Abstract: A temperature control system for monitoring and controlling a zone supplied with low pressure steam is disclosed. The system comprises a series of balanced Wheatstone bridges which, when calibrated, provide a variety of manual and automatic control conditions to maintain the temperature in the zone. Means are provided for obtaining direct readings of room or zone temperature, and monitoring the position and movement of a steam control valve which is utilized as the heat metering apparatus. In order to compensate for environmental differences which may exist in various zones under control, there is disclosed apparatus for selectively varying the effect of sensors utilized in the system, and in particular, the effect of a resistance thermometer located within the zone which may be subject to variations in accuracy in terms of placement.

Abstract: An air motor, responsive to change in pressure of a compressed air supply line acts to control the flow of hydraulic motive fluid to a hydraulic motor which drives the capacity control slide valve of a helical screw, rotary compressor feeding the supply line. To eliminate hunting of the slide valve which shifts in response to change in compressor load, a mechanical feedback from the hydraulic motor modulates the flow of motive fluid to the hydraulic motor.

Abstract: A helical screw rotary compressor is provided with oppositely oriented slide valves at the suction and discharge sides of the machine to control compressor capacity and balance the closed thread pressure at discharge with discharge line pressure in a main closed loop heat pump refrigeration system. The compressor may be bidirectional if the function of the slide valves is reversed. Additional slide valves carried by the compressor may be employed to vary the injection point of intermediate pressure refrigerant gas to a compressor closed thread and to control flow to and/or from closed threads and a secondary loop for subcooling the main loop refrigerant or for other functions.

Abstract: Excess refrigerant is collected within a refrigerant pot surrounding a portion of the return conduit connecting the outdoor coil operating as an evaporator during a heat pump heating cycle to the compressor creating a reduced pressure temperature relationship within the pot cavity causing the migration of liquid refrigerant through a small diameter tube connecting the pot to the liquid line leading from the indoor coil to the outdoor coil at a point upstream of the outdoor coil expansion valve.

Abstract: Complementary semi-tubular metal bars of non-porous metal are extruded to form bar stocks of given length, complementary edges of the semi-tubular metal bars are clamped in edge abutment, a series of longitudinally spaced holes are drilled along respective edges through one of said bars and partially through the other, the holes partially drilled through the edges of the second bar are tapped and the bars are screwed together prior to severing individual connecting rods from the joined bars at points intermediate of the screws.

Abstract: A T-shaped pipe whose base extends through a sidewall of a steam trap housing terminates internally of the housing in open ended upper and lower vertical arms. The lower arm is closed off by an axially movable valve disc mounted to a valve actuator rod extending axially through the arms and coupled at its upper end to a pressure balancing plate sealably connected at its periphery by a non-ferrous metal bellows to the upper end of the T-pipe arm. A float ball fixed to a float arm is pivotably coupled at the opposite end of the arm to the valve actuator rod and to the T-pipe with the pressure on balancing plate balancing the pressures acting on the movable valve disc.

Abstract: An axially shiftable slide valve member in a rotary, helical screw compressor carries a port which senses the pressure of the working fluid in the trapped volume just before uncovering of the closed thread to the discharge port and compares that pressure with the line pressure at the discharge port and shifts the slide valve member to balance the pressures and prevent overcompression or undercompression of the compressor. The screw compressor may be provided with two identical but oppositely oriented slide valve members on opposite sides of the intermeshed helical screws with one slide valve member controlling the capacity of the compressor and the other balancing the closed thread pressure at discharge with discharge line pressure. Compressor rotation may be reversed to eliminate the need for a reversing valve where the compressor operates in heat pump or reverse flow defrost refrigeration applications, with the two slide valves trading functions.

Abstract: An axially shiftable slide valve member in a rotary, helical screw compressor carries a port which senses the pressure of the working fluid in the trapped volume just before uncovering of the closed thread to the discharge port and compares that pressure with the line pressure at the discharge port and shifts the slide valve member to balance the pressures and prevent overcompression or undercompression of the compressor. The screw compressor may be provided with two identical but oppositely oriented slide valve members on opposite sides of the intermeshed helical screws with one slide valve member controlling the capacity of the compressor and the other balancing the closed thread pressure at discharge with discharge line pressure. Compressor rotation may be reversed to eliminate the need for a reversing valve where the compressor operates in heat pump or reverse flow defrost refrigeration applications, with the two slide valves trading functions.