AU2017202395A1 - Height Limiter - Google Patents

Abstract

A height limiter for a machine having a boom (20) with an attachment (32) mounted to the end of the boom (22), the height limiter including an operator input device for enabling an operator to select an attachment that is attached to the boom, a plurality of sensors, at least one sensor associated with the boom and at least one sensor associated with the attachment, a height determination means for receiving data from the plurality of sensors and for determining a height of the boom and a height of the attachment from the data, and control means for preventing further raising of the boom or attachment if the boom or attachment is at a height that is at a maximum height. The height limiter can have an operator input module that only allows the operator of the machine to input the type of attachment that is attached to the boom. a* 4t5

Description

HEIGHT LIMITER TECHNICAL FIELD

[0001] The present invention relates to a height limiter for use on excavators, loaders and other earthmoving equipment.

BACKGROUND ART

[0002] A number of different pieces of earthmoving equipment include a boom or an arm that can be raised or lowered. For example, a front end loader has one arm and an excavator has two arms located at the front of the machine. The arms can be raised and lowered about respective pivot points. Hydraulic mechanisms are typically used to raise and lower the arms.

The arms also normally carry a bucket at their far ends, with that bucket being able to be pivoted around pivot points where it is attached to the arms. Again, appropriate linkages and hydraulic mechanisms are used to control the movement of the bucket. In some excavators, the bucket can be replaced by other attachments.

[0003] Excavators typically have a boom that comprises two or more arms pivotally connected to each other. The end of the most distal arm carries an attachment, which can be a bucket, a grabber, a hammer, a hook, and auger or a tamper. Appropriate hydraulic systems control the arms and the attachment during use of the excavator.

[0004] There are a number of environments of use for earthmoving equipment where it is essential that the arm or arms, associated linkages and attachment do not move above a predetermined maximum safe working height. For example, if the equipment is being used in a mine, the arm(s), linkages or attachment should not be raised to a level where they come into contact with the roof of the mine, as that can cause damage to the roof of the mine. Similarly, if the equipment is being used underneath overhead power lines (such as if the equipment is being used on a railway line having overhead power lines), safe operation of the equipment dictates that the arm(s), linkages or attachment be maintained at a safe distance away from the power lines in order to avoid electrocution risk.

[0005] There are a number of height limiters that are available for purchase. The simplest of these comprise a single angle sensor mounted on the boom. The angle sensor enables a controller to calculate the height of the boom. When the height of the boom reaches a maximum height programmed into the controller, further lifting of the boom above that height is not possible. The controller typically operates to control the hydraulics that drive the boom so that the hydraulics operate to stop further lifting of the boom when the height limit is reached. In this regard, a hydraulic solenoid valve may be included in the hydraulic circuit to provide hydraulic motion cut on the hydraulic lift circuit when the height limit is reached.

[0006] More advanced height limiters include sensors installed on each of the moving parts of the boom and attachment to enable determination of the height of the highest point of the boom and attachment. Again, if the height of the highest point of the boom and attachment hits the maximum height limit, further raising of the boom or attachment is prevented.

[0007] Many existing height limiters that include a number of sensors have a control module that enables the operator of the equipment to input various variables into the controller, such as the maximum height limit and the type of attachment. Many of these systems include touchscreens that provide a variety of screens or menu options to enable the operator to enter the required information or data. Unfortunately, in use, it has been found that operator compliance with all of the requirements for such complex data entry in the controller is poor, which can lead to unsafe operation.

[0008] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

SUMMARY OF INVENTION

[0009] The present invention is directed to a height limiter, which may at least partially overcome at least one of the abovementioned disadvantages or provide the consumer with a useful or commercial choice.

[0010] With the foregoing in view, the present invention in one form, resides broadly in a height limiter for a machine having a boom with an attachment mounted to the end of the boom, the height limiter including an operator input device for enabling an operator to select an attachment that is attached to the boom, a plurality of sensors, at least one sensor associated with the boom and at least one sensor associated with the attachment, a height determination means for receiving data from the plurality of sensors and for determining a height of the boom and a height of the attachment from the data, and control means for preventing further raising of the boom or attachment if the boom or attachment is at a height that is at a maximum height.

[0011] In one embodiment, the at least one sensor associated with the boom comprises at least one sensor attached to the boom. In one embodiment, the at least one sensor associated with the attachment comprises at least one sensor attached to the attachment.

[0012] In one embodiment, the plurality of sensors includes a sensor for determining an angle of an arm of the boom and a sensor for determining an angle of the attachment that is attached to the boom.

