US2892249A

US2892249A - Method of manufacturing a transformer core construction

Info

Publication number: US2892249A
Authority: US
Inventors: Albert E Feinberg; Frank S Endo
Original assignee: Advance Transformer Co
Current assignee: Advance Transformer Co
Priority date: 1956-01-10
Filing date: 1956-01-10
Publication date: 1959-06-30
Anticipated expiration: 1976-06-30

Description

' June 30, 1959 A. E. FEINBERG ETAL 2,892,249

METHOD oF MANUFACTURING A TRANSFORMER com: CONSTRUCTION Filed Jan. 1o. 195e 2 sheets-sheet 1 l' l 33- 'III' 36 l N w June 30, 1959 A. E. FEINBERG ETAL METHOD OF MANUFACTURING A TRANSFORMER CORE CONSTRUCTION 2 Sheets-Sheet 2 Filed Jan. 1o, 195s United States Patent O METHOD F MANUFACTURING A TRANS- FORMER CORE CONSTRUCTION Albert E. Feinberg and Frank S. Endo, Chicago, Ill., as-

signors to Advance Transformer Co., Chicago, lll., a corporation of Illinois `Application January 10, 1956, Serial No. 558,236

2 Claims. (Cl. 'Z9-155.61)

This invention relates generally to electro-magnetic devices such as the transformers of apparatus for igniting and operating gaseous discharge devices. Particularly the invention is concerned with the structure of the core and laminations making up such transformers.

The shell type of transformer core is desirable from many standpoints. It is easy to assemble, compact, results in a quiet transformer, and usually provides at least one complete unbroken magnetic circuit in the frame. By reference to the designation shell type it is intended to designate a type of core structure in which there is a usually elongate rectangular outer frame member having parallel elongate side parts bridged at their ends by short bridging portions maintaining the spacing across the narrow dimension of the frame member. A central winding leg extends along the core, being matingly engaged at its ends with the respective bridging portions. The side parts have windows punched on opposite sides of the winding leg so that coils mounted on the winding leg or bar will be positioned in the windows. Extensions may be provided to separate adjacent windows and form shunts.

The shell type core is usually formed of stacks of laminations in which those laminations stacked to pro vide the central winding leg have been punched out of the center of laminations which thereafter form the framing portion. The material punched out to form the windows is scrap, which is quite substantial in the shell type core. Obviously scrap increases costs and ultimate prices to consumers.

The invention herein also utilizes a shell type core but not of the construction in which the frame portion is an integral member, that is to say an unbroken member formed of a stack of rectangular one piece laminations. The primary object of the invention is to provide a core construction of shell type made up of laminations so formed and shaped as to produce an extremely small quantity of scrap, while providing a highly eifective, electrically and magnetically eicient transformer core.

The invention contemplates the mating formation of parts which will be assembled in stacks out of continuous electrical steel strips running at high rates through automatic stamping machines. In other words, the parts of each laminated layer of the core are so arranged along a continuous uniform width strip that the scrap is minimized.

It is understood that the mere mating arrangement of laminations or parts of laminations along electrical steel strips to decrease total scrap generally has been known, but where special requirements demand the provision of shunts in the core, scrapless mating of parts has not been accomplished to any practical degree. Even Where scrap of some quantity is expected, known structures have not achieved the highly economical core of this invention and this accomplishment is another object of this invention.

The novel core of the invention is made up of several parts, comprising the central winding leg or bar, and two 2,892,249 Patented June 30, 1959 outer elongate members which are disposed on opposite sides of the winding leg and clamped thereto and provide the framing portion. The assemblage can be considered a unitary structure because of the abutting joints between tion is not so constructed.

The invention resides in the provision of a core structure formed of T and L shaped parts forming the shell. The difference between this and prior structures, inter alia, lies in the fact that although the parts are arranged matingly along the strip from which the same are punched, the extensions which will form the shunts in the assembled core are integral with the parts so that there is no need to insert separate shunts. One form of the invention, which is especially economical, utilizes parts which are formed in such a manner that the central winding leg will have indentations from the punching out of the extensions of the side parts, but such indentations are positioned at a part of the transformer where their effect upon the eicient operation of the transformer is practically unnoticed. l

Many objects and advantages will occur to those skilled in this art as a detailed description of specic and preferred embodiments of the invention is set forth herein after, in connection with which illustrations are provided for clarity and to aid in an understanding of the invention.

