US3281763A - Contact assembly means and method - Google Patents

Description

Oct. 25, 1966 CROWLEY ETAL 3,281,763

CONTACT ASSEMBLY MEANS AND METHOD Filed April 24, 1964 2 Sheets-Sheet 1 INVENTORS DAM\E.L QQSEPH CRcwLl-IY CHARLES Ream- SAuveRs aualdl,

Oct. 25, 1966 D, CROWLEY ETAL 3,281,763

CONTACT ASSEMBLY MEANS AND METHOD 2 Sheets-Sheet 2 Filed April 24, 1964 NlCKEL.

PLATE GOLD PLATE FLUX ASSEMBLY UN FLOW TIN FAT STODDARD'S SOLVENT WASH INVENTORS DANIEL JOSEPH CROWLEY YCHARL as 'RoBER-r SANvs e B United States Patent 3,281,763 CONTACT ASSEMBLY MEANS AND METHOD Daniel Joseph Crowley, Steelton, and Charles Robert Sanders, Harrisburg, Pa, assignors to AMP Incorporated, Harrisburg, Pa.

Filed Apr. 24, 1964, Ser. No. 362,316 10 Claims. (Cl. 339-417) This invention relates to an improved contact assembly and method of manufacture which features a new type of mechanical connection between assembly components to provide superior electrical and mechanical characteristics.

In US. Patent 2,975,395 to G. C. Sitz, granted Mar. 14, 1961, there is described a plugboard device of the type used to program electrical and/ or electronic equipment. Part of the contact system of the plugboard assembly shown and described in the Sitz patent is formed of a stamped metal spring member which carries a contact surface on a forward spring portion and includes a support portion adapted to position and hold the member within an insulating board. This support portion further includes a receptacle adapted to receive a taper pin connected to a lead which is, in turn, connected to equipment to be programmed by the plugboard device. The arrangement featured in the Sitz patent has proven to be quite adequate for standard uses and normal environment. In certain applications, however, it has been found advisable to employ a relatively heavy solid metal seamless receptacle into which the taper pin member is plugged. Efforts were made to utilize the spring construction shown in the Sitz patent in such uses with the solid metal receptacle being inserted within the support portion and soldered thereto. A number of deficiencies with this construction developed. One of the principal problems appeared to be related to the incompatibility of standard solder and solder-flowing methods with the base metal and plating material used for the contact spring. Another problem developed due to the insertion and withdrawal forces required by the taper pin which caused displacement of the metal receptacle relative to the support portion and thereby mechanical and electrical failure of the assembly. The foregoing shortcomings were particularly objectionable because the failure most frequently arose after some period of use and well after initial tests showed satisfactory mechanical orelectrical characteristics.

The foregoing problems led to the discovery upon which the present invention is based. As will become apparent from the description hereinafter to follow, it is a general object of the invention to provide a new and improved contact assembly wherein a relatively heavy solid metal member is mechanically and electrically joined to a relatively thin metal member and it is a particularobject to provide a plugboard contact spring assembly having a heavy metal taper pin receptacle secured thereto in a manner to withstand the insertion and withdrawal forces associated with taper pin techniques. It is a further object of the invention to provide a novel method of manufacturing an assembly wherein a relatively heavy metal member is joined to a relatively thin metal member through the combined use of what might be termed soldering and crimping techniques. It is another object of the invention to provide a method of joining metal members in a manner providing a low resistance stable electrical path with a sound mechanical connection. It is yet another object of the invention to provide a novel means and method for connecting metal members which must be thereafter overplated with metals of different characteristics.

In the drawings:

FIGURE 1 shows the contact assembly of the invention in plan secured in an insulating board member sectioned 3,281,763 Patented Oct. 25, 1966 for clarity and with a taper pin positioned relative to use with the assembly;

FIGURE 2 is an enlarged side view of the support portion of the contact assembly of the invention showing the taper pin receptacle secured therein;

FIGURE 3 is an end view taken along the lines 3-3 of FIGURE 1;

FIGURE 4 is an enlarged side view of the contact assembly of the invention showing the crimp employed therewith to lock the taper pin receptacle within the assembly;

FIGURE 5 is a partial section taken along lines 5-5 of FIGURE 4 to show further details of the crimp employed with the invention; and

FIGURE 6 is a block-step diagram showing the method of the invention.

