Title of Invention

AN APPARATUS AND A PROCESS FOR MANUFACTURE OF WIDE WEB STATOR CORE BY ROLLING PROCESS

Abstract

This invention relates to an apparatus and a process for manufacture stator core circular in structure made from straight wide width steel strip having slots on one edge and shallow notches on the other edge by a process of rolling a portion of the strip between two geared tapered rollers. The rolling action progressively stretches the material that forms the outer diameter and as a result it gets curled. When the process is continued the strip takes the shape of a helical coil. After the desired number of turns the helical coil is formed it is cut off from the parent material. This helical coil is subsequently held on a mandrel and selded on shallow notches provided on the outer diameter. Further process i.e. burnishing, sizing, coining, turning, grinding etc. is carried out as required to complete the helically wound stator core.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See Section 10; rule 13) TITLE OF THE INVENTION An apparatus and a process for manufacture of wide web stator core by rolling process APPLICANTS SAMARENDRA NARAYAN SINHA, an Indian national having his address at Shed No.W-10 & 11, Block F-2, MIDC, Pimpri, Pune 411018 Maharashtra, India INVENTORS Samarendra Narayan Sinha, Subhash Sinha and Pravir Sinha, all Indian nationals having their address at Shed No.W-10 & 11, Block F-2, MIDC, Pimpri, Pune 411018 Maharashtra, India PREAMBLE TO THE DESCRIPTION The following Complete specification particularly describes the invention and the manner in which it is to be performed. FIELD OF INVENTION This invention relates to an apparatus and a process for manufacture stator core circular in structure made from straight wide width steel strip having slots on one edge and shallow notches on the other edge by a process of rolling a portion of the strip between two geared tapered rollers. BACKGROUND OF INVENTION Bulk of stator core is still made by stacking punched electrical steel/mild steel of required shape and size. For stator core having web width of about 4 mm represented by Wl Fig.l, process of edge winding is increasingly used. For wide width web ie. 10mm and above represented by W2 Fig. 2, no satisfactory process of edge winding exists. Attempts have been made to curl straight slotted strip by a process of striking the slotted strip by reciprocating wedge to elongate the edge forming the outer diameter. A process of rolling has also been attempted with elaborate arrangement dedicated to manufacture of stator core of one size and configuration only. Both the devices are accompanied by rotary disc and reciprocating fingers. This method has inherent shortcomings. (Refer to US Patent Nos. 4193281 dated 18th March 1980, US Patent No. 3283399 dated 8th November 1966 US Patent No. 4445353 dated 1st May 1980.) The patents mentioned above are not flexible enough to cater to a large variety and size. In addition they are not at all popular with the manufacturers of electrical stampings / stator and rotors. 2 OBJECT OF INVENTION The main objective of the present invention is to design an apparatus that is universal in application and can be adopted to manufacture a large range of stator core with minimum of adjustment and tooling. Another objective is to economize the use of expensive electrical grade steel/mild steel for building stator core and offer scope for using low cost steel to build up rotor core without in anyway compromising on the performance of the electrical machinery. SUMMARY OF INVENTION The present invention provides a simple apparatus to manufacture wide range and size of stator core by a process of rolling slotted strip of steel on one edge and shallow notches at less frequent intervals on the other edge. When two rollers are provided with small equal taper, and a selected portion of slotted steel strip represented by W3 (Fig 2, Fig 4 & Fig 5) is gripped and rolled, the slotted strip near the big end of the taper roller is progressively more elongated and consequently the slotted strip curls (See Fig 5). While rolling, the slotted strip has a tendency to creep towards the small end of the taper roller. To overcome this effect four Nos permanent magnets and 3 (Fig 7) four Nos hard material (Tungsten Carbide) 2 (Fig 7) are provided on the path of movement to hold the slotted strip on the edge in one plane. When tapered rollers are rotated through a predetermined angle the slotted strip moves forward and gets curled and at the same time the slotted strip creeps towards the small end of the tapered roller from its normal working position which results in a slight gap between the hard metal and the edge 3 of the slotted strip. This phenomenon is shown in Fig 8 with faint line numbered 22. As soon as the taper rollers are separated and the grip is released the slotted strip is pulled back by the permanent magnet to its normal working position. When this sequence of operation is repeated a helical coil is produced. As a result of rolling, the width of strip W2 refer Fig 2 marginally increases which is subsequently (after welding) corrected by turning / grinding. The taper on the rollers and the load exerted by the hydraulic cylinder determine the radius of curling. Once the appropriate load exerted by the hydraulic cylinder is determined the pressure of hydraulic oil is kept constant to produce consistent result. The method of maintaining constant pressure is explained in detail in the description of preferred embodiments. Emerging immediately after rolling between two tapered rollers the curled slotted steel strip is made to graze on a suitable radiused forming block to impart consistency to the outside diameter. In addition this curled