US2582984A - Laminated assembly - Google Patents

Description

Jan. 22, 1952 F. GRAY LAMINATED ASSEMBLY Filed June 19, 1947 INVENTOR FRANK GRAY ATTORNEY Patented Jan. 22, 1952 LAMINATED ASSEMBLY FranlrGray, London, England, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application June 19, 1947, Serial n m'zsass 'In Great Britain May 17; 1946 Saa i, Public Law 690, August a, 1946 t Patent expires May 17, 1966 This invention relates to equipment orparts thereof built up of layers o1 material in. which the overall height of a laminated assembly has i cl i (or. Hag-298) to be within predetermined manufacturing limits.

Many equipments of this type are met with in the light electrical field, for instance. in telecommunication equipment. p

It is convenient to state the problem to which the invention relatesand indicate its solution in relation to a particular type of equipment;

One such piece of equipment is the bank of an electromagnetic switch such as is used in auto matic telephone systems. Such a bank comprises straight or arcuate rows of contacts insulated and spaced from one another. Such switches comprise movable contacts or wipers adapted to move relative to the bank, each Wiper during movement contacting in turn with each contact in associated row of contacts in the bank.

It is necessary for eiiicient operation that the contact rows in a bank shall be accurately spaced so that the associated wipers shall contact its associated contacts with the correct pressure dur" ing movement.

It is clear that commercial variations in the thickness of material used for making the contacts, and separators may lead to undue variations in the spacing of contact rows: in fact, the difficulties are so great that it has heretofore been necessary to grade and select certain members of such an assembly in order to ensure that the spacing of contact rows is within allowable limits.

The difliculties arise due to the fact that the cumulative manufacturing tolerances allowable on the thickness dimension of the various materials from which the separators, contacts, insulators, etc. are made, are such, that in the worst Max condition the banks require excessive pressure to compress them within the required limits, whilst in the extreme Min condition, the banks are undersize if compressed sufliciently to grip the terminals so that they will resist the poundage test.

It has now been found that this difiiculty can be simply and cheaply overcome in a manner which allows commercial material to be used without special grading according to thickness.

The method used consists in employing for an element or elements of a pile-up metal of a com-= mercial thickness near the minimum thickness required, in the case of switch banks for aluminum spacers, and forming ribs or other deformations, e. g. domes therein of such height that the ribs can be deformed to the required thickness by 2 the pressure applied in assembly. Any material having suflicient plasticity and strength to be suitable for the. formation of ribs and capable of crushing under pressure to a desired extent and not more could be used for this purpose. metals such as aluminium, brass or copper are suitable materials.

The method can also be' applied for instance to contact spring pile-ups for telephone-type relays and to telephone jack strips but of course is applicable to the manufacture of any light electri'cal equipment in which the problem arises.

The invention will be described with reference to certain embodiments illustrated in the accompanying drawings in which:

Figs. 1 and 2 show in plan and end elevation a ribbed aluminium spacer for a switch bank forming part of an up-and-around telephone type selector switch.

Fig. 3 shows an end view of a typical contact bank embodying the present invention.

Fig. 4 is a cross-sectional elevation of a jack strip embodying the invention.

A switch bank of the type in which the spacer shown in Figs. 1 and 2 may be used is shown in Fig. 3.

Each layer of contact terminals l is placed between laminations 2 of prepared cambric and synthetic resin bonded paper sheet for purposes of insulation. Metal separators 3 are placed between adjacent layers and the whole pile-up is then clamped between steel end plates 4, compressed to the required overall sizes and securely bolted up by means of the bolts 5. It should be mentioned that after tightening is complete, the terminals must resist a lateral pressure of 4 lbs. which is momentarily applied to the extreme tip (outer) of each terminal for test purposes.

The aluminium separators or spacers 3 as shown in Figs. 1 and 2 have fixing holes 6 provided between arcuate ribs 1. The thickness of the material according to commercial ratings is near the minimum limit laid down for the spacers. The height of the ribs is carefully chosen to ensure that when the assembly is compressed the ribbed spacers give way sufficiently to enable the correct overall thickness of the bank to be realized in spite of the normal commercial variations in the thickness of the component parts, whilst at the same time, the terminals are held sufficiently tightly to resist the required test pressure.

By means of this provision, it is possible to manufacture the banks using components made from materials supplied to reasonable commercial tolerances on thickness and by virtue of Soft this, the necessity for expensive operations to grind or otherwise regulate the materials to close dimensional tolerances on thickness has been avoided. In fact it is possible to buy to wider commercial limits than before, e. g. 1.002 inch as against 10005 inch in a thickness of the order of inches and still avoid grading and selection of material.

The preferred overall maximum height of the space at the ribs is with aluminium thick to the above limits.

Fig. 4 shows the application of the invention to jack strips in which the problem arises due to commercial variations in the thickness of sheet ebonite. Each jack assembly comprises a sleeve 8 of brass and tip and ring spring contact pairs 9 and I0 with interleaved spacers H.

The root numeral 12 of the sleeve 8 is corrugated or ribbed as shown at 13 for the purpose specified. Each individual jack pile up is pressed together and insertedjn a slot or milled groove I4 in an ebonite block 15.

The ribs not only. allow the pile-ups to be compressed to the requiredheight for insertion in its groove but also makes the positionin of the pile-up in the groove more secure.

The invention can be applied to equipment comprising one or more laminated assemblies or pile-ups: an up-and-around switch of course usually comprises three contact banks.

' What is claimed is:

A contact bank comprising a series of rows of contact elements, having a plurality of con- 4 tact elements in each row, a pair of strips of insulating material, one on each side of each row. a. plurality of metallic spacing elements each corrugated throughout its length, one spacing member inserted between each pair of rows of contacts with one of the strips of insulating material on each side thereof, and means for clamping the elements together into a unit of a desired dimension by flattening the corrugations of each spacing element as the clamping means is tightened.

FRANK GRAY.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,049,940 Streichert Jan. 7, 1913 1,715,143 Nixon May 28, 1929 2,087,311 Wensley July 20, 1937 2,087,330 Pagenkopf July 20, 1937 2,120,980 Johnston June 21, 1938 2,154,338, Knos Apr. 11, 1939 2,277,443 Livingston Mar. 24, 1942 2,334,897 Baker Nov. 23, 1943 2,395,300 Slauson Feb. 19, 1946 FOREIGN PATENTS Number Country Date 439,500 Great Britain Dec. 9, 1935

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