Abstract: A verification system monitors the operation of a digital control system in order to insure proper operation. The verification system receives control signals and monitors these control signals to determine whether operation is proper. The digital control system is adapted for operational control of various equipment. The verification system monitors control signals received from the digital control system as well as the status of the equipment, where appropriate, in determining whether the operation of the digital control system is proper. The verification system includes various portions which monitor the control signals at various stages. If there is an error detected at one of the stages, an error signal is generated which prevents operation of the associated equipment.

Abstract: An absolute encoder monitors rotary position and senses rotary displacement relative to a measuring scale. The absolute encoder evaluates rotary displacement by providing a plurality of rotatably mounted encoder wheels, and each wheel includes at least one code sequence which in combination comprises the measuring scale. A pinion is provided between each pair of encoder wheels in order that each of the encoder wheels will be rotated upon the rotation of the shaft. Each code sequence of the encoder wheel is monitored by a sensing mechanism and this information is utilized to evaluate the shaft position. The sensing mechanism includes both light emitting and light detecting devices which monitor a defined region of each code sequence and this is evaluated in determining the rotary position.

Abstract: A repeater device in a communication network within a transmission line segment receives a distorted signal from the transmission line and retransmits a modified signal. The repeater includes a detector for activating the device in response to the input of the signal and a logic control in order for directing the signal to the modifying portion of the device. To minimize bit error which may occur as the signal is being transmitted over the network or as the signal is being received by the modifying portion of the repeater, the repeater replaces the leading bit of the signal prior to being retransmitted back to the network.

Abstract: A valve actuator differential worm planetary gear drive provides forward or reverse motion to a valve stem, from an input from either a motor-driven worm or a handwheel drive worm, by using a plurality of planet gears to send motion to the sun gear. If the preference is to have the motor drive the valve primarily, the manual worm stays locked and the motor worm acts as a planetary arm. When it is desired to move the valve by hand, the motor gear is fixed and rotation of the handwheel worm gear transmits the power through the ring gear and the planet gears to the drive sleeve.

Abstract: A two-rotor, three-position indicator for a valve actuator is connected to receive rotary input from at least two independently operating rotors connected inside the geared limit switch of a valve actuator. Individual drive lugs moved interconnected gearing to cause a pointer to indicate whether the valve stem is open, closed or in-between those two oppositely disposed limits.

Abstract: A valve actuator differential worm planetary gear drive provides forward or reverse motion to a valve stem, from an input from either a motor-driven worm or a handwheel driven worm, by using a plurality of planet gears to send motion to the sun gear. If the preference is to have the motor driven the valve primarily, the manual worm stays locked and the motor worm acts as a planetary arm. When it is desired to move the valve by hand, the motor gear is fixed and rotation of the handwheel worm gear transmits the power through the ring gear and the planet gears to the drive sleeve.

Abstract: A switch assembly for a geared limit switch for valve actuators is formed from aligned switch modules. The switch modules includes a pair of switch units, each switch unit having a plunger and a movable contact plate mounted between two springs. As the plunger is driven inward, a camming element on the plunger contacts an edge of an aperture in the movable contact plate, forcing the plate to move in a direction perpendicular to the line of plunger travel. The inward motion of the plunger and the camming action continue after the contacts have closed, wiping the contacts mounted on the movable plate across the surfaces of the stationary contacts. When the plunger is released, an outer edge of the movable plate engages a beveled inner wall of the switch unit housing, returning the movable contact plate to its original position.