Title of Invention	DRAWING CUSHION FIXTURE FOR METAL WORKING PRESS
Abstract	The invention releates to a hybrid drawing cushion facility which comprises a combination cylinders (6) and one or more electric drives (7, 15) acting upon the pressure box (3). The fluid cylinders (6) perform the force function on a high level and the electric drives (7,15) perform the path function, such as pre-acceleration and run-up, and the force function on a low level when the fluid cylinders (6) are deactivated.

Title of Invention

DRAWING CUSHION FIXTURE FOR METAL WORKING PRESS

Abstract

The invention releates to a hybrid drawing cushion facility which comprises a combination cylinders (6) and one or more electric drives (7, 15) acting upon the pressure box (3). The fluid cylinders (6) perform the force function on a high level and the electric drives (7,15) perform the path function, such as pre-acceleration and run-up, and the force function on a low level when the fluid cylinders (6) are deactivated.

Full Text	FORM 2 THE PATENT ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13) 1. TITLE OF INVENTION HYBRID DRAWING CUSHION FACILITY 2. APPLICANT(S) a) Name : MULLER WEINGARTEN AG b) Nationality : GERMAN Company c) Address : SCHUSSENSTRASSE 11, 8824 0 WEINGARTEN, GERMANY 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed : - ENGLISH TRANSLATION VARIFICATION CERTIFICATE u/r. 20(3)(b) I, Mr. HIRAL CHANDRAKANT JOSHI, an authorized agent for the apphcant, MULLER WEINGARTEN AG, do hereby verify that the content of English translated complete specification filed in pursuance of PCT International application No. PCT/DE2005/001094 thereof is correct and complete. HIRAL CHANDRAKANT JOSHI AGENT FOR MULLER WEINGARTEN AG Description The invention relates to a die cushion fixture as per main definition of the patent claim No. 1 State of technology Mechanical and hydraulic presses are machines of metal forming technology for processing of work pieces especially the sheet metal parts. For forming of deep drawn parts it is necessary to clamp the work piece in a special way between the upper and the lower tool of the press, for which purpose different types of sheet metal holding systems are known. From page Nos. 44 to 48 of the magazine Bleche Rohre Profile, 39 (1992) some die equipment have become known, which partly contain an expensive system of control to allow a targeted transmission of sheet metal holding forces. In die presses a distinction is made between so called double acting and single acting presses. In double acting die presses the ram of the hold down device which surrounds the press ram carries out a leading movement vis-avis the press ram and in the subsequent standstill moments it holds the sheet metal stop clamps on the metal as long as decided, in this case it clamps on under controlled expansion till the reforming process of work piece comes to an end. Such a control of hold down device during the drawing process is shown as example in DE 36 40 507 C2. Proportional or servo valves are used in this known equipment for controlling or regulating the pressure in the moldings of hold down device and thus for regulating holding down force, in doing so a sensor is coordinated with the hold down device cylinder, which regulates with the help of proportional or servo valve via a control equipment the required change of pressure in hold down device cylinder in conjunction with the respective drawing progress. Single acting presses there is a single press ram slide in comparison to the above mentioned device. Through the arrangement of an additional drawing apparatus in the press bed plate in case of single acting presses a drawing punch is fixed on the bed plate, while an additional hold down device is suspended as moveable on it. It is -2- under the action of pressure cap from below through several pressure pins. For this purpose a female drawing mould is fitted to a press ram slide. (Bleche Rohre Profile, 39(1992) page Nos. 44 and 45) In DE 32,42, 705, C2 a single acting drawing press is shown, in which the press pad arranged in the bed plate of press can be impacted by several cylinder units with locally varying cushion power, to enable processing of particularly asymmetrical large drawn parts requiring locally varying forces. Through this differential contiol of forces on a press pad a differential drawing capacity in the respective areas of the work piece can be achieved through targeted change in the drawing gap. With this process the differential pressures for holding down can be generated for the work pieces which require asymmetric power admission. Power controlling for a differential support to the press pad takes place, so that this passes on further differential power to the holding down device respectively to the work piece. From the EP 0 173 184 Bl also a press is known for drawing and deep drawing operations, which is developed as single acting press as well and whose hydraulically supported pressure pad acts on the tool bottom part or drawing punch. Also here through a targeted pressure impacting of the press pad the drawing process at the drawing punch can be influenced in the sense of sheet metal formation can be influenced. In all drawing cushion