GB2073963A

GB2073963A - Holder for electrical element

Info

Publication number: GB2073963A
Application number: GB8109821A
Authority: GB
Original assignee: Wickmann Werke AG
Current assignee: Wickmann Werke AG
Priority date: 1980-04-16
Filing date: 1981-03-30
Publication date: 1981-10-21
Also published as: FR2481052A1; DE8010402U1; GB2073963B; JPS56153644A

Abstract

A holder for an electrical element (2) having contact end faces (3), in particular for an electrical safety element which is to be fitted to a printed circuit board, the holder comprising a base plate (4) having two slots (4%) into which spring contacts (5) are press fitted. Upper parts of the spring contacts are provided on their inner faces, which clamp the element between them, with projections (6,9) for locating the element (2). Lower ends (10) of the spring contacts project from the bottom of the base plate for connection to other connectors, e.g. on a printed circuit board. <IMAGE>

Description

SPECIFICATION Holder for electrical element The invention relates to a holder for an electrical element, having contact faces at its ends, in particulay for an element such as a surge suppressor or other safety element which is to be fitted to a printed circuit board, the holder having two spaced similar spring contacts which are fitted on a mounting made of electrically insulating material and between which the element can be resiliently clamped with its end faces in engagement with the spring contacts, the spring contacts having end extensions for connecting to other electrical connectors. Such a holder is hereinafter referred to as of the kind described.

In the case of a known holder of this (West German Utility Model 78 618)the spring contacts are arranged inside a mounting consisting of a chamber formed by two webs arranged at a distance apart with a base connecting the webs, so that the chamber exhibits an upwardly open U-shaped appearance. The base of the chambers of which a number may be arranged in a row one behind the other, have apertures for the reception of clamping contacts which can be snapped in and which project beyond the underside of the base in the usual way for the production of electrical connections such as soldered connections to printed circuit boards. At their upper part the spring contacts have stamped out tongues which are bent and project inwards and which are intended for engagement with electrical safety devices, such as surge suppressers, having indented end faces.The method construction of the chamber makes the mounting and the accessibility and the handling of the spring contacts difficult, and use in restricted to elements which have indented end faces.

Mountings for surge suppressers are already known (West German Utility Model 68 04 494) in which a fixed angular contact and an opposed spring contact engage the end faces of an element and are provided with limiting stops consisting of tongues bent over inwards at the edge of the spring contacts.

Nevertheless this mounting is not suitable for insertion as a holder for printed circuit boards and the two contacts, which are stamped and bent more than once, are differently shaped which demands a correspondingly elaborate manufacture and assembly. Screw fastenings are also in this case unavoidable and the space required by the mounting is considerable.

In order to be able to fit electrical elements of different sizes in the same mounting an adaptor is known for gas discharge arresters (West German Utility Model 19 08 660). This enables the insertion of smaller arresters in larger mountings during the course of modernisation of devices. The adaptor consists of a box shaped casing of two framelike side parts of equal shape, onto which may be slid in a dovetail engagement, contact components which are bent up out of sheet metal into boxlike frames of equal shape and are stamped out in the central portion and have spring tongues projecting inwards.

In spite of the equality of shape of the spring contacts formed in particular by the spring tongues, this known adaptor forms a comparatively costly solution for the achievement of adaptability of mounting elements of different shape and size.

Finally another mounting for surge suppressers is known (West German Patent No. 22 61 513) which, for the reception of the surge suppressers having contacts at their end faces, has two contact springs of equal shape in a boxlike casing open at the respective end faces. The faces of the contact springs, which are not intended for engagement with the surge supresser, rest against the casing of insulating material and out of the centre of the spring contacts there project tongues which are stamped out and bent down. In the same way as in the case of the known mounting first mentioned above, these tongues are intended for engagement with indented end faces of the surge suppressor.The snapping into the inside of a boxlike casing and the contact formation necessary for doing this causes a relatively complicated contact shape and for the electrically conductive engagement with the surge suppresser only a comparatively small section of the contacts is available. Furthermore the casing takes up a lot of room.

As compared with this state of the art the problem exists of creating a holder of the kind described which (a) is suitable for universal use, that is, for the reception of elements provided with contact faces at the ends, of different shapes and sizes within a certain range of sizes and shapes; (b) is easily accessible even in the case of a compact arrangement of different components and requires little space, particularly upon exchange of the holder and/or of the element; and, (c) can be produced from as few components as possible, which are simple to manufacture and also to mount and are individually and as a whole of the smallest possible structural size.

