EP1831472A4

EP1831472A4 - Ground scraper

Info

Publication number: EP1831472A4
Application number: EP05818405A
Authority: EP
Inventors: Gregory Charles Mclean
Original assignee: LORIDEN Pty Ltd
Current assignee: LORIDEN Pty Ltd
Priority date: 2004-12-20
Filing date: 2005-12-19
Publication date: 2008-04-02
Also published as: EP1831472A1; WO2006066318A1; US20090077838A1

Abstract

A ground scraper (10) comprises a bowl (12) for holding excavated ground material, a cutting edge (14) mounted at an open side of the bowl for excavating the ground material, a hitch assembly (56) pivotally coupled to the bowl for coupling the ground scraper to a powered vehicle and an apron (44) pivotally mounted to the bowl for closing the open side of the bowl. An axis of rotation (50) of the apron is substantially parallel to, forward of and above a longitudinal axis of the cutting edge. The axis of rotation is located in a plane extending from the cutting edge and the plane is inclined between 15° and 30° to a vertical plane extending from the cutting edge.

Description

TITLE GROUND SCRAPER

FIELD OF THE INVENTION The invention relates to ground scrapers and improvements thereto. In particular, the present invention relates to an improved ground scraper of the type that is towed behind a powered vehicle such as a tractor.

BACKGROUND TO THE INVENTION In land-levelling and soil-moving applications, a ground scraper is often employed, which is towed behind a powered vehicle such as a tractor to excavate and level the ground and transport the excavated ground to another location. Generally, ground scrapers comprise a cutting edge, referred to as a blade or bit, of adjustable height that is lowered to engage and excavate the ground and a bowl rearward of the blade in which the excavated material is collected as the scraper is pulled along. Once the required volume of material has been excavated to level the ground or the bowl is full, the blade is raised to cease excavation and a gate or "apron" closes an opening at the front of the bowl. Typically, the material is transported to a dumpsite where the apron is opened and a hydraulic ejection ram drives a door forward to expel the excavated material from the bowl. Some scrapers do not comprise an ejection ram and door and instead comprise a bowl that pivots causing the excavated material to fall from the bowl under gravity.

One type of ground scraper comprises a rigid hitching arm forward of the bowl for coupling the scraper to the powered vehicle and a set of wheels, often referred to as walking wheels, rearward of the bowl to support the scraper and enable the scraper to roll along the ground. Whilst this type of scraper is very good at light land levelling and may be drawn over the ground quickly, the relatively small size of the bowl and the opening thereto makes it unsuitable for large earth moving applications. Typically, the apron only opens a small distance, which prevents all of the dirt being expelled from the bowl in a single pass of the door or pivot of the bowl. This results in the need to drive the door back and forth a number of times to expel the dirt from the bowl or to pivot the bowl numerous times to dislodge the dirt. This is particularly so when the dirt is wet.

Another consequence of prior art aprons is that once the bowl is relatively full, the apron is incapable of forcing any more dirt into the bowl. Similarly, dirt that has been scraped up often accumulates in front of the cutting edge as the scraper moves along and the dirt does not collect in the bowl. Some prior art aprons are incapable of moving this excavated dirt into the bowl and it has to be left behind. This results in mounds of earth on the otherwise levelled ground that have to be collected once the bowl has been emptied, which is inefficient. Typically 20-40% of the scraped dirt can be left behind with this type of scraper when the dirt is loose or dry. Further problems are encountered with this scraper when used in the wet because the wet ground material clogs the workings of the bowl. The construction of this particular ground scraper has many voids and regions in which dirt can accumulate and be compacted. The earthmoving/levelling process then needs to cease while the scraper is freed up. Another problem of some scrapers is created by the relatively large separation of the sets of walking wheels at the rear of the scraper, which exacerbate the difficulty encountered in turning the scraper. The difficulty in turning the scraper also causes the scraper to rip up the levelled ground, often creating ruts of 30cm or more, thus necessitating re-levelling of the ground.

