WO2018000049A1

WO2018000049A1 - A vehicle and drive mechanism for a vehicle

Info

Publication number: WO2018000049A1
Application number: PCT/AU2017/050681
Authority: WO
Inventors: Arthur Derek McBeth Thompson; Stephen Hugh Thompson
Original assignee: ADiT Engineering Pty. Ltd.
Priority date: 2016-06-30
Filing date: 2017-06-30
Publication date: 2018-01-04

Abstract

A skid steer vehicle directed towards ensuring that an equal amount of hydraulic fluid flows into each wheel motor such that each rotates at the same speed with each wheel motor having full pump pressure available, at least theoretically, so is capable of high torque with the provision of the relief valves in association with a hydraulic fluid flow divider ensures that the hydraulic pump and the system is protected from excess pressure, at both the hydraulic fluid flow dividers and motor mounted relief manifolds.

Description

A VEHICLE AND DRIVE MECHANISM FOR A VEHICLE TECHNICAL FIELD

[0001] The present invention relates to a vehicle and drive mechanism for a vehicle, particularly a hydraulic drive skid steer utility vehicle.

BACKGROUND ART

[0002] Skid steer vehicles are known. One such skid steer vehicle is disclosed in Australian Patent Application No. 36591/89.

[0003] That document discloses a skid steer utility vehicle comprising hydraulically driven front and rear pairs of wheels, an engine located between said front and rear pairs of wheels, a cabin located forward of said front wheels, and suspension means for mounting the axle of each said wheel movably relative to the body of said utility vehicle, said suspension means comprising for each wheel, a pivotable arm having one end pivotally connected to the body of said vehicle and the other end connected to a respective wheel.

[0004] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0005] The present invention is directed to a vehicle and drive mechanism for a vehicle, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0006] With the foregoing in view, the present invention in one form, resides broadly in a skid steer utility vehicle including a) A chassis;

b) At least six hydraulically driven wheels, at least three wheels on each lateral side of the chassis;

c) An engine;

d) An operator position mounted relative to the chassis;

e) A pair of hydraulic circuits, one hydraulic circuit for driving the at least three wheels on a left side of the chassis and one hydraulic circuit for driving the at least three wheels on a right side of the chassis, each hydraulic circuit having:

i. At least one hydraulic pump;

ii. A hydraulic fluid flow divider including a hydraulic fluid outlet port for each of the driven wheels;

iii. A hydraulic motor associated with each of the driven wheels; and the engine of the vehicle powering both hydraulic circuits, and

f) A controller to control hydraulic flow in each hydraulic circuit to provide the vehicle with skid steer capabilities.

[0007] The skid steer utility vehicle of the present invention will preferably be configurable according to intended use. In particular, the vehicle itself may be manufactured as a bare chassis and hydraulic arrangement providing a customer with the ability to define the configuration of the remainder of the vehicle to optimise the vehicle for its intended use. Customers will preferably be able to define components or requirements which can then be added onto the base vehicle. In this way, a single skid steer utility vehicle base can be adapted or configured as required by a customer for intended use. Where a client requires special configuration the manufacturer or assembly team will preferably implement the customisation of the vehicle having regard to whether the customisation will comply with the regulatory requirements for this type of vehicle.

[0008] Preferably, each hydraulic circuit will also include a hydraulic motor mounted relief block including at least one relief valve with reverse flow check located at each hydraulic motor.

[0009] Preferably, each hydraulic circuit will also include at least one differential area relief valve located in association with each hydraulic fluid outlet port and with each hydraulic motor. The differential area relief valves may be incorporated into the hydraulic fluid flow divider and/or the hydraulic motor mounted relief block.

[0010] The skid steer utility vehicle of the present invention has simplified construction since the normal steering, transmission and braking mechanisms are not required. Further, the vehicle has a more reliable operation due to a significant reduction in the number of moving parts when compared to a vehicle having conventionally mechanically driven wheels.

Additionally, the vehicle of the present invention has high manoeuvrability since the vehicle can be turned about the wheels provided on one side of the vehicle and a highly robust construction.

[0011] The chassis of the skid steer utility vehicle of the present invention is preferably unitary in the context that the chassis normally includes an operator position which may be provided in a cabin integrated with the chassis or within a removable module fitted to the chassis relative to which the engine and hydrauhcally driven wheels are mounted. The chassis of the vehicle of the present invention may be manufactured from more than one structural member attached together, normally permanently, typically using welding or bolting for example.

