Helical compressor with internal bearings

Abstract

A compressor which includes a male rotor assembly including an elongate male helical-shaped rotor having an axial cylindrical cavity therethrough, a stationary shaft axially aligned with the male rotor and through the cavity, a housing for housing the male rotor and its associated stationary shaft therein, wherein the shaft is fixed within the housing, and bearing means mounted within the cavity of the male rotor for bearing the friction between the rotor and the shaft as the male rotor rotates about the stationary shaft.

Claims

1. A compressor comprising: a male rotor assembly which comprises: an axially adjustable elongate male helical-shaped rotor having a first axial cylindrical cavity therethrough; an axially adjustable first stationary shaft axially aligned with the male helical-shaped rotor and through the first axial cylindrical cavity; and a first bearing assembly rotationally connecting the first axial cylindrical cavity and male rotor, the first bearing assembly comprising first radial bearings and first axial thrust bearings with the first radial bearings mounted inside the first axial cylindrical cavity at each end thereof and with the first axial thrust and/or bearings mounted in a middle portion of the first axial cylindrical cavity; a housing for housing the male helical-shaped rotor and the housing also rotationally fixes the first stationary shaft within a first housing cavity of the housing; a female rotor assembly which comprises: an axially adjustable elongate female helical-shaped rotor having a second axial cylindrical cavity therethrough, which is in register with the male helical-shaped rotor; an axially adjustable second stationary shaft axially aligned with the female helical-shaped rotor and through the second axial cylindrical cavity; and a second bearing assembly rotationally connecting the second axial cylindrical cavity and female rotor, the second bearing assembly comprising second radial bearings and second axial thrust bearings with the second radial bearings mounted inside the second axial cylindrical cavity at each end thereof and with the second axial thrust and/or radial bearings mounted in a middle portion of the second axial cylindrical cavity; wherein the housing also houses the female helical-shaped rotor and the housing also rotationally fixes the second stationary shaft in a second housing cavity within the housing; wherein the housing defines an aperture at an end for allowing at least a portion of an end of either the male helical-shaped rotor or the female helical-shaped rotor and its associated shaft to protrude there through, such that a driving means can be mounted on the end of the male helical-shaped rotor or the female helical-shaped rotor or be received by the driving means; wherein the driving means is coupled to either the male helical-shaped rotor or the female helical-shaped rotor; and wherein the male helical shaped rotor and the female helically shaped rotor define working cavities therebetween which capture, drive and compress a fluid substance forward when the male helical-shaped rotor and the female helical-shaped rotor are driven.

2. A compressor as claimed in claim 1 wherein the housing includes lock nuts for axially adjustably fixing the first and second stationary shafts to the housing, which the lock nuts are configured to adjustably fix one end of each of the first and second stationary shafts to the housing, such that the opposing free end thereof can be received by the driving means.

3. A compressor as claimed in claim 1 wherein the housing defines an opening opposite the aperture to receive the first stationary shaft, the second stationary shaft, the male helical-shaped rotor and the female helical-shaped rotor therein.

4. A compressor as claimed in claim 3 wherein the housing comprises a cover for covering the first stationary shaft, the second stationary shaft, the male helical-shaped rotor and the female helical-shaped rotor when received by the opening defined by an end of the housing.

5. A compressor as claimed in claim 1 wherein the first and second axial thrust bearings are located in the first axial cylindrical cavity and second axial cylindrical cavity respectively and wherein the lock nuts allow axial adjustment and lock into position the male helical-shaped rotor and the female helical-shaped rotor.

6. A compressor as claimed in claim 1 wherein the first radial bearings are located at both ends of first axial cylindrical cavity for supporting the first stationary shaft at its ends.

7. A compressor as claimed claim 1 wherein the first radial bearing is located at a portion within the first axial cylindrical cavity where an outer portion of the male helical-shaped rotor is seated in the housing.

8. A compressor as claimed in claim 1 wherein the first and second radial bearings are spaced axially within the first axial cylindrical cavity and the second axial cylindrical cavity respectively.

9. A compressor as claimed in claim 1 wherein spacers are mounted on the first stationary shaft in-between the first radial bearings and the first axial thrust bearings, and the second stationary shaft in-between the second radial bearings and the second axial thrust bearings.

