GB2069775A

GB2069775A - Electrical screw terminal

Info

Publication number: GB2069775A
Application number: GB8104644A
Authority: GB
Original assignee: Lumberg Automation Components GmbH and Co KG
Current assignee: Lumberg Automation Components GmbH and Co KG
Priority date: 1980-02-15
Filing date: 1981-02-13
Publication date: 1981-08-26
Also published as: IT1135407B; IT8119649A0; GB2069775B; DE3005619C2; DE3005619A1

Abstract

An electrical screw terminal for connecting single wires to the conductor tracks of a printed circuit board comprises clamping elements (12), each of which supports a clamping screw (15) and has a soldering tag (14) extending therefrom, the soldering tag (14) and clamping element (13) being formed from a single piece of material bent into a substantially rectangular shape, the soldering tag being stamped therefrom as a tongue which is bent out of the plane of the clamping element. <IMAGE>

Description

SPECIFICATION Electrical screw terminal for connecting single wires to the conductor tracks of a printed circuit board This invention relates to an electrical screw termi nai with clamping elements for connecting single wires to the conductor tracks of a printed circuit board, the clamping elements being accommodated in a housing of insulating material and each adjustably supporting a clamping screw and being equipped with a soldering tag emerging from the housing and adapted for fastening to the circuit board.

The soldering tag of each clamping element, which must make an electrically conductive connection with the bared end of a wire, serves, with its section emerging from the housing, for the electrically conductive and, if appropriate, mechanically fixing connection of the clamping element in question or of the entire screw terminal to the circuit board. Several designs of electrical screw terminals of the aforementioned type are known. There are embodiments in which a loose soldering tag is anchored in the housing of insulating material and penetrates with a contact section into the clamping element which is drawn, with the plugged-in end of the single wire, against the contact section of the soldering tag. This design necessitates specially designed retaining grooves or the like, on the housing of insulating material for the loose soldering tag.

Also, the contact section of the soldering tag which projects into the space of the clamping element can be damaged due to careless manipulation. In another embodiment, the soldering tag is welded to the clamping element but although a bond between the soldering tag and clamping element is thereby obtained, nevertheless this method of producing and fastening the soldering tag to the clamping element is very expensive. Furthermore, the weldpoints sometimes reduce the electrical conductivity of the connection or are inadequately executed, so that electrical faults can occur.

It is an object of the invention to provide a simplified and improved electrical screw terminal.

According to the invention, there is provided an electrical screw terminal with clamping elements for connecting single wires to the conductor tracks of a printed circuit board, the clamping elements being accommodated in a housing of insulation material, each adjustably supporting a clamping screw and being equipped with a soldering tag which emerges from the housing and is adapted for fastening to the circuit board, the soldering tag being integral with the clamping element, and formed from a single sheet-metal strip which, in the plug-in direction of the single wire, is folded into a substantially rectangu lar frame element from which the soldering tag is stamped as a tongue and is bent out of the plane of said strip.

Although it is known, in principle, to make the soldering tag in one-piece with and materially integral with the clamping element, nevertheless, in so doing, the clamping element, together with the soldering tag, has to be turned from the solid on a lathe, that is to say, the soldering tag in the form of a small thin leg has to be produced by machining. The screw terminal according to the invention differs from this very expensive manufacturing and material wasting method of obtaining a clamping element with soldering tag, in that its clamping elements are formed by bending a sheet-metal strip in a simple way, the soldering tag being obtained by stamping and bending it out of the material of the sheet-metal strip which is used for the clamping element. With the present invention therefore, an integral constituent part of the clamping element itself is used as the soldering tag.Thus, no additional material is required for the soldering tag, that is to say, the waste portions arising during the manufacture of the terminal with its soldering tag do not occur. A further, very considerable advantage is that there is relative freedom, in terms of the geometry of the sheet-metal strip forming the clamping element, in how the stamping out of the tongue serving as soldering tag is to be arranged, so that the position and the length of the soldering tag can be selected according to the position and length of the stamped-out tongue. Depending on the arrangement and design of the stamping out and depending on the bending-out of the tongue, a clamping element can be obtained, the soldering tag of which is either aligned with the clamping screw or runs at an angle thereto, for example a right angle.Thus, screw terminals can be obtained in a simple way, in which the plug-in direction of the single wire can be provided either in a plane parallel to the plane of the printed circuit board or in a direction transverse thereto, for example perpendicular. Because the soldering tag is constituted by a tongue which is bent out of the sheet-metal strip, no obstructing and therefore disturbing projections caused by the soldering tag occur within the inner space of the clamping element which serves to receive the single wire.