fixtures described above hydraulic cylinders are used for processing of controllable power acting on the press pad. For the generation of path functions like pre-acceleration, run-up holding with appropriate safety in locking positions, drawing depth adjustments significant mechanical, fluid and control engineering efforts are necessary. To avoid the collisions between the movement of drawing cushion fixture and, for example, casting transport elements increased efforts for movement control are required. While controlling the drawing powers hydraulics-dependent defined rninimum values cannot be undershot. -3- In the recent times drawing cushions have become known, in whose case cushion power is generated through electrical drives. In US 5 435 166 A a drawing equipment in the press bed is shown, which generates cushion power through servo drives, wherein the servo drive is joined with the cushion plate through gear and steering rack. In this arrangement, either several, servo drives coupled mechanically among themselves, can act jointly on a common press pad or one servo drive acts independently from the others on one press pad element of a multi-part press pad. From DE 42 92 190 TI a fixture in the bed of a testing press is known, whose press pad with motors is functionally so connected through a system of spindle-to-spindle nut that the resistance produced on cushion plate against the downward movement is controllable through motors. With the drive or driven motors coupled slippage-free electrically or mechanically the overturning movement of the press pad should be prevented. Disadvantages with such executions, is the coupling of individual drive motors. Particularly in large presses with multi-point drawing devices and single component press pad it is required in case of parts difficult to form, to apply different pressures and with forces varying during the drawing process on individual pressure points. Both the electrically operating drawing cushions described above have the disadvantage, that these have a large space requirement due to large number of mechanical motion transmission means, which in reality is not available. Task and advantage of the invention. The invention is based on the task - assuming from the status of technology - to improvise a drawing cushion fixture in such a way that while reducing expenses on controlling and regulating the regulating behavior is improved, and with a most compact design a variable power distribution at the hold down device is made possible. -4- This task is resolved starting from a drawing cushion fixture with hybrid drive as per main definition of claim 1, through the distinguishing characteristics of claim 1. Advantageous and practical further developments for the device are specified in the sub-claims. The central idea of the invention is to use the advantages of hydraulic drawing cushion as well as the electrically driven drawing cushion. This is achieved through a drawing device as per hybrid system with a combination of fluid cylinders and one or more electrical drives working on press pad where the fluid cylinders take over higher level power functions and the electrical device takes over the path functions, such as pre-acceleration and run-up as well as the power function of lower level while fluid cylinders are deactivated. Herein the power function and/or path function of electrical drive can be transmitted on the press pad on the one hand by means of a linear motor designed as direct drive and on the other hand by means of a servomotor with mechanical transmission on the pressure pad. The linear motors can be arranged in the inner areas of the press pad for example centrally between the fluid cylinders. Through direct energy conversion into a linear path function expensive mechanical transmissions causing increased moments of inertia can be saved. In advantageous manner secondary part belonging to the linear motor is fixed on to the press pad, which countered by one or more primary parts suspended in the press bed depending on the power requirement. It is likewise possible to arrange the linear motors in outer areas of the press pad. This way the secondary part can be suspended at the press pad as well as in the press bed. Apart from it, the externally located linear motor in the use of multi-part pressure pads allows common utilization of primary or secondary part through neighboring drawing cushion fixtures. In place of linear motors servo motors with mechanical transmission can be used as linear transducer, for example as electrical cylinder with spindle and spindle nut, -5- which are preferably arranged between fluid cylinders and are functionally connected with the press pad. As mechanical transmissions alternatively a steering rack with pinion and a lever mechanism between servomotor and press pad are possible. In advantageous manner, to coordinate with the movement of slide of press and of work piece transport elements, the electrical drives are connected through a pilot spindle to the plant control, whereby a permanent position check within the path function is realizable. For safety related locking of drawing cushion fixture in a holding position a motorized brake functionally connected