This invention relates to a skid steer loader and in particular to a drive system for such a vehicle.

Skid steer loaders are vehicles which have two ground engageable wheels on each side of the vehicle which is steerable by causing the wheels on one side to rotate more quickly than the other so that in effect some of the wheels skid.

Such vehicles are extremely popular for applications in construction, mining and industries involved in major or minor earth works.

One problem to which this invention is directed relates to the difficulty experienced if the engine or drive train of an existing machine breaks down.

If the vehicle is being used in a production environment, the loss of the unit for any extended period can cause severe hardship.

Further, by reason of the overall small size of the vehicle, it can be difficult to obtain ready access to the engine or other parts of the drive train.

It is an object of this invention to provide a design whereby the costs of manufacture of such a vehicle can be kept lower than has hitherto been the case.

It is a further object of this invention to provide an arrangement for a vehicle of this type in which the centre of gravity can be kept very low compatible with the need for economy of manufacture and ease of access for maintenance purposes.

In accord with this invention there is proposed a skid steer vehicle comprising a frame, wheels providing ground support on each side of the vehicle and an engine pod including an engine adapted to be slidably removable from between the respective wheels on each respective side

of the vehicle, the engine including an interengaging mechanical drive coupling adapted to effect the mechanical rotational drive of the said wheels.

In preference there are located on a first side of the vehicle two ground engageable wheels coupled through a sprocket chain drive to a common drive location which is aligned to extend along and be adjacent to the first side, and there are located on a second side of a vehicle which is the opposite side to the said first side, two ground engageable wheels coupled through a sprocket and chain drive to a common drive location which is aligned to extend along and be adjacent to the second side on the second side.

By having a sprocket and chain drive along each respective side of the vehicle, this allows firstly an interengaging mechanical drive coupling to be located at a much more convenient location than has hitherto been achievable and this inherently then allows for the location of the engine pod together with the bulky elements which make up the main mass contributing to the weight of the vehicle, to be located at a very low centre of gravity position relative to the remainder of the vehicle.

In one preferred instance, the interengaging mechanical drive coupling is located at a most forward position and is aligned with the forward two side wheels and in another case the mechanical drive coupling is located midway between the respective side wheels but is provided by in each case a hydraulic motor which is connected to the remaining elements in the engine pod only by hydraulic pipes.

Once again therefore this arrangement provides for a very significant improvement in the overall locations of the elements while at the same time allowing for ready rear removal of the engine pod. This then, subject to the relatively minor either withdrawal of hydraulic motors from an interengaging relationship or a withdrawal of the interengaging mechanical drive coupling, and obviously electrical fittings and incidental connectors, allows within a few minutes, all of the majority of the working components of the vehicle to be accessible or to be replaced by an equivalent engine pod brought in as a replacement.

The advantage of this feature is huge in that if an operator has the need, a fully serviced replacement engine pod can be kept on hand, the cost of which is significantly less than the overall vehicle and in the event that an operator has a number of these vehicles it then becomes economic to have such a replacement pod on hand to ensure that a skid steer loader will be out of service even with major mechanical breakdown, only for a very short time while the engine pod is replaced.

This service can be provided either by an external support facility or by kept spares by the operator.

For a better understanding of this invention it will now be described with the assistance of drawings in which:

FIG. 1 is a schematic plan view of a skid steer loader according to the first embodiment,

FIG. 2 is a side elevation of a skid steer loader according to a second embodiment showing in dotted outline the location of the engine pod together with the attached engine and drive elements, and

FIG. 3 is a schematic plan view again of the second embodiment.

Referring in detail to the first embodiment as illustrated in FIG. 1 , there is a skid steer loader 1 which incorporates a body frame 2 which includes a cabin which is not specifically shown and sides 4 and 5. Between sides 4 and 5 is a space 6 in which a drive engine 7, a transmission 8 and slidabiy engageable coupling 9 which includes interengaging splines are located on a separable engine pod. The pod is removable from the universal coupling 10 and the differential transmission 11 by withdrawal in the direction 12 which is to the rear of the skid steer loader. This is to say the elements 7, 8 and 9 are collectively supported on lowermost rails 13 and 14 which are simply shown in dotted outline, such that they can be removed conveniently from time to time by sliding from the operating position shown, out past the sides 4 and 5 and through a rear access door 15.

The drive from differential 11 is split so as to be able to differentially drive through brake discs 16 and 17 sprockets 18 and 19 which each constitute a common drive location.

Sprockets 18 and 19 are coupled to the dual sprockets 20 and 21 by a chain 22 and 23 and a second of these sprockets is then further coupled through the chain 24 in the one case and 25 in the other to a rear sprocket 26 in the one case and 27 in the other.

The respective sprockets 20 and 21 drive side wheels 28 and 29 and then through the chains 25 and 24 the wheels 30 and 31.

