FORM 2 The Patents Act 1970
(39 of 1970) &
The Patent Rules 2003 COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
WEDGE CAM ASSEMBLY FOR RIVETING MAGNET
IN PRESS TOOLS
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278, Mumbai, 400 001, Maharashtra INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED



A) TECHNICAL FIELD
[1] The present invention generally relates to press tool assemblies and particularly to the press tools used in production of electromagnets by riveting mechanism. More particularly the present invention provides a cam arrangement in press tools to control the bulging of electromagnets during riveting operation.
B) BACKGROUND OF THE INVENTION
[2] A press or a machine press is a tool used to work on a metal by changing the metals shape and internal structure. In one of the industrial applications, a press tool is used in production of electromagnets by the riveting operation. The electromagnets are made by joining a stack of stampings made of silicon steel sheet by using a riveting process. The laminations of the silicon steel sheet are stacked and rivets are inserted into holes provided in the laminations. The rivet has a head at the top and a loose end at the bottom. The loose ends are upset to form a rivet head on other side of the stack.
[3] The press tool includes two halves, namely a fixed bottom half and a moving top half. The fixed bottom half is secured to a stationary bolster plate of hydraulic press. The hydraulic press includes an arrangement for locating the stack of laminations, sizing the stack, and for removing the electromagnet assembly after riveting. The press has guide pillars for the alignment of both the fixed and moving halves. The location arrangement for the lamination stack includes two halves such as a moving half on the left side of an operator and a moving half on the right side of the operator. Both the moving halves of the location arrangement are actuated by pneumatic cylinders. The moving top half is clamped to the moving ram of the hydraulic pres. The moving top half also includes numerous round riveting punches housed in a block clamped to the top bolster.

[4] At first, the left moving half of the guiding arrangement is moved in and the stack of laminations are kept on ejector block which is positioned against a locating block. During the downward stroke, the moving parts on the right hand side and left hand side of the press tool are engaged by the guide pins from the top half. The block clamps the stack and pushes it down against a floating block called the ejector block. The registration of the locating blocks by the guide pins from the top creates a finite gap in the location arrangement for the lamination stack. The ejector block is provided with the stationary round punches which are guided into the block and held in a plate called punch holder plate. The downward movement of the ejector block causes a relative movement between the stationary round punches and the ejector block resulting in upsetting the loose ends of the rivets to form a rivet head.
[5] After the riveting operation, the top half moves up and the riveted stack moves up along with the floating ejector block. The locating moving half on the right side moves away from the riveted stack and the stack is removed manually or by other means. However, due to the riveting operation, the sideways bulging of the riveted stack takes place thereby pushing the locating block on the right side. Since the locating block moves sideways, it becomes tough to control the bulging effect on the riveted stack. Moreover, the sideways movement of the locating block results into deflection and breakage of the guide pins in the top half. The uncontrolled bulging creates quality problems and the guide pin breakage results into the downtime of press tool.
[6] In light of the foregoing discussion, there exists a need to provide a cam arrangement in riveting die to control the bulging of magnets during the riveting operation. Also there exists a need to develop the riveting die without using the guide pin thereby preventing the pin breakage and the downtime of the press tool.
[7] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

C) OBJECT OF THE INVENTION
[8] The primary object of the present invention is to develop a wedge cam assembly for riveting die in press tool assembly to control the bulging of magnets during riveting operation.
[9] Another object of the present invention is to develop a wedge cam assembly for riveting magnets in a press tool assembly to avoid the sideways movement of the locating block in the riveting die due to bulging of electromagnets to prevent the deflection and the breakage of the guide pins in the top half of the press tool.
Yet another object of the present invention is to develop a wedge cam assembly without requiring the use of the guide pins thereby eliminating the breakage of the guide pin and the downtime of the press tool due to the bulging of electromagnetic stack during the riveting operation.
[11] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[12] The various embodiments of the present invention provide a cam assembly for riveting magnets in a press tool assembly to control the bulging of the magnets during the riveting operation. The assembly avoids the sideways movement of a locating block of the riveting die due to the bulging of electromagnets to prevent the deflection and breakage of Guide pins.
[13] According to one embodiment of the present invention, a wedge cam assembly for riveting magnets in a press tool assembly has a cam mechanism provided in a top half of the press tool. A retainer plate is arranged above the cam mechanism. A spring is mounted above the retainer plate. A guide block is fixed to