In FIGURE 1, the taper pin 10 is shown relative to insertion within the contact assembly of the invention which is mounted in an insulating board 22. The taper pin 10 includes a forward contact portion 12 tapered along its surface to engage and be wedged against a complementary surface 42 within a taper pin receptacle 40 which is part of 20. The pin is connected to a lead 14 as by a crimp 16 through an insulating sleeve 18. The lead 14, or many leads similar thereto, may be connected to components of electrical and/or electronic equipment served by the plugboard which includes dozens or hundreds of contact assemblies, such as 20. The assembly 20 carries a flexible contact spring 24 which is adapted to engage a pin member 25 extending from a movable board (not shown) of the plugboard assembly. The contact system formed by these parts serves to make or break electrical paths through and between leads such as 14, the assembly 20, spring 24, pin 25, and an identical and similar combination of elements elsewhere in the plugboard. Reference may be had to the aforementioned patent to Sitz for a general description of plugboard systems.

The forces which the assembly 20 must carry in use include a transverse force developed by reason of spring 24 being deflected by pin 25 and an axial force along the center line due to the insertion and withdrawal of taper pin 10. The assembly is locked against the transverse force by reason of the engagement of a support portion 26 with the aperture surface 21 of board 22. The axial forces which tend to pull or push assembly 20 out of the aperture are resisted by means of tabs, such as 28, struck outwardly to engage the surface of board 22 as indicated, in conjunction with the inner transverse surfaces of spring members formed on the opposite end of the assembly.

The contact assembly 20 is initially inserted within board 22 by forcing the end-carrying springs 30 into the aperture and forcing the assembly along the aperture until the tabs 28 engage the surface of the board. Thereafter, the springs 30 are formed outwardly to lock the assembly within the :board. In the embodiment shown, the assembly 20 is formed of a fiat metal material, such as sheet brass, blanked, stamped and formed into the configuration shown. The assembly support portion 26 is generally cylindrical and includes a seam 27, as shown in FIGURES 1 and 3. At the end of 26, proximate springs 30, portions of the support portion shown as 32 are formed inwardly to lock against the surface of taper pin receptacle positioned generally within the support portion as best shown in FIGURES 2 and 3. The portions 32 serve to orient 20 in the panel through cooperation with a portion protruding into aperture 21 and to retain member 40 against rotational movement relative to the contact assembly 20 by means of engagement with a fiat 44 extending along the length of the receptacle.

As can be seen from FIGURES 2 and 3, the exterior surface configuration of 40 is dimensioned to fit tightly Within the interior surface configuration of 20. In this regard, the seam 27 is utilized by an appropriate choice of dimensions to assure tight engagement of 20 and 40 by providing a small space between the edges along the seam to permit the receptacle to be wedged within 20 notwithstanding a slight oversize. The slots 31 and 33 are provided to permit the forming of portions 32 inwardly to lock receptacle 40 Without affecting the portions 34 or the springs 30.

The taper pin receptacle 40 is positioned in 20 with the taper bore forming surface 42 having its point of entry 46 as shown in FIGURE 2. The receptacle further includes the flat 44 above-mentioned and at the end opposite entry 46 an annular recess 48. It is through this recess that receptacle 40 is locked against axial movement relative to 20 by reason of crimps or indentations formed in the wall of portion 26. It will be appreciated that relative movement between 20 and 40 would cause a substantial increase in the resistance of the path through member 20. Relative movement between these two members could, but for the features to be explained, be occasioned by axial loads imparted during the insertion or withdrawal of taper pin or by forces imparted by spring 24.

As an important part of the invention, the member 40 is looked through the provision of indentations shown as 50 and 52 in FIGURE 1 which serve to force the metal material of support portion 26 down within the annular recess 48 of member 40. FIGURES 4 and 5 show these indentations in greater detail. From FIGURE 4, the indentation 52 can be seen to be formed of relatively straight sides 54, 56 which are spaced such that the width of the metal formed inwardly is substantially as wide as the recess 48. The body of metal is shown as 60 and is formed inwardly to contact the bottom of recess 48 as indicated by number 58, FIGURE 5. The configuration of the die which forms the indentation 52 can be visualized from the dotted outline and from the resulting indentation. As should be apparent from FIGURES 4 and 5, this results in a shearing of the metal material .along sidewalls 54, 56 with a bending of the metal material as in 62 about a radius which is controlled to avoid cracking or splitting of the metal material.