The wheels of other scrapers are fixed in position and therefore, when not all of the wheels support the scraper on the ground, such as when the scraper is used on undulating terrain, high stress can be imparted on one or more of the wheels and/or the frame of the scraper. Furthermore, most scrapers are susceptible to "duck-walking" on undulating terrain, which impairs the levelling capacity of the ground scraper and the operator must slow down to overcome the duck-walking, thus slowing down the levelling process.

Further problems of some prior art ground scrapers are exhibited when the apron is in the raised position when the scraper is being drawn along. In the raised position, the apron often obscures the tractor operator's view of the bowl and the blade. Therefore, the operator cannot see when the bowl is full and/or if there is a problem, such as an obstruction, which may damage the scraper.

With some prior art ground scrapers, the raised apron can be at a position of 3m or more above the ground, thus significantly obscuring the operator's view of the scraper. The high elevation of the apron also exacerbates the aforementioned

"duck-walking" problem of some scrapers.

A yet further drawback of numerous prior art ground scrapers is their complexity of design. Many have a large number of different parts which complicates maintenance and repairs and increases the cost thereof. A range of ground scrapers are disclosed in United States Patent Nos. 6,092,316 (Brinker), 6,041528 (Broach) and 5,839,212 (Brinker), United States Patent Application Nos. 2002/0078606 (Grummett) and 2004/0188115 (Moyna et al.) and former Soviet Union abstracts SU 1257141 (Mogil Mech. Eng. Inst.), SU 1216292 (Moscow Auto Road Constr.) and SU 768884 (Sibe Auto Road Inst.). Whilst these scrapers perform their task satisfactorily, each of these ground scrapers suffers from one or more of the aforementioned problems.

In this specification, the terms "comprises", "comprising" or similar terms are intended to mean a non-exclusive inclusion, such that a method, system or apparatus that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

OBJECT OF THE INVENTION

It is an object of the present invention to address or at least ameliorate one or more of the aforementioned problems associated with the prior art ground scrapers and/or to provide a useful commercial alternative.

SUMMARY OF THE INVENTION

In one form, although it need not be the only or indeed the broadest form, the invention resides in a ground scraper comprising: a bowl for holding excavated ground material; a cutting edge mounted at an open side of the bowl for excavating the ground material; a hitch assembly pivotally coupled to the bowl for coupling the ground scraper to a powered vehicle; and an apron pivotally mounted to the bowl for closing the open side of the bowl; wherein an axis of rotation of the apron is substantially parallel to, forward of and above a longitudinal axis of the cutting edge, the axis of rotation located in a plane extending from the cutting edge, the plane inclined between 15° and 30° to a vertical plane extending from the cutting edge.

Suitably, the plane extending from the cutting edge is inclined between 18° and 27° to the vertical plane extending from the cutting edge.

Preferably, the plane extending from the cutting edge is inclined at 26° to the vertical plane extending from the cutting edge.

Preferably, the ground scraper further comprises at least one hydraulic ram coupled between the hitch assembly and the bowl for adjusting a height of the bowl relative to the hitch assembly and the ground.

Suitably, the at least one hydraulic ram is coupled to a draft tube of the hitch assembly.

Preferably, the ground scraper further comprises a frame attached to, and rearward of, the bowl and at least one pair of offset wheels pivotally mounted to the frame.

Preferably, the frame comprises an upper frame member having an upwardly tapering cross section and a lower frame member having a downwardly tapering cross section.

Suitably, the frame comprises a pair of substantially vertical frame members extending between the upper frame member and the lower frame member, the at least one pair of offset wheels pivotally mounted between the substantially vertical frame members. Preferably, the substantially vertical frame members taper upwardly and downwardly from a mounting point of the at least one pair of offset wheels.

Suitably, a mounting point for the at least one hydraulic ram coupled between the bowl and the apron is in substantially the same plane as the axis of rotation of the apron.

Suitably, the at least one hydraulic ram coupled between the hitch assembly and the bowl and at least one hydraulic ram coupled between the bowl and the apron are interchangeable.

