Referring now to Figure 1, a known type of shear grab 10 is shown. The grab 10 comprises a tined base structure 12 comprising a plurality of parallel tines 12' extending from a cross-bar 13. Both the plurality of tines 12'and the cross bar 13 are generally formed from steel or a similar high strength material suitable for use in the manufacture of farm machinery, which is subject to substantial operational loads and adverse operating conditions. At either end of the cross-bar 13, a respective support arm 15 extends upwardly at substantially 90° to the axis of the tines 12'. The base structure 12 is pivotally mounted mid-way along the arms 15 below a grab head 14.

The grab head 14 comprises a pair of side walls 17 to which the arms 15 are pivoted about respective axes 18. A lid 19 joins the upper edges of the side walls 17, the lid having a serrated front edge 19'. Between at least one of the otherwise free ends of the arms 15 and the corresponding upper corner of the grab head 14, a double-acting hydraulic cylinder 21 having oil feed ports A and C is located.

The double acting hydraulic cylinder 21 is operable to pivot the grab head 14 relative to the base structure 12. In use, the base structure 12 can be considered to act as a lower jaw, while the grab head 14 acts as an upper jaw hinged thereto, which can be closed together in order to"bite off'large blocks or bales of silage or the like from a larger volume thereof. In use, the grab head 14 is opened fully away from the base structure 12, the tines 12'of which are then slid under a suitable portion of silage to be removed, much like the blades (not shown) of a forklift truck (not shown) are driven beneath an object to be lifted. The double acting hydraulic cylinder 21 is then actuated in reverse, in order to close the grab head 14 over the base structure 12.

As the grab head 14 closes towards the base structure 12, the serrated front edge 19' cuts through the silage in its path, thereby severing a bale or block (not shown) of silage from the larger volume. The block is consequently enclosed between the base structure 12 and the grab head 14. The shear grab 10 can then be lifted and transported as required, and the bale of silage ejected therefrom at a desired location, for example a cattle feed-shed (not shown). In order to eject the bale, the grab head 14 is opened fully, and the shear grab 10 tipped forward to enable the bale to slide off the tines 12'.

The grab 10 is arranged to be mounted on the front or rear of a tractor or like vehicle with the opening and closing of the base structure 12 relative to the grab head 14 being controlled from the cab of the vehicle through extending and retracting the cylinder 21. Actuation of an arm (not shown) or alternative linkage (not shown) of the tractor to which the shear grab 10 is mounted enables the shear grab 10 to be tilted in order to eject a bale of silage or the like, as hereinbefore described.

These grabs can only handle solid type materials and are not suitable to carry powder or granule type materials. However, it is a common practise in animal farming to use animal feed comprising silage mixed with other fine protein materials. To a farmer, this means such a prior art shear grab as well as another suitable component must be employed to handle such feed. This adds considerable time to feed management as well as adding considerably to the time and material costs involved.

It is therefore an object of the present invention to mitigate the above mentioned problems with prior art shear grabs.

It will however be immediately understood by a person skilled in the art that the configuration of the above described prior art shear grab 10 is merely one preferred arrangement which may be utilised in order to handle silage or the like, and that

many variations on the basic principle exist. For example, the method by which the grab head 14 is hinged relative to the base structure 12, via the pair of support arms 15, could be altered so long as the grab head 14 is rendered movable relative to the base structure 12. Thus the prior art shear grab 10 described hereinabove is to be taken as an exemplary model only, and the invention as described and claimed hereinafter may be utilised with a wide variety of shear grabs (not shown), as will become apparent from the following detailed description of the invention.

Accordingly, the present invention provides a shear grab comprising a grab head; a tined base mounted to the grab head such as to be moveable between an open position distal the grab head, and a closed position in which the base effectively closes the grab head; and a flap moveable between a first position occluding the times of the base and a second position exposing the tines of the base.

Preferably, the grab head is moveable relative to the base by means of at least one first fluid powered ram.

Preferably, the flap is moveable relative to the base by means of at least one second fluid powered ram.

Preferably, the at least one first fluid powered ram is in parallel fluid communication with the at least one second fluid powered ram such that, when the first fluid powered ram has moved the base into the open position, further fluid pressure applied to the first fluid powered ram is transferred to the second fluid powered ram such as to move the flap into the second position.

