Method and system for operating dump truck

Abstract

A system for operating a dump truck and a method of operating a dump truck including a dump truck body pivotably movable relative to a frame with a hydraulic cylinder disposed between the frame and the dump truck body and actuatable to pivot the dump truck body. Load parameters relating to the load borne by the hydraulic cylinder are monitored during the tipping. It is determined whether the hydraulic cylinder is at risk of buckling based at least on the load parameter, and if it is determined that the hydraulic cylinder is at risk of buckling, an output is generated in response.

Description

[0001] This application is a divisional application of the patent application with application number 201710795059.8, filed on September 6, 2017, and titled "Method and system for operating a dump truck". TECHNICAL FIELD

[0002] The present invention relates to a method and system for operating a dump truck. In particular, the present invention relates to a method and system for determining whether a hydraulic cylinder of a dump truck is at risk of buckling. BACKGROUND

[0003] A dump truck (sometimes referred to as a dumper or a tipper) is a vehicle generally used in the construction industry for transporting aggregate, such as gravel or sand. A dump truck generally comprises an engine, a cab and a trailer. The trailer typically has a trailer chassis or frame with a dump body pivotally mounted thereto in the form of an open top cuboid container. A hydraulic cylinder is arranged between the frame and the dump body and is capable of extending to pivot the dump body to a tipped over position in which the load is emptied from the body. The cylinder is capable of retracting to lower the dump body. It will be appreciated that this is just one form of dump truck and that other types exist.

[0004] If, during a tipping operation, the axial load taken by the hydraulic cylinder is too great, the hydraulic cylinder can buckle. This is obviously undesirable as it irreparably damages the hydraulic cylinder and can cause serious safety hazards. To prevent buckling of the hydraulic cylinder, it is known to limit the working pressure of the cylinder to ensure that it never lifts more than its own column strength (plus a safety factor). This sometimes results in the hydraulic cylinder being "oversized" for a particular application in order to ensure that it can lift the required load whilst ensuring that it will not buckle. However, selecting an oversized cylinder often means that the tipping cycle is too slow, the cylinder is too heavy and a large oil tank is required.

[0005] It is therefore desirable to provide an improved arrangement. SUMMARY

[0006] According to an aspect there is provided a method of operating a dump truck, the dump truck comprising a dump truck body pivotably movable relative to a frame, wherein a hydraulic cylinder is arranged between the frame and the dump truck body and is actuatable to pivot the dump truck body, the method comprising: commencing a tipping operation in which the dump truck body is pivoted towards a tipped position; and during at least a phase of the tipping operation: (i) monitoring a load parameter relating to a load experienced by the hydraulic cylinder; (ii) determining that the hydraulic cylinder is at risk of buckling based at least on the load parameter; and (iii) generating an output in response to determining that the hydraulic cylinder is at risk of buckling. The output can be any of a number of suitable outputs such as an audible or visual alarm, or the tipping operation can be stopped, terminated or prevented. This can prevent the hydraulic cylinder from buckling during the tipping operation, thereby providing a significant safety advantage.

[0007] The "load parameter" can be any suitable parameter relating to a load experienced by the hydraulic cylinder. The load parameter can be an axial load parameter relating to an axial load experienced by the hydraulic cylinder.

[0008] The axial load parameter can be a pressure parameter relating to a hydraulic pressure within the hydraulic cylinder. The pressure parameter can be generated by a pressure sensor that measures the hydraulic pressure within the hydraulic cylinder. The pressure sensor can be mounted to the hydraulic cylinder.

[0009] In other arrangements, the load parameter can be generated by one or more load cells. For example, the load cell(s) can be mounted on trunnions that mount the hydraulic cylinder to the frame and / or the dump truck body, or they can be attached to a bracket to which the hydraulic cylinder is attached. In another arrangement, one or more strain gauges can be used to generate a load parameter relating to a load experienced by the hydraulic cylinder. In yet another arrangement, a bend sensor can be used to monitor and / or measure a bend of the hydraulic cylinder, and a bend parameter relating to a load experienced by the cylinder can be monitored. The bend sensor can be, for example, a strain gauge. Of course, it will be appreciated that other suitable sensors or parameters can be utilised and / or monitored.

