GB2170063A - Electrical connections allowing relative movement - Google Patents

Abstract

An electrically conductive and flexible connection is provided in a relatively narrow space between two components 1,2 movable in relation to each other, as are found, for example, in an illuminated key or push-button switch on a keyboard, the connection comprising two parts (8) which extend in the same direction and are connected together both electrically and mechanically at their adjacent overlapping ends (9), the other ends being secured respectively to the two components at (4). <IMAGE>

Description

SPECIFICATION Improvements in and relating to electrical connections The present invention relates to an electrical conductive connection.

Certain types of technical devices or equipment require two movable or relatively movable components to be interconnected by an electrical conductive link or connection. Examples of these are key or button switches having built-in illumination or indicators in their caps in the form of alphabetical letters, numerals or mathematical or other special symbols, which are used in keyboards for the input of information into associated equipment, such as typewriters, computers, calculators or similar.

Other examples are as links for robot arms or printers, which are also of small dimensions. A primary requirement for such devices is that the electrical connection has to fit within a small space for example, the arrangement or layout of a keyboard is effected according to predetermined standards, and consequently the connection has to be made within the predetermined distances/pitch of the keys. In addition, there is a technical requirement that the connection has to withstand many cycles of movement of the interconnected components over several million operations of the key or push button made during normal use. Furthermore, the amount of force required to move the components must be within a preset limit.The force required to activate a key or pushbutton is less than one Newton, and any additional reinforcing of the return spring would lead to an increased duration in the operation of the key and an unreasonable load for the user. In addition, frictional losses must be limited, so that a rapid sequence of movement is possible.

These requirements are contrary to each other to some extent. A high service life of the connection demands a large radius of curvature of the connection, and, therefore, a corresponding increase in space which is not available. A relatively thin insulation or covering of the conductor for effecting a limited expenditure of operating force is necessary.

However, as a result, there is a lack of mechanical guidance, which ensures a uniform distribution of the bend over a long conductive piece/element.

The connection then tends to bend, without exception, at slight irregularities, whereupon this point becomes overstressed and the connection then breaks prematurely at this point. The known and conventional electrical wirings are such, that the conductor/wire is fixed by its ends to both parts/ components, which move in relation to each other, whereby the wire/conductor forms a U-shaped loop. In the region of the radius of the bend and at the point of the sharpest bend/kink the connecting wire/conductor is subjected to the greatest stress.

With this the service life at the radius of the bend increases exponentially, or conversely, a confinement of the pitch/distance between the two components leads, to the same extent, to a severe reduction in the service life. Since the wire/conductor features a certain thickness, the bending of the material results in a kink which does not fully recover (return to its original position) and, as a result, leads to damage of the wire/conductor.

The invention sets out to provide an improved connection.

Accordingly the present invention provides an electrically conductive connection for connecting together two components movable relative to one another, the connection comprising two conductive parts extending generally in the same direction and mechanically and electrically joined in overlapping relationship.

An adgantageous embodiment exists in the fact that the ends of the conductive components running in the same direction are separated and joined together. Furthermore, it is advantageous that a clip connector is fitted preceding the zone of the sharpest bend/kink.

Finally, it is advantageous that the connection is made to a key switch having a movable cap equiped with a built-in indicator.

The connection to a key switch preferably consists of a flexible base material, e.g. copper coated plastic film/sheet.

In accordance with another preferred embodiment, a corresponding number of connections is provided for a plurality of such types of bends.

The advantages primarily are a result of the fact that the problem described in the preamble can be resolved by a conceivably simple solution, and a conductive link is thus created for the narrowest of spaces, which withstands the required multiplicity of cycles of movement without adversely affecting the desired speed of sequential movements or requiring an increase in operational force.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a conventional connection between two components of a key or push-button movable relative to each other; Figure 2 shows a connection in a two-part form separated in the region where its radius of curvature is smallest; Figure 3 shows one embodiment of a connection according to the present invention; Figure 4 shows the components of the connection of Figure 3 at a small separation; Figure 5 shows the components at smaller separation than shown in Figure 4; Figure 6 shows a second embodiment of a connection according to the present invention where the connection fixing points are not directly opposite one another; and Figure 7 shows a third embodiment of a connection according to the present invention.

