|Title of Invention||
ALL ELECTRIC SERVO-TURRET FOR CNC LATHES
|Abstract||ABSTRACT: Disclosed herein is an Electric Servo-turret, wherein the use of hydraulic cylinders are avoided. A further object of the invention is to provide an improved clamping system, which provides higher clamping force. Yet another object of the present invention is to provide a method of clamping/de-clamping of tool turret or indexing table using an electric motor.|
This invention relates to an All Electric Servo-Turret for CNC lathes and a method of clamping /de-clamping of tool turret or indexing table.
It is known in the art to use Hydraulic Cylinder for clamping and de-clamping of Servo Turrets. To create the necessary force for clamping and de-clamping, generally high pressure hydraulics are required. When pressure hydraulics is used it requires additional equipment such as Hydraulic power pack (Pump, motor, tank, filters, valves, hoses etc), which involves additional cost and additional space requirement.
Accordingly, it is an object of the present invention to provide an Electric Servo-Turret wherein the use of hydraulic cylinders are avoided. A further object of the invention is to provide an improved clamping system, which provides higher clamping force. Yet another object of the present invention is to provide a method of clamping / de-clamping of tool turret or indexing table using an electric motor. When hydraulic cylinders are used for clamping the turret, continuous pressure is required to keep it clamped. It consumes power. Also in case of oil hose rupture turret will de-clamp and cause damage to machine or components. The Disc clamp mechanism of the present invention, when operated with electric motor in the servo turrets additional costs for hydraulic power pack and space are eliminated. Also the clamping is inherently safe because it is always clamped with high force springs. Power is required to de-clamp and move the turret.
This invention thus provides an Electric Servo Turret consisting of the foUowing:-
a) Indexing drive or system,
b) Face tooth/gear Coupling; and
c) Clamping system consisting of a Cam system to clamp and de-clamp the turret and an Electric motor (6) to drive the system.
The indexing system in the Electric Servo Turret described above consists of Servo Motor (1), a Reduction Gearing (2), a Spindle (3), and Encoder (4) and a Tool Disc (5) and the Cam System consists of a Reduction Gearing (7), a Drum Cam (8), a Disc-Spring (9) along with the Electric Motor (6), for e.g. an Induction Motor.
In the present invention, electrical drive is used for clamping the tool disc. Other comparable products make use of compressed air or pressure hydraulic. Use of electric drive with clamping mechanism consisting air or make the turret compact, which require less maintenance. Cam mechanism is driven by electric motor to clamp the servo turret. Disc springs are used to keep the turret clamped so that no power is required to keep the turret clamped.
The Drum Cam Assembly in the Servo-turret consists of Cam Gear (10), Cam Ring (11), 3 Rollers at 120°(12), a Sliding Coupling (13) and a Key (14) to prevent rotation of the Sliding Coupling. A 90° rotation of the Cam Gear (10) moves the sliding coupling into clamping position and the teeth of the Sliding Coupling (13) firmly engage with the teeth of fixed Coupling (15) and Indexing Coupling (16).
In a further embodiment of the present invention, Proximity Switches (17) are provided to provide signals of the 'Clamp / de-Clamp' the position of the turret.
Advantages of electrical clamping of servo turret.
> Additional equipment like hydraulic power pack is avoided.
> Only electric wires for motor are required.
> Use of long hydraulic hoses is eliminated which are generally bulkier than electrical cable.
> Continuous use of power is avoided to keep the turret clamped. Power is required only during the indexing of the turret.
> The Servo turret of the present invention does not depend on external power to keep the servo turret clamped.
> There is no possibility of turret getting vmclamped because of rupture of oil hoses through which oil at pressure is supplied to the cylinder inside the turret.
Basically tool turret is an indexing mechanism used to index cutting tools on the lathes. Its job is to bring required tool in cutting position. The indexing mechanism used to index the components to be machined is normally referred as 'Indexing table'. The tool turret can be used as indexing table when component is placed in place of 'Tool Disc'. With this arrangement it is possible to machine for e.g., a hexagon at the end of the bar by indexing (rotating) the component and holding it rigidly for machining.
This invention will now be described with reference to the drawings accompanying the provisional specification, wherein:
Fig 1 illustrates a typical outside view of the tool turret;
Fig 2 illustrates a conventional servo-turret using hydraulic cylinder for clamping/de-clamping. Fig 3 illustrates the servo-turret of the present invention; and Fig 4 illustrates the Drum-cam assembly of the servo-turret shown in Fig-3
Tool turrets are used on CNC lathes to (accommodate a number of tools on its tool disc) act as tool magazines; and to bring the desired tool in working position, as per the instructions from CNC control. Typical outside view of a Tool turret is shown in Fig-1.
