F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN IMPROVED RIVETING PRESS TOOL ASSEMBLY

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE NVENTION

The present invention relates to a riveting press tool assembly. More particularly, the invention is concerned about an improved riveting press tool assembly having a unique profile of stopper pins for avoiding distortion of magnet in riveting tools.

BACKGROUND OF THE INVENTION

Press tool mainly consists of two halves, namely fixed bottom half and a moving top half as shown in figure 1. The fixed bottom half is secured to the stationary bolster plate of hydraulic press. It comprises arrangement for location of stack of laminations, sizing the stack, arrangement to remove the magnet assembly after riveting, guide pillars for alignment of both halves etc. The location arrangement for lamination stack consists of two halves – viz. a moving half on the left side of operator & a moving half on the right side. Both the moving halves are actuated by pneumatic cylinders. The top moving half is clamped to the moving ram of the hydraulic press and it comprises a number of round riveting punches housed in a block clamped to the top bolster. The block moves up and down along with the moving ram of the hydraulic press. The slide on the left has a pair of horizontal ejector pins hidden inside when it is in forward condition.

At the beginning, the left moving half of locating arrangement moves in and the stack of laminations (with rivets flared at both ends after insertion in the stack) is kept on the ejector block and located against the locator. During downward stroke, the moving locating parts on right and left hand side are engaged by Guide pins from the top half, the block clamps the stack & pushes it down against a floating block called ejector. The registration of the locating blocks by guide pins from top creates a finite gap in the location arrangement for the lamination stack. The ejector block has a number of stationary round punches guided in it and held in a plate called punch holder. During downward movement of ejector, there is a relative movement between the stationary round punches and the ejector block which results in upsetting the loose ends of rivets into a rivet head.

As the top half moves up, the riveted stack moves up with the floating ejector. The locating moving half on the right side moves away from the riveted stack and mostly causes bulging of component due to holding pressure applied at top and surface of component because of which stack clings to the locator on the sides. As the slide moves out, the stationary ejector pins hidden inside are exposed & strip the stuck magnet from the locator slides. Thus, the stack is retained on ejector block instead of getting dragged with the slide. It is removed manually. However, many times the free stack does not remain on ejector block but it gets toppled during stripping action due to jerk of ejector pins and gets damaged. The pins also leave a mark on magnet due to stripping action as shown in figure 2.

Press tools for production of Electromagnets by riveting operation. The electromagnets are made by a process of joining a stack of stampings made of silicon steel sheet by riveting process. The laminations are stacked & rivets are inserted in the holes in laminations. The rivets have formed heads at the top & loose ends are upset to form the rivet heads on other side of the stack.

US 6654997 B2 (A) discloses a rivet removal tool and method. This invention is generally related to tool and method for removing rivet after it has been installed and more specifically related to rivet removal tool and method which eliminates, at least substantially reduces, the end load must applied to drill out a button and remove a rivet.

US 4918798 (A) discloses a tool and machine for removing fastener from work piece. Tool includes two piece housing with shaft slid ably position therein. The upper part of housing slides relative to lower part and serves to support to shaft as it is urged into fastener to dislodge it from work piece.

The disadvantages of the prior art are such as that ejector pins used in the prior art are relatively longer and have constraint of placement for construction is not suitable for quick assembly since it passes through cylinder clamping plate and slide. Due to more length, there are chances of buckling and breakage of pins. It is also required PU rod to avoid mark on component. As riveting cycle completed, moving half on the right side moves away from the riveted stack and mostly causes bulging of component due to holding pressure applied at top and surface of component because of which stack clings to the locator on the sides. As the slide moves out, the stationary ejector pins hidden inside are exposed & strip the stuck magnet from the locator slides. Thus, the stack is retained on ejector block instead of getting dragged with the slide. It is removed manually. However, many times the free stack does not remain on ejector block but it gets toppled during stripping action due to jerk of ejector pins & gets damaged. The pins also leave a mark on magnet due to stripping action.

Thus, there is a need to overcome the problems of the prior art. Therefore, present inventors have developed an improved riveting press tool assembly having a unique profile of stopper pins for avoiding distortion of magnet in riveting tools and retentions of component or magnet with sturdy, rigid and simplified construction for ejection in riveting tools and would retain position of stack with the use of stopper pins profile.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the problems/disadvantages of the prior art.

Another object of the present invention is to provide an improved riveting press tool assembly having a unique profile of stopper pins for avoiding distortion of magnet in riveting tools.

These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved riveting press tool assembly comprising:
holder plate means;
stack means;
stopper pin means;
wherein said stopper pin means, having a predetermined height, being operatively arranged on said holder plate means and height of said stopper pin means being operatively kept more than a predetermined height of said stack means so as to retain position of a conventional magnet in the assembly and not allowing movement of said stack means with a conventional slide means.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Figure 1 illustrates a sectional view of riveting press tool assembly
Figure 2 illustrates a sectional view of riveting press tool assembly of another prior art document.
Figure 3 illustrates a sectional view of an improved riveting press tool assembly
Figure 4 illustrates a stopper pin profile.
Figure 5 illustrates a schematic diagram of working of an improved press tool assembly.
Figure 6 illustrates another sectional view of an improved riveting press tool assembly

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the assembly of the components has been discussed below to describe the way the assembly operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

According to the invention there is provided an improved riveting press tool assembly having a unique profile of stopper pins (1) for avoiding distortion of magnet in riveting tools. The ejector pins are retained in the Bottom half in of the Riveting tool. They are fixed in against a spacer in a Cylinder holding block which is fixed to the base plate. As shown in figure 3 and figure 6, a unique stopper pins profile (1) (item no.48 as shown in figure 3) are fixed vertically in holder plate (2) (item no.46 as shown in figure 3) which is bolted to base plate and height of stopper pin means (1) kept more than stack (3) height to retain position of magnet and not to allow movement of stack (3) with slide (item no.71 as shown in figure 3). As shown in figure 4, the height of the stopper pin (1) should be such that it should restrict stack (3) to retain its original position.

Figure 5 shows the schematic diagram of working of the invention. When riveting cycle is over and slides moves away from ejector block as explained above, the stack (3) sticking to slide due to bulging is prevented from moving away with slide due to the barrier created by the stopper pins (1). Since the rigid vertical pins cover full height of stack (3), toppling of magnet is avoided. This avoids damage to the magnet. Ejector pin marks are also avoided.

ADVANTAGES OF THE INVENTION

1. Easy to replace and manufacture.
2. Simple in construction.

Constructional elements:
Stopper pin 1
Holder plate 2
Stack 3

WE CLAIM:

1. An improved riveting press tool assembly comprising:
holder plate means;
stack means;
stopper pin means;
wherein said stopper pin means, having a predetermined height, being operatively arranged on said holder plate means and height of said stopper pin means being operatively kept more than a predetermined height of said stack means so as to retain position of a conventional magnet in the assembly and not allowing movement of said stack means with a conventional slide means.

2. Assembly as claimed in claim 1, wherein said stopper pin means being positioned substantially vertically along an axis.

3. Assembly as claimed in claims 1 or 2, wherein said stopper pin means being positioned proximate to said stack means.

4. Assembly as claimed in any of preceding claims, wherein said stopper pin means being positioned substantially parallel to said stack means.

5. Assembly as claimed in claim 1, wherein said holder plate means being positioned substantially horizontally along an axis.

6. Assembly as claimed in claim 1, wherein said stopper pin means being positioned substantially perpendicular to said holder plate means.

7. An improved riveting press tool assembly as herein substantially described and illustrated with the accompanying drawings.