Patent ID: 8365641

Claim:
A torque wrench comprising: a shaft with a longitudinal axis; wherein the shaft has a lower end and an upper end, the lower end being configured to engage a fastener; a shaft cam configured to rotate with the shaft around the longitudinal axis; a groove defined in the shaft cam by opposed side walls and an upper groove surface; a ramp positioned within the groove between said side walls, wherein the ramp comprises a ramp upper surface spaced from the upper groove surface and having a first lower point, a first upper point and a surface extending along a perimeter of the shaft cam between the first lower and first upper points at an angle with respect to the longitudinal axis; the ramp upper surface is configured so that the first upper point is positioned in the direction of the intended torque with respect to the first lower point; a housing surrounding the shaft and shaft cam; wherein a housing groove is defined in the housing; an outer cam comprising an engaging member extending within the housing, wherein the engaging member is configured to selectively contact the ramp upper surface; a spring configured to apply a downward force on the outer cam, such that the engaging member applies a force against the ramp which tends to hinder the shaft cam from rotating with respect to the housing when the ramp upper surface is in contact with the engaging member of the outer cam; and a void defined in the groove between the ramp and a side wall of the groove, the void configured to allow the engaging member to escape the groove when it is not constrained by the ramp.