GB2026255A - Electrical contact - Google Patents

Abstract

An electrical contact for terminating an insulated wire, comprises an elongate cylindrical-shaped electrical contact body 5, and a hollow fastening collar 24 dimensioned to snugly fit over the contact body 5. The contact body includes a terminal means 2,3 at one end thereof for making connection to an external conductor or apparatus, and a wire-receiving portion at the other end thereof for receiving a wire having a central insulated electrical conductor. The wire-receiving portion 7 has a transverse slot 13 extending across the body 5 and opening at the wire-receiving end of the contact body 5 to define a pair of opposed insulation-piercing jaws 15 for cutting and separating insulation from the central conductor of a wire as the wire enters the slot 13 from the wire-receiving end of the contact body 5. The hollow fastening collar 24 is dimensioned to bias the jaws 15 toward one another after previously having been spread apart by the insertion of a wire in the wire-receiving portion 7 of the contact body 5. The contact is particularly suitable for high current applications. <IMAGE>

Description

SPECIFICATION Electrical contact This invention relates to the field of terminating wires, and more particularly to an electrical contact for terminating a wire having a central insulated electrical conductor, without the need for stripping the wire.

In the prior art, electrical wires carrying heavy currents were generally connected attheirtermination ends by first stripping insulation from about the central conductor of each wire and crimping or soldering the stripped conductor to a terminal lug that is subsequently connected to a terminal strip by means of large-headed screws. However, stripping insulation of large sized wires which carry heavy current loads is cumbersome and time consuming, in that the connection cannot be performed quickly and simply. The problem is amplified when such heavy current wires are to be connected to a multipleterminal strip having a plurality of closely adjacent electrical terminals.

Additionally, in conventional methods of connecting high current wires fastened at their terminal points with screws, the screws can become loosened by vibrations or other causes to create high resistance connections where substantial heat may be generated.

There has been some success in terminating wires using insulation-piercing contacts, but such contacts have been limited to low current applications. Again due to the high currents involved, high resistance connections and/or arcing might easily occur at the interface between the conductor of a wire and a prior art insulation-piercing contact point.

The present invention relates to an electrical contact that can be connected to the conductor of an electrical wire easily, quickly, and securely, without stripping the insulation, and yet the electrical contact is capable of maintaining good electrical connection even for heavy electrical current applications.

In accordance with the invention, there is provided an electrical contact comprising two separate parts, an elongated cylindrical-shaped electrical contact body, and a hollow fastening collar dimensioned to snugly fit over the contact body. The contact body includes a terminal means at one end thereof for making connection to an external conductor or apparatus, and a wire-receiving means at the other end thereof for receiving a wire having a central insulated electrical conductor. The wire-receiving portion has a transverse slot extending across the body and opening at the wire-receiving end of the contact body to define a pair of opposed insulationpiercing jaws for cutting and separating insulation from the central conductor of a wire as the wire enters the slot from the wire-receiving end of the contact body.The wire to be inserted is arranged to have its longitudinal axis normal to the longitudinal axis of the contact body, the slot having a width no greater than, and preferably smaller than, the diameter of the central conductor of a wire to be inserted in the wire-receiving portion of the contact body. The hollow fastening collar is dimensioned to snugly fit over the wire-receiving portion of the contact body without a wire having been inserted in the body, and to bias the jaws toward one another after previously having been spread apart by the insertion of a wire in the wire-receiving portion of the contact body.

Again, in a preferred arrangement, the inside diameter of the collar is slightly less than the outside diameter of the wire-receiving end of the contact body.

The insulation-piercing portion of the contact body includes a blade formed on the tip of each jaw at the wire-receiving end, the blades having their edges lying in a plane perpendicular to the plane of the transverse slot and sloping inwardly and away from the wire-receiving end of the body.

To aid in guiding the collar over the wire-receiving end of the contact body, each of the jaws has at least one exterior sloping surface at the periphery of the wire-receiving end of the contact body to align and cam the collar over and onto the wire-receiving portion of the contact body.