However, it is preferred that the chassis be a unitary chassis. In particular, the chassis of the vehicle will normally have a central portion and a pair of upstanding side rail portions, but the chassis is formed from a single unit. The chassis will preferably define the width of the vehicle and especially the separation distance between the wheels on each lateral side of the vehicle.

[0012] As mentioned above, the cabin is preferably defined by structural members which are themselves mounted relative to or extend from the chassis portion relative to which the hydrauhcally driven wheels are mounted. The chassis normally includes a tray portion extending rearwardly behind the cabin.

[0013] Preferably, the engine is mounted beneath the cabin, typically forwardly of all of the wheels provided on the vehicle. The engine is preferably provided centrally in the cabin.

Typically, a seat area is provided for a driver and the passenger, one on either side of a raised central engine mount. Locating the engine thus may assist with spreading load on the vehicle and increasing stability.

[0014] The operator position and load position will preferably be variable depending on the duty that a particular vehicle may be assigned. It is intended that the vehicle operate as a tractor vehicle with the mechanicals located in and around the unitary chassis. In operation there is not necessarily a "front" or "back" end and the vehicle can travel forwards or backwards. The vehicle tractor may in many cases be fitted with the ability to be loaded with different modules able to be changed out rapidly to carry out particular tasks during a work cycle/day.

[0015] In some embodiments, the operator may not be a person but may be a robotic operator in the form of a controller to control the vehicle.

[0016] Preferably, the cabin has width similar to the preferred rear tray but wider than the chassis.

[0017] Normally, the rear tray is formed on top of the chassis which has at least a pair of elongate side rails, one extending rearwardly on each lateral side of the vehicle and the cabin is mounted above the chassis and the rear tray is mounted relative to the elongate side rails with the rear tray provided above the elongate rails and the hydrauhcally driven wheels mounted on either side of the vehicle to one of the elongate rails of the unitary chassis. [0018] Importantly, the term "chassis" as used in this specification is not limited to a skeleton support structure but it also includes within its scope, the body of the vehicle or any vehicular framework.

[0019] The vehicle of the present invention also includes at least six hydraulically driven wheels, at least three wheels on each lateral side of the chassis. As mentioned, there are preferably three wheels on each lateral side of the chassis mounted to an outer side of each of the elongate chassis rails. Generally, the three wheels on each lateral side are divided into a rearward pair which are substantially adjacent one another on each side and a forward wheel on each side which is separated from the rearward pair of wheels on each side.

[0020] The at least three wheels on each lateral side may be positioned equidistantly longitudinally along the chassis and substantially opposite an opposing wheel on the other lateral side of the vehicle.

[0021] Preferably, each wheel is independently mounted on its own suspension arrangement and is independently driven. The vehicle suitably includes an engine (any type may be used for example internal combustion or electric engine powered by one or more batteries) and the engine of the vehicle will typically drive one or more hydraulic pumps. The one or more hydraulic pumps, in turn typically drive one or more hydraulic motors, normally one hydraulic motor provided for each of the wheels. The drive normally includes a hydrostatic transmission. The drive to each wheel is typically controlled by one or more directional valves in order to thereby steer or reverse the vehicle by driving each of the driven wheels accordingly in forward or reverse. In addition, the vehicle can be skid steered by driving the wheels on one side in a forward direction and either locking the wheels on the other lateral side of the vehicle or driving those wheels in a reverse direction.

[0022] Typically, the suspension arrangement upon which each wheel is independently mounted includes a swinging arm or trailing arm suspension mechanism for each wheel. A spring or other biasing means is provided to bias the suspension arm in a desired orientation. A cushion or other damping member may be provided in addition to the spring or instead of and is preferably interposed between the suspension arm and the chassis in order to control dampen the motion of the suspension arm.

[0023] As mentioned above, each wheel is typically independently mounted and the wheels on one side of the vehicle are typically driven independently from the wheels on the other side. In the preferred embodiment, the engine provided drives two hydraulic pumps, each of which drives preferably by hydrostatic transmission, a hydraulic motor associated with each of the wheels. That is, each wheel is driven by its own hydraulic motor, the hydraulic motors for the three wheels on each side of the vehicle being driven from a respective pump.

[0024] A controller is provided to control hydraulic flow in each hydraulic circuit to provide the vehicle with skid steer capabilities. Controllers of this nature are relatively well-known. In the present invention, there is preferably a single controller to control both hydraulic circuits, both separately and together.