[0010] The hydraulic cylinder can be determined to be at risk of buckling at least when the load parameter exceeds a buckling threshold. The buckling threshold can be a threshold load parameter and can relate to a threshold load experienced by the hydraulic cylinder, such as an axial load. The buckling threshold can be a predetermined buckling threshold. In other words, the buckling threshold can be preset for a particular installation (e.g. it can be preset for a particular hydraulic cylinder). In other arrangements, the buckling threshold can vary, for example, it can depend on a length of the hydraulic cylinder. The buckling threshold can decrease as the length of the hydraulic cylinder increases.

[0011] The method can further comprise determining that the length of the hydraulic cylinder is above a threshold length. The determination that the hydraulic cylinder is at risk of buckling can be based at least on (a) the determination that the length of the hydraulic cylinder is above a threshold length and (b) a load parameter. In one arrangement, the load parameter is not actively monitored until it has been determined that the length of the hydraulic cylinder is above a threshold length, and once it has been determined that the length of the hydraulic cylinder is above a threshold, the load parameter is monitored to check whether the cylinder is at risk of buckling (e.g. whether the load parameter exceeds a threshold).

[0012] The hydraulic cylinder can be a multi-stage hydraulic cylinder (e.g. a telescopic hydraulic cylinder). The determination that the length of the hydraulic cylinder is above a threshold length can be made when it is determined that the hydraulic cylinder is in a final stage of extension. Thus, the actual length can not be determined. Instead, it can simply be determined that the final stage of the cylinder is in extension. This can be done using any suitable method. For example, this can be determined using a Hall effect sensor, or the pressure within the hydraulic cylinder can be monitored, and it can be determined that the cylinder is in a final stage of extension when a last pressure step change occurs.

[0013] The method can further comprise monitoring a length parameter relating to the length of the hydraulic cylinder. The determination that the length of the hydraulic cylinder is above a threshold length can be based at least on the length parameter. The length parameter can be generated by a tilt sensor. The tilt sensor can measure the tilt of the dump truck body. The tilt of the dump truck body will have a fixed relationship to the length of the cylinder and thus can be related to the length of the hydraulic cylinder. The length of the hydraulic cylinder can thus be derived from the tilt of the dump truck body. The tilt sensor can be mounted to the dump truck body. The tilt sensor can measure the tilt of the hydraulic cylinder. The tilt sensor can be mounted to the hydraulic cylinder. Again, the length of the cylinder can be derived from the tilt of the hydraulic cylinder. Other sensors can be used to generate the length parameter and / or determine the length of the hydraulic cylinder. For example, the length parameter can be generated by a rotational position sensor arranged to measure the angular position of the dump truck body about a pivot axis of the dump truck body and / or the angular position of the hydraulic cylinder about a pivot axis of the hydraulic cylinder. Due to fixed geometrical dimensions, the length of the hydraulic cylinder can be derived from the angular position of the hydraulic cylinder or the angular position of the dump truck body. The tilt can be measured relative to the ground or relative to the vehicle. In one arrangement, the tilt can be measured relative to the ground and corrected for any tilt of the vehicle itself.

[0014] Generating the output can include generating an alert in response to determining that the hydraulic cylinder is at risk of buckling. The alert can include a visual and / or audible alert. The method can further include preventing the roll-off operation from being performed (or preventing further elongation of the hydraulic cylinder) in response to determining that the hydraulic cylinder is at risk of buckling. The method can further include automatically terminating (i.e., stopping) the roll-off operation in response to determining that the hydraulic cylinder is at risk of buckling. The method can further include automatically lowering the dump body (e.g., lowering it or returning it to a stowed position) in response to determining that the hydraulic cylinder is at risk of buckling.

[0015] It will be appreciated that the order of the method steps presented herein is not limited and they can be performed in any suitable order.

[0016] According to another aspect there is provided a system for a dump truck, the dump truck comprising a dump truck body movable pivotably relative to a frame, wherein a hydraulic cylinder is arranged between the frame and the dump truck body and is actuatable to pivot the dump truck body, the system comprising: a hydraulic cylinder load monitoring module arranged to monitor a load parameter relating to a load borne by the hydraulic cylinder during a roll-off operation; a buckling risk determination module arranged to: determine whether the hydraulic cylinder is at risk of buckling based on at least the load parameter; and generate an output in the event that the hydraulic cylinder is determined to be at risk of buckling.

