TECHNICAL FIELD

This invention relates to a rotor assembly. In particular, this invention relates to a rotor assembly including a hollow rotor which rotates about a stationary shaft.

SUMMARY OF INVENTION

According to the invention, there is provided a rotor assembly including: - an elongate helical-shaped rotor having an axial cylindrical cavity there through; a stationary shaft axially aligned with the rotor and through the cavity; a housing for housing the rotor and the stationary shaft therein wherein the shaft is fixed within the housing for preventing rotation thereof relative to the housing; and bearing means mounted within the cavity of the rotor for bearing the friction between the rotor and the shaft as the rotor rotates about the stationary shaft.

The rotor may be manufactured from any suitable material including composite alloys, titanium, molybdenum or the like, preferably mild steel. It is to be appreciated that the rotor may be manufactured using any suitable manufacturing process, preferably the rotor is cast and/or machined. An end portion of the rotor may be configured to allow a driving means to be mounted on the rotor. The driving means may be in the form of any suitable driving means and may be in the form of a belt drive, chain drive or motor, preferably a motor. It is to be appreciated that the driving means may be mounted directly on the rotor and there are no transmission losses. The stationary shaft may be manufactured from any suitable material, preferably mild steel.

The housing may be manufactured from any suitable material, preferably steel. The housing may include a fixing means for fixing the shaft to the housing. The fixing means may be configured to fix at least one end of the shaft to the housing, such that the opposing end thereof may be received by the driving means. The fixing means may be in the form of any suitable fixing means, preferably in the form of a lock nut. The lock nut may be configured to allow axial adjustment of the shaft. It is to be appreciated that the housing nay be manufactured using any suitable manufacturing process, preferably the housing is cast and/or machined. The housing may define an opening at one end thereof to receive the rotor and shaft therein. The housing may define an aperture at an end opposing the open end thereof for allowing at least a portion of an end of the rotor and shaft to protrude therethrough, such that the driving means can be mounted thereon and it can be received by the driving means, respectively. The housing may further include a cover for covering the rotor and shaft when received by the opening defined by an end of the housing. Securing means, such as bolts, may further be provided for securing the cover to the housing. The cover may define an aperture therethrough for allowing the end of the shaft, which is to be fixed to the housing, to protrude therethrough. The fixing means may fix the end of the shaft protruding through the cover to the cover. It is to be appreciated that the fixing means may be tightened and loosened for axial adjustment and/or to allow a distance between an end of the rotor and the cover to be adjusted, to allow positioning of the rotor in the housing to be adjusted.

The bearing means may include any suitable bearings such as standard bearings, slide bearings or the like, preferably radial bearings and axial thrust bearings. The axial thrust bearings may be located in a middle portion of the rotor cavity for preventing the rotor from being displaced axially by suction forces. The radial bearings may be located at both ends of rotor cavity for supporting shaft at its ends. A radial bearing may also be located at a portion within the rotor cavity where an outer portion of the rotor is seated in the housing. The bearings means may be spaced axially within the cavity of the rotor for bearing the friction between the rotor and the shaft along an axis thereof. It is to be appreciated that an inner portion of the bearing means may be fixed to the stationary shaft to prevent rotation thereof relative to the shaft whereas an outer portion of the bearings means may be free to allow rotation thereof relative to the shaft.

Spacers may be mounted on the stationary shaft in-between the bearing means. The spacers may be manufactured from any suitable material including steel, hardened composites or metal composites, preferably steel. The spacers may include inner spacer members and outer spacer members which may be coaxially aligned with one another. It is to be appreciated that the inner spacer members may be heat pressed onto the stationary shaft to prevent rotation thereof about the shaft and supports and stiffen the shaft and rotor assembly to lessen bending and to increase resistance to shear forces. It is to be appreciated that ends of the bearing means and ends of the spacers therebetween may abutt and bear against one another to support the shaft and rotor assembly.