slotted steel strip forms a helical coil and is made to pass through two inclined rollers to remove dishing during the process. The height of the pair of inclined rollers define the path followed by the helical coil which is directed on top of taper rollers and accumulated in a coil form. To impart stability to the system two ball ended adjustable screws are positioned along with path between the taper roller and the inclined roller. The entire unit comprising of radiused forming block, pair of inclined rollers and a pair of ball ended screw is held on an adjustable block capable of moving towards or away from the axis of taper rollers. Subsequently the helical slotted strip is held on a suitable fixture and welded longitudinally at several places to make a rigid structure. This structure is then subjected to operations i.e. sizing, burnishing, coining, turning, grinding etc. to make a stator core. 4 BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings as listed below. Throughout the figures like reference numerals designate identical or corresponding components. Fig 1. Represents straight narrow web strip of magnetic material as it comes out from Power Press after punching. Fig 2. Represents a straight wide web strip of magnetic material as it comes out of Power press after punching Fig 3. Represents interlocking method to economize material consumption Fig 4. Enlarged cross section of section on AA, fig 5 Fig 5. Represents partly curled wide web slotted strip Fig 6. Enlarged section on BB (Fig 5) Fig 7. Schematic elevation of the curling apparatus Fig 8. Schematic plan of the curling apparatus Fig 9. Elevation of Fig 10 Fig 10. Enlarged section AA (Fig 7) Fig 11. Plan view of Fig 9 Fig 12. Elevation of storage arrangement of curled helical coil located on top Fig 13. Plan view of fig 12 Fig 14. Sectional view of completed stator core with straight slots after welding Fig 15. Sectional view of completed stator core with skewed slots after welding Fig 16. Plan view of stator core after welding. Fig 17. Sectional elevation of welding fixture for manufacturing straight fluted stator core Fig 18. Plan view of Fig 17 5 Fig 19. Enlarged view of welding mandrel for manufacture of stator core with straight slots Fig 20. Plan view of Fig 19 Fig 21. Sectional view of mandrel for manufacture of stator core with skewed slots Fig 22. End view of Fig 21 Fig 23. Helical slotted strip showing trailing end after bending and trimming ready to be mounted on fixture (Fig 19) Fig 24 Perspective view of taper roller, radiused forming block, ball ended screws and pair of included straight roller along with curled slotted steel strip. DESCRIPTION OF PREFERRED EMBODIMENTS The present invention is applicable to curling a wide width slotted steel strip in a circular helical structure which is further processed to manufacture stator core for electrical machines. Fig 1 represents a narrow width web. Fig 2 represents a wide width web. The apparatus related to this invention is applicable for wide width web represented by Fig 2. Economizing use of raw material is an important need and Fig 3 indicates interlocking of the slotted strips to economize use of raw material. It will be quite apparent that at least two strips are to be manufactured simultaneously to economize raw material consumption. Henceforth, processing of only one slotted strip with related apparatus will be described to convey the salient feature of the invention. Figures 4, 5 & 6 represent a small portion of the strip which has been partly curled. Centre line 1 (Fig 5) is the centre line of the tapered roller forming part of the curling apparatus. The portion of the strip on the left hand side of the centre 6 line 1 has been rolled and thereby curled and the portion on the right hand side shows the straight slotted strip as it comes out of the press. Fig 6 is an enlarged section on BB and indicates that the strip has uniform thickness before rolling. Fig 4 is an enlarged view of the section on AA (Fig 5) which indicates that the thickness of material forming the outer diameter of the curled slotted strip has been progressively thinned by the action of rolling between two tapered rollers 4 & 5 (Fig 7). Fig 7 & 8 are schematic elevation and Plan of an apparatus to curl slotted strip by process of rolling. Basically the apparatus consists of two rollers 4 & 5 (Fig 7) having slight taper on one end as shown in fig 8 represented by two tapered straight lines 4a and 4b (Fig 8) and gears 7 on the other end. Roller 4 is mounted on a fixed housing 9 (Fig 7) whereas roller 5 is mounted on a housing 10 (Fig 7) which is hinged by a pin 6 shown in Fig 8. Since both the rollers 4 & 5 (Fig 7) are geared they will rotate in opposite direction and this condition is necessary for rolling. The horizontal distance between the hinge pin 6 and gear 7 (Fig 8) is about one sixth of the distance between the hinge pin and the face of the taper roller and therefore a vertical movement of less than 1 mm on the taper roller does not effect proper functioning of the gears. A single acting hydraulic cylinder 8 (Fig 7) is positioned under the housing 10 (Fig 7). When hydraulic oil is directed to port 21 (Fig 7) the slotted strip is gripped. To achieve consistent curling it is essential to hold the hydraulic oil pressure at a constant value which is determined by trial and error. To have constant pressure irrespective of temperature variation and viscosity of oil, a double acting hydraulic cylinder is used as a separate stand alone unit where the piston rod is loaded with dead weight. The space between the piston and piston rod gland packing is used to trap oil under pressure. By varying this dead weight the pressure of hydraulic oil in the cylinder is also varied. To