[0017] The load parameter can be an axial load parameter relating to an axial load borne by the hydraulic cylinder. The axial load parameter can be a pressure parameter relating to a hydraulic pressure within the hydraulic cylinder. The system can further comprise a pressure sensor arranged to measure the hydraulic pressure within the hydraulic cylinder and arranged to generate the pressure parameter. The pressure sensor can be arranged to be mounted to the hydraulic cylinder.

[0018] The buckling risk determination module can be arranged to determine that the hydraulic cylinder is at risk of buckling at least when the load parameter exceeds a buckling threshold. The buckling threshold can be a predetermined buckling threshold.

[0019] The system can further comprise a cylinder length determination module arranged to determine whether a length of the hydraulic cylinder is above a threshold length; and wherein the buckling risk determination module is arranged to determine that the hydraulic cylinder is at risk of buckling when (a) it is determined that the length of the hydraulic cylinder is above the threshold length and (b) based on at least the load parameter.

[0020] The hydraulic cylinder can be a multi-stage hydraulic cylinder. The cylinder length determining module can be configured to determine that the length of the hydraulic cylinder is above a threshold length when it is determined that the hydraulic cylinder is in an elongated final stage. The cylinder length determining module can be configured to monitor a length parameter related to the length of the hydraulic cylinder and can be configured to determine whether the length of the hydraulic cylinder is above the threshold length based on at least the tilt parameter. The system can further comprise a tilt sensor configured to generate the length parameter. The tilt sensor can be configured to measure a tilt of the dump truck body. The tilt sensor can be mounted to the dump truck body. The tilt sensor can be configured to measure a tilt of the hydraulic cylinder. The tilt sensor can be configured to be mounted to the hydraulic cylinder.

[0021] The system can further comprise an alert generator configured to generate an alert if it is determined that the hydraulic cylinder is at risk of buckling. The alert generator comprises a visual and / or audible alert generator. The alert can be cancelled if the buckling determining module determines that there is no longer a risk of buckling.

[0022] The system can further comprise a cylinder control module configured to prevent a roll-over operation from being performed if it is determined that the hydraulic cylinder is at risk of buckling. The system can further comprise a cylinder control module configured to automatically terminate a roll-over operation in response to determining that the hydraulic cylinder is at risk of buckling. The system can further comprise a cylinder control module configured to automatically lower the dump truck body in response to determining that the hydraulic cylinder is at risk of buckling.

[0023] The invention also relates to a dump truck comprising: a dump truck body movable pivotably relative to a frame; a hydraulic cylinder arranged between the frame and the dump truck body and actuatable to pivot the dump truck body; and a system according to any of the statements herein. The pressure sensor can be mounted to the hydraulic cylinder. The tilt sensor can be mounted to the dump truck body. The tilt sensor can be mounted to the hydraulic cylinder. Also configured is a dump vehicle according to any of the statements herein.

[0024] The invention can comprise any combination of the features and / or limitations referred to herein, unless the combination of features is mutually exclusive. BRIEF DESCRIPTION OF DRAWINGS

[0025] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0026] Figure 1 schematically illustrating a dump truck;

[0027] Figure 2 schematically illustrating Figure 1 a side view of a dump truck without a tractor;

[0028] Figure 3 schematically illustrating a buckling warning system;

[0029] Figure 4 A graph is shown schematically showing pressure as a function of cylinder tilt angle; and Figure 5 and 6 An alternative dump truck is shown. DETAILED DESCRIPTION