The transverse slot extends axially of the contact body for a predetermined depth, and in a preferred embodiment of the invention, the body has a transverse opening at the predetermined depth to relieve strain at the closed end of the slot due to flexure of the jaws when a wire is being inserted into the contact. In one specific embodiment, the straiin relief is in the form of a relief slit extending across the body of the contact at the closed end of the slot, the slit having a width narrower than that of the slot and opening into the closed end of the slot. In an alternative specific embodiment, the strain relief is in the form of a transverse cylindrical bore extending across the body at the closed end of the slot, the diameter of the bore being larger than the width of the slot but no larger than the diameter of the conductor of a wire to be inserted in the contact.

In a further alternative embodiment, the slot may be provided with sloping sidewalls which merge toward one another in the direction of insertion of a wire into the slot. This arrangement would allow easy insertion of the wire as it enters the contact and yet provide substantial compressive forces at the bottom of the slot against the central conductor.

The terminal end of the contact may be provided with a threaded stud for securing it to a connector strip or connector body, or the terminal can be in the form of a connector pin which projects through an insulation block and can therefore comprise the male pins of a completed connector. Of course, if desired, female contacts can replace the male pins of a completed connector.

In order to ensure that the insulation of the wire does not interfere with good electrical connection in the slot, the body of the contact is provided with a reduced diameter portion which includes the closed end of the slot, so that when the wire is forced down the slot and bottomed at the closed end of the slot, The drawing(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy. the insulation which was cut and separated by the insulation-piercing jaws of the contact will be spaced from the periphery of the reduced diameter portion.

In this manner, when the collar is forced over the wire-receiving end of the contact and cams the jaws toward one another, a clean central conductor (free of bits of insulation) is compressed within the slot transversing the reduced diameter portion of the contact body.

Finally, the contact of the present invention can be utilized in a multi-contact connector, whereby a plurality of wires can be inserted into the wirereceiving end of each contact simultaneously, and a plurality of corresponding collars can be forced over the jaws of the contacts, also simultaneously. In such an arrangement, the insulation block of the connector can be provided with a wire-holding groove adjacent each contact for holding a wire aligned with the slot in the contact as the wire is inserted into the slot.

The invention will now be described in detail with reference to the accompanying drawings representing preferred embodiments of the electrical contact according to the present invention. In the drawings: FIGURE 1 shows an electrical contact for terminat- ing a wire, made in accordance with the present invention.

FIGURE 2 is a right side elevational view of the contact of FIGURE 1.

FIGURE 3 is a cross-sectional view taken along the line 3-3 in FIGURE 1.

FIGURE 4 is a perspective view of the contact of FIGURE 1 mounted on a terminal strip.

FIGURES 5-9 illustrate the various positions of an insulated conductor as it is tooled into the wirereceiving portion of the contact, and further illustrate the procedure for inserting a wire into the contact and inserting the collar over the wire receiving portion of the contact.

FIGURE 10 shows the size relationship between the wire to be inserted and the wire-receiving end of the contact.

FIGURE 11 shows, in partial cross-section, the manner in which the insulation of the wire is stripped as the wire is pushed to the bottom of the slot.

FIGURE 12 shows a completed connection, wherein the collar has been fully inserted to force the jaws of the contact body toward one another to further compress the conductor between the contact jaws.

FIGURE 13 is a perspective view of a connector insulation block holding a plurality of contacts made in accordance with the invention, and a tool particularly adapted to insertthe wires intothewire- receiving end of each contact simultaneously.

FIGURE 14 is a perspective view of a connector insulation block holding a plurality of contacts made in accordance with the invention with the wires fully seated in the slots of each contact and a tool for inserting a collar over the jaws of each contact.

FIGURE 15 shows an alternative embodiment of the wire-receiving portion of the contact illustrating one form of strain relief for the jaws thereof.

FIGURE 16 shows an embodiment of the wire receiving portion of a contact having inwardly and downwardly sloping sidewalls to define the wire receiving slot.

FIGURE 17 shows a simplified version of a collar made in accordance with the invention.

FIGURE 18 is a perspective view of a complete electrical contact showing an alternative embodi ment of the terminal portion thereof in the form of a connector pin which serves as a male contact for a completed connector.

FIGURES 1-4 illustrate a preferred embodiment of the present invention showing various views of an electrical contact body 5 and cooperating fastening collar 24.

The electrical contact body 5 includes a wire receivirrg portion 7 and a terminal portion 2,3. In a preferred embodiment, a conductor-compressing portion Cof reduced diameter may be advantageously utilized, as will be explained later.

