BACKGROUND TO THE INVENTION

Overshot loaders, also known as overhead loaders, over slung loaders or overthrow loaders were introduced into the market about 60 years ago and were employed to move or load material such as earth or gravel from a position in front of the loader, to a receiver located in a position behind the loader.

The loaders typically comprise a scoop or bucket located at the end of a boom fitted to a machine. The material to be transferred is loaded into the scoop or bucket located ahead of one axle of the machine. The boom, and subsequently the scoop is then lifted in a trajectory, up over the machine and down the other side, allowing the material to be discharged either into a receiver, positioned ahead of the second axle of the machine, or onto the ground.

The energy required for movement of the boom was typically effected by hydraulic/electric activators, or winches and cables.

Despite the fact that overshot loaders have many obvious benefits, they suffered from a number of severe drawbacks, not least of which was the mechanical disadvantage caused by the fact that the scoop is located on the end of a long boom, resulting in poor leverage, requiring an adversely deep gearing to generate the high torque but low speed required for breakout that is not appropriate when applied to the task when applied to only lifting the bucket, where lighter effort but higher speeds are required. Further, a bucket on the end of a long boom affects stability of the machine in an adverse way.

Another difficulty facing early machines was that of visibility, where the operator had a clear view of one operation, but was in the dark regarding the other operation, a situation that is now easily overcome with modern industrial grade cameras. Other difficulties faced included preventing spillage from the bucket where the bucket angles relative to the horizontal change progressively during transit.

It is an object of this invention to provide an overshot loader mechanism which, at least partially, alleviates some of the above mentioned problems. SUMMARY OF THE INVENTION

In accordance with this invention, there is provided an overshot loader mechanism for transporting material in an overhead trajectory from a filling position at a loading end of a vehicle, to a discharge position at a discharge end of the vehicle, the overshot loader mechanism comprising;

a chassis frame for supporting the body of the vehicle,

at least one control arm, for controlling the movement of at least one load arm, one end of the control arm being pivotally connected to the chassis frame and the other end of the control arm being pivotally connected to a first/thrust end of the load arm;

and a bucket pivotally connected to a load end of the load arm,

in which rotation and/or counter rotation of the control arm about its pivotal connection to the frame causes movement of the thrust end of the load arm, from a terminal high point when the bucket/load end of the load arm is located towards the bottom of its trajectory for bucket filling and/or discharge, and a terminal low point when the bucket end of the load arm is located towards the height of its trajectory, thus reducing the centre of gravity of the loader mechanism, while retaining a bucket height sufficiently high enough to clear an operator cab located on the vehicle.

There is further provided for the overshot loader mechanism to comprise at least one cam rail extending at least partway along the length of the chassis frame and for the load arm to further include a roller secured at a point along its length, the load arm roller being receivable in use on the cam rail, for guiding and supporting movement of the load arm from a filling position to a discharge position.

In a preferred embodiment of the invention, the overshot loader mechanism comprises a cross shaft, pivotally mounted across the breadth of the chassis frame and a control arm mounted at either end of the cross shaft. Each control arm is pivotally connected to a load arm.

The overshot loader further comprises two cam rails, locatable on opposing sides of the chassis frame, and separated by a distance large enough to accommodate a centrally mounted operators cab. There is further provided for each cam rail located on either side of the chassis frame to comprise a loading cam rail section, extending from the filling end of the chassis frame towards the middle of the chassis frame, and a discharge cam rail section, extending from about the middle of the chassis frame towards the discharge end of the chassis frame.

The discharge cam rail section may be pivotally connected to the loading cam rail section.

The profiles of the loading and discharge cam rail sections are designed to support the load arm in transporting the bucket through an appropriate trajectory.

The profile of the loading cam rail section is generally convex while the profile of the discharge cam rail section is generally concave.

The loading cam rail section may further include a latch located at its lowest end, for engaging the roller when in the filling position thereby allowing downward pressure on the bucket during filling.

Alternatively, in a more aesthetically pleasing embodiment of the invention, a cam plate may be affixed to the load arm, and a roller may be affixed to a bracket rigidly mounted to the chassis frame, the roller engaging with the cam plate to allow a downforce to be applied to the bucket during filling.