Preferably, the at least one first fluid powered ram is a double acting ram having a first side to which pressurised fluid is pumped in order to move the base to the open position, and a second side to which pressurised fluid is pumped in order to move

base to the closed position, the at least one second fluid powered ram being in parallel fluid communication with the first side of the first fluid powered ram.

Preferably, the at least one second fluid powered ram is a single acting ram having an inlet port to which pressurised fluid is pumped in order to move the flap to the second position.

Preferably, the at last one second fluid powered ram is spring biased such as to urge the flap into the first position.

Preferably, the flap is located substantially within the grab head when in the second position.

Preferably, the grab head comprises a pair of opposed side walls and a top extending therebetween, such that when the flap is in the first position and the base is at or adjacent the closed position, at least the flap and the side walls form an enclosure capable of retaining a flowable material.

Preferably, the shear grab further comprising a pressurised fluid circuit having a pair of parallel pressurised fluid conduits via which, in a single operation, pressurised fluid may be simultaneously pumped to the at least one first fluid powered ram to move the base towards the open position, and to the at least one second fluid powered ram to move the flap towards the second position.

Preferably, the pressurised fluid circuit comprises a further pressurised fluid conduit via which pressurised fluid may be independently pumped to the at least one first fluid powered ram such as to move the base towards the closed position.

Preferably, the pressurised fluid circuit is arranged such that when pressurised fluid is pumped through the further pressurised fluid conduit, the pumping of pressurised

fluid through the pair of parallel pressurised fluid conduits is ceased, thereby enabling the flap to be moved into the first position.

Preferably, the flap is pivotally mounted to the base about an axis which is substantially perpendicular to the longitudinal axes of the tines.

Preferably, the base further comprises a pair of oppositely disposed support arms to which the grab head is pivotally mounted.

Preferably, the actuating pressure of the at least one first fluid powered ram, in moving the base towards the open position, is less than that of the at least one second fluid powered ram.

Preferably, each of the first and second fluid powered rams are hydraulically actuated.

Preferably, each support arm comprises a first and a second end between which the grab head is pivotally mounted, the tines projecting from adjacent the first end, and the at least one first fluid powered ram being operatively connected between the second end and the grab head.

As used herein, the term"grab head"is intended to mean a hollow or recessed structure which is adapted to act like an upper jaw which in use is hinged upwardly away from a base, which base itself acts as a lower jaw, the grab head then being positioned about a quantity of material such as silage or the like, and hinged closed against the base such as to effectively bite off that quantity of material for transport to a desired location.

As used herein, the term"tined"is intended to mean having a plurality of prongs, which are narrow in width relative to the length thereof, and which are generally

arranged in parallel to one another, and used to lift and manoeuvre material in a fork- like manner.

As used herein, the term"flap"is intended to mean a surface or plate, preferably planar, which is substantially impermeable to flowable material such as powder or granules.

As used herein, the term"ram"is intended to mean a cylinder having a piston movable therein by pumping a pressurised fluid into the cylinder, the piston being connected to a rod which projects outwardly of the cylinder in order to be capable of imparting motion to, for example, a linkage or the like.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 illustrates a prior art shear grab; Figure 2 illustrates a shear grab according to a preferred embodiment of the invention; Figure 3 illustrates a tined base structure employed with the shear grab of Figure 2; Figure 4 illustrates a side view of the shear grab of Figure 2 including a hydraulic circuit, and in addition showing a flap which forms part of the invention, the flap being in a second, retracted position; Figure 5 is a side view of the shear grab of Figure 2 with the flap shown in a first, extended position; and

Figure 6 is a sectioned side elevation illustrating the preferred means of connection between the flap, shown in the retracted position, and a hydraulic cylinder operable to extend and retract the flap.