[0025] The vehicle of the present invention also includes a pair of hydraulic circuits, one hydraulic circuit for driving the at least three wheels on a left side of the chassis and one hydraulic circuit for driving the at least three wheels on a right side of the chassis, each hydraulic circuit having at least one hydraulic pump, a hydraulic fluid flow divider including a hydraulic fluid outlet port for each of the driven wheels, a hydraulic motor associated with each of the driven wheels. In a preferred embodiment, a tandem hydraulic pump is provided and the tandem pump will provide hydraulic fluid to each hydraulic fluid flow divider.

[0026] Importantly, the hydraulic fluid flow divider in each of the hydraulic circuits is responsible for dividing the flow of hydraulic fluid between the hydraulic motor associated with each of the driven wheels on each lateral side of the vehicle. Typically, the hydraulic fluid flow divider includes a manifold which is typically a substantially solid block of metal with an entry port for hydraulic fluid. Typically, the entry port is located at one end of the manifold and leads to a bore into the manifold. The end of the bore opposite to the entry port is normally closed using a plug or similar such that hydraulic fluid flowing into the manifold flows out of one or more outlet ports, with an outlet port provided for each of the hydraulic motors associated with each of the driven wheels.

[0027] Each of the outlet ports normally communicates with the same bore. In addition, each outlet port is normally provided with a relief valve with a reverse flow check and preferably, a test port coupling.

[0028] Generally, each outlet port is also provided with a number of attachment points in order to attach a hydraulic conduit relative to the hydraulic fluid flow divider manifold to connect to the hydraulic motors associated with each of the driven wheels.

[0029] Each of the hydraulic motors is preferably provided with a motor mounted relief block. Each of the motor mounted relief blocks is typically a substantially solid metal block into or through which a number of flow pathways are provided. Each of the relief blocks preferably has a first flow path and a second flow path. Therefore, each of the first flow path and the second flow path typically has two ports, generally on different sides of the relief block.

[0030] Each of the first flow path and second flow path are preferably provided with a test port coupling and both flow paths are typically associated with a relief valve with reverse flow check. In some circumstances, both flow paths may be associated with a single relief valve with reverse flow check or a relief valve with reverse flow check can be provided for each of the flow paths.

[0031] The vehicle of the present invention is directed towards ensuring that an equal amount of hydraulic fluid flows into each wheel motor such that each rotates at the same speed. The tandem pump provides an equal amount of flow to each flow divider and each flow divider sends 1/3 of the flow it receives (half of the total flow) to each wheel motor. However, each wheel motor has full pump pressure available, at least theoretically, so is capable of high torque. The provision of the relief valves in association with the flow divider ensures that the hydraulic pump and the system is protected from excess pressure, at both the flow dividers and the motor mounted relief manifolds.

[0032] The valves used in the hydraulic circuits of the present invention can be of any type including but not limited to shuttle valves (permits free flow at the highest operating pressure) and rotary valves. The particular valve configuration and type will normally be chosen according to the requirements of the vehicle.

[0033] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0034] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0035] Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows: [0036] Figure 1 is an isometric view of a skid steer utility vehicle chassis with engine according to a preferred embodiment of the present invention.

[0037] Figure 2 is a front elevation view of the skid steer utility vehicle chassis illustrated in Figure 1.

[0038] Figure 3 is a rear elevation view of the skid steer utility vehicle chassis illustrated in Figure 1.

[0039] Figure 4 is a side elevation view of the skid steer utility vehicle chassis illustrated in

Figure 1

[0040] Figure 5 is a bottom view of the skid steer utility vehicle chassis illustrated in Figure

1.

[0041] Figure 6 is a circuit diagram of the hydraulic system of a skid steer utility vehicle according to a preferred embodiment of the present invention.

[0042] Figure 7A is a portion of the circuit diagram illustrate in Figure 6 corresponding to the hydraulic fluid flow divider according to a preferred embodiment of the present invention.

[0043] Figure 7B is an isometric view of a hydraulic fluid flow divider manifold according to a preferred embodiment of the present invention.

[0044] Figure 7C is a plan view of the manifold illustrated in Figure 7B.

[0045] Figure 7D is a left hand end view of the manifold illustrated in Figure 7B.

[0046] Figure 7E is a front elevation view of the manifold illustrated in Figure 7B.

[0047] Figure 7F is a right-hand end view of the manifold illustrated in Figure 7B.

[0048] Figure 7G is a bottom view of the manifold illustrated in Figure 7B.