In a preferred embodiment, the indentations 5t) and 52 are formed 180 apart and the width, in an axial sense, is made to be slightly larger than the width of the recess 48 such that the material of the bend 60 is virtually wedged in compression down Within the recess and an abrupt surface is formed to hold against axial loading. This, in conjunction with portions 32, locks the receptacle 40 against rotational movement in addition to locking against axial movement. As shown in FIGURE 2, and as will be better described hereinafter, with respect to the method of the invention, there is included between member and the member 40 a coating of tin solder bonding the two members together to form a low-resistance electrical path therebetween. The flowing of the tin is accomplished following the crimping operation and both the crimping and flowing are accomplished prior to any final plating operation.

The assembly, thus described, has been found to withstand axial loads of 400 pounds and better with excellent electrical characteristics maintained through standard life tests. In an actual embodiment wherein the assembly 21 was formed of brass stock of approximately 14 thousandths of an inch in thickness and the axial depth of indentation 52 was 20 thousandths of an inch. In this embodiment, the axial width between surfaces 54 and 56 was 68 thousandths of an inch whereas the width of recess 48 was 63 thousandths of an inch to provide the abovementioned wedging action.

In manufacturing the assembly of the invention abovedescribed, the preferred method is as indicated in the step-block diagram shown in FIGURE 6. The method contemplates prior to the first step that members 40 and 20 are separated as indicated in FIGURE 6. The contact assembly 20 is at this point unplated and uncrimped. The receptacle 40 is coated with tin along the portions of its exterior surface as indicated by the heavy line in FIGURES 2 and 3. It is preferred to prepare by screw-machining a solid brass rod which has been previously tin plated.

With the contact spring 20 and receptacle 40 in the above-descrived states and cleaned, the receptacles are then fluxed, as for example, by being briefly submerged in a fiuxing solution such as 48 percent WW rosin and 52 percent denatured alcohol (by weight) and then permitted to dry.

Next, the fluxed receptacle is inserted in the contact spring in the relative position shown in FIGURES 1 and 2 and crimped or indented in the manner abovedescribed with respect to portion 32 and indentations 52.

Thereafter, the assembly of 20 and 40 is then treated to achieve tin flow between the contact assembly by submerging in a preheated tank containing Hydrofol Tinfat No. at approximately 500 F.i10 F. for a period of five minutesione minute. This operation serves to flow the tin between the surfaces of 20 and 4t) and thus, solder the two pieces together through the tin medium. Thereafter, the assembly is withdrawn from the Tinfat and dumped for cleaning in Stoddards solvent which removes excess Tinfat from the members.

Thereafter, a suitable plating such as gold over nickel may be applied to the contact assembly in standard fashion.

The foregoing method has been found to provide an electrical connection between the receptacle 40 and spring 20 which is superior to techniques heretofore attempted. The method of crimping or indenting prior to the soldering operation in conjunction with the particular type of soldering operation has been found to substantially improve the mechanical characteristics of the piece and assure long life in the presence of adverse environments. The method has been found to be particularly compatible with overplating after crimping and soldering.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be define-d in the following claims when viewed in their proper perspective against the prior art.

What is claimed is:

l. An electrical contact assembly including a barrel portion and a contact portion integral with said barrel portion, the said barrel and contact portions being of relatively thin fiat metal stock of the type adapted for ease of stamping and forming with the contact portion having spring characteristics, a contact receptacle of relatively heavy metal stock secured in said barrel portion and adapted to receive a contact member inserted therein, the receptacle having on a portion of the outer surface a thin layer of conductive material to electrically connect the receptacle to the barrel portion, the receptacle further having a recess and being secured in said barrel portion and electrically connected thereto by at least one indentation of the outer surface of said barrel portion forced into the recess of the said receptacle.

2. The assembly of claim 1 wherein the layer of conductive material is a metal having a relatively low melting point.

3. In a contact assembly of the type utilized in a plugboard, the combination including a contact member formed of relatively thin metal stock having a mounting portion adapted to lock said member within a plugboard aperture and a forward spring portion which is resiliently flexible to receive and be held in contact with a patch- Cofd pm under Substantial pressure, the mounting portion including'at the opposite end to said spring an opening adapted to receive a taper pin member therein, a solid metal receptacle fitted within said mounting portion to receive said taper pin through said opening, said receptacle including in the outside surface thereof a recess extending annularly at least around part of said receptacle, the said mounting portion having a segment formed inwardly into said recess to lock said receptacle against relative movement caused by forces developed during insertion and withdrawal of the taper pin in said receptacle.

