Positional control system

Abstract

A working machine comprising an implement pivotable with respect to a loader arm and an actuator arranged to pivot the implement about a physical angular range of motion; wherein the hydraulic system

Description

08 07 25 FIELD The present teachings relate to a positional control system for a working machine. In 5 addition the present teachings relate to working machine and a method of operating a working machine. BACKGROUND Loaders are a type of working machine comprising a working arm pivotable about a horizontal axis and extending forward of a body of the machine. The body comprises a 10 ground engaging propulsion structure (such as wheels) and, usually, an operator station. An attachment, such as a shovel (sometimes referred to as a bucket), is mounted on the free end of the arm with its opening facing forward, and is also pivotable about a horizontal axis with respect to the arm. This enables the loader to scoop and move loose material such as soil, aggregates, sand and deposit it in other locations on worksites. 15 Four-in-one shovels are also known, and add the ability to doze, level, grade and grab material. However it requires operator skill to orientate the 4-in-l shovel to perform these functions when viewed from an operator station. This orientation may need to be re-done many times a day if a machine is performing different operations on a worksite, and if it is time-consuming this is harmful to machine productivity. 20 When grading materials, it is known to use a levelling device to help an operator achieve a required level, for example, if they are levelling aggregate for a sub-base of a road. Such levelling devices have a receiver mounted in a fixed vertical relationship with a lower surface of a grading device such as a dozer blade. Levelling devices operate by sensing laser light emitted by a transmitter, determining if it is intercepting the sensor too high or 25 low, and showing an operator whether they should lift or lower their blade to correct the discrepancy. The receiver therefore needs to be mounted in a relatively high, exposed position for the light to be incident on the receiver. The receiver is therefore mounted on a pole projecting above, and fixed relative to, the blade. On purpose-built bulldozers and graders this is not 30 problematic as little tilting of the dozer blade occurs. However, if grading with a loader and 4-in-l shovel, a problem may arise if the pole and receiver is attached to the shovel whilst performing other operations, such as loading material into a trailer, for example. Damage may be caused to the receiver in this scenario due to high stopping inertia if the shovel is rapidly shaken to dislodge stuck material, for example, or if the operator 35 accidentally hits a foreign object. 08 07 25 The present teachings seek to overcome, or at least mitigate, one or more problems of the prior art. SUMMARY OF THE INVENTION An aspect of present invention relates to a working machine according to claim 1. Optional 5 features of these aspects are provided by the dependent claims. According to a first aspect of the present teachings, there is provided a working machine comprising: a body; 10 a loader arm pivotably mounted to the body; an implement or implement carriage pivotable with respect to the loader arm; an actuator arranged to pivot the implement about a physical angular range of motion; and a hydraulic system optionally arranged to control the motion of the actuator under 15 the influence of an operator input device; the hydraulic system optionally being provided with a positional control arrangement to define first and second adjustable detent positions to selectively restrict or delineate a range of motion of the implement with respect to the loader arm to less than the physical angular range of motion in two directions. 20 Advantageously, this provides a way of ensuring a working machine implement can be set to two positions or intermediate positions without an operator requiring significant skill or judgement to do so. Such functionality may be useful, e.g., if an inexperienced operator is required to perform a grading operation using a 4-in-l or clam shell type shovel. 25 The first and second detents may be stops to hydraulically limit movement in first and second opposing directions respectively. By providing stops, there is no risk of an operator inadvertently moving outside of the 30 desired range being set. The positional control arrangement may be configured to be selectively disengageable and / or overridable by an operator. 35 Advantageously, this enables an operator to easily revert a working machine to a normal mode of operation in which the full physical range for the particular pivotable connection 08 07 25 is available. This may be of benefit if the working machine has multiple uses such as digging or materials handling in addition to the grading function. The positional control arrangement may comprise a body moveable in conjunction with 5 pivoting of the pivotable connection and a switch or sensor associated therewith arranged to determine the first detent position. Advantageously, this enables the positional control without requiring complex sensing arrangements. 10 The body may be linearly moveable. The body may be a bar, plate or rod having a predetermined position sensed by the switch or sensor, e.g. a proximity switch. 