[0049] Figure 7H is a partially transparent view from above of the manifold illustrated in Figure 7B showing the internal configuration.

[0050] Figure 8A is a portion of the circuit diagram illustrated in Figure 6 corresponding to the motor mounted relief block according to a preferred embodiment of the present invention.

[0051] Figure 8B is an isometric view from a first side of the relief block illustrated in Figure 8A.

[0052] Figure 8C is an isometric view from a second side of the relief block illustrated in Figure 8A.

[0053] Figure 8D is a plan view of the manifold illustrated in Figure 8B. [0054] Figure 8E is a left hand end view of the manifold illustrated in Figure 8B. [0055] Figure 8F is a front elevation view of the manifold illustrated in Figure 8B. [0056] Figure 8G is a right-hand end view of the manifold illustrated in Figure 8B . [0057] Figure 8H is a rear view of the manifold illustrated in Figure 8B. [0058] Figure 81 is a bottom view of the manifold illustrated in Figure 8B. DESCRIPTION OF EMBODIMENTS

[0059] According to a particularly preferred embodiment of the present invention, a skid steer utility vehicle is provided.

[0060] The skid steer utility vehicle of the preferred embodiment illustrated in the Figures includes a chassis 10 as illustrated in Figures 1 to 5 with six hydraulically driven wheels, three wheels on each lateral side of the chassis (the wheels have been removed for clarity purposes). The vehicle also includes an engine 11 and a cabin 12 mounted relative to the chassis 10.

[0061] The chassis of the skid steer utility vehicle of the present invention is preferably unitary in the context that the chassis 10 normally includes the cabin 12 integrated with the chassis 10 relative to which the engine 11 and hydraulically driven wheels are mounted.

[0062] The chassis 10 is a unitary chassis. In particular, the chassis 10 of the vehicle will normally have a central portion 14 and a pair of upstanding side rail portions 17, but the chassis is formed as a single unit. The chassis 10 will preferably define the width of the vehicle and especially the separation distance between the wheels on each lateral side of the vehicle..

[0063] As mentioned above, the cabin 12 is preferably defined by structural members 13 which are themselves mounted to or extend from the chassis portion relative to which the hydraulically driven wheels are mounted. As illustrated, the chassis 10 includes a central portion 14 extending rearwardly behind the cabin 12. [0064] Preferably, the engine 11 is mounted beneath the cabin 12, typically forwardly of all of the wheels provided on the vehicle. The engine 11 is preferably provided centrally in the cabin 12. Typically, a seat area 15 is provided for a driver and the passenger, one on either side of a raised central engine cover 17. As illustrated, the cabin 12 is wider than the central portion of the unitary chassis 14.

[0065] Normally, the chassis includes a pair of elongate rails 17, one extending rearwardly from the cabin 12 on each lateral side of the vehicle and the cabin 12 and the rear tray (not shown) is mounted relative to the chassis and particularly the elongate rails 17 and the hydraulically driven wheels mounted on either side of the vehicle to one of the elongate rails 17 as indicated but the circular pattern of holes 18 that mount each of the wheels directly to the rails 17.

[0066] Importantly, the term "chassis" as used in this specification is not limited to a skeleton support structure but it also includes within its scope, the body of the vehicle or any vehicular framework.

[0067] Although removed in the Figures for clarity, the vehicle of the present invention also includes at least six hydraulically driven wheels, three wheels on each lateral side of the chassis 10. As mentioned, there are three wheels on each lateral side of the chassis 10 mounted to an outer side of each of the elongate chassis side rails 17 of the unitary chassis 10. Generally, the three wheels on each lateral side are divided into a rearward pair which are substantially adjacent one another on each side and a forward wheel on each side which is separated to a slightly larger degree from the rearward pair of wheels on each side.

[0068] Preferably, each wheel is independently mounted on its own suspension arrangement is independently driven. The vehicle suitably includes an internal combustion engine or electric engine powered by one or more batteries and the engine of the vehicle will typically drive one or more hydraulic pumps. The one or more hydraulic pumps, in turn typically drive one or more hydraulic motors, normally one motor provider for each of the wheels. The drive normally includes a hydrostatic transmission. The drive to each wheel is typically controlled by valve means in order to thereby steer or reverse the vehicle by driving each of the driven wheels accordingly in forward or reverse. In addition, the vehicle can be skid steered by driving the wheels on one side in a forward direction and either locking the wheels on the other lateral side of the vehicle or driving those wheels in a reverse direction.

