US2774951A - Terminal clip - Google Patents

Description

Dec. 18, 1956 R J. KINKAID ET AL TERMINAL. CLIP Filed Dec. 16, 1954 mull/10 Y INVENTORS. Robert J. Kmka'ld and BY Kemper M. Hamfnell United States Patent TERMINAL CLIP Robert J. Kinkaid, Newville, and Kemper M. Hammell,

. Harrisburg, Pa., assignors to Aircraft-Marine Products,

Inc., Harrisburg, Pa.

This invention relates to detachable electrical connectors by which the ends of a pair of wires may be quickly and easily connected, and more particularly in such connectors to an improved sheet metal spring clip for cooperation with a mating sheet metal tab.

For most applications the characteristics desired in connectors of the sheet metal terminal clip type include, among others, high current-carrying capacity, high tensile strength or resistance to disconnection, minimum stock thickness and low connective force. These characteristics, however, are conflicting from a design aspect which has limited the utility of such connectors in the form as have been heretofore proposed to specialized applicati-ons wherein some of the desired characteristics could be sacrificed. Thus, where current capacity is a minor consideration, for example, it has been proposed to 'form the spring arms of the terminal clip so as to concentrate the available spring force at point or edge contacts with the mating tab, thereby increasing the tensile strength afforded by high contact pressure but at the expense of providing the large area contact required by high current capacity. Alternatively, the area of contact has been enlarged with a corresponding decrease in contact pressure in those applications where current capacity was the primary consideration.

In such connectors it is also desired that the width of the mating tab be substantially equal to the inside width of the clip thereby to insure maximum use of the available contact area of the clip and the tab and to prevent sidewise play of the tab within the clip. To these ends it has been proposed to provide a terminal clip having a flat floor with the side walls, which may form part of the spring system, extending substantially vertically with respect to the floor. It is extremely difficult, however, in automatic strip-forming processes conventionally employed to manufacture the connector to accomplish a true right-angle bend. Observance of realistic tolerances have therefore resulted in rounding the corners of the clip. In the stamping operation of the mating tab there is also a tendency to leave a burr along the tab side edges, which burr tends to dig into and score the rounded corners of the receptacle. As a result the pushon or connective force tended to be materially greater than the maximum force preferred for such connectors.

It is, therefore, an object of the present invention to provide an electrical connector wherein high contact pressures are maintained between elements while also providing a large area of contact without increasing the size or complexity of the components. I

Another object is to provide a detachable electrical connector having a high mechanical stability while maintaining the connective force at a minimum.

A further object is to provide a spring terminal clip having a configuration leading to simplicity of fabrication by automatic blank-forming processes.

Still another object is to provide a sheet metal terminal clip capable of receiving the mating tab with a minimum of connective force while yet having a high. retentive power.

A still further object is to provide in a sheet metal terminal clip an improved elastic system wherein spring tension is vuniformly distributed avoiding undue concentration 'of stress at any point in the system.

These objectives are, in general, attained by providing a sheet metal connector which includes a terminal clip or receptacle element having a planar web or floor with overhanging and inwardly directed spring arms extending from opposed sides of the web, the volume of metal in the elastic system of the spring arms being increased by elevating and bowing a central contact area of the floor whereby to extend the limit of spring flexure to include substantially all the metal forming the receptacle portion of the clip. The contact area of the floor is raised sufliciently to free the side edges of the mating tab member from contact with the corners of the clip where.- by to prevent concentration of stress in the spring arms adjacent the tab side edges.

Other objects and attainments of the present invention to which reference has not been made hereinabove will become apparent when the following description and claims are considered in conjunction with the drawings in which:

Figure 1 is a perspective view of two mating elements of a connector illustrative of the present invention;

Figure 2 is a plan view of the connector with the elements in connective relationship;

Figure 3 is an end view in elevation of the terminal clip portion of the connector;

Figure 4 is a slightly enlarged sectional view taken at line 44 of Figure 3';

Figure 5 is a sectional view taken at lines 5-5 of Figure 3; and

Figure 6 is a sectional ure 2.

In this specification and the accompanying drawing-s there is shown and described a preferred embodiment of my invention; but it is to be understood that this is not intended to be exhaustive nor limiting of the invention but, on the contrary, is given for purposes of illustration in 'order that others skilled in the art may fully underview taken at lines 6 6 of Figstand the invention and the principles thereof and the manner of applying it in practical use so that they may modify and adapt it in various forms, each as may be best suited to the conditions of a particular use.

Referring now to Figures 1 and 2, in the illustrative embodiment of the present invention, the connector receptacle generally designated at 1 includes a ferrule portion 3 and terminal clip portion 5 which is adapted to receive a mating generally rectangular sheet metal tab 7. Connector 1 may conveniently be formed by shaping a sheet metal blank or strip of a suitable electrically conductive material such as brass, bronze 'or other alloy, the metal being sufficiently hard and resilient to give a spring quality to clip portion 5 but preferably malleable to permit cold-forging or crimping of ferrule portion 3 onto the end of conductor 9 so as to make electrical and mechanical engagement therewith.

