Title of Invention	AN AUTOMATIC MACHINE FOR CHASING AND MILLING OF CTC TEA ROLLWERE
Abstract	In the present invention there is provided a machine for chasing and milling operation in combination for sharpening / resharpening of new / used CTC tea rollers. The machine comprises in combination a main frame mounted headstock, tailstock, servo drive assembly, indexer assembly, chaser and milling tool holding attachments, electro-magnetic clutches, brake, power drive arrangements, stepper motor, proximity switches, and electronic control unit having programmable logic controller (PLC). The servo drive assembly, which is a subassembly of the total machine, provides required rotational motion to the job (CTC roller). The same servo drive assembly also provides rotation to the main lead screw for intermittent movement of saddle while chasing and longitudinal motion of the saddle along with the angular indexing of job (CTC roller) in milling operation. The said servo drive assembly, facilitates to provide accurate longitudinal motion to the saddle in required direction i.e. slow advancing movement for chasing, milling operation as well as the non-cutting rapid return of the saddle after completion of particular machining cycle. The single stepper motor provides the movement of saddle for depth of cut during chasing and milling operation. This results in much simplification of the total machine and brings about increased productivity, higher energy efficiency and increased accuracy in machining.

Title of Invention

AN AUTOMATIC MACHINE FOR CHASING AND MILLING OF CTC TEA ROLLWERE

Abstract

In the present invention there is provided a machine for chasing and milling operation in combination for sharpening / resharpening of new / used CTC tea rollers. The machine comprises in combination a main frame mounted headstock, tailstock, servo drive assembly, indexer assembly, chaser and milling tool holding attachments, electro-magnetic clutches, brake, power drive arrangements, stepper motor, proximity switches, and electronic control unit having programmable logic controller (PLC). The servo drive assembly, which is a subassembly of the total machine, provides required rotational motion to the job (CTC roller). The same servo drive assembly also provides rotation to the main lead screw for intermittent movement of saddle while chasing and longitudinal motion of the saddle along with the angular indexing of job (CTC roller) in milling operation. The said servo drive assembly, facilitates to provide accurate longitudinal motion to the saddle in required direction i.e. slow advancing movement for chasing, milling operation as well as the non-cutting rapid return of the saddle after completion of particular machining cycle. The single stepper motor provides the movement of saddle for depth of cut during chasing and milling operation. This results in much simplification of the total machine and brings about increased productivity, higher energy efficiency and increased accuracy in machining.

