GB1585345A

GB1585345A - Electrical connector having displaceable sidewall terminal element

Info

Publication number: GB1585345A
Application number: GB15246/78A
Authority: GB
Original assignee: Bunker Ramo Corp
Current assignee: Bunker Ramo Corp
Priority date: 1977-04-18
Filing date: 1978-04-18
Publication date: 1981-02-25
Also published as: DD135785A5; JPS638589B2; CH628185A5; AU3499878A; IN149888B; BE866102A; IL54479A0; NO781336L; AU514129B2; JPS53129861A; ZA782200B; IT7822425A0; NL7803964A; FI781144A; PL116554B1; DE2815890A1; SE432036B; DK168878A; SE7804040L; FR2388421A1

Abstract

The electrical connector has a connecting part (10) which is in the form of an elongated groove with a U-profile and is inserted into a contact socket (34). The mutually opposite side walls (12, 14) are connected to one another at specific points by means of a base (16). Each side wall has an elastically deformable region (18) on which inward bends are arranged. The insulation of a conductor which is intended to be pressed in between such bends is cut into by means of inclined surfaces (28) of opposite inward bends. The inclined surfaces (28) have a cutting edge at their upper end for this purpose. Connected to the surfaces (28) at the bottom is a connecting part (29) which forms a flat rubbing surface which engages on the conductor. The lateral dimension of the connecting part in the elastically deformable region (18) exceeds the internal dimensions of the contact socket (34) so that, in the installed state, it is in pressing contact with the walls of said socket. A portion of the forces exerted during insertion of a conductor (C) is thus absorbed by the contact socket (34). <IMAGE>

Description

(54) ELECTRICAL CONNECTOR HAVING DISPLACEABLE SIDEWALL TERMINAL ELEMENT (71) We, BUNKER RAMO CORPORATION, a Corporation organised and existing under the laws of the State of Delaware, United States of America, of 900 Commerce Drive, Oak Brook, Illinois, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- Electrical connectors having insulationpiercing contacts are well known in the art and have met with considerable commercial success. Typical examples of such prior art connectors are illustrated in U.S. Patent Specifications Nos. 3,867,005 and 3,926,498.

The contacts employed in these connectors generally include terminal elements which sever or cut through the insulation and establish an electrical connection with the conductor without the need for any stripping or soldering operation. The insulation-piercing terminal elements typically include opposed cutting edges that sever and penetrate the insulation and serve as wiping surfaces, in some configurations, to make the necessary electrical connection with the conductor. The insulation-piercing terminal therefore serves both to sever the insulation and establish an electrical connection with the conductor.

As mentioned above, the prior art insulation-piercing connectors have met with considerable commercial success. Nevertheless, certain problems arising in the fabrication of the miniaturized electrical components used in these connectors have resulted in designs which compromise the optimum performance characteristics which could otherwise be attained. Por example, since the insulationpiercing contacts may be most economically manufactured by press and stamping operations it is necessary to use sheet metal stock which is easily formable. Such sheet metal stock has a tensile strength which is less than that generally considered optimal for withstanding the forces encountered in the connection operation. Accordingly, certain of the structural components of prior art contacts which comprise the insulation-piercing terminal elements may be in some instances deformed or bent in the connecting operation to the point where proper electrical connection may be adversely affected. In addition, because of tolerance ranges required to minimize the cost of manufacture and to facilitate assembly, a small space often exists between the sidewalls of the contact and the lateral surfaces of the insert cavity in which the contact is mounted. Thus, the sidewalls have little or no lateral support and are susceptible to outward lateral deformation during the connecting operation, thereby further jeopardizing the quality of the electrical connection obtained.

Another problem associated with prior art insulation-piercing connectors is that they are not well suited to stranded core conductors.

Oftentimes, individual strands of such conductors snag on, or are severed by, the opposed cutting edges of the insulationpiercing terminal element. In addition, cold flow of the insulation, subsequent to termination can result in movement of the individual strands and changes in the engagement area and force between the conductor and the sidewalls of the contact. Therefore, when utilizing stranded core conductors, the quality of both the electrical and mechanical connection attained with prior art connectors may be seriously impaired.

The present invention is therefore directed to an electrical contact which overcome the aforementioned problems relating to the deformation of the force bearing components of the contact and which can be designed to minimize the snagging and severing problems sometimes encountered in the connection of insulated, stranded core conductors.

According to the present invention there is provided an insulation-piercing contact for electrical connection to an insulation-covered conductor, the contact comprising a pair of opposed sidewalls to receive the insulated conductor longitudinally therebetween, a pair of opposed - protuberances, one on each sidewail, which form a conductor-receiving notch and penetrate the insulation and make electrical connection with the conductor when the insulation-covered conductor is forced between the sidewalls, into the notch, at least one of the protuberances being on a portion of the respective sidewall which is transversely displaceable relative to the remainder of the sidewall.

