Field of the Invention

The present invention relates to a gear assembly.

The invention has been developed primarily as a motor or a pump and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

Background

The present invention seeks to provide a gear assembly useful for use as a motor or a pump, or to at least provide an alternative.

It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

U.S. Patent No. 4753585 discloses a prime mover for transforming energy from the pressure form to the mechanical form. The prime mover comprises a pair of toothed rotors which engage one another so as to be self-timing. Each rotor has a first portion of relatively large diameter and a second portion of relatively small diameter, each of the portions extending approximately 180°. The rotors are enclosed in respective intersecting cylindrical chambers in a housing, with the tips of the teeth of the small diameter portion of each rotor being displaced radially inwardly from the peripheral surface of the corresponding chamber, and with the tips of the teeth of the large diameter portion of each rotor being directly adjacent to the inner surface of the corresponding chamber. First and second sealing members are mounted in the housing, and these engage the tips of successively passing teeth of the large diameter portion of each rotor, as the rotors turn. A drive fluid is introduced into an inlet in the housing located at the common tangent of the two rotors, and the drive fluid exits through a diametrically opposed aligned outlet.

U.S. Patent No. 6352420, discloses a compound teeth type gas compressor comprises a housing with an upper end cover and a lower end cover mounted on both sides of the housing for constituting a seal cavity, a pair of meshing gears rotatably accommodated in the cavity, each gear having two kinds of teeth which are of different size and have a common pitch circle, an inlet port and an outlet port, an intake chamber and a discharge chamber positioned respectively on the sides of the inlet port and the outlet port in the cavity, characterized in fact that the gears are uni-directionally rotated, one of them is a driving gear having larger teeth, the other is a driven gear having larger gullets engaged with the larger teeth, the larger teeth and the larger gullets are formed with asymmetric shapes, and, as viewed in the rotation directions of the gears, their front flank profile curves are designed to achieve a transmission of a constant angular velocity ratio while their rear flank profile curves are designed to be in conjugate contact with each other from the beginning to the end of touching.

British Patent No. 1242293A discloses a gear type rotary machine comprising two working gears mounted within a chamber, each gear having teeth of two different sizes on the same pitch circle, and two guide wheels located outside the chamber and coupled respectively to the two working gears, the guide wheels being in permanent rotary engagement with one another.

German Patent No. 2524280A1 discloses a rotary piston machine, comprising two mutually biasing piston rotor which rotate against one another in axially parallel intersecting cylindrical casing chambers lying on an axis of rotation.

Each of the above patents discloses a gear assembly including two gears, the arrangement of which is generally limited in terms of torque output. Further, the arrangement of each of the gear assemblies may suffer from fluid leakage due to the arrangement of fluid inlet and outlet being disposed on a sidewall of a housing of the gear assembly.

Summary

According to a first aspect, the present invention provides a gear assembly comprising: a housing having an internal cavity;

at least three gears disposed within the internal cavity, each of the gears meshing with an adjacent one of the gears at a meshing zone; and

a port arrangement adapted for forcing fluid through each meshing zone in use.

Preferably, the housing comprises a rear wall, a front wall and a sidewall therebetween, the port arrangement being disposed at one of the front wall and the rear wall.

Preferably, each of the port arrangements comprises an inlet and an outlet.

Preferably, the inlet and the outlet of each port arrangement are arranged about the respective meshing zone.

Preferably, each of the .gears comprises a set of spaced gear teeth, the teeth of each of the gears meshing with those of the adjacent one of the gears at the respective meshing zone.

Preferably, the gear assembly is adapted for gear position invariant fluid injection.

Preferably, the inlets are disposed such that fluid may flow through at least one of the inlets, in use, regardless of positions of the gear teeth of the gears. Preferably: each of the gears comprises a first set of spaced gear teeth interposed between a second set of shorter gear teeth; the internal cavity of the housing defines an internal peripheral profile substantially matching an external peripheral swept profile of the first sets of gear teeth, respective spaces being defined between the internal peripheral profile and the second set of gear teeth; and each of the port arrangements comprises an inlet and an outlet, at least one inlet and at least one outlet being formed in the housing and being in fluid communication with the spaces in use.

