Pumps – Expansible chamber type – Moving cylinder
Patent
1990-03-30
1991-12-31
Bertsch, Richard A.
Pumps
Expansible chamber type
Moving cylinder
418164, F04B 1902
Patent
active
050767682
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a rotary piston compressor.
In rotary piston compressors of this kind using meshing lobes there is a rotatory speed ratio of n.sub.1 =n.sub.2 +1 between the inner rotor and the otuer rotor, i.e., the inner rotor rotates faster than the outer rotor in a ratio of 2:1, 3:2, 4:3 etc. In a rotary piston machine with the rotatory speed rati of n.sub.1 :n.sub.2 =2:1, which is especially suitable as a compressor on account of its low harmful capacity, each of the two working chambers performs one suction cycle and one discharge cycle with each full rotation of the outer rotor.
In known rotary piston machines of this kind (U.S. Pat. No. 883,271, European Paten A 0087 748) the shaft of the inner rotor is brought out and fastened to a drive pulley and in turn drives the outer rotor through the gear transmission at a rotatory speed of n.sub.2 =n1/2. For high output capacities this requires high driving speeds, since for each rotation of the inner rotor only half o the full period is executed.
It is the object of the invention to createa r toary piston compressore which will be characterized by a high output at low driving speeds.
This object is achieved.
In the rotary piston compressor according to the invention, due to the circumstance that it is not the inner rotor but the outer rotor that is driven, with each revolution of the driven shaft the full period is executed in each working chamber, so that the proposed rotary piston compressor, at a rotatory speed ratio of n.sub.1 :n.sub.2 =2:1, produced at a given drive speed twice the pumping volume of a compressor according to the state of the art.
The proposed rotary piston compressor furthermore has important advantages over the state of the art as regards teh journaling of the outer rotor. In the known rotary piston machines, in which the inner rotor is driven, the bearings of the outer rotor must have a large diameter, since the shaft of the inner rotor, which is off-center from the axis of rotation of the outer rotor, extends to the exterior. Bearings of great diameter, however, are expensive and at high rotatory speeds they are subjected to heavy stress. To reduce this stress, in the embodiment of the above-mentioned European Paten A 0087 746 the outer rotor is not journaled in a large bearing but on three symmetrically disposed rollers. This solves the problem of the high peripheral speed of the large bearing, but at the cost of a complex design.
In the proposal of the invention, however, the outer rotor with is side walls can be journaled axially outside of the bearings of the inner rotor; the diameter of these bearings can be relatively small since the shaft of the inner rotor terminates axially inside of these bearings.
Because it is the shaft of the outer rotor that is driven in the proposed rotary piston compressor, the shaft of the inner rotor is not subjected to any flexing by the pull of the drive belt. Therefore this compressor is especially suitable for dry running. Dry-running compressors are used when lubricant-free compressed air is needed. No lubricant must enter into the working chambers, and this requires that no seals can be provided which have to be lubricated. Accordingly, such compressors must be manufactured with leak-resistant clearances of the order of 50 to 100 microns. The maintenance of such tight clearances is facilitated in the rotary piston compressor of the invention by keeping the drive stresses away from the inner rotor shaft. The inner rotor is exposed to great centrifugal forces in operation, since it rotates at twice the speed in the 2:1 machine. To combat this stress from centrifugal forces the inner rotor can be made hollow and from light metal, and can be provided with at least one balancing weight of a material of greater specific weight extending substantially over its entire length. Thus a complete balance of masses is achieved in every transverse plane of the inner rotor, so that no bending moments are exerted on the inner rotor or its shaft. The mass balance can be achieved by one or more heavy
REFERENCES:
patent: 1887884 (1932-11-01), Eyston
patent: 3012550 (1961-12-01), Paschke
patent: 3311094 (1967-03-01), Kehl
patent: 4723895 (1988-02-01), Hayase
patent: 4915596 (1990-04-01), McCall
Bierling Rudolf
Ruf Renate
Bertsch Richard A.
Kocharov Michael I.
Ruf Renate
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