Figure 1 schematically illustrates a conventional key or push-button switch which has a first member in the form of a button or key 1 movable towards and away from a stationary base member 2.

Apart from the switches own internal connections which are made or broken by movement of the button 1, a permanent electrically conductive and flexible or resilient connection 3, shown shaped in the form of a 'U' on its side, is provided between the two switch members 1, 2 with the opposite ends of the connection 3 being secured to respective opposite fixing locations 4 on the two members. The connection 3 serves for example, to supply power to illuminate indicia on the switch push-button.

On depressing the button 1 in the direction of arrow 5 the region 7 of the connection, having the smallest radius of curvature, i.e. with the sharpest bend, is bent even further (the radius of curvature is reduced) and is pressed outwards in the direction of the arrow 6 with the result that a corresponding deformation or kink is formed in this region 7.

Figure 2 shows a switch whose connection 3 is in two parts 8 separated in the region 7, the connection being shown prior to joining of the two parts where adjacent ends 9 of the conductive parts 8 are flattened and laid directly on each other and then mechanically and electrically joined together as shown in Figure 3 to form a connection according to the present invention. Thus, in contrast with the switch of Figure 1 where the connection turns back on itself through a relatively sharp bend, the two parts 8 of the connection of Figure 3 extend in the same direction and are joined in overlapping relationship at or adjacent their free ends without any sharp curving or bending of the connection parts 8 being necessary.

Figure 4 shows the position of the switch parts when the button 1 is moved closer to the base member 2 and it can clearly be seen that where the conductive parts 8 of the connection are bent, the bends have relatively large radii of curvature compared to that of the bend shown in Figure 1.

Stress applied to the conductive parts is therefore distributed relatively uniformly over a much larger area.

Figure 5 shows the switch of Figure 3 with the button 1 and base member 2 at their smallest separation. As can be seen from Figures 3, 4 and 5 during movement of the members 1, 2 towards and away from one another the two conductive parts 8 effectively 'roll' and 'unroll' into and out of contact along their lengths.

In the embodiment shown in Figure 6 the fixing locations 4 of the two conductive parts 8 are not directly opposite one another but are off-set laterally of the direction of movement of the button 1.

However, the connection operates in the same manner as that of Figures 3 to 5.

Figure 7 shows a further embodiment where the connection 3 is in one piece. As can be seen, the two limbs 8 of the U-shaped connection are mechanically secured together adjacent the region 7.

This connection operates in the same manner as those of Figures 3 to 6 but, in contrast with the prior art connection of Figure 1, since the two limbs 8 are mechanically joined by a clip 10 the stress applied to the end region 7 is fixed and does not vary with movement of the button 1 as is the case in the connection of Figure 1. Since the connection is a one-piece connection the clip 10 need only be a mechanical joint and not an electrical joint. As an alternative to the clip 10 the limbs 8 can be mechanically secured by, for example, an adhesive or by welding or fusion.

Claims (7)

1. An electrically conductive connection for connecting together two components movable relative to one another, the connection comprising two conductive parts extending g.enerally in the same direction and joined in overlapping relationship.

2. An electrical connection in accordance with Claim 1 wherein the adjacent ends of the conductive parts are not integral with one another and are electrically and mechanically secured together.

3. An electrical connection in accordance with Claim 1 wherein said conductive parts are interconnected by a clip connector, an adhesive or a welded/fusion joint.

4. An electrical connection in accordance with any of Claims 1 to 3, wherein the connection to a key switch is provided with a movable cap having a built-in indicator.

5. An electrical connection in accordance with any of Claims 1 to 4, wherein the connection on a key switch consists of a flexible base material.

6. An electrical connection in accordance with any of Claims 1 to 5, characterised in that for a plurality of such types of bends a corresponding number of joints is provided.

7. An electrical connection substantiaily as hereinbefore described with reference to Figures 2 to 5, or Figure 6 or Figure 7 of the accompanying drawings.