[0030] Figure 1 and 2 A dump truck 1, sometimes referred to as a tipper truck, is shown comprising a tractor 2 and a trailer 4. The trailer 4 has a trailer chassis or frame 6 and a dump body 8 is pivotally mounted to the trailer chassis or frame. The dump body 8 is pivotally mounted to the chassis 6 about a transverse axis 10 located at the rear of the chassis 6. The dump body 8 is in the form of a cuboid container having an open top. A rear panel (or door) 12 of the dump body 8 is hinged at its upper edge and can be locked and unlocked so that it can be opened to allow the contents of the dump body 8 to be emptied. A multi-stage telescoping hydraulic cylinder 14 is arranged to be pivotally attached at a lower end to the front of the chassis 6 and at an upper end to the front of the dump body 8. The hydraulic cylinder 14 can be extended (as shown) to pivot the dump body 8 about the axis 10 to a fully tilted position in which, with the rear panel 12 unlocked, any load within the dump body 8 is emptied onto the ground. The cylinder 14 can be retracted to pivot the dump body 8 back to a resting position in which it rests on the chassis 6. Figure 1

[0031] The dump truck 1 also includes a hydraulic actuation system 20 for actuating the hydraulic cylinder 14. The hydraulic actuation system 20 includes a tank 22, a pump 24 and a valve assembly 26 which are connected with fluid lines to form a fluid circuit. A pilot system (not shown) is also arranged to switch the valve assembly 26 between various configurations. The valve assembly 26 is configured with ports which are hydraulically connected to the hydraulic cylinder 14 with fluid lines 28. The valve assembly 26 can be switched between a number of configurations in order to operate the hydraulic cylinder 14. In a bypass configuration of the valve assembly 26, with the pump 24 running, hydraulic fluid is circulated by the pump 24 from the tank 22 through the valve assembly 26 back to the tank 22. To extend the hydraulic cylinder 14 to pivot the dump body 8 to the fully tilted position (as shown), the valve assembly 26 is switched to a cylinder extension configuration in which hydraulic fluid is circulated by the pump 24 from the tank 22 through the valve assembly 26 to the hydraulic cylinder 14. To retract the hydraulic cylinder 14 to pivot the dump body 8 back to the resting position, the valve assembly 26 is switched to a cylinder retraction configuration in which hydraulic fluid is circulated by the pump 24 from the tank 22 through the valve assembly 26 to the hydraulic cylinder 14. Figure 1 and 2 ​When the self-dumping truck 1 is to be dumped, the valve assembly 26 is switched to a lift configuration in which the pump 24 pumps hydraulic fluid from the tank 22 into the hydraulic cylinder 14, causing it to extend. When the hydraulic cylinder 14 has extended sufficiently (fully or by a desired amount), the valve assembly 26 returns to a bypass configuration in which hydraulic fluid is circulated from the tank 22 through the valve assembly 26 back to the tank 22 with the pump 24 running. In the bypass configuration of the valve assembly 26, the fluid line 28 is closed and thus the cylinder 14 is maintained in the extended configuration. In this embodiment, the hydraulic actuation system 20 is configured with an automatic knock-off that automatically switches the valve assembly 26 to the bypass configuration when the hydraulic cylinder has fully extended. The automatic knock-off is in the form of a switch that is triggered by the cylinder of the hydraulic cylinder 14 when it reaches the fully extended position. The valve assembly 26 can also be configured with a pressure relief bypass valve. If the pressure of the hydraulic fluid in the valve assembly 26 has reached a threshold value (possibly due to an overloading in the self-dumping truck body 8), the hydraulic fluid is diverted to the tank 22 rather than pumped into the hydraulic cylinder 14. This is a safety feature that can be configured to prevent lifting of an overloading. To lower the hydraulic cylinder 14, the pump 24 is shut down and the valve assembly 26 is switched to a lower configuration. In this configuration, the fluid line 28 is open and the cylinder 14 retracts under the weight of the self-dumping truck body 8 with hydraulic fluid returning to the tank 22.

[0032] If the load within the self-dumping truck body 8 is too large and / or the hydraulic cylinder 14 is too small, there can be a risk of the hydraulic cylinder 14 buckling (i.e. exceeding the critical column strength) during a dump operation. As will be described in more detail below, the self-dumping truck 1 is configured with a buckling warning system 40 that generates an alarm if the hydraulic cylinder 14 is at risk of buckling.