There is further provided for the discharge cam rail section to be pivotable to allow for the load arm to drop the bucket closer towards the ground, to a spreading position.

The chassis frame includes axles and wheels when on a wheel loader or endless tracks when fitted to a crawler type of vehicle.

The bucket is connected to the load arm through a system of pins and linkages, and articulated under load by a power source.

Movement of the control arm may be driven by hydraulic cylinders, electric actuation or other appropriate sources of energy.

There is further provided for a single stroke of the power source to displace the thrust end of the load arm from its terminal high point to its terminal low point, to drive the bucket from its filling position to the top of its trajectory only, and for a single reverse stroke of the power source to displace the thrust end of the load arm from its terminal low point back towards its high point, to move the bucket from the top of its trajectory to its discharge position or spreading position, and whereby the forward and reverse stroke of the power source is achieved with electronically controlled hydraulics or the like.

The rotation and counter rotation of the cross shaft, and consequently the control arms may be electronically triggered, as may the position of the bucket in relation to the load arm during its trajectory from filling to discharge to prevent spillage. Alternatively, other appropriate means may be employed.

The geometry of the cam rail, the position of the roller on the load arm and the effective mounting point of the thrusting end of the load arm at its terminal low point, provide for a reduced overhead trajectory of the bucket and a reduced centre of gravity, while transferring the load from the vehicles loading side to the vehicles discharge side, while also enabling extension of the bucket in front and behind the vehicle to accommodate sufficient loading and offloading clearances when the thrust end of the load arm is at its terminal high point.

Brief Description of the Drawings

A preferred embodiment of the invention is described below by way of example only and with reference to the following drawings, in which;

Figure 1 is a schematic of the overhead loader of the invention;

Figure 2 is a side view of an embodiment of the invention during bucket filling;

Figure 3 is a side view of an embodiment of the invention illustrating an early position as the bucket is power driven from its loading position towards its zenith point;

Figure 4 is a side view of an embodiment of the invention illustrating the load arm and bucket at the peak of their trajectory;

Figure 5 is a side view of an embodiment of the invention illustrating the beginning of the discharge sequence; Figure 6 is a side view of an embodiment of the invention illustrating the discharge point;

Figure 7 is a side view of an embodiment of the invention illustrating the bucket close to ground level on the discharge side;

Figure 8 is a plan view of an embodiment of the invention;

Figure 9 is an illustration detailing the use of cams, the rollers, the load arms and control arms as the bucket is progressively powered from filling to discharge;

Figure 10 illustrates an alternative embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figures 1 to 10, like features of the invention are indicated by like numerals.

Referring to Figures 1 to 8, the overshot loader mechanism (10) for transporting material in an overhead trajectory, from a bucket filling position at one end of a vehicle (Figure 2) to a discharge position at the other end of the vehicle (Figure 6 and 7), comprises a chassis frame (12) mounted on axles and wheels (14) for supporting the mechanism. A cross-shaft (29) is pivotally mounted across the width of the chassis frame (12). See (Figure 8). One end of a pair of control arms (18) are each affixed to opposite ends of the cross-shaft (29). The other end of each control arm (18) is pivotally connected to the thrust end of a load arm (20) at pivot point (25).

The free ends of the load arms (20) are rigidly connected by member (40) and are pivotally connected to a bucket (16) at pivot point (27) through pins and linkages and a power source (details not shown). In this way the bucket (16) is indirectly connected to the centre of mass of the machine (10) allowing for a degree of elasticity to be engineered into the invention.

A pair of cam rails (35) located on opposite sides of the machine support a roller (32) attached at a fixed point along the length of each load arm (20) and is receivable on cam rails (35) during operation. Each cam rail (35) comprises a loading cam rail section (34), affixed to the chassis frame (12) at the loading end and extending partway along the length of the chassis frame, and a discharge cam rail section (36) pivotally connected to the loading cam rail section (34) at pivot point (44) and extending towards the discharge end of the chassis frame (12).

Referring to Figures 2 to 7, the loading cam rail section (34) has a profile that is generally convex, while the discharge cam rail section (36) describes a generally concave profile. However, it is to be understood that other profiles may achieve a similar result.