with electrical drive can be activated. To improve the energy consumption of the press, energy storage as brake energy while bringing up on power or also during the cushion run-up in the electrical network or in the energy circuit of the press is possible. Further details and advantages of the invention are evident from the figures and are presented in detail in the following description of an execution example. Presented are: Fig. 1 Drawing cushion fixture according to the hybrid system with linear motors outside the press pad as section view. Fig. 2 Drawing cushion fixture according to the hybrid system with linear motor inside the press pad as section view. Fig. 3 Drawing cushion fixture according to the hybrid system with electrical cylinder as section view. Fig.4 Path v/s time diagram for drawing cushion fixture according to the hybrid system. Description of an execution example. Fig. 1 shows in a simplified representation a cut out of a press with drawing cushion fixture 2 (as multi-point design) arranged in press bed 1. -6- The press pad 3 guided lengthwise in press bed 1 stays on set bolt 4 functionally connected to the hold down device 5 of the bottom tool. For the generation of sheet metal holding power necessary for the drawing process and against the top tool in the press slide (not represented) between pressure pad 3 and press bed 1 fluid cylinders 6 are arranged. The sectional representation shows the first row with four fluid cylinders 6 of total eight point drawing fixture. During the drawing phase of the sheet metal form part, the press pad 3 is moved downwards through the movement of press slide ram, wherein the regulation of sheet metal holding power along the drawing path is done through valve controlled displacement of the fluid from the fluid cylinders 6. To generate active controlled path function like pre-acceleration, run-up including pickup, release and halting in locking phases according to the diagram for hybrid system as per fig. 4 15 linear motors 7 are used as electrical drives, whose primary and secondary parts 8, 9 are advantageously arranged between bed press 1 and press pad 3. In this the required arrangement of primary parts 8 on the press pad 3 or bed press 1 is possible. As per power requirement several linear motors 7 can be arranged along press pad 3. In this the linear motors 7 can either take up at the same time guiding function of the press pad 3 or the primary and secondary parts 8 and 9 are arranged independent of additional guide elements. In case of a drawing cushion fixture with multi-part press pad, it is advantageous that the neighboring press pads use a common primary or secondary part. In this, in case of arrangement of the primary part in the press bed the associate secondary parts get functionally connected to the press pad of the neighboring drawing cushion fixture. It is likewise conceivable, to arrange the secondary parts on the press pad, which stays always functionally connected to the primary part lying in-between them and is commonly usable. -7- In a second advantageous design as per fig. 2, the linear motor 7 is arranged approximately in the centre between the fluid cylinders 6 in order to generate the path function in the inner region of press pad 3. It is common in all the designs that the electrical energy of linear motor 7 acts directly without any additional mechanical transmissions as straight line path function via the press pad 3 on the hold down device 5. Herein it is possible, that as per demand of power requirement more number of primary parts 8 fixed on bed press 1 act together on secondary parts 9 fixed with the press pad 3. Fig. 3 shows a third design of drawing cushion fixture 2 with electric cylinder 10 acting on press pad 3. The electric cylinder 10 is arranged approximately in the centre amongst the surrounding fluid cylinders 6. In this design a system spindle/ spindle nut 12,11 is used as mechanical transmission 16. Spindle nut 11 connected with press pad 3 does not rotate and can move axially synchronous with the press pad 3. The associate spindle 12 is axially fix in press bed 1 and suspended as revolving around a fixed axes. The end of spindle 12 opposite to the spindle mutter 11 is above a coupling 13 with a servomotor 14 functionally connected. It is also possible without any extra transmission elements to use the extended shaft of the spindle as rotor of servomotor 14. In conjunction with the path / time course of cyclogram shown in fig. 4, the following functions in the drawing cushion device 2 repeat itself per press cycle as per hybrid system. Before the placement of upper work piece fixed to the ram slide-not shown- upon the hold down device 5 the hold down device 5 along with the sinker or mould meant for forming for the purpose of avoiding load due to disadvantageous impinging stroke is pre-accelerated in direction of ram movement. For this purpose the electrical drive 15 is maneuvered either as servo motor 14 or linear motor 7 in acting joint with a path measuring system or via guide shaft to suit the ram movement, so that after a defined acceleration path the top tool arrives on the sheet metal holder 5 with a sustained relative speed. After building up a