US 3255430 A
Description (OCR text may contain errors)
' June 7, 1966 D. L. PHILLIPS 3,255,430
Filed Dec. '7, 1964 I5 Sheets-Sheet 1 June `7, 1966 D. l.. PHILLIPS SPIRALLY WOUND PIN CONNECTOR Filed Deo. '7, 1964 June 7, 1966 D. L.. PHlLLlPs 3,255,430
SPIRALLY WOUND PIN CONNECTOR Filed Dec. 77 1964 5 Sheets-Sheet 3 United States Patent O 3,255,430 SEIRALLY WOUND PIN CONNECTOR Delbert L. Phillips, Malibu, Calif., assignoi to New Twist Connector Corporation, Santa Monica, Calif., a corporation of California Filed Dec. 7, 1964, Ser. No. 418,381 9 Claims. (Cl. 339-252) This application is a continuationdn-part of my -copending application Ser. No. 117,881, filed June 19, 1961, now abandoned entitled Spirally Wound Pin Connector which, in turn, is a continuation-in-part of my abandoned application Ser. No. 808,783, led Apr. 24, 1959 and entitled Plug Connector.
This invention relates to releasable connectors for electric circuits and, more particularly, relates to a pin connector to t retractably into a cooperating socket connector.
The invention :meets the need for a pin connector that is highly efficient and reliable for its purpose over a long service life and at the same time is of simple, inexpensive construction suitable for mass production. The pin connector of the present invention may be produced entirely by automatic machinery at a total labor and material cost that is exceedingly low.
The invention also meets the need for a pin connector that is resiliently contrac-tible in cross sectional dimension throughout its length or at least a major portion of its length. Such a pin connector is highly advantageous for a number of reasons.
In the first place, a resiliently -contractible pin connector may be oversized relative to the cooperating socket connector so that the pin connector is forcibly contracted by the socket connector to Iassure adequate frictional engagement between the two connectors. In the second place, such a construction permits a liberal range of tolerances in the dimensioning of a pin connector to tit into a socket connector of a given size and, conversely, permits tolerances of the dirnensioning of the socket connector. In the third place, a pin connector that is resiliently contracted by the cooperating socket connector has high resistance to vibration. In the fourth place an extensive longitudinal portion of the pin connector makes pressure contact with a cooperating socket to minimize contact resistance at the connection.
A iifth advantage is that such a resiliently contractible pin connector does not depend on spring action by the cooperating socket connector to make an effective elecy trical connection. A sixth advantage is that using such a lresiliently contrac-tible pin connector cooperating with a socket connector that is yieldingly expandible provides a combination of two yielding means with two different natural frequencies of vibration so that only one of the two yielding means can be in resonance with an imposed vibratory frequency at one time, the other yielding means being out of resonance to maintain the eiectiveness of the electrical joint.
The invention further meets a certain troublesome problem that arises from two facts. Thel rst fact is that conventional pin connectors commonly deteriorate badly with respect to resistance to withdrawal from the `cooperating socket connectors and, especially so, when the electrical connections are made and broken repeatedly. Because of this fact effective withdrawal resistance after a period of use can be assured only by starting with a high initial resistance to withdrawal. The second fact is that it is difficult to manufacture pin connectors in large quantities to fall within a narrow range with respect to magnitude of resistance to Withdrawal of the pin connectors from cooperating socket connectors.
Because of these facts, it has been necessary heretofore to accept an unduly high initial resistance to withwire.
3,255,439 Patented June 7, 1966 ICC drawal and to accept a wide range of initial resistance. In -too many instances the initial resistance afforded by a new pin connector is high in the liberal range. In practice, if a -certain given minimum magnitude of resistance to ywithdrawal is required for a given installation, a much higher magnitude than t-he required minimum must be accepted. In many instances, such a wide range of withdrawal resistances creates difficulties. For example an umbilical cord for readying a missile for launching commonly incorporates a large number of releasable electrical connections provided with pin connectors and cooperating socket connectors and -the total resistance to withdrawal of the large number of pin connectors tmay be seriously excessive.
The invention meets this problem by providing a pin connector that oifers resistance to withdrawal within only a narrow range of tolerances and that may be depended upon to maintain substantially the same magnitude of resistance to withdrawal after repeated usage over a long service period. 1
Broadly described, the pin connector comprises a longitudinal core Wire with a cluster of resiliently flexible wires surrounding the Core wire, the cluster being oversized in cross-sectional dimension relative to the cooperating socket connector. The opposite ends of the -wires of the cluster are fxedly connected with the core wire and the intermediate portions of the wires of the cluster are spaced radially outward from the core wire to permit the desired resilient radial contraction of the cluster by a cooperating connector socket.