[0069] Typically, the suspension arrangement upon which each wheel is independently mounted includes a swinging arm or trailing arm suspension mechanism for each wheel. A spring or other biasing means is provided to bias the suspension arm in a desired orientation. A cushion or other damping member may be provided in addition to the spring or instead of and is preferably interposed between the suspension arm and the chassis in order to control dampen the motion of the suspension arm.

[0070] As mentioned above, each wheel is typically independently mounted on the chassis with the wheels on one side of the vehicle are typically driven independently from the wheels on the other side. In the preferred embodiment, the engine provided drives to hydraulic pumps, each of which drives preferably by hydrostatic transmission, a hydraulic motor associated with each of the wheels. That is, each wheel is driven by its own hydraulic motor, the hydraulic motors for the three wheels on each side of the vehicle being driven from a respective pump.

[0071] A controller is provided to control hydraulic flow in each hydraulic circuit to provide the vehicle with skid steer capabilities. Controllers of this nature are relatively well-known.

[0072] As illustrated in Figure 6, the vehicle of the preferred embodiment also includes a pair of hydraulic circuits 19, one hydraulic circuit 19 for driving the three wheels on a left side of the chassis 10 and one hydraulic circuit 19 for driving the three wheels on a right side of the chassis 10. Each hydraulic circuit has a hydraulic pump 20, a hydraulic fluid flow divider 21 including a hydraulic fluid outlet port for each of the driven wheels, and a hydraulic motor 22associated with each of the driven wheels.

[0073] The steering of the vehicle is controlled by a controller to control the direction of hydraulic flow in each hydraulic circuit to change the direction of the wheels, to provide the vehicle with skid steer capabilities.

[0074] An example of a preferred hydraulic fluid flow divider 21 is provided in Figures 7 A to 7H. Importantly, the hydraulic fluid flow divider 21 in each of the hydraulic circuits is responsible for dividing the flow of hydraulic fluid between the hydraulic motor associated with each of the driven wheels on each lateral side of the vehicle. Typically, the hydraulic fluid flow divider includes a manifold 24 which is typically a substantially solid block of metal with an entry port 25 for hydraulic fluid. Typically, the entry port 25 is located at one end of the manifold 24 and leads to a bore 26 through the manifold 24. The end of the bore opposite to the entry port 25 is normally closed using a plug 27 or similar such that hydraulic fluid flowing into the manifold flows out of one or more outlet ports 28, with an outlet port 28 provided for each of the hydraulic motors 22 associated with each of the driven wheels. [0075] Each of the outlet ports 28 normally communicates with the bore 26. As illustrated, each outlet port 28 is normally provided with a relief valve 29 with a reverse flow check and preferably, a test port coupling 30.

[0076] Generally, each outlet port 28 is also provided with a number of attachment points 31 in order to attach a hydraulic conduit relative to the hydraulic fluid flow divider manifold 24 to connect to the hydraulic motors associated with each of the driven wheels.

[0077] Preferably, each hydraulic circuit will also include a hydraulic motor mounted relief block 23 including at least one relief valve 29 with reverse flow check located at each hydraulic motor 22. An example of a preferred hydraulic motor mounted relief block 23 is provided in Figures 8A to 81.

[0078] Each of the motor mounted relief blocks 23 is typically a substantially solid metal block into or through which a number of flow pathways are provided. Each of the relief blocks 23 preferably has a first flow path ("A") and a second flow path ("B"), the first flow path for flow of hydraulic fluid in a first direction and the second flow path for hydraulic fluid flow in a second direction. Therefore, each of the first flow path and the second flow path typically has two ports 33 A, 33B and 34A, 34B, generally on different sides of the relief block 23.

[0079] Each of the first flow path A and second flow path B are preferably provided with a test port coupling 30 and both flow paths are typically associated with a relief valve 29 with reverse flow check. In some circumstances, both flow paths may be associated with a single relief valve with reverse flow check or a relief valve with reverse flow check can be provided for each of the flow paths.

[0080] Preferably, the relief valves 29 used in each hydraulic circuit are differential area relief valves. The relief valves of the hydraulic fluid flow divider 21 are preferably located to relieve pressure in relation to each hydraulic fluid outlet port 28 of the hydraulic fluid flow divider 21 and each hydraulic motor 22. The differential area relief valves may be incorporated into the hydraulic fluid flow divider 21 and/or the hydraulic motor mounted relief block 23 as illustrated.

