EP0041387A1

EP0041387A1 - Electrical connector for non-prestripped insulated wire ends

Info

Publication number: EP0041387A1
Application number: EP81302410A
Authority: EP
Inventors: Hartmut W. Buyken
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1980-06-03
Filing date: 1981-06-01
Publication date: 1981-12-09
Also published as: BR8103442A; DE3020990C2; JPS57172667A; CA1141833A; DE3020990A1

Abstract

An electrical connector (701) having a sharp contact element (709) that is resilient transverse to its main axis in which when an insulated wire end (707, 743) is inserted into the connector (701) essentially coaxially with the contact element (709) the contact element pierces the wire and is flexed transversely to produce a resilient contact with the conductor.

Description

Background of the Invention

The invention relates to an electrical connector for non-prestripped insulated wire ends, the connector including a housing, at least one guide means for the insertion of a cable end being provided in said housing, and at least one sharp contact element adapted to pierce into the insulated wire end and to thereby be brought into contact with the conductor, said contact element being resilient transverse of the direction of insertion.
In a known device of that kind disclosed in German Auslegeschrift 21 32 870, the contact element is formed by a pair of contact pins which are arranged in a plane extending transverse of the guide means and of the wire end to be connected. To make the connection, the wire end must be inserted into the guide means, and thereafter, the contact element must be moved transversely of the direction of insertion. In doing so, the contact pins cut through the insulation of the cable end and come into contact with the conductor. In order to ensure sufficient contact force over extended periods of time, the contact pins are partly resiliently deformable and are supported by a centering device against the spreading forces occurring upon the piercing. Despite that measure, the permanent safety and the electrical load rating of the contacts made in that manner are insufficient for many applications; this is particularly true for electrical installations in dwelling houses, in which relatively high current loads may occur, and a trouble-free and maintenance-free operation must be ensured over many years. Moreover, the af.oredescribed connectors require a relatively large space corresponding at least to the insertion and piercing movements of the cable end and the contact element. In order to ensure the proper relative position and movement of cable end and contact element upon making the connection, the known connector requires a relatively expensive construction; this also makes an economic mass production difficult or practially impossible.
The prior art also includes devices in which non-prestripped wire ends having stranded conductors can be inserted into cylindrical guides of a conductor housing at the bottom of which a contact element in the form of a pointed pin is arranged coaxially so that upon the insertion of the wire end, the pin will be axially piercing into the stranded conductor, as disclosed in U.S. Patents Nos. 2,353,732 and 4,091,233. In those devices,-however, no resilient contact force is exerted between the contact and the conductor as is necessary to meet the requirements with respect to contact safety, durability and current rating as are typical for power current distribution systems, particularly for house installation and household appliances. The same is also true for the device of German Offenle- gungsschrift 23 10 022 in which the end of a stranded conductor insulated wire is shifted onto a pointed contact pin. In doing so, a contact force acting transversely of the shifting direction is obtained only from the expansion of the insulation. This is insufficient to obtain a high load contact which is safe over long periods of time, because most plastic materials have a tendency for cold flow.

Summary of the Invention

The present invention provides a connector for insulated wire in which the contact element is designed and arranged stationarily in the housing such that it pierces essentially axially into the wire end upon the insertion of the latter, and in doing so, is flexed transversely to produce a contact force.
Due to the stationary arrangement of the contact element in the housing, the connector according to the invention does not require any provisions for movably guiding the contact element; also the space requirement therefor is obviated. For making the contact, only a single movement, the insertion of the cable end, is necessary. Thereby, structure and handling are simplified. The contact force is determined by the resilient properties of the contact element, which are exactly predeterminable within wide limits, and therefore can be easily held above a desired minimum value over long periods of time. The magnitude of the contact force obtained is not limited by the diameter of the conductor; thus, with one and the same contact element, sufficiently large contact surfaces for high current loads can be readily obtained.
The connector according to the invention, due to its inherent structural simplicity and small dimensions, can be readily employed within electrical appliances, in plugs, wall sockets, connection boxes and similar structural parts. Because of its small space requirements, the connector is particularly suited for making connections to multi-core cables, flat cables, coaxial cables, and the like.
The finished connection can be again disconnected, and the connector can be re-used. Particularly the embodiments for stranded conductors are suitable for a range of different conductor cross-sections. The manufacture of the conductor can be easily automated. The structure of the conductor is well suited for modular embodiments, a plurality of which can be conveniently associated together to form groups of almost any size.

