Abstract: Protective apparatus in a scroll compressor, in the form of a valve assembly, is operative to prevent compressor damage from reverse direction rotation of the scroll compression mechanism or the development of abnormally high discharge gas temperatures. The valve assembly is disposed in a passage communicating between the suction and discharge pressure portions of the compressor shell and houses a discharge temperature sensor immediately adjacent the location from which discharge gas issues from the compression mechanism. The location of the sensor and its exposure to discharge gas permits the timely sensing of abnormally high discharge temperatures and the shutdown of the compressor upon their occurrence.

Abstract: In a compressor system, surge detection is provided by sensing the current of the motor driving the compressor and reading oscillations of the current about the average thereof and above and below two opposite threshold levels from such average current and counting the polarity changes within a time interval containing so many samples of the current and defining a sliding window.

Abstract: A compressed air supply system including an electric motor for driving an air compressor. An air reservoir connected to an outlet of the air compressor via a cooler. A dryer and a check valve, a pressure sensor coupled to the air reservoir for sensing the pressure therein. An unloading valve coupled to the outlet of the air compressor. A control circuit coupled to the electric motor and the unloading valve. A protective circuit coupled to the control circuit and the unloading valve for preventing the motor from starting under an overload condition and for averting the unnecessary running of the motor and driving of the air compressor.

Abstract: Single shaft, air breathing auxiliary power units having a single stage centrifugal load compressor driven by a gas turbine engine. The latter has a single stage centrifugal compressor and a single stage radial inflow turbine mounted in back-to-back relationship on the same shaft as the load compressor. Control systems for these auxiliary power units feature turbine exhaust gas temperature and turbine speed responsive fuel flow control; a bypass valve control which causes air to be dumped overboard when the pneumatic load demand drops to prevent load compressor surge; and an inlet guide vane control.

Abstract: In a motor driven centrifugal compressor having a diffuser containing a movable wall for varying the width of the diffuser passage, control equipment is provided for continually changing the wall position in response to changes in motor current.

Abstract: An axial flow helical screw type compressor has a slide valve member and slide stop member mounted end to end beneath the intermeshing rotors such that the slide valve member controls communication between the work chamber defined by the rotors and the casing to the outlet port and the slide stop member and the valve member together control the working fluid inlet to the bores of the rotors, the slide valve member and the slide stop being independently movable. Control means for the slide valve member and slide stop include position sensing means for these two members, inlet and outlet pressure sensing means, and means for feeding these inputs into programmable circuitry to control the positions of the slide member and slide stop.

Abstract: A method and apparatus for effecting capacity control of a compressor are described. The electric current to the compressor motor driving a variable step compressor is monitored. The subsequent operating current of the compressor is monitored and compared to the initial reference current value. Upon a predetermined variance between the reference current value and the current operating value being detected the capacity step of the compressor is increased to meet the additional load. Additionally there is provided other means for increasing the capacity step of the compressor including determining that an additional load on the refrigeration circuit has been energized and that the unit has been operating at a particular capacity step for a predetermined delay period. Means are disclosed for altering the capacity step of the compressor in response to any of the above occurrences indicating a need to increase the capacity step of the compressor.

Abstract: A bypass control system and method monitors and controls the amount of air recirculated through a bypass duct from the air supply outlet supplied by a fan and motor from a single zone HVAC unit to the air intake thereof, a stepper motor driven bypass damper is located in the bypass duct having a damper blade movable between opened and closed positions and intermediate positions therebetween, and a bypass monitor is connected to the bypass damper for controlling the operation of the stepper motor of the bypass damper.

Abstract: An electronic control system for sequential actuation of a four-way solenoid valve is used to selectively load and unload a slide valve control for a screw compressor. The electronic control system can be responsive to output or refrigerant pressure or evaporator pressure or inlet pressure and pulses a four-way solenoid valve to selectively load and unload the compressor so that it will maintain system pressure within a preselected deadband. Selective pulsing of the four-way solenoid valve is used to gate hydraulic fluid to load and unload chambers separated by a piston coupled to a slide valve which shifts longitudinally and changes the capacity of the screw compressor. The control system senses system pressure (reflecting load), and when a limit pressure is reached, a gas bypass solenoid valve (or dump valve) and fast-unload system is actuated to entirely unload the compressor. The control circuit also monitors current to the motor which drives the screw compressor.