In some practices of the invention a second outer set of wires is added to the cluster to give the pin a relatively large diameter. The second set is an outer set that surrounds an inner set of -wires and is anchored in the same manner to the opposite ends of the axial core Preferably the t-wo sets of wires of the cluster are helical wires and the two sets are wound in opposite directions.
A feature of the invention is that the pin connectorv in its simplest form com-prises a single pin element Iwith both of its ends adapted for insertion into two corresponding sockets. As will be explained, such a pin element may be used for circuit connections in the general manner of a dowel `without the necessity of applying solder. A plurality of such double ended pin elements may be used to electrically interconnect two printed circuit panels with the panels positioned face to face, or -wit-h the panels positioned edge to edge in the same plane, or with one panel at relative to the other.
The invention has special utility for mounting electrical components on a printed circuit panel or on a breadboard because the spring-like outer cluster wires are so effective for frictionally engaging cooperating sockets. By simply plugging in the pin connectors, connections may be made and tested without stopping to solder or otherwise process the connections. Such connections reliably serve as permanent connections. Thus the invention makes it possible to break the electrical connections with a printed circuit board by simply withdrawing the resilient pin elements from the cooperating sockets. The components plugged into a panel in this manner are conveniently interchangeable and may be quickly and conveniently replaced lwhen desired.
The simple yielding pin element of the invention may also be used in'combination with conductive plastics to make highly accurate but inexpensive resistors. Thus a plug-inresistor may be fabrica-ted simply by inserting a pair of heated pins into afconductive elastomer at spaced points, the heat serving to vulcanize the pins to the elastomer.
The features and advantages of the invention may be understood from the following description and the accompanying drawings.
In the drawings, which are to be regarded as merely illustrative:
FIG. 1 is a view of a pin connector embodying the invention, the view being partly in side elevation and partly in section;
FIG. 2 is a transverse section taken as indicated by the line 3 3 of FIG. l showing how the wires of the cluster and the axial core wire are crowded together inside the base ferrule of the pin connector;
FIG. 3 is a cross section taken as indicated by the line 3 3 of FIG. l and showing how the intermediate portions of the helical wires of the cluster are normally spaced radially away from the core wire;
FIGS. 4 and 5 are cross-sectional views similar to FIGS. 2 land 3 showing how a pin connector may have a larger number of helical wires of smaller diameter mounted on a core wire of larger diameter than in the first embodiment;
FIG. 6 is a side elevation of a second embodiment o f the invention wherein the pin element of the connection is tapered;
FIG. 7 is a side elevation of a third embodiment of the invention which also has a tapered pin element;
FIG. 8 is a side elevation of the pin connector of the invention in its simplest form comprising a pin element, the opposite ends of which may be inserted into cooperative socket connectors;
FIG. 9 is a view partly in side elevation and partly in section showing how the pin element of FIG. 8 may be provided with an encasing cap or ferrule on one end;
FIG. 10 is a side elevation of the pin wherein an outer set of helical wires is applied to the pin element shown in FIG. S to increase the diameter of the pin element, the ends of the outer helical wires being bonded to the end of the axial core wire in the same manner as the inner helical wires;
FIG. 1l is a transverse section taken as indicated by the line 11-11 of FIG. 10 showing the two sets of helical wires of the pin element;
FIG. l2 is a view partly in side elevation and partly in section showing how the simple pin element of FIG. 10 may be provided with an encasing cap or ferrule at one end;
FIG. 13 is a side elevation partly in section of a double ended pin connector, the two pin elements of which may "be inserted into corresponding socket connectors;
FIG. 14 is a sectional View showing how the pin element of FIG. 8 may be employed to electrically connect two printed circuit boards or panels with the two boards or panels in face to face relationship;
FIG. 15 is a similar view showing how the pin element of FIG. 10 may be employed in the same manner;
FIG. 16 is a side elevation of a pin connector of a bulbous configuration;
FIG. 17 is a transverse section of a pin element in which the core comprises three wires twisted together;
FIG. 18 is like FIG. 13 with thinner pin elements such as shown in FIG. 8 substituted for pin elements such as shown in FIG. 10; and
FIG. 19 is a side elevational view with a lportion broken away showing a pin connector embodying one practice of the invention.