The various parts of the contact can be so dimensioned relative to each other and the conductor being terminated as to minimize the changes in termination resistance which typically occur when stranded core conductors are terminated with conventional contacts.

The contact can overcome the problems associated with prior art devices since the sidewalls of the contact which must withstand the lateral forces generated by the insertion of the insulated conductor are designed to positively engage and bear against the lateral surfaces of the contact mounting cavity. In this manner the strength and rigidity of the relatively thick walls of the contact mount of the connector are utilized to withstand the connection forces, and a contact of relatively low tensile strength may be employed without adversely affecting the quality or character of the electrical connection obtained. Therefore, relatively low tensile strength sheet metal stock may be employed in the contact elements, thereby greatly facilitating their fabrication.

The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view illustrating a terminal element of a contact embodying the present invention and for use in an electrical connector; FIGURE 2 is a fragmentary perspective view of the terminal element of FIGURE 1 illustrating in greater detail one of the protuberances or detents which act to open or displace the insulation and make electrical connection with the conductor; FIGURE 3 is a plan view of the terminal element shown in FIGURE 1; FIGURE 4 is a partial cross-sectional view showing the contact within a contact mounting cavity of an electrical connector and further showing an insulated stranded core conductor positioned above the contact member immediately prior to the connection operation; FIGURE 5 is a cross-sectional view similar to that of FIGURE 4 showing the insulated stranded core conductor in final position within the contact member with the protuberances of the contact member having opened and displaced the insulation and making electrical contact with the stranded core of the conductor; FIGURE 6 is a view similar to that of FIGURE 1, but showing a preferred embodiment of the present invention; FIGURE 7 is a fragmentary perspective view of the terminal element of FIGURE 6; FIGURE 8 is a plan view of the terminal elements shown in FIGURE 6; and FIGURE 9 is a fragmentary side view of the terminal element shown in FIGURE 6.

Referring now to FIGURES 1 to 3 of the drawings, a terminal element 10 of a contact member is illustrated comprising a channel having an elongated U-shaped configuration.

The channel includes opposed sidewalls 12 and 14 and a bottom wall 16 which joins at least a portion of the sidewalls 12 and 14 to one another. Each sidewall 12 and 14, respectively, includes a displaceable portion 18 which carries at least one inwardly extending protuberance or detent 20. The protuberances 20 on each sidewall 18 are aligned to form conductor-receiving notches adapted to penetrate the insulation and establish electrical connection with a conductor. The portions 18 of each sidewall are displaceable transversely relative to one another. In their initial position, as can be most clearly seen in FIGURE 3, the portions 18 of each sidewall 12 and 14, respectively, are bowed outwardly. Preferably, the displaceable portions 18 are positioned intermediate generally stationary end portions 22 and 24. In addition, portions 18 are separated from bottom wall 16 by apertures 26, thereby allowing their transverse displacement. The stationary end portions, 22 and 24, together with the bottom wall 16, give the terminal element 10 the desired rigidity for successful operation in the connector.

The protuberances 20 are integrally formed in the displaceable portions 18 of the respective sidewalls and include an upper, insulation piercing portion 27, having an inclined surface 28 and a lower conductor wiping portion 29 having a generally planar wiping surface 30.

The inclined surfaces 28 of each respective pair of protuberances 20 form an entry-way to the conductor-receiving notch formed by the protuberances. The inclined surfaces 28 terminate in an upper, cutting edge 32 which is remote from the wiping surface 30 and which serves to initially penetrate the insulation on the conductor as it is inserted into the terminal element 10 of the contact member. In any given conductor-receiving notch, the cutting edges 32 are spaced a distance greater than the diameter of the conductor core but less than the diameter of the conductor insulation. Thus, the protuberances 20 are approximately half closed at their conductor-receiving upper surface.

It will be appreciated by those skilled in the art that the smooth inclined surface 28, together with the location of cutting edge 32 spaced or remote from the wiping surface 30 and the longitudinal centre line of the terminal element 10, serves to enhance the quality of the connection obtained since the snagging or "hang-up" encountered with stranded conductors is substantially eliminated. In addition, since the displaceable portions 18 of each sidewall are separated from the bottom wall 16 by the slots or apertures 36, the displaceable portions remain generally perpendicular to bottom wall 16 regardless of their relative positions. The wiping surfaces 30 of protuberances 20 also remain generally parallel to one another.

It should also be noted that the inclined surfaces 28 are generally planar and sufficiently wide to ensure the proper removal of the bulk of insulation from the metallic core of the conductor as it is forced into the terminal element 10. The surfaces 30 are also generally planar and sufficiently wide so as to remove any residual insulation film from the core and to provide a clean surface on the core to establish optimal electrical contact.