Full Text	The present invention relates to an automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers. The present invention particularly relates to an automatic machine providing combined facilities for chasing circular grooves and milling helical grooves on the surface of CTC tea rollers. The machine of the present invention will be useful for performing sharpening and resharpening operations, both for chasing and milling in one setup, for manufacturing / reconditioning of CTC tea rollers used in tea industry. The said CTC tea rollers, having annular and helical grooves on the surface, are used in the CTC tea manufacturing machines, wherein a pair of such rollers rotates at different speeds. The withered tea leaf after passing through a number of such pairs of rotating rollers achieve the final size and shape through the process of crushing, tearing and curling (CTC) resulting in CTC tea. The main usage of this invention is to provide a programmable machine with combined facilities for chasing circular grooves and milling helical grooves on the surface of CTC rollers, in one set up. Once the roller is loaded on the machine, appropriate types of chasing and milling tools are used and respective programming sequence is applied to the drive units of the machine. The machine follows the sequence of chasing and milling to complete the machining of the grooves on the surface of the roller. In this machine, according to the design of the helical grooves, the milling cutter can be fitted accurately with respect to the roller. Through search of patent data-bases and market survey, it is found that two different machines are used for sharpening and re-sharpening of CTC rollers one for chasing and another for milling. Since tool positioning and depth of cut are executed manually, accuracy and productivity are entirely dependent on the skill of the operator and varies from individual to individual. However, no automatic combined machine is commercially available for production of CTC tea rollers. In our co-pending Indian patent application no. 0052DEL2002 filed on 25/01/2002, titled "An Universal Machine for Manufacturing and or Reconditioning of Processors like CTC Tea Rollers", we have described and claimed an automatic machine which can undertake both chasing and milling operations. In figure-1 of the drawings accompanying this specification is shown the kinematic arrangement of the said machine, which comprises in combination: four induction motors (lal, la2, lb, Id), three stepper motors (lc, le, If), six electro-magnetic clutches (2a, 2b, 2c, 2d, 2e, 2f), four gear boxes (3a, 3b, 3c, 3d), three encoders (4a, 4b, 4c), a dual clutch (5a) and one brake (6a). Induction motor (Id) is used for providing the drive to the milling cutter, motor (lb) is used for rotation of the roller during chasing, two induction motors (lal &la2) are used for longitudinal slow forward and rapid reverse movement of the tool carriage during milling operation. A dual clutch (5a) has been used along with a gearbox (3a) and belt-pulley drives to obtain both forward and reverse speeds of the tool carriage. One stepper motor (le) has been used for intermittent longitudinal positioning of the carriage during chasing operation. Another stepper motor (If) is used for angular indexing of the roller during helical milling. The other stepper motor (lc) is used for imparting depth of cut to the chasing tool /milling cutter. The herein above described disclosure in our co-pending Indian patent application no. 0052DEL2002 has successfully provided, as per the objectives set forth therein, an automatic machine which can undertake both chasing and milling operations. Although the above said disclosure meets the objectives and provides a combined machine for undertaking both chasing and milling operations, in the kinematic arrangement, as described herein above, there is scope for improvement as follows: 1. This arrangement has altogether seven motors, i.e. three stepper motors and four induction motors and may cause complexity in assembly and lead to alignment problem. 2. There are six electromagnetic clutches and one brake, which may require frequent maintenance problem. 3. This arrangement has five gearboxes i.e. (3a,3b,3c,3d) as described and one headstock gearbox integrated with the basic machine, which will result in high inertia. 4. The system is not energy efficient due to large number of rotating components, resulting in frictional losses. 5. The system does not have any provision for higher cutting speeds suitable for a carbide tool. Based on the prior art details and drawbacks thereof, the problems envisaged are complexity in assembly and misalignment, frequent maintenance, high inertia, high frictional losses. From the hitherto known prior art, as detailed above it is clear that there is a definite need to provide a machine for chasing and milling of CTC tea rollers in a single set-up, which overcomes the above stated problems. The main object of the present invention is to provide an automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, which obviates the drawbacks as detailed above. Another object of the present invention is to provide automation with minimum rotating components. Still another object of the present invention is to provide chasing and milling operations of CTC rollers, in one machine, instead of two machines, as is being done in industry, at present. Yet another object of the present invention is to provide an automated machine for the purpose of chasing and milling of the CTC rollers, through programmable electronic controller, with optimum cutting speed and feed according to the tool material. Still yet another object of the present invention is to provide a low cost automation in chasing and milling operation of CTC tea rollers. A further object of the present invention is to provide an automated machine with minimum maintenance. A still further object of the present invention is to provide an energy efficient system for the purpose of chasing and milling of CTC tea rollers. In the present invention there is provided a machine for chasing and milling operation in combination for sharpening / resharpening of new / used CTC tea rollers. The machine comprises in combination a main frame mounted headstock, tailstock, servo drive assembly, indexer assembly, chaser and milling tool holding attachments, electro-magnetic clutches, brake, power drive arrangements, stepper motor, proximity switches, and electronic control unit having programmable logic controller (PLC). The servo drive assembly, which is a subassembly of the total machine, provides required rotational motion to the job (CTC roller). The same servo drive assembly also provides rotation to the main lead screw for intermittent movement of saddle while chasing and longitudinal motion of the saddle along with the angular indexing of job (CTC roller) in milling operation. The said servo drive assembly, facilitates to provide accurate longitudinal motion to the saddle in required direction i.e. slow advancing movement for chasing, milling operation as well as the non-cutting rapid return of the saddle after completion of particular machining cycle. The single stepper motor provides the movement of saddle for depth of cut during chasing and milling operation. This results in much simplification of the total machine and brings about increased productivity, higher energy efficiency and increased accuracy in machining. The machine of the present invention for chasing and milling of CTC tea rollers and the constituent subsystems are illustrated and described in figures 2 to 5 of the drawings accompanying this specification, which show the schematic and perspective views. In the drawings accompanying this specification, figure-2 represents the schematic view of the machine of the present invention for chasing and milling of CTC Tea Rollers, which consists of servo drive assembly for rotation of CTC roller (4) and main lead screw (5). The servo drive assembly consists of servo motor (la) with electro-magnetic clutch (EMC) (lb) for continuous rotation of roller. EMC (2b) and gear train (7) are used for rotation of main lead screw (5) using servo drive assembly as and when required while performing chasing and milling operation. Brake (le) is used to prevent rotation of lead screw while chasing annular grooves. Stepper drive assembly consists of stepper motor (3a) with EMC (3b) and gearbox (2c) for rotation of cross lead screw (6) to provide movement of cross slide (8). Motor (2a) rotates milling cutter (9) through gearbox (lc) while performing milling operation on the CTC roller. In the figure-3 of the drawings accompanying this specification is shown the perspective view of the machine of the present invention, from operator side. It comprises machine bed (1) on which various subsystems are mounted, main lead screw (2) for providing longitudinal movement to the saddle (3). Indexer assembly (8) is mounted on headstock (9). Headstock (9) provides rotation of the roller (10) through chuck (26), which holds the CTC roller (10) from one end and other end of the roller (10) is hold in tailstock (24). Milling head (7) is used to mount milling cutter (12). Electronic control unit (11) is used for automatic chasing and milling operation as well as for initial set up. In the figure-4 of the drawings accompanying this specification is shown the perspective view of the machine of the present invention, from rear side. It comprises servo motor assembly consisting of servo motor (13) with belt pulley (14) and EMC (15) for rotating the CTC roller (10) through headstock gear box (9). The power is transmitted to main lead screw (2) through indexing assembly (8) (shown in figure 3) and gear train assembly (16) for longitudinal motion of the saddle (3) on which cross slide (4) is attached through cross lead screw (5). The chasing tool holder (6) and milling head (7) (shown in figure 3) are mounted on cross slide (4). Stepper drive assembly consisting of stepper motor (18) with gear box (19) and EMC (20) rotates cross lead screw (5) through timer pulley arrangement (21). Cross lead screw (5) imparts motion to cross slide (4) which slides on saddle (3) to provide depth of cut during chasing and milling operation. Motor (22) rotates milling cutter (12) (shown in figure 3) through gearbox (23) while performing milling operation on the CTC roller (10). The brake (17) is used to prevent rotation of lead screw while cutting annular grooves during chasing operation. In the drawings accompanying this specification, figure-5 shows the schematic view of the servo drive assembly (13,15,14), servo motor (13) with belt pulley (14) and EMC (15) and indexing assembly (8) of the machine of the present invention as shown in figure-3 and figure-4. The indexing assembly (8) comprises of EMC (25), which is engaged whenever it is required to rotate the main lead screw i.e. while indexing to next annular groove or indexing to next helical groove or for milling of helical grooves. When EMC (25) is disengaged, the power does not transmit to lead screw. Automation logic provided by the electronics is such that the chasing operation is followed by milling operation. During chasing operation, the chaser tool holder moves forward to get engaged with the job (CTC roller) by stepper motor up to required depth while the job / roller is continuously rotating at the set speed by servo drive. After machining the annular groove to full depth, the chaser tool holder returns to the cross home position, which is set outside the roller surface. The tool