A lubrication system may be in fluid flow communication with the bearing means. The lubrication system may include a lubricant and a lubrication channel defined by the shaft which is in fluid flow communication with the bearing means for directing the lubricant towards the bearing means for lubrication thereof. The lubricant may be in the form of any suitable lubricant and may be selected from the group including grease, ISO 67 grade lubricant or the like. A lubrication channel may be defined by both ends of the shaft. The channels may be in fluid flow communication with the bearings means. The lubrication channel at one end of the shaft may be an inlet channel allowing the lubricant to flow into the rotor cavity to lubricate the bearing means. The channel at an opposing end of the shaft may be an outlet channel allowing the lubricant to be removed from the rotor cavity. Seals may be mounted within the rotor cavity for sealing the bearing means and spacers therein. The seals may be in the form of any suitable convention seal. An inner portion of the seal may be fixed to the shaft for preventing rotation thereof about the shaft. An outer portion of the seal may rotate relative to the inner portion of the seal to allow the rotor cavity to remain sealed as the rotor rotates about the shaft. It is to be appreciated that the seals may prevent the lubricant from leaking from the rotor cavity. It is to be appreciated that the seals also prevent the lubricant, preferably water, lubricating the rotor in a compression chamber of the rotor assembly, from leaking into the rotor cavity.

A coupling arrangement may be mounted on an end of the rotor protruding from the housing which may be sized, shaped and configured for receiving the end of the shaft therein, for coupling the drive means directly to the rotor.

It is to be appreciated that surfaces of the rotor assembly and its components may be plated with a nickel composition, molybdenum, Teflon or similar alloys to protect the surfaces against corrosion caused by water or abrasion thereof by abrasive foreign materials. It is to be appreciated that any suitable process to plate may be used, preferably it is an electroless process.

BRIEF DESCRIPTION OF THE DRAWING

A rotor assembly in accordance with the invention will now be described by way of the following, non-limiting examples with reference to the accompanying drawing.

In the drawing: -

Figure 1 is a cross-section of the rotor assembly without the housing. DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings reference numeral 10 refers generally to a rotor assembly which includes an elongate helical-shaped rotor 12 having an axial cylindrical cavity 14 there through, a stationary shaft 16 axially aligned with the rotor 12 and through the cavity, a housing (not shown) for housing the rotor 12 and the stationary shaft 16 therein wherein the shaft 16 is fixed within the housing (not shown) for preventing rotation thereof relative to the housing (not shown), and bearing means 18 mounted within the cavity 14 of the rotor 12 for bearing the friction between the rotor 12 and the shaft 16 as the rotor 12 rotates about the stationary shaft 16.

The rotor 12 is manufactured from mild steel. It is to be appreciated that the rotor 12 is manufactured by being cast or machined. An end portion 20 of the rotor 12 is configured to allow a driving means 22 to be mounted on the rotor 12. The driving means is in the form of a motor 22. It is to be appreciated that the motor 22 is mounted directly on the rotor 12 and there are no transmission losses.

The stationary shaft 16 is manufactured from mild steel.

The housing (not shown) is manufactured from steel. The housing (not shown) includes a fixing means 24 for fixing the shaft 16 to the housing (not shown). The fixing means 24 is configured to fix at least one end 26 of the shaft 16 to the housing (not shown), such that the opposing end 21 thereof is received by the motor 22. The fixing means is in the form of a lock nut 24. The lock nut 24 is configured to allow axial adjustment of the shaft 16. It is to be appreciated that the housing (not shown) can be manufactured by being cast or machined. The housing (not shown) defines an opening at one end (not shown) thereof to receive the rotor 12 and shaft 16 therein. The housing (not shown) defines an aperture (not shown) at an end (not shown) opposing the open end (not shown) thereof for allowing at least a portion of an end 20 of the rotor 12 and shaft 16 to protrude therethrough, such that the motor 22 can be mounted thereon and it can be received by the motor 22, respectively. The housing (not shown) further includes a cover (not shown) for covering the rotor 12 and shaft 16 when received by the opening (not shown) defined by an end (not shown) of the housing (not shown). Securing means (not shown), such as bolts, are further provided for securing the cover (not shown) to the housing (not shown). The cover (not shown) defines an aperture (not shown) therethrough for allowing the end 26 of the shaft 16, which is to be fixed to the housing (not shown), to protrude therethrough. The lock nut fixes the end 26 of the shaft 16 protruding through the cover (not shown) to the cover (not shown). It is to be appreciated that the lock nut 24 is tightened and loosened for axial adjustment and to allow a distance between an end 20 of the rotor 12 and the cover (not shown) to be adjusted, to allow positioning of the rotor 12 in the housing (not shown) to be adjusted.