15 The relative physical positions of the body and the switch or sensor may be adjustable so as to alter at least one of the detent positions. Advantageously, this may allow the implement to be set to one of the desired detent 20 positions and then the body and / or switch adjusted so the detent coincides with that position. The working machine may comprise a second body moveable in conjunction with pivoting of the pivotable connection and a second switch or sensor associated therewith arranged 25 to determine the second detent position. The hydraulic system may comprise a spool valve controlling fluid flow to the hydraulic actuator and wherein upon achieving the first or second detent positions, flow through the spool valve is adjusted. 30 Advantageously, this provides an effective way of achieving positional control. The hydraulic system may comprise a pilot line control and the positional control arrangement alters pilot pressure in the pilot line to the spool valve to adjust the flow. 35 Advantageously, this enables the control to be achieved at relatively low cost without requiring full electro-hydraulic control of the hydraulic system. The altering of pilot pressure may comprise relieving pressure in the pilot line. 08 07 25 The working machine may further comprise a controller and an electro-hydraulic spool valve. 5 A sensor may signal the controller and the controller may signal the electro-hydraulic spool valve when one of the first and second detent positions is reached. The controller may additionally signal operation of a further hydraulic service. 10 Advantageously, this may enable the more sophisticated use of the system, for example, to perform a grabbing operation of material in front of a grading blade whilst pivoting the blade. The implement may be a 4-in-l shovel and the controller may signal pivoting of a clam 15 shell portion of a 4-in-l shovel simultaneously with movement of the of the hydraulic actuator between the first and second detent positions. The implement may be a 4-in-l shovel and wherein the first and second adjustable detent 20 positions may provide a level position of the 4-in-l shovel and a grading position of the 4-in-1 shovel. Advantageously, this arrangement allows the easy and relatively unskilled operation of the working machine to perform additional functions in a semi-automated way. 25 A second embodiment of the present teachings provides a method of operating a working machine according to any preceding claim comprising the steps of setting the first and second detent positions and operating the shovel between these positions. 30 A third embodiment of the present teachings provides a working machine comprising: a body; a loader arm pivotable about a substantially horizontal axis to the body, an implement pivotably mountable with respect to the loader arm; a positional control system comprising an adjustable detent position for the 35 pivotable connection of the implement to the loader arm; and a level receiver mounted to the loader arm. Advantageously, this arrangement enables an operator to set a fixed vertical relationship between a lower edge of an implement and the level receiver (e.g., a laser level) whilst 40 mounting the indicator in a location where it is less susceptible to damage from foreign 08 07 25 objects and / or inertial forces acting on the implement in certain situations such as when an operator rapidly cycles the shovel to free stuck material. The detent may be a stop preventing movement in at least one direction. 5 The positional control system may provide a hydraulic implementation of the detent. The system may comprise a body moveable in conjunction with pivoting of the pivotable connection and a switch or sensor associated therewith to determine the first detent 10 position. The body may be linearly moveable. The body may be a bar, plate or rod having a predetermined position sensed by the switch 15 or sensor, e.g. a proximity switch. The level receiver may be mounted to an elongate pole extending generally vertically from the loader arm. 20 The working machine may further comprise a feedback arrangement to automatically adjust the level of the implement based on a level sensed by the level receiver. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments will now be described with reference to the accompanying drawings, in 25 which: Figure 1 is a side view of backhoe loader working machine of the present teachings comprising a shovel; Figure 2 is an isometric view of the shovel of Figure 1 in a closed position; 30 Figure 3 is an isometric view of the shovel of Figure 1 in an open position; Figure 4 is a perspective view of a front portion of the backhoe loader of Figure 1; Figure 5 is a diagram of an electrical circuit of the working machine of the present teachings; Figure 6 is a diagram of a hydraulic circuit of the working machine of the present teachings; 35 Figures 7, 8 and 9 are side views of the shovel of Figure 1 at different angles suitable for performing different tasks; and Figure 10 is a schematic illustration of an electro-hydraulic embodiment of the present teachings. 08 07 25 DETAILED DESCRIPTION OF EMBODIMENT(S) In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of various embodiments and the teachings. However, 5 those skilled in the art will understand that: the present teachings may be practiced without these specific details or with known equivalents of these specific details; that the present teachings are not limited to the described embodiments; and, that the present teachings may be practiced in a variety of alternative embodiments. It will also be appreciated that well known methods, procedures, components, and systems may not 10 have been described in detail. Terms such as front, rear, lateral, side, upper and lower as used herein are with reference to the orientation of the working machine on level ground. They are used for ease of understanding and should not be taken as limiting. 