US2886745A

US2886745A - Connecting strip

Info

Publication number: US2886745A
Application number: US396018A
Authority: US
Inventors: Pieter Van Leeuwen
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1952-12-05
Filing date: 1953-12-03
Publication date: 1959-05-12
Anticipated expiration: 1976-05-12

Description

E May 12, l959 P. VAN LEEUWEN 2,886,745

coNNEcTlNG STRIP Filed Dec. 5, 1955 INVENTOR PIETER VAN LEEUWEN ill CONNECTING STRIP pany, Inc., New York, N.Y., a corporation of Delaware Application December 3, 1953, Serial No. 396,018

Claims priority, application Netherlands December 5, 1952 6 Claims. (Cl. 317-112) The invention relates to a connecting strip comprising a number of connecting or Contact members which are insulated from one another, more particularly a struc tural element of a bank of contacts for use in automatic telephone systems and the like.

It is known to construct banks of contacts by piling upon one another a number of connecting strips each comprising a row of contact members which generally project beyond the edge of the strip on both sides. Usually the ends at one side of the strip are intended for the attachment of the multiple cables, the ends at the other side for co-operation with a moving contact member, The known connecting strips for this purpose are usually formed by gripping a row of contact members between insulating strips or, as is more usual, by casting or pressing an insulating plastic mass in a mould so as to surround the row of contact members, whereupon the insulating mass is hardened. The connecting strips manufactured in this manner have a limitation in that the limited accuracy of finishing and the distortion of the insulating material, such as shrinkage in cooling, necessitate the acceptance of comparatively large tolerances. Not only comparatively large dimensional departures must be permitted in the relative spacing of the Contact members but also departures in the relative position of the rows of contacts of a number of connecting strips composing a bank of contacts are inevitable. The aforesaid results in that a bank of contacts for a selector switch for use in automatic telephone systems comprising a determined number of contacts per layer must have a definite minimum size for it is necessary that in every rest position of the brush carriage of the selector the brushes co-operate correctly with the bank contacts. Thus, the relative spacings of the contact members due to the tolerances mentioned cannot be as small as would otherwise be possible.

As a rule the rst stage in the manufacture of the known connecting strips comprising liat contact members is to punch a metal plate so as to produce a row of contact members which are mutually correctly positioned and the ends of which are connected to a remaining part of the plate. After this interconnected row of contact members has been accommodated in the connecting strip the plate parts connecting the ends of the contact members are cut away. This method has a limitation in that it results in a large loss of material.

The primary object of the invention is to provide a connecting strip comprising a number of contact members which are insulated from one another, which strip can be manufactured with small tolerances, the loss of material in forming the contact members being very small. Due to these small tolerances which also permit the accurate piling of a number of connecting strips according to the invention so as to obtain a bank of contacts it is possible either while retaining definite dimensions to allow for more contact members in each row, or while retaining a definite number of contact members in each row to reduce the dimensions of the strip. This hired States Patent l ice 2 has the advantage that in a bank of contacts for a se-Y lector built up from such strips more contacts can be covered per unit of time without the mass forces produced by accelerating and arresting the brush carriage being increased. This is of particular importance in direct telephone systems, that is, systems without registers.

According to the invention the connecting strip consiste of a metal supporting strip comprising transverse bores in which lengths of metal wires projecting on both sides of the strip are centered by means of an insulating mass, for example polystyrene or some other synthetic resin.

Since the supporting strip is made of metal, in view of a light 'weight preferably of aluminum which may be anodized, it can be manufactured with very small tolerance. In addition, the connecting or contact members formed by the lengths of wire are all screened from one another electrically.

Preferably the insulating mass at the end of a bore is provided with a conical surrounding the length of wire centered in this bore to ensure a suicient creeping path.

To obtain firm anchoring of the lengths of wire in the insulating mass the parts imbedded in the insulating mass preferably comprise a tiattening or some other deformation.