In accordance with the invention, in a holder of the kind described, the mounting consists of a base plate having two slots into respective ones of which the spring contacts are inserted as far as the engagement of a stop on each spring contact against a first surface of the base whereupon the end extentions project from the opposite surface of the base; the element-engaging parts of the spring contacts converging towards one another in a direction away from the first surface of the base prior to introduction of an element, and being provided on their inner faces with a number of projections which are arranged to embrace the element and to locate it in a predetermined position.

A holder of this construction may overcome the above problem in a simple manoeuvre. The spring contacts of like shape, which may be stamped out of sheet metal of appropriate springy characteristics in one working steps, exhibit on their inner faces a number of projections, in the simplest case two, which are arranged to locate an element introduced between the contact springs. The projections may be formed by point-shaped impressions from the outer faces, or by stamping out, and in any case are arranged and distributed in such a way that they correspond with the outline shape of the contacts on the electrical element to be held. Consequently, the contact faces of the element may be frusto-conical, the shape of a hollow cylinder, square etc. The projections embrace the element and hold it firmly.

The spring contacts are held in the base, and before the introduction of the element are inclined towards one another in oblique positions. Upon introduction of the element, they are spread to accommodate the element so that automatically a spring clamping force is developed which is adequate for the electrically conductive connection to the contact faces of the element. This is desirable for the avoidance of slipping of the element out of the correct position which is defined by the projections.

An important advantage of the new holder is its compactness. The employment of leaf spring contacts enables the length of the holder to be only slightly greater than the length of the electrical element. In any case no projections of any kind or the like need to exist on the outside of the spring contacts. The length of the base does not need to exceed that of the whole arrangement of the spring contacts and the electrical element if each spring contact has a stop in the form of a jog. This jog enables the formation of the two slots necessary for the mounting of the spring contacts in the base, at a distance inwardly from the edge of the base, and through the jog running outwards from the respective slot the full length of the base is again available for the distance between the spring contacts.With the same size of base and the same distance between the two slots, a variation in the offset of the jog varies the separation of the element-engaging parts of the spring contacts so that elements of different size can be held. In extreme cases the jog may be so wide that it reaches out beyond the edge of the base and thereby the maximum distance between the contact springs is greater than the length of the base.

The same degree of adaptability exists for the kind and arrangement of the projections, since for these the whole area of the spring contacts is available if the latter are made, as is preferred, as continuous leaf spring contacts.

It follows that the holder in accordance with the invention consists of only two different parts, that is, the base of insulating material and a pair of spring contacts of like shape. Both components may be of a simple shape which is consequently correspondingly simple to manufacture. Assembly likewise is easy as the spring contacts may be inserted by their end extensions into and through the two slots in the base. The relative dimensions of the spring contacts and slots may be such that the spring contacts are anchored by being a force fit in the slots in the base.

Adequate fastening of the spring contacts into the base is thus achievable without further measures having to be adopted.

The size of the area of the spring contacts does not need to exceed significantly the outline of the end face of the element which is to be held. This results in an extraordinarily small structural width and structural height so that in combination with the above mentioned small structural length, optimum compactness of the holder is achieved.

The position and construction of the spring contacts allows exact and at the same time secure location of the element. Upon insertion and removal of the element only a small spring movement is necessary, since the projections for locating the element need project only slightly inwards from the faces of the spring contacts.

This new three-dimensional shape of base and contact springs can easily be produced automatically by the means available today.

When the holder is intended for elements such as surge suppressers or other electrical safety elements which are to be arranged on printed circuit boards, the base may be kept relatively thin-walled, because in this case the spring contacts may be arranged to be soldered at their end extensions into a printed circuit board. This provides additional fastening of the ends of the spring contacts, after they have been plugged into a printed circuit board. This is sufficient as the spring contacts usually only become loaded by an element after the insertion of the holder in the printed circuit board. The base then acts essentially only as an aid to assembly and the fastening of the spring contacts to the printed circuit board.

The holder may be modified for further applications.

Thus, for making tangential contact with an annular central electrode of, e.g. a three-electrode suppresser, a forklike contact part pointing away from the first surface of the base, may be arranged between the two spring contacts and is similarly supported in an additional slot in the base so that in use the fork prongs contact the central electrode; and an end extension of the contact part projects in the form of at least one plug pin from the opposite surface of the base.

Furthermore for receiving two elements and making contact against their end faces, a piece of sheet metal may be inserted between the two spring contacts and similarly supported in a slot in the base.