Brief Description of the Drawings

The invention will be subsequently described in more detail by means of embodiments in connection with the drawings, in which

Figure 1 is a diagrammatic illustration of the basic structureand the mode of operation of a connector according to the invention, in the manner of an axial section,
Figure 2 is an illustration corresponding to Figure 1, however, for a connector with a solid conductor wire end inserted,
Figure 3 is an illustration, corresponding to Figure 1, of a second embodiment.
Figure 4 is an illustration corresponding to Figure 3, but with a stranded conductor wire end inserted,
Figure 5 is a sheet metal stamping for manufacturing a contact element for a third embodiment of a connector according to the invention,
Figure 6 is a contact element produced from the sheet metal stamping according to Figure 5 by bending,
Figure 7 is a diagrammatic perspective view of the third embodiment with some of the constituents partly broken away, and
Figure 8 is a diagrammatic perspective illustration of another embodiment of a contact element.

Detailed Description of the Drawings

Figure 1 shows an electrical connector 1 having a housing 3, a cylindrical guide 5 for the insertion of a non-prestripped wire end 7, and a resilient sharp contact element 9 which is secured in the housing 3 and projects in the direction of the axis 11 of the guide 5 into the guide 5. The non-prestripped wire end 7 has a solid conductor 13 having a circular cross-section, and insulation 15 surrounding the conductor 13. The insulation is, for example, polyethylene or a similar material. The resilient sharp contact element 9 is arranged stationarily in the housing 3 such that upon the insertion of the wireend 7 into the guide 5, it pierces axially into the wire end 7 between conductor 13 and insulation 15. The contact element 9 has two pointed legs 17 and 19 which extend in the axial direction of the guide 5 and have knife-like, sharp interior edges 21 and 23. The legs 17 and 19 are pointed at their free ends, and at their other ends, they merge integrally into a web portion 25 which in the simplest case may be formed by a flat or cylindrical piece of sheet metal which is secured in the housing 3 in a press fit. In order to facilitate the insertion of the wire end 7, the guide 5 has a conical enlargement 27 at its free end. The dimensions of the contact element 9 and particularly of its legs 17 and 19 are matched with the radial dimensions of the conductor 13 and the insulation 15 of the cable to be inserted so that upon pushing- in of the cable, the points 29 and 31 of the legs pierce axially into the wire end between conductor 13 and insulation 15, and the legs 17 and 19 are radially spread against the spring force exerted by them.
Figure 2 illustrates the condition after the piercing of the conductor end 7. In Figure 2, the pointed ends 29 and 31 of the legs 17 and 19 are illustrated in a slightly perspective view in order to illustrate an embodiment which is advantageous with respect to the contact surface obtained; that embodiment is characterized in that thelegs have essentially a V-shaped cross-section which is open towards the axis 11 of the guide 5. It may be seen from Figure 2 that in the inserted condition, the sharp edges 21 and 23 (which each are present twice in the embodiment illustrated in Figure 2, because of the V-shaped cross section of the legs} have come into contact with the conductor 13 over a relatively great axial length. Since the legs 17 and 19, are resilient, a resilient contact force is obtained by the slight spreading of the legs, which force will take care of maintaining a safe contact over long periods of time. As may be further seen from Figure 2, the portions of the insulation which have.been displaced by the legs 17 and 19 may produce an additional radial contacting pressure if they consist of a correspondingly resilient material, which is the case with many plastic insulation materials.
Figures 3 and 4 illustrate another embodiment in views which basically correspond to Figures 1 and 2. Parts which are present in a corresponding manner in Figures 1 and 2, are designed by the same reference numerals used in Figures 1 and 2, with the prefix "3".
The embodiments according to Figures 3 and 4 are designed for a wire end 307 having a stranded conductor 313. In such case, the piercing of the contact element 309 need not be restricted to the areas between the conductor 313 and the insulation 315. The resilient contact element 309 has a plurality of pointed legs 317, 319, 333, 335 which extend essentially in the axial direction of the guide 305 and are dimensioned and arranged in correspondence with the dimensions of the wire end 307 so that they pierce axially into the conductor 313 when the wire'end 307 is pushed into the guide 305.
Figure 4 shows that in inserting the wire end 307, the legs will be radially spread due to their pointed shape and the space which they require. Since the contact element 309 is designed resiliently, the legs exert radial contact forces onto the parts of the conductor 313 engaged by them, and this over a relatively large axial length. A relatively large contact surface is obtained which, combined with the spring contact force of the legs, results in an electrical connection which may carry high electrical loads and will operate trouble-free over long periods of time. As may be further seen from Figure 4, in this embodiment the insulation 315 may also contribute in the exertion of a contact pressure directed radially inwards, if the insulation consists of a correspondingly resilient material. The same is also true for the guide 305.
