Motor-driven control device for a valve-actuating spindle

A valve having a case, a closure member within the case and a spindle rotatable relative to the case about an axis for shifting the closure member between valve opening and valve closing positions, a control device for rotating the spindle and comprising an electric motor having a stator and a rotor, means for connecting the rotor to the spindle to rotate the spindle, an electric power supply circuit electrically connected to the motor, means for detecting stoppage of the rotation of the spindle, switching means inserted in said circuit and responsive to the detecting means for opening the supply circuit when the spindle stops rotating, the detecting means comprising a detecting element mounted to be movable with respect to said case transversely of a radial plane containing said axis in a given direction between a first position and a second position, the detecting element being cooperative with the switching means to achieve opening of the supply circuit in said first position and closure of the supply circuit in said second position, and force transmitting means interposed between the spindle and the detecting element for urging the detecting element to said second position while the spindle is being driven in rotation by the motor, abutment means fixed relative to said case, elastically yieldable means interposed between said abutment means and said detecting element for elastically biasing the detecting element to said first position, the electric motor being a variable inductance motor and said means connecting the rotor to the spindle being operative to prevent rotation of the rotor when the spindle is prevented from rotating, said force transmitting means being capable of exerting sufficient force on the detecting element to overcome the action of the elastically yieldable means and shift the detecting element to said second position when the spindle is rotated to actuate the valve in a given direction and capable of allowing the detecting element to return to said first position under the combined actions of the elastically yieldable means and the vibrations of the electric motor when the spindle is prevented from rotating the current is continued to be supplied to the electric motor.

In a control device for shifting a closure member of a valve, comprising a case, a spindle rotatably mounted in the case to rotate about an axis for connection to the closure member, an electric motor having a stator and a rotor, means for connecting the rotor to the spindle to rotate the spindle, an electric power supply circuit electrically connected to the motor, means for detecting stoppage of the rotation of the spindle, switching means inserted in said circuit and responsive to the detecting means for opening the supply circuit when the spindle stops rotating, the detecting means comprising a detecting element mounted to be movable with respect to said case transversely of a radial plane containing said axis in a given direction between a first position and a second position, the detecting element being cooperative with the switching means to achieve opening of the supply circuit in said first position and closure of the supply circuit in said second position, and force transmitting means interposed between the spindle and the detecting element for urging the detecting element to said second position while the spindle is being driven in rotation by the motor;

• the improvement comprising in combination abutment means fixed relative to said case, elastically yieldable means interposed between said abutment means and said detecting element for elastically biasing the detecting element to said first position, said electric motor being a variable reluctance motor and said means connecting the rotor to the spindle being means fixing the spindle to the rotor to rotate with the rotor, said force transmitting means being a friction drive means capable of exerting sufficient force on the detecting element to overcome the action of the elastically yieldable means and shift the detecting element to said second position when the spindle is rotated to actuate the valve in a given direction and capable of allowing the detecting element to return to said first position under the combined actions of the elastically yieldable means and the vibrations of the electric motor when the spindle is prevented from rotating and current is continued to be supplied to the electric motor.