EP0828314A1

EP0828314A1 - Screwless electrical contact device

Info

Publication number: EP0828314A1
Application number: EP97115354A
Authority: EP
Inventors: Per Huse
Original assignee: Elektrokontakt AS
Current assignee: Elektrokontakt AS
Priority date: 1996-09-10
Filing date: 1997-09-04
Publication date: 1998-03-11
Also published as: HUP9701490A2; HU9701490D0; NO963800A; PL321998A1; NO301567B1; HU218123B; NO963800D0; HUP9701490A3

Abstract

Screwless electrical contact device for connecting one or more bare conductors thereto, comprising a main part (4) consisting of an electrically well conductive metal, formed from sheet material and having contact areas (7,7A) for cooperation with an inserted conductor (2). A spring element (9,9A) is adapted to press an inserted conductor (2) against the contact areas (7,7A) and formed with an edge or the like for blocking against inadvertent retraction of the conductor (2). A backing element (8) is located opposed to at least an inner portion (7) of the contact areas (7,7A) and converges towards the inner portion (7) at such spacing and such direction that the end (2A) of an inserted conductor (2) is urged into engagement with the contact areas (7,7A).

Description

This invention relates to a screwless electrical contact device for connecting one or more bare conductors thereto.

Previously known designs of such contact devices can comprise a main part consisting of an electrically well conductive metal, formed from sheet material and having contact areas for cooperation with an inserted conductor, and a spring element adapted to press an inserted conductor against the contact areas and formed with an edge or the like for blocking against inadvertent retraction of the conductor.

Contact devices of the kind being of interest here, are usually designed for being able to receive electrical conductors having dimensions within a certain range, for example from 1,5 til 2,5 mm² for common house installations. The contact areas or portions in these devices can have adjacent or associated lateral backing portions and the contacts themselves can be formed more or less as suitable cradles for the conductor or conductors concerned.

It may be of substantial significance that such contact devices provide for a secure and reliable contact, that besides shall operate satisfactorily through longer times, most often many years. In this connection it is a factor of interest that the spring element incorporated in the structure should not carry any significant current, since such current flow may be detrimental to the spring material.

A problem which may arise with such screwless contacts is due to the fact that during installation work electric fitters often will have to bend connected wires and thereby the conductors therein, quite much depending, inter alia, on the available space. Such bending of the conductor may, according to the circumstances, have influence on the portion of the conductor being inserted into the contact device, so that this can be bent somewhat away from the contact area to be engaged by the conductor. Accordingly the contact can be poor and a risk of failure arises. Experience has shown that this problem occurs quite often in practice, and has not been solved in any previously known contact devices for screwless operation.

On the above background and in a screwless electrical contact device as referred to in the introduction to this description, the invention provides a structural design having novel and specific features consisting in a backing element located opposed to at least an inner portion of the contact areas and converging towards said inner portion at such spacing and such direction that the end of an inserted conductor is urged into engagement with the contact areas.

The solution according to the invention eliminates the problem discussed above, at the same time it is simple and advantageous with respect to its production.

In the following description the contact device according to the invention will be explained more closely with referance to the drawings, wherein:

Fig. 1: shows a longitudinal section through a main part of an embodiment of the contact device according to the invention, with a conductor inserted, and
Fig. 2: shows the main part in Fig. 1 without a conductor, but completely assembled in a surrounding housing.

In a longitudinal section corresponding to the direction of insertion of a conductor 2 belonging to an electric wire 1, there is shown a main part 4 having substantially a U-shape in the cross sectional illustration, where one of the legs is formed with contact portions or

areas

7 and 7A being adapted to cooperate with the portion of the conductor 2 being inserted for obtaining contact. Through a cross member 6 which constitutes the bottom of the U-shape, the main part continues in another or opposite leg 5. Cross member 6 has an entering hole 3 for conductor 2. Inside the U-shape there is mounted a spring element having a back part 9A adapted to engage the inside of U-leg 5, possibly in a depressed or profiled portion thereof. Preferably the back part 9A of the spring element is fixed by clamping in the position shown. In contrast thereto a freely cantilevered part 9 of the spring element is adapted to be urged against conductor 2, the outer end of spring element 9 having a sharp edge or bit which can secure that conductor 2 when being inserted, is blocked against inadvertent retraction.

In actual practice however, it will not be expedient or possible to employ such a

strong spring element

9, 9A that this can prevent the previously discussed problems of bending of conductor 2, resulting in a poor contact between this and

contact areas

7, 7A. A consideration to be taken into account here, is that spring element 9 must not represent any strong impedance against insertion of a conductor 2, i.e. with spring element 9 in the position shown in Fig. 2.