Referring now to Figures 2 to 6 of the accompanying drawings, a shear grab 20 according to a preferred embodiment of the invention is shown. The grab 20 is very similar to the prior art grab 10 described above, and thus like components have been accorded like reference numerals, and unless otherwise stated, perform a like function. As in the prior art, the grab 20 comprises a base in the form of a base structure 12 having a plurality of tines 12'secured to a crossbar 13, the base structure 12 being pivotally mounted below a grab head 14. The base structure 12 further includes a pair of oppositely disposed support arms 15 to which the grab head 14 is pivotally mounted about respective axes 18. The grab head 14 could of course be mounted to the base structure 12 in any other suitable fashion which permits the necessary relative movement therebetween. In the preferred embodiment illustrated, the grab 20 is provided with a first double acting hydraulic cylinder 21 having a first side defined by a first port A through which pressurised fluid is pumped in order to move the grab head 14 to an open position distal the base structure 12, thereby permitting access to the interior of the grab head 14. The first cylinder 21 is further provided with a second side defined by a second port C to which pressurised fluid is pumped in order to extend the length of the first cylinder 21, and thus move the grab head 14 to a closed position in which the tines 12'of the base structure 12 effective close off the interior of the grab head 14.

Again, the grab 20 is mountable on a vehicle (not shown) in a conventional manner and as such the present specification does not provide a detailed description of the mounting mechanism. In brief, the grab 20 is preferably mounted to a conventional articulated arm or arms (not shown) of the vehicle, for example a tractor (not shown), and may be so mounted by any suitable means, for example a quick hitch coupling (not shown) or the like. The grab 20 must also be connected to the

hydraulic circuitry (not shown) of the vehicle, or indeed an independent hydraulic supply (not shown), in order to provide power to the grab 20, in particular to supply pressurised fluid to ports A and C as required. Again this is an entirely conventional operation, and is not therefore described herein.

The grab 20 of the preferred embodiment has, in addition to the above known features, a flap 30 extending across the width of, and movable relative to, the base structure 12, so that the flap 30 may be selectively deployed into a first position to cover or occlude the permeable base structure 12 as defined by the plurality of tines 12'. The flap 30 is formed from any suitable material which is substantially impermeable to flowable materials such as powder or granules, the level of impermeability being dictated by the intended materials with which the grab 20 is to be used. However, the flap 30 is preferably formed of metal such as steel or aluminium alloy, which embody sufficient strength to cope with the operational loads experienced thereby. When the flap 30 is in this first position, along with the solid sides 17 and closed top in the form of a lid 19 of the grab head 14, the flap 30 forms a enclosure that can retain fine or particulate materials such as powder or granulated feed stuff. When the flap 30 is retracted to a second, in use vertical position, the grab 20 can be used in the conventional manner to handle silage type materials as hereinbefore described with reference to the prior art grab 10.

Referring in particular to Figures 3 to 6, the preferred method of mounting the flap 30 about the base structure 12 is illustrated in greater detail. At approximately the centre of the crossbar 13, the flap 30 (shown extending away from the base structure 12) is pivotally coupled to the base structure 12 at a fulcrum point 22. A leg 23 extends rearwardly from the fulcrum point 22, while being hingedly mounted about said fulcrum point 22. The leg 23 is also rigidly or fixedly coupled to the flap 30, such that rotation of the leg 23 about the fulcrum point 22 results in direct rotation of the flap 30 about the fulcrum point 22. An otherwise free end 24 of the leg 23 is pivotally mounted to a rod 27 of a single acting second hydraulic cylinder 25. This

second hydraulic cylinder 25 is provided with an inlet/outlet port B, through which pressurised hydraulic fluid is pumped into the cylinder 25, in order to effect extension of the rod 27 from the cylinder 25. It will therefore be appreciated that the leg 23 and fulcrum point 22 serve to translate linear motion of the rod 27 into rotary motion of the flap 30 about the fulcrum point 22, in order to move the flap 30 between the first and second positions. The other end of the second cylinder 25 is pivotally fixed to the base structure 12, in order to allow a slight rotation of the second cylinder 25 as the rod 27 is extended and retracted, which is due to the curved path of the free end 24 of the leg 23 about the fulcrum point 22.

Around the rod 27 within the lower end of the cylinder 25 is located a coil spring 26 which is biased to retract the rod 27, or to effectively shorten the overall length of the second cylinder 25. Thus the spring 26 effectively biases the flap 30 into the first position occluding the tines 12'of the base structure 12. In order to retract the flap 30 into the second position, hydraulic fluid must be pumped under pressure into the second cylinder 25, via the port B, in order to effect extension of the rod 27.