15 With reference to Figure 1 a working machine in the form of a backhoe loader 10 of the present teachings is illustrated. A backhoe loader 10 is a known type of loader. The backhoe loader 10 comprises a loader arms 12 pivotable about a horizontal axis and extending forward of, and either side of, a body 14 of the machine. The body 14 comprises 20 a ground engaging propulsion structure 16 (wheels in this embodiment, but tracks in other embodiments) and an operator station 18 in the form of an enclosed cab. A shovel 20 is mounted on the free end of the loader arm 12 with a mouth or opening 21 facing forward. The shovel is pivotable about a horizontal axis with respect to the loader arm 12 by a hydraulic actuator and linkage assembly as is well known, and indicated generally at 15. 25 This arrangement enables the backhoe loader 10 to, for example, drive the shovel 20 into a pile of material when it is lowered and scoop the material into the shovel, then move the machine, lift the arm 12 and tip the material from the shovel at another location, such as into a trailer (not shown). As such it is a versatile tool that is found on various worksites including construction sites, quarries, farms etc. The backhoe loader is powered by a prime 30 mover, such as an internal combustion engine, and / or one or more electric motors (not shown). The backhoe loader 10 additionally comprises a rear mounted backhoe 22, that is a form of excavating arrangement that comprises a boom 24 and dipper arm 26 (stick) that are 35 pivotable about horizontal axes, with the boom also being slewably mounted to the body 14. The free end of the dipper is typically fitted with a smaller bucket 28 and or other 08 07 25 attachments (not shown) to be used for trenching operations and the like. These may also be carried between worksites in the front shovel 20. Whilst a backhoe loader 10 is described, it will be appreciated that the present teachings 5 are also applicable to other types of working machines with loader arms, such as wheel loaders, skid-steer loaders, tracked loaders, articulated telescopic loaders and telehandlers. These machines do not usually comprise a backhoe. The shovel 20 is typically interchangeable with other attachments such as forks, grabs, 10 and the like, to perform further functions. Referring now to Figures 2 and 3 the shovel 20 is a "four-in-one" or "clamshell" shovel which adds further functions over and above a conventional shovel. The four-in-one shovel 20 is essentially separated into two portions. A rear portion 30 comprises a generally 15 upright wall 32 with a forwardly inclined lower linear edge acting as a blade 34 and relatively small side walls 35. A mounting interface 36 to the loader arm is provided 12 on its rear face, as is visible in Figure 1. A U-shaped front portion 38 is pivotably mounted near its upper extent to the rear portion 20 30. Upright parts 40 of the U form side walls of the shovel 20 and a lower part forms a base wall 42. The base wall 42 comprises a generally straight leading edge 44, sometimes fitted with forwardly projecting teeth (not shown). Teeth are useful when using the shovel to handle more solid material such as boulders and compacted earth. The base wall also comprises a trailing edge 45 which is also generally straight and contacts the rear portion 25 30 proximate its lower linear edge 34 when in the closed position of Figure 2. When the front portion 38 is closed against the rear portion 30 as shown in Figure 2, part of the side walls 40 of the front portion 38 nest inside the side walls 35 of the rear portion 30 and the four-in-one shovel 20 is essentially functionally the same as a standard shovel, 30 whose internal volume can be used to scoop up and hold material therein. When the front portion 38 is pivoted open by a linear actuator 98 (Figure 10) as depicted in Figure 3 this exposes the upright wall 32 and lower edge 34 of the rear portion 30, so the rear portion can be used as a dozer blade to push and level material. In addition, with 35 the front portion 38 open the whole shovel 20 can be tilted forward and the base of the front portion 38 used as a grading tool (see Figure 8). Finally. By closing the front 38 and rear portions 30 around material the shovel can be used as a grab or grapple. In this 08 07 25 embodiment, a trailing edge of the upright parts 40 comprises a toothed profile 48 to assist with this. In this embodiment, a pole 50 is substantially vertically mounted to the loader arm 12 5 near to the shovel 20 and has a laser receiver / display 52 attached near to its upper end. The receiver 52 detects a laser emitted from a laser level 54 positioned on the worksite and displays to an operator whether the blade 34 of the shovel 20 needs to be raised or lowered to grade to a predetermined level. 10 Referring to Figures 1 and 4, first and second positioning rods 56a and 56b are mounted with respect to hydraulic linear actuators 58a and 58b forming part of the shovel actuator assembly 15 the positioning rods 56a and 56b are mounted in a fixed relationship to the end of the rod of each actuator 58a and 58b and slide through a bore in a respective bracket 60a and 60b at head ends of each linear actuator 58a and 58b. 15 Each bracket 60a, 60b mounts a proximity switch 62a and 62b (see also Figure 5). The proximity switches 62a and 62b change their output from a low output when the respective positioning rod 56a, 56b is not adjacent the switch and a high output when the positioning rod is adjacent the respective switch 62a / 62b as can be seen in Figure 4. 