[0013] In another embodiment, the plurality of sensors includes a sensor for determining an angle of a first arm of the boom that is attached to the machine, a sensor for determining an angle of a second arm of the boom that is attached to the first arm, and a sensor for determining an angle of the attachment, the attachment being attached to the second arm of the boom.

[0014] In a further embodiment, the plurality of sensors further includes a sensor for determining an angle of a linkage member for controlling movement of at least part of the boom or the attachment. In one embodiment, the linkage member controls movement of the attachment relative to the arm.

[0015] In some embodiments, the boom and attachment has at least two potential points of maximum height and the height determination means determines the height of each of those at least two potential points of maximum height. If any one of the at least two potential points of maximum height reaches a predetermined height, the height limiter will prevent further raising of the boom or attachment.

[0016] In some embodiments, the height limiter prevents further raising of the boom by automatically controlling hydraulics that control the height of the boom or attachment. Depending upon the point of potential maximum height that reaches the height limit, the control of raising of the boom or attachment may vary somewhat. For example, if the height of the attachment reaches the predetermined maximum height, the height of the boom is controlled so that the boom can not be further raised and the height of the attachment is also controlled such that the attachment cannot be further raised relative to the boom. However, if a first arm of the boom has reached a maximum height but a second arm of the boom and the attachment are below the maximum height, then the first arm of the boom can be controlled such that it cannot be further raised but the second arm of the boom and the attachment may still be further raised as they are below the maximum height.

[0017] In one embodiment, the height determination means comprises calculation means that receives data from each of the plurality of sensors relating to an angle of the boom and an angle of the attachment, the height determination means determining the height of the boom and the attachment from calculations based on geometry or dimensions of the boom and geometry or dimensions of the attachment and the data relating to the angle of the boom and the angle of the attachment.

[0018] In one embodiment, the height determination means comprises calculation means that receives data from each of the plurality of sensors relating to an angle of a first arm of the boom, a second arm of the boom and an angle of the attachment, the height determination means determining the height of the boom and the attachment from calculations based on geometry or dimensions of the first arm of the boom, the second arm of the boom and the attachment and the data relating to the angle of the first arm of the boom, the second arm of the boom and the angle of the attachment. In a further embodiment, the height determination means also receives data from a sensor in relation to an angle of a linkage member for controlling movement of at least part of the boom or the attachment, [0019] In one embodiment, the only input available to an operator of the machine is selection of the attachment that is attached to the boom. In one embodiment, the operator selects the attachment attached to the boom by turning a key to an appropriate position to select an attachment from a set of attachments.

[0020] In one embodiment, the height limiter includes a control module having an operator's selection input, the operator selection input allowing an operator to only select an attachment type for an attachment that is attached to the boom.

[0021] In one embodiment, the control module includes a key slot for receiving a key, the operator inserting a key into the key slot and turning the key to select an attachment that is attached to the boom. The key may be turned from an off position to select the particular attachment that has been attached to the boom. In some embodiments, turning the key from an off position to select the particular attachment also acts to turn on the height limiter.

[0022] In some embodiments of the present invention, by providing a control module that only allows the operator of the machine to select the attachment that is attached to the boom, much simpler set up of the height limiter for the operator is achieved. Further, the amount of training required for the operator to use the height limiter is minimised. Further, the risk of the machine operator inputting incorrect information into the control module for the height limiter is significantly reduced.

[0023] In some embodiments, the sensors may comprise angle sensors. The sensors may comprise accelerometers.

[0024] The sensors transmit information to the height determination means. The height determination means may comprise appropriate software or computer code or algorithms written into a computational device. The computational device may be physically located within the control module of the height limiter. The computational device may be a microcomputer. The sensors may transmit data to the height determination means in any manner known to the person skilled in the art. In one embodiment, the sensors transmit data to the height determination means through one or more cables. The one or more cables may comprise part of a CAN bus system. In other embodiments, the sensors may transmit data wirelessly to the height determination means. The present inventors believe that use of a cabled or wired connection to transmit data from the sensors to the height determination means is like to be more robust during use, especially in instances where the height limiter is used to limit height of a machine that is used near live electrical wires. It will be understood that live electrical wires may result in the generation of large electrical fields, which could potentially disrupt wireless communications and thereby make the use of wireless communication between the senses and the height determination means less reliable.

[0025] Each of the sensors may be mounted within a housing. The housing may have connectors enabling appropriate cabling to be connected to the housing. The connectors may enable data to be sent from the sensors to the height determining means. Each housing may have two connectors. The connectors may be located on opposing faces of the housing. The two connectors may be electrically connected to each other.