An alternative and preferred construction for the protuberances 20 is illustrated in FIGURES 6 to 9. In accordance with this embodiment, the insulation displacing portion 27 is enlarged such that its dimension along the longitudinal axis of the terminal element 10 (arrow a, FIGURE 8) is greater than the same dimension (arrow b, FIGURE 8) of the conductor wiping portion 29'. Accordingly, insulation is displaced or stripped from a longer segment of the conductor than is actually engaged by the conductor wiping surface 30'. It has been found that this arrangement improves the electrical quality of the termination, particularly when using stranded core conductors.

It has also been discovered that the dimensions of the protuberances 20, relative to the size of the conductor C, play an important part in optimizing the quality of the termination. In order to assure proper insulation removal, the insulation displacing portion 27 of the protuberances should have a vertical dimension (arrow c,;FIGURE 4) at least as great as the radius of the conductor being terminated. In addition, in order to properly clean the exposed conductor core, the conductor wiping portion 29 of the protuberances 20 should have a vertical dimension (arrow d, FIGURE 4) at least as great as the diameter of the conductor. Finally, the inclined surface 28 should form an angle with the vertical longitudinal plane of the terminal element 10 (angle e, FIGURE 4) of about 35 degrees.

The above-described terminal element 10 forms a portion of a contact member which is used in conjunction with a contact mount of an electrical connector. The specific structural features of the contact mount and the other connector components and the assembly of the contact member with the connector are illustrated in greater detail in the above-mentioned US. Patent Specification No. 3,867,005. Generally, the contact includes both a terminal element and an active contact element (i.e. a part which mates with another contact in another connector) which are disposed within a contact mount 34 made of dielectric material. The contact mount includes an elongated contact mounting cavity 36 having a generally U-shaped configuration with inner and outer ends, the terminal element 10 of the contact member being disposed within the outer end of the cavity.

It will be appreciated that in order to facilitate the assembly of the connector it is necessary that the contact mounting cavity and the terminal element be dimensioned within narrow tolerances. Nevertheless, in prior art connectors a small space often exists between the lateral surfaces of the contact mounting cavity and the sidewalls of the terminal element. This spacing is undesirable in that it allows the sidewalls to spread apart upon the insertion of the insulated conductor therebetween. The connector constructed in accord with the present invention overcomes this problem.

In order to ensure that the terminal element 10 has sufficient lateral support to withstand the forces encountered during connection of the conductor C, the portions 18 of the terminal element 10 are bowed outwardly to have an initial pre-assembly transverse dimension which is greater than that of the contact mounting cavity 36. Of course, the transverse dimension of the terminal element at the stationary end portions 22 and 24 is less than that of the cavity 36. Exemplary dimensions for the terminal element 10, for use in a cavity having a 0.053 inch width, include a width at the stationary portions (arrow f, FIGURE 3) of 0.050 inch and an initial pre-assembly width at the displaceable portion (arrow g, FIGURE 3) of 0.ops inch.

Accordingly, when the contact member is inserted into the contact mount 34 during assembly of the connector, the portions 18 of the terminal element 10 are displaced inwardly to a final, assembled portion in which the sidewalls 12 and 14, at the displaceable portions 18 bear directly against the lateral surfaces 38 and 40 of the cavity 36. Thus, the terminal element 10 is disposed within the contact mounting cavity 36 in press-fit relationship without any spacing between the lateral surfaces 38 and 40 and the sidewalls 12 and 14. In addition, the protuberances 20 have substantial support on each side thereof, at the points 21 where the protuberances join their respective sidewalls.

As is clearly illustrated in FIGURE 5, when the conductor C is forced into the terminal element 10 by means of an appropriate insertion tool 42 the insulation is stripped from the core of the conductor and the wiping surfaces 30 of protuberances 20 engage the core to provide the desired electrical connection.

The construction of the contact in accordance with the present invention, prevents the outward displacement of sidewalls 12 and 14 as is sometimes encountered in prior art connectors. Thus, the transverse dimension of the conductor-receiving notch (represented by the double headed arrow in FIGURE 5) remains generally constant and uniform during the connection operation, thereby ensuring proper electrical connection even with stranded core conductors. In addition, the cutting edge 32 on each protuberance 20 is spaced a sufficient distance outwardly from the centreline to terminal element 10 to ensure that the stranded core of the conductor does not hang-up. Moreover, the danger of individual strands of the core being severed by the cutting edge 32 is greatly reduced.

Since the connector relies upon the strength of the dielectric contact mount to support the sidewalls of the terminal element, the contacts may be fabricated from relatively low tensile strength sheet metal stock without adversely affecting the quality of the electrical connection obtained. In addition, since the sidewalls of the terminal element are transversely displaceable, the dimensional variations in both the contacts and contacting mounting cavities become less critical.