20 The end of each rod 56a / 56b mounted to the end of the actuator rod 58a, 58b is threaded and corresponding nuts 64 are provided to enable the extension of each linear actuator 58a / 58b at which the proximity switch 62a / 62b changes from low to high can be adjusted, consequently the angle of the shovel or other attachment at which each switch output 25 changes is consequently also adjusted. It can be seen that in this embodiment the length of the second positioning rod 56b is greater than that of the first positioning rod 56a and therefore the output of the corresponding switch 60b will change when the linear actuators 58a and 58b are extended 30 further, and the shovel 20 is therefore tipped further forward. Accordingly, the outputs from the first and second proximity switches 62a, 62b will change at different tilt angles of the shovel 20. Referring to Figures 5 and 6 schematic electrical and hydraulic circuits are respectively 35 shown, which illustrate the function of the positional control system incorporated within the working machine 10 of the present teachings. 08 07 25 The electrical circuit 65 of Figure 5 comprises a three-position switch 66, the first and second proximity switches 62a and 62b, a crowd divert solenoid 68 and a dump divert solenoid 70. 5 In an off position of the switch 66 the outputs from the first and second proximity switches 62a and 62b do not influence the operation of the crowd divert and dump divert solenoids 68 and 70 and the loader 10 operator is able to access the full angular range of motion for the shovel 20. 10 In a second position of the switch 66, which may be referred to as a return-to-dig (RTD) position, only the first proximity switch 62a is operative and only influences operation of a return to dig solenoid 82 connected to a loader shovel reset valve 84 (Figure 6). This return to dig function is known per se. When enabled, the operator moves a joystick 76 or other user input into a crowd / roll back position. A detent solenoid (not shown) holds 15 the shovel spool valve 78 in the crowd position until the proximity switch produces a high output and triggers the return to dig solenoid to move the loader shovel reset valve 84 to a divert to tank position and the joystick returns to its neutral position. This is utilised in an operation to load a trailer or the like by partially automating the movement of returning a tipped forward shovel, back into its level, digging position ready to scoop material and 20 be refilled. In the third position of the switch 66, which may be referred to as a return-to-grade position (RTG) both proximity switches 62a and 62b become operative and influence operation of the crowd divert solenoid 68 and dump divert solenoid 70. 25 With reference to the hydraulic circuit 75 of Figure 6, the crowd divert solenoid 68 and dump divert solenoid 70 control the position of a crowd divert spool valve 72 and dump divert spool valve 74 respectively. In this embodiment, each of these spool valves 72, 74 is a two-position, three-way valve biased into the supply position. However, when the 30 solenoid is activated, flow is diverted to tank. Both the crowd divert and dump divert valves 72 and 74 are located in a pilot hydraulic circuit (denoted by dashed lines) of the loader machine 10 between a pilot hydraulic operator input, such as the joystick or other lever 76 controlling the extension of the linear actuators 58a and 58b, and therefore the crowd / dump position of the shovel 20. 35 The pilot circuit feeds pilot pressure to a main shovel spool valve 78 provided in the main loader valve block 80 and controls the position of that spool valve. The main shovel spool valve 78 controls the flow of hydraulic fluid to the hydraulic linear actuators 58a and 58b. 08 07 25 The electrical circuit 65 is configured such that when the proximity switch 62a moves from the low to the high state, the crowd divert solenoid 68 switches the pilot flow to tank. When the proximity switch 62b goes from high to low, the dump divert solenoid 70 5 switches the pilot flow to tank. With reference to Figure 7, in use, an operator of the loader machine 10 sets the position of the first positioning rod 56a to correspond to proximity switch 62a transitioning to a high output when the shovel 20 is level, as depicted therein by adjusting the position of 10 the rod 56a using the nuts 64. With reference to Figure 8 the operator sets the position of the positioning rod 56b so that the proximity switch 62b turns transitions to a low output with the shovel in the grading position depicted in Figure 8, in which the blade 34 of the rear portion 30 is substantially 15 vertical and in contact with the ground and the front portion 38 is open with the trailing edge 45 of the base wall 42 also in contact with the ground. With these two positions set, if the operator attempts to crowd the shovel 20 past the position of Figure 7, the rod 56a switches the first switch to a high output, which in turn 20 activates the crowd divert solenoid 68 and causes the pilot pressure from the joystick 76 to divert to tank, therefore meaning that no further crowding / rolling back is possible. Similarly, if the operator seeks to tip the shovel past the position shown in Figure 8 this results in the second proximity switch 62b moving from a high to a low output, with the 25 electrical circuit of Figure 5 being configured such that this switches the dump divert solenoid 70 to a high output, which moves the dump divert spool valve to its divert to tank position resulting in pilot pressure from the joystick 76 being diverted to tank rather than flowing to the main shovel spool valve 78 and no further tipping being possible. 