US 3120988 A
Description (OCR text may contain errors)
Feb. 11, 1964 L. GILBERT BELLOWSTYPE comer CONSTRUCTION 3 Sheets-Sheet 2 Filed May 25. 1962 INVENTOR. 1:0 6/1857?! FIG. 8
y JITOR/VEKS Feb. 11; 1964 L. GILBERT 3,
BELLOWS-TYPE CONTACT CONSTRUCTION Filed May 25, 1962 3 Sheets-Sheet 3 I I i: l A a I I I I INVENTOR. IO/V G/ZBA'RI' United States Patent ()fifice 3,l2,%88 Patented Feb. ll, 1%64 i. sa s-no The present invention relates to a bellows-type contact construction, and more particularly one which minimizes resistance and inductance effects arising within the contact structure.
My Patent 2,875,425 of February 24, 1959, entitled Multiple Electrical Connector, is assigned to the assignce of the instant patent. it discloses a multiple electrical connector, particularly of the miniature type, which comprises a jack or receptacle designed to receive printed circuit cards or plug The receptacle is provided with multiple miniature contact elements which engage with mating terminal .portions on the printed circuit card or plug when the latter is inserted into the receptacle. The aforementioned Patent 2,875,425 featured miniature contact elements in the receptacle which were i iade of strip spring stock, and were constructed to act as compressio springs, more particularly bellows-type compression springs. The bellows-shaped part of those contact elements was formed of a plurality of branches or sections, the outermost of which was adapted to make contact with the circuit element or contact of the printed circuit card or plug, that outermost section or branch being electrically connected to the terminal portion of the contact by means of an intermediate branch or section and an inner branch or section, those two sections being serially electrically connected between the outermost or contact sccion land the terminal portion.
T his bellows-type construction has proved to be highly satisfactory, and has been adopted quite widely. One of the fields in winch it has proved to be most advantageous is in connection with electronic computers, where different printed circuit cards are adapted to be used depending upon the part .iular type of comcutation desired. In applications of this tyne the signals are often very weak, or function at a high frequency, or both. With weak signals voltage drop is to be avoided, since any such voltage drop results in undesired attenuation of the signal. This vol age drop can arise either by virtue of the contact resistance at the interface between the bellows contact and the terminal portion on the printed circuit card, or by virtue of ohmic losses as the signal passes along the contact unit itself from the outermost branch or section to the terminal portion thereof. The current ath in the contact also gives rise to undesirable inductive effects, particularly when, as is the case the hello s-tyne contact, that current path is tortuous. These inductive effects become more and more troublesome as the effective frequency of the signal increases.
It is the prime object of the present invention to devise a bellows-type contact arrangement which has all of the advantages of the devices isclosed in my Patent 2,875; 425, and ah has the further advantages that voltage drop and inductance effects are greatly minimized when compared with the construction shown in hat patent.
This obiective is achieved by retaining the basic bellowsshape and bellows-action of the contact units, while at the same time reducing the length and tortuo ,ty of the electrical path which the signal must travel through the contact. The structure employed to accomplish this rcsuit has the added advantage of increasing the firmness and reliability of the engagement between the outermost branch or section of e contact unit and the mating conductive portion of the printed circuit card or plug inserted into the receptacle in which the contact units are mounted.
More specifically, the terminal portion of the contact is provided with a conductive element which resiliently engages either the outermost branch of the contact unit or the intermediate branch thereof, preferably adjacent the lower end of the engaged branch, thereby defining a direct conductive path between the terminal portion of the contact and the outer branch thereof, through which path the signal can flow. This in eifect electrically short circuits the innermost and intermediate branches or sections of the contact assembly, those sections still functioning, however, to provide the desired bellows-action. The resilient force exerted by the newly added conductive element acts on the outermost bran h or section of the contact to urge it to firm and reliable connection, both physical and electrical, with the mating terminal portions on the printed circuit card or plug.