[14] the top plate in the press tool. A guide slot is provided in the guide block. Atleast one locating block is arranged below the guide block. The cam mechanism and the locating block has tapered profile so that the cam mechanism is engaged with the locating block to arrest the movement of the locating block, when the top half is moved downwardly.
[14] The cam mechanism has a taper surface at the bottom. The locating block has a slot to receive the cam mechanism during the downward movement of the top half. The slot on the locating block has a tapered surface on the top side. The tapered profile on the cam mechanism and the tapered profile on the locating block are identical. The tapered profile on the cam mechanism and the tapered profile on the locating block are identical. The taper angle in the cam mechanism and the taper angle in the slot are identical.
[15] The locating blocks are provided in the right hand side and in the left hand side of an ejector block holding the laminated stack of the magnet assembly. The locating blocks are moved to hold the laminated stack of magnet assembly in position during the riveting operation.
[16] The tapered surface of the cam mechanism is received in the tapered slot of the locating block to make the cam mechanism to engage with the locating block to exert a wedge effect on the locating block to prevent the movement of the locating block to control the bulging of the magnet assembly during the riveting operation, when the top half is moved downwardly. The cam mechanism is moved through the guide slot in the guide block during the downward movement of the top half.
The cam mechanism has a height such that the tapered surface of the cam mechanism engages with the tapered slot on the locating block only after the movement of the locating block to hold the laminated stack of magnet assembly but before the starting of the riveting process.

[17] The guide block has a slot to guide and move the cam mechanism in vertical direction. The guide block is fixed to the bottom surface of the top piate through a fastener. The guide block is fixed to the bottom surface of the top plate through Allen screws. The guide block is fixed to the bottom surface of the top plate through dowel pins. The guide block has a slot to accommodate the retainer plate of the cam mechanism.
[18] The retainer plate has a size which is greater than the size of the cam mechanism to retain the cam mechanism within the guide block. The spring rests on the retainer plate. The spring is accommodated in a top plate provided in the top half of the press tool sothat any extra movement of the top half of the press tool pushes the cam mechanism up and the upward movement of the cam is allowed by the deflection of the spring.
According to one embodiment of the present invention, a cam is retained in top half of the riveting die. The cam is guided through a guide block which is fixed to top plate of the riveting die The Cam is provided with a taper surface at the bottom on left hand side of the cam. Further the cam is provided with a retainer plate and a light spring which are mounted above the cam.
[20] According to one embodiment of the present invention, moving part of guiding arrangement on right hand side of the riveting die has a locator slot with taper surface on left side of the locator slot. Taper angle in the locator slot is identical to that of taper on the cam. During the downward movement of the top half of the riveting die, the tapered surface on the cam engages with the tapered surface on the right hand side of the locating block. The taper locking between the tapered cam and the tapered locating block exerts a wedge effect on the locating block. Further, the wedge effect on the locating block prevents the locating block on right side from shifting due to the bulging effect of the electromagnets during riveting operation. Thus the wedge effect controls the bulging in electromagnet during riveting operation. Once the cam gets engaged with the locating block, the extra downward movement of

[21] the cam is compensated by the deflection of springs provided in the cam and the cam is pushed upwards.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[21] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[22] FIG. 1 illustrates a top side plan view of a bottom half in a riveting press tool assembly provided with a wedge cam mechanism according to one embodiment of the present invention.
[23] FIG. 2 is a front sectional view of a riveting press tool assembly provided with a wedge cam mechanism according to one embodiment of the present invention, when the riveting die is in upward stroke condition.
[24] FIG. 3 shows a top plan view and sectional side view of a wedge cam mechanism in a riveting press tool assembly according to one embodiment of the present invention.
[25] FIG. 4 shows a side sectional view and top plan view of a retainer plate in a wedge cam mechanism in a riveting press tool assembly according to one embodiment of the present invention.
[26] FIG. 5 shows a side sectional view and top plan view of a guide block in a wedge cam mechanism in a riveting press tool assembly according to one embodiment of the present invention.
[27] FIG. 6 is a side sectional view of a wedge cam mechanism in a press tool assembly according to one embodiment of the present invention.