30 In contrast with return-to-dig, continued actuation of the joystick 76 is required to tip and crowd between the two positions. In other words, operation is "hold to run". As a result, when the switch 66 is activated into the return to grade mode, the shovel is restricted so as to move only in the range depicted between the Figure 7 and Figure 8 35 angles. This enables a relatively unskilled machine operator to adopt two key shovel positions used when levelling and grading material (and intermediate positions between) on a work site in a very simple manner. 08 07 25 This functionality is achieved with robust and low cost components of the loader machine 10, e.g., without requiring complex optical position sensors associated with the hydraulic linear actuators 58a and 58b or angular sensors associated with the shovel pivot, nor with electro-hydraulic control of the main shovel spool valve 78. Further, if combined with a 5 return-to-dig system, a number of components can have a dual use. It will be appreciated that this two-position "hard stop" functionality may be utilised to adopt further positions of a shovel 20 or other implements. For example, as depicted in Figure 9, a fine grade position of the shovel 20 may be set which is part way between the 10 positions of Figures 7 and 8 and allows for grading of material using the angled base wall 42 of the front portion 38 of the 4-in-l shovel. It will further be appreciated that the stop positions may be an overridable stop or detent, e.g. with a pushbutton or extended actuation of the joystick 76, for example. 15 Whilst described in relation to a pilot hydraulic system, a similar system may be adopted using an electro-hydraulic system 75'. This is shown in Figure 10, in which the same parts are denoted by the same reference numeral and components that are similar are denoted with a ' suffix and hydraulic lines are shown solid and electrical as dotted. 20 Use of electro-hydraulic controls may provide additional functionality. For example, by utilising a suitable controller 90, such as a microprocessor controller, the hydraulic actuation of the front portion 38 of the 4-in-l shovel 20 by a linear actuator 98 may be synchronised with movement of the shovel linear actuator 58a, 58b and optionally a lift 25 actuator 96 under the influence of solenoid operated proportional spool valves 78', 92' and 94' for the shovel, lift and 4-in-l linear actuators respectively. In a simple form, this may automatically close the clam for the level position of Figure 7 and / or open the clam for the grade position of Figure 8 30 In a more sophisticated form, the synchronisation permits motion from the grade position of Figure 8 to the closed position of Figure 7 whilst maintaining ground contact of both the blade 34 and a trailing edge 45 of the base wall 42 of the front portion 38, during crowding motion. This to automates the grabbing of loose material in front of the blade 34 at the end of a grading operation. The function may be selected by providing a further position 35 on a selector switch 66', for example and actuating the joystick 76', which in this embodiment has an electrical rather than pilot hydraulic output. 08 07 25 Referring back to Figure 1, the ability to set the extension of the hydraulic linear actuators 58a and 58b, and therefore the position of the base wall 42 of the front portion 48 and / or position of the blade 34 enables there to be a fixed vertical distance X between the laser receiver 52 and those parts of the shovel 20, despite the laser receiver being mounted to 5 the loader arm 12, and not directly to the shovel 20 itself. As a consequence, this enables the pole 50 to be mounted to the loader arm, for example, to a cross member connecting the arms 12 either side of the body where it is less susceptible to impact damage, or damage due to vibration or inertial effects. In addition, 10 in this location the display portion of the laser receiver 52 remains visible to the operator from the operator station 18 and is easily accessible for fitting and removal. The one or more embodiments are described above by way of example only and it will be appreciated that the variations are possible without departing from the scope of protection 15 afforded by the appended claims. For example the teachings may be incorporated in to manually actuated loader hydraulic systems, as well as pilot- or electro-hydraulic. In the embodiment with the laser receiver 52, this may be linked to the lift actuators 96 such that if the laser senses the shovel 20 is too low or too high, the solenoid valve 92' 20 associated with the lift actuators raises or lowers the lift arm 12 automatically under the influence of the controller 90 by a corresponding amount, without requiring operator intervention, in an open or closed loop manner. Such an arrangement may be implemented readily in the electro-hydraulic embodiment described with respect to Figure 10 and may result in more accurate levelling as the controller 90 may be able to react 25 more quickly than a human operator and may be less likely to "overshoot" with the required adjustments.