carriage then shifts in the longitudinal direction to the next position for subsequent grooving operation. In this way, the chasing operation for all the grooves will be completed and then the tool carriage returns to the starting home position, which is set at the tailstock end of the machine. For milling operation, the coordinate movement of saddle and roller is required. Servo drive assembly and indexing assembly provides this coordinate movement. While at longitudinal home position, milling tool holder moves forward to get engaged with the job (CTC roller) at a specific depth of cut by stepper motor. Thereafter milling operation is continued where the job is rotating and the milling tool point is traversing slowly along the length of the job by servomotor. After the completion of the milling operation, the tool holder disengages itself from job and returns to the starting position (longitudinal home position) at rapid speed by servomotor. The essential constructional features present in the hitherto known machine of the prior art are: (a) Machine bed (b) Main lead screw (c) Cross lead screw (d) Headstock, clutch and tailstock (e) Saddle (f) Cross slide along with chaser and milling tool holder with tools (g) Gear train assembly (h) Stepper motor along with gearbox and clutch for depth of cut. The essential constructional features of the machine of the present invention are: i) A servo drive with a belt pulley and electro-magnetic clutches (two nos.) to provide rotational motion in chasing and angular indexing in milling. Further, it provides longitudinal motion (intermittent for chasing and continuous for milling) to the cutting tool, ii) A stepper motor with a gear box and electro-magnetic clutch to provide movement of the cross slide lead screw, iii) An electronic controller having programmable logic controller (PLC) for total automation. The novel constructional features of the machine of the present invention, that is constructional features which are not present in the hitherto known machines of the prior art, is the kinematic arrangement wherein with a single servo motor with minimum rotating components it has been possible to achieve all the motions at different speeds required for chasing and milling operations. i. Servo drive assembly, which is a subassembly of the total machine, provides the rotational motion to the job (roller) through clutch, belt pulley arrangement and worm gear assembly, as a constituent of the headstock. ii. Servo drive assembly provides accurate longitudinal motion to the saddle in required direction i.e. slow advancing movement for chasing, milling operation and as well as the non-cutting rapid return of the saddle after completion of particular machining cycle through clutch, belt pulley arrangement, gear train assembly and lead screw, iii. Brake is provided to hold the lead screw while doing the angular precision indexing of roller in milling and cutting of grooves in chasing, through servo motor assembly, iv. Proximity sensors are suitably used and positioned as required to provide information of depth of cut, cross home position, longitudinal home positions at tailstock and headstock ends of job (roller) eliminating the use of encoders. The novelty of the machine of the present invention resides in the kinematic arrangement of the servo motor assembly which ensures the flexibility of the movement of the milling cutter, chaser tool and the roller at different speeds, and feed in different directions and roller indexing at different angles whenever required to ensure maximum productivity. The novelty of the machine of the present invention lies in the kinematic arrangement wherein with a single servo motor, two electro-magnetic clutches and one electro-magnetic brake, it has been possible to achieve at different speeds all the following motions: i) Rotation of the roller while chasing operation, ii) Indexing of the roller in milling iii) Rotation of the roller for helical milling iv) Longitudinal indexing of the chaser in chasing v) Longitudinal motion of the milling cutter for helical milling vi) Rapid return movement in longitudinal direction of chaser and milling cutter. The non-obvious inventive step in the machine of the present invention resides in providing in combination the kinematic arrangement of the servo motor assembly, wherein with a single servo motor, two electro-magnetic clutches and one electro-magnetic brake, it is capable to offer the flexibility in movement of the milling cutter, chaser tool and the roller at different speeds in different directions, whenever required, to reduce the idle period in the non-cutting process. The results achieved due to inventive steps defined above are simpler assembly, high productivity, better accuracy and minimum maintenance. Accordingly the present invention provides an automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, which comprises: in combination a main frame mounted headstock (9) having chuck (26) and tailstock (24), capable of holding a job/roller (10) to be machined, characterized in that the said headstock (9) being provided with a servo drive unit (13, 14, 15), wherein servo motor (13) is connected by means such as a belt pulley (14) and an electromagnetic clutch (15) to the said chuck (26) and also to the main lead screw (2) via a gear train (16) and an electro-magnetic clutch (25) capable of driving a horizontally placed saddle (3) having a cross lead screw (5) capable of driving a movable cross slide (4) provided with a milling head (7) and a chasing/cutting tool holder (6) placed diametrically with respect to the said job/roller (10) to be machined; the said headstock (9) being provided with an auto-indexing attachment (8) capable of indexing the job/roller (10) after each helical and annular groove. In an embodiment of the present invention, the chuck (26) and main lead screw (2) with indexing attachment (8) is coupled through a gear train assembly (16), belt pulley arrangement (14), electro-magnetic clutches (25,15) to the servo motor (13). In another embodiment of the present invention, the servo drive (13) is capable to rotate the job (10) for both chasing and milling operations. In yet another embodiment of the present invention, the servo drive unit (13,14,15) is essentially capable of providing slow longitudinal motion to the milling head (7) or chaser tool (6) during milling or chasing operation, respectively and rapid longitudinal return to the starting point in the non-cutting phase. In still another embodiment of the present invention, the milling tool /chaser tool crosswise positioning attachment, which consists of a stepper motor (18) coupled to a speed reducer gear box (19) and an electro-magnetic clutch (20), is essentially capable of providing incremental positioning at the required pitch to the milling tool/chaser tool (7 & 6) through the cross lead screw (5). In still yet another embodiment of the present invention, the cross lead screw (5) is coupled with a speed reducer gear box (19) and a stepper motor (18) along with clutch (20) in such a manner as to enable both chasing and milling operations using proximity switches as cross-home and cross-end position. In a further embodiment of the present invention, the milling head (7) is provided with a precise tilting arrangement consisting of an inbuilt micrometer arrangement consisting of worm wheel and vernier scale. In a still further embodiment of the present invention, there is provided an electronic control mechanism (11) which consists of a programmable logic controller coupled with stepper motor (18), servo motor (13), electromagnetic clutches (20, 15, 25), brake (17) and proximity switches, in such a manner as to be capable of providing programmed control to the main lead screw (2), cross lead screw (5), job (10) and auto-indexing attachment (8). In a yet further embodiment of the present invention, the characteristics of machining operations capabilities of the machine on job/roller are: (i) fully automatic chasing of annular groves; (ii) fully automatic milling of helical grooves; and (iii)turning operation on the roller with manual longitudinal feed of tool. In another embodiment of the present invention, the machine is capable of accommodating a job/roller of size in the range of: (a) total length of roller: 700 mm to 1600 mm; (b) diameter of roller : 150 mm to 325 mm; (c) maximum machinable length on roller : 1400 mm. In still another embodiment of the present invention, the pitch accuracy of the machine for annular chasing of grooves is of the order of 500 to 600 microns. The complete description of the automatic machine, of the present invention, for chasing and milling of CTC (crushing, tearing and curling) tea rollers is as follows: The three dimensional views of the machine which are shown in figures 3 & 4 of the drawings comprise of headstock (9), chuck (26) and tailstock (24) for holding the job (CTC roller) (10) to be machined. Milling head attachment (7) holds the milling cutter (12). This milling head (7) along with the milling cutter (12) is capable of tilting to the required angle by means of the inbuilt micrometer arrangement. For cutting circumferential groove on the cylindrical job (CTC roller) (10), the chaser tool is attached to the chaser tool holder (6). Servo motor coupled with a speed reducer belt pulley arrangement, gear train, an electro-magnetic clutch and brake, facilitates the incremental longitudinal positioning of the chaser tool at the required pitch for machining circumferential grooves on the job. During milling operation, the servo motor (13) is used to achieve different speeds of rotation of the main lead screw (2) to move the saddle (3) in both forward and reverse directions through servo drive unit (13,14,15), clutch (25) and gear train (16). While in milling phase, the saddle (3), travels with slow speed along the axis of the job with the milling cutter engaged. After the completion of one longitudinal travel, the milling cutter gets disengaged from the job and returns to the starting position (longitudinal home position) with rapid speed. Also the same servo system is used for angular indexing of roller i.e. rotating the roller by required angle for machining of the next milling groove. The servo drive assembly thus contributes to the automation of the machine by using minimum number of components and constructional simplicity. The chaser tool holder (6) is mounted on the front side of the cross slide (4) where as milling head (7) is mounted on the rear side. The cross lead screw (5) is coupled with a stepper motor (18) and a speed reducer gear box (19) for both chasing and milling operation. During chasing operation, the cross slide (4) will move gradually towards the job (roller) (10) and engage the cutting tool in the cutting operation, through specified depth of cut (using proximity switch to provide information of depth of cut). Once the cutting operation is completed, the cross slide (4) with the cutting tool (6) will retract to its initial position of disengagement (cross-home position). For milling operation, the cross slide (4) which also accommodates the milling head (7) at the backside of the machine, is set at a position as per required depth of cut (using proximity switches for depth of cut information) by giving only required incremental rotation by the stepper motor (18) which drives the cross lead screw (5). The forward (comparatively slow) and return (comparatively fast) movements of the cross slide (4) are synchronized using the signals from proximity switches (not shown in the drawings) situated