Abstract: A rotary compressor has an outlet port with a variable area for discharging compressed medium from a working chamber to the outlet. The degree of opening of the outlet port is controlled by a regulator which senses the energy supplied to the compressor for compressing the medium and which from time to time changes the degree of opening of the outlet port until the need of drive energy for the compressor becomes minimal.

Abstract: An electronic control system for pressure and flow control of variable displacement pumps consists of a closed loop system of operational amplifiers which provide continuous control of the volume modifying element in the pump. In a variable displacement vane pump application a command flow control signal and a feedback signal representative of the position of the adjustable cam ring in the pump are applied to an integrating amplifier to develop a signal for application to an electro-hydraulic valve in the pressure compensating portion of the pump. A command pressure signal is compared with the control signal to limit the latter to a level, thereby providing pressure control for the pump. Slip compensation is effected in the control system by utilizing a portion of the control signal to provide proportional modification of the command signal.

Abstract: An electronic control system for sequential actuation of a four-way solenoid valve is used to selectively load and unload a slide valve control for a screw compressor. The electronic control system is responsive to output air pressure and pulses a four-way solenoid valve to selectively load and unload the system so that it will maintain system pressure within a preselected deadband. Selective pulsing of the four-way solenoid valve is used to gate hydraulic fluid to load and unload chambers separated by a piston coupled to a slide valve which shifts longitudinally and changes the capacity of the screw compressor. The control system senses output line pressure, and when a limit pressure is exceeded, a dump solenoid valve and fast-unload system is actuated to entirely unload the system of air pressure until reduced to a level below the set deadband. The control circuit also monitors current to the motor which drives the screw compressor.

Abstract: Gas is circulated within the chamber of a heat treating furnace by a fan which is driven by an electric motor. The current drawn by the motor is detected and, when the current exceeds a predetermined magnitude, the density of the gas in the chamber is reduced to prevent an excessive load from being imposed on the motor. The density of the gas is reduced by shutting off the flow of gas to the chamber and by exhausting gas from the chamber.

Abstract: A variable capacity rotary screw compressor driven by an electric motor and having an adjustable slide valve for varying compressor capacity is provided with a control system for adjusting the slide valve to regulate compressor capacity and thereby maintain a variable system condition, such as gas inlet or outlet pressure or temperature, within a predetermined range. The control system comprises first means including a current transformer for sensing changes in motor current as compressor capacity varies and a current converter connected to the current transformer for providing a first electrical signal proportional to compressor capacity. The control system also comprises means for sensing changes in the particular system condition being monitored and for providing a second electrical signal proportional thereto.

Abstract: This hydraulic engine utilizes two sets of hydraulic cylinders connected to a shaft so as to be alternately pressurized as the shaft is reciprocally driven by a pair of conventional internal combustion chambers. The outlets of all hydraulic cylinders are connected to a common output line via valves. During each power stroke certain of the hydraulic cylinders being pressurized are selectively disconnected (depressurized) from the output line. This effectively decreases the load on the driving chamber, and insures a relatively constant, high pressure hydraulic fluid output level despite changes in supplied force during each power stroke. The selective cylinder disconnection may be implemented programmatically in response to changes in engine parameters such as combustion chamber pressure. The engine also includes a pump for supplying input hydraulic fluid to each set of cylinders while that set is not being pressurized. The input fluid force is additive to the power supplied by the operative combustion chamber.

Abstract: In an exhaust system for removing smoke and pollutant fumes from the area surrounding the discharge of coke from a coke oven in which air, solids, and gaseous pollutants are moved through an exhaust manifold gated at its inlets, through treating apparatus for removing contaminants from the air, with the cleaned air subsequently discharged to the atmosphere, a method and means are provided for maintaining continuous induced draft within the exhaust system. A means for inducing exhaust flow operates continuously between a minimum flow and maximum capacity depending on whether the inlet gates of the exhaust manifold are closed or open, respectively. A flow control damper located at the suction of the means for inducing exhaust flow is controlled to permit the flow inducing means to operate in accordance with its performance curve up to drawing a predetermined maximum amperage.