GB2247791A

GB2247791A - Connecting terminal

Info

Publication number: GB2247791A
Application number: GB9117139A
Authority: GB
Inventors: Gerhard Moessner
Original assignee: ABB Patent GmbH
Current assignee: ABB Patent GmbH
Priority date: 1990-08-17
Filing date: 1991-08-08
Publication date: 1992-03-11
Also published as: DE4026037A1; GB9117139D0; DE4026037C2

Abstract

A screw terminal with a terminal frame (10) and a clamping frame (20), the lower transverse webs (12, 22) of which can be clamped against each other by means of a clamping screw (17) so that a lead (28) can be clamped firmly between them, is provided with cutting edges (26, 27) on the mutually opposite faces of the lower transverse webs for clamping aluminium leads. The cutting edges are formed in such a way that they can pierce the aluminium oxide formed on the surface of the aluminium lead. <IMAGE>

Description

1 "Connecting terminal" The invention relates to screw connecting

terminals.

A screw connecting terminal disclosed for example in German Patent Specification 31 37 177 has a square clamping frame of clos ed form through which passes a terminal frame constructed in the form of a slider or runner. The clamping screw passes through an opening in the terminal frame and is screwed into the clamping frame; the screw head is situated outside the terminal frame. When the clamping screw is tightened the clamping frame is pulled towards the outer face of the side of the terminal frame passing through the clamping frame, so that a lead inserted between the clamping frame and the terminal frame is firmly clamped.

The faces of the mutually adjacent webs of the clamping frame and the terminal frame, between which a copper wire for example can be inserted and clamped therein, have roughened areas in the known designs in order to prevent the connecting lead from being easily withdrawn from the clamping point.

2 However, leads produced from aluminium cannot be simply connected to the known terminals since an excessively high transition resistance is produced by the oxide layer which forms on any surface of an aluminium component exposed to the air. Consequently, in the case of aluminium leads the aluminium oxide layer must be removed for example in accordance with the GDR-Standard TGL 21590/01 and the bare metal ends of the lead must be greased with a neutral grease.

Similar connecting terminals can also have a terminal frame and a Ushaped clamping frame part, or a clamping frame and a U-shaped terminal frame part, or a terminal frame part and a clamping frame part which are each U-shaped; here too the same problem exists as in the case of a connecting terminal according to DE-PS 31 37 177.

The object of the invention is to provide a screw connecting terminal of the type described in the introduction, to which aluminium connecting leads can also be connected without preliminary treatment.

t 1 3 The invention resides in an electrical screw connecting terminal comprising a first member comprising two transverse arms integrally formed on respective ends of at least one longitudinal web and extending transversely thereto, a first said transverse arm of the first member being provided with a bore for passage of a clamping screw, and further comprising a second member comprising two transverse arms integrally formed on respective ends of at least one longitudinal web of the second member and extending transversely thereto, a first said transverse arm of the second member being provided with a threaded bore and being inserted between the transverse arms of the first member and the clamping screw passing through the through bore in the first transverse arm of the first member and being screwed into the said threaded bore for moving the second transverse arm of the first member and the second transverse arm of the second member towards one another, and at least one cutting edge being integrally formed on the mutually opposed faces of the second transverse arms, the cutting edges extending transversely to the length of a lead to be clamped between the said two faces.

4 The mutually facing faces of the transverse arms of the first and second members are provided with at least one pointed protrusion, which can pierce the aluminium oxide layer of the aluminium lead so that the terminal is given an adequate current-carrying capacity. A single projection can be provided on the outer face of the second transverse arm of the first member and two projections, arranged at a distance from each other, can be provided on the opposite inner face of the second transverse arm of the second second member, or vice versa, one projection being provided on one member between the projections on the other member.

The said arms may be arms of Ushaped members or webs of members of closed profile.