at appropriate locations, as inputs to the programmable logic controller (PLC) located at Electronic console for automation (11). For chasing operation chuck (26) (which holds one end of the job to be machined and imparts rotation to it) is directly driven by the servo motor (13) through clutch (15), belt pulley arrangement (14) and worm gear assembly, as a constituent of the headstock (9). For milling operation, chuck (26) receives power from the same servo motor (13). The power propagation route from servo motor (13) to main lead screw is through belt pulley (17), electromagnetic clutches (18) & (19) and gear train (11). The machine can be used for chasing and milling of CTC tea rollers, chasing operation being followed by milling operation. Thus with single loading of the job, a cylindrical used roller or a new roller can be re-sharpened or sharpened in an automatic process, with the help of programmable logic controller (PLC). Moreover, this machine can be used either in auto mode or in manual mode, in the event of any problem with the PLC facility. The novelty of the machine of present invention resides in providing the desired output i.e. chasing and milling of CTC Tea Rollers with greater accuracy in single setup. The non-obvious inventive step in the machine of the present invention resides in providing in combination the kinematic arrangement of the servo motor assembly, which is capable to offer the flexibility in movement of the milling cutter, chaser tool and the roller at different speeds in different directions, whenever required, to reduce the idle period in the cutting process. This is not like any existing device used for similar purpose available in the public domain. A prototype machine of the present invention as herein above described for chasing and milling of CTC (crushing, tearing and curling) tea rollers was fabricated. The characteristics of the said prototype machine of the present invention for machining operations and job specifications were as follows: The machine was capable of performing the following operations on job (roller): 1. Fully automatic chasing of annular groves. 2. Fully automatic milling of helical grooves. 3. Turning operation on the roller with manual longitudinal feed of tool. The machine was capable of accommodating a job (roller) of size in the range of: a. Total length of roller: 700 mm to 1600 mm. b. Diameter of roller: 150 mm to 325 mm. c. Maximum machinable length on roller: 1400 mm. The following examples are given by way of illustrations of the machine of the present invention for chasing and milling of CTC tea rollers in actual practice and should not be construed to limit the scope of the present invention. The roller used in the following examples has the specifications as given below: CTC tea roller specifications : Roller material : stainless steel Roller diameter : 215.9 MM (8.5inch), Machinable length of roller : 914.4MM (36 inch), No of chasing grooves : 288 Pitch of circumferential grooves : 3.0625MM (8 Tooth per inch) No of Helical grooves on circumference : 50 present invention for (a) chasing and (b) milling are as follows: (a). Examples of Chasing of annular grooves: The following experiments were for chasing operation of the annular grooves as per the specifications of Whitworth's thread, for 8 TPI, 55° profile with root radius r = 0.8 mm (as U Type) and with root radius r = 0.4 mm (as V Type). The longitudinal movement to the saddle was imparted by servo motor through indexing unit and main lead screw as discussed in the description of the machine. The depth of cut for chasing tool was imparted by driving the cross lead screw with a stepper motor. Table-1, given below, shows the different parameters set during chasing operation for annular grooves where columns represent three experimental trials, namely: Example-1, Example-2 and Example-3, respectively and rows shows the variables set during trial. Table-1 (Table Removed) The function of the machine was found satisfactory and the machine was able to perform the chasing operation on the CTC tea roller made of stainless steel material. The cumulative pitch error was measured over the length of the roller [on 914.4 mm (on 36 inch length)] for above trials and it was found to be of the order of 500 to 600 microns. The depth of the chasing grooves was also found to be uniform all over. It is observed that the pitch accuracy for the annular chasing grooves achieved by the machine of the present invention is of the order of 500 to 600 microns, which is much better than the accuracy of the CTC tea rollers sharpened on the existing conventional machine tools, which is of the order of 2mm (2000 Microns). (b). Examples of milling helical grooves: The longitudinal feed to the saddle was imparted by servo motor in accordance with the roller RPM to machine helical grooves on roller as discussed in the description of the machine. The depth of cut of milling cutter was imparted by driving the cross lead screw with a stepper motor. The parameters for milling of helical grooves set for trials were: Tool material : HSS Grade M-15 Milling tool specifications : OD-0 75mm, 16 mm wide, 0 32 mm bore, 70 degree one side angle, 24 teeth, Left hand. RPM of milling cutter : 144 RPM No of helical grooves : 50 numbers on circumference. Depth of cut : 1.98 mm (full depth). Table-2, given below, shows the different variable parameters set during milling operation of helical grooves where columns represent three experimental trials, namely: Example-4 and Example-5, respectively and rows shows the variables set during trial. Table-2 (Table Removed) The function of the machine was found satisfactory and the machine was able to perform the milling operation on the CTC tea roller made of stainless steel material. The spacing of the grooves over the roller circumference and the milling depth of the milled helical grooves for above trials was found to be uniform. Thus, it is obvious that the rollers manufactured / re-sharpened on the machine of the present invention will be of much greater accuracy and thereby result in production of properly matched pair of CTC or special purpose rollers. While in experimentation with the experimental model, involvement of the human-operator was much reduced due to the inbuilt automation of the process. Now, in one loading and programming through PLC, the process of the metal removal has become efficiently automated. The main advantages of the present invention are: 1. Increased productivity. 2. More energy efficient. 3. Increased accuracy in machining is envisaged due to use of servo motor. 4. The servo drive assembly provides flexibility to the combined machine such that the milling cutter / chaser tool can return with faster speed to the starting position after completing the metal removal operation at slower speed and same movement can be repeated till the job is over. 5. The same servo drive unit also makes the job to rotate in milling / chasing operation. 6. Provides higher speed of roller rotation. 7. Minimum rotating components make the assembly simple. 8. Reduction in alignment complexity. 9. Minimum maintenance problem is envisaged due to less number of rotating components, such as motors, gears and electromagnetic clutches. We claim: 1. An automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, which comprises: in combination a main frame mounted headstock (9) having chuck (26) and tailstock (24), capable of holding a job/roller (10) to be machined, characterized in that the said headstock (9) being provided with a servo drive unit (13, 14, 15), wherein servo motor (13) is connected by means such as a belt pulley (14) and an electro-magnetic clutch (15) to the said chuck (26) and also to the main lead screw (2) via a gear train (16) and an electro-magnetic clutch (25) capable of driving a horizontally placed saddle (3) having a cross lead screw (5) capable of driving a movable cross slide (4) provided with a milling head (7) and a chasing/cutting tool holder (6) placed diametrically with respect to the said job/roller (10) to be machined; the said headstock (9) being provided with an auto-indexing attachment (8) capable of indexing the job/roller (10) after each helical and annular groove. 2. An automatic machine for chasing and milling as claimed in claim 1, wherein the chuck (26) and main lead screw (2) with indexing attachment (8) is coupled through a gear train assembly (16), belt pulley arrangement (14), electromagnetic clutches (25,15) to the servo motor (13). 3. An automatic machine for chasing and milling as claimed in claim 1-2, wherein the servo drive (13) is capable to rotate the job (10) for both chasing and milling operations. 4. An automatic machine for chasing and milling as claimed in claim 1-3, wherein the servo drive unit (13,14,15) is essentially capable of providing slow longitudinal motion to the milling head (7) or chaser tool (6) during milling or chasing operation, respectively and rapid longitudinal return to the starting point in the non-cutting phase. 5. An automatic machine for chasing and milling as claimed in claim 1-4, wherein the milling tool /chaser tool crosswise positioning attachment, which consists of a stepper motor (18) coupled to a speed reducer gear box (19) and an electro-magnetic clutch (20), is essentially capable of providing incremental positioning at the required pitch to the milling tool/chaser tool (7 & 6) through the cross lead screw (5). 6. An automatic machine for chasing and milling as claimed in claim 1-5, wherein the cross lead screw (5) is coupled with a speed reducer gear box (19) and a stepper motor (18) along with clutch (20) in such a manner as to enable both chasing and milling operations using proximity switches as cross-home and cross-end position. 7. An automatic machine for chasing and milling as claimed in claim 1-6, wherein the milling head (7) is provided with a precise tilting arrangement consisting of an inbuilt micrometer arrangement consisting of worm wheel and vernier scale. 8. An automatic machine for chasing and milling as claimed in claim 1-7, wherein is provided an electronic control mechanism (11) which consists of a programmable logic controller coupled with stepper motor (18), servo motor (13), electromagnetic clutches (20, 15, 25), brake (17) and proximity switches, in such a manner as to be capable of providing programmed control to the main lead screw (2), cross lead screw (5), job (10) and auto-indexing attachment (8). 9. An automatic machine for chasing and milling as claimed in claim 1-8, wherein the characteristics of machining operations capabilities of the machine on job/roller are: (iv)fully automatic chasing of annular groves; (v) fully automatic milling of helical grooves; and (vi)turning operation on the roller with manual longitudinal feed of tool. 10. An automatic machine for chasing and milling as claimed in claim 1-9, wherein the machine is capable of accommodating a job/roller of size in the range of: (a) total length of roller: 700 mm to 1600 mm; (b) diameter of roller : 150 mm to 325 mm; (c) maximum machinable length on roller: 1400 mm. 11. An automatic machine for chasing and milling as claimed in claim 1-10, wherein the pitch accuracy of the machine for annular chasing of grooves is of the order of 500 to 600 microns. 12. An automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, substantially as herein described with reference to the examples and figures 2 to 5 of the drawings accompanying this specification. Intellectual Property Management Division Council of Scientific and Industrial Research