[28] FIG. 7 is a front sectional view of riveting press tool assembly provided with a wedge cam mechanism according to one embodiment of the present invention.
Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[30] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[31] The various embodiments of the present invention provide a cam assembly for riveting magnets in a press tool assembly to control the bulging of the magnets during the riveting operation. The assembly avoids the sideways movement of a locating block of the riveting die due to the bulging of electromagnets to prevent the deflection and breakage of Guide pins.
[32] According to one embodiment of the present invention, a wedge cam assembly for riveting magnets in a press tool assembly has a cam mechanism provided in a top half of the press tool. A retainer plate is arranged above the cam mechanism. A spring is mounted above the retainer plate. A guide block is fixed to the top plate in the press tool. A guide slot is provided in the guide block. Atleast one locating block is arranged below the guide block. The cam mechanism and the

[33] locating block has tapered profile so that the cam mechanism is engaged with the locating block to arrest the movement of the locating block, when the top half is moved downwardly.
[33] The cam mechanism has a taper surface at the bottom. The locating block has a slot to receive the cam mechanism during the downward movement of the top half. The slot on the locating block has a tapered surface on the top side. The tapered profile on the cam mechanism and the tapered profile on the locating block are identical. The tapered profile on the cam mechanism and the tapered profile on the locating block are identical. The taper angle in the cam mechanism and the taper angle in the slot are identical.
[34] The locating blocks are provided in the right hand side and in the left hand side of an ejector block holding the laminated stack of the magnet assembly. The locating blocks are moved to hold the laminated stack of magnet assembly in position during the riveting operation.
[35] The tapered surface of the cam mechanism is received in the tapered slot of the locating block to make the cam mechanism to engage with the locating block to exert a wedge effect on the locating block to prevent the movement of the locating block to control the bulging of the magnet assembly during the riveting operation, when the top half is moved downwardly. The cam mechanism is moved through the guide slot in the guide block during the downward movement of the top half.
The cam mechanism has a height such that the tapered surface of the cam mechanism engages with the tapered slot on the locating block only after the movement of the locating block to hold the laminated stack of magnet assembly but before the starting of the riveting process.
[36] The guide block has a slot to guide and move the cam mechanism in vertical direction. The guide block is fixed to the bottom surface of the top plate through a fastener. The guide block is fixed to the bottom surface of the top plate

[37] through Allen screws. The guide block is fixed to the bottom surface of the top plate through dowel pins. The guide block has a slot to accommodate the retainer plate of the cam mechanism.
[37] The retainer plate has a size which is greater than the size of the cam mechanism to retain the cam mechanism within the guide block. The spring rests on the retainer plate. The spring is accommodated in a top plate provided in the top half of the press tool sothat any extra movement of the top half of the press tool pushes the cam mechanism up and the upward movement of the cam is allowed by the deflection of the spring.
[38] According to one embodiment of the present invention, a cam is retained in top half of the riveting die. The cam is guided through a guide block which is fixed to top plate of the riveting die The Cam is provided with a taper surface at the bottom on left hand side of the cam. Further the cam is provided with a retainer plate and a light spring which are mounted above the cam.
The moving part of guiding arrangement on right hand side of the riveting die has a locator slot with taper surface on left side of the locator slot. Taper angle in the locator slot is identical to that of taper in the cam. During the downward movement of the top half of the riveting die, the tapered surface on the cam engages with the tapered surface on the right hand side of the locating block. The taper locking between the tapered cam and the tapered locating block exerts a wedge effect on the locating block. Further, the wedge effect on the locating block prevents the locating block from shifting on right side due to bulging effect of the electromagnets during riveting operation. Thus the wedge effect controls the bulging in electromagnet during riveting operation. Once the cam gets engaged with the locating block extra downward movement of the cam is compensated by deflection of springs provided in the cam and the cam is pushed upwards.
[40] FIG. 1 illustrates s a top side plan view of a bottom half in a riveting press tool assembly provided with a wedge cam mechanism according to one embodiment

[41] of the present invention. With respect to FIG. 1, the riveting press tool is provided with guide pin holes 101, a stack lamination slot 102 and a locating block with a tapered slot 103. During the riveting process of the electromagnets, the guide pins are received through the guide pin holes 101. The laminated stack of silicon sheets inserted with rivet is placed within the stack lamination slot 102. The tapered slot 103 receives a tapered cam during the downward stroke movement of the riveting die. The taper angle of the tapered slot 103 is identical to that of a taper angle in the cam.
[41] FIG. 2 is a front sectional view of a riveting press tool assembly provided with a wedge cam mechanism according to one embodiment of the present invention, when the riveting die is in upward stroke condition.
With respect to FIG.2, the riveting die includes two halves, namely fixed bottom half and a moving top half. The various elements of the moving top half of the riveting die include a top plate 201, a cam 202, a guide block 203 and a riveting punch holder 204. The various elements of the fixed bottom half include a locating block 205, an ejector 206 and a stacked assembly of silicon sheet 207 that is placed on the ejector 206. The guide block 203 is fixed to the bottom surface of the top plate 201 with the help of screws and dowel pins. The locating block 205 is provided with a tapered surface 208 at the left hand side of a guide slot in the locating block 205 at the right side. The cam 202 is guided through the guide block 203 which is fixed to the top plate 201 of the riveting die. The Cam 202 is provided with a taper surface 209 on the left hand side at the bottom. Further the cam 202 is provided with a retainer plate 210 and a spring 211. The retainer plate 210 and the spring 211 are mounted above the cam 202. The tapered angle on the cam 202 is identical to tapered angle of the slot in the locating block 205 provided at right hand side of the fixed bottom half of the riveting die.
[42] The height of the cam 202 is designed such that the tapered surface 209 of the cam 202 gets engaged with the tapered surface 208 on right hand side of the locating block before the start of the riveting process. The guide block 203 is provided with a slot to guide the movement of the cam 202 in vertical direction