Preferably, the housing comprises a rear wall, a front wall and a sidewall therebetween, wherein the internal peripheral profile is defined by the sidewall.

Preferably, the housing comprises respective sealing means between the gears and the rear wall, and between the gears and the front wall.

Preferably, the rear wall, the front wall and the sidewall are made separately from each other.

Preferably, the gear assembly further comprises respective sealing means between the sidewall and the front wall, and the sidewall and the rear wall.

Preferably, the rear wall and the sidewall are integral with each other.

Preferably, the gear assembly further comprises sealing means between the sidewall and the front wall.

Preferably, the at least one inlet and the at least one outlet are formed in the rear wall.

Preferably, the at least one inlet is formed in the rear wall and the at least one outlet is formed in the front wall.

Preferably, the housing comprises a respective axle for supporting a respective bearing for each gear.

Preferably, at least one of the gears is coupled to a shaft which extends through an aperture in the housing.

Preferably, the gear is mounted to the shaft for co-rotation about the gear axis

Preferably, the first and second sets of gear teeth mesh at a meshing zone, and the at least one inlet and the at least one outlet are formed adjacent the meshing zone.

Preferably, the at least one inlet and the at least one outlet are formed adjacent opposing portions of the meshing zone.

Preferably, each tooth in the first set of gear teeth comprises a correspondingly shaped valley formed adjacent thereto. Preferably, each tooth in the second set of gear teeth comprises a correspondingly shaped valley formed adjacent thereto.

_, Preferably, the second set of gear teeth comprises at least two teeth interposed between each pair teeth of the first set of gear teeth.

Preferably, each first set of gear teeth gear comprises at least three teeth.

Preferably, each tooth in the first set of gear teeth comprises sealing means for substantially sealing with the internal periphery of the housing.

Preferably, the gears include first, second and third gears that are disposed generally side by side, the second gear being disposed between the first and third gears.

Preferably, at least one of the gears is coupled to a shaft which extends through an aperture in the housing. ' ^

Preferably, the at least one gear is mounted to the shaft for co-rotation about the gear axis.

Preferably, the teeth of the first and second gears mesh at a first meshing zone, and the teeth of the second and third gears mesh at a second meshing zone, wherein the assembly comprises at least first and second inlets respectively formed adjacent the first and second meshing zones.

Preferably, the assembly comprises at least first and second outlets respectively formed adjacent the first and second meshing zones.

Preferably, the inlet and the outlet adjacent each of the first and second meshing zones are formed at opposing portions thereof.

Preferably, the at least first and second inlets are formed adjacent opposing portions of the second gear.

Preferably, the at least first and second outlets are formed adjacent opposing portions of the second gear.

Preferably, the gear assembly further comprises a third outlet formed adjacent an outer portion of the first gear distal to the second gear.

Preferably, the gear assembly further comprises a fourth outlet formed adjacent an outer portion of the third gear distal to the second gear.

Preferably, each tooth in the first set of gear teeth of the second gear comprises a recess or aperture formed at a distal portion thereof.

Other aspects of the invention are also disclosed. Brief Description of the Drawings

Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of a gear assembly in. accordance with a preferred embodiment of the present invention;

Fig. 2 is a front perspective view of the gear assembly of Figure 1 with the front wall lifted for illustration purposes;

Fig. 3 is a front internal view of the gear assembly of Figure 1 ;

Fig. 4 is a side cross-section view of the second gear portion of the gear assembly of Figure

1 ;

Fig. 5 is an enlarged view of encircled portion A of Figure 3;

Fig. 6 is an exploded perspective view of the gear assembly of Figure 1 ; and

Fig. 7 is an exploded perspective view of a modified embodiment of the gear assembly of Figure 1 .

Description of Embodiments

It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

Figures 1 to 6 show a gear assembly 10 according to a first preferred embodiment of the present invention. Referring primarily to Figures 2 to 4 and 6, the gear assembly 10 comprises a housing 12 having an internal cavity 18 which houses a first gear 20a, a second gear 20b and a third gear 20c which are disposed side by side and coupled to each other.

