GB2266199A

GB2266199A - Earthing bridging contact

Info

Publication number: GB2266199A
Application number: GB9307181A
Authority: GB
Inventors: Siegmar Birkmann
Original assignee: Schroff GmbH
Current assignee: Schroff GmbH
Priority date: 1992-04-09
Filing date: 1993-04-06
Publication date: 1993-10-20
Anticipated expiration: 2013-04-06
Also published as: JPH0645011A; FR2689719A1; DE4211923C1; ITMI930686A1; JP2602610B2; FR2689719B1; IT1264787B1; GB2266199B; GB9307181D0; ITMI930686A0

Description

2266199 CONTACT ELEMENT The invention relates to a contact element of

metal, e.g. sheet spring steel,for the electrically conductive connection of a partial front plate to a threaded hole strip that is inserted into the open-front receiving groove of a module rail of a subassembly carrier, having contact tips that press under spring tension into the rear side of the fitted partial front plate.

In the case of subassembly carriers that are used for accommodating electrical and electronic subassemblies, lo the partial front plates forming the front end of the apparatus often have to be reliably connected in an electrically conductive manner to the other metal components. especially to the module rails. An earthed conductor function is thereby created which contributes is to the user.'s safety or protects the installed electronic system. It is also necessary to connect all of the housing components to one another in an electrically conductive manner when the installed electronic system has to be shielded from interfering electromagnetic radiation.

The desired electrical connection between the partial front plate and the module rail of the subassembly carrier can be achieved by various methods. For example, the fastening screws for the partial front plate can simultaneously be used to produce an electrical connection. For that purpose, however, the screw must be connected m6tallically both to the partial front plate and to the threaded hole strip inserted Into the module rail. Front plates are. however. generally provided with a non-conductive anticorrosion covering. for example they are lacquered. so that an electrically conductive connection to the module rail can be produced by means of the fastening screw only if special measures are taken to ensure that that surface layer is penetrated.

Spring elements are known that are inserted into grooves of the module rails and contact both the module rail and the front plate or partial front plate with their contact tips. The disadvantage of those spring elements is that they have relatively large dimensions and therefore cannot be used for small subassemblies. Furthermore. it is difficult to add such spring elements to finished apparatuses.

Finally, DE- A-37 17 219 discloses a contact spring that is constructed in a sleeve-like manner with a longitudinal slot. That contact spring can be locked from the front side into a widened portion of the receiving groove of the module rail. which widened portion is provided in front of the threaded hole strip. When the front plate is subsequently screwed on, the contact portion is deformed in resilient manner and is supported against the inwardly pointing sides of the widened groove. The disadvantage of that arrangement is that manufacturing tolerances have a direct effect on the effectiveness of the contact. It may happen, for example, that when the fastening screw has been tightened the front plate and the threaded hole strip are reliably contacted by means of the contact element. but the clamping between the front plate. the threaded hole strip and the module rail is no longer ensured. so that there is not a reliable electrical connection with the frame. A further disadvantage is that the contact spring. which has a very complicated structure,, can be used only in module rails that are equipped with the special widened groove. In addition. once the contact element has been locked in, it is very difficult to remove it from the widened groove again.

A contact component is known for the production of an electrically conductive connection of a front plate to a module rail of a subassembly carrier, which contact component has an H-shaped cross-section and is inserted into a receiving groove in front of the threaded hole strip of the module rail. The tips of triangular contact sites arranged on both sides connect the front plate to the threaded hole strip. The production of that contact component is, however, not very.easy and it is complicated to mount (German Utility Model No. 89 06 492).

Also known is an electrically conductive locking device comprising a flat spring with the aid of which an electrical contact can be produced between the front plate of a plug-in subassembly and the front side of the module rails of a subassembly carrier. But, because in this case the threaded hole strip is not brought into direct electrical connection with the rear side of the front plate, it is in many cases not possible to achieve sufficient attenuation of interference radiation. (East :o German Patent Specification No. 241 176).