[43] during the riveting process. The slot in the guide block 203 accommodates the retainer plate 210 of the cam 202 during the riveting process. The retainer plate 210 is a rectangular plate fixed to the cam 202 using screws. The size of the retainer plate 210 is comparatively bigger than that of the cam 202 to retain the cam 202 within the guide block 203. The spring 211 of the cam 211 is accommodated in the top plate 201 and rests on the retainer plate 210 at a pre-compressed state.
[43] FIG. 3 shows a top plan view and sectional side view of a wedge cam mechanism in a riveting press tool assembly according to one embodiment of the present invention. With respect to FIG 3, the cam 202 is provided with a taper surface 209 on left hand side of the bottom part. The tapered angle on the cam 202 is identical to the tapered angle of the slot in the locating block provided at the right hand side of the fixed bottom half of the riveting die. The height of the cam 202 is designed such that the tapered surface 209 of the cam 202 gets engaged with the tapered surface on right hand side of the locating block before the start of the riveting process. The cam has a top planar surface 301 which is fastened to a retainer plate through the screws.
[44] FIG. 4 shows a side sectional view and top plan view of a retainer plate in a wedge cam mechanism in a riveting press tool assembly according to one embodiment of the present invention. With respect to FIG. 4, the retainer plate 210 is a rectangular plate fixed to the cam of the riveting die using screws. The size of the retainer plate 210 is comparatively bigger than the cam size to retain the cam within guide block of the riveting die. The retainer plate 210 is accommodated in a slot provided in the guide block.
[45] FIG. 5 shows a side sectional view and top plan view of a guide block in a wedge cam mechanism in a riveting press tool assembly according to one embodiment of the present invention. With respect to FIG. 5, the guide block 203 is provided with a slot 502 to guide the cam movement in vertical direction during riveting process. The slot 502 in the guide block 203 accommodates retainer plate of the cam during the riveting process. The retainer plate with a size bigger than the size

[46] of the cam is used to retain the cam within the guide block 203. The retainer plate is fixed to the cam mechanism through dowel pins and screws. The guide block is attached to the bottom surface of the top plate in the riveting press tool die using the Allen screws.
[46] FIG. 6 is a side sectional view of a wedge cam mechanism in a press tool assembly according to one embodiment of the present invention. With respect to Fig. 6, the guide block 203 is fixed to bottom of top plate 201 of the riveting press tool die using Allen screw 601 and dowel pin 602. The Allen screw 601 clamps the guide block 203 to the top plate 201. The Dowel pin 402 locates the guide block 203 with respect to the top plate 201. Further the Dowel pin 402 ensures alignment of cam 202 with respect to fixed bottom half of the riveting die. A cam mechanism 202 is guided through a slot in the guide block 203. The guide blocks helps to move the cam mechanism along the vertical direction. A retainer plate is fixed to the top surface of the cam mechanism. A spring is mounted above the retainer plate.
[47] FIG. 7 is a front sectional view of riveting press tool assembly provided with a wedge cam mechanism according to one embodiment of the present invention. With respect to FIG. 1, the moving top half of the riveting die is moved downwards towards fixed bottom half of the riveting die during the riveting process. Cam 202 of the riveting die is guided through a guide block 203 which is fixed to top plate 201 of the riveting die The Cam 202 is provided with a taper surface on the left hand side of the bottom portion. Further the cam 202 is provided with a retainer plate 210 and a spring 211 which are mounted above the cam 202. The tapered surface on the cam 202 engages with the tapered surface on the right hand side of locating block 205. Taper locking between the tapered surface of the cam 202 and the tapered surface of the locating block 205 exerts a wedge effect on the locating block 205.
[48] The spring 211 of the cam 202 attains compressed state due to the taper locking between the tapered surface of the cam 202 and the tapered surface of the locating block 205.Thus the wedge effect on the locating block 205 prevents the locating block 205 on the right side from shifting due to the bulging effect of the