Full Text

The present invention relates to an automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers. The present invention particularly relates to an automatic machine providing combined facilities for chasing circular grooves and milling helical grooves on the surface of CTC tea rollers.
The machine of the present invention will be useful for performing sharpening and resharpening operations, both for chasing and milling in one setup, for manufacturing / reconditioning of CTC tea rollers used in tea industry. The said CTC tea rollers, having annular and helical grooves on the surface, are used in the CTC tea manufacturing machines, wherein a pair of such rollers rotates at different speeds. The withered tea leaf after passing through a number of such pairs of rotating rollers achieve the final size and shape through the process of crushing, tearing and curling (CTC) resulting in CTC tea.
The main usage of this invention is to provide a programmable machine with combined facilities for chasing circular grooves and milling helical grooves on the surface of CTC rollers, in one set up. Once the roller is loaded on the machine, appropriate types of chasing and milling tools are used and respective programming sequence is applied to the drive units of the machine. The machine follows the sequence of chasing and milling to complete the machining of the grooves on the surface of the roller. In this machine, according to the design of the helical grooves, the milling cutter can be fitted accurately with respect to the roller.
Through search of patent data-bases and market survey, it is found that two different machines are used for sharpening and re-sharpening of CTC rollers one for chasing and another for milling. Since tool positioning and depth of cut are executed manually, accuracy and productivity are entirely dependent on the skill of the operator and varies from individual to individual. However, no automatic combined machine is commercially available for production of CTC tea rollers.
In our co-pending Indian patent application no. 0052DEL2002 filed on 25/01/2002, titled "An Universal Machine for Manufacturing and or Reconditioning of Processors like CTC Tea Rollers", we have described and claimed an automatic machine which can undertake both chasing and milling operations. In figure-1 of the drawings accompanying this specification is shown the kinematic arrangement of the said machine, which comprises in combination: four induction motors (lal, la2, lb, Id), three stepper motors (lc, le, If), six electro-magnetic clutches (2a, 2b, 2c, 2d, 2e, 2f), four gear boxes (3a, 3b, 3c, 3d), three encoders (4a, 4b, 4c), a dual clutch (5a) and one brake (6a). Induction motor (Id) is used for providing the drive to the milling cutter, motor (lb) is used for rotation of the roller during chasing, two induction motors (lal &la2) are used for longitudinal slow forward and rapid reverse movement of the tool carriage during milling operation. A dual clutch (5a) has been used along with a gearbox (3a) and belt-pulley drives to obtain both forward and reverse speeds of the tool carriage. One stepper motor (le) has been used for intermittent longitudinal positioning of the carriage during chasing operation. Another stepper motor (If) is used for angular indexing of the roller during helical milling. The other stepper motor (lc) is used for imparting depth of cut to the chasing tool /milling cutter.
The herein above described disclosure in our co-pending Indian patent application no. 0052DEL2002 has successfully provided, as per the objectives set forth therein, an automatic machine which can undertake both chasing and milling operations. Although the above said disclosure meets the objectives and provides a combined machine for undertaking both chasing and milling operations, in the kinematic arrangement, as described herein above, there is scope for improvement as follows:
1. This arrangement has altogether seven motors, i.e. three stepper motors and four induction motors and may cause complexity in assembly and lead to alignment problem.
2. There are six electromagnetic clutches and one brake, which may require frequent maintenance problem.
3. This arrangement has five gearboxes i.e. (3a,3b,3c,3d) as described and one headstock gearbox integrated with the basic machine, which will result in high inertia.
4. The system is not energy efficient due to large number of rotating components, resulting in frictional losses.
5. The system does not have any provision for higher cutting speeds suitable for a carbide tool.
Based on the prior art details and drawbacks thereof, the problems envisaged are complexity in assembly and misalignment, frequent maintenance, high inertia, high frictional losses. From the hitherto known prior art, as detailed above it is clear that there is a definite need to provide a machine for chasing and milling of CTC tea rollers in a single set-up, which overcomes the above stated problems.
The main object of the present invention is to provide an automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, which obviates the drawbacks as detailed above.
Another object of the present invention is to provide automation with minimum rotating components.
Still another object of the present invention is to provide chasing and milling operations of CTC rollers, in one machine, instead of two machines, as is being done in industry, at present.
Yet another object of the present invention is to provide an automated machine for the purpose of chasing and milling of the CTC rollers, through programmable electronic controller, with optimum cutting speed and feed according to the tool material.
Still yet another object of the present invention is to provide a low cost automation in chasing and milling operation of CTC tea rollers.
A further object of the present invention is to provide an automated machine with minimum maintenance.
A still further object of the present invention is to provide an energy efficient system for the purpose of chasing and milling of CTC tea rollers.
In the present invention there is provided a machine for chasing and milling operation in combination for sharpening / resharpening of new / used CTC tea rollers. The machine comprises in combination a main frame mounted headstock, tailstock, servo drive assembly, indexer assembly, chaser and milling tool holding attachments, electro-magnetic clutches, brake, power drive arrangements, stepper motor, proximity switches, and electronic control unit having programmable logic controller (PLC). The servo drive assembly, which is a subassembly of the total machine, provides required rotational motion to the job (CTC roller). The same servo drive assembly also provides rotation to the main lead screw for intermittent movement of saddle while chasing and longitudinal motion of the saddle along with the angular indexing of job (CTC roller) in milling operation. The said servo drive assembly, facilitates to provide accurate longitudinal motion to the saddle in required direction i.e. slow advancing movement for chasing, milling operation as well as the non-cutting rapid return of the saddle after completion of particular machining cycle. The single stepper motor provides the movement of saddle for depth of cut during chasing and milling operation. This results in much simplification of the total machine and brings about increased productivity, higher energy efficiency and increased accuracy in machining.
The machine of the present invention for chasing and milling of CTC tea rollers and the constituent subsystems are illustrated and described in figures 2 to 5 of
the drawings accompanying this specification, which show the schematic and perspective views.
In the drawings accompanying this specification, figure-2 represents the schematic view of the machine of the present invention for chasing and milling of CTC Tea Rollers, which consists of servo drive assembly for rotation of CTC roller (4) and main lead screw (5). The servo drive assembly consists of servo motor (la) with electro-magnetic clutch (EMC) (lb) for continuous rotation of roller. EMC (2b) and gear train (7) are used for rotation of main lead screw (5) using servo drive assembly as and when required while performing chasing and milling operation. Brake (le) is used to prevent rotation of lead screw while chasing annular grooves. Stepper drive assembly consists of stepper motor (3a) with EMC (3b) and gearbox (2c) for rotation of cross lead screw (6) to provide movement of cross slide (8). Motor (2a) rotates milling cutter (9) through gearbox (lc) while performing milling operation on the CTC roller.
In the figure-3 of the drawings accompanying this specification is shown the perspective view of the machine of the present invention, from operator side. It comprises machine bed (1) on which various subsystems are mounted, main lead screw (2) for providing longitudinal movement to the saddle (3). Indexer assembly (8) is mounted on headstock (9). Headstock (9) provides rotation of the roller (10) through chuck (26), which holds the CTC roller (10) from one end and other end of the roller (10) is hold in tailstock (24). Milling head (7) is used to mount milling cutter (12). Electronic control unit (11) is used for automatic chasing and milling operation as well as for initial set up.
In the figure-4 of the drawings accompanying this specification is shown the perspective view of the machine of the present invention, from rear side. It comprises servo motor assembly consisting of servo motor (13) with belt pulley (14) and EMC (15) for rotating the CTC roller (10) through headstock gear box (9). The power is transmitted to main lead screw (2) through indexing assembly
(8) (shown in figure 3) and gear train assembly (16) for longitudinal motion of the saddle (3) on which cross slide (4) is attached through cross lead screw (5). The chasing tool holder (6) and milling head (7) (shown in figure 3) are mounted on cross slide (4). Stepper drive assembly consisting of stepper motor (18) with gear box (19) and EMC (20) rotates cross lead screw (5) through timer pulley arrangement (21). Cross lead screw (5) imparts motion to cross slide (4) which slides on saddle (3) to provide depth of cut during chasing and milling operation. Motor (22) rotates milling cutter (12) (shown in figure 3) through gearbox (23) while performing milling operation on the CTC roller (10). The brake (17) is used to prevent rotation of lead screw while cutting annular grooves during chasing operation.
In the drawings accompanying this specification, figure-5 shows the schematic view of the servo drive assembly (13,15,14), servo motor (13) with belt pulley (14) and EMC (15) and indexing assembly (8) of the machine of the present invention as shown in figure-3 and figure-4. The indexing assembly (8) comprises of EMC (25), which is engaged whenever it is required to rotate the main lead screw i.e. while indexing to next annular groove or indexing to next helical groove or for milling of helical grooves. When EMC (25) is disengaged, the power does not transmit to lead screw.
Automation logic provided by the electronics is such that the chasing operation is followed by milling operation. During chasing operation, the chaser tool holder moves forward to get engaged with the job (CTC roller) by stepper motor up to required depth while the job / roller is continuously rotating at the set speed by servo drive. After machining the annular groove to full depth, the chaser tool holder returns to the cross home position, which is set outside the roller surface. The tool carriage then shifts in the longitudinal direction to the next position for subsequent grooving operation. In this way, the chasing operation for all the grooves will be completed and then the tool carriage returns to the starting home position, which is set at the tailstock end of the machine. For milling operation,
the coordinate movement of saddle and roller is required. Servo drive assembly and indexing assembly provides this coordinate movement. While at longitudinal home position, milling tool holder moves forward to get engaged with the job (CTC roller) at a specific depth of cut by stepper motor. Thereafter milling operation is continued where the job is rotating and the milling tool point is traversing slowly along the length of the job by servomotor. After the completion of the milling operation, the tool holder disengages itself from job and returns to the starting position (longitudinal home position) at rapid speed by servomotor.
The essential constructional features present in the hitherto known machine of the prior art are:
(a) Machine bed
(b) Main lead screw
(c) Cross lead screw
(d) Headstock, clutch and tailstock
(e) Saddle
(f) Cross slide along with chaser and milling tool holder with tools
(g) Gear train assembly
(h) Stepper motor along with gearbox and clutch for depth of cut.
The essential constructional features of the machine of the present invention are: i) A servo drive with a belt pulley and electro-magnetic clutches (two nos.) to provide rotational motion in chasing and angular indexing in milling. Further, it provides longitudinal motion (intermittent for chasing and continuous for milling) to the cutting tool, ii) A stepper motor with a gear box and electro-magnetic clutch to
provide movement of the cross slide lead screw, iii) An electronic controller having programmable logic controller (PLC) for total automation.