The task. of the present invention is therefore to provide an especially simple contact element that is inexpensive to produce and permits a reliable contact between the partial front plate and the threaded hole strip without disturbing the clamped connection between the front plate.. the threaded hole strip and the module rail,,.and fcr it to be poe to. add this contact element rapidly and in a simple manner. without using a tool. even to existing subassembly carriers and also. if necessary. to remove it again without difficulty.

The starting point for the solution to this technical problem is a contact element e.g. of sheet sRring steel, as described at the beginning. The problem is solved by constructing the contact element so that it is substantially U-shaped, the web of the U carrying the contact tips on its outer side and the two limbs of the U being constructed as resilient legs for insertion into a threaded hole of the threaded hole strip.

The contact element constructed according to the invention can be produced from sheet spring steel in a manner that saves material and is simple from the manufacturing standpoint. It can be very readily inserted by its resilient legs into two threaded holes of the threaded hole strip without the need to change the construction of the laodule rail in any way. It is thus also possible to retrofit the element to existing apparatuses without difficulty.

For insertion. the contact element is held with the fingers and introduced by its resilient legs into the threaded hole strip. The length of the said web and thus the distance between the two resilient legs. is so chosen that it corresponds to the distances between the holes of the threaded hole strip. It has been found to be advantageous if the contact element covers a threaded hole that remains free.

A preferred embodiment provides that the web of the U has an outwardly directed bow-shaped curved portion, the outwardly pointing contact tips then advant ageously being arranged symmetrically to that curved portion. If the radius of curvature is so chosen that.

when the contact element is inserted. the outwardly protruding contact tips project beyond the end face of the module rail, the contact element Is resiliently deformed when the partial front plate is screwed onj the contact tips pressing into the rear side of the front plate and the spring force being sufficient to penetrate a non-conductive covering.

In an advantageous development of the invention. the resilient legs have outwardly pointing locking protrus- ions, which render the assembly especially elegant: for insertion, the contact element is held between the thumb and the index finger and first introduced by the free ends of the resilient legs, which are advantageously rounded, into the threaded holes of the threaded hole strip. The resilient legs are of such a length that they permit reliable guiding in the threaded holes even when the remaining portion of the contact element is still outside the rail section and can thus still be held firmly. When the resilient legs have found a certain grip in the holes it is possible to let go of them and the rest of the mounting operation can be effected by pressing with the top of the finger on the highest point of the curved U-wib. As a result, the resilient resistance of the contact protrusions is overcome and the contact element snaps into its intended mounted position.

Especially preferred is an embodiment where the resilient legs are bent back in an inward direction from the U-web to form an acute angle. so that the ends of the resilient legs are closer to one another than are the corner regions formed w ' ith the U-web. This geometry facilitates the introduction of the contact element into the threaded holes and results in a locking fit as soon as the resilient legs have been introduced just a few milli- metres into the holes. An inclined position of the resilient legs with respect to one another at an angle of approximately 10 is sufficient.

The U-back is advantageously wider than the resilient legs, and the resulting transition zones between the resilient legs and the U-web can form corners that form an acute angle. Those corners rest on the front side of the threaded hole strip in a conduct-producing manner even if there are burrs in the area of the edges of the threaded holes. It is sufficient if the angle formed by the corners is approximately 85.

The contact element constructed according to the invention can be produced from a single narrow piece of sheet jo spring metal by stamping and bending. The contact tips may advantageously be constructed as triangular resilient tongues that are bent outwards out of the web of the U.

An embodiment of the invention is explained in more detail hereinafter with reference to the attached drawings.

Figure la is a greatly enlarged front view of a contact element; Figure lb is a side view of the contact element of Figure la; Figure 2 is a developed view of the contact element according to Figure la; - Figure 3 is a partially sectional view of two contact elements inserted into a subassembly carrier.. and Figure 4 is a section along the line A-A of Figure 3.

According to Figure la. the contact element 1 is in the form of a large inverted U,, the web 1 2 having an outwardly directed bow-shaped curved portion 3 and the two limbs of the U being constructed as resilient legs 4. Two outwardly directed contact tips 5 are arranged symmetrically to the curved portion 3. The resilient legs 4 have outwardly pointing locking protrusions 6. The free ends 7 of the resilient legs 4 are rounded.