To the accomplishment of the above, and to such other objects as may hereinafter appear, the present invention relates to the construction of the bellows-type contact and the multiple electrical connector in which it is employed, as defined in the appended claims and as described in this specification, taken together with the accompanying drawings, in which:
H6. 1 is a three-quarter perspective view of a multiple electrical connector made according to the present invention and shown in combination with a printed circuit plug assembly, with parts shown in cross-section;
FIG. 2 is a front p ers ec'ive view of the multiple electrical connector with the contract units in slace;
FIG. 3 is a View shown to an enlarged scale corresponding to the cross sectional part of FIG. 1 of the drawings, but with the printed circuit plug assembly removed, and
illustrating one embodiment of the contact construction of the present invention;
FIG. 4 is a view similar to FIG. 3, but showing a typical printed circuit plug assembly in iposition;
FIG. 5 is a View similar to FIG. 3, but illustrating a second contact construction;
PEG. 6 is a view similar to FlG. 5, but with the printed circuit plug assembly in place;
PEG. 7 is a front elevational view of the contact unit of FIG. 5 taken in the direction of the line 7-7 of FIG. 5;
FIG. 8 is a view similar to FIG. 5' but showing a third embodiment of the contact construction;
FIG. 9 is a view similar to PEG. 8, but with the printed circuit plug assembly in place;
FIG. 10 is a front elevational View of the contact unit of FIG. 8, taken in the direction of the line lib-lb in FIG. 8;
FIG. 11 is a view similar to FIG. 5 but showing a fourth embodiment of the spring unit;
FIG. 12 is a view similar to FIG. 11, but with the printed circuit plug assembly in place; and
FIG. 13 is a front elevational view of the contact unit of FIG. 11, taken in the direction of the line 13ll3 of FIG. 11.
Referring now more in detail to the drawings, and having reference first to FIGS. 1 thereof, the multiple electrical connector comprises a jack assembly generally designated I and ada nted to receive a printed circuit plug assembly P or any like plug assembly, the said jack assembly I being provided with a plurality or series of miniature contact elements 0, the printed circuit plug assembly P being provided with a plurality of circuit elements or strips c the terminii of which define terminal elements for mating cooperation with the contact elements 0 of the jack assembly I.
The jack assembly 3 comprises a receptacle ill made of a single molded piece of insulation formed with a central longitudinal trough 12 for receiving the plug assembly P, the said trough being defined by two op ositely facing walls 14- and to, at least one and preferably both of which walls are formed with a plurality of pockets 18, 18 spaced along the trough 12 and corresponding in number to the number or" contact elements 0, each contact element being located and partially housed by a pocket 18. The walls 14 and 16 form the inside walls of said pockets 18, the side walls of said pockets being defined by ribs 20 directed inwardly of said walls. The receptacle M9 is also formed at its top with shoulders 22 extending the length of the trough 12, and with a boss or protuberance 24 at its bottom also extending the length of the trough 12, for purposes that will appear hereinafter. The receptacle Ml may also be rorrned with terminal lug portions 26 for the reception of attaching elements.
Each of the contact elements 0 comprises a bellowsshaped spring unit made from strip spring stock such as spring tempered Phosphor bronze (which may be gold plated over silver for obtaining low contact resistance), and having three branches or sections, an innermost section 28 being lodged against the inside wall such as the wall 14 or 16 of a pocket 18, an outermost branch 39 defining the contact which is engageabie by the mating terminal strip 0' of the plug assembly P, and an intermediate branch or section 32 forming a spring connection between the other two branches 2% and 30. The lower end of the innermost branch 28 of each bellows-shaped contact c is anchored in some appropriate manner to the body of the receptacle it), as by means of the struck out portion 34 located eXteriorly of the receptacle 10, and the ends 36 protruding from the receptacle 1t) and extending up into the pockets 1S define terminal ends to which conductors may be connected, as by soldering. The outermost branch or section 1% of the contact c terminates at its upper end in a hook portion 38 which is engaged by and over the shoulder wall 22, the end of the hook portion 38 having a limited freedom of movement in a recess 44) formed between said shoulder wall 22 and the outer walls 4-2 of the receptacle. The wall shoulder 22. forms a stop for limiting the outward movement (into the trough 12) of the top of the contact elements 0, and the boss 24 forms a stop for limiting the outward movement of the bottom of the contact elements 0.