defined -8- pressure in the fluid cylinders 6 the drawing power is reached, which is required for forming the sinker or the mould. The movement of the pressure pad 3 takes place during the drawing process in passive manner through the movement of the ram. According to the fluid cylinders 6 known from the state of technology in this drawing phase the drawing force per fluid cylinder 6 can be varied, as well as time-wise differing drawing forces between neighboring fluid cylinders 6 can be adjusted according to the technological requirements. The moving elements of the electrical drive 15 are during this drawing process either in an idle running phase or can store the energy back through switching in the generator mode. It is also possible that in case of smaller drawing forces the electrical drive 15 takeover the force functions through resistance controlled brake application in the generator mode. After running through the lower reversing point of the press according to Fig. 4 following path functions at the drawing cushion fixture 2 are possible: In case of non-delayed run up motion the pressure pad 3 follows the upward directed ram movement for the purpose of ejecting the formed drawn part in synchronous fashion. For this purpose the movement direction of the electrical drive(s) 15 is changed and the pressure pad 3 in the motor mode is actively driven. The fluid cylinders 6 are deactivated in this phase on the pressure side. It is also possible in case of delayed run-up motion to block the drawing cushion fixture 2 in its deepest position after running through the lower reversing point. The subsequent run-up motion for taking up a new sinker or mould follows with delay from a defined run-up start as per guide shaft for the ram movement. -9- During the guide path controlled path functions a synchronous movement of drawing cushion fixture 2 follows for the main movement of the ram, as well as for the sub-movement of, for example, work piece transport element, so that an anti-collision situation even in narrow tolerance window is ensured. List of Reference Symbols 1 Press bed 2 Drawing cushion fixture 3 Pressure pad 4 Pressure bolt 5 Sheet metal holder 6 Fluid cylinder 7 Linear motor 8 Primary part 9 Secondary part 10 Electrical cylinder 11 Spindle nut 12 Spindle 13 Coupling 14 Servo motor 15 Electrical drive 16 Mechanical transmission -10- WE CLAIM : 1. Drawing cushion fixture for a metal working press for regulating sheet metal holding force between tool lower part and tool upper part, in which the pressure application on the pressure pad (3) and whose movement can be regulated by means of a combination of at least one fluid cylinder (6) and at least one electrical drive (15) and at least one electrical drive (15) is actively connected with the pressure pad (3) is characterized by the fact that at least one electrical drive (15) is linear drive (7) designed as direct drive or an electrical cylinder (10) and is actively connected with the pressure pad (3) and the electrical drives (15) are actively connected within the press cycle sequential via a guide shaft with the ram movement. 2. Drawing cushion fixture as per claim 1 is characterized by the fact that the linear motor (7) is arranged within the pressure pad (3). 3. Drawing cushion fixture as per claim 1 is characterized by the fact that the linear motor (7) is arranged outside of the pressure pad (3). 4. Drawing cushion fixture as per claim 1 is characterized by the fact that in case of a multi-part pressure pad (3) the allocated primary or secondary parts (8, 9) are actively connected with a secondary or primary part (9, 8) commonly useful for neighboring pressure pads (3). 5. Drawing cushion fixture as per claim 1 to 4 is characterized by the fact that the electrical drives (15) can be outfitted with a motorized brake. 6. Drawing cushion fixture as per claim 1 to 5 is characterized by the fact that the pressure pad (3) can be locked with a controllable clamping device. -11- 7. Drawing cushion fixture as per claim 1 to 6 is characterized by the fact that the brake energy generated during the drawing lift in the electrical drive (15) can be stored back in generator fashion in the energy circuit of the press or in the electrical circuit. 8. Drawing cushion fixture as per claim 1 is characterized by the fact that the servo motor (14) and the mechanical transmission (16) are integrated in form of a steering rack/pinion or spindle/spindle nut (12, 11) in a compact electrical cylinder (10) 9. Drawing cushion fixture as per claim 1 is characterized by the fact that the mechanical transmission (16) is realized between electrical drive (15) and the pressure pad (3) through a lever mechanism. Dated this 5th day of January, 2007 ABSTRACT The invention releates to a hybrid drawing cushion facility which comprises a combination cylinders (6) and one or more electric drives (7, 15) acting upon the pressure box (3). The fluid cylinders (6) perform the force function on a high level and the electric drives (7,15) perform the path function, such as pre-acceleration and run-up, and the force function on a low level when the fluid cylinders (6) are deactivated. To, The Controller of Patents, The Patent Office, Mumbai

