Camstack timers have been used in many household appliances, such as dishwashers, clothes washers, clothes dryers, etc. These timers control the operational cycles of appliances by opening and closing switches to start and stop various motors, actuate various valves, and illuminate indicators. The switches (“camstack switches”) are actuated and de-actuated as a timer motor turns a camstack, which is a cylindrical structure having undulations in its circumference. These undulations act as cams that move cam followers riding against the circumference of the camstack. The movements of these cam followers under the influence of the cam surfaces on the camstack result in the opening and closing of switches in switch assemblies. These switches, in turn, determine whether electrical current is applied to the motors, actuators, values, and indicators of the appliance.
To orient the camstack to an appropriate position to perform an operational cycle for the appliance, the camstack typically includes a shaft that extends beyond the surface of a control panel where a knob is mounted to the shaft. The knob usually includes an index mark that can be aligned with cycle indicia located on the control panel about the knob. Typically, the knob is rotated so the knob index is aligned with the cycle indicia that the operator wants the appliance to perform and then the appliance is activated. The timer motor then begins to rotate the camstack to operate the motors, actuators, valves, and indicators of the appliance to perform the selected cycle.
Manual rotation of the control knob to the position for selecting a cycle may adversely affect the components of the timer. For example, if electrical line power is available for application to the camstack switches by the interaction of the cams on the camstack and the cam followers, the switch contacts may experience damage from arcing as the contacts are closed and opened quickly. To address this risk of damage, some appliances have included dedicated manually operated line switches that are separate from the camstack timers. These separate line switches are manually moved by the operator to disconnect electrical line power from the timer switch assemblies before the control knob is rotated to the desired start position. Once the initial position is reached, the switch is moved to reapply electrical line power to the timer. However, operator error may result in the separate line switches not being used before the control knob is rotated to a position for cycle commencement.
More recently, U.S. Pat. No. 4,146,760 to Voland (“Voland”) discloses, among other things, a camstack timer including a line switch such that alternative manual axial indexing of a control knob can alternatively open and close the line switch, while the camstack setting can still be manually adjusted by rotating the same control knob. Also, U.S. Pat. No. 4,892,982 to Hueber et al. discloses a timer mechanism with an improved clutch assembly. The device disclosed in this patent also includes a switch actuator that selectively disengages a set of electrical contacts based on axial position of a shaft within the camstack structure. This structure, however, requires operator movement of the shaft to both engage and disengage the electrical contacts. Additionally, the switch actuator is not fixedly linked to the contacts. Consequently, slippage and wear over time may result in the contacts becoming close enough to arc even though the shaft is in position to disengage the electrical contacts.