When a printed circuit card P having a thickness no greater than the distance between the facing ribs 24) is inserted into the trough 12 of the receptacle 10, engagement is made at once between a terminal element c and the top of the outermost branch or section 3b of the contact element 0, this branch pivoting about the lower bend b of the contact element. As the plug P is moved further into the trough 12 this action continues, together with a pivoting of the intermediate branch or section 32 about the upper bend b of the contact element. As the plug P is forced into its home position the contact 0, in its action as a bellows, is compressed, the contact 0 also acting as a whole as a compression spring. The result is that the electrical engagement section of the contact element c, which is preferably linear in configuration, makes contact over substantially its full face or area with the mating terminal element 0' of the printed circuit plug P. With the compression spring bellows contacts 0, 0 arranged as pairs on oppositely facing sides of the connector, the further result is achieved that the circuit card or plug assembly P is accurately held resiliently in the receptacle it) by the oppositely acting compression action of the contact element pairs 0, c. The bellows sections, moreover, makes the face of the contact section 39 follow the printed circuit, preventing circuit discontinuity under severe vibration and printed circuit board misalignment.
The description thus far relates to the basic bellowstype contact construction and mounting as disclosed in Patent 2,875,425. In the construction as thus far described the signal, in passing through the contacts 0, flows along the following elements in series: terminal portion 4 It is satisfactory for many applications, but presents voltage drop and inductance complications for weak and very high frequency signals respectively.
In order to eliminate this disadvantage, and as disclosed in FIGS. 3 and 4, the terminal portion 36 is provided at its upper end with a conductive element 44 the lower end of which is engaged with what may be considered as the upper end of the terminal portion 36. The upper and free end of the conductive element 44 engages and bears against the intermediate contact section 32, preferably adjacent the lower end thereof. The conductive element is physically interposed between the contact sections and 32. More specifically, in this particular embodiment, the terminal portion 36 is formed of two parallel parts 36a and 361), connected by integral reverse bend as, the terminal part 36a being connected to the inner contact section 28 and the terminal part 36b carrying the conductive element 44 at its upper end. If desired, in order to assist in the vertical location of the con tact c within the receptacle it an ofiset portion 48 may be interposed between the conductive element 44 and the upper end of the terminal part 36b, that offset portion cooperating with a correspondingly oriented wall 50 formed at the bottom of the pocket 18.
When the printed circuit P is removed from the jack 1, as illustrated in FIG. 3, the conductive element 44, by virtue of its resilient action on the contact section 32, will urge the bellows contact 0 to expanded position. When a printed circuit plug P is inserted into the trough 1 2, as illustrated in FIG. 4, the bellows contact 0 will be compressed in bellows fashion. The conductive element 44 will constitute a direct conductive path between the lower end of the intermediate contact section 32 and the terminal portion 36, so that the signal will not have to traverse the contact sections 32 and 23 or the reverse bend b connecting those sections. This shorter and more direct path for the signal reduces voltage drop within the contact c and minimizes inductive problems. Moreover, the resilient action of the conductive element 44- tends to urge the lower ends of the contact sections 32 and 30 toward the printed circuit plug P, thus aiding in the attainment of firm electrical connection between the contact c and the mating terminal strip c. This reduces voltage drop at the contact interface and improves the reliability of the contact thus made in the presence of shock or vibration.
The embodiment of FiGS. 5, 6 and 7 is in many respects similar to that of FIGS. 3 and 4, and similar parts have similar reference numerals applied thereto. The contacts in FIGS. 6 and 7 differ from those in FIGS. 3 and 4 in that the outer contact sections 3th! are bifurcated by slot 52, and the intermediate contact sections 32a are bifurcated by slot 54-. The lower portion of the slot 54 in the intermediate contact section 32a is widened at 56. The conductive element 44a is composed of laterally outer portions 58 and a central tongue 63, the Width of the tongue ot being less than that of the widened slot portion 56 and greater than that of the slot 52 in the outer contact section 3%. The laterally outer portions 58 of the conductive element 44a engage those portions or" the intermediate contact section 32. on either side of the slot 56, while the tongue 6h passes through the slot 56 and engages the lower portions of the outer contact section Ella, spanning the slot 52. This construction provides parallel paths for the signal through the tongue es and the laterally outer portions 58 of the conductive element 44a respectively, with the tongue 6t) providing an even more direct conductive path for the signal than the laterally outer portions 53. The laterally outer portions 58 of the conductive element 44a exert a resilient force upon the lower end of the intermediate contact section 32a in a manner similar to that shown in FIGS. 3 and 4, and in addition, the tongue 6%) exerts a resilient force in the same direction directly upon the outermost contact section 390.