Tool turrets have 3 basic components: 'Indexing drive'; 'face tooth coupling'; and 'clamping system', (fig 2). In the provisional specification, the term 'face tooth coupling' is called as 'face gear coupling' and it is a general term used for toothed coupling with teeth machined on the face of round disc. Teeth could have a variety of shapes. Straight teeth like that of 180° bevel gear are common (such as Hirth Coupling). Another common tooth form is circular arc (popularly known as Gleason curvic coupling). Important property of face tooth coupling mentioned above is the 'repeat positioning accuracy' and 'rigidity' under clamped condition. These couplings are therefore commonly used for indexing applications.
Indexing drive is obtained either by induction motor; or by hydraulic motor; or by Servo-Motor. Repeat positioning accuracy of the tool is provided by 'face tooth/gear coupling'.
Clamping force can be obtained through a hydraulic cylinder, or by mechanical arrangement using a disc spring.
SUBJECT OF THE PATENT:
The present invention relates to Electric Servo-Turret for CNC lathes. The prior art of the Servo-Turret use Hydraulic Cylinder for Clamping/De-clamping purposes (Fig-2). It is therefore necessary to use electrical wiring as well as Hydraulic Hoses for the operation of this Servo-Turret. These turrets require high-pressure hydraulics for providing sufficient clamping force; and enough oil flow to provide fast clamp/de-clamp actions. These turrets therefore require additional costs of special hydraulics; and involve long piping and hoses to carry oil to the moving turret, mounted on the lathe saddle.
Accordingly, it is an object of the present invention to use as Electric Motor and de-clamping system to Clamp/de-Clamp the Turret. It thus eliminates the use of hydraulics and saves on its associated costs. It avoids complicated hydraulic supply lines required to connect to a moving turret and thus helps in making a cleaner looking lathe. Electrical clamping also provides much higher clamping force, in comparison to the hydraulic systems. An electric motor can be switched off after the clamping operation because the clamping force is obtained through a spring; whereas in hydraulic systems the hydraulic pressure must be continuously maintained to keep the turret clamped.
From the mechanism described in Figure 3, it can be seen that this Turret has two independent system; 'Indexing System' driven by a Servo-Motor, and 'Clamping System' driven by a separate electric motor.
Indexing system consists of Servo-motor (1), reduction gearing or indexing drive (2), spindle (3), encoder (4) and tool disc (5).
Clamping system consists of induction motor (6), reduction gearing (7), drum cam assembly (8) and disc-spring (9). Drum Cam assembly (fig 4) consists of cam gear (10), cam ring (11), 3 rollers at 120°(12), and the sliding coupling (13). Sliding coupling is prevented from rotation by key (14). Typically, 90° rotation of cam gear will move the slidmg coupling into clamping position. In this position, teeth of sliding coupling (13)
firmly engage with the teeth of fixed coupling (15), and indexing coupling (16). Simultaneously, drum cam assembly compresses the disc spring (9); so that full force of these springs is applied on the coupling teeth, thus clamping the tool disc in position. Rotation of cam gear in reverse direction, back to original position, causes the sliding coupling to come back to original position, thus disengaging the coupling teeth.
Thus, rotation of drum cam gear by approximate 90°, to 'clamp' position will clamp the turret; and rotating it back by the same angle to original de-clamp position will de-clamp the turret.
Induction motor (6) provides the power for rotating the cam gear from 'clamp' position to 'de-clamp' position; and vice versa. Motor is switched off in the correct position with the help of signals from proximity switches (17) and the lead stops. These switch signals are also used to confirm the 'clamp' or 'de-clamp' position of the turret. The proximity switch is an electro magnetic device in which the magnetic field changes when a metallic object comes near the same. The change in magnetic filed is sensed by electronics in the proximity switch and it gives and output signal. Proximity switch is a non-contact limit switch and the same is used in a turret to sense the gear position.
The indexing cycle of the present invention consists of 3 operations; 'declamp index clamp'. This cycle is obtained by controlling two motors with the help of PLC (programmable logic control), and CNC.
Initial position of turret is as follows:
Both the motors are switched off. 'Clamp' Proximity switch indicates that the turret is in clamped position. Encoder signals indicate the current index position.