[0081] In the present specification and claims (if any), the word 'comprising' and its derivatives including 'comprises' and 'comprise' include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0082] 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, the appearance 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.

Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0083] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims

A skid steer utility vehicle including:

a) A chassis;

c) An engine;

d) A cabin mounted relative to the chassis;

i. At least one hydraulic pump;

iii. A hydraulic motor associated with each of the driven wheels; and engine of the vehicle powering both hydraulic circuits, and

A skid steer utility vehicle as claimed in claim 1 wherein each hydraulic circuit includes a hydraulic motor mounted relief block including at least one relief valve with reverse flow check located at each hydraulic motor.

A skid steer utility vehicle as claimed in claim 1 or claim 2 wherein each hydraulic circuit includes at least one differential area relief valve located in association with each hydraulic fluid outlet port and with each hydraulic motor.

A skid steer utility vehicle as claimed in claim 3 wherein the at least one differential area relief valve is incorporated into the hydraulic fluid flow divider.

A skid steer utility vehicle as claimed in claim 3 when dependent on claim 2 wherein the at least one differential area relief valve is incorporated into the hydraulic motor mounted relief block.

A skid steer utility vehicle as claimed in any one of the preceding claims wherein the chassis is unitary such that the chassis includes an operator position which is provided in a cabin integrated with the chassis

A skid steer utility vehicle as claimed in any one of claims 1 to 5 wherein the chassis is unitary with an operator position which is provided in a cabin provided within a removable module fitted to the chassis relative to which the engine and hydraulically driven wheels are mounted.

8. A skid steer utility vehicle as claimed in any one of the preceding claims wherein the chassis has a central portion and a pair of upstanding side rail portions.

9. A skid steer utility vehicle as claimed in any one of the preceding claims wherein the engine is mounted beneath the cabin, forwardly of all of the wheels provided on the vehicle.

10. A skid steer utility vehicle as claimed in any one of the preceding claims wherein a rear tray is formed on top of the chassis which has at least a pair of elongate side rails, one extending rearwardly on each lateral side of the vehicle and the cabin is mounted above the chassis and the rear tray is mounted relative to the elongate side rails with the rear tray provided above the elongate rails and the hydraulically driven wheels mounted on either side of the vehicle to one of the elongate rails of the unitary chassis.

11. A skid steer utility vehicle as claimed in any one of the preceding claims wherein the at least three wheels on each lateral side are positioned equidistantly longitudinally along the chassis and substantially opposite an opposing wheel on the other lateral side of the vehicle.

12. A skid steer utility vehicle as claimed in any one of the preceding claims wherein each

wheel is independently mounted on its own suspension arrangement and is independently driven.

13. A skid steer utility vehicle as claimed in claim 12 wherein each wheel drive includes a

hydrostatic transmission.

14. A skid steer utility vehicle as claimed in claim 12 or 13 wherein each wheel drive is

controlled by one or more directional valves in order to thereby steer or reverse the vehicle by driving each of the driven wheels accordingly in forward or reverse.

15. A skid steer utility vehicle as claimed in any one of claims 12 to 14 wherein the suspension arrangement upon which each wheel is independently mounted includes a swinging arm or trailing arm suspension mechanism for each wheel with a spring or other biasing means is provided to bias the suspension arm in a desired orientation.

16. A skid steer utility vehicle as claimed in any one of claims 12 to 15 wherein the suspension arrangement includes a cushion or other damping member interposed between the suspension arm and the chassis in order to control dampen the motion of the suspension arm.

17. A skid steer utility vehicle as claimed in any one of the preceding claims wherein the

hydraulic fluid flow divider in each of the hydraulic circuits is responsible for dividing the flow of hydraulic fluid between the hydraulic motor associated with each of the driven wheels on each lateral side of the vehicle.

18. A skid steer utility vehicle as claimed in any one of the preceding claims wherein the

hydraulic fluid flow divider includes a manifold block with an entry port for hydraulic fluid and one or more outlet ports connected by a bore, with an outlet port provided for each of the hydraulic motors associated with each of the driven wheels.

19. A skid steer utility vehicle as claimed in claim 18 wherein each of the outlet ports

communicates with the bore and each outlet port is provided with a relief valve with a reverse flow check.

20. A skid steer utility vehicle as claimed in claim 2 wherein each of the hydraulic motors is provided with a motor mounted relief block having a first flow path and a second flow path and both flow paths are associated with a relief valve with reverse flow check.