The embodiment of FIGS. 11-13 is similar to that of FIGS. 3 and 4, except the terminal portion 36 is formed of but a single strip of material, with the resilient conductive element 44b being struck out from the body of the conductive strip, instead of being formed at the free end of a reverseiy bent portion thereof, as in the embodiment of FIGS. 3 and 4.
embodiment of H68. 11l3 is similar to that of FIGS. 5-7, except that the terminal portion 36 is formed from but a single length of material and the resilient conductive element 44c is struck from the body of the spring strip. As specifically disclosed the slot 540 which bifurcates the intermediate contact section 320 is, throughout its length, wider than the conductive element 440, the slot 520 which biturcates the outer conductive section 300 being smaller in width than the conductive element 44c, the latter freely passing through the slot 540 and physically and electrically engaging the contact section 300. In the embodiment of FIGS. 11-13, as specifically illustrated, there is no counterpart to the conductive element parts 58 in the embodiment of FIGS. 5 and 6, but these could be provided if desired.
From the above it will be seen that the contact constructions here disclosed provide all of the advantages of the bellows-type contacts used in multiple electrical connectors and, in addition provide a more direct conductive path through the contact units, thereby to minimize voltage drop and undesirable inductive effects. The very structure which produces these additional advantages also serves to make more secure and reliable the electrical connection between the contacts and the terminal portions of the printed circuit plug P adapted to mate therewith. The constructions are such that they can be made simply and economically on a mass production basis through suitable punching, stamping and bending operations performed on spring strip material.
While a limited number of embodiments of the present invention have been here specifically disclosed, it will be apparent that many variations may be made therein, all Within the scope of the instant invention as defined in the following claims.
1. In a contact comprising a terminal portion, a first section connected to said terminal portion, a second section overlying and spaced from said first section and defining a contact adapted to be engaged by a conductive portion of an external assembly, and a third section spatially located between and spaced from said first and second sections, said contact sections being formed from a strip of conductive resilient material, with said third section being physically and electrically connected between said first and second sections respectively by means including reverse bends of said strip, thereby to define a bellows-shaped spring unit; the improvement which comprises a conductive element electrically connected to said terminal portion and physically resiliently engaging at least one of said second and third contact sections, thereby to function as a comparatively direct electrical path between said second contact section and said terminal portion, said third contact section having an opening therethrough, said conductive element passing through said opening and engaging said second contact section.
2. The contact of claim 1, in which said conductive element is struck out from the body of said strip.
3. The contact of claim 1, in which said terminal portion comprises first and second parallel parts electrically connected to one another, said first part being conected at its upper end to said first contact section, said second part having a free upper member defining said conductive element.
4. In a contact comprising a terminal portion, a first section connected to said terminal portion, a second section overlying and spaced from said first section and defining a contact adapted to be engaged by a conductive portion of an external assembly, and a third section sp atially located between and spaced from said first and second sections, said contact sections being formed from a strip of conductive resilient material, with said third section being physically and electrically connected between said first and second sections respectively by means including reverse bends of said strips, thereby to define a bellows-shaped spring unit; the improvement which com prises a conductive element electrically connected to said terminal portion and physically resiliently engaging at least one of said second and third contact sections adjacent the lower end of the engaged section, thereby to function as a comparatively direct electrical path between said second contact section and said terminal portion.
5. The contact of claim 4, in which said third contact section has an opening therethrough, said conductive element passing through said opening and engaging said second contact section.
6. The contact of claim 4, in which said third contact section has an opening therethrough, said conductive element passing through said opening and engaging said second contact section, said conductive element being resilient relative to said terminal portion, thereby to act as a biasing means active on said contact sections in a direction to tend to expand said bellows unit.
References Cited in the file of this patent UNITED STATES PATENTS 2,875,425 Gilbert Feb. 24, 1959 2,908,775 Gilbert Oct. 13, 1959 2,983,896 Gilbert May 9, 1961 3,016,508 Lalonde Jan. 9, 1962 3,069,652 Greco Dec. 8, 1962