Clip portion 5 is provided with spring members 11 which extend from opposed sides of floor or web portion 13. The spring members or arms 11 are inturned and inwardly directed so as to overlie :a portion of floor 13, the side faces 15 at the free ends of arms 11 being substantially parallel to floor 13 and adapted to bear against the surface of the mating contact blade 7. The plane of faces 15 may be slightly inclined, Figure 3, toward the longitudinal center of floor 13 whereby upward and outward movement of arms 11 as a consequence of insertion of the tab within the clip will bring faces 15 into faceJo-face area contact with the flat upper surface'of the tab, Figure 6. The clearance between floor '1'3'aridfa6es '15 "is considerably less than thethickness of tab 7 whereby to grasp the tab with yielding pressure and preferably is such as toobtain the maximum distention that the elasticity dfthe metahwilljprnlit without effecting a permanent set in spring arins 11 upon "repeated connections and discdnne'tidns of the members.

As best illustrated in Figure 3 a substantially fiat central portion '17 comprising the contact area of 'fioor 1 3 is elevated with respect to the sides of the clip, the spring members 11 curving aroundthe side edges oftab 7, Figure 6, effectively to include within the elastic system of the spring armsat least thatpoition of floor 13 up 'to the,point of-elevationof portion 17. In addition-it'is preferred that contactliportion 17 be slightly bowed upwardly further totinclude, at least during initial spring deflection of the metal forming the clip, in the elastic systenrfor each spring arm 11 the corresponding half of contact portion 17 from 'the side edge thereof up to the crown of the bow. It is contemplated that the bow in, portion 17 will be substantially flattened upon full insertion of the tab, Figure 6, the resiliency of the bow, however, contributing to the total springpressure on the tab. Due to the configuration of the spring elements in the illustrated embodiment of the present invention there is a tendency for the floor to dish or how outwardly upon opening of spring arms 11 by tab 7 which would result in undesirable edge contact by tab 7 with the sides of contact portion 17. By providing the clip floor with an upward preformed how, the tendency to dish is counteracted and compensated whereby the desired flat area contact between the elements is obtained.

The holding power of the clip may be further increased by providing in contact portion 17 an indentation or dimple 19, Figure 5, preferably semi-circular inclined away from the insertion end of the clip to pro- .vide an abrupt rear edge 22 which acts in concert with a rounded indentation 21 in tab 7 as a detent when the tab is inserted within the clip. Preferably detent 19 is indented upwardly to approximately one-third the stock thickness of the clip whereby the holding power of the clip is sufficiently increased without unduly increasing the added amountof deflection the spring arms must take due to the lifting of the 'tab as it rides over detent 19 prior toseating f recess 21.

Elevatingthe central contact area 17 serves to relieve the clip from forceful engagement with any burr 24 which might remain on the side edges of tab 7 as a result of stamping operations employed to form the tab. The connective force. thereby is reduced to the minimum defined by the force required to open the clearance of faces 15 from floor 17 through distention of spring arms 11 to an amount-sufficient to admit the tab in the. clip. Inaddition, elimination of the edge contact of tab 7 with the sides of the clip eliminates a focal :pointabout which the spring arms would ordinarily tend to bend. The concentration of stresses at such a point would require the clip to be formed of a metalof considerable thickness to withstand thestresses necessary to develop and maintain the desired degree of contact-pressure between the elements. In the illustrative form shown the curvature of the spring members 11 around the tab edges and thebowing of contact-portion 17'assures substantially even distribution'of stresses from the pressure points at faces 15 to the crown of the --bow of contact portion -17. Moreover, by extending the length of metal in the elastic system to include floor 13, a greater deflection may be obtained between the elements having a given stock thickness without the metal taking apermanent set.

Theholding power of thecliprnay, of course, be increased by increasing the stock thickness: of sheet metal fromwhich the clip is formed. -As theistockthickness is-in reased, however, spring members 11 become more rigid requiring greater connective or push-on force to be 'exeifedwli'ile '"rendenngthe forming process more diflicult. The more effective use of the available metal according to the present invention, however, will provide the necessary amount of spring pressure required in normal applications of such clips while yet maintaining the push-on force at a minimum. In this connection the rigidity of the clip as 'a Whole may be lessened by providing one or more transverse slots 25 in web or floor 13 whereby 'to permit greater spring deflec'tion without resulting in a permanent set. In the illustrated form of the present invention two closely adjacent slots 25 are provided, the strip 27 of floor 13 therebetweenadditionally serving as a convenient position for detent 19. As thus arranged, a substantial amount'of the spring deflection in the clip required to permit tab 7 to pass over detent 19 may be absorbed by downward deflection of strip 27, thereby to relieve spring arms 11.

if desired, the forward corners 23 of the free ends of arms 11 may be inclined so 'as to guide tab 7 more easily into the clip.

