Switches of the present type which permit multi-speed operation of household appliances, such as food mixers and the like, are well known. One such switch and the environment in which it is utilized is disclosed in U.S. Pat. No. 3,725,624 issued Apr. 3, 1973, and as such, is representative of the present state of the art of such switch designs. Such switches include frame components, a rotor and a plurality of identical conductor blades each having a generally V-shaped detent intermediate the extent thereof which serves to activate various speed-control circuits by engaging cam recesses staggered around the rotor so that each switch may be closed while the others are held open. Where the speed selector circuit includes diode means, each rotor cam is provided with two diametrically opposed cam recesses, one series of recesses operating in combination with a high 180.degree. cam land of an added cam surface, and the other series operating in combination with the low-cam profile on the remaining 180.degree. periphery thereof. An added high-low cam surface of this type serves to double the available speeds otherwise provided by such coil control switches. The operational mode of such switches and their manner of use in home appliances of the aforementioned type may be seen by specific reference to the aforementioned patent.
Disadvantages of prior art switches generally include their lack of a positive feel between speed positions, and the undesirable possibility that the switch may become lodged or hung up between selected speed positions on the rotor while the main circuit is activated, whereby a person, erroneously thinking the switch is in "off" position, may move the rotor into operative position while cleaning beaters or the like, hence raising the danger of physical injury.
In addition, previously known switch constructions of this type usually require that the conductor blades be plated with a nonoxidizing, highly conductive metal, such as silver, in order to achieve the necessary conductivity that the higher rating outputs require of such devices. Highly conductive materials such as silver are extremely expensive, and it would accordingly be desirable if the same operating outputs could be achieved using unplated copper or brass conductor blades. It is also desirable that the speed-selection rotor of switches of the type here under consideration be so constructed that the amount of force necessary to turn the rotor be equal in either direction. Furthermore, in the manufacture and assembly of such prior art switches, the resilient conductor blades thereof are normally pre-stressed so as to achieve the correct force engagement with a common conductor so as to achieve the required power ratings. In many cases, however, the contact pressure of the blades may be undesirably reduced by repeated use of the switch or by annealing of the blades that may take place by heat generated during assembly, such as by ultrasonic welding or the like. It is therefore desirable to provide means to maintain proper contact pressure and to eliminate or lessen the other stated shortcomings of known prior art switches of the type here under consideration.