Power assist device using strain responsive means

For use with x-ray apparatus having a moveable component which is subject to being selectively positioned and having motor means operatively coupled to said component for driving it to desired positions;

• control means comprising:
• manually engageable handle means coupled to said component and subject to having a manual force applied substantially in the direction in which movement of said component is desired,
• strain responsive means having input and output means,
• means for imparting a strain to said means in correspondence with the force applied to said handle means,
• said strain responsive means having the property of varying its electric resistance in response to varying the strain imparted thereto,
• voltage source means for providing a voltage to said input means to produce a predetermined output signal at said output means in the absence of a force and to produce an error signal having a magnitude and polarity depending on the magnitude and direction respectively, of the applied force, and
• means for operating said motor in response to said error signal, and
• including means for inactivating said control means in the event of failure of said strain responsive means, comprising:
• amplifier means having input and output means,
• means for producing a signal corresponding with the magnitude of electric current supplied to said strain responsive means and said amplifier means,
• window comparator means having input means for said signal and having output means which change state in response to said current going above and below a predetermined magnitude indicative of failure, and
• means coupled with the output means of said comparator means and responsive to one state thereof by enabling said means for operatiang said motor to operate said motor and responsive to another state of said comparator means which corresponds with failure by disabling said means for operating said motor.

For use with x-ray apparatus having a moveable component which is subject to being positioned selectively and having motor means operatively coupled to said component for driving it to desired positions;

• control means comprising:
• manually engageable handle means for applying a manual force substantially in the direction in which movement of said component is desired,
• beam means coupling said handle to said component, said beam means being yieldable by a small amount in response to said force being applied to said handle,
• strain responsive means mounted to said beam means and subject to having a strain imparted thereto in response to yielding of said beam means, said strain responsive means having the property of varying its electric resistance in correspondence with the strain therein and having input means for being connected to an electric power source and having output means for an error signal that has magnitude and polarity which depends on the amount and direction, respectively, in which said beam means yields,
• amplifier means having input and output means, the input means of said amplifier means being connected to receive said error signal from said strain responsive means and said amplifier means producing a corresponding output signal, and
• means for controlling operation of said motor means in response to said last named output signal.

For use in x-ray apparatus having a moveable component which is subject to being positioned selectively and having motor means for driving said component to desired positions;

• manually engageable handle means coupled to said component for applying a manual force in either of opposite directions in which movement of said component is desired,
• strain responsive means mounted for being strained in response to a manual force being applied to said handle means in either of said directions,
• said strain responsive means comprising a piezoresistive element, which has the property of varying its electric resistance in response to being strained, and a reference resistive element,
• a source of d-c voltage, said elements being connected in series with each other and between said source of voltage such that a predetermined signal is developed at a point intermediate said elements when substantially no force is applied to said handle and an error signal is developed at said point when a force is applied to said handle, said error signal having a magnitude and polarity depending on the magnitude and direction of the force applied to said handle, and
• means including motor control means responsive to said error signal by causing said motor to drive said component during existence of said error signal and in a direction corresponding with the direction in which said manual force is applied.