Title of Invention

A DEVICE MOUNTED ON DOUBLE ACTING PRESS FOR TRIPLE ACTION RIVETING OF STEEL LAMINATIONS

Abstract

A device for riveting steel laminations and adapted to provide third degree of motion, the riveting device comprising plurality of plates (1,2,3 and 8), means (C1) mounted on the said plates and adapted for providing third degree of motion, means (6) adapted for holding together the lamination stack (13) to be riveted, means (4 and 5) adapted for squaring the lamination stack (13) to be riveted, means (C2 and 4) adapted for pressing the lamination stack (13) rested on the block (5) provided in the device and means (9 and 10) adapted for compensating the variation in defined length of the rivet and operatively connected to said plurality of plates.

Full Text

F0RM2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10; rule 13) 1. Title of the invention. - DEVICE FOR TRIPLE ACTION REVETING 2. Applicant(s) (a) NAME : (b) NATIONALITY: (c) ADDRESS : LARSEN & TOUBRO LIMITED An Indian Company. 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 INVENTION The present invention relates to a device for riveting steel magnet plates (or laminations). More particularly, it relates to a device adapted for riveting steel magnet laminations accurately for one side headed rivets wherein the riveting device provides third degree of motion producing triple action riveting. The present device comprises an arrangement for compensating the variation between the actual rivet length and the nominal length. BACKGROUND ART In electrical industry the electro magnets are important parts of electrical appliances, efficiency of which depends upon the efficiency of magnets. In riveting process the laminations are stacked together and the rivets are inserted in the pre-pierced holes in the laminations. The riveting process has two objectives; holding the laminations properly and tightly and retaining the perpendicularity of the faces of the magnet. In case of conventional riveting operation, there are two sources of motion. Due to this, there are inherent problems in the riveting tools and also the quality of riveted magnets is not good. This is because of the inconsistency in the lengths of rivets etc. Another disadvantage with the existing riveting device is that due to variation in lengths of the rivets the quality of the magnet is affected. If the length of the rivet is more than the nominal length, the extra material in the rivet leads to the deformation of magnets and if the rivet length is smaller than the nominal length, improper holding of the laminations occurred. These problems result in the following drawbacks in the magnet assembly: The improper stacking and holding of the laminations adversely affects the efficiency of the magnets. This is because the laminations in the magnet become loose causing a lower "stacking factor" (Stacking Factor is the ratio of minimum height of the magnet having certain number of laminations to the height of the magnet having same number of the laminations). Lower stacking factor results in higher hysteresis losses and during the 2 course of life of the magnet mushrooming takes place which results in reduced life of the magnet. Proper stacking and holding ensures a higher stacking factor for the magnet and thus improves life and lower looses. The other disadvantage lies in maintaining the perpendicularity of the faces of the magnet stacks i.e. squaring (Squaring is a process of maintaining lamination stack faces perpendicular to the lamination surface). Squaring is important since it defines the face of the magnet, which actually touches the other magnet. To achieve proper squaring, the process followed after conventional riveting is grinding. This involves higher cost per magnet assembly. Thus conventional riveting tool has problems in producing high quality magnets. The other method of getting good quality magnets is by using a specially made tool on triple action press. Of the various devices used in the industry today for magnet riveting, one of the most reliable methods for riveting is using the riveting tool on a triple action press. The press has three independent modes of generating the motion. The first one is used to clamp the loose laminations properly, the second one is used to hold the topside head of the rivets and the third one is used to form the bottom side head of the rivets. Basically, three independent sources of motion are required to take care of the varying rivet lengths. The triple action press due to its inherent capability in giving three independent motions providing a better quality of riveted magnets. The disadvantages associated with the triple action presses are as follows - The triple action press is extremely costly and requires a high amount of initial investment to buy a triple action press. Another disadvantage is that the tool designed to run on a triple action press cannot be used on a conventional press. So, the riveting tool made for a triple action press becomes a dedicated tool. 3 Thus there is a need to provide for a riveting device giving advantage of triple action riveting on conventional hydraulic press and for accurate riveting of laminations of steel magnet, adapting third degree of motion producing triple action riveting and compensating the variation between the actual rivet length and the nominal length. OBJECTS OF INVENTION The basic object of the present invention is to provide triple action riveting by a conventional hydraulic press. Another object is to provide high quality riveting by compensating for the variation in rivet length. Further object of the present invention is to provide high staking factor and thus minimizing hysteresis losses in the lamination stack. SUMMARY OF INVENTION Thus according to the basic aspect of the present invention, there is provided a device for riveting steel laminations and adapted to provide third degree of motion, the riveting device comprising: (i) plurality of plates; (ii) means mounted on the said plates and adapted for providing third degree of motion; (iii) means adapted for holding together the lamination stack to be riveted; (iv) means adapted for squaring the lamination stack to be riveted; (v) means adapted for pressing the lamination stack rested on the block provided in the device and; (vi) means adapted for compensating the variation in defined length of the rivet and operatively connected to said plurality of plates. 