The ground scraper may further comprise a guard detachably mountable to sidewalls of the bowl to prevent overflow of excavated material from the rear of the bowl.

The ground scraper preferably further comprises a detachable wall portion to enable the apron to be attached and detached from the bowl.

Preferably, an operator of the powered vehicle has a line of sight to the cutting edge and/or the bowl when the apron is in an open position.

Further features of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:

FIG 1 is a side elevation of an improved ground scraper with an apron in a closed position and an ejector door in a rearward position according to one embodiment of the present invention;

FIG 2 is a plan view of the ground scraper in FIG 1 ; FIG 3 is a side elevation of the ground scraper in FIG 1 with the apron in an open position and the ejector door in a forward position; FIG 4 is a front elevation of the ground scraper in FIG 1 ;

FIG 5 is a rear elevation of the ground scraper in FIG 1 ; FIG 6 is a side elevation of a draft arm of the ground scraper in FIG 1 ; FIG 7 is a plan view of the draft arm of FIG 6; FIG 8 is a front elevation of the apron; FIG 9 is a plan view of an ejector door ram;

FIG 10 is a side elevation of the ejector door ram of FIG 9; FIG 11 is a rear elevation the ejector door ram of FIG 9; FIG 12 is an end view of a wheel assembly; FIG 13 is a plan view of the wheel assembly in FIG 12; FIG 14 is an end view of a wheel assembly and frame;

FIG 15 is a front view of a cutting edge comprising an additional toothed cutting edge;

FIG 16 is a sectional view of FIG 16;

FIG 17 is a schematic diagram showing angles between an axis of rotation of the apron and a transverse edge of an internal floor plate;

FIG 18 is a sectional view of a sidewall of the ground scraper in FIG 1 ; and

FIG 19 is a side elevation of a check plate. DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS 1 and 2, in accordance with an embodiment of the present invention there is provided an improved ground scraper 10 comprising a bowl 12 for holding excavated material and a cutting edge 14 in the form of a blade or bit for excavating ground material. Bowl 12 is formed from a base 16 and sidewalls 18 and the cutting edge 14 extends the width of the bowl 12.

Rearward of the bowl 12 is a transverse frame member 20 spanning the width of the bowl 12 and attached to sidewalls 18. Frame 22 is connected to transverse frame member 20 by any suitable means known in the art, such as welding. Frame 22 includes upper frame members 23, lower frame members 25 and a push pad 24 extending between upper and lower frame members 23, 25 to which force may be applied by, for example, a bulldozer, to aid the powered vehicle in moving the laden scraper 10 and/or to aid extracting the scraper 10 in the event that it becomes bogged, for example, in soft terrain. Frame 22 and transverse frame member 20 are made from hollow sections of 350 grade steel, which provide good resistance to deflections and twisting. However, alternative grades of steel may be employed. Frame 22 and transverse frame member 20 may further comprise extra gussets at corner regions to provide added strength.

A plurality of walking wheels 26 are provided with each wheel mounted to an axle 28. Walking wheels 26 are provided in pairs to form wheel assemblies

30 and in one embodiment, the wheels 26 in each pair are offset with respect to each other resulting in staggered wheel locations. Each wheel assembly 30 is pivotally mounted to substantially vertical frame members 32. Wheel assemblies

30 and their mounting to frame 22 will be described in more detail hereinafter. With additional reference to FIGS 5 and 9-11 , ground scraper 10 further comprises ejector door 36 at or toward the rear of the bowl 12 and ejector door 36 extends substantially the width of the bowl 12. Ejector door 36 is pivotally coupled to hydraulic ejection ram 38 and the other end of hydraulic ejection ram 38 is coupled to a rear portion of frame 22 adjacent push pad 24. As shown most clearly in FIGS 9-11 , rollers 41 are rotatably mounted on elongate members 45 extending rearwardly from ejector door 36. Rollers 41 move on roller guides 43 attached to the frame 22 to help maintain smooth motion of the ejector door 36 in the bowl 12. As shown in FIGS 1 and 2, smooth motion of the ejector door 36 is further aided by rollers 40 rotatably mounted to each side of ejector door 36, which move on respective roller guides 42 mounted to the inside of sidewalls 18 of bowl 12. Alternative embodiments may comprise more than a single roller 40 and roller guides 42 on each side. Excavated material is ejected from the bowl 12 by hydraulic ejection ram 38 moving ejector door 36 from the rear of the bowl toward the front of the bowl 12. A rearward position of the ejector door 36 is shown in FIG 1 and a forward position of the ejector door 36 is shown in FIG 3.

