US 5,963,707 A · Method and apparatus for determining and adjusting torque in an electric impact torque wrench

Abstract

A method and apparatus for adjusting torque in an electric impact torque wrench. A current sensing circuit passes current through a power relay for powering an electric impact torque wrench. The power relay is normally in a conducting state. The current sensing circuit includes a threshold current indicator which is activated when current flowing through the current sensing circuit reaches a predetermined threshold amount. The threshold current indicator is provided to a first timer which counts an activation-off time since the threshold indicator is activated, the first timer presuming that the current has remained above the predetermined threshold amount during this time. At the conclusion of the activation-off time, the first timer signals a time-off extender circuit. On receipt of the signal, the time-off extender circuit (1) switches the power relay to a non-conducting state, to interrupt the flow of current therethrough, (2) counts a predetermined time-off time, at the conclusion of which the time-off extender circuit switches the power relay back to the conducting state, and (3) resets the first timer for repeat of the aforedescribed cycle.

Claims11

Dependent claims

An apparatus for adjusting torque in an electric impact wrench to provide a desired torque, comprising:

a power input for receiving electrical power from an electrical current source;
a switchable electrical power output for selectably delivering said electrical power to the electric impact torque wrench, said switchable electrical power output being adapted for switching between a substantially conducting state of said electrical power output and a substantially non-conducting state thereof;
a power sensing circuit coupled to said electrical power input and adapted for determining whether said power exceeds a predetermined threshold amount;
and
a first timing circuit coupled to said power sensing circuit and adapted for timing a predetermined on-duty time interval after said power is determined to exceed said threshold amount, wherein said switchable electrical power output is adapted to switch from said conducting state to said non-conducting state at substantially the end of said on-duty time interval for a substantial fraction of the total time required to provide the desired torque.

2 more elements

A method for adjusting torque in an electric impact torque wrench to provide a desired torque, comprising:

providing a switchable source of electrical power to the electric impact torque wrench, said switchable source of electrical power being adapted for switching said electrical power between a substantially on state and a substantially off state;
determining whether the power exceeds a predetermined threshold amount;
timing, after the time said power is determined to exceed said predetermined threshold amount, a predetermined on-duty time interval;
and
switching, after about the end of said on-duty time interval, said switchable source of electrical power from said substantially on state to said substantially off state for a substantial fraction of the total time required to provide the desired torque.

2 more elements

Dependencies are inferred from the claim text.

Method and apparatus for determining and adjusting torque in an electric impact torque wrench

Life of this patent

Method and apparatus for determining and adjusting torque in an electric impact torque wrench

Life of this patent

Abstract

Claims11