GRANT WILSON AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT "IMPROVEMENTS TO GRAIN FIELD BINS" The following statement is a full description of this invention, including the best method of performing it known to us:- -2 IMPROVEMENTS TO GRAIN FIELD BINS Field of the Invention This invention relates to improvements in field bins used for holding grain during harvesting. In particular, it relates to improvements in means for raising and 5 lowering the containers of field bins to permit transport thereof. Background to the Invention "Field bins" have been used for many years on farms in grain growing areas. They are often simply described as "mobile grain silos". Essentially, the field bin includes a bin mounted on a frame which frame is provided with wheels on stub 10 axles to enable transport from one place to another, usually while the bin is empty, so that the field bin can be used as a temporary silo or storage facility during harvesting. In the transporting configuration, the wheels mounted on stub axles mounted on a frame contact the ground to permit the field bin to be towed to a site. In use for holding grain or seeds, the stub axles on which the wheels are mounted typically are 15 raised so that the wheels are out of contact with the ground and the framework on which the bin is mounted rests on the ground thereby providing a stable base for the bin and minimising ground pressure. Manually lifting or lowering the stub axles on field bins by using levers is the typical process. However, that has its risks as the operator may be struck by one 20 of the levers causing injury, sometimes very serious injury. Additionally, a field bin is often provided with power take off apparatus so that an auger mounted within the bin can be used to deliver grain out of the bin. The power take off apparatus is usually connected by a power take off shaft provided on a tractor. The connection of a power take off shaft is a manual task which can also give 25 rise to injury. Additionally, back injuries can occur whilst manually lifting and/or manoeuvring field bins in order to connect them to the drawbar of a tractor. Further, a significant amount of time can be spent in repositioning of field bins during harvesting, which can occur frequently. 30 It is one of the objects of the present invention to alleviate some of the foregoing problems. 16/01/09jb17744 complete innovation patent spccification.doc,2 -3 Summary of the Invention According to one aspect of the invention there is provided an apparatus for automatically raising or lowering a field bin, said apparatus including a bin for receiving grain or seeds or other material, a framework supporting said bin, a 5 plurality of wheels each of which is rotatably mounted on a stub axle, each said stub axle being pivotally mounted on said framework in an offset manner via an arm or plate fastened to the stub axle and a shaft, said shaft being pivotally received at or adjacent the free end thereof within a bearing or bearing assembly fixed on said framework, and means permitting said framework to move vertically relative to the 10 ground on which the field bin is situated in reaction to the addition of material to or removal of material from said bin. Said means may include a force absorbing means mounted between each said stub axle or each said arm or plate and the framework. Preferably, said means includes at least one compression spring mounted between each of the arms or plates to which each of the stub axles are fixed and the 15 framework. Alternatively, said means may include at least one gas strut, hydraulic cylinder, or gas spring mounted in a similar manner. Alternatively, said means may include at least one leaf spring or at least one air bag. Preferably each of said means is adjustable so that movement of the framework commences when a predetermined load has been added to the bin. Such adjustment may involve altering the 20 compression in a compression spring, gas strut or gas spring when it is not under load. Another aspect of the invention relates to the mounting of the pull arm by which the field bin may be connected to a hauling device such as a tractor or truck. According to this aspect of the invention there is provided a pull arm pivotally 25 mounted to the framework of a field bin as aforesaid, said pull arm being restrained in upward and downward movement by at least one of a selection of one or more compression springs, gas springs, tension springs, or gas struts pivotally mounted to said pull with the other end being mounted fixedly to the framework. Preferably the pull arm is pivotally mounted to said framework and is restrained in upward and 30 downward movement by a plurality of compression springs pivotally mounted to the pull and at their other ends mounted to a bar fixed to the framework. 