The connecting strip according to the invention may be designed so that the parts of the contact members extending beyond the edge of the supporting strip are shaped in the usual hat form. This only requires the lengths of Wire to be flattened at one or both ends. As a rule this flattening can only be carried out after the attachment of the length of wire in the bores since othen wise the flattened parts prevent the lengths of wire from being introduced into the bores. If the dimensions of the flattened parts are such that the latter condition does not apply or if only one end of the length of wire is flattened, the attening may also be carried out before the lengths of wire are secured in the supporting strip, To ensure a great accuracy in the relative spacings of the fiat ends of the contact members preferably the fiattened ends of all the contact members arranged in the supporting strip are simultaneously punched to the desired size by means of a cutting tool. Locating holes or alternative means of alignment provided in or at the metal supporting strip allow this supporting strip and the cutting tool to be arranged in an accurately determined relative position Which may be reproduced for each supporting strip with the result that not only the Contact members of one connecting strip are at a correct relative position but also that the connecting strips ex hibit a high degree of similarity. The means of alignment may also be used to ensure a correct relative position of the strips when a number thereof are piled upon one another.

The invention will now be described with reference to one embodiment thereof given by way of example and shown in the accompanying diagrammatic drawing, in which Fig. 1 is a plan view of a first embodiment of a connecting strip according to the invention of which Figs. 2 and 3 show cross-sections taken along the lines II-II and III-III.

Fig. 4 is a cross-sectional View corresponding with that shown in Fig. 2 of a second embodiment of the connecting strip according to the invention.

Referring now to the figures, the connecting strip shown in Figs. l, 2 and 3 consists of a flat strip-shaped support 1 made of anodized aluminum and shaped in semi-circu lar form. This connecting strip is intended for use as a structural element for a bank of contacts of a rotary selector for use in automatic telephone systems. The strip l comprises a number of equally spaced bores 2 which are parallel with the plane of the strip and all I are directed to the center of' curvature thereof; Contact members constituted by lengths of metal wire 3 which project beyond the end of the supporting strip 1 on either side are arranged" in these bores.' The lengths of wire are centered in the bores 2 by means of a hard insulating mass 5, in this case polystyrene. The lengths of wire are anchored in the polystyrene in that the parts enclosed in the bores locally comprise a flat part l2. The insulating mass S in each bore is anchored with respect to the support l in that this mass ills not only the bore itself but also the transverse apertures 4 which act as charging holes for the insulating mass in manufacture. The polystyrene 5 which centers a length of 'wire 3` in a bore at the ends of the bore hasta bulge 6 which surrounds the length of wire conically and increases the creeping path between the supporting strip l and the length of wire.

Fig. 4 is a cross-sectional view or" a second embodiment of the connecting strip according to the invention. The difference from the embodiment shown in Figs; l, 2 and 3 is that no charging holes 4 are provided but the support l comprises a channel-shaped recess 13` which runs substantially throughout the length of the support and into which all bores 2 open. The insulating mass 5 also iills this recess and thus goes on at one side of the support.

Not all the contact members 3 arranged in the supporting strip l are shown in Fig. 1. Those shown are divided in three groups A, B and C which show the contact members 3 in different stages of manufacturing. As has been stated hereinbefore, in the embodiment shown all contact members arranged in the supporting strip in actual fact are shaped in the form indicated with respect to those of the group C.

The contact members 3 of group A consist of straight lengths of metal wire of identical cross-section throughout their length.

The contact members of group B consist of lengths of wire such as those in group A, both ends of the lengths, however, being ilattened. Thus flat end parts 7 and 8 are obtained which lie in one plane. The parts 7 and 8 may be formed previously to the insertion of the lenghs of wire in the supporting strip, however, it is simpler to insert lengths of wire like those of group A into the supporting strip first and then to flatten the ends of these lengths all together in one operation.

The contact members in the group C are shaped into their final form by punching the attened endsV of the lengths of wire secured in the supporting strip 1 (group B) to the correct size by means of a speciiically made cutting tool. The correct relative arrangement of the cutting tool and the connecting strip is obtained with theA aid of locating holes formed in the ends of the supporting strip l. In this punching operation the ends of the wire segments which are situated at the inner side of the strip are shaped into the form of substantially rectangular ilat contact planes l0 which are very accurately spaced and are intended to be swept by a brush in a selector, the bank of contacts of which is built up from such connecting strips. As may be seen at 9 this punching process causes the flattened ends 7 of the lengths of wire to be shaped so as to exhibit a profile which facilitates the attachment of connecting wires to these ends, for example by soldering.

In view of a satisfactory contact between the contacts 10 and thefbrush sliding thereon in a selector built up from a number of the described connecting strips it may be. desirable for the contact surfaces to consist of precious metal, for example palladium or silver. This `may be obtained by making that end of the length of some other manner a length of previous metal wire to 'g5 the lengths of wire consisting of base metal, for example brass; which are to be arranged in the bores 2 or by previously providing the ends concerned of these lengths of wire with a sheath of precious metal.