Wire-receiving portion 7 has a transverse slot 13 extending across the entire width of the body of the contact 5 and to a predetermined depth. The slot 13 has a closed end in the direction toward the terminal portion 2,3 of the contact body 5 and opens at the wire-receiving end of the contact body 5 to thereby define a pair of opposed insulation-piercing arms 11, 12. The upper edges 15 of the insulation-piercing arms 11, 12 are diagonally formed to extend inwardly and away from the wire-receiving end of the contact body 5. The diagonally formed jaw edges 15 define insulation-piercing jaw edges 18,19 for effecting a cutting action into the insulation of a wire to be inserted in the contact body 5.As can best be seen in FIGURE 2, the blades 18 and 19 are wedgeshaped for a substantial distance axially of the contact body to form triangular-shaped insulationpiercing jaws 16,17.

In order to secure a conductor in the slot 13 positioned at the closed end of the slot, collar 24 is forced overthe jaws 16, 17 and onto arms 11, 12. The inside dimensions of the forward end of fastening collar 24 are such that the arms 11, 12 will be biased inwardly toward one another to compress a conductor lying at the closed end of the slot 13. In order to guide the fastening collar 24 over the edges of the insulation piercing jaws 16, 17, sloping surfaces 20 and 21 are provided. For further aiding the collar to be slid overthe insulation-piercing arms 11, 12, additional sloping surfaces 22,23 are provided.Sloping surfaces 22,23 permit an optimum anglefor insulation-piercing jaws 16, 17 while yet providing optimum guiding and caming action for insertion of the fastening collar 24 over the wire-receiving portion 7 of the contact body 5. This is best illustrated in FIGURE 3 which shows a more obtuse angle for the sides oftheinsulation-piercing jaws 17 than that for the sloping surfaces 23 When it is desired to provide a reduced diameter portion 6 for the contact body 5, a shoulder 8 results at the interface between the wire-receiving portion 7 and the reduced diameter conductor-compressing portion 6, and spaced conductor clamp portions 9 and 10 are produced adjacentthe closed end of slot 13. A cylindrical base portion 1 also results from reducing the diameter of portions 6 in order to provide sufficient area of engagement with a contact strip 4 (FIGURE 4) upon which the contact body 5 can be mounted.

Since a wire being forced into slot 13 will tend to spread apart arms 11 and 12, a substantial amount of strain will develop next to the closed end of slot 13.

In order to reduce the amount of strain concentrated at this point, and thereby avoid damage to the contact body 5, a transverse opening 14 is provided.

In a preferred embodiment, the fastening collar 24 can be provided with an internal tapered annular rim 25 (FIGURE 3) which cooperates with the sloping surfaces 20, 21 and 22, 23 as the collar 24 is inserted over the wire-receiving portion 7.

With reference to FIGURES 5-9, there is shown perspective views of the manner in which a wire 28 is inserted into the wire-receiving portion 7 of contact body 5. In FIGURE 5, a wire 28 having a central conductor 31, insulated by insulation 27, is positioned with its longitudinal axis substantially parallel to the transverse axis of the slot 13. FIGURE 6 shows an insertion tool 29 having an insertion blade 30 forcing wire 28 into the wire-receiving portion 7 of the contact body 5. FIGURE 6 illustrates that the insulation 27 is cut and severed by the insulation-piercing jaws 16, 17, and the insulation follows the sloping surface of the jaws 16 and 17 and sloping surfaces 22, 23 to accumulate on the outer periphery of arms 11, 12. In the FIGURE 6 illustration, the wire is only partially inserted into the wirereceiving portion 7.

FIGURE 7 shows a fully inserted wire 28 seated at the bottom closed end of slot 13. FIGURE 8 is a view similar to that of FIGURE 7 showing additionally the fastening collar 24 as the tapered annular rim 25 begins to engage sloping surfaces 20, 21.

FIGURE 9 shows a completed assembly of fastening collar 24 over wire-receiving portion 7 (not visible in the figure) with the wire 28 being compressed between conductor clamps 9 and 10. FIGURE 9 also shows a portion of a collar insertion tool 32 having a cylindrical hole 33 sized to slip over collar 24 and force collar 24 into the assembled position as seen in FIGURE 9.

The width of slot 13 as compared to the size of the inner conductor 31 and insulation 27 of wire 28 is shown in FIGURE 10. For good electrical contact, it can be appreciated that the width of slot 13 must be no greater than the diameter of conductor 31. Additionally, it is preferred that the length of blades 18 and 19 be sufficient to accommodate the full diame terofthe insulation 27 of wire 28.