The rst embodiment of the invention illustrated by FIGS. 1 to 3 includes a base member in the form of a errule 30, the bore of which is of stepped coniguration to receive the end of an insulated wire 32. The wire 32 is shown anchored in the bore by solder 34 with the insulation 35 of the wire extending into the enlarged end of the bore. lf desired, the ferrule 30 may be crimped to engage the wire 32 with the solder omitted. The pin element of the pin connector comprises an axial core Wire 36 and a cluster of helically formed wires 38 surrounding the core wire.
It is contemplated that the two ends of the helical wires 38 of the cluster will be iixedly connected with the corresponding ends of the core wire 36: In this particular embodiment of the invention, the ferrule 30 is'crimped inward as indicated at 4t) to grip the cluster of wires 38 and thus serves the purpose of iixedly connecting the inner ends of the helical wires 38 to the core wire 36. The outer ends of the helical wires 38 may be bonded to the outer end of the core wire 36 in any suitable manner, for example, by solder. In this instance, the outer ends of the helical wires 38 and the outer end of the core wire 36 are welded together, an arc welding operation being used for this purpose. Such an arc welding operation is advantageous in that it melts the ends of the wires to make the leading end of the pin desirably rounded.
It is contemplated that the core wire 36 will be made of highly conductive material and soft copper is presently preferred for this purpose. On the other hand, it is contemplated that the helical wires 38 will be of resilient or spring-like construction. For this purpose, the helical wires 38 may be made of beryllium copper that is threefourths hard.
As clearly shown in FIG. 3, the helical wires 38 at their intermediate portions are spaced radially outward from the core wire 36 to permit the pin element of the connector to be yieldingly contracted radially by the cooperating socket connector in which it is inserted. It may be further noted in FIG. 3 that the core wire 36 has shallow recesses or indentations 42 on its peripheral surface corresponding to the helical wires 38 to provide additional clearance for radially inward flexure of the helical wires.
The unrestrained cross-sectional dimension of the cluster v of helical wires 38 in FIG. 3, i.e. the overall cross-sectional dimension of the cluster before the` pin element of a pin connector is inserted into a cooperating socket connector, is greater than the internal cross-sectional dimension of the cooperating socket connector. Consequently, insertion of the pin element into the cooperating socket connector causes the pin element to be radially contracted, the major portions of the helical wires 38 being exed towards the core wire 36. On the other hand, the cornpletely contracted cross-sectional dimension of the pin element shown in FIG. 2 is preferably too small for effective t in the cooperating socket connector. v l
The construction may be understood by considering the preferred method of fabrication. First, the outer wires 38 are Wound helically tightly around the core wire 36 to make a strand of wires and then the strand of wires is drawn through a die orifice that contracts the strand with consequent forcing of the relatively hard beryllium copper helical wires into the relatively soft copper core wire with resulting formation of the helical indentations 42 in the core wire.
After the strand of wire has been processed in this manner, the end of the strand is inserted into a ferrule 30 and the ferrule is crimped as indicated at 40 in FIG. 1 to fixedly confine the wires of the end of the strand, thus in effect connecting the ends of the helically formed wires 38 to the end of the core wire 36. The wire strand is then cut to the desired length for a pin element'and the outer ends of the wires of the severed strand are then bonded together by the application of a small electric arc of suicient intensity and duration to cause the metal at the ends of the wires to melt and form a single rounded nose 44 as shown in FIG. -1.
At this point in the procedure of fabricating the pin connector, the helically formed wires 38 are seated snugly in the helical indentations 42 of the core wire 36. The next step is to shorten the core wire 36 to cause the helically formed wires 38 to be flexed or biased outward in the manner indicated by FIG. 3.
The preferred procedure for shortening the core wire `36 is simply to subject the pin element to a suitable endwise impact. An alternate procedure which is also satisfactory is simply to grip the two ends of the pin element and twist the pin element in an unwinding direction for 'in the core wire.
a few degrees. The unwinding operation in itself causes the helical wires 38 to bulge radially outward from the corewire 36 and the shortening of the core wire that is caused by the twisting of the core wire further expands the cluster of helically formed Wires.