The housing 12 comprises a first portion 31 and a second portion 32. The first potion 31 comprises a rear wall 13 and a sidewall 14 which are formed integrally with each other. The second portion 32 comprises a front wall 15. The housing 12 further comprises a sealing means 6 between the sidewall 14 and the front wall 15, the sealing means 16 being a shaped rubber ring extending around the periphery of the cavity 18. Corresponding aligned apertures 1 1 are formed in the first and second portions 31 and 32, through which respective attachment bolts (not shown) are inserted to attach the second section 32 to the first section 31.

The front wall 15 further comprises a central shaft aperture 33 and two side axle apertures 34 formed therein. A front bearing recess 42 (see Fig. 4) is formed around the central shaft aperture 33 and facing the cavity 18. The rear wall 13 comprises a central shaft recess 36 (see Fig. 4) and four apertures 37a to 37d equiangularly spaced around the central shaft recess 36. The apertures 37a to 37d form the inlets and outlets of the gear assembly 10 as further described below. The rear wall further comprises two side axle formations 38a and 38c which extend into the cavity 18 and formed on opposing sides of the central shaft recess 36. Further respective bolts (not shown) are inserted into the axle apertures 34 and through the side axle formations 38.

The axle formations 38a and 38c support respective bearings 39a and 39c respectively for the first gear 20a and third gear 20c. The central shaft recess 36 receives a rear bearing 41a and the front bearing recess 42 receives a front bearing 41b, the bearings 41 a and 41 b both supporting a shaft 60 as further described below.

The first gear 20a, second gear ^' 20b and third gear 20c are substantially identical in size and shape. The first gear 20a and third gear 20c are identical and each includes a central aperture 51 for receiving the respective bearing 39a and 39c therein for respective rotation about the axle formations 38a and 38b.

The second gear 20b comprises a central aperture 52 through which is inserted the shaft 60. The shaft 60 is also inserted through the rear bearing 41a, front bearing 41 b, an O ring seal 62 and the central shaft aperture 33 of the front wall 15. The second gear 20b comprises a fixing pin recess 64 which receives a fixing pin 63. The fixing pin 63 is inserted through an aperture 65 of the shaft 60. Thus, the second gear 20b is fixed to the shaft 60 co-rotation therewith. The shaft 60 is then supported for rotation at the rear wall 13 and front wall 15 by the rear bearing 41a and the front bearing 41b respectively. The O ring seal 62 seals the Shaft 60 with the central shaft aperture 33.

The teeth configuration of the first, second and third gears 20 will now be described. The first, second and third gears 20 have an identical teeth configuration which comprises a first set of spaced gear teeth 70 interposed between a second set of shorter gear teeth 80. The first set of spaced gear teeth 70 comprises three teeth 71 equiangularly spaced about the respective gear axis. Each tooth 71 includes a correspondingly formed valley 72 adjacent thereto. The second set of shorter gear teeth 80 comprises three teeth 81 is disposed between each pair of teeth 71 of the first set 70. Each tooth 81 also includes a correspondingly shaped valley 82 adjacent thereto.

As best shown in Figures 2 and 3, the first set of gear teeth 70 and the second set of gear teeth 80 respectively mesh with each other in use. The gear teeth of the first and second gears 20a and 20b mesh at a first meshing zone 91 and the gear teeth of the second and third gears 20b and 20c mesh at a second meshing zone 92. It can be seen that the apertures 37a and 37b are formed at opposing portions of the first meshing zone 91 and the apertures 37c and 37d are formed at opposing portions of the second meshing zone 92.

The side wall 14 of the housing 12 defines an internal peripheral profile 19 of the cavity 18 substantially matching an external peripheral swept profile of the first sets of gear teeth 70 of the first, second and third gears 20. Respective spaces 29 are defined between the internal peripheral profile 19 and the second set of gear teeth 80. As shown in Figure 4, front and rear faces of the gears 20 substantially engage the front and rear walls respectively. As shown in Figure 5, a distal portion 74 of each tooth 71 includes an aperture 73 for receiving a fixing pin 75 of a resilient seal member 76, such that the seal member 76 engages the internal peripheral profile 19. The seal members 76 thus substantially sealingly separate the spaces 29.

