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United States Patent 3,818,587
Williams June 25, 1974

METHOD FOR PROVIDING STAGGERED JOINT, SINGLE TURN, CUT CORE LAMINATIONS

Abstract

A spirally wound roll of core steel is mounted on the arbor of a cutting and stacking machine. As the roll of core steel is cut by a moving blade, a table moves beneath the arbor at a constant speed catching each lamination as it is cut. The movement of the table as a function of the cutting speed of the blade provides for the offsetting of the ends of the cut laminations thereby providing staggered packets of laminations for later assembly into a staggered joint, single turn, cut core.


Inventors: Williams; Larry D. (Taylorsville, NC)
Assignee: General Electric Company (New York, NY)
Appl. No.: 05/305,795
Filed: November 13, 1972


Current U.S. Class: 29/606 ; 29/56.5; 29/609; 29/738; 336/217; 83/29; 83/88; 83/924
Current International Class: H01F 41/02 (20060101); H01f 007/06 ()
Field of Search: 29/606,609,23L 336/216,217,211 83/29,88,924

References Cited

U.S. Patent Documents
1783040 November 1930 Guay et al.
3186067 June 1965 Somerville
3204501 September 1965 Lane
3327373 June 1967 Somerville
3451130 June 1969 Ellis
Primary Examiner: Lanham; Charles W.
Assistant Examiner: Hall; Carl E.
Attorney, Agent or Firm: Doyle; Francis X. Kelleher; John J. Ulbrich; Volker R.

Claims



What is claimed as new and which it is desired to secure by Letters Patent of United States is:

1. A method of making single turn cut core laminations with the ends of each lamination offset relative to adjacent laminations comprising the steps of winding a strip of electrical grade core steel into a spiral roll comprising a plurality of turns, cutting through the turns of said roll one at a time, each of the cut turns comprising a lamination, each of the cut laminations dropping from said roll to a flat surface and becoming stacked on said surface and moving each said cut lamination longitudinally a predetermined distance with respect to said roll prior to cutting the next lamination thereby to offset the ends of each said cut lamination said predetermined distance from the ends of the next cut lamination upon stacking.

2. A method as set forth in claim 1 in which the outer lamination turn of said roll is formed into a stacking ring after cutting and the remaining offset cut laminations are assembled into said stacking ring to form a single turn cut core having staggered joints.
Description



BACKGROUND OF THE INVENTION

This invention relates to magnetic cores for electrical induction apparatus and more particularly to a method and apparatus for providing single turn core laminations having staggered ends for making single turn magnetic cores.

In the magnetic core art, such as are used in various types of electrical magnetic induction apparatus, it is common to use a build of a number of layers of electrical grade magnetic core steel laminations formed to the shape of a desired core. In general, there are two methods being used to make such cores. The first method comprises the precutting of a sufficient number of separate laminations of appropriately increased length to form the desired core, then stacking the laminations and finally forming such laminations into a desired core. The second method generally comprises winding a single strip of magnetic material about a mandrel to form a roll or core having the desired number of laminations. In general, the second type of core is referred to as a "spirally wound" magnetic core. Regardless of the method used, a magnetic core is subsequently placed about an electromagnetic coil. In many instances, in present day manufacturing operation, the electromagnetic apparatus is generally provided with a preformed coil and the core is placed around the coil by a lacing operation.

The invention disclosed in this application relates to the method of making a spirally wound magnetic core and to a machine utilized in cutting and stacking core laminations. In making the spirally wound magnetic core, it is the usual practice to wind the strip on a mandrel, generally round, and subsequently form the core to a desired shape. The core may be cut either before or after forming and is subsequently placed about a preformed coil. The core is normally annealed to relieve various stresses which are built into the core during its manufacture. The annealing step may be done either after forming or after forming and cutting as desired. As will be understood, the core may be cut as a single turn, two turns, or in half, in the manner of a "C" core. Where the core is cut at only a single turn, it is usually called a "single turn core" in that each of the separate laminations extends for approximately a single turn of the core. In making a single turn core by spirally winding the material on a mandrel, a problem usually arises in that when the core is completely wound, it is necessary to band the laminations to prevent the core from unwinding during the remainder of the core forming process. A further problem arising during the cutting operation is that if the cutting is done prior to annealing, the various laminations tend to loosen and spring out from the wound position. However, if the cutting is done after annealing, the stresses set up by cutting the core are not subsequently relieved and thus tend to increase core losses.