It is apparent that the use of relatively soft copper for the core wire 36 is advantageous for a number of reasons. In the iirst place the soft copper offers relatively low resistance to the flow of current to minimize the contact resistance at an electrical joint that is completed by the pin connector. In the second place the relatively soft copper is readily deformed to provide the indentations 42 fo-r greater freedom of radial movement of the helically formed wires.
tn the other hand, the use of beryllium copper for the helically formed wires is advantageous because the beryllium copper is hard enough to form the indentations A further advantage is that the 'resiliency of beryllium copper makes the helically formed wires 38 function as springs soI that the confined helical wires make effective contact with a surrounding socket and resiliently conform to the dimensions and configuration of the socket. Each of the helical springs makes contact with a surrounding socket .throughout the major portion of the length of the spring and since there is a plurality of thehelically formed wires, say four, six, eight or more wires, the connector pin and the socket in which the connector pin is inserted have an extensive area of mutual contact. The extensive area of mutual Contact not only lowers the resistance at the electrical connection but also results in longevity for the connector pin.
FIGS. 4 and 5 show in cross section how a pin element of a pin connector may have an axial core wire 45 in combination with a cluster of six helical wires 46, the helical wires being smaller in diameter than the four helical wires 3S of the iirst described embodiment of the invention. As shown in FIG. 5, the core wire 45 has peripheral recesses or helical indentations 48 corresponding to the individual helical wires 46, and the intermediate portions of the cluster wires are spaced radially outward from the axial core wire so that the pin element of a pin connector may be radially contracted by a socket connector in which it is inserted.
FIG. 6 shows another embodiment of the invention in which a pin element comprising a core wire t) and a cluster of helically formed wires 52 is mounted in a ferrule 54 for connection to a circuit wire 55. The ferrule 54 is crimped around the helical wires 52 as indicated at 56 and is also crimped around the circuit wire 55 as indicated at 58. The cluster of helical wires 52 is tapered in overall configuration and in this particular instance, the core wire 50 is also tapered. Such a tapered pin element of a pin connector may be used with a cooperating socket connector that is correspondingly tapered, or if desired, the tapered pin element may be used with a socket of uniform cross section.
FIG. 7 shows a pin connector with a pin element having a greater diameter than the pin element of FIG.6 and having a greater taper angle. In FIG. 7, one end of a core wire 59 and the corresponding ends of six spirally formed wires 69 are rigidly gripped by a ferrule 62 which is crimped for this purpose, as indicated at 64. The outer ends of thespiral wires 6ft are bonded to the outer end of the core wire 59 by welding in the manner heretofore described. v
FIG. 8 shows how the invention may be incorporated in a pin connector, both ends of which may be inserted into corresponding sockets. The pin connector shown in FIG. 8 is the simplest form of the invention and consists of a pin element without a ferrule. A single core wire extends from one welded end of thepin element to the other welded end and a cluster of helical wires 65 encases the single core wire throughout its length, the opposite ends of the helically formed wires being welded to the opposite ends of the core wire. The helical wires 65 are biased radi-ally outward from the core wire in the manner heretofore described.
FIG. 9 shows how the simple pin element shown in FIG. 8 may be provided with an encasing cap or ferrule 66 at one of its ends. The ferrule 66 may be crimped into engagement with the end of the pin element o-r may be soldered to the pin element or may be otherwise bonded to the pin element. The encasing cap or ferrule 66 makes it unnecessary to weld together the inner ends of the wires.
FIGS. 10 and 11 show a relatively thick double-ended pin element that may be formed by adding a second set of helically formed wires 68 to enclose the set of helical wires 65 of the pin 8, the outer set of helical wires being preferably wound in the opposite direction from the inner set. The opposite ends of the outer helical wires 68 are welded both to the opposite ends of the axial core wire. FIG. 1-1 shows how the outer set of helical wires 68 and the inner set of helical wires 65 are related to each other and how they are rel-ated to the axial core wire 82. All of the spiral wires of the two sets are biased radially outwardly.
FIG. 12 shows how the pin element of FIGS. l() and 11 having both an inner set of helical wires 65 and an outer set of helical wires 68 may' be provided with an encasing end cap or ferrule 70. Here again the end cap or ferrule 70 makes it unnecessary to weld together the inner ends of the wires.
FIG. 13 shows how two pin elements A71 of the construction shown in FIGS. 10 and 11 may be mounted in the opposite ends of a ferrule 72 to form a double-ended pin connector. The opposite ends of the connector may be inserted into two corresponding sockets. FIG. 18 is similar to FIG. 3 with thinner pin elements 73 mounted in a ferrule 72, the thinner pin elements being of the construction of the pin element shown in FIG. 8.