4 DETAILED DESCRIPTION OF INVENTION The device of the present invention is mounted on double acting (conventional hydraulic) press comprising top ram and bottom buffer. The said device comprises plurality of plates viz. the top plate, middle plate and the bottom plate. The means mounted between the said top and the middle plate comprises four cylinders adapted for providing third degree of motion in the riveting device and forming gap between the auxiliary plate and means adapted for compensating for variation in length of the rivet. The means adapted for compensating for variation in length of the rivet comprises floating punches adapted to assume differential position with respect to length of the rivet The floating punches are held in the holder plate provided below the auxiliary plate. The means adapted for pressing the lamination stack comprises slide, which is provided on the resting block in the device and this slide along with the said resting block is adapted for squaring the stack of the laminations, which are to be riveted. The means adapted for holding the lamination stack comprises of the ejector block, which is floating in the device. One side headed rivets are inserted & crimped in the said stack of laminations. This is mounted on the floating ejector block. The auxiliary plate provided in the device adapted for driving the top floating punches is connected to the top plate by a screw, the screw being fixed to the said plate such that the motion of the top plate is transmitted to the auxiliary plate adapted for driving the floating punches. Thus the auxiliary plate is operatively connected to the top plate, which in turn is connected to the top ram of the double acting press or the conventional hydraulic press by screws. The floating punches adapted for assuming differential lengths with respect to the nominal rivet length are fitted in the holder plate. The fitment of the floating punch with the said holder plate is so provided that if the rivet length is more than the nominal length, the floating punch assumes the topmost position. The gaps between the topside head of the rivets and the stack of the laminations are so provided that the increased length of the rivet does not affect the clamping of the magnet lamination in any way. The 5 floating punch moves to the top position to absorb the increased length of the rivet. So, the riveting operation does not begin till the laminations are properly clamped. The laminations being properly clamped, the auxiliary plate is adapted for pushing the floating punches giving proper riveting effect. In case the rivets are shorter in length than the nominal length, the floating punches are provided so as to assert no load on the rivets till the clamping is properly done. The auxiliary plate then pushes the floating punches to give proper riveting. The third degree of motion developed in the device by the cylinders takes care of the both lesser or more rivet length. Working of the invention- One side headed rivets are inserted & crimped in the said stack of laminations. This is mounted on the floating ejector block. For riveting using the device of the present invention the said lamination stack is squared and the set of cylinders between the top and middle plates are actuated i.e. opened, thereby causing a gap to be formed between the auxiliary plate and the floating punch. At this stage of operation no force acts on the floating punches from the topside. Next the top ram is actuated and the top plate, middle plate and the punch come down as a single unit. Hence, the lamination stack is gripped between the punch and the ejector block. The movement of the top half of the device initiates the forming process of the topside head of the rivets. At this time there is a gap between the topside of the rivets and the stack of the laminations. This gap is basically for compensating the inaccuracies in the lengths of the rivets. After this, the top ram is moved down further and simultaneously the set of four cylinders are actuated i.e. closed. This causes the gap between the topside head of the rivets and the stacks to close up. The further bulging of the topside head of the rivets closes the 6 gap. The force that causes this is the force acting from the top ram of the press and thus proper riveting is ensured. Then the top ram is moved up and simultaneously the four cylinders are opened. The bottom buffer is brought up and cylinder is retracted. The magnet is thus ejected. BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES Figure 1 illustrates the schematic view of the triple action riveting device of the present invention. Figure 2 illustrates enlarge schematic view of the lamination stack alongwith the ejector block in the riveting device of the present invention. Figure 3 to figure 6 illustrate different working stages of the triple action riveting device of the present invention. DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURES In figure 1 the