The manner in which the insulation is stripped and spread apart as the wire is inserted into the contact is illustrated in FIGURE 11. In this figure the upper position of wire 28 shows that the insulation 27 has been cut by blade 18 and spread by insulation-piercing jaw 16 to separate the insulation into two pieces which continue to be spread apart until the insulation is separated a distance equal to the diameter of the wire-receiving portion 7 as shown in the middle wire position of FIGURE 11. As the wire is pushed further downwardly into slot 13, it comes to rest at the closed end of the slot where it meets with slit 14.

Thus, in the bottomed position of wire 28 in FIGURE 11, the insulation remains spread to the diameter of wire-receiving portion 7 after it passes shoulder 8 and seats in the bottom of slot 13 in the conductor compressing portion 6 of reduced diameter. In this manner, the insulation is kept away from the edge portions of the conductor clamp arms 9 and 10 so as to avoid intrusion of any insulation in slot 13 which would lead to a poor electrical connection when the fastening collar is applied.

In FIGURE 12, a wire 31 is shown in its completely seated position with the center conductor 31 being deformed by both the insertion force of insertion blade 30 (FIGURE 6) and by the camming action of annular rim 25 against the outer periphery of wirereceiving portion 7. FIGURE 12 further indicates that, in the fully assembled position of the fastening collar, the arms 11 and 12 are biased inwardly to a position even closerthan its initial state without a wire inserted. This ensures good electrical connection even when a wire is used which has a diameter approximately the same as the width of slot 13. This figure also shows a biting action between the upwardly directed tips of annular rim 25 and the circular periphery of wire-receiving portion 7.This assures good mechanical retention of the collar 24 even under sever vibrating conditions.

The electrical contact 5 can be used in a connector holding a plurality of such contacts as shown in FIG URES 13 and 14. In these figures, an insulation block 4 holds a plurality of spaced contacts 5, each aligned laterally with wire holding grooves 34 which serve to hold the wires with their axes parallel to the transverse axes of slots 13 as the wires 28 are inserted.

Insertion tool 29 with insertion blades 30 force all wires 28 to the closed end of slots 13 simultaneously, while in a subsequent operation, collar insertion tool 32 with cylindrical holes 33 force a plurality of corresponding collars 24 over the wire receiving ends 7 of contacts 5.

FIGURE 15 illustrates an alternative form of the transverse relief opening at the closed end of slot 13, such opening being in the form of a transverse bore 35 extending across the diameter of conductor compressing portion 6.

FIGURE 16 shows an alternative form for slot 13 having sloped sidewalls 13' which converge toward one another in the direction of insertion of a wire into the slot 13.

Rather than to provide an internal tapered rim 25 as seen in FIGURE 3, FIGURE 17 shows that a more simplified collar 24 can have its entrance opening beveled such that the sides of the cylinder forming collar 24 define the internal tapered rim 25.

Since the contact of this invention is particularly suited for heavy current uses, FIGURES 1-4 show the terminal portion 2,3 as comprising a threaded stud 2 and locking nuts 3 for mounting the contact securely on a rigid contact terminal strip 4 as seen in FIGURE 4. If desirable, the terminal portion of the contact 5 can be in the form of a connector pin 36 which has an attachment section 37 for fastening to the insulation block of a connector and annular groove 38 for retaining a securing ring to maintain the contact in place.

From the foregoing, it can be readily realized that this invention can assume various embodiments.

For example, the contact 5 can be used singly or in multiple contact configurations, can be used by sec uring itto an insulation block of a connector, to a connectorterminal strip, or to the frame of a piece of equipment. Additionally, the strain relief opening 14 and the reduced diameter portion 6 may be omitted without departing from the inventive concept described herein, and the sloping surfaces for guid ing the fastening collar 24 onto wire-receiving por tion 7 are merely preferred improvements, and that other shapes for the connector and other means for guiding the collar over the contact body can be real ized. The invention can be used to terminate both stranded and solid wires, the former being accom modated due to the substantial compressive forces afforded the completely assembled contact. Thus, it is to be understood that the invention is not limited to the specific embodiments described herein, but is to be limited only by the appended claims.