Full Text

FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION
HYBRID DRAWING CUSHION FACILITY
2. APPLICANT(S)
a) Name : MULLER WEINGARTEN AG
b) Nationality : GERMAN Company
c) Address : SCHUSSENSTRASSE 11,
8824 0 WEINGARTEN, GERMANY
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

ENGLISH TRANSLATION VARIFICATION
CERTIFICATE u/r. 20(3)(b)
I, Mr. HIRAL CHANDRAKANT JOSHI, an authorized agent for the apphcant, MULLER WEINGARTEN AG, do hereby verify that the content of English translated complete specification filed in pursuance of PCT International application No. PCT/DE2005/001094 thereof is correct and complete.

HIRAL CHANDRAKANT JOSHI
AGENT FOR
MULLER WEINGARTEN AG

Description
The invention relates to a die cushion fixture as per main definition of the patent
claim No. 1
State of technology
Mechanical and hydraulic presses are machines of metal forming technology for
processing of work pieces especially the sheet metal parts. For forming of deep
drawn parts it is necessary to clamp the work piece in a special way between the upper and the lower tool of the press, for which purpose different types of sheet metal holding systems are known. From page Nos. 44 to 48 of the magazine Bleche Rohre Profile, 39 (1992) some die equipment have become known, which partly contain an expensive system of control to allow a targeted transmission of sheet metal holding forces. In die presses a distinction is made between so called double acting and single acting presses. In double acting die presses the ram of the hold down device which surrounds the press ram carries out a leading movement vis-avis the press ram and in the subsequent standstill moments it holds the sheet metal stop clamps on the metal as long as decided, in this case it clamps on under controlled expansion till the reforming process of work piece comes to an end. Such a control of hold down device during the drawing process is shown as example in DE 36 40 507 C2.
Proportional or servo valves are used in this known equipment for controlling or regulating the pressure in the moldings of hold down device and thus for regulating holding down force, in doing so a sensor is coordinated with the hold down device cylinder, which regulates with the help of proportional or servo valve via a control equipment the required change of pressure in hold down device cylinder in conjunction with the respective drawing progress.
Single acting presses there is a single press ram slide in comparison to the above mentioned device. Through the arrangement of an additional drawing apparatus in the press bed plate in case of single acting presses a drawing punch is fixed on the bed plate, while an additional hold down device is suspended as moveable on it. It is
-2-

under the action of pressure cap from below through several pressure pins. For this purpose a female drawing mould is fitted to a press ram slide. (Bleche Rohre Profile, 39(1992) page Nos. 44 and 45)
In DE 32,42, 705, C2 a single acting drawing press is shown, in which the press pad arranged in the bed plate of press can be impacted by several cylinder units with locally varying cushion power, to enable processing of particularly asymmetrical large drawn parts requiring locally varying forces. Through this differential contiol of forces on a press pad a differential drawing capacity in the respective areas of the work piece can be achieved through targeted change in the drawing gap.
With this process the differential pressures for holding down can be generated for the work pieces which require asymmetric power admission. Power controlling for a differential support to the press pad takes place, so that this passes on further differential power to the holding down device respectively to the work piece. From the EP 0 173 184 Bl also a press is known for drawing and deep drawing operations, which is developed as single acting press as well and whose hydraulically supported pressure pad acts on the tool bottom part or drawing punch. Also here through a targeted pressure impacting of the press pad the drawing process at the drawing punch can be influenced in the sense of sheet metal formation can be influenced.
In all drawing cushion fixtures described above hydraulic cylinders are used for processing of controllable power acting on the press pad. For the generation of path functions like pre-acceleration, run-up holding with appropriate safety in locking positions, drawing depth adjustments significant mechanical, fluid and control engineering efforts are necessary. To avoid the collisions between the movement of drawing cushion fixture and, for example, casting transport elements increased efforts for movement control are required. While controlling the drawing powers hydraulics-dependent defined rninimum values cannot be undershot.
-3-

