US3350676A

US3350676A - Pinboard with ladder type contact springs

Info

Publication number: US3350676A
Application number: US453722A
Authority: US
Inventors: Mcfadden Bruce Richard
Original assignee: AMP Inc
Current assignee: TE Connectivity Corp
Priority date: 1965-05-06
Filing date: 1965-05-06
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31
Also published as: SE313357B; NL6605946A; GB1096082A; DE1565989A1

Description

I 061531, 1967 MCFADDEN 3,350,676

PINBOARD WITH LADDER TYPE CONTACT SPRINGS 2 Sheets-Sheet 1 Filed May 6, 1965 INVENTOR.

BRucE RKHAMS M FAbpeN BY M, m r W Oct. 31, 1967 R. MCFADDEN 3,350,676

PINBOARD WITH LADDER TYPE CONTACT SPRINGS Filed May 6, 1965 2 Sheets-Sheet 2 INVENTOR.

I LBRucE RK ARv MLFADDEN United States Patent 3,350,676 PINBOARD WITH LADDER TYPE CONTACT SPRINGS Bruce Richard McFadden, Harrisburg, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Filed May 6, 1965, Ser. No. 453,722 9 Claims. (Cl. 339-18) ABSTRACT OF THE DISCLOSURE A pinboard is disclosed for interconnecting electrical circuit paths by the insertion of a conductive pin selectively in a matrix of conductive spring members. The conductive spring members are of a ladder-like configuration wherein the rungs of the ladder define tie points for spring systems defined by the sides of the ladder. An insulating block is provided having apertures therein to receive conductive pins and grooves aligned with the apertures to house the conductive spring members. The spring members are made to be of a width less than the width of the grooves but greater than half of the groove width in order to eliminate tolerances and to assure the proper insertion of conductive pin members between the sidewalls formed by the ladder-like construction of the conductive spring members.

Background of the invention The pinboard represents a type multiple coordinate switch wherein selected interconnections are accomplished through the insertion of a conductive pin member between isolated contacts bussed to input and output leads. The usual construction includes a laminated insulating block structure designed to hold conductive strips carrying contact springs in isolated and intersecting relationship registered with apertures in the insulating block structure. The problem with most of the prior art devices is one of complexity which results in high manufacturing cost and poor reliability. Complexity arises by virtue of the need to maintain a large number of insulating and conductive components in rather exact alignment. For example, in a typical pinboard capable of permitting a selected interconnection of any one of ten input leads to any one of ten output leads it is necessary to provide 100 connection paths. In an accepted prior art pinboard construction this is accomplished through an assembly including four or more insulating boards containing some twenty conductive strips each having at least eleven separate contact springs (a total of 220) fixed within the boards such that the contact areas of the springs are in exact alignment with apertures for pin insertion in the board members. This means that considerable care must be exercised in the production of the various insulating and conductive components with respect to length, width and center-to-center spacing and considerable care must be exercised in assembly of these components to achieve the necessary registry of the parts. Close tolerances in manufacture and assembly means high relative cost and can mean poor overall reliability which is related to the performance of each component.

Summary of the invention This invention relates to a pinboard assembly of the type utilized to selectively interconnect electrical circuits.

Accordingly, it is one object of the present invention to provide a pinboard assembly which is inexpensive and yet reliable. It is another object of the invention to provide a pinboard construction utilizing a novel contact spring which substantially reduces the need to maintain close tolerances with respect to manufacture and assembly of pinboard devices. It is a further object of the invention to provide a new contact spring system for pinboards and like devices.

The present invention overcomes the foregoing problems and attains its objectives through an insulating board construction employing two identical board members which inter-digitate to captivate spring contact strips contained therein. The spring contact members are of a ladder like configuration wherein the rungs of the ladder define tie points for the spring systems defined by the size of the ladder. The contact spring members include further details to prevent scouring of the pins inserted therein and to further relieve tolerances of manufacture and assembly.

