Rotary expansible chamber devices – Multistage – Interengaging rotary members
Patent
1992-07-07
1994-01-25
Vrablik, John J.
Rotary expansible chamber devices
Multistage
Interengaging rotary members
418203, F01C 116, F01C 2102, F01C 1816, F01C 2300
Patent
active
052811158
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a rotary screw machine having at least one pair of rotors which are affected by forces from the working fluid in a first axial direction, at least one of the rotors being provided with shaft journals supported by bearing means, including main thrust bearing means and thrust balancing bearing means having a rotating ring and a stationary ring and being provided with thrust balancing means, said thrust balancing means including spring means acting on said stationary ring in said first direction and fluid pressure means acting axially on said stationary ring.
A compressor of this kind is known from U.S. Pat. No. 3,388,854. In that disclosure, the stationary ring of the thrust balancing bearing is pre-loaded by a spring 35 acting in the same direction as the axial gas forces on the rotors. The stationary ring also abuts a fluid actuated piston 36, through which a force can be applied to the ring counteracting the force from the spring. The pressure chamber 37, through which a pressure can be applied to the piston 36 can be connected to a pressure source, i.e. the outlet channel. This is the case under normal operating conditions, whereby the thrust load will be distributed to the thrust bearings on both ends of the rotor. When the compressor is idling, the pressure chamber is relieved to the atmosphere so that only the spring pre-loads the stationary ring. Through this known device, in many cases, a satisfactory distribution of the axial forces on the thrust bearings is attained, but it entails still some limitations regarding an optimal distribution of these forces.
The object of the present invention is to improve the known thrust balancing device in order to reach such a force distribution on the thrust bearings so that the resultant force on each thrust bearing falls within a more narrow range, thereby increasing the possibility to meet the requirements for a sufficient working life for each of the thrust bearings.
SUMMARY OF THE INVENTION
According to the present invention, this object has been attained in that a device of this kind is provided with means for regulating the axial direction of the force exerted by the fluid pressure means.
Each thrust bearing has to be loaded within a certain range, where the maximum force is determined by the working life of the bearing, and the minimum force has to be large enough to avoid sliding of the bearing balls in the rings. With a balancing device according to the invention, the possibilities to attain a force distribution for the bearings so that the force on each bearing falls within this range, will increase due to the fact that the force on the stationary ring of the thrust balancing bearing can be either the sum of the fluid pressure force and the spring force, the spring force along or the difference between the fluid pressure force and the spring force. By having these different alternatives for loading the stationary ring of the thrust balancing bearing, it will be possible to adapt this loading to the different running conditions of the machine; starting, idling, working at low pressure and working at full pressure. During these various running conditions, the external axial force on the rotors, comprised mainly by forces from the pressure of the working fluid but also by forces from driving and timing gears, are of different strength.
With the earlier known technique, where the fluid pressure force on the outer ring either is zero or acts contrary to the spring force, the possibility to adapt the loading of the ring to the various running conditions are more limited, and with that the possibility to keep the forces within the prescribed ranges.
The fluid pressure means preferably takes the form of a pressure chamber, the pressure of which acts on a surface on the stationary ring. The regulating means selectively connects the pressure chamber with either overpressure, atmospheric pressure or underpressure. The machine is particularly intended to be used as a compressor, in which case the ov
REFERENCES:
patent: 3388854 (1968-06-01), Olofsson et al.
patent: 3947078 (1976-03-01), Olsaker
Svenska Rotor Maskiner AB
Vrablik John J.
LandOfFree
Rotary screw machine having thrust balancing means does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rotary screw machine having thrust balancing means, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary screw machine having thrust balancing means will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-724243