For exemplary purposes, a terminal clip constructed in accordance with principles of the presentinvention was formed of three-quarters hard strip brass 0.018 inch in thickness. Within close tolerances the outside width of the clip was 0.300 inch with a clearance of 0.025 men between faces 15 and floor 13 for mating with a0.03 2 inch tab, faces 15 being inclined at an angle of approximately 2. Contact portion '17 was elevated approximately OL006 inch and bowed to have a crown 0.003 inch, the sides of the clip adjacentfloor 13' being rounded with an inside radius of 0.015 inch. With/this construction an average force of 10 poundswas required for tab insertion as opposed to an average of '12 pounds for disengaging the tab from the clip.

We claim:

1. In an electrical connector, a terminal -clipv having a substantially planar floor and overhanging spring members extending from opposed sides of saidfloor, a central contact area of said floor beingelevatedto raise a contact surface for theclip above the sides "thereof, 'said central area being transversely bowed in a continuous curvature from side-to-side thereof to extend'the elastic system of said members from the respective terminal edges thereof to the crown of said bow and'to counteract substantially the tendency of said area to bow concavely upon insertion of a mating contact blade in said clip.

2. in an electrical connector, a terminal clipfhaving a fioor and overhanging spring members extending from opposed sides of said floor, a substantially planar central contact area of said floor being relatively'elevate'd to raise a contact surface for the clip above the sides thereof, the ends of said members being directed toward said floor and with the respective terminal faces thereof being parallel with 'said floor.

3. A-terminal clip for electrical connection .witha'substantially flat contact blade comprising a web having a contact surface thereon, inwardly directed spring members extending from opposed sides of the web, theends of said members overlying and being spaced less than 'the thickness of the blade from said'contact sur' face'to engage the blade yieldingly therewith, said web having a substantially uniform transverse curvature from 'side-to-side in said'contact surface to extend the elastic systemof'said members from the respective terminal edges thereof to the crown of'the bow'defined' by said curVature said'contact surface adapted to be substantially flattened into face-to-face contact with a blade upon insertion'thereof.

4. in combination in an electrical connection, a contact blade having opposed surfaces, a sheet metal te'rminal clip for receiving said blade including a contact surface in engagement with said blade-over a'major part of one of said blade surfaces,-said.contact surface terminatin g shortof the side edges of said one'blade surface, and spring members integrally extending from opposed'sides of said contact surface and spatially encircling said side edges to bear against the other blade surface for biasing said blade into engagement with the clip, said contact surface being formed with a transverse bow of continuous curvature from side-to-side thereof, said bow being directed toward said blade for extending the elastic system of said members to the crown of the bow.

5. An electrical receptacle for a susbtantial ly flat in,- sertable electrical connector blade, said receptacle comprising: a sheet metal blank having spring characteristics, said blank being formed to define a contact portion adapted to make contact over one face of an inserted connector blade, arm portions extending integrally from each side of said contact portion first downwardly and then outwardly and upwardly and inwardly toward each other and then again downwardly so as spatially to surround without touching the side edges of an insertedconnector blade, said arm portions terminating each in an edge having an edge portion adapted to bear upon the other face of an inserted connector blade along an area of the blade sunface not substantially wider than the thickness of the metal blank from which the receptacle is formed, each such edge portion extending substantially the length of said contact portion, each such edge portion being located approximately one-third the distance from one side of the receptacle to the other side thereof; said receptacle being so constructed and arranged that during normal connected relationship with an inserted blade said contact portion will be flexed over at least a major portion into substantially flat face-to-face contact with the bottom face of the blade and so that tension in said arm portions will hold said edge faces in tight engagement with narrow spaced-apart areas extending along the top face of the blade.

6. An electrical receptacle for a substantially flat insertable electrical connector blade, said receptacle comprising: a sheet metal blank having spring characteristics,

said blank being formed to define a contact portion adapted to make contact over one face of an inserted connector blade, arm portions extending integrally from each side of said contact portion first downwardly and then outwardly and upwardly and inwardly toward each other and then again downwardly so as spatially to surround without touching the side edges of an inserted connector blade, said arm portions terminating each in an edge having an edge face adapted to bear upon the other face of an inserted connector blade along an area of the blade surface not substantially wider than the thickness of the metal blank from which the receptacle is formed, each such edge face extending substantially the length of said contact portion, each such edge face being located approximately one-third the distance from one side of the receptacle to the other side thereof, said edge faces being substantially parallel to each other and to the sides of the receptacle, and said contact portion being bowed slightly upwardly toward said edge faces; said receptacle being so constructed and arranged that during normal connected relationship with an inserted blade said contact portion will be flexed over at least a major portion into substantially flat face-to-face contact with the bottom face of the blade and so that tension in said arm portions will hold said edge faces in tight engagement with narrow spaced-apart areas extending along the top face of the blade.

References Cited in the file of this patent UNITED STATES PATENTS 2,301,447 Parker Nov. 10, 1942 2,550,636 Bengan Apr. 24, 1951 2,579,739 Hayes Dec. 25, 1951 2,600,188 Batcheller June 10, 1952 2,644,146 Dupre June 30, 1953 2,685,074 Lazzery July 27, 1954

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