Rotary screw compressor with improved volume ratio regulation means

Abstract

 A rotary screw compressor with improved volume ratio regulation means, comprising a pair of rotors provided in the interior of a compressor casing and being capable of rotating intermeshingly, and a slide valve provided in parallel with rotating shafts of the rotors and being capable of axially moving back and forth so as to control the volume ratio of discharge gas, the slide valve being provided at one end thereof with a slide stop for adjustment of the position of axial movement thereof, characterized in that, for the slide stop, the elements used for restricting the sway or rotation, generated along with the motion thereof comprise an eccentric support shaft driving the slide stop to move back and forth axially, and a set of plate-shaped bushings provided above the slide stop as well as manufactured and assembled precisely with ease.

Description

BACKGROUND OF THE INVENTION

Field of the Invention:

[0001] The present invention is related to a rotary screw compressor with improved volume ratio regulation means, particularly to a slide stop used for adjusting the position of the axial movement of a slide valve in which volume ratio is controlled. Elements for stabilizing the movement of the slide stop without sway comprise an eccentric support shaft for the control of axial movement of the slide stop and a pair of plate-shaped bushings.

Description of Prior Art:

[0002] A general rotary screw compressor is provided at a casing side thereof with two parallel bores, to each of which a cylindrical rotor is fixedly mounted, each rotor of the rotary screw compressor generally including an elongated land and groove forming the periphery thereof and presented in the form of a spiral. When the rotors rotate, a succession of variation in volume between the rotors may be formed by the intermesh of two rotors, and thus close cooperation of the spiral lands in the way that the land of one rotor may be meshed with the corresponding groove of the other rotor.

[0003] During the continuous rotation of the rotors, gas is compressed gradually and then, the compressed gas is discharged toward an opposite end of the casing, via a continuous variation in space between the lands.

[0004] On one side of the aforementioned rotors, there is provided with a slide valve allowing axial movement. The volume ratio of the compressed gas is determined by the adjustment of the axial position of the slide valve. Moreover, there is further provided at one end of the slide valve with a slide stop used for the adjustment of the axial position of the slide valve.

[0005] A conventional rotary screw compressor is shown in Fig. 1A illustrating U. S. Patent No. 6,409,490, which disclosed a pair of cheese-typed bushings 11, 21 fitted within bores in which the support bearings for rotors are located. Mostly, the bushings 11, 21 are provided for rotating shafts of rotors passing therethrough, and used for facilitating the guidance of the slide stop so as to control its stability.

[0006] Referring to Fig. 1B, each of the cheese-shaped bushings 11, 21 comprises a plate 12, 22, and a projection tube portion 13, 23 extending outward from one end surface of the plate, respectively. At the center of each bushing 11, 21, there may be provided with a through hole 14, 24, respectively, used for the rotor passing therethrough.

[0007] Through practical manufacture and test, however, it is found that, not only the concentricity of the outer peripheries of the plate and the protrusion tube portion must be taken into consideration in the meantime, leading to increased manufacturing difficulties, but also the control of the clearance between the peripheries of the plates and the slide stop may be affected probably, further influencing the stability of the slide stop.

[0008] Moreover, as disclosed in U. S. Patent No. 6,409,490, a slide stop 25 provided at the other end of a slide valve 20 is driven by a support shaft 10 provided at the center of this slide stop. Since said support shaft is provided at the center of slide stop 25, it is then can not be used as a construction of preventing the sway and rotation of slide stop. In this case, thus when the slide stop 25 is moved by the support shaft 10, the slide stop 25 may sway and rotate probably during movement if the clearance between the peripheries of the plates and the slide stop is not properly controlled, thus the compressor is easily to generate noise, even causes the mutual contact between slide stop and rotors.

SUMMARY OF THE INVENTION

[0009] The present invention is related to a rotary screw compressor with improved volume ratio regulation means, particularly to a slide stop used for adjusting the position of the axial movement of a slide valve in which volume ratio is controlled. An eccentric support shaft and a pair of plate-shaped bushings are provided for the slide stop. Tolerance of the periphery of each bushing can be easily manufactured. Thus, accurate guidance of the slide stop is achieved.

