US Patent 7131356 Hand tool having an adjustable head with joint lock mechanism

A hand tool having an adjustable head with a joint lock mechanism. The joint lock mechanism includes a first engaging device, a second engaging device, a pull button and a first elastic device. The pull button has a knob portion and an engaging portion beneath the knob portion and the engaging portion engages the second engaging device. The first elastic device is received in a first aperture and abuts against the second engaging device with a forward force such that the front end of the second engaging device is pushed to engage the first engaging device.