Wrench extension with a socket-coupling system

A socket-coupling system comprising:

• a wrench extension shaft including an end, the end including an axial passageway extending along a longitudinal direction of the wrench extension shaft, the end further including a first transverse passageway extending in a direction transverse to the longitudinal direction of the wrench extension shaft, the first transverse passageway including an inner end communicated with the axial passageway and an outer end communicated with outside, the wrench extension shaft further including a second transverse passageway defined in an outer periphery thereof and extending in a direction transverse to the longitudinal direction of the wrench extension shaft, the second transverse passageway being communicated with the axial passageway and having an outer end communicated with outside;
• a transmission member mounted in the axial passageway and slidable along the longitudinal direction of the wrench extension shaft, the transmission member including a recessed portion in an outer periphery thereof, the transmission member further including an inner end having a pressing face extending along a direction substantially perpendicular to a longitudinal direction of the wrench extension shaft, the inner end of the transmission member further including an inclined sliding face at an acute angle with the longitudinal direction of the wrench extension shaft;
• a latch partially received in the first transverse passageway and movable along an extending direction of the first transverse passageway, the latch being partially received in the recessed portion of the transmission member;
• a push member mounted in the second transverse passageway and slidable along an extending direction of the second transverse passageway, the push member including an operative section having a pressing face extending in a direction perpendicular to the longitudinal direction of the wrench extension shaft, the operative section of the push member further including an inclined sliding face in sliding engagement with the inclined sliding face of the transmission member allowing mutual sliding movement between the inclined sliding face of the push member and the inclined sliding face of the transmission member;
• and
• an elastic element mounted in the second transverse passageway for biasing the push member to an undepressed position;
• wherein when the push member is pushed and a socket is coupled to the end of the wrench extension shaft, the latch is moved inward to allow passage of the socket, and the transmission member is moved by the latch along the longitudinal direction of the wrench extension shaft, and when the push member is released, the transmission member is moved along the longitudinal direction of the wrench extension shaft in response to movement of the push member under action of the elastic element until the recessed portion of the transmission member urges the latch to protrude into a detent of a cavity of the socket coupled to the end of the wrench extension shaft;
• and
• wherein when the socket is subject to a force along the longitudinal direction of the wrench extension shaft for moving the socket away from the end of the wrench extension shaft, the pressing face of the transmission member is stopped by the pressing face of the push member, thereby preventing further movement of the transmission member along the longitudinal direction of the wrench extension shaft and reliably retaining a protruded portion of the latch in the detent of the socket.