US3538601A

US3538601A - Method for the manufacture of laminated electromagnetic cores

Info

Publication number: US3538601A
Application number: US730439A
Authority: US
Inventors: Patrick J M Nerot; Claude P Vinot
Original assignee: Telemecanique Electrique SA
Current assignee: Telemecanique SA
Priority date: 1967-05-26
Filing date: 1968-05-20
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10
Also published as: DE1764271C3; SE367887B; DE1764271A1; NL6807152A; GB1158859A; AT284251B; CH488258A; NL157736B; LU55958A1; DE1992600U; BE714018A; DK137298C; DK137298B; FR1532459A; DE1764271B2

Description

Nov. 10, 1970 -r ETAL 3,538,601

METHOD FOR THE MANUFACTURE OF LAMINATED ELECTROMAGNET CORES Filed May 20, 1968 g I INVENTORS Patrick J-M. NEROT Claude P. VINOT United States Patent Int. Cl. rioir 7/06 U.S. Cl. 29-609 Claims ABSTRACT OF THE DISCLOSURE A method for the manufacture of an electromagnet core made of a movable and of a stationary part WhlCh comprises assembling punched laminations into two stacks to form the said parts, each defining a polar surface and truing only one of said polar surfaces, by grinding, the other polar surface remaining rough.

An electromagnet core formed of a movable and of a stationary part and made of laminations stacked into the said parts, each part defining a polar surface. One of the polar surfaces is a polished surface whereas the other polar surface is defined by rough edges of the corresponding laminations.

-The present invention relates to a method for the manufacture of laminated electromagnet cores and cores so obtained.

More specifically, the present invention relates to a very simple method for manufacturing stationary or movable laminated cores usually used in alternating current ,electromagnets. These cores are made in magnetic laminations punched in the form of an E or an U, the said laminations being thereafter assembled in generally riveted stacks. In many devices, such as relays or contactor,.one of these stacks forms the stationary portion and carries the magnetic coil that creates the magnetic flux on one of its branches whereas the other portion, called the armature, is movable in translation or in rotation of a relatively small angle.

A method for the manufacture of an electromagnet will be found, by way of example, in U.S. Pat. No. 2,997,- 633, issued Aug. 22, 1961. Such an electromagnet is capable of resisting a very high number of operations without decreasing the quality of the magnetic circuit with regard to the ill effects of the residual magnetism.

One object of the manufacturing method of the invention lies in that it makes it possible to obtain still better results with simpler, and consequently, more economical means. It relates to a two-part electromagnet of which one part is movable in relation to the other, that obviates the sticking effect of the polar surfaces and with a very high manoeuvring possibility without deterioration of the said surfaces. It is applicable to all shapes of electromagnet cores but it is particularly efiicient for a magnetic core made of two branches such as those made with U-shaped laminations and provided with an antiresidual 4 air gap incorporated in the branches. This type of electromagnet is described and illustrated in U.S. Pat. N0. 1,518,020, issued Dec. 2, 1924.

When the antiresidual air gap is obtained by a narrow space resulting from an interruption in the metal of the core branches themselves and not by the polar surfaces that separate the stationary and movable parts, it is sure that the antiresidual air gap will remain constant even after a very large number of operations as it will not be altered by wear or by the meeting surfaces of the parts being pushed back. It is consequently not necessary in such a case to harden the said surfaces by a chemical treatment. But, as has been observed in the prior technique, it is advantageous to provide the meeting surfaces of the electromagnet with a fine oil film which, on the one hand, gives protection against corrosion and, on the other hand, absorbs the meeting shock. This greasing method by an oil reserve located between the laminations and that slowly seeps onto the polar surface is already known by itself and already provides a very important improvement in the quality of electromagnetic subjected to armature shocks repeated several millions of times.

The oil reserve between the laminations may be used as well as with E-shaped three-branch cores or U-shaped two-branch cores. In each case, there will be two cooperating polar surfaces narrowly joined since, if the core is U-shaped, there must be an incorporated air gap.

In known manner, these joined surfaces are obtained by truing up the stack of assembled laminations by grinding. The coexistence of these means: the oil film on the polar meeting surfaces and the same surfaces being trued up by grinding has drawbacks. On the one hand, during repeated closures of the armature, the oil film bursts and splashes on the external parts. On the other hand, the flat polished surfaces have a tendency to stick to one another and prevent the reopening of the magnetic circuit. To obviate this, truing by grinding of the two parts of the core could obviously be totally omitted but the magnetic circuit would then vibrate and make a great noise when excited.

In a magnetic core of a laminated electromagnet comprising an oil reserve supplying an oil film on the polar surfaces, a surprising effect has been noted that if, according to the invention, all of the polar surfaces of one part of the core are trued up by grinding whereas the cooperating surface of the other part is only equalized by ramming but not trued up, the sticking effect of the said surfaces is avoided simultaneously with obtaining a much greater number of operations than usually obtained with industrial electromagnets.