The contact element 1 is produced from a single narrow piece of sheet spring metal (see Figure 2) by stamping and bending. The contact tips 5 are constructed as triangular resilient tongues that are bent outwards out of the wL-b 2 of the U.

The resilient legs 4 are bent back in an inward direction from the U-web 2 to form an acute angle, so that the ends 7 of the resilient legs 4 are closer to one another than are the corner regions 8 formed with the U-web 2.

The resilient legs 4 are thus inclined towards one another at an angle of approximately 10.

The web 2 is approximately twice as wide as the resilient legs 4 formed in one piece therewith, as is shown especially in Figure 2. The corners 9 formed by the transition zones between the resilient legs 4 and the web 2 form an acute angle 10 of approximately 85.

Figures 3 and 4 show, in a cut-out manner. a subassembly carrier for accommodating electronic subassemblies. The front module rails 11 of that subassembly carrier have a receiving groove 12 into which a threaded hole strip 13 having equidistant threaded holes 14 is inserted. The subassenbly carrier is terminated at the front by several partial front plates 15 which together form the front of the apparatus. Each partial front plate 15 is screwed onto the threaded hole strip 13 by fastening screws 16 so that a clamped connection is formed between the partial front plate 15. the threaded hole strip 13 and the module 8 rail 11.

Before screwing on the partial front plates 15, contact elements 1 can be inserted into two threaded holes 14 each of the threaded hole strip 13. For that purpose, the contact element 1 has to be introduced by its resilient legs 4 into the threaded holes 14 and clipped in by pressure on the web 2.

The mounted contact element 1 is held in the threaded hole strip 13 by the locking protrusions 6 provided on the resilient legs 4. The curved portion 3 of the web 2 is of such a size that the contact tips 5 project slightly forwards out of the module rail 11. As a result, the contact tips 5 press into the rear side of the partial front plate 15 which is screwed on subseq- uently,, the surface covering of the partial front plate 15 being penetrated.

The contact element 1 secures the electrically conductive connection between the partial front plates 15 and the threaded hole strip 13 which, in its turn, is connected in a clamped manner to the module rail 11. The spring excursion produced by the curved portion 3 balances out any dimensional tolerances.

- 9 List of reference numerals contact element 2 web of the U 3 curved portion 4 resilient leg contact tips 6 locking protrusion 7 end a corner region 9 corner angle 11 module rail 12 receiving groove 13 threaded hole strip 14 threaded hole is partial front plate 16 fastening screw 10.

Claims

1. A contact element of metal, e.g. sheet spring steel, for the electrically conductive connection of a partial front plate to a threaded hole strip that is inserted into the open-front receiving groove of a module rail of a subassembly carrier, having contact tips that press under spring tension into the rear side of the fitted partial front plate, the element being constructed in substantially U-shape, the web of the U carrying the contact tips on its outer side and the two limbs of the U being constructed as resilient legs for insertion into a respective threaded hole of the threaded hole strip.

2. An element according to claim 1, wherein the said web has an outwardly directed bow-shaped curved portion.

3. An element according to claim 1 or 2, wherein two outwardly pointing contact tips are arranged symmetrically about the curved portion.

4. An element according to any preceding claim in which the resilient legs are provided with outwardly pointing locking protrusions.

5. An element according to any preceding claim in which the free ends of the resilient legs are rounded.

6. An element according to any preceding claim in which the resilient legs are bent back in an inward direction from the said web to form an acute angle, so that the ends of the resilient legs are closer to one another than are the corner regions formed with the said web.

7. An element according to claim 6, in which the resilient legs are inclined towards one another to form an angle of substantially 100.

PAnNS297.1

8. An element according to any one of claims 1 to 7, in which the said web is wider than the resilient legs.

9. An element according to claim 8, in which the corners formed by the transition zones between the resilient legs and the said web form an acute angle.

10. An element according to claim 9, in which the angle is approximately 850.

11. An element according to any preceding claim in which it is produced from a single narrow piece of sheet spring metal by stamping and bending.

12. An element according to any preceding claim in which the contact tips are constructed as triangular resilient tongues that are bent outwardly out of the said web.

13. A contact element substantially as herein described with reference to and as shown in the accompanying drawings.

PATW297.1