[0010] Accordingly, it is a primary object of the present invention to provide a rotary screw compressor with improved volume ratio regulation means, stabilizing the movement of a slide stop without sway further, and providing a member used for the control of the guidance of the slide stop with a feature of easy manufacture.

[0011] According to the rotary screw compressor with improved volume ratio regulation means of present invention, not only allowing the easy control of a clearance between plate-type bushings and the slide stop, but also assuring no sway presented during the movement of the slide stop in such a way that the definite control of the guidance of the slide stop may be obtained more easily, and the compressor would not generate noises, due to an eccentric support shaft driving the slide stop to move, together with the plate-type bushings provided at one end of the slide stop, this is a second object of present invention.

[0012] According to the rotary screw compressor with improved volume ratio regulation means of the present invention, since the bushings are transformed into plate-shaped ones, such that during the manufacture of these bushings, only the outer peripheries thereof have to be taken into consideration, facilitating the accurate manufacture further. Then, a problem of the necessary consideration for too many cumulative tolerances on the manufacture of the conventional cheese-shaped bushings may be avoided, the manufacturing becomes easier there before, and the precision is easier to be controlled.

[0013] According to the rotary screw compressor with improved volume ratio regulation means of present invention, the bushings are transformed into plate-shaped ones, in such a way each of the bushings may be used as an interface element between an end surface of a rotor and an inner wall of a rotor chamber directly. Under the prerequisite of easy manufacture, the bushings may be used to compensate or adjust a possible too large error resulted from the manufacturing deviation of the inner wall of the rotor chamber. The efficiency of compressor can be obtained, this is the forth object of present invention.

[0014] According to the rotary screw compressor with improved volume ratio regulation means of present invention, forming the bushings as plate-shaped ones which are easy to manufacture, in such a way when the rotor contacts with the plate-shaped bushing owing to the improper use of the compressor, only immediate replacement of the bushing is required so as to maintain gap between the rotors, thus eliminating the cast and inconvenience resulted from the need for the replacement of the compressor casing, this is the fifth object of present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a further understanding of the objects, shapes, features and functions of the constituting devices of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings.

Fig. 1A is a structural section view showing a slide valve of a conventional compressor disclosed in U. S. Patent No. 6,409,490.

Fig. 1B is a perspective view showing bushings of the conventional compressor disclosed in U. S. Patent No. 6,409,490.

Fig. 2 is a plan view showing a rotor chamber of a compressor of the present invention before bushings are mounted.

Fig. 3 is a plan view showing the intermesh of male and female rotors of the present invention.

Fig. 4 is an axial section view of the compressor of the present invention.

Fig. 5 is a plan view showing the rotor chamber of the compressor of the present invention after the bushings have been mounted.

Fig. 6 shows plan views and longitudinal section views of the bushings of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] There is shown in Fig. 2 a rotary screw compressor with improved volume ratio regulation means of the present invention. A rotary screw compressor 3 is provided in a casing thereof with two rotor bores 31, 32, allowing a male rotor 41 and a female rotor 51 (as shown in Fig. 3) to rotate together by the intermesh of a groove and a land thereof after the male rotor 41 and the female rotor 51 have been mounted therein.

[0017] Referring to Fig. 4, before the male rotor 41 and the female rotor 51 are mounted in the rotary screw compressor 3, there may be provided at the front end of an inner wall of a rotor chamber 30, i.e., at the location where each rotor bore 31, 32 is positioned, with an individual bushing 42, 52, used for attaching onto the wall of each bore 31, 32, respectively (as shown in Fig. 5)

[0018] Referring to Fig. 6, each of the bushings 42, 52 may be presented in the form of a noncircular plate, and formed with an individual cutting edge 421, 521, respectively, at a location where the two bushings abut against each other. At the center of each bushing, there may be provided with an individual through hole 422, 522 in communication with each rotor bore 31, 32, allowing rotating shafts of the male rotor 41 and the female rotor 51 passing through the through holes 422, 522 and the rotor bores 31, 32 in the meantime so as to be supported, respectively.

