Some embodiments are directed to a positive displacement pump comprising: a pipe having a first end secured to a transmission area and a second end ending in a cylinder secured to a discharge area, the pipe comprising a suction opening and the discharge area comprising a discharge opening, a drive shaft with one end situated at the cylinder, a piston pressed against the cylinder by elastic means so as to prevent fluid from moving between the pipe and the discharge area, in which the pump further comprises means for moving the piston elastically away from the cylinder and keeping it at a predetermined distance from same. Some other embodiments are directed to a method for cleaning this pump.

A compressor 12 for use in a refrigerant circuit 11 using a refrigerating machine oil 60 being free of phosphoric ester and a refrigerant mixture inclusive of 1,1,2-trifluoroetylene includes a rolling piston 32 and a vane 33 in contact with the rolling piston 32 in a slidable manner. The rolling piston 32 and the vane 33 are formed of a base metal, the base metal being steel, and the base metal is exposed at a contact portion between the rolling piston 32 and the vane 33.

A roots rotor for removing dust coagulum and droplets comprises a rotor body, which rotates inside the roots pump case. Both ends of the rotor body are sealing surfaces, which are meshed with the inner wall of the roots pump case. The rotor slot scraping cavities are arranged on both sides of the sealing surface. The side of the rotor slot scraping cavity close to the sealing surface is set as the scraper surface, which forms a sharp edge with the sealing surface. A guide surface is arranged on the surface of the rotor body, and the guide surface is located on the side of the rotor slot scraping cavity away from the sealing surface. The utility model overcomes the disadvantages of the prior art, and the attachment can be scraped off and gathered into the rotor slot scraping groove through the action of the scraper surface; and with the rotation of the rotor body, the particles and dust can be easily dropped outside the exhaust port of the pump; thus to achieve to avoid the accumulation of dust, coagulum and other incompressible medium in the process gas on the wall of the pump case.

Some embodiments are directed to a positive displacement pump comprising: a pipe having a first end secured to a transmission area and a second end ending in a cylinder secured to a discharge area, the pipe comprising a suction opening and the discharge area comprising a discharge opening, a drive shaft with one end situated at the cylinder, a piston pressed against the cylinder by elastic means so as to prevent fluid from moving between the pipe and the discharge area, in which the pump further comprises means for moving the piston elastically away from the cylinder and keeping it at a predetermined distance from same. Some other embodiments are directed to a method for cleaning this pump.

A refrigerant compressor for air-conditioning systems and to a method for operating a refrigerant compressor, is based on the object of specifying a solution with which safe functioning of a refrigerant compressor is achieved and in which the effort during production of the refrigerant compressor and the costs are reduced.

A compressor 12 for use in a refrigerant circuit 11 using a refrigerating machine oil 60 being free of phosphoric ester and a refrigerant mixture inclusive of 1,1,2-trifluoroetylene includes a rolling piston 32 and a vane 33 in contact with the rolling piston 32 in a slidable manner. The rolling piston 32 and the vane 33 are formed of a base metal, the base metal being steel, and the base metal is exposed at a contact portion between the rolling piston 32 and the vane 33.

The filter device is applied to a small-size air compressor. The filter device includes a base member and a cover member. The base member has a back side and a front side. The back side is for sealing and connecting to a rear end of a driving motor of the air compressor. The front side is provided with a housing space surrounded with a side wall. The base member has multiple exhaust holes, allowing the housing space communicate with the driving motor's interior. At least one filtering material is placed inside the housing space. The cover member is joined to the base member to seal the housing space. The cover member is provided multiple air intake grooves. When the air compressor starts, external air is forcibly drawn through the air intake grooves, the at least one filtering material, and the exhaust holes into the driving motor.

The filter device is applied to a small-size air compressor. The filter device includes a base member and a cover member. The base member has a back side and a front side. The back side is for sealing and connecting to a rear end of a driving motor of the air compressor. The front side is provided with a housing space surrounded with a side wall. The base member has multiple exhaust holes, allowing the housing space communicate with the driving motor's interior. At least one filtering material is placed inside the housing space. The cover member is joined to the base member to seal the housing space. The cover member is provided multiple air intake grooves. When the air compressor starts, external air is forcibly drawn through the air intake grooves, the at least one filtering material, and the exhaust holes into the driving motor.

A refrigerant compressor for air-conditioning systems and to a method for operating a refrigerant compressor, is based on the object of specifying a solution with which safe functioning of a refrigerant compressor is achieved and in which the effort during production of the refrigerant compressor and the costs are reduced.