schematic view of the triple action riveting device of the present invention is illustrated. In the figure the top plate (1) is connected to the top ram (14) by the screw (11). The device comprises of the middle plate (2) and the bottom plate (3). The screw (11) passes through the top plate (1) and the middle plate (2) and is attached to the auxiliary plate (8). The head of the screw (11) is in mechanical conjunction with the top ram (14) and is adapted to move the auxiliary plate (8) with the movement of the top ram (14). Four cylinders (C1) are mounted between the top plate (1) and the middle plate (2) and is adapted for third degree of motion. The lamination stack (13) is mounted on the floating ejector block (6) (enlarge view provided in figure 2). The one side headed rivets (15) are inserted and crimped into the stack of lamination (13). The lamination stack (13) is gripped between the ejector block (6) and the punch (7), which is held in the holder plate (12). The said holder plate (12) also holds the floating punches (9 and 10), which are adapted for absorbing the variation in length of the rivet (15). The slide (4) along with the resting block (5) is adapted for squaring the lamination stack (13). 7 In figures 3 to 6 different working stages of the triple action riveting device of the present invention are illustrated. The double acting (conventional hydraulic) press comprises the top ram (14) and bottom buffer. The device of the present invention is mounted on the press and is mechanically connected to the top ram (14) by the screw (11). As illustrated in figure 3 the top ram (14) and the bottom buffer is at its topmost position when the lamination stack (13) is mounted on the ejector block (6). The cylinders (C1) are in the closed state and adapted for keeping the auxiliary plate (8) in the topmost position. Cylinder (C2) is adapted for actuation of movement of slide (4) and thereby pressing the lamination stack (13) on the resting block (5) giving squaring to the lamination stack (13). As shown in figure 4, actuation of cylinder (C1) is adapted for forming the gap (16) between the auxiliary plate (8) and floating punches (9 and 10). As shown in figure 5 top ram (14) and screw (11) is adapted for moving the top plate (1), middle plate (2) and punch (7) as a single unit, hence tightly gripping the lamination stack (13) between the punch (7) and the ejector block (6). In figure 6 further downward movement of the top ram (14) is adapted for minimizing the gap between the rivet head and the lamination stack (13). 8 WE CLAIM 1. A device for riveting steel laminations and adapted to provide third degree of motion, the riveting device comprising: (i) plurality of plates; (ii) means mounted on the said plates and adapted for providing third degree of motion; (iii) means adapted for holding together the lamination stack to be riveted; (iv) means adapted for squaring the lamination stack to be riveted; (v) means adapted for pressing the lamination stack rested on the block provided in the device and; (vi) means adapted for compensating the variation in defined length of the rivet and operatively connected to said plurality of plates. 2. A device as claimed in claim 1, wherein the means adapted for compensating the variation in defined length of the rivet comprises floating punch adapted to assume differential position with respect to length of the rivet. 3. A device as claimed in claims 1 and 2, wherein the floating punch is adapted for forming head of the rivet such that it bulges to minimize the gap between the head and the lamination stack. 4. A device as claimed in claim 1, wherein the plurality of plates comprises top plate, middle plate, bottom plate, auxiliary plate and holder plate. 5. A device as claimed in claim 4, wherein the auxiliary plate is connected to the top plate by a screw, the screw being fixed to the said plates such that the motion of the top plate is transmitted to the auxiliary plate adapted for driving the floating punches. 9 6. A device as claimed in claim 1, wherein the means for holding the lamination stack adapted for proper clamping and gripping comprises floating ejector block and punch. 7. A device as claimed in claim 1, wherein the pressing means comprises cylinder actuated slide adapted for pressing the lamination stack and providing squaring to the stack. 8. A device as claimed in any of the preceding claims, wherein the means adapted for providing third degree of motion comprises four cylinders mounted in between the top and middle plates adapted to form gap between the auxiliary plate and the floating punch thus producing no load on the floating punch. 9. A device as claimed in any one of the preceding claims adapted for triple action riveting on conventional hydraulic press. 10. A device for riveting substantially as herein described and illustrated with reference to the accompanying figures. Dated this 29th day of April, 2005. Dr. Sanchita Ganguli of S. Majumdar & Co. Applicant's agent 10 ABSTRACT Title: Device For Triple Action Riveting A device for riveting steel laminations and adapted to provide third degree of motion, the riveting device comprising plurality of plates (1, 2, 3 and 8), means (C1) mounted on the said plates and adapted for providing third degree of motion, means (6) adapted for holding together the lamination stack (13) to be riveted, means (4 and 5) adapted for squaring the lamination stack (13) to be riveted, means (C2 and 4) adapted for pressing the lamination stack (13) rested on the block (5) provided in the device and means (9 and 10) adapted for compensating the variation in defined length of the rivet and operatively connected to said plurality of plates. Figure 1