In the recent times drawing cushions have become known, in whose case cushion power is generated through electrical drives.
In US 5 435 166 A a drawing equipment in the press bed is shown, which generates cushion power through servo drives, wherein the servo drive is joined with the cushion plate through gear and steering rack. In this arrangement, either several, servo drives coupled mechanically among themselves, can act jointly on a common press pad or one servo drive acts independently from the others on one press pad element of a multi-part press pad.
From DE 42 92 190 TI a fixture in the bed of a testing press is known, whose press pad with motors is functionally so connected through a system of spindle-to-spindle nut that the resistance produced on cushion plate against the downward movement is controllable through motors. With the drive or driven motors coupled slippage-free electrically or mechanically the overturning movement of the press pad should be prevented.
Disadvantages with such executions, is the coupling of individual drive motors. Particularly in large presses with multi-point drawing devices and single component press pad it is required in case of parts difficult to form, to apply different pressures and with forces varying during the drawing process on individual pressure points. Both the electrically operating drawing cushions described above have the disadvantage, that these have a large space requirement due to large number of mechanical motion transmission means, which in reality is not available.
Task and advantage of the invention.
The invention is based on the task - assuming from the status of technology - to
improvise a drawing cushion fixture in such a way that while reducing expenses on
controlling and regulating the regulating behavior is improved, and with a most
compact design a variable power distribution at the hold down device is made
possible.
-4-

This task is resolved starting from a drawing cushion fixture with hybrid drive as per main definition of claim 1, through the distinguishing characteristics of claim 1. Advantageous and practical further developments for the device are specified in the sub-claims.
The central idea of the invention is to use the advantages of hydraulic drawing cushion as well as the electrically driven drawing cushion. This is achieved through a drawing device as per hybrid system with a combination of fluid cylinders and one or more electrical drives working on press pad where the fluid cylinders take over higher level power functions and the electrical device takes over the path functions, such as pre-acceleration and run-up as well as the power function of lower level while fluid cylinders are deactivated. Herein the power function and/or path function of electrical drive can be transmitted on the press pad on the one hand by means of a linear motor designed as direct drive and on the other hand by means of a servomotor with mechanical transmission on the pressure pad.
The linear motors can be arranged in the inner areas of the press pad for example centrally between the fluid cylinders. Through direct energy conversion into a linear path function expensive mechanical transmissions causing increased moments of inertia can be saved. In advantageous manner secondary part belonging to the linear motor is fixed on to the press pad, which countered by one or more primary parts suspended in the press bed depending on the power requirement.
It is likewise possible to arrange the linear motors in outer areas of the press pad. This way the secondary part can be suspended at the press pad as well as in the press bed. Apart from it, the externally located linear motor in the use of multi-part pressure pads allows common utilization of primary or secondary part through neighboring drawing cushion fixtures.
In place of linear motors servo motors with mechanical transmission can be used as linear transducer, for example as electrical cylinder with spindle and spindle nut,
-5-

which are preferably arranged between fluid cylinders and are functionally connected with the press pad. As mechanical transmissions alternatively a steering rack with pinion and a lever mechanism between servomotor and press pad are possible.
In advantageous manner, to coordinate with the movement of slide of press and of work piece transport elements, the electrical drives are connected through a pilot spindle to the plant control, whereby a permanent position check within the path function is realizable.
For safety related locking of drawing cushion fixture in a holding position a motorized brake functionally connected with electrical drive can be activated. To improve the energy consumption of the press, energy storage as brake energy while bringing up on power or also during the cushion run-up in the electrical network or in the energy circuit of the press is possible.
Further details and advantages of the invention are evident from the figures and are presented in detail in the following description of an execution example. Presented are: Fig. 1 Drawing cushion fixture according to the hybrid system with linear motors
outside the press pad as section view. Fig. 2 Drawing cushion fixture according to the hybrid system with linear motor
inside the press pad as section view. Fig. 3 Drawing cushion fixture according to the hybrid system with electrical
cylinder as section view. Fig.4 Path v/s time diagram for drawing cushion fixture according to the hybrid
system.
Description of an execution example.
Fig. 1 shows in a simplified representation a cut out of a press with drawing cushion
fixture 2 (as multi-point design) arranged in press bed 1.
-6-