When a new tool demand is received; clamp motor is switched ON. As soon as de-clamp position is reached, 'de-clamp' proximity signal switches the motor off. Position control drive of Servo-Motor now takes control, and indexes the turret to its new, demanded position. After reaching the position, Servo-Motor is switched OFF; and 'clamp' motor is switched on in reverse direction to clamp the turret in position. 'Clamp' proximity switch
then switches the motor 'off after the turret is clamped in position. This completes the indexing cycle.
This mechanism was described in the context of a tool turret. However, it is also appUcable to other indexing systems like 'Index Tables'. The Invention of this mechanism should cover these related applications; including specially the index tables.
1. An Electric Servo Turret consisting of:
a) Indexing drive a system, driven by servo motor; and
b) Clamping system consisting of a cam system to clamp and de-clamp the turret and an electric induction motor (6) to drive the system.
2. An electric servo turret as claimed in claim 1, wherein the indexing system consists of Servo Motor (1), a reduction gearing (2), a spindle (3), an Encoder (4), a Tool Disc (5) and Face Tooth Coupling (13, 14, 15).
3. An Electric Servo Turret as claimed in claim 1, wherein the Clamping system consisting of a Cam system comprising Reduction gearing (7), a Drum Cam (8), a Disc-Spring (9) along with the Electric induction Motor (6).
4. An Electric Servo Turret as claimed in Claim 1, wherein the clamping system consisting of a Drum Cam Assembly comprising of Cam Gear (10), Cam Ring (11), 3 Rollers at 120° (12), a Sliding Coupling (13), and a Key (14) to prevent rotation of the Sliding Coupling.
5. An Electric Servo Turret as claimed in claim 1, comprising a clamping system, wherein a part rotation of the Cam Gear (10) moves the sliding coupling into clamping position and reverse rotation by the same angle pulls the sliding coupling out of engagement.
6. An Electric Servo Turret as claimed in Claim 1, comprising a clamping system, wherein the teeth of the Sliding Coupling (13) firmly engage with the teeth of fixed Coupling (15) and Indexing Coupling (16).
7. An Electric Servo Turret as claimed in claim 1, comprising a clamping system, wherein Proximity Switches (17) are provided to provide signals of the 'clamp' or 'de-clamp' position of the Turret.
8. A Clamping system for electric servo turret consisting of a cam system to clamp and de-clamp the turret and an electric induction Motor (6) to drive the system.
9. A Clamping system as claimed in claim 8, wherein the cam system consists of reduction gearing (7), a drum cam assembly (8), a disc spring (9) along with an electric induction motor (6).
10. A clamping system as claimed in Claim 9, wherein the Drum Cam Assembly consists of Cam Gear (10), Cam Ring (11), 3 Rollers at 120° (12), a Sliding Coupling (13), and a Key (14) to prevent rotation of the Sliding Coupling.
11. A clamping system as claimed in Claim 10, wherein a part rotation of the Cam Gear (10) moves the sliding coupling into clamping position and reverse rotation by the same angle pulls the sliding coupling out of engagement.
12. A clamping system as claimed in Claim 11, wherein the teeth of the Sliding Coupling (13) firmly engage with the teeth of fixed Coupling (15) and Indexing Coupling (16).
13. A clamping system as claimed in any one of claims 8 to 12, wherein Proximity Switches (17) are provided to provide signals of the 'clamp' or 'de-clamp' position of the Turret.
14. An indexing table using the indexing system and clamping system as claimed in claims 1 to 13.
15. A method of clamping/de-clamping of tool turret or indexing table comprising the steps of:
a. switching the clamp motor 'ON', when a new tool demand is received,
using the programmable logic controller;
b. switching the motor 'OFF' using the 'de-clamp' proximity switches as
soon as the 'de-clamp' position is reached;
c. indexing the turret/indexing table to the new demanded position through
the position control drive of the Servo-motor;
d. switching 'OFF' the Servo-motor once the new position is reached;
e. switching the 'clamp' motor 'ON' in the reverse direction to clamp the
turret/ indexing table in the new position; and
f. switching the motor 'OFF' using the 'clamp' proximity switch after the
turret is clamped in position.
|Indian Patent Application Number||1228/MAS/1999|
|PG Journal Number||20/2006|
|Date of Filing||27-Dec-1999|
|Name of Patentee||PRAGATI ENGINEERING WORKS|
|Applicant Address||NO.413, 4TH PHASE, 11TH CROSS, PEENYA INDUSTRIAL AREA, BANGALORE 560 058|
|PCT International Classification Number||B23B3/16|
|PCT International Application Number||N/A|
|PCT International Filing date|