Documents:

536-mum-2005-abstract.doc

536-mum-2005-abstract.pdf

536-mum-2005-claim.doc

536-MUM-2005-CLAIMS(AMENDED)-(10-5-2012).pdf

536-MUM-2005-CLAIMS(AMENDED)-(13-10-2014).pdf

536-MUM-2005-CLAIMS(MARKED COPY)-(13-10-2014).pdf

536-mum-2005-claims.pdf

536-MUM-2005-CORRESPONDENCE(11-9-2013).pdf

536-MUM-2005-CORRESPONDENCE(14-7-2014).pdf

536-MUM-2005-CORRESPONDENCE(20-7-2012).pdf

536-MUM-2005-CORRESPONDENCE(23-12-2009).pdf

536-mum-2005-correspondence(23-4-2008).pdf

536-MUM-2005-CORRESPONDENCE(24-8-2012).pdf

536-MUM-2005-CORRESPONDENCE(25-8-2009).pdf

536-MUM-2005-CORRESPONDENCE(26-7-2010).pdf

536-MUM-2005-CORRESPONDENCE(6-5-2014).pdf

536-MUM-2005-CORRESPONDENCE(8-5-2009).pdf

536-MUM-2005-CORRESPONDENCE(9-4-2013).pdf

536-mum-2005-correspondence-received-ver-290405.pdf

536-mum-2005-correspondence-received-ver-300605.pdf

536-mum-2005-description (complete).pdf

536-mum-2005-drawings.pdf

536-MUM-2005-FORM 1(13-10-2014).pdf

536-mum-2005-form 1(8-7-2005).pdf

536-mum-2005-form 18(17-9-2007).pdf

536-MUM-2005-FORM 2(TITLE PAGE)-(13-10-2014).pdf

536-mum-2005-form 2(title page)-(2-5-2005).pdf

536-mum-2005-form-1.pdf

536-mum-2005-form-2.doc

536-mum-2005-form-2.pdf

536-mum-2005-form-26.pdf

536-mum-2005-form-3.pdf

536-MUM-2005-GENERAL POWER OF ATTORNEY(13-10-2014).pdf

536-MUM-2005-REPLY TO EXAMINATION REPORT(10-5-2012).pdf

536-MUM-2005-REPLY TO EXAMINATION REPORT(22-7-2010).pdf

536-MUM-2005-REPLY TO HEARING(13-10-2014).pdf

536-MUM-2005-SPECIFICATION(AMENDED)-(10-5-2012).pdf

536-MUM-2005-SPECIFICATION(MARKED COPY)-(10-5-2012).pdf

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