In the drawings, in which the same characters of reference are used throughout the several figures in order to designate the same or similar parts:

Fig. 1 is a diagrammatic top plan view of a transformer constructed in accordance with the invention, and using the novel core of the invention, the coils being shown in section in order better to illustrate the details.

Fig. 2 is a fragmentary top plan View of a strip of electrical steel showing the lay-out of the parts of the core of Fig. 1 along the same to illustrate the small amount of scrap resulting from the core structure.

Fig. 3 is an electrical diagram of the circuit of the apparatus with which the transformer of Fig. 1 is intended to be used.

Fig. 4 and 5 illustrate ditferent layouts along strips of electrical steel for a slightly modified form of the invention, but in which there is slightly more scrap resultmg.

Fig. 6 is another illustration of a layout of parts of a core along a steel strip, the view being quite similar to that of Fig. 2, but the form of the invention being subtantially identical to that of Figs. 4 and 5.

Looking tirst at Fig. 1, there is illustrated a transformer 10 which is formed of a so-called iron core 12 which shortly will be described in detail. The transformer 10 is intended to be connected into a circuit for igniting and operating two gaseous discharge devices in a manner illustrated in Fig. 3. There the transformer core is shown to mount four windings comprising a primary winding P connected across a relatively low Voltage A.C. line 14, a tirst secondary Winding S1 which is spaced from the other windings along the core 12 and separated therefrom magnetically by means of a shunt 16, a second secondary winding S2, and an extension of the second secondary winding which is designated S21. The windings are connected end to end in order named, but the physical placement on the core 12 is otherwise. The tirst secondary winding S1 is disposed on the left hand end of the core 12 as viewed in Fig. 1, and the second secondary winding S2 is disposed on the right hand end. The primary winding P is in the center of the core and alongside the winding S2 and separates the winding S3 from its extension S2'.

As shown in the circuit diagram of Fig. 3, there is a gaseous discharge device such as a fluorescent lamp L1 connected in series with a condenser C and together therewith connected across the winding S1. There is a second lamp L2 which is connected across all of the windings. In operation, the lamp L1 lights iirst after which the lamp L2 lights, and, by virtue of the placement of'the` winding S1 and the shunt 16, current principally liows in series through the lamps and the windings S3 and S2 and the condenser C. The exact manner of operation is described in U.S. Letters Patent No. 2,683,243 olf` A. Feinberg, one of the applicants herein.

It` be seen that the construction of the core is such as to accommodate the windings described, provide theA necessary shunt, and the air gaps and magnetic structure. is done in theinvention, without losing any ofthe advantagesaccruing by virtue of the highly construction of the core and the formation of the'laminations thereof from strips of steel in the manner described in detail hereinafter.

The core 12 is formed of three stacks of laminations hdd, L Seh in any suitable manner by clamps or other fastening devices which are well known and need not be shown. There is a T-shaped central winding leg or bar 20., the cross; head 22 of which is shown at the right hand end in Fig. l forming the bridging magnetic connection of that end. Spaced inwardly of the right hand end there isprovided a slot 24, the purpose ofwhich is' to improve wave shape in the manner described in Paul Berger application for Letters Patent Serial No. 503,163 filed April 22, 195,5. There is also a pair of identical side legs 26. L-shaped with the short. leg 28 Aof each facing inwardly abutting the left end of the central winding leg or bar 20 on opposite sides thereof and making magnetic connection therewith at 30. The right hand end of the side legs 26 meet the` outer ends ofk cross head 22 in similar abutting joints 32.

The. windings described are.y mounted along the central windingleg or bar 20 in the order also set forth, and ther shunt 16 is disposed between the winding S1 and Szf. The shunt 16V is formed by means of the inwardly extending lugs 34 integral with the side legs 26 and 27. The ends of the lugs are spaced from the sides of the central winding leg by some predetermined amount in order to provide the usual air gaps 36 of such shunts.