electromagnets during the riveting operation. The wedge effect on the locating block 205 controls the bulging of the electromagnet during riveting operation. Once the cam 202 gets engaged with the locating block 205, the extra downward movement of the cam 202 is compensated by the deflection of the springs 211 provided in the cam 202 and as a result the cam 202 is pushed upwards. Stack assembly, which contains the laminated magnetic sheets 207 inserted with a rivet and placed on the ejector block 206, is punched with a riveting punch holder 204 resulting in upsetting the loose ends of the inserted rivets into a rivet head to form riveted electromagnet assembly 207. G) ADVANTAGES OF THE INVENTION
[49] Thus the various embodiments of the present invention provide a wedge cam assembly for magnets in riveting press die to control the bulging of the magnets during riveting operation. The assembly avoids the sideways movement of a locating block of the riveting die due to the bulging of the electromagnets to prevent the deflection and the breakage of the guide pins provided in the riveting die. The assembly avoids the downtime caused in the riveting die due to the uncontrolled bulging action of the electromagnets during the riveting operation.
[50] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[51] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be
said to fall there between.
Date: October 26, 2009 Place: Bangalore.



CLAIMS
What is claimed is:
1. A wedge cam assembly for riveting magnets in a press tool assembly comprising:
A cam mechanism provided in a top half of the press tool; A retainer plate arranged above the cam mechanism; A spring mounted above the retainer plate; A guide block fixed to the top plate in the press tool; A guide slot provided in the guide block; and A locating block arranged below the guide block;
Wherein the cam mechanism and the locating block has tapered profile so that the cam mechanism is engaged with the locating block to arrest the movement of the locating block, when the top half is moved downwardly.
2. The assembly according to claim 1, wherein the cam mechanism has a taper surface at the bottom.
3. The assembly according to claim 1, wherein the locating block has a slot to receive the cam mechanism during the downward movement of the top half.
4. The assembly according to claim 1, wherein the slot on the locating block has a tapered surface on the top side.
5. The assembly according to claim 1, wherein the tapered profile on the cam mechanism and the tapered profile on the locating block are identical.
6. The assembly according to claim 1, wherein the tapered profile on the cam mechanism and the tapered profile on the locating block are identical.
7. The assembly according to claim 1, wherein the taper angle in the cam mechanism and the taper angle in the slot are identical.

8. The assembly according to claim 1, wherein the locating block are provided in the right hand side and in the left hand side of an ejector block holding the laminated stack of the magnet assembly.
9. The assembly according to claim 1, wherein the locating blocks are moved to hold the laminated stack of magnet assembly in position during the riveting operation.
10. The assembly according to claim 1, wherein the tapered surface of the cam mechanism is received in the tapered slot of the locating block to make the cam mechanism to engage with the locating block to exert a wedge effect on the locating block to prevent the movement of the locating block to control the bulging of the magnet assembly during the riveting operation, when the top half is moved downwardly.
11. The assembly according to claim 1, wherein the cam mechanism is moved through the guide slot in the guide block during the downward movement of the top half.
12. The assembly according to claim 1, wherein the cam mechanism has a height such that the tapered surface of the cam mechanism engages with the tapered slot on the locating block only after the movement of the locating block to hold the laminated stack of magnet assembly but before the starting of the riveting process.
13. The assembly according to claim 1, wherein the guide block has a slot to guide and move the cam mechanism in vertical direction.
14. The assembly according to claim 1, wherein the guide block is fixed to the bottom surface of the top plate through a fastener.
15. The assembly according to claim 1, wherein the guide block is fixed to the bottom surface of the top plate through Allen screws.

16. The assembly according to claim 1, wherein the guide block is fixed to the bottom surface of the top plate through dowel pins.
17. The assembly according to claim 1, wherein the guide block has a slot to accommodate the retainer plate of the cam mechanism.
18. The assembly according to claim 1, wherein the retainer plate has a size which is greater than the size of the cam mechanism to retain the cam mechanism within the guide block.
19. The assembly according to claim 1, wherein the spring rests on the retainer plate.
20. The assembly according to claim 1, wherein the spring is accommodated in a top plate provided in the top half of the press tool sothat any extra movement of the top half of the press tool pushes the cam mechanism up and the upward movement of the cam is allowed by the deflection of the spring.