Electric switch with welded contact sensor lockout

An electric switch comprising:

• an insulating housing having an interior chamber and an opening communicating with said chamber;
• stationary contacts mounted in said chamber;
• a plunger assembly mounted for reciprocal movement in said housing, said plunger assembly comprising a switch operator extending through said opening and a contact carrier mounted for movement relative to said switch operator;
• a first spring biasing said plunger assembly to an extended position;
• a pair of movable contacts mounted on said contact carrier engagable with respective said stationary contacts upon application of an operating force to said switch operator moving said plunger assembly against the bias of said spring to a depressed position;
• a bridging contact mounted for movement with said switch operator and normally engaging said movable contacts in said extended and depressed positions of said plunger assembly;
• and
• a second spring interposed said operator and said contact carrier biasing said operator away from said contact carrier toward said extended position, said second spring being effective, upon welding of said movable contacts to said stationary contacts and removal of said operating force from said switch operator, to drive said operator away from said contact carrier and said bridging contact out of engagement with said movable contacts.

A method of opening a circuit within an electric switch when primary contacts of the switch weld together comprising the steps of:

• providing spaced stationary contacts;
• guiding a plunger assembly comprising a contact carrier and a switch operator movable relative to said contact carrier for reciprocal movement in proximity to said stationary contacts;
• biasing said plunger assembly to an extended position;
• providing spaced movable contacts on said contact carrier as primary contacts engagable with respective said stationary contacts upon operation of said plunger assembly from said extended position to a depressed position;
• providing a secondary contact in bridging engagement with said spaced movable contacts;
• biasing said switch operator and said secondary contact away from said contact carrier and out of engagement with said spaced movable contacts when the latter fail to separate from said stationary contacts under the bias of said plunger assembly to said extended position.

An electric switch comprising:

• an insulating housing having an interior chamber and an opening communicating with said chamber;
• stationary contacts mounted in said chamber;
• a plunger assembly mounted for reciprocal movement in said housing, said plunger assembly comprising a switch operator extending through said opening and a contact carrier mounted for movement relative to said switch operator;
• a first spring biasing said plunger assembly to an extended position;
• a movable contact mounted on said contact carrier engagable with and bridging said stationary contacts upon application of an operating force to said switch operator moving said plunger assembly against the bias of said spring to a depressed position;
• a secondary movable contact mounted for movement with said switch operator, said secondary movable contact having wiping engagement with said movable contact upon movement of said switch operator relative to said contact carrier;
• a secondary stationary contact disposed for engagement by said secondary movable contact in said extended position of said plunger assembly, said secondary stationary contact and one of said stationary contacts being connectable to an electrical power supply;
• an electric fuse connected to said one of said stationary contacts;
• and
• a second spring interposed said operator and said contact carrier biasing said operator away from said contact carrier toward said extended position, said second spring being effective, upon welding of said movable contact to said stationary contacts and removal of said operating force from said switch operator, to drive said operator away from said contact carrier and drive said secondary movable contact into engagement with said secondary stationary contact, rendering said fuse directly connectable across said electrical power supply.