In one use, the apertures 37a and 37c are configured as the inlets and the apertures 37b and 37d are configured as the outlets of the gear assembly 10. Compressed air communicated into the inlets travels between the respective spaces 29 and pushes the respective teeth 71 , until the compressed air exits via the outlets. The travel direction of the air is indicated by the arrows 95 in Figure 3. This results in rotation of the shaft 60 which can be utilised as desired.

If desired, additional outlets 97 can be formed in the rear wall adjacent portions of the first and third gears substantially diametrically opposite to the second gear. Also, each tooth 71 of the second gear comprises an air pressure relief aperture 99 formed at a distal portion thereof.

Air can be communicated into the inlets from an air compressor or as the product of combustion of fuels such as gas, petrol, diesel or biofuel. The rotation of the shaft 60 can be used for powering vehicles and tools.

Alternatively,, the shaft 60 can be rotated by a motor with the inlets communicated to a fluid, such as a liquid or air. Rotation of the shaft 60 draws in the fluid into the gear assembly 10 and out via the outlets. The gear assembly 10 thus functions as a pump.

The modified embodiment gear assembly 0a shown in figure 7 is substantially similar to the gear assembly 10 above. In this embodiment however, the rear wall 13 is formed separately from the side wall 14 and thus includes an additional sealing means 16b therebetween. Also in this embodiment, the axles 38a and 38b are formed separately from the rear wall 13 and attached thereto when bolts are inserted through the axle apertures 34.

In one embodiment, the port arrangement of the apertures 37a, 37b is adapted for forcing fluid through the first meshing zone 91 , and the port arrangement of the apertures 37c, 37d is adapted for forcing fluid through the second meshing zone 92. It is to be noted that the , apertures 37a-37d are arranged such that fluid may flow into one of the apertures 37a, 37c when the other of the same is obstructed by one of the teeth 71. Such a mechanism ensures smooth flow (i.e., injection) of liquid into the gear assembly 10 regardless of positions of the teeth 71 of the gears 20a-20c, which enables the gear assembly 10 to be driven to start without first adjusting the positions of the gears 20a-20c (e.g., gear position invariant fluid injection). In this embodiment, the port arrangements are disposed at the rear wall 13 and disposed proximate to the respective meshing zones 91 , 92 such that fluid may flow into the gear assembly in a lateral direction. Such a configuration of the port arrangements ensures that most of fluid injected from the aperture 37a is forced through to apertures 37b, and that most of fluid injected from apertures 37c is forced through to aperture 37d, thereby preventing leakage of fluid. Unlike the gear assembly 10 of the present invention, the aforementioned conventional gear assemblies of the prior art are relatively more susceptible to fluid leakage as a result of the inlet and the outlet been disposed relatively distal from the meshing zone.

However, it is to be noted that implementation of the port arrangements are not limited to such. In other embodiments, the port arrangements may be disposed at the other surfaces.

Whilst preferred embodiments of the present Invention have been described, it will be apparent to skilled persons that modifications can be made to the embodiments described. For example, the inlets can be formed in the rear wait and the outlets can be formed in the front wall. Also, it is apparent that the third gear can be omitted and the internal peripheral profile of the cavity 18 can be correspondingly reshaped. Further, it is also apparent that is the first and third gears can also be coupled to respective shafts similar to the shaft 60.

Interpretation

Embodiments:

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular leatures, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the above description of example embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description of Specific Embodiments are hereby expressly incorporated into this Detailed Description of Specific Embodiments, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Different Instances of Objects

s used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

Specific Details

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Terminology

In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "forward", "rearward", "radially", "peripherally", "upwardly", "downwardly", and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

Comprising and Including

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Any one of the terms: including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising.

Scope of Invention

Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Industrial Applicability

It is apparent from the above, that the arrangements described are applicable to the motion and power transfer industries.