Multiple push-button switch arrangement

A multiple push-button switch arrangement comprising:

• (a) a box-shaped casing made of synthetic resin and having an upper opening;
• (b) a plurality of sets of fixed and movable contacts disposed within a lower portion of the casing;
• (c) a plurality of movable stems made of synthetic resin, at least parts of the stems extending in the casing, each stem holding a respective set of the fixed and movable contacts in mutual electric contact when the stem is depressed and out of contact when the stem is retracted;
• (d) a plurality of push buttons mounted on upper ends of the stems respectively;
• (e) means for locking a set of the contacts in contact when its respective stem is depressed and for unlocking that set and moving its contacts out of contact when another stem is depressed comprising an interlink plate made of synthetic resin, the interlink plate being inserted through the upper opening into the casing and placed in a position where the interlink plate extends horizontally, the interlink plate being urged horizontally;
• (f) means for preventing the contacts of at least two of the sets from being simultaneously locked in contact comprising a simultaneous lock prevention plate made of synthetic resin, the simultaneous lock prevention plate being inserted through the upper opening into the casing and placed in a position where the simultaneous lock prevention plate extends horizontally on the interlink plate;
• and
• (g) posts projecting from a bottom wall of the casing in a direction along which the stems are movable, the stems having side projections respectively, the simultaneous lock prevention plate extending outward of the posts and being movable horizontally, the simultaneous lock prevention plate having a groove, wherein the distance between the groove and an edge of the simultaneous lock prevention plate is smaller than the distance between the side projections on the adjacent stems.