The invention relates to a pushbutton switch arrangement in which the switches are mounted parallel in relation to one another on a U-shaped bar extending vertically in relation to the pushbutton switches, in which a locking bar cooperating with the switch slides and provided with cams, is arranged displaceably in the longitudinal direction.
For the switching of electrical equipment, such as radio and television receivers, mostly several pushbutton switches are required for the individual functions. These switches are mostly arranged parallel in relation to one another and mounted on a U-shaped bar extending vertically in relation to the switches, with this bar also being referred to as the chasis. Mostly it is still required that upon actuation of one pushbutton switch, another already depressed switch returns to normal, or that by one depressed pushbutton switch all other switches can be returned to their non-depressed positions. For this purpose it is known to arrange in the U-shaped hold bar a locking bar which is provided with individual cams for cooperating with the slides of the individual pushbutton switches. Upon actuation of one pushbutton switch, the bar is displaced in such a way by thecorresponding cam, that at least one further cam will release the slide of another pushbutton switch, so that the latter is permitted to return to normal. This is referred as the mutual release of pushbuttons. In practice, there are used several types of embodiments of such locking bars.
Locking bars of metal, such as of steel, are made by way of punching, and the engaging cams are bent out of the bar. Such bars are relatively exact in their dimensions, but must go through several steps of operation in the course of being manufactured. Thus, it is necessary to remove the burrs, and to restraighten the mostly bent parts. The length of such blocking bars is restricted owing to the tools used for the manufacture, so that in cases where longer locking bars are required, several such bars have to be connected to one another via a suitable coupling. Moreover, locking bars of metal have the disadvantage of having a relatively high weight and of being slow in functioning, because relatively great masses have to be accelerated during actuation.
Locking bars, therefore, have also already been made from plastics material. Here, too, the length of the individual bar is restricted by the employed tool, e.g., the injection moulding tool. Accordingly, in cases where long switch arrangements are required, several bars have to be coupled to one another also in this case. Locking bars of plastics material, of course, have a lower weight, so that weaker locking slide springs can be used, and are of easier action than locking bars of metal. Plastics materials, however, compared with metal, have a higher heat expansion coefficient, so that in the case of temperature variations, there also appear variations in length with respect to the U-shaped hold bar of metal, thus causing detrimental effects on the locking function of the bar. The proper functioning of the bar is affected in the case of many plastics materials by the relatively high absorption of moisture.
Accordingly, both kinds of locking bars have the disadvantage that they can only be manufactured in restricted lengths, and that in the cases where greater lengths are required, coupling elements have to be employed between the individual bars. Both kinds of locking bars, however, also have the disadvantage that different tools are required for bars having a different spacing between locking cams, thus resulting in a substantial increase in costs, affecting both manufacture and stockkeeping. In fact, in practice the distances between switches in the case of new types of equipment, are always again varied either for constructional or aesthetic reasons so that, although the same switches are used, there are always again required different locking bars with different spacings between cams.
It is the object of the invention to provide a locking bar which can practically be manufactured in any desired length, and with which the spacings between locking cams are variable at will from bar to bar.