The press pad 3 guided lengthwise in press bed 1 stays on set bolt 4 functionally connected to the hold down device 5 of the bottom tool. For the generation of sheet metal holding power necessary for the drawing process and against the top tool in
the press slide (not represented) between pressure pad 3 and press bed 1 fluid cylinders 6 are arranged. The sectional representation shows the first row with four fluid cylinders 6 of total eight point drawing fixture. During the drawing phase of the sheet metal form part, the press pad 3 is moved downwards through the movement of press slide ram, wherein the regulation of sheet metal holding power along the drawing path is done through valve controlled displacement of the fluid from the fluid cylinders 6.
To generate active controlled path function like pre-acceleration, run-up including pickup, release and halting in locking phases according to the diagram for hybrid system as per fig. 4 15 linear motors 7 are used as electrical drives, whose primary and secondary parts 8, 9 are advantageously arranged between bed press 1 and press pad 3. In this the required arrangement of primary parts 8 on the press pad 3 or bed press 1 is possible. As per power requirement several linear motors 7 can be arranged along press pad 3. In this the linear motors 7 can either take up at the same time guiding function of the press pad 3 or the primary and secondary parts 8 and 9 are arranged independent of additional guide elements.
In case of a drawing cushion fixture with multi-part press pad, it is advantageous that the neighboring press pads use a common primary or secondary part. In this, in case of arrangement of the primary part in the press bed the associate secondary parts get functionally connected to the press pad of the neighboring drawing cushion fixture. It is likewise conceivable, to arrange the secondary parts on the press pad, which stays always functionally connected to the primary part lying in-between them and is commonly usable.
-7-

In a second advantageous design as per fig. 2, the linear motor 7 is arranged approximately in the centre between the fluid cylinders 6 in order to generate the path function in the inner region of press pad 3.
It is common in all the designs that the electrical energy of linear motor 7 acts directly without any additional mechanical transmissions as straight line path function via the press pad 3 on the hold down device 5. Herein it is possible, that as per demand of power requirement more number of primary parts 8 fixed on bed press 1 act together on secondary parts 9 fixed with the press pad 3.
Fig. 3 shows a third design of drawing cushion fixture 2 with electric cylinder 10 acting on press pad 3. The electric cylinder 10 is arranged approximately in the centre amongst the surrounding fluid cylinders 6. In this design a system spindle/ spindle nut 12,11 is used as mechanical transmission 16.
Spindle nut 11 connected with press pad 3 does not rotate and can move axially synchronous with the press pad 3. The associate spindle 12 is axially fix in press bed 1 and suspended as revolving around a fixed axes. The end of spindle 12 opposite to the spindle mutter 11 is above a coupling 13 with a servomotor 14 functionally connected. It is also possible without any extra transmission elements to use the extended shaft of the spindle as rotor of servomotor 14.
In conjunction with the path / time course of cyclogram shown in fig. 4, the following functions in the drawing cushion device 2 repeat itself per press cycle as per hybrid system. Before the placement of upper work piece fixed to the ram slide-not shown- upon the hold down device 5 the hold down device 5 along with the sinker or mould meant for forming for the purpose of avoiding load due to disadvantageous impinging stroke is pre-accelerated in direction of ram movement. For this purpose the electrical drive 15 is maneuvered either as servo motor 14 or linear motor 7 in acting joint with a path measuring system or via guide shaft to suit the ram movement, so that after a defined acceleration path the top tool arrives on the sheet metal holder 5 with a sustained relative speed. After building up a defined
-8-