If necessary the piece of sheet metal may have an end extension projecting in the form of at least one plug pin from the opposite surface of the base. It is possible to leave the inserted piece of sheet metal dead flat in the actual contact region, the required definite position of the electrical element being brought about by the associated spring contact provided with corresponding projections. But is equally possible to provide the piece of sheet metal on one face or even on both faces with projections similar to those provided on the spring contacts. In the case of projections arranged on both faces these will be appropriately offset with respect to one another.

Some examples of holders constructed in accordance with the invention are illustrated in the accompanying drawings, in which: Figure 7 is a side elevation of a holder soldered onto a printed circuit board, and having wart-shaped projections facing one another close to the upper ends of the contact springs and inwardly directed stops arranged beneath them; Figure 2 is a side elevation of the holder of Figure 1 illustrating the maximum spring travel during the insertion or removal of an electrical element; Figure 3 is a side elevation of the holder of Figure 1 with an electrical element received in the fully assembled position; Figure 4 is a front elevation of the holder as in Figure 3 as seen in the direction of the arrow in Figure 3;; Figures 5a and 5b are a front elevation and a cross section respectively of a small projecton arranged at the top on the inside of the contact springs, in the form of an embossed wart; Figures 6a and 6b are a front elevation and a cross section respectively of a small projection applied at the top on the inside of the contact springs, in the shape of an embossed strip; Figures 7a and 7b are a front elevation and a cross section respectively of a small projection attha top of the inside of the spring contacts, in the form of a tongue which has been stamped out and forced obliquely inwards; Figures 8, 9 and 10 are elevations of a holder similar to that of Figure 1, but for alternative forms of connection.

A holder designated in general by 1 has a base 4 made of electrically insulating material and provided with two slots 4' arranged at a distance apart.

Through the slots 4' extend a pair of generally rectangular-shaped leaf spring contacts 5 which each exhibits a jog 5' at an upper surface 4" of the base 4 and, on its inner faces, projections in the form of warts 6 projecting slightly out of the face and tongues 9 stamped partially out of the face and bent inwards. This arrangement may be seen from Figure 4 where the outline of an electrical component 2 is indicated in dash-dot lines.

At their upper ends the spring contacts 5 are bevelled outwards for facilitating the introduction of an element 2. Upon the introduction of an element 2, as is illustrated in Figure 2 in the form of an arrester (surge suppresser) provided with contact faces 3 at the ends, the contact springs 5 get spread resiliently apart until the element 2 has reached a position against the inwardly projecting tongues 9 as may be seen on Figure 3, in which it is embraced in the upper region by the warts 9. In this way under the clamping spring action of the spring contacts 5 and in combination with the projections 6 and 9 an exactly predetermined position of the element 2 between the spring contacts 5 is obtained and maintained under operating conditions.

Figures 5a and 5, 6a and 6b, and 7a illustrate that the projections serving for the location of the element in parallel with the spring contacts 5 may be made in very different ways. What is essential is that the upper projections allow easy insertion and removal of the element 2 and nevertheless make possible a holding action after the insertion of the element 2 against unintentional slipping out in the direction away from the base 4.

The width of the jog 5' together with a predetermined distance between the slots 4' (Figure 1) determined the distance between the spring contacts 5 in the region where the element 2 is held. To that extent the contacts 5 may be adapted to different lengths of the element 2.

Furthermore the jog 5' restricts the movement of the contacts 5 upon insertion and subsequent forcing of the contacts 5 into the slots 4' in the base 4. In order to achieve a secure clamping action of the spring contacts 5, which can preferably be forced into the slots 4' across the whole width of the contact (indicated in dotted line in Figure 4), the parts of the spring contacts 5 which are to be brought into engagement with the slots 4' exhibit, in their width and along their length, dimensions only slightly more than the width of the corresponding slots.

Upon mounting the spring contacts 5 on the base 4 the spring contacts 5 are first of all inserted by their bottom ends 10, which may be made as plugs for printed circuit boards L, from above into the slots 4', whereafter the forcing-in of the spring contacts 5 is effected as far as contact of the respective jog 5' against the surface 4" of the base 4.

Figures 8, 9 and 10 make it clear that the holder may be provided with various kinds of connection, the bottom ends 10 may, as shown in Figures 9 and 10, be bent to the side for the production of an electrically conductive connection to corresponding connectors. But preferably the bottom ends 10 of each spring contact 5 are forked as may be seen, for example from Figures 3 and 4, for plugging into printed circuit boards L in which, as illustrated in Figure 1, they are soldered. By the soldering-in the spring contacts 5 obtain additional holding and a secure fastening with respect to mechanical loadings.