load the piston of the hydraulic cylinder, a system of pulleys and wire ropes is used to minimize the actual dead weight required. The oil under pressure is used for gripping the slotted steel strip between 7 the two tapered rollers. Repeated gripping at constant pressure and release of the two tapered rollers uses up the trapped oil which is under constant pressure and it becomes necessary to stop the machine for a few seconds and charge the hydraulic cylinder with oil under higher pressure so as to lift the dead weight. Once adequate oil under pressure is accumulated in the cylinder the hydraulic pump delivering oil at a higher pressure to the cylinder is unloaded. As soon as the hydraulic pressure is released in cylinder 8 (Fig 7) the grip on the slotted strip is released and a small gap occurs between the rollers and the slotted steel strip. A bracket 16 (Fig 7) is mounted on base plate 12 (Fig 7). Four hard material (Tungsten Carbide) item 2 (Fig 7) and four permanent magnets item 3 (Fig 7) are held on the bracket 16 (Fig 7) along with 2 Nos. roller 18 (Fig 7 & 8) in a straight line so that the face of all the hard material are in one plane and that of permanent magnet slightly below that of hard material. The edge of the slotted steel strip thereby come in contact with the hard material and a small air gap is maintained between the magnet and the edge of the slotted steel strip. Two rollers item 18 (Fig 7) assure that only the edge come in contact with hard material 2 (Fig 7) and the plane of the slotted strip is held at right angles. While rolling, the slotted steel strip tends to creep towards the small end of the tapered rollers 4 & 5 (Fig 7 & 8). The phenomena of creeping is represented by a thin line item 22 (Fig 8) while rolling. The permissible distance of the creep "C" (Fig 8) determines the angle through which the tapered rollers can be rotated before releasing the grip on the slotted strip. Taper on the rollers and the permissible creep "C" (Fig 8) is exaggerated to convey the operation of the apparatus. 8 The following sequence of operation is followed to achieve the curling of slotted strip. 1. Grip the slotted steel strip between the two tapered rollers by directing hydraulic oil through port 21 (Fig 7). 2. Rotate the tapered rollers through a specified angle to curl the slotted steel strip. While the slotted strip is curled, it creeps towards the small end of the tapered rollers thereby resulting in a gap between the hard material (Tungsten Carbide) 2 (Fig 8) and the edge of the slotted steel strip 67 (Fig 8). 3. Hydraulic oil is now released to separate the rollers and provide a gap between the slotted steel strip and the tapered rollers. This allows the slotted steel strip to be pulled back by the permanent magnets 3 (Fig 8) to its original position. 4. When this sequence of operation is repeated continuously the slotted steel strip gets curled and is directed to move on top of tapered roller 4 (Fig 12) and accumulates as shown by 31 (Fig 12). The curled slotted steel strip while moving up takes a helical path similar to a spiral staircase. This is represented by 41 (Fig 12). Immediately after passing between the rollers 4 and 5 the slotted steel strip curls and at that stage it is made to graze the radiused forming block 11 (Fig 13). The function of the forming block is to impart consistency to the outside diameter of the curled slotted strip. The function of the inclined rollers 13(Fig 13) is to remove the effect of dishing during processing. It will be observed that the three support rollers 29 (Fig 12 & 13) are located approximately 120 degrees apart over which the slotted helical steel strip is stored. A freely rotating pipe structure is provided at the centre of 9 the coil to assure that accumulated coil do not topple over. For clarity this pipe has not been shown in the illustration. The accumulated helical slotted steel strip 31 (Fig 12) after being cut from the parent material has to be welded on a specially designed mandrel to impart required accuracy. For the ultimate accuracy of the stator core, pitch of the slotted steel strip has to be uniform and dimension should be such that when matched for the number of slots the inside diameter has to confirm to the specification. Process of curling and getting a helical slotted coil out of straight slotted strip cannot impart final accuracy because of its flexible nature. Holding the helical slotted strip on a specially designed fixture imparts the final accuracy to the stator core. There are two types of stator core that can be manufactured from helical slotted strip. i) Stator core with straight flutes (See Fig 14) ii) Stator core with skewed flutes (See Fig 15) These are described below : Stator core with straight flute : Referring to Fig 17 and 18, loading mandrel 40 (Fig 17) and welding mandrel 41 (Fig 17) are held one over the other on a turn table 42 (Fig 17) through which a draw bar 43 (Fig 17) passes. In the open position, the draw bar moves up a little more than the thickness of the stator core to be produced. In that position "C" washer 44 (Fig 17) and spacer 45 (Fig 17) are removed. Fig 18 show plan view of the mandrel along with inserts 46 & 47. Fig 19 & Fig 20 show full size view of these mandrels along with inserts 46 & 47 (Fig. 20). Top end diameter of mandrel 40 (Fig 19) represented by dia "d" is ground to the same size as internal diameter of the stator core. Width of spline on the welding mandrel represented by "T" (Fig 19) is the same as required on the stator core while that of loading mandrel is 10 slightly smaller for ease of loading. Helical slotted steel strip as it comes out of curling apparatus have a leading and trailing ends. Both these are to be hooked to the inserts 