Rotary expansible chamber devices – Heat exchange or non-working fluid lubricating or sealing – Heat exchange by diverted incoming or outgoing working fluid
Reexamination Certificate
2000-06-05
2002-04-02
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Heat exchange or non-working fluid lubricating or sealing
Heat exchange by diverted incoming or outgoing working fluid
C418S097000, C418S201100, C418S201200, C418SDIG001
Reexamination Certificate
active
06364645
ABSTRACT:
The invention relates to a screw compressor for compressing a working medium, comprising an outer housing, two screw rotors which are arranged in the outer housing in rotor bores provided for them and a drive for the screw rotors.
In the case of screw compressors of this type, the sealing gap formed between the screw rotors and the rotor bores is a critical parameter since this is responsible for the leakage. The sealing gap normally varies on account of thermal or other influences.
The object underlying the invention is therefore to improve a screw compressor of the generic type in such a manner that the sealing gap is subject to as little variation as possible.
This object is accomplished in accordance with the invention, in a screw compressor of the type described at the outset, in that a compressor screw housing, in which the rotor bores for the screw rotors are arranged, is provided within the outer housing and that a space is arranged between a substantial part of the compressor screw housing and the outer housing.
The provision of a space serves in this respect to couple the compressor screw housing and the outer housing as little as possible thermally and with a view to vibrations or even decouple them. The effects on the compressor screw housing of external, thermal influences acting on the outer housing of the screw compressor are thus reduced and the compressor screw housing itself has the possibility of taking up a thermal state of equilibrium and of remaining in this state, at least only with long-term variations. Moreover, vibrations of the compressor screw housing are transferred to the outer housing to a lesser extent.
With respect to the design of the compressor screw housing, no further details have been given in conjunction with the preceding embodiments. One advantageous embodiment, for example, provides for the compressor screw housing to have an inlet section, a compression section and an outlet section.
With respect to the extension of the space in azimuthal direction to the rotor bores, it is particularly advantageous when the space extends over at least half the circumference of the compression section in azimuthal direction.
It is particularly favorable when the space extends over at least approximately three quarters of the circumference of the compression section in order to thus disconnect as large a portion of the compression section as possible from the outer housing thermally and with regard to vibrations.
With respect to the extension of the space in the area of the inlet section of the compressor screw housing, no further details have so far been given. It is, for example, particularly favorable when the space extends in azimuthal direction to the rotor bores over at least half the inlet section. It is even better when the space extends over three quarters of the circumference of the inlet section in azimuthal direction.
Furthermore, no further details have been given in conjunction with the preceding explanations concerning individual embodiments with respect to the extension of the space in the area of the outlet section. Since the outlet section is in any case, on account of the exiting working medium, at the temperature thereof, it is in principle not absolutely necessary for the space to extend in the area of the outlet section, as well.
However, it is likewise advantageous when the space also extends in circumferential direction over the outlet section in order to bring about an even more uniform temperature in this section.
It is likewise particularly advantageous when the space extends over at least half the circumference of the outlet section in azimuthal direction, even better over approximately three quarters of the circumference of the outlet section in azimuthal direction.
With respect to the extension of the space in axial direction of the screw rotors, no further details have likewise been given in conjunction with the preceding explanations concerning the individual embodiments. One advantageous embodiment, for example, provides for the space to extend on average over at least half of a length of the compressor screw housing extending in axial direction of the screw rotors.
In this respect, it is expedient when the space extends from an end of the compressor screw housing on the outlet side in the direction of an end thereof on the inlet side.
In this respect, it is especially favorable when the space extends at least over the compression section in axial direction.
It is particularly favorable when the space extends as far as the inlet section and thus already contributes to a decoupling of the compressor screw housing and the outer housing in the area of the inlet section.
In conjunction with the inventive solution, it has merely been assumed so far that the space serves to bring about a thermal and vibrational decoupling between the outer housing and the compressor screw housing.
A particularly favorable utilization of the fact that such a space is present is, however, given when the space is acted upon by pressure so that not only is the compressor screw housing acted upon by the pressure resulting internally in the area of the screw rotors during the compression of the working medium but also, on the other hand, a pressure acting from outside on the compressor screw housing counteracts this pressure. It is particularly expedient when the space is subject to a pressure which corresponds approximately to the end pressure of the screw compressor since, in this case, the compressor screw housing is already acted upon from outside by a pressure which always corresponds to the maximum pressure in the interior thereof during the compression of the working medium and so, in the long run, the compressor screw housing is not subject to any one-sided pressure acting on it but, on average, is acted upon with a pressure which is greater than the pressure resulting in the interior thereof.
This solution has the particular advantage that the compressor screw housing need be dimensioned with respect to its mechanical stability only such that it keeps the sealing gap between the screw rotors and the compressor screw housing essentially constant when pressure acts on it from outside and need not be dimensioned, as in the known solutions, such that it is rigid against deformation in relation to a difference in pressure between the interior pressure which ensues and the surrounding pressure.
With respect to the effect of the space, it has so far merely been assumed that the space effects per se a thermal decoupling between the outer housing and the compressor screw housing. It is particularly favorable, however, especially to reduce any thermal distortion between the inlet section and the outlet section or even avoid such distortion which is caused by the inlet section being at the temperature of the working medium entering it whereas the outlet section is heated by the working medium exiting from it and heated due to the compression, when the compressor screw housing can be temperature controlled.
Such a temperature control may preferably be brought about in that the compressor screw housing can be temperature controlled by a temperature control medium provided in the space.
In principle, it would be conceivable to provide any suitable medium as temperature control medium. For example, it would be conceivable to introduce a special temperature control medium into the space for this purpose. The inventive solution is, however, particularly simple when the temperature control medium comprises the working medium.
A supplementary or alternative solution provides for the temperature control medium to comprise oil from a lubricating oil circuit of the screw compressor since this oil from the lubricating oil circuit is likewise heated to a higher temperature, preferably to a temperature close to the temperature of the compressed working medium.
Such a temperature control of the compressor screw housing by a temperature control medium provided in the space can be brought about either by a standing temperature control medium arranged in the space or
Bitzer Kuehlmaschinenbau GmbH
Lipsitz Barry R.
McAllister Douglas M.
Vrablik John J.
LandOfFree
Screw compressor having a compressor screw housing and a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Screw compressor having a compressor screw housing and a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Screw compressor having a compressor screw housing and a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2839023