pressure in the fluid cylinders 6 the drawing power is reached, which is required for forming the sinker or the mould.
The movement of the pressure pad 3 takes place during the drawing process in passive manner through the movement of the ram. According to the fluid cylinders 6 known from the state of technology in this drawing phase the drawing force per fluid cylinder 6 can be varied, as well as time-wise differing drawing forces between neighboring fluid cylinders 6 can be adjusted according to the technological requirements. The moving elements of the electrical drive 15 are during this drawing process either in an idle running phase or can store the energy back through switching in the generator mode.
It is also possible that in case of smaller drawing forces the electrical drive 15 takeover the force functions through resistance controlled brake application in the generator mode.
After running through the lower reversing point of the press according to Fig. 4 following path functions at the drawing cushion fixture 2 are possible:
In case of non-delayed run up motion the pressure pad 3 follows the upward directed ram movement for the purpose of ejecting the formed drawn part in synchronous fashion. For this purpose the movement direction of the electrical drive(s) 15 is changed and the pressure pad 3 in the motor mode is actively driven. The fluid cylinders 6 are deactivated in this phase on the pressure side.
It is also possible in case of delayed run-up motion to block the drawing cushion fixture 2 in its deepest position after running through the lower reversing point. The subsequent run-up motion for taking up a new sinker or mould follows with delay from a defined run-up start as per guide shaft for the ram movement.
-9-

During the guide path controlled path functions a synchronous movement of drawing cushion fixture 2 follows for the main movement of the ram, as well as for the sub-movement of, for example, work piece transport element, so that an anti-collision situation even in narrow tolerance window is ensured.

List of Reference Symbols
1 Press bed
2 Drawing cushion fixture
3 Pressure pad
4 Pressure bolt
5 Sheet metal holder
6 Fluid cylinder
7 Linear motor
8 Primary part
9 Secondary part
10 Electrical cylinder
11 Spindle nut
12 Spindle
13 Coupling
14 Servo motor
15 Electrical drive
16 Mechanical transmission
-10-

WE CLAIM :
1. Drawing cushion fixture for a metal working press for regulating sheet metal holding force between tool lower part and tool upper part, in which the pressure application on the pressure pad (3) and whose movement can be regulated by means of a combination of at least one fluid cylinder (6) and at least one electrical drive (15) and at least one electrical drive (15) is actively connected with the pressure pad (3) is characterized by the fact that at least one electrical drive (15) is linear drive (7) designed as direct drive or an electrical cylinder (10) and is actively connected with the pressure pad (3) and the electrical drives (15) are actively connected within the press cycle sequential via a guide shaft with the ram movement.
2. Drawing cushion fixture as per claim 1 is characterized by the fact that the linear motor (7) is arranged within the pressure pad (3).
3. Drawing cushion fixture as per claim 1 is characterized by the fact that the linear motor (7) is arranged outside of the pressure pad (3).
4. Drawing cushion fixture as per claim 1 is characterized by the fact that in case of a multi-part pressure pad (3) the allocated primary or secondary parts (8, 9) are actively connected with a secondary or primary part (9, 8) commonly useful for neighboring pressure pads (3).
5. Drawing cushion fixture as per claim 1 to 4 is characterized by the fact that the electrical drives (15) can be outfitted with a motorized brake.
6. Drawing cushion fixture as per claim 1 to 5 is characterized by the fact that the pressure pad (3) can be locked with a controllable clamping device.
-11-

7. Drawing cushion fixture as per claim 1 to 6 is characterized by the fact that the brake energy generated during the drawing lift in the electrical drive (15) can be stored back in generator fashion in the energy circuit of the press or in the electrical circuit.
8. Drawing cushion fixture as per claim 1 is characterized by the fact that the servo motor (14) and the mechanical transmission (16) are integrated in form of a steering rack/pinion or spindle/spindle nut (12, 11) in a compact electrical cylinder (10)
9. Drawing cushion fixture as per claim 1 is characterized by the fact that the mechanical transmission (16) is realized between electrical drive (15) and the pressure pad (3) through a lever mechanism.
Dated this 5th day of January, 2007

ABSTRACT
The invention releates to a hybrid drawing cushion facility which comprises a combination cylinders (6) and one or more electric drives (7, 15) acting upon the pressure box (3). The fluid cylinders (6) perform the force function on a high level and the electric drives (7,15) perform the path function, such as pre-acceleration and run-up, and the force function on a low level when the fluid cylinders (6) are deactivated.
To,
The Controller of Patents,
The Patent Office,
Mumbai

DRAWING CUSHION FIXTURE FOR METAL WORKING PRESS

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