4. The assembly of claim 3 wherein the said mounting portion egment formed inwardly into said recess includes at least one .wall section defining a surface substantially perpendicular to the longitudinal axis of said receptacle and the said receptacle recess includes a surface substantially perpendicular to the longitudinal axis of said receptacle, the said surfaces being in contact to lock against relative axial movement.

5. The assembly of claim 3 wherein the said segment formed into the receptacle recess includes two spaced surfaces substantially perpendicular to the longitudinal axis of the receptacle and said recess include complementary surfaces substantially perpendicular to the longitudinal axis of the receptacle, the said surfaces of the segment and recess acting to resist axial movement between receptacle and contact member.

6. The assembly of claim 5 wherein the axial spacing of the recess surfaces relative to the axial spacing between segment surfaces is such that the material of the segment is wedged under residual compression in said recess.

7. An improved method for forming a mechanical and electrical connection between a relatively heavy stock metal receptacle and the barrel portion of a contact member of relatively flat thin metal stock comprising providing a coating of metal material having a relatively low melting'point over a portion of the surface of the receptacle, placing said receptacle within said barrel portion, applying a crimp to said barrel portion to force the material thereof into engagement with said receptacle and heating said member and receptacle to a temperature and for a period of time to flow the metal material between the receptacle and contact member.

8. The method of claim 7 wherein the method step of heating consists of submerging the receptacle and contact member in a substantially neutral oil at a temperature of more than 375 9. The method of claim 8 wherein there is a further step including submerging the assembly while heated in a solvent to wash and remove the said oil.

10. In a contact assembly of the type utilized in a plugboard, the combination including a contact member formed of relatively thin metal stock having a mounting portion adapted to lock said member within a plugboard and a forward spring member which is resiliently flexible to receive and be held in contact with a. patchc-ord pin member, the mounting portion including at the opposite end of said spring an opening adapted to receive a connector terminal, a metal receptacle fitted within said mounting portion to receive said terminal through said opening, the said receptacle having a recess extending in annular fashion about a portion of its surface and including surfaces substantially perpendicular to the longitudinal axis of the receptacle and spaced apart by a given distance, said mounting portion having two segments spaced substantially apart and forced inwardly into said recess, the said segments having a width relative to the surfaces of the recess such as to be held under residual compression therein, the assembly further including extending between a substantial portion of the outside surface of the receptacle and a complementary inside surface of the mounting portion, a layer of conductive material fused to the metal material of the receptacle and mounting portion whereby the receptacle and mounting portions are mechanically and electrically joined to receive and bear the stresses of insertion and withdrawal of the terminal and flexure of the forward spring portion in use.

References Cited by the Examiner UNITED STATES PATENTS 1,575,656 3/1926 Stratford et al 339276 1,920,791 8/1933 Hogan 29470.5 2,405,111 8/1946 Carlson et al 339-276 X 3,100,330 8/1963 Rice et a1 29502 X 3,140,141 7/1964 Nava 339256 3,189,868 6/1965 Hatfield 339217 X FOREIGN PATENTS 643,627 9/ 1950 Great Britain.

EDWARD C. ALLEN, Primary Examiner. P. A. CLIFFORD, Assistant Examiner,

Claims (1)

1. AN ELECTRICAL CONTACT ASSEMBLY INCLUDING A BARREL PORTION AND A CONTACT PORTION INTEGRAL WITH SAID BARREL PORTION, THE SAID BARREL AND CONTACT PORTIONS BEING OF RELATIVELY THIN FLAT METAL STOCK OF THE TYPE ADAPTED FOR EASE OF STAMPING AND FORMING WITH THE CONTACT PORTION HAVING SPRING CHARACTERISTICS, A CONTACT RECEPTACLE OF RELATIVELY HEAVY METAL STOCK SECURED IN SAID BARREL PORTION AND ADAPTED TO RECEIVE A CONTACT MEMBER INSERTED THEREIN, THE RECEPTACLE HAVING ON A PORTION OF THE OUTER SURFACE A THIN LAYER OF CONDUCTIVE MATERIAL TO ELECTRICALLY CONNECT THE RECEPTACLE TO THE BARREL PORTION, THE RECEPTACLE FURTHER HAVING A RECESS AND BEING SECURED IN SAID BARREL PORTION AND ELECTRICALLY CONNECTED THERETO BY AT LEAST ONE INDENTATION OF THE OUTER SURFACE OF SAID BARREL PORTION FORCED INTO THE RECESS OF THE SAID RECEPTACLE.

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