04/08/09,dh17744 -complete innovation patent specification - rck,3 -4 It is anticipated that the invention provides advantages including the reduction or elimination of manual work involved in positioning and setting up the field bin. An operator should have to do no more than drive to the work location on a tractor towing the field bin, disembark from the tractor, and leave the area, either 5 with the tractor still hitched to the field bin or unhitch the tractor and field bin and then drive off. Compression springs or gas springs are believed to offer advantages in providing better performance than is the case with tension springs. Description of Preferred Embodiment 10 In order that aspects of the invention may be more clearly understood, a preferred embodiment is now described with reference to the accompanying drawings in which: Figure 1 is a partial view of a typical current axle lowering arrangement with the field bin being in the lowered position; 15 Figure 2 is a partial view of an embodiment of the invention showing a mechanism for raising and lowering wheel and associated stub axle; and Figure 3 is a partial view of the pull bar of a field bin according to the present invention. In Figure 1 the numeral 12 designates portion of the framework of a field 20 bin. In almost every case of existing field bin designs the means for raising and lowering the field bin comprises a plurality of movable stub axle mounted wheels. In each such instance a lever 14 is fixed at right angles to a shaft 16 rotatably mounted within a greased bush 18 fixed to framework 12. At the opposite end of shaft 16 is fixed a crank arm 20 at right angles to shaft 16. From the other end of crank arm 20 25 is disposed a stub axle 22 and wheel 24. In practice to raise the bin the lever 14 is rotated clockwise (to the right in the drawing) to in turn force the stub axle 22 and wheel 24 downwards so that the wheel 24 contacts the ground with enough force to thereby force the field bin including bin 26 upwards. The lever is then attached to a retainer 28 to lock the field 30 bin in transport position. This process is repeated for each of the other wheels on which the field bin is to be moved. To lower the field bin the reverse procedure is performed. As will be appreciated, considerable physical effort may be required to 16/01/09jb17744 complete innovation patent specification.doc,4 -5 move lever 14 from one position to another. In many instances commercial manufacturers use tension springs such as illustrated here as numeral 30, mounted between the crank arm 20 and the framework 12 at point 29, to assist in reducing the force required to move the lever 14 in the interests of operator safety. The pull bar of 5 conventionally manufactured field bins which connects to tractors or transporting vehicles is always a fixed structure. The embodiment shown in Figure 2 is meant to directly replace the mechanism shown in Figure 1. A shaft 32 is rotatably mounted through a pillar block bearing 34 on the framework 12 of the field bin and side flange block 36 bearing 10 fixed on the inner side of framework 12. On the inner end of shaft 32 is attached an arm 38 which is similarly oriented as, and is the same or similar to, existing crank arms used in commercially manufactured bins. A compression spring 40 is mounted between crank arm 38 via plate 42 and the field bin frame 12. When the bin (not shown) is loaded to a specified capacity the weight causes the field bin to lower itself 15 to the ground by compressing the compression spring 40. The point at which this occurs can be predetermined by an adjuster nut 41 which can either be screwed down along thread 45 on to the compression spring 40 to increase the pre-existing compression in the compression spring or away from the compression spring to reduce the compression therein and consequently render it more sensitive to loading 20 of material into the bin. Conversely when the bin is emptied the compression spring is released from compression and forcibly lowers the stub axle 22 and wheel 24 thereby raising the field bin, while still being attached to a tractor draw-bar. This also permits the power take off shaft of the bin to remain connected to the power take off of the tractor. 25 The redesigned pull system shown in Figure 3 contains a common A-frame pull mount 44 which is pivotally mounted to the frame 12 of a field bin at points 46,48. Also provided are a plurality of compression springs 50 pivotally mounted on greased bushes on the A-frame pull bar at points 52,54, and to a bar 56 fixed between uprights 58,60 of framework 12. When the field bin is in the transport position, i.e., 30 with the wheels lowered and riding on the ground the pull is slightly inclined upwardly and is restrained from dropping down to a substantially vertical orientation. When the field bin is lowered into the material receiving position the pull inclines 16/01/09jb 17744 complete innovation patent specification.doc,5 -6 further upwardly being still attached to the tractor draw-bar. The combination of the integers depicted in Figures 2 and 3 and described herein allow the field bin to raise and lower in reaction to unloading or loading of the bin while still connected to a tractor. The compression springs 50 may be adjustable in the same manner as the 5 compression spring 40 in Figure 2. It is to be understood that the invention may embrace many further modifications as would be readily apparent to persons skilled in the art and which would be deemed to reside within the broad scope and ambit of the invention. The preferred embodiment described above is by way of example only and is not to be 10 considered as limiting. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or 15 group of integers or steps. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form or suggestion that the prior art forms part of the common general knowledge in Australia. 20 16/0I/09jbl7744 complete innovation patent specification.doc,6