Thus, according to the invention in the embodiment shown in the drawing, there is provided a backing element 8 as a continuation of the first U-leg having the

contact areas

7 and 7A, whereby the sheet material is bent back so that the backing element 8 extends over some distance opposed to at least the inner portion 7 of the contact areas and converges inwardly. When inserting a conductor 2, the end thereof will be captured by the converging portion and ultimately will arrive in a fixed or blocked position as shown at the end 2A of conductor 2 in Fig. 1. In this way it is secured that bending of the conductor or wire 1 during mounting can not lead to any movement away from

contact areas

7, 7A, so that the contact will be secured both at short and long term.

Depending on the conductor dimension the conductor end 2A will be arrested in an end position more or less far inserted into the converging portion between the backing element 8 and

contact areas

7, 7A.

In the complete device of Fig. 2 the main part 4 is mounted in a surrounding housing 10, in which the main part is held by its own spring action. Housing 10 has a funnel-shaped opening 13 corresponding to the entering hole 3 in cross member 6, for the purpose of convenient insertion of a conductor 2. In this connection it can be an advantage that the free or flexible end of spring element 9 and the end of backing element 8 are so arranged in relation to each other that there is a small overlap between them, as will be seen from Fig. 1. When the free end of spring element 9 in this manner extends over the end of backing element 8 and at the inside thereof, it will be additionally safe guarded that a conductor 2 during insertion can without problems enter into the converging space between the inside of backing element 0 and

contact areas

7, 7A. Besides this will prevent over-loading of spring element 9.

Fig. 2 shows a contact pin 15 being introduced into the contact device, whereby such a contact pin normally is incorporated in the equipment or installation unit on which the contact device is intended to be mounted. For this purpose the housing 10 is provided with an opening 17 for entering contact pin 15, such opening 17 leading into a split in the U-leg 5 so that the contact pin is guided between this leg and the back part 9A of the spring element. Thereby contact pin 15 will be clamped by spring action and a secure electrical contact is obtained with U-leg 5. The above mentioned profiling of leg 5, in this connection can serve for lateral guiding of contact pin 15.

As an alternative to the above described embodiment of the backing element 8 as a bent-back continuation of

contact areas

7, 7A, there is indicated in Fig. 1 with dashed lines, that backing element 8 can be associated with U-leg 5 in a manner corresponding more or less to the embodiment first explained and shown with full lines in Fig. 1. Thus, in the alternative embodiment there will be an extension or supporting member 5A maintaining backing element 8 fixed in the correct position, but supported by leg 5 instead of being supported by the opposite U-leg with

contact areas

7, 7A.

A further alternative for providing a backing element or portion having a quite similar effect as the backing element 8 described, could be to form a suitably large, conical bore in a more or less transverse plate piece opposite to cross member 6, i.e. beyond one or both ends of the U-legs and preferably carried by one of these. The conicity of such a stamped or drawn bore in the plate piece, in such case would in principle correspond to the converging space for the inner end 2A of conductor 2, that in Fig. 1 is present between the inside of backing element 8 and

contact areas

7, 7A.

Claims

Screwless electrical contact device for connecting one or more bare conductors thereto, comprising a main part (4) consisting of an electrically well conductive metal, formed from sheet material and having contact areas (7,7A) for cooperation with an inserted conductor (2), and a spring element (9,9A) adapted to press an inserted conductor (2) against the contact areas (7,7A) and formed with an edge or the like for blocking against inadvertent retraction of the conductor (2),
characterized by a backing element (8) located opposed to at least an inner portion (7) of the contact areas (7,7A) and converging towards said inner portion (7) at such spacing and such direction that the end (2A) of an inserted conductor (2) is urged into engagement with the contact areas (7,7A).
Contact device according to claim 1,
characterized in that the backing element (8) is formed as a bent-back continuation of the sheet material from the contact areas (7,7A).
Contact device according to claim 1,
characterized in that the main part (4) as seen in cross section coinciding with the longitudinal direction of an inserted conductor (2), has an approximate U-shape with the contact areas (7,7A) formed in one leg of the U-shape, and another or opposite leg (5) of the main part (4) provides support for a back part (9A) of the spring element (9,9A) and that the backing element (8) is formed at an extended portion (5A) of the other U-leg (5).
Contact device according to claim 1,
characterized in that the backing element is formed by a stamped or drawn bore which is tapering conically in the direction of insertion of a conductor, from a relatively large opening making possible the entering of a conductor, to a relatively narrow inner end, the diameter of which is smaller than the smallest transverse dimension of the conductors concerned.
Contact device according to any one of claims 1-4,
characterized in that the spring element (9,9A) with its edge or end portion is adapted upon its bending, to lie on the inside of and somewhat overlap the backing element (8).
Contact device according to any one of claims 1-5,
characterized in that it has an opening (17) for introducing a contact pin (15) so as to clamp the pin between the other U-leg (5) and the back part (9A) of the spring element.