In the drawings:

FIGURE 1 is a perspective of a pinboard in accordance with the present invention having a corner thereof sec tioned to show interior construction;

FIGURE 2 is a perspective showing two of the contact members of the invention positioned as in use in the board of FIGURE 1 and having a die conductive pin inserted therebetween;

FIGURE 3 is a plan view, somewhat enlarged from actual size, showing portions of the contact member of the invention positioned within an insulating board member;

FIGURE 4 is a section taken through lines 44 of FIGURE 3;

FIGURE 5 is a section taken through lines 5-5 of FIGURE 3; and

FIGURE 6 is a sectional view of an alternative construction for the spring member of the invention.

Description of the preferred embodiment 09 the invention Referring now to FIGURE 1, the pinboard assembly is shown as 10 to include a pair of

insulating board members

12 and 14; at least the upper member containing an array of apertures 16. The board members are, for the purposes of illustration, fastened at each corner by rivets, screws or the like, shown as 18. Input leads are applied to the assembly 10 from the rear of the board or in some other suitable fashion and selected connections are accomplished by the insertion of pins such as 20; one being shown inserted in the board and one being shown positioned above the board for insertion.

The

boards

12 and 14 are identical and may preferably be from the same mold, if molded. Each of the boards includes a series of parallel grooves 12a separated by a series of parallel projections shown as 12b which carry further and integral projections 120. As assembled the groove projection faces of the board are disposed in face to face relationship and oriented at right angles so that the various grooves and projections of one board intersect the grooves and projections of the other board. Within each groove of the upper and lower board members is a contact spring like the

springs

26 and 28 shown in FIGURE 2 which held against lateral displacement by the projections 12b between grooves and held against transverse displacement by the further projections which extend from one board over into the other board to hold the spring members of that board in position.

As a preferred way of accomplishing the input and output connections the general board construction reference is made to copending US. application Ser. No. 441,700 filed Mar. 22, 1965 in the name of Winfield Loose.

With the

boards

12 and 14 properly oriented and assembled as indicated in FIGURE 1 insertion of a pin member 20 within an aperture 16 will result in an interconnection between one of the upper contact members such as 26 and one of the lower contact members such as 28; the connection being made through the conductive body of the pin member. The pins 20 may be considered as solid 3 members comprised of a conductive barrel 24 and an insulating handle 22 although it is contemplated that diode pins or live pins of the type described in the aforementioned Loose application may also be employed.

Each contact member is of the general configuration shown in FIGURE 2 with respect to contact member 26. The member includes sides of conductive metallic strip stock shown as 26a and 26b in open parallel relationship joined at the bottom by members 260. This structure forms a ladder arrangement wherein 26a and 261) are the sides and members 260 may be thought of as rungs. The sides 26a and 26b should have spring characteristics and various grades of brass or beryllium copper have been found suitable for this purpose. The contact members 26 are preferably formed in the flat from sheet stock material by stamping and blanking and then formed into the configuration shown and plated at least on the interior surfaces with an alloy adapted to provide a low resistance path and to prevent corrosion. In a typical construction both the pin barrel 24 and the

members

26 and 28 would be furnished with a standard gold over nickel plating.