Claims (14)

1. An electrical contactforterminating awire having a central insulated electrical conductor, comprising: an elongated cylindrical-shaped electrical contact body including a terminal means at one end thereof for making connection to an external conductor, and a wire-receiving means at the other end thereof, said wire-receiving means having a transverse slot extending across said body and opening at said other end to define a pair of opposed insulating-piercing jaws for cutting and separating insulation from the central conductor of a wire as the wire enters said slot from said other end, the wire to be inserted having its longitudinal axis normal to the longitudinal axis of said elongated contact body, said slot having a width no greater than the diameter of the central conductor of a wire to be inserted in said wire-receiving means; and a hollow fastening collar dimensioned to snugly fit over said wirereceiving means and to bias said jaws toward one another after insertion of a wire in said wirereceiving means.

2. The electrical contact as claimed in Claim 1, wherein said insulation-piercing means includes a blade formed on the tip of each jaw at said other end, said blades having their edges lying in a plane perpendicularto the plane of said transverse slot, said blades sloping inwardly and away from said other end of said contact body.

3. The electrical contact as claimed in Claim 1, wherein each of said jaws has at least one exterior sloping surface at the periphery of said other end for guiding said collar onto said wire-receiving means.

4. The electrical contact as claimed in Claim 3, wherein said collar has a sloping internal annular rim adapted to engage said sloping surface of said jaws to further aid in guiding said collar onto said wire-receiving means.

5. The electrical contact as claimed in Claim 1, wherein said slot extends axially of said contact body for a predetermined depth, and said contact body has a transverse opening at said predetermined depth, and said contact body has a transverse opening at said predetermined depth to relieve strain at the closed end of said slot due to flexure of said jaws.

6. The electrical contact as claimed in Claim 5, wherein said body has a transverse relief slit extend ing across said contact body at said predetermined depth, said slit being narrower in width than said slot and opening into said closed end of said slot.

7. The electrical contact as claimed in Claim 5, wherein said contact body has a transverse cylindri cal bore extending across said contact body at said predetermined depth, the diameter of said bore being larger than the width of said slot but no larger than the diameterofthe conductor of a wire to be inserted in said wire-receiving means.

8. The electricat contact as claimed in Claim 1, wherein said slot has sloping side walls which merge toward one another in the direction of insertion of a wire into said wire-receiving means.

9. The electrical contact as claimed in Claim 1, wherein said terminal means includes a threaded stud integral with said wire-receiving means.

10. The electrical contact as claimed in Claim 1, wherein said terminal means includes a projecting connector pin integral with said wire-receiving means.

11. The electrical contact claimed in Claim 1, wherein said contact body includes a conductorsompressing portion intermediate said ends and having a diameter reduced from that of the remainder of said contact body, said conductorcompressing portion containing the closed end of said slot for receiving a fully inserted wire to thereby avoid the intrusion of insulation into the closed end of said slot prior to compression of the conductor at said closed end by the insertion of said collar over said wire-receiving means.

12. The electrical contact as claimed in Claim 4, wherein said internal annular rim slopes outwardly in the direction of insertion of a wire being inserted into said contact body, to define a sharp inwardly directed tip which securely engages the periphery of said wire-receiving portion of said contact body in the fully assembled condition of said collar and said contact body.

13. An electrical connector comprising: a connector insulation block; and at least one electrical contact mounted in said insulation block, each of said electrical contacts adapted for terminating a wire having a central insulated electrical conductor, and each of said electrical contacts including an elongated cylindrical-shaped electrical contact body having a terminal means at one end thereof for making connection to an external conductor, and awirereceiving means at the other end thereof, said wirereceiving means having a transverse slot extending across said body and opening at said other end to define a pair of opposed insulating-piercing jaws for cutting and separating insulation from the central conductor of a wire as the wire enters said slot from said other end, the wire to be inserted having its longitudinal axis normal to the longitudinal axis of said elongated contact body, said slot having a width no greater than the diameter of the central conductor of a wire to be inserted in said wire-receiving means; and a hollow fastening collar dimensioned to snugly fit over said wire-receiving means and to bias said jaws toward one another after insertion of a wire in said wire-receiving means.

14. The electrical connector as claimed in Claim 13, wherein said insulation block has a wire holding groove adjacent each electrical contact for holding a wire aligned with said slot as the wire is inserted into said wire-receiving means.