The bearing means 18 include radial bearings 18a and axial thrust bearings 18b. The axial thrust bearings 18b are located in a middle portion of the rotor cavity 14 for preventing the rotor 12 from being displaced axially by suction forces. The radial bearings 18a are located at both ends of rotor cavity 14 for supporting shaft 16 at its ends. A radial bearing 18ai is located at a portion within the rotor cavity 14 where an outer portion of the rotor 12 is seated in the housing (not shown). The bearings 18a, 18b, 18ai are spaced axially within the cavity 14 of the rotor 12 for bearing the friction between the rotor 12 and the shaft 16 along an axis (not shown) thereof. It is to be appreciated that an inner portion (not shown) of the bearings 18a, 18b, 18ai is fixed to the stationary shaft 16 to prevent rotation thereof relative to the shaft 16 whereas an outer portion (not shown) of the bearings 18a, 18b, 18ai is free to allow rotation thereof relative to the shaft 16.

Spacers 28 are mounted on the stationary shaft 16 in-between the bearings 18a, 18b, 18a- _| . The spacers 28 are manufactured from steel. The spacers include inner spacer members 28a and outer spacer members 28b which are coaxially aligned with one another. It is to be appreciated that the inner spacer members 28a are heat pressed onto the stationary shaft 16 to prevent rotation thereof about the shaft 16 and supports and stiffens the shaft 16 and rotor assembly 10 to lessen bending and to increase resistance to shear forces. It is to be appreciated that ends of the bearings 18a, 18b, 18ai and ends of the spacers 28 therebetween abutt and bear against one another to support the shaft 16 and rotor assembly 10.

A lubrication system (not shown) is in fluid flow communication with the bearings 18a, 18b, 18a- _| . The lubrication system (not shown) includes a lubricant (not shown) and a lubrication channel 30a, 30b defined by the shaft 16 which is in fluid flow communication with the bearings 18a, 18b, 18ai for directing the lubricant (not shown) towards the bearings 18a, 18b, 18ai for lubrication thereof. The lubricant (not shown) is in the form of water. A lubrication channel 30a, 30b is defined by both ends 26,21 of the shaft 16. The channels 30a, 30b are in fluid flow communication with the bearings 18a, 18b, 18a-i. The lubrication channel at one end of the shaft is an inlet channel 30a allowing the water (not shown) to flow into the rotor cavity 14 to lubricate the bearings 18a, 18b, 18a- _| . The channel at an opposing end of the shaft is an outlet channel 30b allowing the water (not shown) to be removed from the rotor cavity 14.

Seals 32 are mounted within the rotor cavity 14 for sealing the bearings 18a, 18b, 18ai and spacers 28 therein. The seals 32 are in the form of any suitable convention seal. An inner portion 32a of the seal 32 is fixed to the shaft 16 for preventing rotation thereof about the shaft 16. An outer portion 32b of the seal 32 rotates relative to the inner portion 32a of the seal 32 to allow the rotor cavity 14 to remain sealed as the rotor 12 rotates about the shaft 16. It is to be appreciated that the seals 32 prevent the water (not shown) from leaking from the rotor cavity 14. It is to be appreciated that the seals 32 also prevent the lubricant (not shown), preferably water, lubricating the rotor in a compression chamber (not shown) of the rotor assembly 10, from leaking into the rotor cavity 14. A coupling arrangement 34 is mounted on an end 20 of the rotor 12 protruding from the housing (not shown) which is sized, shaped and configured for receiving the opposing end 21 of the shaft 16 therein, for coupling the motor 22 directly to the rotor

12.

It is to be appreciated that surfaces of the rotor assembly 10 and its components 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.

It is, of course, to be appreciated that the rotor assembly 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 may be varied as desired.

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.

The inventor believes that the rotor assembly 10 in accordance with the present invention is advantageous in that it has a higher efficiency than other known rotors. The rotor assembly 10 also experiences less bending than other known rotors because of the fact that the rotor 12 rotates about the shaft 16. Another advantage is there are no transmission losses as the motor 22 is directly mounted on the rotor 12 by a coupling arrangement 34. Using water as a lubricant (not shown) in the compression chamber is advantageous because it allows the rotor assembly 10 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 assembly 10 that rotate. The enclosed lubrication system (not shown) is also less sensitive to an increase in the pH values of the water (not shown), due to pollution of the air that is sucked in by the rotor assembly 10, thus no filtration system is required to filter and reduce the pH of the water (not shown) The hollow rotor 12 has a lower rotor backlash and also allows for clearances between the rotor 12 and the housing (not shown) and cover (not shown). The bearings 18a, 18b, 18ai and spacers 32 which are mounted within the hollow rotor 12 allows for significantly less rotor bending by providing support for the shaft 16.