A further problem arising in making the core stems from the fact that it is desirable to provide a core in which all of the joints do not fall in the same area. As is well known, the core joints tend to disturb the magnetic flux flowing in the core, and when the joints are substantially aligned and adjacent each other, they tend to increase the disturbance in each of the laminations, thereby increasing over-all core losses. It is thus desirable to stagger the various joints in adjacent laminations so that they will not fall in the same area and thus will not increase the disturbance of the magnetic flux around such joints. This can be accomplished by cutting each turn of the lamination separately in a staggered pattern in the manner disclosed in U.S. Pat. No. 2,960,756. However, this method has the disadvantage that each lamination must be separately cut thus increasing the labor and time required to form the core. Clearly, it is desirable to provide a single cut in the core and still provide the staggered joints in the finished core.

One method of providing a single cut and obtaining staggered joints is disclosed in U.S. Pat. No. 3,327,373. While this method of U.S. Pat. No. 3,327,373 is very useful, it requires a separate station and a separate operation to obtain the staggering of the ends of the cut laminations. Obviously, it would be more desirable to provide staggering or offsetting of the ends of the cut laminations during the cutting process thereby eliminating the separate operation of staggering or offsetting the ends.

It is, therefore, one object of this invention to provide an improved method of making a single turn, staggered joint, magnetic core.

A further object of this invention is to provide a novel machine for both cutting a spiral core into single turn laminations, and offsetting the cut ends of the single turn laminations in substantially the same operations.

A still further object of this invention is to provide an improved method of making a magnetic core in which only a single cut is made in the core, severing the laminations and in which the joint pattern is staggered at the time of making the cut in the core.

SUMMARY OF THE INVENTION

In carrying out this invention in a preferred form, a spirally wound roll of electrical grade magnetic core steel is provided. The roll of core steel is mounted on the arbor of a cutting and stacking machine. As the cutter of the machine cuts each lamination of the rolled core steel, a table moves beneath the roll at a constant speed, such that each lamination as it drops onto the table has its ends offset from the ends of the previously cut lamination. The entire roll may be cut as a single group of offset laminations or the cutter stopped, the table returned to a given position and then again the cutter started and the table moved at a constant speed beneath the roll to provide a series of packets of offset laminations. After cutting, the laminations are reassembled as a circular core having staggered joints and is then shaped into the desired rectangular or other form of core.

The invention which is sought to be protected will be clearly pointed out and distinctly claimed in the claims appended hereto. However, it is believed that this invention and the manner in which its objects and advantages are obtained, as well as other objects and advantages thereof, will be better understood from the following detailed description of a preferred embodiment, especially when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a preferred form of machine for carrying out the cutting and stacking operation of this invention;

FIG. 2 is a front view of the machine of FIG. 1 showing a roll of core steel being cut and the laminations being stacked, according to the preferred form of this invention; and

FIG. 3 shows one means, according to this invention, of reassembling the cut core into a staggered joint core prior to shaping.

DESCRIPTION OF PREFERRED EMBODIMENT

This invention relates to the method and apparatus for providing staggered joint, single turn, cut core laminations. A preferred apparatus for performing the invention is shown in the drawings. Referring now to the drawings in which like numerals are used to indicate like parts throughout, and referring especially to FIGS. 1 and 2, there is shown a novel machine 10 for cutting and stacking laminations according to this invention. As is shown in FIGS. 1 and 2, the cutting and stacking machine 10 includes an arbor or anvil 12, a cutting blade 14 and a movable table 16. Arbor 12 is fixed to vertical portion 18 of machine 10 which in turn is secured to a base 20.

As is shown in FIG. 2, the arbor 12 receives a roll of electrical grade core steel 22, which is to be cut into single turn laminations.

The blade 14 is mounted on a piston member 24 which is hydraulically actuated through a hydraulic system indicated by pump 26 and lines 28. The table 16 is movably mounted on base 20, being movable up and down on hydraulic cylinder 30 and movable back and forth below arbor 12 by means of hydraulic cylinders 32 and 34. A control unit 36 is provided which controls the movement of blade 14 and table 16 and the other additional portions of the machine, as will be clearer as this description proceeds.