The novel constructional features of the machine of the present invention, that is constructional features which are not present in the hitherto known machines of the prior art, is the kinematic arrangement wherein with a single servo motor with minimum rotating components it has been possible to achieve all the motions at different speeds required for chasing and milling operations.
i. Servo drive assembly, which is a subassembly of the total
machine, provides the rotational motion to the job (roller) through clutch, belt pulley arrangement and worm gear assembly, as a constituent of the headstock. ii. Servo drive assembly provides accurate longitudinal motion to the saddle in required direction i.e. slow advancing movement for chasing, milling operation and as well as the non-cutting rapid return of the saddle after completion of particular machining cycle through clutch, belt pulley arrangement, gear train assembly and lead screw, iii. Brake is provided to hold the lead screw while doing the angular precision indexing of roller in milling and cutting of grooves in chasing, through servo motor assembly, iv. Proximity sensors are suitably used and positioned as required to provide information of depth of cut, cross home position, longitudinal home positions at tailstock and headstock ends of job (roller) eliminating the use of encoders.
The novelty of the machine of the present invention resides in the kinematic arrangement of the servo motor assembly which ensures the flexibility of the movement of the milling cutter, chaser tool and the roller at different speeds, and feed in different directions and roller indexing at different angles whenever required to ensure maximum productivity.
The novelty of the machine of the present invention lies in the kinematic arrangement wherein with a single servo motor, two electro-magnetic clutches
and one electro-magnetic brake, it has been possible to achieve at different speeds
all the following motions:
i) Rotation of the roller while chasing operation, ii) Indexing of the roller in milling iii) Rotation of the roller for helical milling iv) Longitudinal indexing of the chaser in chasing v) Longitudinal motion of the milling cutter for helical milling vi) Rapid return movement in longitudinal direction of chaser and milling cutter.
The non-obvious inventive step in the machine of the present invention resides in providing in combination the kinematic arrangement of the servo motor assembly, wherein with a single servo motor, two electro-magnetic clutches and one electro-magnetic brake, it is capable to offer the flexibility in movement of the milling cutter, chaser tool and the roller at different speeds in different directions, whenever required, to reduce the idle period in the non-cutting process. The results achieved due to inventive steps defined above are simpler assembly, high productivity, better accuracy and minimum maintenance.
Accordingly the present invention provides an automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, which comprises: in combination a main frame mounted headstock (9) having chuck (26) and tailstock (24), capable of holding a job/roller (10) to be machined, characterized in that the said headstock (9) being provided with a servo drive unit (13, 14, 15), wherein servo motor (13) is connected by means such as a belt pulley (14) and an electromagnetic clutch (15) to the said chuck (26) and also to the main lead screw (2) via a gear train (16) and an electro-magnetic clutch (25) capable of driving a horizontally placed saddle (3) having a cross lead screw (5) capable of driving a movable cross slide (4) provided with a milling head (7) and a chasing/cutting tool holder (6) placed diametrically with respect to the said job/roller (10) to be machined; the said headstock (9) being provided with an auto-indexing
attachment (8) capable of indexing the job/roller (10) after each helical and annular groove.
In an embodiment of the present invention, the chuck (26) and main lead screw (2) with indexing attachment (8) is coupled through a gear train assembly (16), belt pulley arrangement (14), electro-magnetic clutches (25,15) to the servo motor (13).
In another embodiment of the present invention, the servo drive (13) is capable to rotate the job (10) for both chasing and milling operations.
In yet another embodiment of the present invention, the servo drive unit (13,14,15) is essentially capable of providing slow longitudinal motion to the milling head (7) or chaser tool (6) during milling or chasing operation, respectively and rapid longitudinal return to the starting point in the non-cutting phase.
In still another embodiment of the present invention, the milling tool /chaser tool crosswise positioning attachment, which consists of a stepper motor (18) coupled to a speed reducer gear box (19) and an electro-magnetic clutch (20), is essentially capable of providing incremental positioning at the required pitch to the milling tool/chaser tool (7 & 6) through the cross lead screw (5).
In still yet another embodiment of the present invention, the cross lead screw (5) is coupled with a speed reducer gear box (19) and a stepper motor (18) along with clutch (20) in such a manner as to enable both chasing and milling operations using proximity switches as cross-home and cross-end position.
In a further embodiment of the present invention, the milling head (7) is provided with a precise tilting arrangement consisting of an inbuilt micrometer arrangement consisting of worm wheel and vernier scale.
In a still further embodiment of the present invention, there is provided an electronic control mechanism (11) which consists of a programmable logic controller coupled with stepper motor (18), servo motor (13), electromagnetic clutches (20, 15, 25), brake (17) and proximity switches, in such a manner as to be capable of providing programmed control to the main lead screw (2), cross lead screw (5), job (10) and auto-indexing attachment (8).
In a yet further embodiment of the present invention, the characteristics of machining operations capabilities of the machine on job/roller are: (i) fully automatic chasing of annular groves; (ii) fully automatic milling of helical grooves; and (iii)turning operation on the roller with manual longitudinal feed of tool.
In another embodiment of the present invention, the machine is capable of accommodating a job/roller of size in the range of:
(a) total length of roller: 700 mm to 1600 mm;
(b) diameter of roller : 150 mm to 325 mm;
(c) maximum machinable length on roller : 1400 mm.
In still another embodiment of the present invention, the pitch accuracy of the machine for annular chasing of grooves is of the order of 500 to 600 microns.
The complete description of the automatic machine, of the present invention, for chasing and milling of CTC (crushing, tearing and curling) tea rollers is as follows:
The three dimensional views of the machine which are shown in figures 3 & 4 of the drawings comprise of headstock (9), chuck (26) and tailstock (24) for holding the job (CTC roller) (10) to be machined. Milling head attachment (7) holds the milling cutter (12). This milling head (7) along with the milling cutter (12) is
capable of tilting to the required angle by means of the inbuilt micrometer arrangement.
For cutting circumferential groove on the cylindrical job (CTC roller) (10), the chaser tool is attached to the chaser tool holder (6). Servo motor coupled with a speed reducer belt pulley arrangement, gear train, an electro-magnetic clutch and brake, facilitates the incremental longitudinal positioning of the chaser tool at the required pitch for machining circumferential grooves on the job. During milling operation, the servo motor (13) is used to achieve different speeds of rotation of the main lead screw (2) to move the saddle (3) in both forward and reverse directions through servo drive unit (13,14,15), clutch (25) and gear train (16). While in milling phase, the saddle (3), travels with slow speed along the axis of the job with the milling cutter engaged. After the completion of one longitudinal travel, the milling cutter gets disengaged from the job and returns to the starting position (longitudinal home position) with rapid speed. Also the same servo system is used for angular indexing of roller i.e. rotating the roller by required angle for machining of the next milling groove.
The servo drive assembly thus contributes to the automation of the machine by using minimum number of components and constructional simplicity.
The chaser tool holder (6) is mounted on the front side of the cross slide (4) where as milling head (7) is mounted on the rear side. The cross lead screw (5) is coupled with a stepper motor (18) and a speed reducer gear box (19) for both chasing and milling operation. During chasing operation, the cross slide (4) will move gradually towards the job (roller) (10) and engage the cutting tool in the cutting operation, through specified depth of cut (using proximity switch to provide information of depth of cut). Once the cutting operation is completed, the cross slide (4) with the cutting tool (6) will retract to its initial position of disengagement (cross-home position).
For milling operation, the cross slide (4) which also accommodates the milling head (7) at the backside of the machine, is set at a position as per required depth of cut (using proximity switches for depth of cut information) by giving only required incremental rotation by the stepper motor (18) which drives the cross lead screw (5). The forward (comparatively slow) and return (comparatively fast) movements of the cross slide (4) are synchronized using the signals from proximity switches (not shown in the drawings) situated at appropriate locations, as inputs to the programmable logic controller (PLC) located at Electronic console for automation (11).
For chasing operation chuck (26) (which holds one end of the job to be machined and imparts rotation to it) is directly driven by the servo motor (13) through clutch (15), belt pulley arrangement (14) and worm gear assembly, as a constituent of the headstock (9).
For milling operation, chuck (26) receives power from the same servo motor (13). The power propagation route from servo motor (13) to main lead screw is through belt pulley (17), electromagnetic clutches (18) & (19) and gear train (11).
The machine can be used for chasing and milling of CTC tea rollers, chasing operation being followed by milling operation. Thus with single loading of the job, a cylindrical used roller or a new roller can be re-sharpened or sharpened in an automatic process, with the help of programmable logic controller (PLC). Moreover, this machine can be used either in auto mode or in manual mode, in the event of any problem with the PLC facility.
The novelty of the machine of present invention resides in providing the desired output i.e. chasing and milling of CTC Tea Rollers with greater accuracy in single setup. The non-obvious inventive step in the machine of the present invention resides in providing in combination the kinematic arrangement of the servo motor assembly, which is capable to offer the flexibility in movement of
the milling cutter, chaser tool and the roller at different speeds in different directions, whenever required, to reduce the idle period in the cutting process. This is not like any existing device used for similar purpose available in the public domain.
A prototype machine of the present invention as herein above described for chasing and milling of CTC (crushing, tearing and curling) tea rollers was fabricated. The characteristics of the said prototype machine of the present invention for machining operations and job specifications were as follows: The machine was capable of performing the following operations on job (roller):
1. Fully automatic chasing of annular groves.
2. Fully automatic milling of helical grooves.
3. Turning operation on the roller with manual longitudinal feed of tool.
The machine was capable of accommodating a job (roller) of size in the range of:
a. Total length of roller: 700 mm to 1600 mm.
b. Diameter of roller: 150 mm to 325 mm.
c. Maximum machinable length on roller: 1400 mm.
The following examples are given by way of illustrations of the machine of the present invention for chasing and milling of CTC tea rollers in actual practice and should not be construed to limit the scope of the present invention.
The roller used in the following examples has the specifications as given below: CTC tea roller specifications :
Roller material : stainless steel
Roller diameter : 215.9 MM (8.5inch),
Machinable length of roller : 914.4MM (36 inch),
No of chasing grooves : 288
Pitch of circumferential grooves : 3.0625MM (8 Tooth per inch)
No of Helical grooves on circumference : 50
present invention for (a) chasing and (b) milling are as follows:
(a). Examples of Chasing of annular grooves:
The following experiments were for chasing operation of the annular grooves as per the specifications of Whitworth's thread, for 8 TPI, 55° profile with root radius r = 0.8 mm (as U Type) and with root radius r = 0.4 mm (as V Type). The longitudinal movement to the saddle was imparted by servo motor through indexing unit and main lead screw as discussed in the description of the machine. The depth of cut for chasing tool was imparted by driving the cross lead screw with a stepper motor.
Table-1, given below, shows the different parameters set during chasing operation for annular grooves where columns represent three experimental trials, namely: Example-1, Example-2 and Example-3, respectively and rows shows the variables set during trial.
Table-1