[0033] Figure 3A jackknife warning system 40 is shown for generating a warning that the hydraulic cylinder 14 is at risk of jackknifing. The jackknife warning system 40 includes a pressure sensor 42 for measuring the pressure of the hydraulic fluid, such as oil, within the hydraulic cylinder 14, and a tilt (or roll) sensor 44 for measuring the tilt of the dump truck body 8 about the pivot axis 10, i.e. the tilt angle. The pressure sensor 42 is an electronic pressure transducer mounted within a port configured in the outer wall of the cylinder body 14. The pressure sensor 42 is thereby fixed to the hydraulic cylinder 14 and exposed to the hydraulic fluid within the cylinder body 14. The pressure sensor 42 is arranged to generate an electronic signal representative of the detected hydraulic pressure, i.e. the pressure of the hydraulic fluid. The hydraulic pressure within the cylinder body 14 can therefore be determined from the electronic signal generated by the pressure sensor 42. The pressure within the hydraulic cylinder 14 is also related to the axial load experienced by the hydraulic cylinder 14. The electronic signal generated by the pressure sensor can therefore be considered to be a load parameter related to the load experienced by the hydraulic cylinder 14. The tilt sensor 44 is mounted to the dump truck body 8 and positioned such that it can measure the tilt of the dump truck body 8 about the pivot axis 10. In the case where the truck chassis 6 is level, the tilt angle Θ of the dump truck body 8 can be determined from the electronic signal generated by the tilt sensor 44. Due to the relationship between the hydraulic cylinder 14 and the dump truck body 8, the electronic signal generated by the tilt sensor 44 is also related to the tilt angle a of the hydraulic cylinder 14 and the length L of the hydraulic cylinder 14, i.e. in the case where the truck chassis 6 is level, the tilt angle a and the length L of the cylinder body can be determined from the electronic signal generated by the tilt sensor 44. The signal generated by the tilt sensor 44 can therefore be considered to be a length parameter as it can be related to the length of the cylinder body 14.

[0034] The jackknife warning system 40 also includes a hydraulic cylinder load determination module 52, a cylinder length determination module 54, a jackknife risk determination module 56, a cylinder control module 58 and a display 60. The pressure sensor 42 is connected by a suitable cable to the hydraulic cylinder load determination module 52, and the tilt sensor 44 is connected by a suitable cable to the cylinder length determination module 54, such that the modules 52, 54 can receive the electronic signals generated by the sensors 42, 44. In particular, the hydraulic cylinder monitoring module 52 is arranged to receive from the pressure sensor 42 a load parameter related to the load experienced by the hydraulic cylinder 14, and the cylinder length determination module 54 is arranged to receive from the tilt sensor 44 a length parameter related to the length of the hydraulic cylinder 14. It will be appreciated that in other embodiments the sensors 42, 44 can be connected wirelessly to the respective modules 52, 54.

[0035] The bend determination module 56 is connected to the hydraulic cylinder load monitoring module 52 and receives the pressure signal (or load parameter) relating to the axial load being taken by the hydraulic cylinder 14. The cylinder length determination module 54 is configured to determine whether the multi-stage telescopic hydraulic cylinder 14 is in the extended final stage based on the signal generated by the tilt sensor 44. This can be achieved by setting a threshold tilt value relating to a threshold length of the hydraulic cylinder, which is the length of the cylinder before it enters the extended final stage. The cylinder length determination module 54 is configured to determine that the cylinder is above the threshold length (and in the extended final stage) when the length parameter (i.e. the output of the tilt sensor 44) exceeds the threshold tilt value. The bend determination module 56 is connected to the cylinder length determination module 54 and receives a signal from the cylinder length determination module 54 when it is determined that the cylinder 14 is in the extended final stage. It will be appreciated that the cylinder can be determined to be above the threshold length and / or in the extended final stage by monitoring other parameters. For example, a Hall effect sensor can be used to determine when the cylinder has reached a particular length. In another arrangement, the pressure within the hydraulic cylinder 14 can be monitored and the cylinder can be determined to be in the extended final stage when a last step change in pressure occurs. Figure 4 A graph showing the hydraulic pressure P within a four-stage telescopic hydraulic cylinder as the tilt angle a increases (where a = 0 when the dump truck body 8 is in the stowed position) is shown. As shown, there is a step increase in pressure corresponding to the next stage of extension. Thus, for a four-stage hydraulic cylinder, the cylinder can be determined to have entered the extended final stage when the third step change in pressure occurs. This can correspond to the threshold length LT. Figure 4