10. A compressor as claimed in claim 1 wherein a lubrication system is in fluid flow communication with the first bearing assembly and the second bearing assembly, inside the respective first and second axial cylindrical cavities, which the lubrication system comprises a lubricant and a lubrication channel defined by both ends of the first stationary shaft and the second stationary shaft and a corresponding, an inlet and outlet respectively, which is in fluid flow communication with first bearing assembly and the second bearing assembly, inside the respective first and second axial cylindrical cavities.

11. A compressor as claimed in claim 10 wherein seals are mounted within the first axial cylindrical cavity and the second axial cylindrical cavity for sealing the first bearing assembly respectively and the second bearing assembly respectively and wherein an inner portion of a first seal of the seals is fixed to the first stationary shaft for preventing rotation thereof about the first stationary shaft and an outer portion of the first seal to rotate relative to the inner portion of the first seal to allow the first axial cylindrical cavity to remain sealed as the male helical-shaped rotor rotates about the first stationary shaft, and wherein an inner portion of a second seal of the seals is fixed to the second stationary shaft for preventing rotation thereof about the second stationary shaft and an outer portion of the second seal to rotate relative to the inner portion of the second seal to allow the second axial cylindrical cavity to remain sealed as the female helical-shaped rotor rotates about the second stationary shaft.

12. A compressor as claimed in claim 1 wherein a coupling arrangement is mounted on an end of the first male helical-shaped rotor protruding from the housing which is sized, shaped and configured for receiving the end of the male helical-shaped rotor therein, for coupling the driving means directly to the male helical-shaped rotor; or wherein a coupling arrangement is mounted on an end of the female helical-shaped rotor protruding from the housing which is sized, shaped and configured for receiving the end of the female helical-shaped rotor therein, for coupling the driving means directly to the female helical-shaped rotor.

13. The compressor as claimed in claim 1, wherein another first radial bearing is mounted in a middle portion of the first axial cylindrical cavity, and another second radial bearing is mounted in a middle portion of the second axial cylindrical cavity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A compressor in accordance with the invention will now be described by way of the following, non-limiting examples with reference to the accompanying drawings.

(2) In the drawings:

(3) FIG. 1 is a cross-section of the compressor;

(4) FIG. 2 is a cross-section of the female rotor; and

(5) FIG. 3 is a cross-section of the male rotor.

DETAILED DESCRIPTION OF THE INVENTION

(6) Referring now to the drawings reference numeral 10 refers generally to a compressor which includes a male rotor assembly 12 including an elongate male helical-shaped rotor 14 having an axial cylindrical cavity 16 therethrough, a stationary shaft 18 axially aligned with the male rotor 14 and through the cavity 16, a housing 20 for housing the male rotor 14 and its associated stationary shaft 18 therein wherein the shaft 18 is fixed within the housing 20 for preventing rotation thereof relative to the housing 20, and bearing means 22 mounted within the cavity 16 of the male rotor 14 for bearing the friction between the rotor 14 and the shaft 18 as the male rotor 14 rotates about the stationary shaft 18. The compressor 10 also includes a female rotor assembly 24 including an elongate female helical-shaped rotor 26 having an axial cylindrical cavity 28 therethrough, which is in register with the male rotor 14, a stationary shaft 30 axially aligned with the female rotor 26 and through the cavity 28, wherein the housing 20 also houses the female rotor 26 and its associated stationary shaft 30 therein wherein the shaft 30 is fixed within the housing 20 for preventing rotation thereof relative to the housing 20, bearing means 22 mounted within the cavity 28 of the female rotor 26 for bearing the friction between the rotor 26 and the shaft 30 as the rotor 26 rotates about the stationary shaft 30, a drive means 32 for driving either the male 14 or female 26 rotor, and wherein the complementary helix formations 34a,34b define cavities between the male 34a and female 34b formations which capture, drive and compress a fluid substance (not shown) forward when the rotors 14,26 are driven.