It will however be understood that the above described mechanism, comprising the second cylinder 25, the leg 23 and the fulcrum point 22, is merely the preferred arrangement to be utilised in moving the flap 30 between the first position and the second position. The preferred arrangement beneficially utilises pressurised hydraulic fluid to effect this movement, which pressurised hydraulic fluid is already used in many industrial vehicles to power various aspects thereof, and thus the grab 20 of the present invention is ready to use with any such vehicles, or indeed with any conventional independent hydraulic supply. However, any other suitable configuration, mechanical, electrical, or otherwise, could of course be utilised to effect movement of the flap 30 as hereinbefore described.

For example, a motor (not shown), whether powered by electricity, a liquid fuel, or indeed gas, could be utilised to drive a pinion (not shown) which meshes with a

linear rack (not shown), which would impart the necessary linear motion to the leg 23 to be translated into rotary motion of the flap 30. A suitable solenoid (not shown) or a pneumatic ram (not shown) could also replace the second cylinder 25, while maintaining the functionality of the invention. It will also be apparent that many more mechanisms could be utilised in order to move the flap between a position occluding the tines 12'and a position distal said tines 12'. In this regard, it should also be noted that retraction of the flap 30 into the second position within the grab head 14 is merely the preferred arrangement, and the flap 30 could of course be located, for example, beneath the tines 12'when in the first position, and pivot downwardly away from same before pivoting back up into the second position between the pair of support arms 15.

However, as explained above, the use of pressurised hydraulic fluid is the preferred means by which to operate the grab 20 of the present invention. In addition to being a widely used source of power on many industrial and agricultural vehicles, the use of hydraulic power enables further benefits to be derived from the invention, as will be described hereinafter. Thus in a particularly preferred embodiment of the invention, a hydraulic fluid supply line S is connected to port A of the first cylinder 21 and is connected in parallel to port B on the second cylinder 25. When hydraulic pressure is applied through the supply line S hydraulic fluid is pumped into the first cylinder 21 via port A, thereby shortening the first cylinder 21, and consequently opening the grab head 14. When the grab head 14 is fully open and the first cylinder 21 has reached the end of its closing stroke a slight build up of hydraulic pressure will then begin to pump hydraulic fluid into the second cylinder 25 via port B, thereby extending the rod 27. As hereinbefore described, extension of the rod 27 results in hinging of the flap 30 into the second, vertical position against the bias of the spring 26. The flap 30 will remain in this state as long as the elevated pressure is maintained in the supply line S.

This sequential operation of the first cylinder 21 and the second cylinder 25 may be effected in a number of ways. For example, the first cylinder 21 may be chosen to have a lower operating pressure than the second cylinder 25, such that although ports A and B are arranged in parallel, pressurised fluid will only flow into the first cylinder 21 until the end of it's stroke has been reached, and the pressure therein begins to build. Once the threshold pressure for the second cylinder 25 is then reached, fluid will be pumped into same, thereby actuating the second cylinder 25.

With such an arrangement, it is preferable that the operating pressure of the second cylinder 25 is only slightly above that of the first cylinder 21, such that when the first cylinder 21 reaches the end of it's stroke, there will be an almost instantaneous actuation of the second cylinder 25. However, a desired time delay could of course be built into the sequential operation of the first cylinder 21 and the second cylinder 25.

Another way of achieving this sequential operation is to install a restrictor (not shown) upstream of port B of the second cylinder 25, which restrictor has a bypass or threshold pressure again just above that of the operating pressure of the first cylinder 21. This arrangement may be used, for example, where the first cylinder 21 has a greater operating pressure than the second cylinder 25.

With the flap 30 in the second, vertical position, the shear grab 20 can be used to handle material such as silage as hereinbefore described with reference to the grab 10 of the prior art. When the grab 20 is pushed into a silage heap, the grab head 14 is closed by actuating the cylinder 21 through port C, thus closing the grab head 14 against the tines 12'of the base structure 12, cutting a block of silage. Although pressure in the supply line S must be dropped when applying pressure to port C, in order to permit the grab head 14 to be closed, it will be appreciated that this pressure release from port B, and so the second cylinder 25, does not affect the flap 30, as it will in any case be held in the second, vertical position by the block of loaded silage bearing against it.