As may be further seen from Figures 3 and 4 the pointed legs 317, 319, 333, 335 merge integrally into a web portion 325. In this embodiment, as well as in the embodiment according to Figures 1 and 2, the resilient contact element may be formed from a single piece of sheet metal.
Figures 5 and 6 illustrate that even resilient contact elements of more complicated shape may be manufactured from sheet metal by bending. The entire contact manufacturing process will then require only stamping and bending steps and thus will be particularly suited for mass production.
The sheet metal stamping illustrated in Figure 5 consists of spring bronze or a similar suitable electrically conductive material having permanently elastic properties and a spring constant which is sufficient for obtaining the desired contact pressures.
Figure 6 shows the finished contact element 609 which has been made from the sheet metal stamping of Figure 5., This contact element has pointed legs which point in two opposite directions; the legs 617, 619 pointing in one direction, and the legs 637, 639 in the opposite direction. It will be understood that one-piece sheet metal stampings and resilient contact elements made therefrom by bending may be also designed with legs pointing in one direction only. Also, more complicated resilient contact elements may be made in a similar manner from one-piece sheet metal stampings. For example, contact elements which have a plurality of side-by-side- arranged groups of sharpened and/or pointed legs, of which each group is designed to pierce into a wire end.
Figure 7 illustrates in a diagrammatic perspective partial view with portions partly broken away, an embodiment of a connecting connector, in which the contact element 609 illustrated in Figure 6 is employed. In order to avoid repetitions, parts which also appear in a corresponding manner in Figures 1 and 2 are designated with the same reference numerals as there, however, with the prefix "7".
The connector illustrated in Figure 7 has at least one pair of mutually aligned guides 705, 741, each for the insertion of one wire end 707 and 743, respectively, from opposite directions. The guides are each formed by the bottom 745 of the housing 703, and bordering walls 747, 749 and 751, 753, respectively. The connector 701 illustrated in Figure 7 has selectively operable retaining devices for securing the inserted cable ends. A retaining device 755, 759 is associated with each of the guides 705 and 741, respectively. Each retaining device has a pivotable wire clamp 761 or 763, respectively, which is designed to simultaneously exert an inwards shifting force on the wire end 707 or 743, respectively. To that end, each wire clamp is pivotable about a pivot axis 767, 769, respectively, extending transversely of the direction of insertion. Each wire clamp has a toothed clamping portion 771, 773, respectively, and a gripping portion 775 and 777, respectively. The gripping portions 775, 777 project through housing openings of which only the housing opening 779 associated with the gripping portions 775 is illustrated in Figure 7. The wire clamps have insertion openings 781 and 783, respectively, in their gripping portions, into which a tool, particularly a screwdriver, can be inserted in order to obtain a larger moment of force for pivoting the wire clamps.
In Figure 7, the wire clamp 761 is illustrated in the clamped position, and the wire clamp 763 in the released position. Each of the wire clamps is held in the clamping position by arresting means, which, in the illustrated embodiment, comprise oblique or hemi- spherical projections 785, 787 that cooperate with depressions or recesses (not illustrated) in the associated side walls of the housing 703. As will be readily understood, an inserted wire can be securely clamped by a clamping portion by pivoting the wire clamp downwards. In Figure 7, that condition is indicated with the inserted wire 707. As may be readily seen, an inwards shifting force is exerted on the wire end upon the clamping thereof, and this occurs at a point close to the free end, which can no longer be gripped manually. In this manner, an extraordinarily large inwards shifting force can be exerted without deforming the wire end. Then, a correspondingly large contact force is obtained.
As will be readily recognized, a plurality of connectors of the kind illustrated in Figure 7 may be arranged side-by-side in a common housing, and, if desired, additionally separated from each other by separating walls.
Figure 8 illustrates, in a diagrammatic perspective view, a contact element 809 which, as the contact element 609 of Figures 6 and 7, can be made from a one-piece sheet metal stamping by bending. This contact is, however, also suitable for solid conductor wires. As the contact element according to Figures 1 and 2, it comprises resilient sharp legs which are arranged so as to pierce between the conductor and insulation of the wire end (not illustrated in Figure 8). In this case, three legs 817, 818, 819 are provided depending integrally from a web portion 825 which is bent to form a ring. Preferably, the ring is closed in an overlap area 826, with the overlapping parts of the web portion 825 being interconnected, by welding or hard soldering, to rigidify the contact element 809. The legs each have an approximately V-shaped cross-section and are pointed outwards at their free ends to facilitate the piercing between insulation and conductor. In the embodiment illustrated, the V cross-sections extend into the web portion; the thus-caused bending lines 889, 891 further increase the stiffness of the contact element 809. Of course, contact elements of the kind illustrated in Figure 8 also may be designed to pierce into two opposite directions, for instance as illustrated in Figures 6 and 7.

