Rotary piston compressor with an axial direction of delivery

Details Rotary piston compressor with an axial direction of delivery Rotary piston compressor with an axial direction of delivery

2000-06-09

2001-12-11

Koczo, Michael (Department: 3746)

Pumps

Motor driven

Interrelated or common lubricating or cooling means for pump...

C417S410400, C418S083000

Reexamination Certificate

active

06328540

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to a rotary piston compressor with an axial direction of delivery from the top downwards, in particular of screw spindle-type construction, with cooling ducts for the motors, bearings and sensors, through which ducts a cooling fluid flows, and with a cooling device for the pump space.
A known rotary piston compressor (DE 19522559 A1) of this kind has two screw spindles which intermesh and are driven synchronously by motors. Here, the angles of rotation and speeds of rotation of the two screw spindles or rotors are detected by sensors. The motors are synchronized electronically by means of the signals of these sensors. In the case of such rotary piston compressors, there is, on the one hand, the need to cool the motors, bearings and sensors, and they should be cooled to as low temperatures as possible, e.g. 20° C., although, of course, they should not be cooled down to such an extent that condensation forms. The pump space, which is heated up due to the compression of the medium delivered, must likewise be cooled. However, the pump space must be cooled to a higher temperature of, for example, 60° C. to avoid the pumped medium condensing.
In the case of the known rotary piston compressor, the motors, bearings and sensors are cooled by a cooling fluid which flows through cooling ducts. Although the pump space is cooled primarily by internal cooling of the screw spindles, provision has also been made in one embodiment for the casing of the pump space to be cooled. However, the corresponding cooling fluid must be at a higher temperature than the cooling fluid for the motors, bearings and sensors, making it necessary to have two separate cooling circuits. If the rotary piston compressor is to be serviced or repaired, two cooling circuits have to be divided and emptied. The cooling system is therefore complex and requires a considerable amount of work when disassembling the rotary piston compressor.
SUMMARY OF THE INVENTION
The object of the invention is to provide a rotary piston compressor by means of which it is possible in a particularly simple manner to cool the motors, bearings and sensors to a relatively low temperature and to cool the pump space to a considerably higher temperature, with the pump space at the same time being cooled to a greater extent on the delivery side than on the intake side.
The fact that the delivery side should be cooled to a greater extent than the intake side is likewise known from the prior art. According to the invention, the solution to the object, including this secondary problem, is achieved by virtue of the fact that the casing of the pump space has a closed annular space which is partially filled with a liquid, which is cooled by the cooling fluid via heat exchanger surfaces.
The pump space is thus cooled by a liquid which is contained within a closed annular space. In an advantageous embodiment, this annular space extends over the entire height of the casing of the pump space. The liquid contained in it is cooled by the cooling fluid for the motors, bearings and sensors. In this context, the rate of flow and size of the heat exchanger surfaces can be selected so that, although the motors, bearings and sensors are cooled to approximately 20° C., the casing of the pump space is cooled to a temperature of approximately 60° C. Since the annular space is only partially filled with liquid, cooling is less effective at the top, i.e. the intake zone, in line with the fact that there should be less cooling here. Moreover, since the annular space is only partially filled with liquid, this liquid can expand as it heats up. The liquid in the annular space does not have to be drained off when the casing is disassembled but remains in it. All that is required is to divide the circuit for the cooling fluid for the motors, bearings and sensors and, where appropriate, partially drain it.
In an embodiment which is particularly expedient and simple to produce, the annular space has a cooling coil through which cooling fluid flows.
It is expedient if the liquid in the annular space is a water/glycol mixture, which allows effective cooling but is not subject to the risk of freezing when the pump is unused at low temperatures.
It is expedient to use cooling water as the cooling fluid.
It is expedient here to make provision for the cooling fluid to flow through the cooling ducts for the motors, bearings and sensors first and then to flow through the cooling coil.
It is advantageous if the cooling ducts and the annular space are closed off, i.e. are not connected to the pump space, eliminating the need for a seal—with the familiar problems associated with it—which would otherwise be necessary.


REFERENCES:
patent: 3478689 (1969-11-01), Ball
patent: 4767284 (1988-08-01), Shiinoki et al.
patent: 5222874 (1993-06-01), Unnewehr et al.
patent: 5904473 (1999-05-01), Dahmlos et al.
patent: 195 22 559 A 1 (1997-01-01), None
patent: 197 45 616 A 1 (1999-04-01), None

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