One advantage of adding a second set of helical wires is, of course, the increase in the diameter of the pin element for installations where increased diameter is desirable. A more important advantage is that using two sets of relatively fine helical wires to provide a pin element of a given diameter instead of using a single set of coarser helical wires is that the pin element may be bent and rebent with relatively little damage and weakening of the helical wires. This fact may be appreciated when it is considered that when two wires of different diameters are bent to a given radius the material-of the wire of the smaller diameter is stressed to a lesser degree than the material of the wire of the larger diameter. Another advantage of using two sets of helical wires instead of one set, is that the two sets more effectively enclose the axial core wire. If only one set of helical wires is used in the construction of a pin element and the pin element is bent to a sharp angle, the core wire may protrude at the bend. -If two sets of helical wires are used, the core wire will not protrude at a sharp bend.
A further advantage of using relatively line outer helical wires either in a pin element with two sets of helical wires or in a pin element with a single set of helical wires is the increased area of mutual contact between the pin element and a surrounding socket into which the pin element is inserted. For example, if the outer surface of a pin element is formed by four helical wires, as shown in FIGS. 1, 2 and 3 and the pin is inserte-d into a socket lA; inch deep, for example abore in a printed circuitboard that is 1/16 inch thick, the pin will make contact with the socket along four spiral lines each somewhat longer than lAf; inch for a total of 4/16 of an inch. If 6, 8, l() and 1'2 finer helical wires form the outer surface of a pin element of the same diameter, the total length of the lines o-f contact will be correspondingly increased to result in a highly effective electrical connection with exceedingly low contact resistance.
Another advantage of using a relatively large number of relatively fine helical wires to provide the outer surface of a connector pin element instead of a fewer number of coarser wires is greater tolerance in the di-mensions of the pin elements and the complementary sockets. To explain, the larger number of relatively fine helical wires results in a greater range of -radial contraction `and expansion of a pin element to permit the pin element to cooperate effectively with sockets of a corresponding Wide range of diameters, and especially so when the cluster of Wires consists of two sets of oppositely wound helical Wires. It is apparent that a double thickness pin element having two sets of oppositely wound helical wires has special utility where a wide Arange of dimensions must be tolerated and where extreme flexibility is required.
FIG. 14 shows how the connector pin or pin element shown in FIG. 8 may be employed to interconnect conductors on a pair of printed circuit boards 74 and 75 that are positioned in face to face abutment. For the purpose of electrically interconnecting the two printed circuit boards, each of the two boards is provided with a bore 76 and a portion of a printed conductor 71S on each printed circuit board is extended into the corresponding bore to form a conductive lining for the bore as indicated at 8) in FIG. 14. The connector pin 81 in FIG. 14 makes effective and extensive contact `with both of the conductive linings 80. FIG. 15 shows how a connecto-r pin 81a of the construction shown in FIG. 10 may be employed in the same manner, the arrangement shown in FIG. 15 being the same as the arrangement shown in FIG. 14, as indicated by the yuse of correspondin-g numerals to indicate corresponding parts.
FIG. 16 shows a connector pin with a pin element comprising a core wire 82 and a cluster of helical wires 84 gripped at one end by an encasing cap or ferrule 8&5. The cluster of helical wires 84 is bulbous in overall configuration to provide a larger than usual range of resilient contraction for the pin element.
FIG. 17 shows how a plurality of three wires may be used for a core of a pin element instead of a single wire. The three co-re `wires 168* in FIG. 17 are surrounded by a cluster of helical wires 162, the twist direction of the three core wires being opposite to the helical direction of the outer wires 162. The use of three relatively small core Wires instead of a single relatively lar-ge core wire shown in FIGS. 3 and 4 p-rovides a connector pin of increased tlexibility.
FIG. 19 shows the presently preferred embodiment of a combination of a pin element 170 and a ferrule 172 constituting a pin connector for mounting on the end of aninsulated conductor 174. -It is to be noted that the pin element 170- is of the previously described construction shown in FIG. 10 Which is characterized by two solid metal rounded noses 175 at its opposite ends that are produced by fusing the wires together. In the fabrication of the pin connector shown in FIG. 19 the pin element 170 in unexpanded form is first mounted vin the ferrule 172 and is secured therein by crimping the -ferrule. The whole pin connector is then subjected to axial compression to shorten the pin element and thus expand the pin element radially, the pin element being stressed beyond its elastic limits so that it is permanently expanded. The advantage of the const-ruction is that the fusing of the wires together to form the solid metal noses 175 at the opposite ends of the pin element keeps the wire ends from slipping longitudinally relative to each other when the pin connector is subjected to axial compression.
My description in specific detail of the selected embodiments of the invention kwill suggest various changes, substitutions and otherdepartures from my disclosure within the spirit and scope of the appended claims.