Considering the machine thus far described, its operation will now be set forth. Electrical grade core steel is spirally wound on a mandrel to provide a core or roll 22 of the desired size, in any desired manner, such as that disclosed in U.S. Pat. No. 3,327,373. The roll 22 of core steel is placed on arbor 12 and blade 14 moved down until it almost contacts the top of core 22. The table 16 is then moved upward as necessary beneath core 22 until it is sufficiently close to catch the cut laminations. As the machine 10 is started, blade 14 moves downward at a constant speed cutting separate laminations or turns from the core 22. At the same time, table 16 moves to the right as indicated by arrow 38, at a constant speed. As each lamination or turn is cut, it drops onto table 16 as indicated by laminations 40, 42, 44 and 46 in FIG. 2. As will be apparent, the overlap between the end of each lamination as indicated by x in FIG. 2, is a function of the speed of blade 14 with respect to the speed of table 16. As will be understood, if the table moves rapidly to the right in the direction of arrow 38, as the blade slowly cuts the turns of the core 22, a large distance x will be provided between the ends of the various laminations, while if the table moves slowly with respect to the cutting blade 14, then, of course, a very small offset x will be provided between the ends of the core laminations.

As will be apparent from FIG. 2 of the drawing, as the table 16 moves to the right, each lamination drops in place with the offset x distance between its end and the end of the previous lamination. If desired, the speed of the table, depending on the thickness of the core 22, may be such that the entire core 22 may be cut in a single move of the table, thereby providing one single packet with the ends offset from each other in a manner shown in FIG. 2. However, in the preferred form, as the table moves to the right after cutting a number of laminations, for example, 12 to 20, a stop is provided by control unit 36; the blade 14 stops its cutting and the table 16 is moved or returned to the starting position as indicated by arrow 39. The control unit 36 then continues the operation of blade 14 and table 16, thereby cutting a second group of laminations which will fall on top of the first group forming a second packet. This action may be continued as necessary until all of the core 22 has been cut. Obviously, as many or as few packets may be provided according to the number of laminations, the size of the core 22, and the particular type of electromagnetic apparatus being manufactured.

Referring again to FIGS. 1 and 2 of the drawing, two additional portions of machine 10 are provided in the preferred embodiment. First, as is shown particularly in FIG. 1, a magnet member 50 is provided in back of table 16, the magnet 50 being hydraulically actuated such that with each packet magnet 50 is moved out away from wall 52 to catch magnetically the laminations such as 40, 42, 44 and 46 as they are cut and prevent them from dropping onto table 16 and losing the desired offset x obtained by the cooperative movement of blade 14 and table 16. A second device provided is the movable arm 52 which is also hydraulically actuated and moves against the outer lamination, as is shown, for example in FIG. 2, to hold the lamination between the cuts of blade 14. As will be understood, as blade 14 cuts one lamination, such as 46, the opposite end of 46 is held by 52 until the next lamination is cut, then 52 moves to one side to allow the end of 46 to drop into place and then returns against core 22 to catch the end of the next lamination. Again, this hydraulic member 52 merely prevents the improper stacking of the laminations as they fall into 16.

Also shown in the drawing on table 16 are a plurality of rollers 54. These rollers may be utilized in the preferred form of the invention to roll the plurality of packets of laminations onto a succeeding table for the stacking or reassembling of the core in the manner shown particularly in FIG. 3 of the drawing, to which reference will now be made.

Referring now to FIG. 3 of the drawing, there is shown a table 56 provided with a pair of expanding shoes 58. As indicated in FIG. 3, the outer sheet or lamination from core 22, which was previously cut, is overlapped and crimped as indicated at 60 in the manner, for example, particularly set forth in copending patent application Ser. No. 240,573 filed Apr. 3, 1972 in the name of Willi Klappert for Crimp Locked Outer Turn for Induction Core and which is assigned to the same assignee as this application.

As will be readily understood by those skilled in this art, the outer lamination is separately cut with a large overlap so as to enable such lamination to be used as a stacking ring for the cut core as described in said application, Ser. No. 240,573. Each packet beginning with the outer packet may be stacked within the outer crimped lamination 60 as indicated by the plurality of laminations 62 generally with the ends overlapping as indicated. As each packet is set within the outer crimped layer 60, the expanding shoes 58 are moved outwardly to expand the packet thereby placing the ends in abutting relation. A second packet may then be placed within the first packet and the shoes expanded and this method continued until such time as all of the cut laminations have been placed into the outer turn 60 and the entire core 22 reassembled with the ends in abutting relation as indicated.

After core 20 has been reassembled, as in FIG. 3, the core may be shaped as desired and then annealed, for example, as shown in U.S. Pat. No. 3,327,373.

From the above, it will be apparent that by means of this invention there is provided both a method and an apparatus for providing a single turn cut core in which the single turns are cut and placed in offsetting relation in a single step and then the core is reassembled with the cut ends to provide staggered joints in a single turn cut core.

While the apparatus shown is that which is preferred according to this invention, it will, of course, be understood that various changes may be made in constructional details without departing from the spirit and scope of the invention, particularly as is set forth in the appended claims.

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