[0019] Referring to Fig. 5, after the bushings 42, 52 have been fixedly mounted in the wall of the rotor chamber, there is only a quite small clearance presented between a slide stop 6 and themselves. In comparison to the conventional cheese-type bushing, the plate-type bushings 42, 52 may provide an advantage that precise control of the positioning of the slide stop 6 may be obtained easily due to much lowered manufacturing difficulty and simplified tolerance control, because only the consideration for whether the distance between the slide stop 6 and the bushings is kept below the standard clearance is required during manufacture, on the basis of this design of the plate-type bushings 42, 52.

[0020] Referring again to Fig. 4, the rotary screw compressor with improved volume ratio regulation means of the present invention is further eccentrically provided with a support shaft 61 used for adjusting the position of the slide stop 6. The problem of probable sway presented when the slide stop 6 is moved in case it is driven at the center thereof may be avoided by means of this eccentric support shaft 61, further providing a feature of the stable positioning for the slide stop 6.

[0021] Therefore, by means of the use of the plate-type bushings 42, 52 and the eccentric support shaft 61 described above, the slide stop 6 may be retained without sway during either the back and forth movement of itself, further raising the precision in the control of a slide valve.

[0022] Additionally, a clearance between end portions of the rotors and the inner wall of the rotor chamber may be adjusted by the thickness of the bushings 42, 52, due to the bushings 42, 52 of transformed plate type. For the same reason, even the undesired contact or interference between the end portions of the rotors and the rotor chamber occurs owing to the improper use or external factors during the operation of the rotors, the resulting problem may be relieved by the reconditioning or replacement of the bushings 42, 52. This reconditioning or replacement of the bushings is relatively much simplified, because the bushings of transformed plate type may be easy to manufacture.

[0023] Although the present invention has been described with a certain degree of particularity, the present disclosure has been made by way of example and changes in detail of structure may be made without departing the spirit thereof.

Claims

1. A rotary screw compressor with improved volume ratio regulation means comprises: a rotor chamber provided in an inner wall thereof with rotor bores allowing a pair of rotors to intermeshingly rotate after they have been mounted therein; a slide valve further provided for the control of gas volume ratio through the axial movement thereof; and a slide stop further provided on the moving route of said slide valve for adjusting the axial position thereof, characterized in that said slide stop is provided at one end thereof with a support shaft for the control of the axial movement thereof, and said support shaft used for driving said slide stop to move is eccentrically provided, whereby said slide stop may be retained without sway when it is moved.

2. The rotary screw compressor with improved volume ratio regulation means as claimed in Claim 1, wherein an inner wall of each of said rotor bores is further provided with a bushing used for restricting the sway of said slide stop, each of said bushings being presented in the form of noncircular with a cutting edge formed at a location where said bushings abut against each other, and being provided at the center thereof with a through hole in communication with each of said rotor bores, respectively, a rotating shaft of each of said rotors being allowed to pass through each of said through holes and said rotor bores, respectively, in the meantime so as to be supported; a small clearance between said bushings and said slide stop is kept after said bushings have been firmly mounted, and said bushings are plate-shaped bushings.

3. A rotary screw compressor with improved volume ratio regulation means comprises: a rotor chamber provided in an inner wall thereof with rotor bores allowing a pair of rotors to intermeshingly rotate after they have been mounted therein; a slide valve further provided for the control of gas volume ratio through the axial movement thereof; and a slide stop further provided on the moving route of said slide valve for adjusting the axial position thereof, wherein an inner wall of each of said rotor bores is further provided with a bushing used for restricting the sway of said slide stop, each of said bushings being presented in the form of noncircular with a cutting edge formed at a location where said bushings abut against each other, and being provided at the center thereof with a through hole in communication with each of said rotor bores, respectively, a rotating shaft of each of said rotors being allowed to pass through each of said through holes and said rotor bores, respectively, in the meantime so as to be supported, a small clearance between said bushings and said slide stop being kept after said bushings have been firmly mounted, characterized in that said bushings are plate-shaped bushings.

Drawing