The inner space of the clamping element can therefore be used to the full.

In one embodiment of the present invention, the soldering tag is located approximately along the longitudinal centre axis of the sheet-metai strip so that the supporting sections of the clamping element remain on both sides of the stamped-out soldering tag.

The soldering tag can be located approximately coaxially to the clamping screw, so that the direction of movement of the clamping screw coincides with the plug-in direction of the soldering tag into the printed circuit board. As a result, very favourable force conditions arise, which, even in the case of repeated actuation of the clamping screws and loading of the screw terminals, do not lead to a disadvantageous loading or damaging of the sensitive connecting tags and of their connection to the circuit board.

In another embodiment, the sheet metal strip clamping element consists of a base section, of two The drawing(s) originally filed were informal and the print here reproduced is taken from a laterfiledformal copy.

side sections and of two overlapping end sections, at least one of which contains 3 thread to receive the clamping screw, the tongue being, shaped out of at least that part of the sheet-metal strip which corres ponds to a side section of the clamping element. To obtain an arrangement in which the soldering tag is located approximately coaxially to the clamping screw, it is advantageous to stamp the soldering tag out of that part of the sheet-metal strip which consti tutes the base section and one side section of the clamping element. In addition, if appropriate, that part of the sheet-metal strip which constitutes that outer end section of the clamping element which adjoins the side section can also be included at least partly.In this case, a relatively long soldering tag can be obtained in a very simple way, which can be especially advantageous if it is intended to fasten the screw terminal to the printed circuit board at a distance from the latter.

In another preferred embodiment, a threaded section is extended, in a neck-like manner, into the inner one of the overlapping end sections of the sheet metal strip for the clamping element, said threaded section projecting into the over-lapping region of the outer section and serving as a bearing peg for a strip-shaped wire protector which is clamped between the sections and the free end section of which is bent back into the space of the clamping element to run underneath the screw shank. A screw terminal designed in this way is characterised by its espe cially convenient and reliable arrangement of the wire protector.This can be inserted between the end sections during the operation of wrapping-around the sheet-metal strip to form the clamping element, said wire protector being fixed firmly to the clamp ing element by the threaded section which is extended in a neck-like manner. The free section of the wire protector points appropriately in the plug-in direction of the single wire, as a result of which free dom from faults is guaranteed in the case of repe ated wire connections.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure lisa side view of an electrical screw termi nal with four clamping elements, Figure 2 is a longitudinal section taken along the sectional line ll-ll in Figure 1, Figure 3 is a section along the sectional line lil-lil in Figure 2, but only through the clamping element, Figure 4 is a section along the sectional line IV-IV in Figure 3, Figure 5 is a view of the clamping element shown in Figure 4, and Figure 6 is a plan view of the clamping element of Figure 5.

The drawings show an electrical screw terminal comprising a substantially block-shaped housing 10 of insulating material which has, in the illustrated embodiment, four chambers 11 for receiving clamp ing elements 12, each chamber housing on one side an insertion opening 13 for introducing the clamping element 12.

For the electrically conductive and mechanically fixing connection of the screw terminal to a printed circuit board (not shown), each clamping element 12 possesses a soldering tag 14 which is stamped out of, the sheet-metal strip used to form each wrapped- around clamping element 12 and which is deformed out of the plane of said strip. In the illustrated embodiment, each soldering tag 14 projects from the base and emerges, as a coaxial extension of clamping screw 15, from the housing 10 through an opening 16 in base 17 thereof. Opening 16 widens, in the direction of opening 13, into a slot 18forintroducing the soldering tag.

As already mentioned, each clamping element 12 is folded out of a sheet-metal strip to form an approximately rectangular contour and possesses several sections 19-23. Of these sections, sections 19 and 23 provide end sections for the sheet-metal strip which overlap one another, the sections 20 and 22 constituting side sections and the section 21 providing the base section of the clamping element 12. An outwardly directed threaded socket 24 is extended, in neck-like manner, approximately in the centre of the inner end section 23 which is overlapped by the outer end section 19 from the opposite direction.

Internal thread 32 of said threaded socket interacts with an external thread 33 of the clamping screw 15.

So that the outer end section 19 can rest tightly on the inner end section 23, the former has, in the region where it overlaps the threaded socket 24, a recess 25 which, continues on into the side section 20 (see Figure 5). Moreover, the threaded socket 24 also serves to support a wire protector 26 which is formed from a strip of sheet spring material and which has a flat rectangular cross-sectional contour.