(Table Removed)
The function of the machine was found satisfactory and the machine was able to perform the chasing operation on the CTC tea roller made of stainless steel material. The cumulative pitch error was measured over the length of the roller [on 914.4 mm (on 36 inch length)] for above trials and it was found to be of the
order of 500 to 600 microns. The depth of the chasing grooves was also found to be uniform all over.
It is observed that the pitch accuracy for the annular chasing grooves achieved by the machine of the present invention is of the order of 500 to 600 microns, which is much better than the accuracy of the CTC tea rollers sharpened on the existing conventional machine tools, which is of the order of 2mm (2000 Microns).
(b). Examples of milling helical grooves:
The longitudinal feed to the saddle was imparted by servo motor in accordance
with the roller RPM to machine helical grooves on roller as discussed in the
description of the machine. The depth of cut of milling cutter was imparted by
driving the cross lead screw with a stepper motor.
The parameters for milling of helical grooves set for trials were:
Tool material : HSS Grade M-15
Milling tool specifications : OD-0 75mm, 16 mm wide, 0 32 mm bore,
70 degree one side angle, 24 teeth, Left hand.
RPM of milling cutter : 144 RPM
No of helical grooves : 50 numbers on circumference.
Depth of cut : 1.98 mm (full depth).
Table-2, given below, shows the different variable parameters set during milling operation of helical grooves where columns represent three experimental trials, namely: Example-4 and Example-5, respectively and rows shows the variables set during trial.
Table-2

