Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C27/00—Sealing arrangements in rotary-piston pumps specially adapted for elastic fluids
  • F04C27/008—Sealing arrangements in rotary-piston pumps specially adapted for elastic fluids for other than working fluid, i.e. the sealing arrangements are not between working chambers of the machine
  • F04C27/009—Shaft sealings specially adapted for pumps

Definitions

• the present invention relates to a rotary screw compressor of the kind specified in the preamble of claim 1.
• US-A 3 913 346 discloses a refrigeration compressor of the twin-screw type, in which the drive motor is internally cooled by liquid refrigerant of delivery pressure supplied from the condenser, and the liquid and evaporated gas is then drained to a closed working chamber in the compressor working space.
• the loss in compressor efficiency which is entailed with that system can be avoided by providing a pump for raising the pressure of the liquid before entering the motor space, so that the liquid-gas-mixture leaving the motor can be drained directly to the delivery line of the compressor.
• US-A 4 669 279 discloses such a system in connection with a centrifugal compressor.
• the object of the present invention is to attain a compressor with a seal between the low pressure end of the compressor working space and a high pressure cavity at the other side of the low pressure end wall, which seal should be effective as well as economical in operation.
• a compressor of the kind in question has the features specified in the characterizing portion of claim 1.
• Fig. 1 is a schematic illustration of a refrigeration system with a compressor according to the invention.
• Fig. 2 is a section through the seal means in the low pressure end section of the compressor in fig. 1.
• the refrigeration system in fig. 1 has a hermetic compressor-motor unit with a twin-screw rotary compressor 1, the low pressure end of which is connected to an electric motor 2. At the high pressure end of the compressor an oil separator 3 is provided for separating oil from the working fluid, which oil has been injected into the compressor working space for sealing, cooling and lubricating purposes.
• the refrigeration system is of conventional type including a condenser 4, an expansion valve 6 and an evaporator 5 connected by pipes, 8, 9, 10 to form a closed refrigeration circuit. Liquid refrigerant is supplied from the condenser 4 through a pipe 11 to the motor 2 for cooling the motor windings 18. In the pipe 11 a pump 7 is provided for raising the pressure to a level about 1 to 2 bars above delivery pressure.
• the liquid refrigerant When cooling the motor windings 18 the liquid refrigerant will partly be evaporated, and the gas-liquid mixture is drained to the discharge line of the compressor. In the illustrated embodiment the gas- liquid mixture is drained to the oil separator 3 where the remaining liquid is evaporated for cooling the oil.
• One of the rotors 13 of the compressor is directly driven by the motor 2 through a shaft 14 extending through the low pressure end section 15 of the compressor.
• roller bearings 16 and a seal arrangement 17 for sealing between the low pressure end of the compressor, where the pressure is about evaporating or suction pressure and the motor space where the pressure is 1 to 2 bars above condensing or delivery pressure.
• the seal arrangement is illustrated in fig. 2 in an enlarged section.
• the shaft 14, including a shaft sleeve 21, is extending through the low pressure end section 15 of the compressor and is at its left end connected to the motor 2 and at its right end to one of the compressor rotors 13.
• the seal arrangement 17 is on its left side exposed to a cavity communicating with the motor space and thus having a pressure above delivery pressure and on its right side to a cavity communicating with the low pressure end of the compressor working space and thus having a pressure corresponding to the compressor inlet pressure.
• a lip seal 20 Adjacent to the high pressure cavity a lip seal 20 is provided and adjacent to the low pressure cavity there is a non-contacting seal 24.
• An intermediate chamber 22 is formed between these two seals 20, 24, to which chamber oil of about delivery pressure is supplied through a nozzle 23, connected by a supply channel 28 to a source of oil under pressure, normally the oil separator of the compressor.
• the sealing is accomplished by a non-contacting seal 24, allowing the supplied oil to leak from the intermediate chamber 22 through the seal gap 27 to the compressor working space.
• the non-contacting seal can be of any kind, e.g. a labyrinth seal
• the preferred embodiment shown in the figure employs a so called floating seal of the type disclosed in US-A 5 009 583.
• the seal gap 27 can be as small as desired, since the seal body 24 is radially movable while being axially kept in a fixed position by the supports 25, 26 on either side.
• the seal body 24 is squeezed between these supports 25, 26 with a force large enough to prevent rotation but low enough to allow the seal body 24 to move radially.
• the seal body 24 thus is self-centering around the sleeve 21 of the shaft 14.
• the blocking oil leaking from the intermediate chamber 22 to the compressor working space passes the roller bearings 16 supporting the shaft and is used to lubricate these.
• the seal gap 27 therefore must be dimensioned so that the leakage is sufficient for that lubrication requirement.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Applications Or Details Of Rotary Compressors (AREA)
• Compressor (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20389942

Family Applications (1)

Country Status (5)

Cited By (9)

Citations (3)

• 1993
  • 1993-05-14 SE SE9301662A patent/SE9301662L/sv unknown
• 1994
  • 1994-02-04 WO PCT/SE1994/000087 patent/WO1994027050A1/en active IP Right Grant
  • 1994-02-04 DK DK94910075T patent/DK0698185T3/da active
  • 1994-02-04 EP EP94910075A patent/EP0698185B1/en not_active Expired - Lifetime
  • 1994-02-04 DE DE69406134T patent/DE69406134T2/de not_active Expired - Fee Related

Patent Citations (3)

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