An overcenter mechanism comprising: a housing; a first shaft mounted on the housing, the first shaft defining a first axis; a second shaft mounted on the housing, the second shaft defining a second axis that parallels the first axis; a lever attached to the first shaft, the lever pivoting about the first axis in response to a force applied to the lever; a cam attached to the first shaft, the cam pivotable about the first axis, the cam having a cam surface including a first surface portion and a second surface portion, the first and second surface portions forming a cusp therebetween; a cam follower having a cam follower surface, the cam follower pivoting about the second axis; and a biasing member that urges the cam follower surface against the cam surface in pressure contact, the pressure contact cooperating with the cam follower during pivoting of the lever to generate torque on the cam until the cam follower surface approaches the cusp, the pressure contact creating an instability about the cusp when the cam follower surface contacts the cusp, such that the torque pivots the cam so the cam follower moves away from the cusp; characterized in that - the first and second surface portions (58, 60) are convex surfaces and are elongate and curve arcuately toward each other to define a cam profile including the cusp at the junction of the surface portions (58, 60), wherein the first and second surface portions (58, 60) each define a convex profile. a housing; a first shaft mounted on the housing, the first shaft defining a first axis; a second shaft mounted on the housing, the second shaft defining a second axis that parallels the first axis; a lever attached to the first shaft, the lever pivoting about the first axis in response to a force applied to the lever; a cam attached to the first shaft, the cam pivotable about the first axis, the cam having a cam surface including a first surface portion and a second surface portion, the first and second surface portions forming a cusp therebetween; a cam follower having a cam follower surface, the cam follower pivoting about the second axis; and a biasing member that urges the cam follower surface against the cam surface in pressure contact, the pressure contact cooperating with the cam follower during pivoting of the lever to generate torque on the cam until the cam follower surface approaches the cusp, the pressure contact creating an instability about the cusp when the cam follower surface contacts the cusp, such that the torque pivots the cam so the cam follower moves away from the cusp; characterized in that - the first and second surface portions (58, 60) are convex surfaces and are elongate and curve arcuately toward each other to define a cam profile including the cusp at the junction of the surface portions (58, 60), wherein the first and second surface portions (58, 60) each define a convex profile. - the first and second surface portions (58, 60) are convex surfaces and are elongate and curve arcuately toward each other to define a cam profile including the cusp at the junction of the surface portions (58, 60), wherein the first and second surface portions (58, 60) each define a convex profile.