The side wheels in the first instance 28 and 30 are supported in mutual parallel alignment the one 28 being located at a forward position and the other 30 located at a rearward position with respect to the vehicle 1 providing ground support on the said side of the body frame 2 of the vehicle 1.

Likewise with wheels 29 and 31 , these are also in mutual parallel alignment, the one namely 29 located at a forward position and the other 31 located at a rearward position with respect to the vehicle 1 providing ^' ground support on a first side of the body frame 2 of the vehicle 1.

Each of the wheels 28, 29, 30 and 31 is supported so that they are non- steerable and are adapted to be driven in a controlled rotational manner by the appropriate chain connection.

Steering as is conventional in vehicles of this type is achieved by differentially driving the wheels on one side at a different speed with respect to the wheels on the other side and this is achieved in this case by selectively operating the respective brake either 16 or 17.

As will now be seen by the physical arrangement of the parts, the location of the differential 11 can be at any selected height regardless of the respective height of the axes of the wheels 28, 29, 30 and 31 simply because the common drive location defined by sprockets 18 and 19 can be located lower than any alignment with any plane defined by the axes of the respective wheels 28, 29, 30 and 31.

This allows for a very low location of the main weight contributing elements of the engine pod incorporating the engine 7 and the transmission 8.

We now refer to the second embodiment which is described more specifically in FIGS. 2 and 3.

In this case, the vehicle 32 includes a body frame 33 which includes upstanding sides 34 and 35 and a base floor 36 which thereby provides in effect a channel into which the engine pod can be moved.

The floor 36 can in this configuration be located significantly lower than any plane defined by the respective axes of each of the side wheels 37, 38, 39 and 40.

As with the first embodiment, the respective wheels 37 and 38 are each located on one side of the vehicle and in mutual parallel alignment, the wheel 37 being located at a forward position with respect to the vehicle and the wheel 38 at a rearward position with respect to the vehicle.

In like manner the wheels 39 and 40 are in mutual parallel alignment, 39 being positioned in a forward position and 40 in a rearward position and in each case these are supported by appropriate stub axles and bearings shown typically at 41 , 42, 43 and 44.

On an inner side in respect of each of these stub axles and support bearings is located a sprocket these being shown respectively at 45, 46, 47 and 48.

The respective sprockets then are coupled at a common medial location by chains which respectively engage one of the dual sprockets supported by housing 49 and 50.

A surrounding cover plate 51 on the one side and 52 on the other help to seal off each chain transmission assembly so that these can be kept in a constant oil bath and while not specifically shown, chain tensioning devices can be incorporated to also run within a constant oil bath and

therefore can be expected to have a long life in a relatively dust-free and compatible environment.

Drive access to this chain sprocket combination in each case is achieved through a male and female spline assembly at 53 and 54 such that the respective hydraulic drive motor 55 in the one case and 56 in the other can be either fixedly secured to the inner wall so that its male spline can operably engage the respective drive sprockets or in the event that an engine pod is to be removed, the hydraulic drive motors can be removed from their attached position, withdrawn from their interconnection between the respective splines and then while the respective hydraulic pipes still connect the motors, be left loose on the pod so that they can be withdrawn with the pod as appropriate.

The engine pod 57 is constituted by an engine 58 and a dual hydraulic pump assembly 59.

The pod 57 overall is shown only in schematic outline but includes all of the engine elements including a generator, an appropriate cooling radiator for the engine which is located at a rearward most position, and respective ancillary parts.

The engine pod 57 can be withdrawn from its operating position which is as shown in FIG. 3, either partially or fully so that it can be either available for easy access for maintenance or it can be replaced entirely so that within a few minutes, a replacement pod including a replacement engine and hydraulic pump and hydraulic motors all can be in place.

Having the split drive chain sprocket assemblies allows for the location of the drive to the side wheels to be located in a most appropriate position. The engine and attached hydraulic reservoirs and hydraulic pumps can be located at a lowest most position to assist in stability of the vehicle.

The heavier elements are located toward the rear of the vehicle so as to provide some counteracting weight to any load that might be held in the bucket 59.

The relative height of the elements can be best seen by reference to the dotted outline shown in FIG. 2 where the location of the engine 58 can be seen to be very close to the floor 36 and likewise the tandem hydraulic pump 59 can be seen to be in also a very low position.

By judicious location of the various elements, it has been found possible that the overall centre of gravity of the skid steer loader overall can be kept very low particularly the base of the engine pod can be kept below the plane defined by the axes of the respective wheels 37, 38, 39 and 40.

The arrangement described provides a significant improvement in respect of stability of a skid steer loader and by having a removable engine pod allows for significant advantages in relation to either access or replacement of the engine or other drive elements.