Referring to figures 1 to 7, and in one embodiment of the invention, the loading cam rail section (34) further includes a latch (42) located at its loading end, for engaging the roller (32) when the load arm (20) is in the filling position, thus retaining the roller on the cam rail section (34), allowing the operator to apply downward force on the bucket (16) during filling without the roller lifting off the loading cam rail section (34).

Alternatively, and with reference to figure 10, in a more aesthetically pleasing embodiment of the invention, a cam plate (51 ) is affixed to the load arm (20) and a roller (52) is affixed to a bracket (50) that is rigidly mounted to the chassis frame (12). These elements allow for a downforce to be applied to the bucket during filling.

The pivot point (44) at which the discharge cam rail section (36) is connected to the loading cam rail section (34) allows the operator to set the discharge end height of the discharge cam rail section (36) so as to allow for a consistent dumping height or even to drop the bucket (16) to ground level as depicted in Figure 7, to allow for spreading of material while on the move.

In use, and referring to Figure 2, when in the filling position, the pivot point (25), joining the control arm (18) to the load arm (20), is at its highest terminal point, ensuring that the load arm (20) maintains a clearance above the loading end axle, and in such a position where latch (42) prevents the roller (32) from being lifted off the cam rail section (34) when a downforce is applied to the bucket (16).

Maximum power is absorbed at bucket filling (Figure 2). Thereafter energy requirements diminish as the energy is only directed to lifting the bucket (16). The profile of lifting cam (34) is engineered so as to direct this surplus energy to accelerating the mass of the bucket (16) on its journey to its high point (Figure 4).

Referring to Figure 3 once the bucket has been filled, the pivot point (25) rotates under power about pivot point (29), from its terminal high point (Figure 2) towards its terminal low point illustrated in Figure 4.

As the load arm (20) is connected to control arm (18) at the pivot point (25), any incremental reduction of the height of pivot point (25) powers the roller (32) up the slope of the loading cam rail section (34) displacing the load arm (20) and bucket (16) from its position at loading, as depicted in Figure 2, through the position depicted in Figure 3 until it is displaced progressively into a substantially vertical position as illustrated in Figure 4, as the pivot point (25) is power driven towards its lowest terminal point (Figure 4) as the bucket (16) is displaced progressively towards its zenith.

It will be appreciated that the geometry of the cam rails and all the linkages are engineered for a reduced height of the overhead trajectory of the bucket (16) with a corresponding lowering of the centre of gravity of the loaded bucket, while still allowing a sufficient clearance between the top of the operators can and the bucket assembly.

One stroke of the power source (not shown) will only displace the pivot point (25) from its high point as depicted in Figure 2, through to its terminal low point as depicted in Figure 4, and as such will only drive the load arm (20) and bucket (16) from its filling position through to being displaced into a more or less vertical position. It then requires a reverse stroke of the power source to displace the load arm from this position illustrated in Figure 4 through the intermediate position illustrated in Figure 5, until the load arm and bucket reach the discharge position illustrated in Figure 6, or even to its spreading position as illustrated in Figure 7.

By definition pivot point (25) must come to a complete standstill as it reaches its lowest terminal point before it can commence its return journey. It will be understood that the loaded bucket and load arm will have gathered considerable momentum as it is being accelerated to its position as depicted in Figure 4. Such momentum allows the bucket to easily cross the valley at point (44). Referring to Figure 9, at points 7a and 7b, the time delay in reversing the flow of fluid to the hydraulic cylinder or the like will be engineered to equate to the time the load arm takes to cross the valley between loading cam (34) and discharge cam (36).

The rotation and counter rotation of the control arm (18) about its pivot point (29) is activated by a power source that is electronically triggered or the like, as is the position of the bucket (16) in relation to the load arm during its trajectory from filling to discharge, to prevent spillage in use.

While the figures illustrate a wheeled vehicle, the loader can also be employed on a tracked vehicle.

It will be appreciated that one of the fixed parameters relating to a conventional overshot loader is that the length of the load arm or boom carrying the bucket may not be shorter than half of the sum of the length of the vehicle plus the required bucket filling clearance ahead of the filling end of the vehicle and the required bucket discharge clearance ahead of the discharge end of the vehicle needed for filling a receiver.