In the embodiment described the supporting strip l is semicircular so that the connecting strip may act as a structural element of a semi-cylindrical bank of contacts. However, the supporting strip may be shaped in a ditferentfo'rm, for example in a straight form so as to enable the strip to act as a structural element for a straight bank of contacts.

The connecting strip according to the invention may also' be used in a'diierentmanner than as a structural element for a Ibank. ofV contacts. It may, for example, be used as a distributing strip in telephone exchanges, as a mounting support for electric parts in an apparatus and as a connectingv strip for the energizing windings of an electro-magnetic relay. In relays the contact springs are usually gripped between insulating spacers which are mounted on a connecting strip which is secured to the yoke and comprises Contact members for the energizing coils. Due to tolerances in thickness in the connecting strip the contact springs do not always occupy the correct position with respect to the parts moving them which are coupled to the armature thereby necessitating adjustment of the contact springs. By the use of the connecting strip according to the invention which can be manufactured and reproduced with great accuracy of the aforesaid thickness this disadvantage is overcome.

While I have shown and described the preferred embodiment of my invention, it will be understood that the latter may be embodied otherwise than as herein specilically illustrated or described and that in the illustrated embodiment certain changes in the details of construction and in theV arrangement of parts may be made Without departing from the underlying idea or principle of the invention Within the scope of the appended claims.

What is claimed is:

l. A connecting strip for a bank of contact members insulated from one another comprising said connecting strip being integral and composed of metal and having a plurality of bores therein transverse to the longitudinal axis of said connecting strip and parallel with the plane of said strip, an insulating mass for permanently and precisely centering each of said contact members in said bore in such a manner that the ends of each of said contact members project beyond the adjacent side of said connecting strip.

2. A connecting strip as set forth in claim l wherein said strip is composedofaluminum.

3. A connecting strip forV a bank of Contact members insulated from one another comprising said connecting strip being integral and composed of metal and having a plurality of bores therein transverse to the longitudinal axis of said connecting strip and parallel with the plane of said strip, an insulating mass yfor permanently and precisely centeringeach of said contact members in said bore in such a manner that the ends of each of said contact members project beyond the adjacent side of said connecting strip, said contact members being lengths of Wire and said insulating mass at the end of each of saidbores being provided with a conical bulge surrounding the length of wire centered in each bore.

4. A connecting strip for a bank of contact members insulated from one another comprising said connecting strip being integral and composed of metal and having a plurality of bores therein transverse to the longitudinal axis' of said connecting strip' and parallel with the plane of said strip, an insulating mass for permanently and precisely'centering each of said contact members in said bore in such a manner that the endsfof each of said contact members project beyond the adjacent side of said connecting strip, said contactmembers being lengths of wire which are imbeddedfin the insulating mass, each of 5 said lengths of wire having one flattened end for attaching connecting wires thereto.

5. A connecting strip for a bank of contact members insulated from one another comprising said connecting strip being integral and composed of metal and having a plurality of bores therein transverse to the longitudinal axis of said connecting strip and parallel to the plane of Said strip, an insulating mass for permanently and precisely centering each of said contact members in said bore in such a manner that the ends of each of said contact members project beyond the adjacent side of said connecting strip, said contact members being lengths of Wire which are imbedded in the insulating mass, each of said wires having at one end a coating of precious metal, the other part of said Wire being a base metal.

6. A connecting strip for a bank of contact members insulated from one another comprising said connecting strip being integral and composed of metal and having a plurality of bores therein transverse to the longitudinal axis of said connecting strip and parallel to the plane of said strip, an insulating mass for permanently and precisely centering each of said contact members in said bore in such a manner that the ends of each of said contact members project beyond the adjacent side of said connecting strip, said contact members being lengths of wire imbedded in said insulating mass, and at one side of said connecting strip the ends of each of the lengths of Wire are flattened.

References Cited in the le of this patent UNITED STATES PATENTS 1,178,207 Baldwin Apr. 4, 1916 1,557,615 RichterA Oct. 20, 1925 1,595,107 Lyng Aug. 10, 1926 2,294,482 Siegmund Sept. 1, 1942 2,534,864 Fritts Dec. 19, 1950 FOREIGN PATENTS 197,486 Great Britain May 17, 1923 433,597 Germany May 2, 1924