A screw compressor includes an outlet housing. The outlet housing includes a passage that is configured to communicate compressed fluid from a screw rotor to a discharge. A removable cover plate is configured to cover a portion of the passage. A method of varying a volume index for a screw compressor is also disclosed.

A screw compressor includes an outlet housing. The outlet housing includes a passage that is configured to communicate compressed fluid from a screw rotor to a discharge. A removable cover plate is configured to cover a portion of the passage. A method of varying a volume index for a screw compressor is also disclosed.

The invention relates to an assembly comprising a vacuum pump and a chamber, wherein a suction tract extends between the chamber and the vacuum pump. The vacuum pump is a liquid ring machine. According to the invention, a liquid outlet is arranged in the suction tract in order to add liquid to gas sucked in from the chamber. The invention further relates to a method for evacuating a chamber filled with vapor. According to the invention, the vapor is condensed by introducing additional liquid into the suction tract, thus by co-condensation. By supplying liquid selectively only when liquid is required for the condensation of the vapor, water is saved.

A scroll compressor with a first valve having a first surface to open/close between a first path and a second path; a back pressure chamber assembly or non-orbiting scroll having a third path through which a first pressure refrigerant flows, a fourth path through which refrigerant of a second pressure lower than the first pressure flows, and one end in communication with the third and fourth paths and the other end having a fifth path in communication with a second surface of the first valve; and a second valve provided where the third, fourth, and fifth paths to meet and moveable between first and second positions, wherein at the first position the third and fifth paths communicate to supply the first pressure refrigerant toward the second surface, and at the second position the fourth and fifth paths communicate to supply the second pressure refrigerant toward the second surface.

A claw pump includes: a housing; two rotating shafts which are disposed parallel; a pair of rotors respectively fixed to the two rotating shafts; a rotary drive device driving the pair of rotors; and a suction port and discharge ports formed in a partition wall of the housing. The discharge ports are constituted by a first discharge port and a second discharge port. The first discharge port is formed at a position that communicates with an initial stage compression space formed at an initial stage of a compression stroke in a compression space that is formed by joining a first pocket and a second pocket. The claw pump includes an opening/closing mechanism which opens the first discharge port when a pressure of the initial stage compression space reaches a threshold and closes the first discharge port when the pressure does not reach the threshold.

A scroll compressor is provided that may include a casing including a rotational shaft, a cover fixed inside of the casing to partition the inside of the casing into a suction space and a discharge space, a first scroll that is revolved by rotational of the rotational shaft, a second scroll disposed on or at a side of the first scroll to define a plurality of compression chambers together with the first scroll, the second scroll having an intermediate pressure discharge hole that communicates with a compression chamber having an intermediate pressure of the plurality of compression chambers, a back pressure plate coupled to the second scroll, the back pressure plate having an intermediate pressure suction hole that communicates with the intermediate pressure discharge hole, and a floating plate movably disposed on or at a side of the back pressure plate to define the back pressure chamber together with the back pressure plate. The discharge space may have a volume greater by a set ratio or more than a volume of the back pressure chamber.

A scroll compressor is provided that may include a casing including a rotational shaft, a cover fixed inside of the casing to partition the inside of the casing into a suction space and a discharge space, a first scroll that is revolved by rotational of the rotational shaft, a second scroll disposed on or at a side of the first scroll to define a plurality of compression chambers together with the first scroll, the second scroll having an intermediate pressure discharge hole that communicates with a compression chamber having an intermediate pressure of the plurality of compression chambers, a back pressure plate coupled to the second scroll, the back pressure plate having an intermediate pressure suction hole that communicates with the intermediate pressure discharge hole, and a floating plate movably disposed on or at a side of the back pressure plate to define the back pressure chamber together with the back pressure plate. The discharge space may have a volume greater by a set ratio or more than a volume of the back pressure chamber.

A compressor may include first and second scrolls and a capacity modulation assembly. The capacity modulation assembly may include a valve ring and a modulation control valve. The valve ring is movable relative to the first scroll between a first position corresponding to a first capacity mode and a second position corresponding to a second capacity mode. The modulation control valve includes a valve body and a valve member that is movable relative to the valve body to cause corresponding movement of the valve ring. The valve body includes a cavity in which the valve member is movably disposed. The valve body includes passages in fluid communication with the cavity. A first pressure differential between fluid in one of the passages and fluid in another of the passages causes movement of the valve member to cause corresponding movement of the valve ring between the first and second positions.

Provided is a horizontal step scroll compressor with which liquid compression can be effectively prevented even when starting up from a liquid migration state in which liquid refrigerant has migrated into the compressor while operation of the compressor is stopped. In this horizontal step scroll compressor, bypass ports, which divert pressure into a discharge chamber when the pressure in a pair of compression chambers reaches or exceeds a set pressure at an intermediate compression position between a suction cutoff position and the position communicating with a discharge port, are provided along the spiral direction of spiral wraps. Among these bypass ports, the opening area of the bypass ports that open into the first compression chamber, which includes the step parts in the gravity direction when a step part and a step part, and a step part and a step part, begin to engage each other, is greater than the opening area of the bypass port, which opens to the second compression chamber forming a pair with the first compression chamber.

The invention provides a pump comprising a pump inlet, a pump outlet, at least two threaded rotors and a pressure controlled valve, the pressure controlled valve being capable of controlling re-circulation of fluid from the pump outlet to the pump inlet. The pressure controlled valve can be a control valve. The invention also provides a multiple stage pump assembly comprising at least two pumps arranged in series, wherein at least one of the pumps is the aforementioned pump.