Ground scraper 10 further comprises an apron 44 pivotally mounted to the bowl 12 by pivot means 46 in the form of trunnions and caps, which are familiar to those skilled in the art. Pivot means 46 also coincides with an axis of rotation of the apron 44. According to one embodiment, apron 44 is a unitary structure. When apron 44 is in a lowered or closed position as shown in FIG 1 , excavated material is retained in bowl 12, for example, during transportation to a dumpsite. When apron 44 is in a raised or open position as shown in FIG 3, such that apron 44 has moved approximately 90° clockwise about pivot means 46, this allows ejection of material from the bowl 12 by ejector door 36. Obviously, apron 44 is in the raised or open position when ground material is being excavated and the ground is being levelled to allow the excavated material to enter, and be collected in, the bowl 12. Apron 44 is raised and lowered by a pair of hydraulic rams in the form of apron rams 48. One apron ram 48 is located either side of the apron 44, as clearly shown, for example, in FIG 2. For the sake of clarity, only one of the apron rams 48 is shown in FIG 1. With additional reference to FIG 8, apron rams 48 are pivotally coupled at one end to upwardly extending arms 47 of apron 44 by means of lugs 51 and are pivotally coupled at the other end to sidewalls 18 of the bowl 12 at pivot point 49. According to one embodiment, pivot point 49 lies substantially in the same plane as the axis of rotation 46 of apron 44, which simplifies the manufacturing process. In one embodiment, apron rams 48 are 29" x 5" (approx 73.7cm x 12.7cm) with a correspondingly large oil supply from a dedicated hydraulic circuit. Consequently, apron 44 is capable of forcing a large volume and mass of material into the bowl 12 of the scraper 10 thus making full use of the large capacity of the bowl. Also, apron 44 can force material situated up to approximately one metre in front of the cutting edge 14 into the bowl 12. Hence, the mounting position of the axis of rotation 50 of the apron 44 enables the ground scraper of the present invention to address one of the aforementioned prior art problems by reducing the amount of material left behind that has already been excavated. Furthermore, when the low profile apron 44 is in the raised or open position, the apron is high enough for the operator of the powered vehicle to see beneath the apron such that the operator has a line of sight to the cutting edge 14. Furthermore, apron 44 is shaped such that the operator of the powered vehicle has a line of sight over the apron to the bowl 12 when the apron is in an open position. This is facilitated by the higher position of the draft tube 62. These features render the improved scraper 10 of the present invention easier for the operator to use than many prior art scrapers. With reference to FIG 1 , to enable arms 47 of the apron to be coupled to rams 48 through sidewalls 18, sidewalls 18 comprise an aperture 91. To enable the apron 44 to be easily attached and detached from the bowl 12, each sidewall 18 includes a detachable wall portion 90, which can be bolted, or affixed in any other suitable detachable manner, to the remainder of the sidewall 18 and to upwardly extending reinforced portions 65.