Claims

1. An electrical connector for non-prestripped insulated wire ends, the connector including a housing, at least one guide means for inserting a cable end being provided in said housing, and at least one sharp contact element adapted to pierce into the non-prestripped wire end and to thereby be brought into contact with the conductor of the cable, said contact element being resilient transverse of the direction of insertion, characterized in that the resilient sharp contact element (9) is designed and arranged stationarily in the housing such that it pierces essentially axially into the wire end upon the insertion of the latter, and in doing so, is flexed transversely to produce a contact force.

2. A connector according to claim 1, characterized in that the resilient sharp contact element (9) comprises at least two pointed legs (17, 19) extending essentially in the axial direction of the guide (5) for piercing axially between the conductor (13) and insulation (15) of the wire end (7).

3. A connector according to claim 1 or 2, characterized in that the legs (17, 19) comprise knife-like sharp interior edges (21, 23).

4. A connector according to claim 3, characterized in that the legs (17, 19) essentially have a V-shaped cross-section which is open towards the axis (11) of the guide (5).

5. A connector according to claim 1 for wires having stranded conductors, characterized in that the resilient contact element (309) comprises a plurality of pointed legs (317, 319, 333, 335) extending essentially in the axial direction of the guide (305) for piercing axially into the conductor (313).

6. A connector according to claim 1, 2 or 5 characterized in that the resilient contact element is a one-piece sheet metal part.

7. A connector according to claim 1 characterized in that the housing comprises at least one pair of mutually aligned guides (705, 741) for inserting a wire end (707, 743) each from opposite directions, and in that the resilient contact element (709) is stationarily arranged centrally and is designed to pierce axially into both wire ends.

8. A connector according to claim 1 or 7, characterized by a selectively operable retaining device (755, 759) for securely clamping the inserted wire end (707, 743).

9. A connector according to claim 8, characterized in that the retaining device comprises a gripping portion projecting through the housing opening and adapted to be actuated from the outside.

10. A connector according to claim 8, characterized in that the retaining device is designed for exerting an inward shifting force on the wire end.