Claims

08 07 251. A working machine comprising:a body;5 a loader arm pivotably mounted to the body;an implement pivotable with respect to the loader arm;an actuator arranged to pivot the implement about a physical angular range of motion;a hydraulic system arranged to control the motion of the actuator under the10 influence of an operator input device;the hydraulic system being provided with a positional control arrangement to define first and second adjustable detent positions to selectively restrict or delineate a range of motion of the implement with respect to the loader arm to less than the physical angular range of motion in two directions; and15 wherein the implement is a 4-in-l shovel and wherein the first and secondadjustable detent positions provide a level position of the 4-in-l shovel and a grading position of the 4-in-l shovel.

2. The working machine of claim 1 wherein the first and second detents are stops20 to hydraulically limit movement in first and second opposing directionsrespectively.

3. The working machine of any preceding claim wherein the positional control arrangement is configured to be selectively disengageable and / or overridable25 by an operator.

4. The working machine of any preceding claim wherein the positional control arrangement comprises a body moveable in conjunction with pivoting of the pivotable connection and a switch or sensor associated therewith arranged to30 determine the first detent position.

5. The working machine of claim 4, wherein the body is linearly moveable.

6. The working machine of claim 4 or claim 5 wherein the body is a bar, plate or35 rod having a predetermined position sensed by the switch or sensor.

7. The working machine of claim 6 wherein the switch is a proximity switch.

8. The working machine of any one of claims 4 to 7, wherein the relative physical positions of the body and the switch or sensor are adjustable so as to alter at least one of the detent positions.5 9. The working machine of any of claims 4 to 8 comprising a second bodymoveable in conjunction with pivoting of the pivotable connection and a second switch or sensor associated therewith arranged to determine the second detent position.10 10. The working machine of any preceding claim, wherein the hydraulic systemcomprises a spool valve controlling fluid flow to the actuator and wherein upon achieving the first or second detent positions, flow through the spool valve isadjusted.15 11. The working machine of claim 10, wherein the hydraulic system comprises apilot line control and the positional control arrangement alters pilot pressure in the pilot line to the spool valve to adjust the flow.08 07 2512. The working machine of claim 11, wherein the altering of pilot pressurecomprises relieving pressure in the pilot line.

13. A working machine of any of claims 1 to 8 comprising a controller and an electro-hydraulic spool valve.25 14. The working machine of claim 13 wherein a sensor signals the controller andthe controller signals the electro-hydraulic spool valve when one of the first and second detent positions is reached.

15. The working machine of claim 13 or claim 14 wherein the controller signals 30 operation of a further hydraulic service.

16. The working machine of claim 15, wherein the controller signals pivoting of a clam shell portion of the 4-in-l shovel simultaneously with movement of the of the actuator between the first and second detent positions.3517. A method of operating a working machine according to any preceding claim comprising the steps of setting the first and second detent positions and operating the shovel between these positions.

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