Once the block of silage has been successfully cut and transported to a desired location, the silage can then be discharged from the shear grab 20. This is achieved by actuating the first cylinder 21 through port A to open the grab head 14 relative to the base structure 12. It will be appreciated that as the grab head 14 is being opened, there will not be sufficient pressure in the supply line S to pressurise the second cylinder 25, and thus the spring 26 will be urging the flap 30 towards the first position, the block of silage disposed within the grab head 14 thus being pressed against the interior of the grab head 14, but ultimately preventing the flap 30 from moving into the first position. However, once the grab head 14 has fully opened, and before additional pressure is applied to the supply line S, the grab head 14 will no longer present an obstruction to the block of silage, and thus the force of the spring 26 on the flap 30 will act to push the block of silage off the tines 12', thereby ejecting the block of silage from the grab 20. It can thus be seen that spring biasing of the flap 30 into the first position enables a block of silage to be ejected from the grab 20 without the requirement to tilt the grab 20 downwardly.

In addition to the above conventional operation, the grab 20 can be used to handle finer or granulated materials (not shown) such as powdered or granulated feed stuff or the like. In order to make ready the grab 20 for handling such material, an operator will initially open the grab head 14 as hereinbefore described, by the application of hydraulic pressure to port A. Provided that the operator, once the grab head 14 is fully opened, does not apply additional pressure to the supply line S such as to actuate the second cylinder 25, the flap 30 will already be in the first position occluding the tines 12'. If the second cylinder 25 has been pressurised such that the flap 30 is in the second position exposing the tines 12', all an operator has to do is slightly rotate the grab head 14 back towards the base 12 by applying pressure to port C of the first cylinder 21. When this side of the first cylinder 21 is pressurised it relieves pressure from port A and port B. The pressure applied by the spring 26, in addition to the weight of the flap 30, will then cause the second cylinder 25 to retract

and so force the flap 30 to rotate downwardly into the first position such as to occlude the tines 12'. This arrangement thereby offers an enclosed base 12, and sides 17, thus forming a scoop that can be used as normal for lifting fine material.

Furthermore, once the scoop has been pushed into such fine material, the grab head 14 can then be completely closed by applying further pressure to port C to form a complete enclosure, which can in turn be used to carry fine material to a desired location without any spillage.

It will therefore be seen that the preferred embodiment of the invention provides an improved shear grab 20 in which the control of both the flap 30 and the grab head 14 can be implemented with only one control (not shown). In other words, a single supply line S of pressurised hydraulic fluid can be used to open the grab head 14, and to then move the flap 30 from the first position to the second position, greatly simplifying the operation of the improved shear grab 20 of the present invention.

This aspect is particularly beneficial to users who wish to upgrade to the grab 20 of the present invention from a prior art grab such as the grab 10 illustrated in Figure 1.

Although the grab 20 incorporates the additional second hydraulic ram 25, no addition hydraulic conduits (not shown) or vehicle mounted controls (not shown) need be fitted in order to control the grab 20, as the second hydraulic ram 25 is powered from the same supply line S as the first hydraulic ram 21. The grab 20 may therefore be directly fitted in place of a prior art grab, without any further adjustments being made.

As highlighted above, although the preferred embodiment has been described in terms of hydraulic cylinders, it will of course be understood by a person skilled in the art that this embodiment of the invention could equally have been implemented with, for example, pneumatic cylinders (not shown), or a mixture of both.

It will also be appreciated that, although less preferred, the second hydraulic ram 25 could be replaced with a double acting ram (not shown), which would thus replace the spring 26, but which would require an additional branch of hydraulic conduit (not shown) and a vehicle mounted control (not shown) in order to control same.

Similarly, the first hydraulic ram 21 could be replaced with a single acting hydraulic ram (not shown) spring biased towards the extended state, although the spring (not shown) utilised would have to be powerful enough to force the serrated edge 19' through any material being cut into blocks or bales.