With additional reference to FIGS 4, 6 and 7, the ground scraper 10 is coupled to a powered vehicle, such as a tractor, by a hitch assembly 56. Hitch assembly 56 comprises a pull 58 coupled to a drawbar 60. In this embodiment, drawbar 60 is bolted to pull 58, but any suitable alternative means for coupling the two may be employed. At an end opposite drawbar 60, pull 58 is coupled to draft tube 62. In this embodiment, pull 58 is welded to draft tube 62, but any suitable alternative means for coupling the two may be employed. At each end of draft tube 62, a first end of a draft arm 64 is coupled thereto, for example, by welding, and an opposite end of each draft arm 64 is pivotally coupled to sidewalls 18 of bowl 12 via trunnions 66 and caps 67 (shown in FIG 18) such that bowl 12 is located between the two arms 64. Draft arms 64 are substantially parallel with each other and are coupled substantially perpendicular to draft tube 62. Pull 58 is coupled to draft tube 62 at an angle of about 150-170° to the draft arms 64 to ensure that the operator has a good view of the cutting edge 14 and the bowl 12. A pair of hydraulic rams in the form of hitch assembly rams 68 are coupled between opposing ends of the draft tube 62 and upwardly extending reinforced portions 65 of the sidewalls 18. As the mass of the bowl 12 increases with increasing mass of excavated material held therein, hitch assembly rams 68 adjust the height of the bowl 12 relative to hitch assembly 56 and relative to the ground. The relatively high mounting position of the rams 68 keeps them above ground level and minimises the chances of the rams becoming clogged with dirt. Furthermore, since rams 68 are mounted to the draft tube 62, complex shapes and recesses in draft arms 64 are not required to accommodate the rams 68, thus avoiding unnecessary width in the improved scraper of the present invention.

Referring to FIGS 12-14, each wheel assembly 30 comprises a pivot pin 29 within a housing 35, which comprises replaceable bushings (not shown). Gussets 31 are welded to housing 35, which accommodate a pair of axles 28. Hubs 33 are mounted to axles 28 and tyres 34 have been omitted from FIGS 12 and 13 for the sake of clarity. Pivot pin 29 of each wheel assembly 30 is pivotally mounted to substantially vertical frame members 32 to allow the wheel assemblies 30 to pivot. Substantially vertical frame members 32 are welded to upper frame members 23 and lower frame members 25. From the mounting points of the wheel assemblies 30, substantially vertical frame members 32 taper toward upper frame members 23 and taper toward lower frame members 25. Additionally, upper frame members 23 taper upwardly and lower frame members 25 taper downwardly, as shown in FIG 14.

Such an arrangement enables the scraper 10 to follow contours of the ground whilst negotiating potholes, ruts and the like. This arrangement avoids undue stress being placed on the wheels 26, axles 28 and/or frame 22 to which the wheel assemblies 30 are mounted. The tapering of the upper and lower frame members 23, 25 and substantially vertical frame members 32 improves the extent of pivoting achievable by the walking wheels 26, whilst maintaining strength in the frame 22. A typical pivoting angle of the wheels 26 from the vertical is about 13°.

Whilst two wheel assemblies 30 are shown in the figures, it is envisaged that a single wheel assembly can be provided in an alternative embodiment comprising a wide tyre 34. Alternatively, more than two wheel assemblies 30 can be provided in a yet further alternative embodiment.

FIGS 15 and 16 show detail of the cutting edge 14 mounted to a mounting member in the form of mouldboard 15, which is mounted to the base 16 of the bowl 12 by welding or other suitable means such as bolting. Base 16 comprises an internal floor plate 80 and an external floor plate 82 and an angled, bisalloy backing plate 86 extending between the internal and external floor plates 80, 82. FIG 15 shows a toothed cutting edge 17 mounted to the cutting edge 14, which has teeth 19 for ripping up hard dirt. Cutting edge 14 is reversible so that when one edge becomes worn, the cutting edge can be reversed to utilize a fresh cutting edge without the need to completely replace the cutting edge. The scraper 10 can further comprise rippers (not shown) forward of the cutting edge 14 to loosen the ground prior to the cutting edge 14 scraping the ground material into the bowl 12. The arrangement of such rippers and their mounting to the improved scraper 10 would be familiar to one skilled in the art.

Referring to FIG 17, an axis of rotation 50 of the apron 44, which coincides with pivot means 46, is substantially parallel to, forward of and above a longitudinal axis of the cutting edge 14, i.e. the axis along which the cutting edge 14 extends. The cutting edge 14 is mounted via mouldboard 15 and extends substantially parallel to a transverse edge 52 of the internal floor plate 80 of the bowl 12. The axis of rotation 50 of the apron 44 is located in a plane extending from the longitudinal axis of the cutting edge 14. The plane is inclined between 15° and 30° to a vertical plane 54 extending from the cutting edge 14. The vertical plane 54 can extend from any point along the width W of the cutting edge 14, width W being shown in FIG 15. The inventor has determined that in a preferred embodiment of the present invention, the plane is inclined between 18° and 27°. However, the inventor has achieved the best results in a more preferred embodiment of the present invention in which the apron 44 is mounted such that its axis of rotation 50 lies in a plane inclined at 26° to the vertical plane 54. At this angle, the apron 44 of the improved scraper is able to push the largest amount of excavated/scraped dirt into the bowl 12 and is able to gather a large proportion of the excavated dirt located in front of the cutting edge 14.

According to one embodiment, the improved scraper 10 of the present invention can comprise a transverse beam 72 extending across the width of the bowl 12 between upwardly extending reinforced portions 65 of the sidewalls 18, as shown most clearly in FIGS 4 and 5. Transverse beam 72 acts as a mount for laser equipment known in the art used for guidance during the levelling process with the scraper 10. Transverse beam 72 also prevents flexing of the sidewalls 18 of the bowl 12.

The inventor has recognised that, particularly in wet conditions, very large clods of excavated ground material can be forced over the ejector door 36 by the forward motion of the scraper 10 and the further excavated ground material entering the bowl 12. The large mass of such clods can potentially damage the frame 22 and walking wheels 26. To address this problem whilst maintaining the large capacity of the improved ground scraper 10, the inventor has devised a detachable guard 74, which can be detachably mounted to sidewalls 18 of the bowl 12 to prevent such overflow. The guard 74 comprises a pair of side frames 75, a plurality of transverse frame members 76 extending between the side frames 75 across the width of the bowl 12 and a plurality of vertical members 77. Mesh 79 is fastened to the transverse frame members 76 and vertical members 77 by any suitable means, such as welding, to stop the overflow of excavated ground material. The guard 74 comprises an opening 78 below the mesh 79 to allow passage of the ejector door 36.

With reference to FIGS 18 and 19, each sidewall 18 of the ground scraper 10 comprises a hardwearing bisalloy check plate 21 to which a mounting block 69 is attached by any suitable means known in the art, such as welding. A trunnion 66 is mounted to mounting block 69 about which a draft arm 64 of the hitch assembly 56 pivots. Mouldboard 15, to which cutting edge 14 is mounted, is also welded to the bisalloy check plate 21. FIG 18 also shows one of the roller guides 42 on sidewall 18 to guide the ejector door 36, internal floor plate 80 and external floor plate 82. Hence, the improved ground scraper of the present invention thus provides a solution to the aforementioned problems associated with the prior art since the ground scraper of the present invention is more manoeuvrable than some of the prior art scrapers. Manoeuvrability is also improved by keeping the width of the scraper 10 and the lateral spacing of the wheels 26 to a minimum. However, a certain width needs to be maintained to provide the large bowl capacity of the improved ground scraper, making the ground scraper 10 suitable for both small and large applications. The notable ground clearance of the scraper of the present invention in comparison to some of the prior art scrapers provided by, for example, the angled hitch assembly 56 and large, pivotally mounted walking wheels 26, enables the scraper to be used on rough, undulating terrain and help the scraper to be utilized in wet conditions. The pivotally mounted walking wheels also prevent undue stress being placed on the frame, wheels or axles and prevent ruts being created in the levelled ground especially when turning. The tapered frame members allow a good pivoting range for the walking wheels 26. The reduced dimensions of the scraper also contribute to minimizing the turning circle of the scraper. This is desirable to minimize delays between runs and to enable the scraper to be used in more confined locations. The bowl 12 has a large opening to maximize the amount of excavated material entering the bowl. The powerful apron 44 and the relationship between the cutting edge 14 and the axis of rotation 50 of the apron 44 enables the bowl 12 to be filled to its maximum capacity and excavated material in front of the cutting edge 14 to be pushed into the bowl by the apron 44, thus minimising the amount of excavated material that is left behind and improving efficiency. The low profile apron causes the improved scraper 10 to have a lower overall height when the apron is open and provides the operator with better vision of both the cutting edge 14 and the bowl 12. The simple construction of the scraper in general and fewer moving parts than many of the prior art scrapers make the present invention more reliable than the prior art scrapers and cheaper to maintain. Features such as the interchangeable nature of the rams 38, 68 contribute to this by reducing the number of different types of spare parts required.

Throughout the specification the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention.

For example, variations in the size of the rams described herein may also produce satisfactory results. One or more weight sensors as known in the art and additional hydraulic circuits may be employed to aid the operator and enhance performance.

Claims

CLAIMS:

1. A ground scraper comprising: a bowl for holding excavated ground material; a cutting edge mounted at an open side of the bowl for excavating the ground material; a hitch assembly pivotally coupled to the bowl for coupling the ground scraper to a powered vehicle; and an apron pivotally mounted to the bowl for closing the open side of the bowl; wherein an axis of rotation of the apron is substantially parallel to, forward of and above a longitudinal axis of the cutting edge, the axis of rotation located in a plane extending from the cutting edge and the plane inclined between 15° and 30° to a vertical plane extending from the cutting edge.

2. The ground scraper of claim 1 , wherein the plane extending from the cutting edge is inclined between 18° and 27° to the vertical plane extending from the cutting edge.

3. The ground scraper of claim 1 , wherein the plane extending from the cutting edge is inclined at 26° to the vertical plane extending from the cutting edge. 4. The ground scraper of claim 1 , further comprising at least one hydraulic ram coupled between the hitch assembly and the bowl for adjusting a height of the bowl relative to the hitch assembly and the ground.

5. The ground scraper of claim 4, wherein the at least one hydraulic ram is coupled to a draft tube of the hitch assembly.

6. The ground scraper of claim 1 further comprising a frame attached to, and rearward of, the bowl and at least one pair of offset wheels pivotally mounted to the frame.

7. The ground scraper of claim 6, wherein the frame comprises an upper frame member having an upwardly tapering cross section.

8. The ground scraper of claim 6, wherein the frame comprises a lower frame member having a downwardly tapering cross section.

9. The ground scraper of claim 6, wherein the frame comprises a pair of substantially vertical frame members extending between an upper frame member and a lower frame member, the at least one pair of offset wheels pivotally mounted between the substantially vertical frame members.

10. The ground scraper of claim 9, wherein the substantially vertical frame members taper upwardly from a mounting point of the at least one pair of offset wheels. 11. The ground scraper of claim 9, wherein the substantially vertical frame members taper downwardly from a mounting point of the at least one pair of offset wheels.

12. The ground scraper of claim 1 , wherein a mounting point for at least one hydraulic ram coupled between the bowl and the apron is in substantially the same plane as the axis of rotation of the apron.

13. The ground scraper of claim 4, wherein the at least one hydraulic ram coupled between the hitch assembly and the bowl and the at least one hydraulic ram coupled between the bowl and the apron are interchangeable.

14. The ground scraper of claim 1 , further comprising a guard detachably mountable to sidewalls of the bowl to prevent overflow of excavated material from the rear of the bowl.

15. The ground scraper of claim 1 , further comprising a detachable wall portion to enable the apron to be attached and detached from the bowl.

16. The ground scraper of claim 1 , wherein an operator of the powered vehicle has a line of sight to the cutting edge when the apron is in an open position. 17. The ground scraper of claim 1 , wherein an operator of the powered vehicle has a line of sight to the bowl when the apron is in an open position.