By way of example, one embodiment of a method for the manufacture of a magnetic core according to the invention will now be given with reference to drawings, such embodiment is limited however to the only features of the method, it being understood that the construction I of laminated cores is well known in itself.

spread over the laminations during punching. Then the laminations are degreased by immersion in a bath of liquid trichlorethylene at a temperature of 87 C., the immersion period being'about 20 minutes to obtain a weight of oil of 0.2 mmg./cm. This figure is suitable for a small magnetic core of 76 g. such as used in relays. For more involved magnetic cores, the amount of oil may attain 0.5 mmg. per cm. the immersion period being then reduced. In every case, experimentation must be made and the amount of oil needed may vary from 0.1 to 0.5 mmg. per cm. One of the stacks of laminations, for instance that which constitutes the armature 1 of the electromagnet, may thereafter be assembled by any convenient means such as rivets 2. It is thereafter trued up by grinding to obtain perfectly fiat polar surfaces 3. The

other stack of laminations, corresponding in this instance to the stationary part 4, is placed in a gig and also assembled. The polar surface 5 of the latter stack is thus, constituted by the rough edges of the punched laminations without any particular hardening treatment. However, as the punched laminations are removed from the machine, they are progressively picked up by stringing them in such a way that they may be assembled parallel with an in the same direction as that of the work of the punching tool. It will be observed also that a certain hardness is already obtained by the cold hammering of the metal in the work of the press tool. This second stack of laminations remaining in its gig is then rammed by a force directed in the plane of the laminations and against the polar surfaces. For this purpose, it is only sufficient to'give these surfaces a simple press blow. The two stacks of laminations are then joined and assembled with the other parts of the electromagnet.

With a two-branch circuit constructed according to the above-described method, it has been possible to obtain a satisfactory working during forty million operations. The method is extremely economical since it requires no special chemical or thermal treatment and that it even omits one of the usual truing operations.

The very interesting technical result obtained may be explained as follows: the polar surfaces 3 and 5 movable against one another are of different physical nature. On the one hand, a surface 3 polished by the work of the millstone, on the other hand, an irregular surface 5 formed of very small grooves 6 as illustrated in FIG. 2. Indeed, during the punching operation of the laminations, there is produced along the punched contour a small round on one side and a small burr on the other side rather than two sharp edges. Thus, the parallel assembly of the punched laminations in the same working direction gives, on the edge of the stack of laminations, a series of narrow parallel surfaces separated by minute edgy groove 6; besides, these surfaces have been subjected to a certain hardening inherent to the cold working of the metal. The groove '6 thus formed and that would disappear if they were trued up by grinding will thus serve to hold into position the oil film that comes from the reserve between the laminations. Furthermore, the cooperating polar surfaces 3 and 5 may no longer adhere as would two polished surfaces under atmospheric pressure. Finally, the voids corresponding to the grooves fin rea e ta c ..,th ma neti c rcu tthus proving the antiresidual effect.

It is clear that the scope of the invention is not limited to electromagnet parts as described above but that it also relates to any other assembly of magnetic laminations of an alternating current electric apparatus.

We claim:

1. A method of manufacturing a laminated electromagnet core comprising: punching metal laminations into a predetermined shape; spreading over the surface of the laminations a predetermined amount of oil which is proportional to the size of the laminations; assembling said punched laminations in parallel relationship into stacks to constitute two core portions defining rough polar surfaces while maintaining a common direction for the mounting of the stacked laminations with regard to the punching direction, truing up the rough polar surfaces of only one of said stacks by grinding, aligning the laminations of the other stack by ramming against its rough polar surface, and assembling said two core portions to form an electromagnet core having cooperating polar surfaces.

2. Amethod as defined in claim 1 including degreasing said laminations.

3. A method as defined in claim 2 wherein said degreasing includes immersing said laminations in a bath of liquid trichlorethylene.

4. A method as defined in claim 1 wherein said predetermined amount of oil spread over the surface is from 0.1 mmg./cm. to and including 0.5 mmg./cm.

5. A method as defined in claim 1 including forming minute grooves on said polar surfaces when said laminations are assembled in parallel relationship.

References Cited UNITED STATES PATENTS 1,834,898 12/1931 Boyajian 29-609 2,541,502 2/1951 Cross et al. 29-609 X 2,997,633 ,8/1961 Ellis et a1. 335-281 3,058,039 10/1962, Ray 335-281 X JOHN F. CAMPBELL, Primary Examiner C. E. HALL, Assistant Examiner US. 01. X.R. 29-602; 335-281; 336-212, 234