The known holders mentioned at the beginning, have box-shaped casings or are U-shaped in crosssection with webs against which the parts of the contact frame, which surround the actual contact tongues and from which these tongues extend, must bear and load upon receiving a component. In contrast, the spring contacts 5 in accordance with the invention are readily inserted in the slots in the base and obtain a secure fastening which the upper parts of the spring contacts help to secure when spread under loading by an electrical element. In the direction transversally to the slots 4' the spring contacts 5 obtain across the whole length and height of the slots a secure grip in order to oppose adequate resistance to tilting torque which occurs upon the loading of the upper parts of the spring contacts 5 when they receive an electrical element.

In the longitudinal direction of the slots the same holds good because the side edges are likewise held securely against tilting by corresponding pressure against the end walls of the slots. In order that the spring contacts 5 can be easily inserted in the slots 4', the outside distance apart of the two plug pins formed by the bottom end of each spring contact 5 is slightly less than the length of the slot, and furthermore the slots 4' exhibit at their ends in each case a short widening. By this means mentioned, the initial insertion of the spring contacts 5 is made possible by easy introducing of the plug pins, whereupon the pressing of the spring contacts 5 into the base 4 is effected. In so doing the parts of the spring contacts 4 intended for engagement with the walls of the slots obtain their firm force fit in the base 4. The arrangement with two plug pins is, because of the possibility of heavy current surges in the case of arresters, to be preferred to a construction with one single plug pin.

The free arrangement of the spring contacts 5 above the base 4 has the further advantage that, in contrast to the known holders, the parts made of insulating material lie relatively far removed from the contacts and hence cannot be directly loaded and possibly damaged by the heat arising in service from the arrester.

The previously mentioned short widening at the ends of the slots also serve for the stabilisation of the part of the injection moulding tool forming the slot, since for precision manufacture adequate stability must be imparted to it.

Claims

1. A holder for an electrical element having contact faces at its ends, the holder having two spaced similar spring contacts which are fitted on a mounting made of electrically insulating material and between which the element can be resiliently clamped with its end faces in engagement with the spring contacts, the spring contacts having end extensions for connecting to other electrical connectors, wherein the mounting consists of a base plate having two slots into respective ones of which the spring contacts are inserted as far as the engagement of a stop on each spring contact against a first surface of the base whereupon the end extensions project from the opposite surface of the base; the element engaging parts of the spring contacts converging towards one another in a direction away from the first surface of the base prior to introduction of an element, and being provided on their inner faces with a number of projections which are arranged to embrace the element and to locate it in a predetermined position.

2. A holder according to claim 1, wherein each spring contact has a stop in the form of a jog.

3. A holder according to claim 1 or claim 2, which is intended for use with a printed circuit board, the spring contacts being arranged to be soldered at their end extensions into a printed circuit board.

4. A holder according to any one of the preceding claims, wherein the projections include at least two spaced warts adjacent to the free end of each spring contact.

5. A holder according to any one of the preceding claims, wherein the projections include spaced tongues which are stamped out of the face of each spring contact adjacent to the base and project obliquely inwardly and away from the base.

6. A holder according to any one of the preceding claims, wherein the spring contacts are anchored by being a force fit in the slots in the base.

7. A holder according to any one of the preceding claims, wherein each spring contact is a substantially rectangular-shaped leaf spring of which the end extension is forked.

8. A holder according to any one of the preceding claims, wherein, for making tangential contact with an annular central electrode of e.g. a threeelectrode suppressor, a forklike contact part pointing away from the first surface of the base is arranged between the two spring contacts and is similarly supported in an additional slot in the base so that in use the work prongs contact the central electrode; and an end extension of the contact part projects in the form of at least one plug pin from the opposite surface of the base.

9. A holder according to any one of the preceeding claims, wherein, for receiving two elements and making contact against their end faces, a piece of sheet metal is inserted between the two spring contacts and is similarly supported in a slot in the base.

10. A holder according to claim 9, wherein an end extension of the sheet metal piece projects in the form of at least one plug pin from the opposite surface of the base.

11. A holder according to claim 9 or claim 10, wherein the piece of sheet metal has on at least one face projections similar to those provided on the spring contacts.

12. A holder according to claim 1, substantially as described with reference to the accompanying drawings.