Liquid level sensor switch

Abstract

A liquid level sensor switch comprising a case, a rod type guide vertically extending from an inside bottom center of the case, a float having a center bore fitted on the guide with a clearance allowing the float to freely move up and down along the guide inside the case, an electrode plate attached to a circumferential bottom surface of the float and a pair of fixed contacts disposed opposite to each other across the guide on the inside bottom surface of the case, wherein the float moves down with the drop of oil in the case along the guide to reach a lowest position at which the electrode plate makes contact with both the fixed contacts to turn on a circuit formed by the electrode plate bridging between the contacts for producing an electrical signal indicating that oil surface is lowered to or below a specified level, which is featured by using the guide having a body tapering upward from its bottom end or the float having the center bore tapered to be gradually larger in diameter upward from its bottom end to prevent the float from putting the electrode plate into poor contact with the both contacts due to variations in height of the paired contacts when the switch used in a tilted state with the float inclined aside with its center bore abutting on the guide and which is also featured by using a combination of the cylindrically formed guide and the float having a center bore having a polygonal cross section or a combination of the guide having a polygonal cross section and the float having the round center bore to prevent the float from adhering to the float to the guide due to the effect of the surface tension of oil between them when the switch is used in a tilted state.