The wire protector 26 engages round the outer periphery of the threaded socket 24 and is gripped between the end sections 19 and 23, the side sections 20 and 22 preventing the wire protector 26 from turning. Remote from bent zone 27 which is provided just outside the clamping element 12, the wire protector 26 has an end section 30 (see Figure 4) which is bent back into the inner space 28 in the plug-in direction R of a single wire 29 (see Figure 2).

The end section 30 is approximately as long as the inner space 28 of the clamping element 12. In the embodiment illustrated in Figure 2, the end section 30 is curved convexly towards the screw shank 1 spa.

As a result, in conjunction with the bending zone 27, a constant pressing force is exerted against the screw shank, so that, when the clamping screw 15 is slackened, the end section 30, following the withdrawing movement of the clamping screw 15, opens up the plug-in space again for the single wire 29. In any case, the end section 30 of the wire protector 26, which serves as the actual protector, is located between the clamping screw 15 and the base section 21 of the clamping element 12.

In the illustrated embodiment, the soldering tag 14 is cut out, by means of a cut into the sheet-metal strip for the clamping element 12, over approximately half the width of the base section 21 and a considerable part of the second section 20 and is bent over so that the attaching zone 31 is aligned approximately axially with the clamping screw 15.

The soldering tag 14 is also coaxial with respect to the clamping screw 15.

To obtain a longer soldering tag 14than that illustrated, with an otherwise identical arrangement, the cut into the sheet-metal strip could also be continued into the outer end section 19, which it is safe to do, because the outer end section 19 must, all the same, possess the recess 25 for the passage of the threaded socket 24.

In the embodiment illustrated primarily, the single wire 29 would normally be introduced into the terminal parallel to the base 17 thereof, that is to say, parallel to the plane of the printed circuit board. An angular arrangement, e.g. at right angles, is also possible, two example of which are shown in Figure 3. In one of these emhodiments, the sheet-metal strip forthewrapped-around clamping element 12 is stamped out in the region of the side section 20 only, so that a soldering tag 14' can be obtained, which is aligned as an extension ofthe base section 21 ofthe clamping element 12. This soldering tag 14' would then project at right angles to the axis of the clamping screw 15. A second, rectangular arrangement is illustrated by dot-and-dash lines in Figure 3, in which a soldering tag 14" is obtained by means of a cut over a part of the side section 20 and over the entire base section 21, at the end of which the soldering tag 14" is bent out of the clamping element. The projecting length of this soldering tag 14" beyond the remainder of the clamping element is greater than that of the soldering tag 14' by approximately the width of the base section 21. A soldering tag 14" which is prolonged in this way can be advantageous, depending on the design of the housing 10 of insulating material, or can provide the possibility of enabling a screw terminal to be fitted on a printed circuit board at a distance from the latter.

Claims

1. An electrical screw terminal with clamping elements for connecting single wires to the conductor tracks of a printed circuit board, the clamping elements being accommodated in a housing of insulation material, each adjustably supporting a clamping screw and being equipped with a soldering tag which emerges from the housing and is adapted for fastening to the circuit board, the soldering tag being integral with the clamping element, and formed from a single sheet-metal strip which, in the plug-in direction of the single wire, is folded into a substantially rectangular frame element from which the soldering tag is stamped as a tongue and is bent out of the plane of said strip.

2. A screw terminal according to claim 1, wherein the soldering tag is located approximately along the longitudinal centre axis of the sheet-metal strip.

3. A screw terminal according to claim 1 or claim 2, wherein the soldering tag is substantially coaxial with the clamping screw.

4. A screw terminal according to any of claims 1 to 3, wherein the sheet-metal strip clamping element consists of a base section, two side sections and two overlapping end sections, at least one of which contains a thread to receive the clamping screw, the soldering tag being cut out of at least that part of the sheet-metal strip which corresponds to a side section of the clamping element.

5. A screw terminal according to any of claims 1 to 3 wherein the sheet-metal strip clamping element comprises a base section, two side sections and two end sections, the soldering tag being stamped out of that part of the sheet-metal strip which constitutes the base section and a side section and, if appropriate, also that outer end section of the clamping element which adjoins said side section.

6. A screw terminal according to claim 4, wherein a threaded section is provided in the inner one of said overlapping end sections of the sheet-metal strip for the clamping element, said threaded section projecting in a neck-like manner into the overlapping region of the outer end section and serving as a bearing peg for a strip-shaped wire protector which is clamped between the end sections, the free end section of said protector being bent back into the clamping element to run underneath the screw shank.

7. A screw terminal according to claim 6, wherein the free end section of the wire protector points in the plug-in direction of the single wire.

8. A screw terminal with clamping elements substantially as herein described with reference to the accompanying drawings.