[0036] The bend determination module 56 is configured such that when the cylinder is in the extended final stage (i.e. when it is above the threshold length), it is configured to determine whether the hydraulic cylinder 14 is at risk of buckling. The bend determination module 56 is configured to determine that the hydraulic cylinder 14 is at risk of buckling if the value of the pressure signal monitored (i.e. the value of the load parameter) exceeds a pre-set buckling threshold. The buckling threshold is defined based on the critical load of the hydraulic cylinder (using Euler's column formula) plus a safety factor. If the buckling threshold is exceeded, this indicates that the hydraulic cylinder is at risk of buckling. In this arrangement, the buckling threshold is fixed for a particular set-up. However, in other arrangements, the buckling threshold can be calculated based on the current length of the hydraulic cylinder.

[0037] ​The cylinder control module 58 is coupled to the hydraulic actuation system 20 of the dump truck 1 (via a pilot system) to enable it to automatically terminate the tilting operation and actuate the hydraulic cylinders 14 to return the dump body 8 to the stowed position in the event that the flex determination module 56 determines that the hydraulic cylinders 14 are at risk of flexing. A display 60 is connected to the flex determination module 56 and is configured to display an alert in the event that the flex determination module 56 determines that the hydraulic cylinders 14 are at risk of flexing. The display 60 is an LCD screen configured to display a visual alert, and a generator is also configured to produce an audible alert. In this embodiment, the display 60 is mounted in the dashboard of the tractor 2 so that it is easily visible to the operator. However, in other embodiments, the display can be located externally, or it can be in the form of a wireless handheld device such as a smartphone or tablet. If the display 60 is provided by a portable wireless device such as a smartphone or tablet, it can also incorporate the various modules 52, 54, 56, 58 and can communicate wirelessly with the sensors 42, 44. It will be appreciated that other displays such as one or more LEDs can be used to provide an alert.

[0038] The operation of the dump truck 1 will now be described.

[0039] Before commencing a tilting operation, the dump truck 1 is brought to a site where the chassis 6 is substantially level. Initially, the dump body 8 containing the load 16, such as sand, is in the stowed position. In the stowed position of the dump body 8, it is stowed on the chassis 6 of the trailer 4 so that the load is transmitted directly to the chassis 6. Thus, in the stowed position, no load is transmitted through the hydraulic cylinders 14. To commence a tilting operation to empty the load 16 within the dump body 8, the operator uses a control lever (not shown) of the hydraulic actuation system 20 to extend the multi-stage telescopic hydraulic cylinders 14. This causes the dump body 8 to pivot about the axis 10 from the stowed position towards the fully tilted position. The hydraulic cylinders 14 are extended so as to pivot the dump body 8 to the fully tilted position, and the stages of the cylinder are extended one after the other in sequence.

[0040] Referring to Figure 4 As soon as the dump body 8 is pivoted away from the chassis 6, the load is transmitted through the hydraulic cylinders 14 which pressurise the hydraulic fluid within the cylinders 14. As the angle of inclination a of the cylinder increases (i.e. as the dump body 8 is pivoted away from the chassis), the pressure exerted by the cylinder gradually decreases as the axial load on the cylinder decreases. However, the pressure within the hydraulic cylinders 14 exhibits a step change increase corresponding to the commencement of extension of the next stage of the hydraulic cylinders 14.

[0041] The hydraulic cylinder load monitoring module 52 continuously monitors the value of the pressure signal generated by the pressure sensor 42, and the cylinder length determination module 54 continuously monitors the value of the tilt signal generated by the tilt sensor 44. The tilt sensor 44 monitors the angle of tilt of the dump truck body 8, but due to the relationship between the cylinder 14 and the dump truck body 8, it is also related to the length L of the hydraulic cylinder 14. The cylinder length determination module 54 determines whether the hydraulic cylinder 14 is in the final stage of elongation by determining whether the value of the tilt signal exceeds a threshold value. The threshold value corresponds to the value of the tilt signal when the final stage of the cylinder 14 begins to elongate. When the cylinder length determination module 52 has determined that the hydraulic cylinder 14 has entered the final stage of elongation, the buckling risk determination module 56 determines whether the load (which can be an axial load) being experienced by the hydraulic cylinder 14, as indicated by the pressure signal, indicates that the hydraulic cylinder 14 is at risk of buckling. In this embodiment, this is done by comparing the value of the pressure signal generated by the pressure sensor 42 to a predetermined buckling threshold. As explained above, the buckling threshold is based on the pressure within the cylinder corresponding to the critical load plus a safety factor.