Referring now to FIGURE 3, a contact member 26 is shown positioned in a groove 12a. As part of the invention the width W of the contact member relative to the width W of the groove is made such that there is considerable play between the member and the walls of the groove. This means that there is practically no criticality of tolerance as to the width of the spring member or as to the width of the groove. It is preferred to make W greater than /2 W so that no combination of tolerances or position of the contact member within the groove can result in the pin body 24 passing outside of the contact member sides rather than therebetween. In an actual unit made of stock 0.010 inch wherein W was equal to 0.178 inch, the interior width of the contact member 26 was made 0.080 inch (making W equal to 0.090 inch) and the aperture 16 was made to be 0.102 inch in diameter. The spacing between rungs 26c may be as shown as in FIGURE 3 by S to be approximately equal to the center-to-center spacing of the apertures 16 and the width of the body of the rungs should be sufiicient to adequately tie the sides 26a and 26b together and to form a point of contact for the projections 12c of the opposite board member which holds the contact members in position in the embodiment of FIGURE 3. These projections are shown in crosssection in FIGURE 3 by dotted lines to fit between the contact member sides and to overlap the rungs to eliminate tolerances in mating therewith. The thickness and material characteristics of the sides 26a and 26b in conjunction with dimension S establishes the resiliency of the spring system of the contact members and the axial force of insertion of the pin necessary to spread the sides. In an actual unit S was 0.450 inch and the sides were of 0.010 inch Phosphor bronze No. 4 stock which was 0.040 inch in width. In this regard it is considered to be important to have a spring force sufficient to define a low resistance path between the contact strips and the pin body but insufficient to cause inelastic stressing of the sides of the member or scouring of the contact surfaces. As will be apparent from FIGURE 3, the sides have an unstressed configuration as shown to the left relative to the aperture 16 having no pin inserted therein and a stressed condition shown to the right developed by the insertion of the body of 24c of the pin.

If desired, rungs may alternately be provided between each aperture with an appropriate adjustment in the thickness and hardness of the contact member stock to provide proper resiliency.

FIGURE 4 is an enlarged cross-section showing the preferred configuration of the sides of the contact member to be of two upstanding and substantailly parallel beams which may be deflected as indicated by the dotted line in a sense transverse to the longitudinal axis of the member. The upper and lower edges of each beam are preferably coined to define a radius shown as 26d and 262. This may be readily accomplished in the blanking operation by having the cutting die directed in movement or stroke to shear the metal downwardly on both edges of each side such that when the members formed into the position of FIGURE 4 the radii are left on the interior of the member. Through the provision of the radiused edges the insertion of the pin is faciliated, the surfaces tending to guide the pin and prevent damage to the contact surfaces. In an actual unit the radius was made approximately equal to 0.012 inch.

FIGURE 5 shows a section through the rung of the contact member 26 and in the embodiment of FIGURE 3 the rung will be seen to substantially intersect the side members and to lay flat along the bottom of the groove 12a. FIGURE 6 shows an alternative embodiment which with respect to the groove 12a and the aperture 16 is identical to the embodiment of FIGURE 4. The side members of the contact members shown as 26' are also similar to the embodiment shown in FIGURE 4 but the rung includes a tab indicated by 27 displaced upwardly from the floor of 12a and there are projections 26d provided to aid in centering the member. The projection 12c employed to hold the contact member 26 in position is made of a length to engage the projection and hold the contact members resiliently in a downward sense. This serves to provide an additional relief against tolerances since the projections may vary from a point of light engagement with the tabs 27' to a length approximately equal to the displacement of a tab to a flat position along the floor of the groove.

Having thus described my invention I now define it in the appended claims.

What is claimed is:

1. In an assembly for selectively interconnecting electrical circuits, an insulating block structure having rows of transverse apertures therein, a series of conductive pin members adapted to be inserted in said apertures, a plurality of grooves within said block structure generally aligned with the rows of apertures and of a given width, a conductive contact member in each groove including a pair of fiat strip side members of spring material extending along the groove length, said side members having in terior facing contact surfaces in substantially parallel relationship normal to the axis to the said apertures so as to receive a pin member inserted therebetween, means joined to said side members at spaced points along the length thereof for holding said members and said surfaces spaced apart by a distance less than said given width but greater than one-half said given width and less than the said apertures to provide resiliency to said side members by providing spring beams between said points and assure pin member insertion between said surfaces.

2. The assembly of claim 1 wherein said means is comprised of a series of rungs disposed at right angles to said side members, said rungs being positioned in said grooves between said apertures.

3. The assembly of claim 1 wherein said means is comprised of rungs disposed along the length of the contact member between the said apertures, said rungs being integral with the material of each side member.

