1. Field of the Invention
This invention relates generally to a portable power tool of the impulse type and more particularly to an impulse device designed to deliver a controllable torque to a threaded fastener.
2. Description of the Prior Art
In many industrial applications it is desirable to tighten threaded fasteners to a predetermined torque automatically and rapidly. Such applications include internal combustion engine head bolts and connecting rod bearings and wheel nuts or studs. Many applications also exist, particularly in the maintenance area, where it is necessary to loosen threaded fasteners in order to disassemble a machine. While it is desirable that the tool develop a predetermined torque, it is also important to be able to adJust the predetermined torque and to use the same tool for tighlening and loosening threaded fasteners.
A number of devices have been developed utilizing either an electric motor or an air motor as the powering mechanism. Generally, an hydraulic or mechanical mechanism is attached to the output shaft of the air or electric motor which is adapted to convert the rotary motion into torque impacts. The production of torque impacts within the torque conversion mechanism often leads to high impact stresses and consequent wear of the working parts of the mechanism. Where a series of impacts or hammer blows is entailed, the predetermined torque may be exceeded. It is an object of the present invention to develop a controllable predetermined torque through cyclical impulses which do not constitute a series of impacts. It is also an object of the invention to reduce the noise associated with the prior art torque devices of the impact type.