Claims

Further advantageous features of the invention are set out in the Sub- Claims. Although only a connecting terminal with a closed terminal frame and clamping frame is. referred to below in the oxplanation of the invention, this should not be regarded as a restriction. The invention can also be applied even if the terminal frame and/or the clamping frame are constructed in a U-shape, each having only one longitudinal web and two transverse webs integrally formed thereon and extending at right angles thereto. k_ A The invention and further advantageous developments and improvements of the. invention are explained and described in greater detail with reference to the accompanying drawing, in which two embodiments of the invention are illustrated and in which Fig. 1 is a perspective sectional view of a first embodiment of a terminal according to the invention; Fig. 2 is a sectional view of the terminal according to Fig. 1, with a lead inserted; Fig. 3 is a partial sectional view in perspective of a further embodiment of the invention, and Fig. 4 is a sectional view through part of the screw terminal according to Fig. 3 with a lead inserted. A screw connecting terminal shown in Fig. 1 comprises a terminal frame 10 which has a rectangular shape, the shorter transverse webs of which are joined to each other by way of longitudinal webs 13 and 14. The shorter web at the top of the drawing in Fig. 1, also referred to as the upper first transverse web 11, has a through hole 14, through which is inserted the shank 16 6 of a screw 17, the head 18 of which is situated outside the upper transverse web. An extension 19, to which can be connected connecting elements of the switching appliance or other device in which the screw terminal according to Fig. 1 is used, is integrally formed on the upper transverse web 11 at right angles thereto or at right angles to the plane set defined the terminal frame 10. The lower transverse web 12 has a clamping frame 20 passing through it, which is constructed in the form of a slider and which comprises an upper first transverse web 21, a lower second transverse web 22 and two longitudinal webs 23 joining them together (the other longitudinal web is not visible as it has been cut away), the lower transverse web 22 being bent into a semicircle so that the two longitudinal webs 23and the lower transverse web 22 together form a U-shape. As may be seen from Fig. 1, the lower transverse web 12 is provided on both lateral edges with projections 24 (the-nearer projection is not visible) which engage in rectangular openings 25 in the longitudinal webs 13, 14 of the terminal frame 10 and thus serve to guide the clamping frame 20 with respect to the terminal frame 10. n- 7 A transverse cutting edge 26 is provided on the underside of the web 12 as shown in Figs. 1 and 2 in the region of the projections 24, the said cutting edge 26 having a counterpart 27 on the opposite inner face of the web 22. The two cutting edges 26 and 27 have been pressed out of the webs 12 and 22 respectively by deformation and each forms a V-shape in cross section. As may be seen from Fig. 2, in use the cutting edges 26 and 27 are pressed into a lead 28 clamped between them, with the result that if the said lead consists of aluminium the aluminium oxide surface layer is pierced, so that a good electrical contact is formed between the aluminium lead 28 and both webs 12 and 22. In order to clamp the lead 28 the screw 17 is turned, in such a way that the clamping frame 20 is pulled upwards in the direction of the arrow P by the thread on the screw shank 16. Instead of one cutting edge 27, it is also possible to provide two cutting edges 29 and 30, as shown in Figs. and 4, which are formed in the same way as the cutting edge 27, in the web 22. The cutting edge 26, which is present in the web 12, is situated approximately in the middle between the two cutting edges 29 and 30, so that in contrast to the embodiment according to Fig. 2, in 3 8 which the.lead is clamped only by two cutting edges or between two cutting edges, three clamping points are provided at which the oxide layer is pierced. It should be added that the cutting edges 26, 27; 29 and 30 are produced by deformation of the web 12 and the web 22 respectively; depressions 31, 32; 33, 34 corresponding to the shape of the cutting edges are formed on the other faces of the webs opposite the cutting edges. The cutting edges are arranged parallel to one another; in the case of the terminal frame they extend parallel to the corner edges of the terminal frame, and in the case of the clamping frame 20 they extend parallel to the lateral edges of the clamping frame. In each case they extend transversely to the lead 28. Figs. 1 to 4 show that the cutting edges extend at right angles to the lead 28; it is also possible of course for the cutting edges to be arranged in a slanted manner, i.e. obliquely to the lead 28. The arrangement according to the invention can also of course be used even if the terminal frame and/or the 11 C 11 9 clamping frame themselves are not constructed in the form of closed sliders, but are U-shaped. If the terminal frame is U-shaped, i.e. has one longitudinal web omitted for example, the cutting edge 26 is provided on the outside of the lower arm. The same also applies if the clamping frame is U-shaped. 11 Cl ai ms: 1. An electrical screw connecting terminal comprising a first member comprising two transverse arms integrally formed on respective ends of at least one longitudinal web and extending transversely thereto, a first said transverse arm of the first member being provided with a bore for passage of a clamping screw, and further comprising a second member comprising two transverse arms integrally formed on respective ends of at least one longitudinal web of the second member and extending transversely thereto, a first said transverse arm of the second member being provided with a threaded bore and being inserted between the transverse arms of the first member and the clamping-screw passing through the through bore in the first transverse arm of the first member and being screwed into the said threaded bore-for moving the second transverse arm of the first member and the second transverse arm of the second member towards one another, and at least one cutting edge being integrally formed on the mutually opposed faces of the second transverse arms, the cutting edges extending transversely to the length of a lead to be clamped between the said two faces.

1 1 I-

2. A connecting terminal according to Claim 1, characterized in that the said face of the second transverse arm of the second member comprises two cutting edges which extend parallel to each other and transversely to the longitudinal direction of the clamped lead.

3. A terminal substantially as herein described with reference to Figs. 1 and 2 or Figs. 3 and 4 of the accompanying drawings.

Published 1992 at The Patent Office. Concept House, Cardiff Road. Newport. Gwent NP9 IRH. Further copies may be obtained from Sales Branch. Unit 6, Nine Mile Point. Cwmfelinfach, Cross Keys, Newport, NP1 7HZ. Printed by Multiplex techniques ltd. St Mary Cray, Kent.