4. The assembly of claim 1 wherein said side members are radiused at the top and bottom edges to prevent scouring of a pin member during insertion and withdrawal in said assembly.

5. The assembly of claim 1 wherein said block structure is comprised of a pair of insulating boards each having rows of transverse apertures therein and each having said plurality of grooves therewithin, the said boards being arranged with the grooves thereof at right angles, each board including bordering the grooves thereof a projection extending into the groove of the opposite board to hold the contact member therein against transverse movement relative to said assembly.

6. The assembly of claim wherein said means includes a projection adapted to engage the projection of said boards.

7. In a pinboard assembly of the type utilized to selectively interconnect electrical circuits, a pair of boards of insulating material each including a plurality of rows of apertures transverse to the major surface of the board, a plurality of parallel grooves of a given width generally aligned with the board apertures, and a plurality of first projections between said grooves and continuous therewith, each board further including a plurality of second projections extending from said first projections and noncontinuous along the length of said first projections, a contact member in each groove comprised of a pair of sidewalls each defined by a fiat strip of conductive material and having the interior surfaces thereof in spaced and substantially parallel relationship extending continuously along said grooves, the said sidewalls being held by rung portions at points spaced along the length thereof to define spring beams between said rungs formed of the material of said sidewalls, the said sidewalls being spaced apart by .a distance less than the said given width of said grooves and less than the diameter of said apertures whereby the insertion of a conductive pin member in said apertures will engage the interior surfaces of said sidewalls under a spring force developed in said sidewall, the said second projections extending between said sidewalls to engage the said rungs between said apertures and hold said contact members in position in said pinboard.

8. In a pinboard assembly of the type adapted to be utilized to selectively interconnect electrical circuits comprising an insulating block structure having rows of apertures extending transversely therethrough adapted to receive conductive pin members, a plurality of grooves within said block structure, each groove being aligned with a row of apertures and of a width greater than the diameter of said apertures, a contact member disposed in each groove formed of flat strip conductive material having spring characteristics, the said contact member including parallel sides extending along said grooves, said sides being held by rungs disposed at points along the lengths of said contact member and spaced apart by a distance less than the diameter of said apertures but greater than onehalf the width of said grooves so that at least one side wall of said contact member is always secant to a said aperture.

9. The assembly of claim 8 wherein projections are included extending out from said sides to engage the walls of said grooves and center said contact members in said grooves.

References Cited UNITED STATES PATENTS 2,251,403 8/1941 Frank et al 33922 2,922,135 1/1960 Hoberg et a1. 339-18 3,027,534 3/1962 Deakin 33918 3,170,745 2/1965 Deakin 33918 3,245,024 4/ 1966' Evans 33917 FOREIGN PATENTS 893,066 10/1953 Germany. 896,105 5/1962 Great Britain.

MARVIN A. CHAMPION, Primary Examiner. PATRICK A. CLIFFORD, Assistant Examiner.

Claims

1. IN A ASSEMBLY FOR SELECTIVELY INTERCONNECTING ELECTRICAL CIRCUITS, AN INSULATING BLOCK STRUCTURE HAVING ROWS OF TRANSVERSE APERTURES THEREIN, A SERIES OF CONDUCTIVE PIN MEMBERS ADAPTED TO BE INSERTED IN SAID APERTURES, A PLURALITY OF GROOVES, WITHIN SAID BLOCK STRUCTURE GENERALLY ALIGNED WITH THE ROWS OF APERTURES AND OF A GIVEN WIDTH, A CONDUCTIVE CONTACT MEMBER IN EACH GROOVE INCLUDING A PAIR OF FLAT STRIP SIDE MEMBERS OF SPRING MATERIAL EXTENDING ALONG THE GROOVE LENGTH, SAID SIDE MEMBERS HAVING INTERIOR FACING CONTACT SURFACES IN SUBSTANTIALLY PARALLEL RELATIONSHIP NORMAL TO THE AXIS TO THE SAID APERTURES SO AS