(Table Removed)
The function of the machine was found satisfactory and the machine was able to perform the milling operation on the CTC tea roller made of stainless steel material. The spacing of the grooves over the roller circumference and the milling depth of the milled helical grooves for above trials was found to be uniform.
Thus, it is obvious that the rollers manufactured / re-sharpened on the machine of the present invention will be of much greater accuracy and thereby result in production of properly matched pair of CTC or special purpose rollers. While in experimentation with the experimental model, involvement of the human-operator was much reduced due to the inbuilt automation of the process. Now, in one loading and programming through PLC, the process of the metal removal has become efficiently automated.
The main advantages of the present invention are:
1. Increased productivity.
2. More energy efficient.
3. Increased accuracy in machining is envisaged due to use of servo motor.
4. The servo drive assembly provides flexibility to the combined machine such that the milling cutter / chaser tool can return with faster speed to the starting position after completing the metal removal operation at slower speed and same movement can be repeated till the job is over.
5. The same servo drive unit also makes the job to rotate in milling / chasing operation.
6. Provides higher speed of roller rotation.
7. Minimum rotating components make the assembly simple.
8. Reduction in alignment complexity.
9. Minimum maintenance problem is envisaged due to less number of rotating components, such as motors, gears and electromagnetic clutches.

We claim:
1. An automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, which comprises: in combination a main frame mounted headstock (9) having chuck (26) and tailstock (24), capable of holding a job/roller (10) to be machined, characterized in that the said headstock (9) being provided with a servo drive unit (13, 14, 15), wherein servo motor (13) is connected by means such as a belt pulley (14) and an electro-magnetic clutch (15) to the said chuck (26) and also to the main lead screw (2) via a gear train (16) and an electro-magnetic clutch (25) capable of driving a horizontally placed saddle (3) having a cross lead screw (5) capable of driving a movable cross slide (4) provided with a milling head (7) and a chasing/cutting tool holder (6) placed diametrically with respect to the said job/roller (10) to be machined; the said headstock (9) being provided with an auto-indexing attachment (8) capable of indexing the job/roller (10) after each helical and annular groove.
2. An automatic machine for chasing and milling as claimed in claim 1, wherein the chuck (26) and main lead screw (2) with indexing attachment (8) is coupled through a gear train assembly (16), belt pulley arrangement (14), electromagnetic clutches (25,15) to the servo motor (13).

3. An automatic machine for chasing and milling as claimed in claim 1-2, wherein the servo drive (13) is capable to rotate the job (10) for both chasing and milling operations.
4. An automatic machine for chasing and milling as claimed in claim 1-3, wherein the servo drive unit (13,14,15) is essentially capable of providing slow longitudinal motion to the milling head (7) or chaser tool (6) during milling or chasing operation, respectively and rapid longitudinal return to the starting point in the non-cutting phase.
5. An automatic machine for chasing and milling as claimed in claim 1-4, wherein the milling tool /chaser tool crosswise positioning attachment, which consists of a stepper motor (18) coupled to a speed reducer gear box (19) and an electro-magnetic clutch (20), is essentially capable of providing incremental positioning at the required pitch to the milling tool/chaser tool (7 & 6) through the cross lead screw (5).
6. An automatic machine for chasing and milling as claimed in claim 1-5, wherein the cross lead screw (5) is coupled with a speed reducer gear box (19) and a stepper motor (18) along with clutch (20) in such a manner as to enable both chasing and milling operations using proximity switches as cross-home and cross-end position.
7. An automatic machine for chasing and milling as claimed in claim 1-6, wherein the milling head (7) is provided with a precise tilting arrangement consisting of an inbuilt micrometer arrangement consisting of worm wheel and vernier scale.
8. An automatic machine for chasing and milling as claimed in claim 1-7, wherein is provided an electronic control mechanism (11) which consists of a programmable logic controller coupled with stepper motor (18), servo motor (13), electromagnetic clutches (20, 15, 25), brake (17) and proximity switches, in such a manner as to be capable of providing programmed control to the main lead screw (2), cross lead screw (5), job (10) and auto-indexing attachment (8).
9. An automatic machine for chasing and milling as claimed in claim 1-8, wherein the characteristics of machining operations capabilities of the machine on job/roller are:
(iv)fully automatic chasing of annular groves; (v) fully automatic milling of helical grooves; and
(vi)turning operation on the roller with manual longitudinal feed of tool.
10. An automatic machine for chasing and milling as claimed in claim 1-9,
wherein the machine is capable of accommodating a job/roller of size in the
range of:
(a) total length of roller: 700 mm to 1600 mm;
(b) diameter of roller : 150 mm to 325 mm;
(c) maximum machinable length on roller: 1400 mm.

11. An automatic machine for chasing and milling as claimed in claim 1-10, wherein the pitch accuracy of the machine for annular chasing of grooves is of the order of 500 to 600 microns.
12. An automatic machine for chasing and milling of CTC (crushing, tearing and curling) tea rollers, substantially as herein described with reference to the examples and figures 2 to 5 of the drawings accompanying this specification.
Intellectual Property Management Division Council of Scientific and Industrial Research

Documents:

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Patent Number

270295

Indian Patent Application Number

394/DEL/2006

PG Journal Number

50/2015

Publication Date

11-Dec-2015

Grant Date

09-Dec-2015

Date of Filing

13-Feb-2006

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

ANUSANDHAN BHAWAN, RAFI MARG, NEW DELHI-110 001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	BANERJEE AMIT JYOTI	CMERI, M.G.AVENUE,DURGAPUR, DIST. BURDWAN, W.B., INDIA
2	SAHA PRNABENDU	CMERI, M.G.AVENUE,DURGAPUR, DIST. BURDWAN, W.B., INDIA
3	MUKHERJEE NARAYAN PRASAD	CMERI, M.G.AVENUE,DURGAPUR, DIST. BURDWAN, W.B., INDIA
4	DATTA UMA	CMERI, M.G.AVENUE,DURGAPUR, DIST. BURDWAN, W.B., INDIA
5	LANJEWAR RAJESH WASUDEO RAO	CMERI, M.G.AVENUE,DURGAPUR, DIST. BURDWAN, W.B., INDIA
6	GOPALSAMY BALAMURUGAN	CMERI, M.G.AVENUE,DURGAPUR, DIST. BURDWAN, W.B., INDIA

PCT International Classification Number

B23B 79/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA