Ground engaging tool

Abstract

A ground engaging tool is provided and comprises a blade. The tool includes means for controlling the engagement depth of the blade in the ground. The height of the blade and / or the pitch of blade is

Description

The present invention relates generally to a tool and particularly, although not exclusively, to a ground engaging tool. All ground engaging blades used on bulldozers, graders, mine ploughs and the like are heavy items that have three requirements: • They need their masses and working forces physically supporting • They need positioning at an accurate depth • The above needs doing, advantageously with minimum energy and / or power whilst progressing at the maximum possible speed. Military mine clearing operations often involve mine clearing ploughs which may clear the whole width of a vehicles path, so called ‘full width’ ploughs or they may only clear two narrower paths just wide enough for a vehicle’s tracks or wheels, so called ‘track width’ ploughs. Track width ploughs leave the ground between the two cleared paths undisturbed. These ground engaging tools fit to the front of host vehicles and feature comb like tines fitted to a main blade. The tines rake through the ground excavating larger buried objects such as landmines but also excavate considerable amounts of soil. The blade geometry is such that the soil and included objects are excavated from the ground and a side cast echelon angle means they flow sideways to be deposited in a spoil heap to the outside of the vehicle’s path. The construction of bulldozers and graders with wheels and tracks attached directly to their chassis (i.e. without any compliant suspensions) provides ample physical support. The un-sprung vehicle chassis also provides a reasonably steady ground reference that a blade can be positioned relative to although the vehicle chassis sit upon ground that the blade has just formed, it is not the same ground that exists ahead of the blade and this may be an important discrepancy. These vehicles also progress relatively slowly so adjustments to the blade position relative to the vehicle chassis can be made relatively slowly and thus with low power. However, military vehicles typically have sprung suspension systems which are necessary for high speed operation and also have limited spare power take off available for applique tools. 5 Sprung chassis do not provide reliable ground references. Mine plough blades are thus often attached to such vehicles via freely moving kinematic linkages and use their own ground reference in the form of support skids attached to the plough blade either directly or via some further mechanical linkage. The mine plough blade is thus able to move freely, in a way controlled by its linkage(s) and skid, relative to the host vehicle 10 chassis. The skids slide across the ground’s surface, the blade mass and work forces being partially supported on this skid and the tine tips being positioned relative to these and so maintained at a fixed depth. These skids, and any linkages that attach them to the plough blades, are typically passive, requiring no power supply or energy source. 15 A passive skid cannot be positioned behind the plough blade because the level of the ground at this location is not representative of the ground level ahead of the blade and immediately above the tines. This is because the amount of soil the plough excavates CM varies depending on many factors such as the soil type, moisture content and 1— vegetation and can change randomly from one location to the next. A location behind 20 the blade is thus unsuitable for a passive depth reference skid. CO T"— The skids cannot be located at the outer edge of the blades because they would be overwhelmed by the side cast soil making this location unsuitable for a depth reference skid. 25 The skids of a track width plough are typically attached directly to the inner edge of each plough blade. The ground here is undisturbed by the operation of the plough and can provide firm support, the excavated soil and mines flow outwards, away from this location, so do not influence the skid, and yet the location is very close to the tine tips 30 and thus provides a good quality ground reference. A full width plough has no inner edge location, its blade extends the full width of the vehicle. The skids of a full width plough are thus typically attached to long arms which project forwards over the emerging soil flow to place the skids on ground some 35 distance ahead of the plough tines. This undisturbed ground can provide firm support, but its location offset some distance from the tines means it may still be an unreliable reference. For instance, the ground ahead may be significantly higher or lower than the ground local to the tines. A major disadvantage of inner edge and forward ground reference skids in a mine clearing plough is their potential to depress the detonator of land mines causing them to explode. The present invention seeks to provide improvements in or relating to ground engaging tools. An aspect of the present invention provides a ground engaging tool comprising a blade having a plurality of tines, in which the blade includes trailing, ground-contacting support means for at least partially supporting the blade and for at least partly influencing the height thereof, in which the ground-contacting support means is attached to the rear of the blade and is movable relative to the blade, and in which the tool comprises a non-contact sensor for measuring the ground, the non-contact sensor is attached to the blade at a fixed height above the tine tips, and rearward of the tine tips, and engagement depth is determined as the depth of a tip relative to prevailing ground, and in which the height of the blade and / or pitch of the blade is adjustable to control the engagement depth. The trailing, ground-contacting support means comprise one or more skids, rollers, wheels, continuous or caterpillar tracks or other support surfaces or combinations thereof. For example caterpillar tracks may be used instead of a sliding skid; and generating some power from this being pushed along. Combinations of different support means may also be used e.g. a combined roller-skid design. Embodiments are based on the provision of ground-contacting skids (or the like support means - see above) which are trailing i.e. it / they trail behind a groundengaging tool. Some embodiments are concerned with / provide for adjusting blade pitch; for example trying to control the engagement depth of a (e.g. echeloned) blade and having to adjust the height of the blade and / or the pitch of the blade to do this. In some embodiments the apparatus precedes a host vehicle. The skid may be movable relating to the blade. For example the skid may be movable by translation and / or rotation relative to the blade. In some embodiments, for example, the skid is hinged to the blade and its orientation relative to the blade can be adjusted. The tool may comprise a powered actuator, such as a ram or cylinder, for moving the skid relative to the blade. The skid may be positioned on the blade within the engaged ground width. The tool may comprise means for (actively) adjusting the pitch of the blade, for example one or more powered actuators for adjusting the pitch of the blade. The tool may comprise one or more top links for adjusting the pitch of the blade. The tool may comprise one or more lower booms for adjusting the pitch of the blade. The tool may comprise means for measuring the ground and means for measuring the position of the blade tip relative to the ground, whereby the engagement depth can be determined. The tool may comprise means for measuring / calculating / predicting the ground profile in advance of the blade. The tool may comprise a sensor located at a fixed position relative to the blade tip. For example fixed to the top of the blade and therefore being a fixed distance from the blade tip. The tool may, for example, comprise a non-contact optical sensor. In some embodiments the tool may comprise a kinematic linkage, allowing the blade to move freely, unpowered, to approximately a required engagement depth. The tool may further comprise a trailing skid and means for blade pitch adjustment that can be used to provide optimisation of blade position. The tool may be or may form part of a plough, dozer or grader. The present invention also provides a vehicle fitted with one or more tools or ploughs as described herein. Also described is method for moving a ground engaging tool blade at a generally constant depth through undulating terrain of varying soil strength, comprising measuring the ground engagement depth of a tool blade tip and dynamically adjusting the height of the blade and / or the pitch of the blade to actively control the depth of the blade tip relative to the ground. The method comprises the step of providing trailing, ground-contacting support means (such as one or more skids, rollers, wheels, tracks or the like) for at least partially supporting the tool blade and using the support means to at least partially determine the height of the blade, with the ground-contacting support means attached to the rear of the blade and being movable relative to the blade. Also described is a control system for moving a ground engaging tool blade through the ground whilst using minimum energy, comprising means for measuring the depth of a tool blade tip and using the measured data to calculate the best adjustments to maintain a preferred blade pitch and tip depth whilst using a minimum amount of energy to achieve this as the vehicle and blade moves forwards. The tool may comprise one or more trailing skids, wheels, rollers, tracks or the like for influencing blade height and one or more top cylinders for influencing blade pitch, in which the system uses measured data to calculate the best adjustments to the skid / s and / or top link cylinder / s. Some aspects and embodiments may provide or relate to a mine plough with supporting heel skid (or other support means) attached to the rear of the blade and with the blade / skid assembly connected to the host vehicle by a linkage e.g. with a lower boom and a top link. In some embodiments a skid or the like is hinged to the blade and its orientation relative to the blade can be adjusted by a powered actuator (the “skid” cylinder). The top link may also be telescopic and a powered actuator can adjust its length (e.g. a top link cylinder). 5 A non-contact sensor (e.g. Lidar, Radar etc) is used to measure the ground profile ahead of the blade and the position of the blade relative to this. This sensor may be attached directly to the blade or it may be attached to the vehicle chassis. There may be instrumentation to measure the position of the linkage and / or forces within it. 10 A control system algorithm may be provided and use the measured data to calculate the best adjustments to the skid and top link cylinders to maintain a preferred blade pitch and tine depth whilst using a minimum amount of energy to achieve this as the vehicle and plough moves forwards. 15 For some aspects and embodiments the problem addressed is how to move a ground engaging tool (e.g. a landmine clearing plough) at a constant depth through undulating CM terrain of varying soil strength and without applying load to the ground ahead of, or to 1— either side of, the ground engaging tool whilst using minimum energy to operate the 20 tool and progressing through the terrain at maximum speed. CO T"— Different aspects and embodiments of the invention may be used separately or together. 25 Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with the features of the independent claims as appropriate, and in combination other than those explicitly set out in the claims. Each aspect can be carried out independently of the other aspects or in combination with one or more of 30 the other aspects. The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: 35 Figure 1 is a plan view of a mine plough fitted to a vehicle; Figure 2 is a front view; Figure 3 is a side view and a centre section view with mechanism in a typical operating orientation on level ground; Figure 4 is an isometric view; Figure 5 is a side view and a centre section view with mechanism in another typical operating orientation; Figure 5b illustrates why some embodiments of the present invention are suitable for sprung vehicles; Figure 6 shows what happens when the ground falls away if neither the skid nor the top link cylinders are adjusted; Figure 7 shows what can be achieved by adjusting the top link cylinder length; Figure 8 shows views of the plough; and Figure 9 illustrates a heel plough sensing system formed in accordance with the present invention. Example embodiments are shown and described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein. Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate. The invention is not limited in the design and shape of the structure shown in the drawings. The terminology used herein to describe embodiments is not intended to limit the scope. The articles “a,” “an,” and “the” are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the 5 singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and / or “including,” when used herein, specify the presence of stated features, items, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and / or 10 groups thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art 15 and not in an idealized or overly formal sense unless expressly so defined herein. Figure 1: CM A plan view of a mine plough 10 fitted to a vehicle 15. “ 20 The major parts are visible. Shows the sensor positions and how their line of sight is at the middle of the blade. The plough has a left blade assembly 20a and a right blade assembly 20b which are generally identical mirror images and which can move independently. They create a V 25 shaped blade which will side cast soil and landmines to either side of the vehicle’s path. For each blade assembly 20a, 20b a top link 22a, 22b and lower boom 24a, 24b, skid 26a, 26b, skid cylinder 28a, 28b, main blade 30a, 30b and tines 32a, 32 are visible. 30 Each blade assembly 20a, 20b has a sensor 34a, 34b whose line of sight 36a, 36b is shown aligned with the middle of the respective main blade. Figure 2: 35 A front view. Figure 3: Side view and a centre section shows the vehicle with articulating suspension arms and all the major plough parts. Shown in a common operating depth on level ground: The tine tips are 300mm below ground; the plough is excavating 150mm so the skid and vehicle sit on ground 150mm below the original ground. The skid cylinder is the correct length for this situation. The top link cylinder is the correct length so the plough blade pitch is correct and all of the tines are at the correct depth. Side view and centre section view with mechanism in a typical operating orientation on level ground. Tines are all at 300mm deep and plough is excavating 150mm of soil. Skid and vehicle are in contact with the excavated ground level. Other embodiments (not shown) use a track, roller, wheel or the like in place of a skid, for example. Skid cylinder is at the correct length to support the tines at 300mm deep. Top link cylinder is at the correct length so that blade pitch is correct which in turn means that all the tines are at the same depth. Figure 4: An isometric view of the arrangement. Shows major parts. Figure 5: Level ground with the plough tines at 300mm deep but the plough is only excavating 50mm of soil. The skid and vehicle are on ground 50mm below the original ground. The skid cylinder has adjusted its length to achieve this. The top link and lower boom kinematic mechanism has moved (notice that the top link is approximately horizontal in this view when it sloped backwards in Figure 3) because the position of the vehicle relative to the plough blade is different because of the difference in soil excavation. Side view and centre section view with mechanism in another typical operating 5 orientation. Compared to Figure 3, this is still level ground but for whatever reason the plough is only excavating 50mm of soil. This can happen because of a different soil type, different soil strength or different vegetation, etc. In this figure, the skid cylinder has changed length to adjust the skid position to support 10 the tines at 300mm deep. If the plough had moved from the soil of Figure 3 to this soil and the skid had not been adjusted, then the tine depth would now be incorrect leading to inconsistent land mine removal. The top link cylinder may also have changed length so that blade pitch is correct which 15 in turn means that all the tines are at the same depth. Figure 5b: CM Figure 5b illustrates why some embodiments of the present invention are suitable for 1— sprung vehicles (when a conventional “bulldozer” architecture - with a blade connected “ 20 rigidly to the vehicle chassis - would not work so well). CO T"— Level ground with the plough tines at 300mm deep and still excavating 50mm of soil. Compared to Figure 5 the blade is in the same position relative to the ground and the 25 skid cylinder length is unchanged. The vehicle chassis has, however, moved upwards and rotated backwards on its sprung suspensions as can happen when ploughing forces increase in stronger soils. 30 The top link and lower boom kinematic mechanism has moved (freely) to suit the new position of the vehicle relative to the blade. The top link cylinder length is adjusted so the blade pitch is correct and all the tines are at the same depth. 35 Figure 6: Shows what happens when the ground falls away if neither the skid nor the top link cylinders are adjusted. The plough is still excavating 50mm of soil. 5 The blade is incorrectly pitched backwards relative to the sloping ground it is adjacent to. The tines are all at different depths ranging from too shallow to too deep. 10 Shows what could happen if the plough shown in Figure 5 moves onto ground which slopes downwards and neither the skid cylinder nor the top link cylinder lengths are adjusted. The tine depths are not correct which may result in different amount of 15 excavation and importantly inconsistent landmine removal. In this example the plough is still excavating 50mm of soil but this could vary because the plough depth has changed as well as with changes in soil type. Incorrect depth and / or pitch might also be caused when the plough moved onto ground sloping upwards or a step up or step down. 20 Figure 7: Shows what can be achieved by adjusting the top link cylinder only. The top link cylinder has extended. 25 The blade has corrected its pitch so that all tines are at the same depth. The plough is still excavating 50mm of soil. 30 The skid cylinder has not moved. The skid is supporting the blade on the sloping terrain. Shows what can be achieved by adjusting the top link cylinder length. 35 Compared to Figure 6, the top link cylinder has extended and the blade pitch relative to the sloping ground it is on has been corrected so all the tines are at the same depth. The skid cylinder may also have adjusted in length if that constant depth of all the tines is not the required depth (e.g. 300mm) i.e. because of a change in the volume of soil excavated. 5 Similar adjustments can be used to correct depth and pitch with the plough moved onto ground sloping upwards or a step up or step down. Figure 8: 10 Shows detail views of the plough. Major components are: mounting plate, top link cylinder, lower boom, main blade, tines, sensor, skid, skid cylinder, skid hinge. 15 This embodiment achieves changes to the blade pitch by adjusting the top link length. This could also be achieved by adjusting the lower boom length, or by moving the location of the joints between these parts and the mounting plate and / or the blade. CM 1— This embodiment uses a skid hinged to the blade. Another solution might be a skid “ 20 attached to a telescopic mechanism which moved it up / down relative to the blade. In a QQ further embodiment a linkage, for example a parallel linkage, may be provided which T"— provides a skid which rotates and translates. In operation, the sensor which might be a 2D LiDAR, RaDAR, SoNAR or other sensor, 25 measures the topology of the ground ahead relative to the blade. As the vehicle advances and the blade moves depending on the terrain, a data processing algorithm generates a mathematical record of this topology and blade position. This might include using Simultaneous Localisation And Mapping (SLAM) techniques which are well understood. This data is used to determine if the blade is currently at the correct depth 30 and pitch and provide a target depth and pitch that is desired to be achieved some small distance ahead. This next target may be the perfect desired depth and pitch or may be some intermediate target. A control algorithm determines the most efficient adjustments to the skid and top link cylinders to achieve this goal. 35 A single 1D sensor taking measurements of the ground as the system advances can also be used to generate a suitable 2D data set. Alternatively, a 3D sensor would also provide ample information. Ideally any sensor used in a mine clearing application would be a none contact sensor so there would be no possibility to depress landmine detonators. It may be desirable in some situations to use a contact sensor e.g. to physically push aside vegetation 5 obscuring measurement of the real ground surface. However, the load such a contact sensor applied to the ground could be very small and in the context of landmine detonators negligible. The control algorithm might compute a skid adjustment based on the current and target 10 tine depths i.e. to control the height position of the whole blade assembly relative to the ground. The control algorithm might compute a top link adjustment based on the current and target pitch requirements i.e. to control the variation in tine depths across the blade 15 width. The control algorithm might be given, or might establish, a tolerance for acceptable depth and / or acceptable pitch and may decide not to energise any actuators unnecessarily if the blade position is within tolerance either in its current position or is 20 predicted to be within tolerance some small distance ahead. Such a prediction may be based on the measured terrain and / or the measured motion of the system and / or the forces within the system. The control system might monitor the power drawn from the power supply and adapt its 25 strategy if there is some limit to this supply which limits the ability of the actuators to react as requested. The control system might monitor the traction of the host vehicle and adjust the plough if required. E.g. if the vehicle is unable to push the plough in the current conditions and 30 its tracks slip excessively it may be desirable to reduce the working depth to prevent this. The control system might monitor the forces in the plough mechanism and adjust the plough if required. E.g. the forces from an extremely adhesive soil sliding up the plough 35 blade surface may be sufficient to lift the blade assembly, making the skid loose contact with the ground and reducing the tine depth. It may be desirable to adjust the blade pitch to prevent this. Forces could be measured in the assembly by strain gauges attached at appropriate places and / or by measuring pressures in hydraulic actuators. The actuators may be hydraulic or electrically powered. This embodiment is a side cast blade for a mine clearing plough. If the blade were a straight dozer blade with a heel skid then the depth of its cutting blade tip could be adjusted by changing the length of the skid cylinder (which would raise or lower the whole blade) or by changing the length of the top link cylinder which would change the pitch of the blade, rotating it about the point where the skid contacts the ground and thus also changing the tip depth as this is some distance ahead of the skid contact patch. The control algorithm might compute the optimum change to these 2 cylinders for most efficient operation. Differences in height between the blade and the vehicle are tolerated because of the kinematic linkage formed by the top link and lower boom which is able to move freely. This free movement means cylinder adjustments are not necessarily or continuously required for all changes in terrain and potentially no energy is consumed negotiating such terrain whilst the tine tip depths are still maintained. In operation, the top link cylinder will usually be in tension and the skid cylinder will usually be in compression. Thus to retract the top link cylinder or extend the skid cylinder will consume energy. However, if the desired change is to lengthen the top link cylinder or shorten the skid cylinder then energy can be generated from these actions which may be stored and reused to reduce the systems net energy requirement. This embodiment shows a two-piece plough with each side able to operate independently to move up or down freely on the linkages formed by the top links and lower booms and to be optimised by independent skids and pitch adjustment. This particular embodiment does not allow the individual blades to roll left or right. The advantages of the combined adjustable heel skid and adjustable blade pitch could equally apply to a single V-shaped or straight blade and such a system may also benefit from an additional roll freedom, e.g. it could be a single wide blade with two separate heel skids, one on each side of the blade. Alternatively, systems comprising three or more independent blade sections are possible. Figure 9: Figure 9 illustrates a heel plough sensing system formed in accordance with the present invention. In this embodiment a non-contact sensor such as a 2D LiDAR scanner is attached directly to the plough blade at a fixed height above the tine tips. In the top diagram of figure 9, this scanner has a field of view and coordinate system such that it can measure the X and Y coordinates of 2 ground points, A and B, ahead of the blade. In the middle diagram of figure 9, the blade (with it’s the sensor and it’s coordinate system) has moved forwards. The control system, which may use a SLAM algorithm, is able to remember the absolute position of points A and B i.e. it does not just remember the coordinates of A and B as measured in the top diagram, the SLAM algorithm constantly updates the coordinates of points A and B as the blade and coordinate system move so that at this moment in time the control system can know the distances A1 and B1 even though points A and B points are no longer in the sensors field of view. The depth of the tine tip is the (fixed) height of the sensor minus the value A1 or B1 because on level ground A1 = B1 and either of these would produce the same answer. The lowest diagram in figure 9 shows the blade in some arbitrary orientation where it is clear that tine tip depth is best calculated by using the average value of A2 and B2 and also that blade pitch can be quantified using the value of A2 minus B2. Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A ground engaging tool comprising a blade having a plurality of tines, in which the blade includes trailing, ground-contacting support means for at least partially 5 supporting the blade and for at least partly influencing the height thereof, in which the ground-contacting support means is attached to the rear of the blade and is movable relative to the blade, and in which the tool comprises a non-contact-sensor for measuring the ground, the non-contact sensor is attached to the blade at a fixed height above the tine tips, and rearward of the tine tips, and engagement depth is determined 10 as the depth of a tip relative to prevailing ground, and in which the height of the blade and / or pitch of the blade is adjustable to control the engagement depth.

2. A tool as claimed in claim 1, in which the trailing, ground-contacting support means comprise one or more skids, rollers, wheels, continuous or caterpillar tracks or 15 other support surfaces, or combinations thereof.

3. A tool as claimed in claim 1 or claim 2, in which the non-contact sensor CM comprises a 2D LiDAR scanner.“ 20 4. A tool as claimed in any preceding claim, in which the trailing, ground-QQ contacting support means is a skid, and the skid is hinged to the blade.

5. A tool as claimed in claim 4, in which the ground-contacting support means is movable by translation and / or rotation relative to the blade.

256. A tool as claimed in claim 4 or claim 5, in which the ground-contacting support means is hinged to the blade and its orientation relative to the blade can be adjusted.

7. A tool as claimed in any of claims 4 to 6, comprising a powered actuator for30 moving the ground-contacting support means relative to the blade.

8. A tool as claimed in any of claims 4 to 7, in which the ground-contacting support means is positioned on the blade within the engaged ground width.35 9. A tool as claimed in any preceding claim, comprising means for adjusting thepitch of the blade.

10. A tool as claimed in claim 9, comprising one or more powered actuators for adjusting the pitch of the blade.

11. A tool as claimed in any preceding claim, comprising one or more top links for adjusting the pitch of the blade.

12. A tool as claimed in any preceding claim, comprising one or more lower booms for adjusting the pitch of the blade.

13. A tool as claimed in any preceding claim, in which the ground-contacting support means is a skid and the tool comprises a skid cylinder.

14. A tool as claimed in any preceding claim, comprising means for measuring the ground profile in advance of the blade.

15. A tool as claimed in claim 13 or claim 14, comprising a sensor located at a fixed position relative to the blade tip.

16. A tool as claimed in claim 15, comprising a non-contact optical sensor.

17. A tool as claimed in any preceding claim, comprising a kinematic linkage allowing the blade to move freely, unpowered, to a required engagement depth.

18. A tool as claimed in claim 17, comprising a trailing, ground-contacting support means and means for blade pitch adjustment providing optimisation of blade position.

19. A tool as claimed in claim 18, in which the ground-contacting support means comprises one or more trailing skids.

20. A tool as claimed in any preceding claim, in which tool is or forms part of a plough, dozer or grader.

21. A vehicle fitted with one or more tools as claimed in any preceding claim.

Images