SOLID STATE CONTROL FOR HOSPITAL BED MOTORS

• US 3,921,048 A
• Filed: 07/18/1973
• Issued: 11/18/1975
• Est. Priority Date: 10/08/1971
• Status: Expired due to Term

• Current Assignee: B-W Health Products Incorporated
• Original Assignee: Kenneth W. Padgitt
• Inventors: Padgitt, Kenneth W.
• Primary Examiner(s): Dobeck, B.
• Application Number:
  US05/380,310
• Time in Patent Office: 853 Days
• Field of Search: 318/480,27R 250/229
• US Class Current: 318/480
• CPC Class Codes: A61G 7/018 Control or drive mechanisms

Abstract

A control system and circuitry in an electric motor articulated hospital bed for achieving electrical isolation between the patient'"'"''"'"'s hand control unit and the higher current motor circuitry and for protecting him against shock is disclosed wherein an optical linkage is employed using photosensitive elements (photoresistors) and low voltage lamps. For each controlled function (e.g. knee up or down) lighting of the lamps changes the resistance of the photoresistor to cause a solid state circuit to turn on one, but never both, of a pair of Triacs each of which is in series with a different directional coil (clockwise or counterclockwise) of a motor and the electric mains (e.g. 120v, 60 hz. a.c.). Two or more motors may be controlled from a single electrically isolated hand held unit. In one embodiment, a low voltage transformer output is switched by the patient, in another embodiment a small d.c. battery is so switched and in a third embodiment the patient controls a mechanical linkage to mask or unmask remotely located photoresistor from a light source.

Claims

1. In an adjustable motorized hospital bed of the type having articulated panels positioned by at least one reversible electric motor having forward and reverse winding coils, a solid state control system for controlling the application of a relatively high voltage a.c. mains to the winding coils to effect rotation of the motor in either clockwise or counterclockwise direction, comprising:

first and second triacs each having first and second main terminals and a gate terminal;

a first series circuit, including the forward winding coil and the first and second main terminals of said first triac, coupled across the a.c. mains;

a second series circuit, including the reverse winding coil and the first and second main terminals of said second triac, coupled across the a.c. mains;

a first voltage divider, including a first photosensitive element, coupled to the gate terminal of said first triac and normally applying to that gate terminal a voltage of an amplitude insufficient to turn said first triac ON and render it conductive;

a second voltage divider, including a second photosensitive element, coupled to the gate terminal of said second triac and normally applying to that gate terminal a voltage of an amplitude insufficient to turn said second triac ON and render it conductive;

first and second light emitters each of which is optically coupled to, but electrically isolated from, a respective one of said first and second photosensitive elements;

a source of relatively low voltage;

a hand-held, patient operated control unit having first and second manually actuated switches each of which, when actuated, couples said low voltage source to a respective one of said light emitters to effect illumination thereof, the resistance of said first photosensitive element decreasing in response to the illumination of said first light emitter to effect an increase in the voltage applied to the gate terminal of said first triac thereby turning the first triac ON and coupling the high voltage a.c. mains to the forward winding coil to cause the motor to rotate in the clockwise direction, the resistancE of said second photosensitive element decreasing in response to the illumination of said second light emitter to effect an increase in the voltage applied to the gate terminal of said second triac thereby turning the second triac ON and coupling the high voltlage a.c. mains to the reverse winding coil to cause the motor to rotate in the counterclockwise direction;

means, operable when said first photosensitive element is activated by light from said first light emitter, for preventing said second triac from conducting; and

means, operable when said second photosensitive element is activated by light from said second light emitter, for preventing said first triac from conducting.