Of course, it should be understood that various changes and modifications to the preferred embodiments described herein will be apparent to those skilled in the art. For example, the displaceable portion 18, may be used in only one sidewall of the terminal element and structural configurations other than the disclosed three-side channel may be employed to position and align the opposed sidewalls 12 and 14.

WHAT WE CLAIM IS: 1. An insulation-piercing contact for electrical connection to an insulation-covered conductor, the contact comprising a pair of opposed sidewalls to receive the insulated conductor longitudinally therebetween, a pair of opposed protuberances, one on each sidewall, which form a conductor-receiving notch and penetrate the insulation and make electrical connection with the conductor when the insulation-covered conductor is forced between the sidewalls, into the notch, at least one of the protuberances being on a portion of the respective sidewall which is transversely displaceable relative to the remainder of the sidewall.

2. A contact as claimed in Claim 1, wherein the sidewalls are joined by a bottom wall, thereby forming an elongated channel, the displaceable portion of the or each sidewall being separated from the bottom wall.

3. A contact as claimed in Claim 2, wherein each protuberance comprises a detent having an inclined surface and a generally planar wiping surface, the inclined surfaces of the pair of protuberances forming an entry-way to the notch.

4. A contact as claimed in Claim 3, wherein said detents further include cutting edges on the inclined surfaces spaced from the wiping surfaces.

5. A contact as claimed in Claim 4, wherein the wiping surfaces of a pair of protuberances are generally parallel to each other regardless of the position of the displaceable portion(s).

6. A contact as claimed in Claim 1, wherein each protuberance comprises a detent integrally formed in the respective sidewall and includes an insulator displacing portion and a conductor wiping portion, the insulation displacing portion having a dimension along the longitudinal axis of the channel greater than that of the conductor wiping portion.

7. A contact as claimed in Claim 1, wherein each said protuberance comprises a detent integrally formed in the respective sidewall and includes an insulation displacing portion and a conductor wiping portion, the insulation displacing portion having a size and configuration such that the insulation is displaced from a substantially greater segment of the conductor than is contacted by the conductor wiping portion.

8. A contact as claimed in Claim 1, wherein each protuberance comprises a detent integrally formed in the respective sidewall and includes an insulation displacing portion having an inclined surface and a conductor wiping portion, the insulation displacing portion having a vertical dimension not less than the radius of the insulation-covered conductor, the conductor wiping portion having a vertical dimension not less than the diameter of the insulation-covered conductor, the inclined surface being disposed about 35 degrees from the vertical longitudinal plane of the channel.

9. A contact according to any of Claims 1 to 8, further including a part which, in use, mates with another contact.

10. An elecrical connector for interconnecting electrical circuits including insulationcovered conductors, the connector comprising a contact mount of electric material having at least one elongated contact mounting cavity with inner and outer ends and a contact according to Claim 9 mounted in the cavity.

11. An insulation-piercing contact substantially as hereinbefore described with reference to and as illustrated in FIGURES

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. outward displacement of sidewalls 12 and 14 as is sometimes encountered in prior art connectors. Thus, the transverse dimension of the conductor-receiving notch (represented by the double headed arrow in FIGURE 5) remains generally constant and uniform during the connection operation, thereby ensuring proper electrical connection even with stranded core conductors. In addition, the cutting edge 32 on each protuberance 20 is spaced a sufficient distance outwardly from the centreline to terminal element 10 to ensure that the stranded core of the conductor does not hang-up. Moreover, the danger of individual strands of the core being severed by the cutting edge 32 is greatly reduced. Since the connector relies upon the strength of the dielectric contact mount to support the sidewalls of the terminal element, the contacts may be fabricated from relatively low tensile strength sheet metal stock without adversely affecting the quality of the electrical connection obtained. In addition, since the sidewalls of the terminal element are transversely displaceable, the dimensional variations in both the contacts and contacting mounting cavities become less critical. Of course, it should be understood that various changes and modifications to the preferred embodiments described herein will be apparent to those skilled in the art. For example, the displaceable portion 18, may be used in only one sidewall of the terminal element and structural configurations other than the disclosed three-side channel may be employed to position and align the opposed sidewalls 12 and 14. WHAT WE CLAIM IS:

1. An insulation-piercing contact for electrical connection to an insulation-covered conductor, the contact comprising a pair of opposed sidewalls to receive the insulated conductor longitudinally therebetween, a pair of opposed protuberances, one on each sidewall, which form a conductor-receiving notch and penetrate the insulation and make electrical connection with the conductor when the insulation-covered conductor is forced between the sidewalls, into the notch, at least one of the protuberances being on a portion of the respective sidewall which is transversely displaceable relative to the remainder of the sidewall.

1 to 5 of the accompanying drawings.

12. An insulation-piercing contact substantially as hereinbefore described with reference and as illustrated in FIGURES 6 to 9 of the accompanying drawings.