(7) The rotors 14,26 are manufactured from mild steel. It is to be appreciated that the rotors 14,26 are cast or machined. An end portion 14a of the male rotor 14 is configured to allow a driving means 32 to be mounted on the rotor 14. The driving means is in the form of a motor 32. It is to be appreciated that the motor 32 is mounted directly on the rotor 14 and there are no transmission losses.

(8) The stationary shafts 18,30 are manufactured from mild steel.

(9) The housing 20 is manufactured from steel. The housing 20 includes a fixing means 38 for fixing the shafts 18,30 to the housing 20. The fixing means 38 is configured to fix at least one end 18a of the male shaft 18 to the housing, such that the opposing free end 18b thereof may allow the corresponding rotor end 14b to be received by the motor 22. The fixing means 38 is in the form of a lock nut. The lock nut 38 is configured to allow axial adjustment of the shaft 18,30. It is to be appreciated that the housing 20 is cast or machined. The housing 20 defines an opening 40 at one end 20a thereof to receive the rotors 14,26 and shafts 18, 30 therein. The housing 20 defines an aperture (not shown) at an end 20b opposing the open end 20a thereof for allowing at least a portion of an end 14b of the male rotor 14 and shaft 18 to protrude therethrough, such that the motor 22 can be mounted thereon and it can be received by the motor 22, respectively. The housing 20 further includes a cover 42 for covering the rotors 14,26 and shafts 18,30 when received by the opening 40 defined by an end 20a of the housing 20. Securing means, such as bolts, are further provided for securing the cover 42 to the housing 20. The cover 42 defines a threaded aperture (not shown) therethrough for allowing the ends 18a,30a of the shafts 18,30, which is to be threadedly fixed to the housing 20, to protrude therethrough. The lock nut 38 fixes the ends 18a,30a of the shafts 18,30 protruding through the cover 42 to the cover 42. It is to be appreciated that the lock nut 38 is tightened and loosened for axial adjustment to adjust the interface clearance between the male 34a and female 34b formations, up to 20 micron which varies according to a diameter and length of the rotors 14,26, and to allow positioning of the rotors 14,26 in the housing 20 to be adjusted.

(10) The bearing means 22 includes radial bearings 22a and axial thrust bearings 22b. The axial thrust bearings 22b are located in a middle portion of the rotor cavity 16,28 for preventing the rotor 14,26 from being displaced axially by suction forces. The radial bearings 22a are located at both ends of rotor cavity 16,28 for supporting the shaft 18,30 at its ends. A radial bearing 22a1 is also located at a portion within the rotor cavity 16 where an outer portion of the rotor 14 is seated in the housing 20. The bearings 22a,22b, 22a1 are spaced axially within the cavity 16,28 of the rotor 14,26 for bearing the friction between the rotor 14,26 and the shaft 18,30 along an axis thereof. It is to be appreciated that an inner portion (not shown) of the bearings 22a,22b, 22a1 is fixed to the stationary shaft 18,30 to prevent rotation thereof relative to the shaft 18,30 whereas an outer portion (not shown) of the bearings means 22a,22b, 22a1 is free to allow rotation thereof relative to the shaft 18,30.

(11) Spacers 44 are mounted on the stationary shaft 18,30 in-between the bearings 22a,22b, 22a1. The spacers 44 are manufactured from steel. The spacers 44 include inner spacer members 44a and outer spacer members 44b which are coaxially aligned with one another. It is to be appreciated that the inner spacer members 44a are heat pressed onto the stationary shaft 18,30 to prevent rotation thereof about the shaft 18,30 and supports and stiffens the shaft 18,30 and rotor assembly 12,24 to lessen bending and to increase resistance to shear forces. It is to be appreciated that ends (not shown) of the bearings 22a,22b, 22a1 and ends (not shown) of the spacers 44 therebetween abutt and bear against one another to support the shaft 18,30 and rotor assembly 12,24.