[0042] If it is determined that the current hydraulic cylinder is at risk of buckling, the display 60 generates a visual alert, and an audible alert is also generated. This alerts the operator to the potential risk of cylinder buckling. Furthermore, in this arrangement, in response to determining that the hydraulic cylinder is at risk of buckling, the cylinder control module 58 communicates with the hydraulic actuation system 20 to automatically actuate the hydraulic cylinder 14 to terminate the tilting operation, prevent any further tilting, and return the dump truck body 8 to the resting position. Returning the dump truck body 8 to the resting position minimises any risk of the cylinder 14 buckling. As soon as it is determined that the risk of buckling no longer exists, any alerts are cancelled and tilting is again permitted.

[0043] Providing the buckling alert system 40 allows smaller, lighter hydraulic cylinders to be used for a particular working pressure, while still minimising the risk of cylinder buckling. This can also result in a reduction in the length of the tilting cycle.

[0044] It has been described above that if the buckling risk determination module 56 determines that the cylinder 14 is at risk of buckling, the tilting operation is stopped (i.e. movement of the dump truck body 8 is terminated), the dump truck body 8 is returned to the resting position, and an alert is generated. However, in other embodiments, only the alert is generated. Alternatively, in another embodiment, movement of the dump truck body 8 can be stopped, and the operator can need to manually lower the dump truck body.

[0045] In the embodiment described above, the pressure sensor 42 that measures the hydraulic pressure within the cylinder 14 is used as a load parameter related to the axial load borne by the hydraulic cylinder 14. However, other sensors (such as load cells or strain gauges) attached to appropriate components of the dump truck can be used to generate a load parameter related to the load borne by the hydraulic cylinder 14. In addition, if a pressure sensor is used, this pressure sensor can be installed at any appropriate location in the hydraulic circuit to measure the pressure within the cylinder.

[0046] The tilt sensor 44 has been described as generating a signal indicative of the length of the hydraulic cylinder 14 and as being able to be related to the cylinder length L. However, other suitable sensors and / or methods may be used to determine whether the cylinder length is above a threshold. Furthermore, in certain embodiments, the cylinder length may not be monitored or calculated, and a load parameter related to the load passing through the hydraulic cylinder 14 may be continuously monitored to determine whether a risk of buckling exists.

[0047] The system and method can be used with any suitable single stage or multi-stage (telescopic) hydraulic cylinder.However, it will be appreciated that the buckling threshold may be different for each cylinder depending on, among other things, the slenderness ratio of the hydraulic cylinder.

[0048] It will be appreciated that the system may be used with any suitable type of dump truck in which the dump truck body 8 is capable of being pivoted or moved by hydraulic cylinders. Figure 5 and 6 As shown, a dump truck 1 can include a tractor 2 having a frame 6, with a hydraulic cylinder 14 connected between the frame 6 and a dump truck body 8. The dump truck 1 also includes a drawbar 9 that is pivotally connected to the frame 6 at a first pivot axis 10 at a first end and to the dump truck body 8 at a second end at a second pivot axis. To pivot the dump truck body 8 from a rest position (not shown) to a fully tilted position, the hydraulic cylinder 14 is extended, which causes the dump truck body 8 to pivot clockwise relative to the frame 6 and the drawbar 9. It should also be appreciated that to monitor the length of the hydraulic cylinder 14, the tilt angle of the drawbar 9 can be measured, as there is a fixed relationship between this angle and the length of the hydraulic cylinder 14.