1. An electrical pin connector forinsertion at its opposite ends into corresponding sockets of two devices for electrically interconnecting the two devices, each end of the pin connector comprising:
an axial core of at least one wire; and a surrounding cluster of resilient wires wound helically around the axial core wire and connected at their outer ends to the axial core, said core restricting the length of the cluster to bias the -helically Iformed wires radially outward to make the cluster resiliently radially contractible by the corresponding socket into which it is inserted, said cluster comprising two sets of helically formed wires connected at their opposite ends to the core, one of said sets being an inner set surrounding the core, the other set being an outer set surrounding the inner set. 2. A pin connector as set forth in claim 1 in which the two sets of wires are wound in opposite helical directions.
3. A pin connector as set forth in claim 11 which comprises a central ferrule with two cores of at least one wire each and two clusters of helically formed wires mounted in the two ends lrespectively of the ferrule.
4. A pin element to 'lit into a cooperating socket connector comprising:
a longitudinal core; and a cluster of resiliently flexible wires formed helically around the core, said cluster being oversized in cross section relative to the cooperating socket connector in which it is intended to be lit,
the opposite ends of the Wires of said cluster bein-g lixedly connected with the core and the intermediate portions of the wires of the cluster being spaced and biased radially outward from the core to permit resilient radial contraction of the cluster by the cooperating socket connection,
said cluster comprising Aan inner set of `wires formed helically around the core and an outer set of wires formed helically around the inner set.
5. AA pin connector as set forth in claim 4 in which said two sets of wires are wound in opposite helical directions.
6. A pin element to fit into a cooperating socket connector, comprising:
a longitudinal core; and
a cluster of resiliently flexible wires formed helically around the core, -the cluster being oversized in cross section relative to the cooperating socket connector in which it is intended to be t, the opposite ends of the wires of the cluster being fixed relative to the core and the intermediate portions of the wires of the cluster being spaced and biased radially outward from the core to permit resilient radial contraction of `the cluster by the cooperating socket connector, said core being formed with helical recesses conforming to the helical configuration of the wires of the cluster to increase the capability of the pin elel ment for radial contraction.
7. A pin connector to lit into a cooperating socket connector, comprising:
a longitudinal core; and
a cluster vof resiliently flexible wires formed helically around the ycore,the cluster being oversized in cross section relative to the cooperating socket connector in which i-t is intended to t, the opposite ends of the wires of the cluster being iixed relative to the core and the intermediate portions of the wires of the cluster being spaced and biased radially outward from the core to permit resilient radial contraction of the cluster by the cooperating socket connector, said longitudinal core comprising a plurality of wires twisted together, the twisting of the wires of the core being opposite to the helical direction of the 'cluster of wires.
3. A pin connector, comprising:
a pin element; and
a base member attached thereto,
said pin element comprising an axial metal core and a cluster of resilient wires surrounding the core and bowed outwardly from the core,
the opposite ends of the cluster of wires being fused to the corresponding ends of the core and forming therewith solid metal noses at the opposite ends of the pin element,
said noses having smooth rounded end surfaces free from sharp edges,
said base member embracing one end of the pin element and the corresponding nose thereof,
9. Apin connector, comprising:
a ferrule, and
two coaxial pin elements attached to the opposite ends of the ferrule,
each of said pin elements comprising an axial metal `core and a cluster of resilient wires surrounding the core and bowed outwardly from the core,
the opposite ends of the cluster of wires being fused to the corresponding ends of the core and forming therewith solid metal noses at the opposite ends of the pin element,
sai-d noses having smooth rounded end surfaces free from sharp edges,
said base member embracing one end of each of the two pin elements and the corresponding nose thereof.
References Cited by the Examiner UNITE STATES PATENTS 5/1916 Parker 57-147 3/1956 Edelman et al. 339-17 6/1956 Shewmaker 339-17 11/1956 Henry 29-155.5 1/1957 Albright et al. 29-l55.5 11/1960 Epstein 29-155.7l 6/1961 Cahill 29-155.71 1/1962 Platz et al 339-252 4/ 1963 Campbell.
FOREIGN PATENTS 12/ 1938 Germany.
9/ 1927 Great Britain. 7/1930 Great Britain. 7/1931 Great Britain. 1/ 1947 Great Britain.
JOSEPH D. SEERS, Primary Examiner.
ALBERT H. KAMPE, Examiner.
R. E. MOORE, Assistant Examiner.