For example, if the total length of the vehicle plus the clearances is 5.6m load arm cannot be shorter than 2,8m. Furthermore, in the case of a wheel mounted overshot loader the thrust end of the load arm needs to be fixed to the vehicle at a minimum height in order that the load arm does not foul the one axle during bucket filling or the other axle during the spreading of material. For example, if the load arm is 2.8m long, the thrust end of the load arm needs to be at least 2.2m above the ground to clear the axle, as explained, the bucket will be at 5m (2.2m + 2.8m) above ground at the height of its trajectory. Add a further 0.4m for the centre of gravity of the loaded bucket, and the overall centre of gravity of the loaded bucket is at an unnecessary height of 5.4m when in fact the bucket needs to be only 3.4m above ground to clear the top of operators cab as described in this example.

To lower the centre of gravity as much as possible but still clear the cab, it follows that the thrust pin that connects the load arm to the bucket only needs to be 3.4m to clear the cab, less the load arm length of 2.8m means the knuckle at point (25) will be 0.6m above ground. This ideal is achieved in the above described invention by having the pair of control arms (18) mounted on the ends of a cross shaft (29) separated by a gap wide enough to accommodate the centrally mounted operators cab. The free ends of these control arms (18) can reciprocate between a terminal high point and a terminal low point ie 2.2m above ground, as the minimum height to clear the front axle during bucket filling in this example, and 0.6m above ground as the calculated height to allow the bucket to clear the operators cab, all with the lowest centre of gravity.

The free end of the control arm (18) at its starting high point becomes the ideal anchor point (25) for the load arm (20) during bucket filling. To maximise vehicle stability requires keeping the loaded bucket as low as possible during its trajectory. This is achieved by rotating the control arms (18) and consequentially, load arm (20) and the bucket (16) to the lowest possible point that still leaves sufficient clearance between the cab and bucket.

Furthermore the loading cam rail section (34), which supports the load arm by means of the roller, is profiled to displace the bucket in a trajectory from its loading position to its high point, allowing for cab clearance and similarly the discharge cam rail section (36) is profiled to transport the bucket in a trajectory from its high point to its discharge position or even ground level.

The invention therefore satisfies the requirement of providing an overshot loader in which the bucket follows a suitable trajectory, from filling to its high point and then from its high point to its discharge point, and additionally being able to spread material at ground level if so required.

The invention provides a system whereby the thrust end of the load arm (25) is power driven from a terminal high point, for loading of the bucket as depicted in Figure 2 to a terminal low point, to displace the bucket to its highest point, in one full power stroke of the activator as illustrated in Figure 4. The reverse stroke of the power drive will displace the bucket from its high point to its discharge position as illustrated in Figure 6 or even to ground level as illustrated in Figure 7. Referring to Figure 9, the use of cams of a specific profile ensures that the load arm (20) is always supported by two inter related elements, enabling the bucket to follow the required trajectory. The first element is the load arm anchor point (25) that is displaced incrementally from its highest terminal point towards its lowest terminal point. The second element is the support provided to the load arm. This is achieved by fitting a roller (32) at a point along the length of the load arm (20) that will thrust against a given point on the loading cam rail section (34) for bucket filling. As the thrust point (25) of the load arm (20) moves incrementally downwards the roller will be supported at a higher and higher point on this loading cam (34) for the bucket to be lifted to its next position on its trajectory. As this continues increment by increment so too does the roller (32) require support at every incremental point to scribe the required trajectory. By joining these support points in a smooth curve it becomes the profile of loading cam (34) that together with the moving anchor point (25) displaces the load arm (20) in a manner that imparts the required trajectory to the bucket from filling until it reaches its highest point.

For the bucket (16) to be displaced from its highest point to its dumping position, or even dropped to ground level, requires the power drive to start reversing the direction of the anchor point (25) from its lowest terminal point towards its high point. As this is happening increment by increment to displace the bucket towards its dumping position requires that the load arm roller needs to be supported at every incremental point. By joining these support points in a smooth curve dictates the profile of the discharge cam (36).

The invention therefore provides an overshot loader which is therefore more efficient and cost effective than a conventional loader.