46 and 47(Fig 20). As one of the end of the slotted helical coil is hooked to the insert a light twist either clockwise or anticlockwise, as required, is given to the bunch of coil till the internal diameter of the helical coil engage with the top end diameter "d" of mandrel 40 (Fig 19). In this condition all the slots in the helical slotted strip gets lined up and freely enters on the spline mandrel 40 (Fig 19) with a slight downward push. This process is repeated several times so that the entire helical slotted strip is accommodated on the mandrel 40 (Fig 19) and trailing end also gets hooked up to one of the insert either 46, 47(Fig 20). Next the spacers 45 and "C" washer 44 both (Fig 17) are placed in position. In this condition the draw bar 43 is pulled down by pneumatic or hydraulic cylinder. As the slotted helical coil moves down the splines rides over the small chamfer 48 (Fig 19) and gets properly located. Further downward pull of the draw bar 43 (Fig 17) compacts the slotted helical coil and it is then welded in that condition. Welding is carried out in generally six locations as indicated and the turn table automatically does that. On completion of the welding three pins 49 (Fig 17) eject the welded stator core from the welding mandrel. Stator core with skewed flutes : Item 51 (Fig 21) is a solid mandrel with centers on both ends, a flange 52, body diameter "dl" which is the same as the required internal diameter of the stator core, a threaded portion 53 (Fig 21) and a suitable extension 64 (Fig 21). End plate 54 (Fig 21) is keyed to the mandrel by key 55(Fig 21). Copper inserts 56 (Fig 22) in six locations are held to facilitate striking of arc for welding. End plate 54 (Fig 21) has a recess which accommodate a block 58(Fig 22). This block has a taper face and is used to clamp starting end of slotted helical coil item 19 (Fig 23), 11 after being mounted on mandrel 51 (Fig 21). When nut 62 (Fig 21) is tightened the leading edge of the slotted helical coil gets locked. While preparing the leading edge by trimming and bending the line of bend is positioned such that the welding groove lines up in the recess where copper inserts 56 (Fig 22) are located. Trailing end of the helix is similarly prepared and held on end plate 60 (Fig 21). At least six holes are drilled radially on item 60 (Fig 21) to facilitate rotating. When this end plate is rotated about the mandrel, either clockwise or anticlockwise, the slotted helical coil wraps around the mandrel. In this position the nut 62(Fig 21) is tightened to prevent end plate 60 (Fig 21) from rotating. The six grooves on the outer diameter gets skewed as also the slots on the inner diameter. This condition will be evident from Fig 15. While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown in the drawing and have been described herein by way of example only. However it would be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. 12 WE CLAIM 1) An apparatus for producing helical curled stator core from a wide strip having slots on one edge and notches on the other, comprising two identical motorized spindles having gear on one end and taper on the other end, one spindle having fixed housing and the other having a hinged housing, a hydraulic cylinder located under said hinged housing, guide means comprising multiple magnets, blocks of hard material such as tungsten carbide and guide rollers, radius sizing block, two adjustable parallel rollers positioned next to said block and holding means located mid way between said taper roller and parallel rollers to produce helically coiled stator from straight strip. 2) The apparatus as claimed in claim 1, wherein said means for feeding the strip comprises a plurality of permanent and/or electro magnets positioned on either side of a feed path made of hard surface such as tungsten carbide. 3) The apparatus as claimed in claims 1, wherein said adjustable parallel rollers are located on the path of the helically formed strip in order to remove dishing and to guide the strips for storage. 4) A method of producing circular station core from a strip having slots on one edge and shallow notches on the other by an apparatus as claimed in claims 1 to 3, said method being carried out under constant pressure. 5) The method as claimed in claim 4, wherein said helically coiled stator coil is welded on mandrels to provide rigidity thereto. 13 6) The method as claimed in claim 5, wherein said mandrels of atleast one loading mandrel and one welding mandrel provided with fastening hooks for hooking the leading and trailing ends. 7) The method as claimed in claim 5, wherein stator core produced is wounded tightly on a solid mandrel to obtain skewed stator core. 8) The stator core when produced by an apparatus and a method as claimed in the preceding claims. 14 ABSTRACT "An apparatus and a process for manufacture of wide web stator core by rolling process" This invention relates to an apparatus and a process for manufacture stator core circular in structure made from straight wide width steel strip having slots on one edge and shallow notches on the other edge by a process of rolling a portion of the strip between two geared tapered rollers. The rolling action progressively stretches the material that forms the outer diameter and as a result it gets curled. When the process is continued the strip takes the shape of a helical coil. After the desired number of turns the helical coil is formed it is cut off from the parent material. This helical coil is subsequently held on a mandrel and welded on shallow notches 'provided on the outer diameter. Further process i.e. burnishing, sizing, coining, turning, grinding etc is carried out as required to complete the helically wound stator core. Figure 1