[0049] The buckling warning system 40 can be one of a plurality of intelligent systems provided with the dump truck 1 and can therefore be used in combination with any suitable system to provide information related to the dump truck and / or the load carried by the dump truck body. If multiple intelligent systems are provided, they can, for example, share the same display or processor.

[0050] Certain aspects of the apparatus, systems and methods described hereinabove can be implemented as instructions (such as processor control code) stored on a non-transitory carrier medium, such as a magnetic disk, a CD-ROM, a DVD-ROM, a programmed memory such as a read-only memory, a firmware, or a data carrier such as a visual signal or an electrical signal carrier. For certain applications, embodiments of the present application will be implemented on a DSP (digital signal processor), an ASIC (application specific integrated circuit) or a FPGA (field programmable gate array). Accordingly, the code can comprise conventional program code or microcode or code for setting up or controlling an ASIC or FPGA. The code can also comprise code for dynamically configuring reconfigurable apparatus, such as reprogrammable logic gate arrays. Similarly, the code can comprise code for a hardware description language such as Verilog (trademark of TM Cadence Design, Inc.) or VHDL (very high speed integrated circuit hardware description language). The code can be distributed as object code upon a storage medium or via a suitable type of carrier wave. Those skilled in the relevant arts will appreciate that the embodiments of the present application can be practiced with other computer system configurations, including single-processor or multiprocessor computer systems, minicomputers, mainframe computers, as well as personal computers, hand-held computing devices, microprocessor-based or programmable consumer electronics, network PCs, and the like. The embodiments of the present application can also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules can be located in both local and remote memory storage devices.

Claims

1. A method of operating a dump truck, the dump truck comprising a dump truck body pivotally movable relative to a frame, wherein a multi-stage hydraulic cylinder is disposed between the dump truck body and the frame and is actuatable to pivot the dump truck body, the method comprising: initiating a tipping operation in which the dump truck body is pivoted toward a tipping position by pumping hydraulic fluid into a multi-stage hydraulic cylinder; and during tipping operations: (i) monitoring the pressure of the hydraulic fluid in the multi-stage hydraulic cylinder; (ii) determining that the multi-stage hydraulic cylinder is in the final stage of extension by detecting a step increase in pressure corresponding to the beginning of extension of the final stage of the multi-stage hydraulic cylinder; (iii) after determining that the multi-stage hydraulic cylinder is in the final stage of extension, determining that the multi-stage hydraulic cylinder is at risk of buckling by comparing the monitored pressure with a predetermined buckling threshold; and (iv) generating an output in response to determining that the multi-stage hydraulic cylinder is at risk of buckling.

2. The method of claim 1, wherein generating an output comprises generating a visual and / or audible alarm.

3. The method of claim 1 or 2, wherein generating an output comprises automatically stopping the tipping operation.

4. The method of claim 1 or 2, wherein generating an output comprises automatically lowering a dump truck body.

5. A system for a dump truck comprising a dump truck body pivotally movable relative to a frame, wherein: The multi-stage hydraulic cylinder is arranged between the dump truck body and the frame. The system includes: a pressure sensor configured to monitor hydraulic pressure within the multi-stage hydraulic cylinder; and a control module operatively connected to the pressure sensor, the control module configured to: (i) determining that the multi-stage hydraulic cylinder is in the final stage of extension by detecting a pressure step increase in the monitored pressure, the pressure step increase corresponding to the beginning of extension of the final stage of the multi-stage hydraulic cylinder; (ii) after determining that the multi-stage hydraulic cylinder is in a final stage of extension, determining that the multi-stage hydraulic cylinder is at risk of buckling by comparing the monitored pressure with a predetermined buckling threshold; and (iii) generating an output in response to determining that the multi-stage hydraulic cylinder is at risk of buckling.

6. A system according to claim 5, further comprising an alarm generator arranged to generate a visual and / or audible alarm as output.

7. The system of claim 5 or 6, wherein the control module is further configured to automatically stop the tipping operation as an output.

8. A dump truck comprising: a dump truck body pivotally movable relative to the frame; a multi-stage hydraulic cylinder disposed between the frame and the dump truck body and actuatable to pivot the dump truck body; And a system according to any one of claims 5 to 7.

9. A dump vehicle comprising the dump vehicle according to claim 8.

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