(12) A lubrication system (not shown) is in fluid flow communication with the bearings 22a,22b, 22a1. The lubrication system (not shown) includes a lubricant (not shown) and a lubrication channel 46a,46b defined by the shaft 18,30 which is in fluid flow communication with the bearings 22a,22b, 22a1 for directing the lubricant (not shown) towards the bearings 22a,22b, 22a1 for lubrication thereof. The lubricant (not shown) is in the form of ISO 67 grade lubricant. A lubrication channel 46a,46b is defined by both ends 18a, 18b,30a,30b of the shaft 18,30. The channels 46a,46b are in fluid flow communication with the bearings 22a,22b, 22a1. The lubrication channel 46a at one end 18a,30a of the shaft 18,30 is an inlet channel 46a allowing the ISO 67 grade lubricant (not shown) to flow into the rotor cavity 16,28 to lubricate the bearings 22a,22b, 22a1. The channel 46b at an opposing end 18b,30b of the shaft 18,30 is an outlet channel 46b allowing the ISO 67 grade lubricant (not shown) to be removed from the rotor cavity 16,28.

(13) Seals 48 are mounted within the rotor cavity 16,28 for sealing the bearings 22a,22b, 22a1 and spacers 44 therein. The seals 48 are in the form of any suitable convention seal. An inner portion 48a of the seal 48 is fixed to the shaft 18,30 for preventing rotation thereof about the shaft 18,30. An outer portion 48b of the seal 48 rotates relative to the inner portion 48a of the seal 48 to allow the rotor cavity 16,28 to remain sealed as the rotor 14,26 rotates about the shaft 18,30. It is to be appreciated that the seals 48 prevent the ISO 67 grade lubricant (not shown) from leaking from the rotor cavity 16,28. It is to be appreciated that the seals 48 seal the ISO 67 grade lubricant (not shown) within the cavity 16,28 of the rotor 14,26 such that the ISO 67 grade lubricant ((not shown) does not come into contact and contaminate air (not shown) that is compressed. It is to be appreciated that the seals 48 also prevent the lubricant (not shown), preferably water, lubricating the rotors 14,26 in a compression chamber (not shown) of the compressor, from leaking into the rotor cavities 16,28.

(14) A coupling arrangement 50 is mounted on an end 14b of the male rotor 14 protruding from the housing 20 which is sized, shaped and configured for receiving the end 18b of the shaft 18 therein, for coupling the motor 22 directly to the rotor 14.

(15) It is to be appreciated that surfaces of the rotor assemblies 12,24 are plated with a nickel composition to protect the surfaces against corrosion caused by water or abrasion thereof by abrasive foreign materials. It is to be appreciated that it is an electroless process.

(16) It is, of course, to be appreciated that the compressor 10 in accordance with the invention is not limited to the precise constructional and functional details as hereinbefore described with reference to the accompanying drawings and which is varied as desired.

(17) Although only certain embodiments of the invention have been described herein, it will be understood by any person skilled in the art that other modifications, variations, and possibilities of the invention are possible. Such modifications, variations and possibilities are therefore to be considered as falling within the spirit and scope of the invention and hence form part of the invention as herein described and/or exemplified. It is further to be understood that the examples are provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and is not meant to be construed as unduly limiting the reasonable scope of the invention.

(18) The inventor believes that the compressor 10 in accordance with the present invention is advantageous in that it has a higher efficiency than other known rotors. The rotor assemblies 12,24 also experience less bending than other known rotors because of the fact that the rotor 14,26 rotates about the shaft 18,30. Another advantage is there are no transmission losses as the motor 22 is directly mounted on the rotor 14 by a coupling arrangement 50. Using water as a lubricant (not shown) for the rotors in the compression chamber is advantageous because it allows the rotor assemblies 12,24 to run at lower operating temperatures. A further advantage is that the enclosed lubrication system (not shown) allows the rotating parts to be effectively lubricated, thus resulting in no wear on the parts of the rotor assemblies 12,24 that rotate. The enclosed lubrication system (not shown) is also less sensitive to an increase in the pH values of the water, due to pollution of the air that is sucked in by the rotor assemblies 12,24, thus no filtration system is required to filter and reduce the pH of the water (not shown). The hollow rotor 14,26 has a lower rotor backlash and also allows for clearances between the rotor 14,26 and the housing 20 and cover 42. The bearings 22 and spacers 44 which are mounted within the hollow rotor 14,26 allows for significantly less rotor bending by providing support for the shaft 18,30. The compressor 10 in accordance with the present invention also has an expected lifetime which is twice to three times as long as present oil-free compressors.