Documents:

1392-MUM-2005-ABSTRACT(9-11-2005).pdf

1392-mum-2005-abstract(granted)-(28-5-2009).pdf

1392-mum-2005-abstract.doc

1392-mum-2005-abstract.pdf

1392-MUM-2005-CANCELLED PAGES(29-1-2009).pdf

1392-MUM-2005-CLAIMS(10-7-2008).pdf

1392-MUM-2005-CLAIMS(9-11-2005).pdf

1392-MUM-2005-CLAIMS(AMENDED)-(29-1-2009).pdf

1392-mum-2005-claims(granted)-(28-5-2009).pdf

1392-mum-2005-claims.doc

1392-mum-2005-claims.pdf

1392-MUM-2005-CORRESPONDENCE(10-7-2008).pdf

1392-MUM-2005-CORRESPONDENCE(26-2-2008).pdf

1392-MUM-2005-CORRESPONDENCE(29-1-2009).pdf

1392-MUM-2005-CORRESPONDENCE(IPO)-(30-6-2009).pdf

1392-mum-2005-correspondence-others.pdf

1392-mum-2005-correspondence-received-ver-141106.pdf

1392-mum-2005-descripiton (complete).pdf

1392-MUM-2005-DESCRIPTION(COMPLETE)-(10-7-2008).pdf

1392-MUM-2005-DESCRIPTION(COMPLETE)-(9-11-2005).pdf

1392-mum-2005-description(granted)-(28-5-2009).pdf

1392-MUM-2005-DRAWING(10-7-2008).pdf

1392-MUM-2005-DRAWING(9-11-2005).pdf

1392-mum-2005-drawing(granted)-(28-5-2009).pdf

1392-mum-2005-drawings.pdf

1392-MUM-2005-FORM 1(10-7-2008).pdf

1392-MUM-2005-FORM 1(9-11-2005).pdf

1392-mum-2005-form 13(04-05-2009).pdf

1392-MUM-2005-FORM 13(8-11-2006).pdf

1392-MUM-2005-FORM 18(12-1-2007).pdf

1392-mum-2005-form 2(10-7-2008).pdf

1392-MUM-2005-FORM 2(COMPLETE)-(9-11-2005).pdf

1392-mum-2005-form 2(granted)-(28-5-2009).pdf

1392-MUM-2005-FORM 2(TITLE PAGE)-(10-7-2008).pdf

1392-MUM-2005-FORM 2(TITLE PAGE)-(COMPLETE)-(8-5-2009).pdf

1392-MUM-2005-FORM 2(TITLE PAGE)-(COMPLETE)-(9-11-2005).pdf

1392-mum-2005-form 2(title page)-(granted)-(28-5-2009).pdf

1392-MUM-2005-FORM 3(10-7-2008).pdf

1392-MUM-2005-FORM 3(9-11-2005).pdf

1392-mum-2005-form-13.pdf

1392-mum-2005-form-18.pdf

1392-mum-2005-form-2.doc

1392-mum-2005-form-2.pdf

1392-mum-2005-form-26.pdf

1392-mum-2005-form-5.pdf

1392-mum-2005-form-9.pdf

1392-MUM-2005-SPECIFICATION(AMENDED)-(10-7-2008).pdf

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