Attention is invited to the recesses 38 which are provided in the central winding leg 20 between the shunt i6 and the` left hand end of the core 12. These recesses are completely covered by the first secondary r winding S1 which is the high leakage reactance winding ofl the appar atus,'and which carries very little current, compared Ito the other windings of the transformer 10, once' the lamps are ignited. It has been found that positioning the recesses beneath the coil of the windingrSl prevents the leakagev which might be. caused byv such a Ar'ecessffrorn producing noise in the cannister containingthe apparatus. Also, since this winding will carry little current duringthe operation of the lamps, the eiiects of high f luxpdensity onwave shape caused by an effective narrow cross sectionV of` the central winding legl aresubstantially reduced.

Since the adverse effects of the recesses 38 are tolerable because of thenature of the operation of the transformer, it is possible` to produce the parts of the transformer coreI `12Vvery economically.

In; orderA to avoid confusion herein, the same characters of` reference will be used to designate the stacked partsof thecore 12 andtheindividual laminations used to makeup such stacks.` Thus, in Fig. 2 which shows a single,thickness. of a steel strip having parts of laminationslaidlout thereon, the reference character 20 designates a lamination intended to be combined with identical laminations in a stack to form the T-shapedcentral These side legs or parts are,

winding leg 20. Likewise the individual stampings 26 will be used to make the side legs 26.

The strip of electrical steel 40 has the

parts

20 and 26 laid out thereon in groupings of two side legs and one central winding leg disposed therebetween. The central winding leg part 20 however is shifted to the right relative the side legs 26 when compared with the eventual position in the assembled core. Thus, the side leg parts of each group are laterally closer together and the end of the central winding leg is abutted against the inside of the short legs of the side legs at 42, with the cross head 22 outside the right hand end of the side legs 26. The extensions 34 are punched out of the body of the central winding leg parts 20 giving rise to the recesses 38 referred to above.

With the layout described the amount of scrap is extremely small. All scrap areas in the drawings are shaded and marked S to identify the same, and it will be seen that the areas of Fig. 2 are quite small. There is one area and an area 46 for every group of parts.

The groups are arranged side by side with the backs of parts 26 abutting along lines 48.

When the parts are stacked and assembled, the central winding leg 20 is shifted to the left, the side legs 26 being spread to accommodate-the same, resulting in the structure of Fig. l which provides-the necessary windows for the windings.

In certain structures it might be disadvantageous to have the recesses 38, and hence the layout of parts is somewhat different. In Fig. 6 there is illustrated a yfragment of a strip of steel, in which the central winding leg part 20 is shifted to the right compared to the layout of Fig. 2 so that it abuts against the side of the extensions 34. Thus all of the strip which is contained between the side legs 26 and to the left of the end of the Winding leg 20 is scrap, designated 52. Likewise,

since the` cross head 22 `protrudes considerably beyond the ends of the side legs 26, there will be an additional irregular scrap area 54 between each groupof' parts. The side legs 26 are back to back along the line 48. The strip 50 will obviously be wider than thestrip 40 and the amount of scrap from the layout of Fig. 6 v

greater thanA from the layout of Fig. 2.

In Figs. 4 and 5 there are illustrated the layouts for parts along steel strips 56 and 58 for forming the winding leg parts. 20 and ther side legparts 26 separately, instead of4 in the same operation as described hereinabove. In' Fig. 4 the Winding leg parts 20 are formed side by side and with heads alternately reversed to give rise to a single scrap area 60 for. eachfpart. In Fig. 5 the pairs of side legs- 26xare laid out for punching with the short 1legs28` and extensions 34 facing but the ends reversed so that there is. mating of the parts and a minimum of scrap. The pairs are back to back. Each pair produces two irregular scrap areas 62 of the same size.

lt is believed that the invention should beobvious without'further description, and it isdesired to point out that variationsin details are possible without departing from the scope asdened inthe claims. The structure shown in the drawings was used in constructing apparatus which gave successful results whenused withtwo fwatt instant start fluorescent lamps. The width of the central winding leg was approximately 1% inches and the other' The two windows'accommodate all windings, with-the winding S1 being 1.8 inches long,.and the other. three combined being a total of approximately, 5 inches in` length. The condenser C was 1.74 microfarads.`

Although .not illustrated, in addition `to the lscrap, which is shown in the accompanying drawings, there may be a very narrow strip which is called a carrying strip alongside any of lthe wider strips illustrated for the purpose of supporting the partly punched laminations during progrcssive movement through the die. The use of carrying strips is a technique Well known in the art. in addition, although not illustrated, the corners of the side parts 26 may be notched for the seating of clamps. This also is known and need not be illustrated.

What it is desired to secure by Letters Patent of the United States is:

1. A method for producing a shell-type transformer core which is comprised of individual laminations of electrical 4steel stacked and arranged together in a unitary core structure and in which the individual laminations consist only of an elongate T-shaped member and an elongate L-shaped member, said T-shaped members are stacked to form the central winding bar of the core and said L-shaped members are stacked and arranged with respect to the stack of T-shaped members to form the side parts of the core, the lengths of side parts are equal and the sum of the width of the long leg of the T-shaped lamination plus twice the maximum length of the short leg of the L-shaped lamination is equal to the maximum length of the crosshead of the T-shaped lamination plus twice the Width of the Ilonger leg of the L-shaped lamination, and there is a lug integral with the long leg of the L-shaped lamination extending in the same direction as the short leg thereof: said method comprising, stamping said T-shaped and L-shaped laminations in a continuous process from a sheet of electrical steel moved through a stamping machine, albeit in a predetermined geometric arrangement of said individual laminations along the direction of movement of said sheet which defines groups of said laminations, each group including a pair of said L-shaped laminations and one of said T-shaped ilaminations, each T-shaped lamination having an L-shaped lamination on opposite sides of the long leg of said T- shaped lamination with each side edge of the long leg of the intermediate T-shaped lamination abutting a side edge of the long leg of one of said pair of L-shaped laminations, the cross-head of the T-shaped lamination abutting the long leg of each one of said pair of L-shaped laminations whereby said stamping results in a substantail reduction in waste, forming said lugs at the `same time of stamping on each long leg of the larninations of said pair, thereafter stacking and assembling said L-shaped and T-shaped laminations to form said core.

2. A method for producing a shell-type transformer core which is comprised of individual laminations of electrical steel stacked and arranged together in a unitary core structure and in which the individua-l laminations consist only of an elongate T-shaped member and an elongate L-shaped member, said T-shaped members are stacked to form the central winding bar of the core and said L-shaped members are stacked and arranged with respect to the stack of T-shaped members to form the side parts of the core, the lengths of side parts are equal and the sum of the width of the long leg of the T-shaped lamination plus twice the maximum length of the short leg of the L-shaped lamination is equal to the maximum length of the cross-head of the T-shaped lamination plus twice the width of the longer leg of the Lshaped lamina tion, and there is a lug integral with the long leg of the L-shaped iamination extending in the same direction as the short leg thereof: said method comprising stamping said T-shaped and L-shaped laminations in a continuous process from a sheet of electrical lsteel moving through a stamping machine, albeit in a predetermined geometric arrangement of said individual laminations along the direction of movement of said sheet in which a pair of L- shaped laminations have the long legs thereof arranged back to back transverse to the direction of movement of the sheet and the short legs of the pair face in opposite directions and are approximately ush vwith a side edge of the sheet, said pair of L-shaped laminations are spaced longitudinally along the sheet from a second pair of L-shaped laminations `likewise arranged back to back with the :shorter legs thereof approximately flush with the same side edge of the sheet, and there is a T-shaped lamination between said two pairs of L-shaped laminations with its cross-head approximately flush with the opposite side edge of the ISheet and the end of the longer leg thereof remote from said cross-head spaced from said one side edge a distance equal to the width of a said short leg, the side edges of the long leg of the T-shaped lamination abutting the side edges of the long leg of an L- #shaped lamination of each of said pairs whereby during said stamping there results substantial reduction in waste, and said lugs are formed during stamping of the laminations on each long leg of an L-shaped lamination of said pair abutting the long leg of the T-shaped lamination with accompanying formation of a recess in the said long leg of the T-shaped lamination, thereafter stacking and assembling said individual laminations to form said core.

References Cited in the le of this patent UNITED STATES PATENTS 509,770 Scott Nov. 28, 1893 1,314,051 Dorman Aug. 26, 1919 1,472,023 Koos Oct. 23, 1923 1,962,431 Daley June 12, 1934 2,085,092 Furth June 29, 1937 2,330,824 Graniield Oct. 5, 1943 2,575,093 Bridges Nov. 13, 1951 2,582,291 Sola Ian. l5, 1952 2,708,741 Orsini May 17, 1955