[0026] It is desirable to position the sensors inside housings in order to protect the sensors from the environment of use. In this regard, it will be understood that earthmoving equipment is often used in dirty, dusty or muddy conditions with a real risk of impacts being placed on the equipment. Placing the sensors within respective housings will assist in isolating the sensors from the environment to a degree.

[0027] In some embodiments of the present invention, the geometry and/or dimensions of the boom may be preloaded into the height calculation means. When the operator selects the attachment that is attached to the boom, the calculation means obtains details as to the geometry and dimensions of the attachment and uses those details in order to calculate the height of the attachment. The details of geometry and dimensions of the attachment may be obtained from a lookup table programmed into the memory associated with the computational means on which the height calculation means is loaded. When the operator selects the attachment that is attached to the boom, the calculation means may obtain details of the geometry and/or dimensions of the attachment from the lookup table.

[0028] Any of the features described herein can be combined in any combination with any one or more of the other features described herein within the scope of the invention.

[0029] The reference to any prior art in this specification is not, and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge.

BRIEF DESCRIPTION OF DRAWINGS

[0030] Various embodiments of the invention will be described with reference to the following drawings, in which: [0031] Figure 1 shows a schematic side view of a front end loader having a height limiter in accordance with one embodiment of the present invention fitted thereto; [0032] Figure 2 is a similar view to that shown in figure 1, but with the sensors being shown mounted to the front end loader (the sensors are shown in somewhat exaggerated scale); [0033] Figure 3 is a flow chart showing a decision logic program used by the height limiter of one embodiment of the present invention to prevent the height of the boom or arm of the front end loader shown in figures 1 and 2 from breaching the maximum height limit; [0034] Figure 4 shows a schematic side view of an excavator having a height limiter in accordance with one embodiment of the present invention fitted thereto; [0035] Figure 5 is a similar view to that shown in figure 4, but with the sensors being shown mounted to the excavator (the sensors are shown in somewhat exaggerated scale); and [0036] Figure 6 shows a view of a front panel of a control module for use with a limiter in accordance with an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0037] It will be appreciated that the attached drawings have been provided for purposes of describing preferred embodiments of the present invention. Therefore, it will be understood that the present invention should not be considered to be limited solely to the features as shown in the attached drawings.

[0038] Figure 1 shows a front end loader 10. The front end loader 10 has a cabin 12. The operator sits in the cabin during use and controls operation of the front end loader from the cabin. The front end loader has an engine 14 and wheels 16, 18. Wheels 18 form the front wheels of the front end loader 10.

[0039] The front end loader also includes a boom arm 20. Boom arm 20 is mounted to the front end loader at pivot point 22 by use of pivot pins, as will be known to person skilled in the art. The boom arm 20 may be raised and lowered by operation of hydraulic cylinder 24.

Hydraulic cylinder 24 is pivotally connected at point 26 to the chassis or body of front end loader 10 and pivotally connected at point 28 to the boom arm 20. Extending the hydraulic cylinder 24 causes the distal end 30 of boom arm 20 to be raised upwardly, whilst retracting the hydraulic cylinder 24 causes the distal end 30 of boom arm 20 boom arm 20 to be lowered.

[0040] The distal end 30 of boom arm 20 carries a bucket 32. The bucket 32 is pivotally mounted to the distal end 30 of the boom arm 20 at pivot point 34. In order to cause the bucket 32 to rotate at pivot point 34, the linkage arrangement 36 has a linkage member 38 pivotally mounted to the boom arm 20 at a point intermediate the ends of the arm 20. A further linkage member 40 is pivotally connected at one end to the linkage member 38. Yet a further linkage member 42 is pivotally connected at one end to an end of the linkage member 40. The other end of linkage member 42 is pivotally connected to the bucket. And intermediate linkage member 44 is pivotally connected at one end to a distal end of the boom arm 20 and pivotally connected at its upper end to linkage member 42. A hydraulic cylinder (which is hidden in figure 1) can move the linkage member 38 by causing it to rotate about its lower pivot point (where it is pivotally connected to the boom arm). This causes the bucket to be caused to rotate.

[0041] The construction and arrangement of the boom arm, linkage member, hydraulic cylinders/hydraulic actuators and bucket for front end loaders would be well understood by persons skilled in the art and it need not be described any further detail. Persons skilled in the art will also appreciate that other arrangements may be used for mounting the bucket to the boom arm and for moving the bucket and the boom arm. In some instances, the bucket may be replaced with other attachments.

[0042] Movement of the boom arm, the linkage members and the bucket has the potential to change the maximum height of the boom arm, linkage members and bucket. As shown in figure 1, there are three points of potential maximum height, these being points F, E and G. Therefore, in order to maintain the height of the boom arm, linkages and bucket below a maximum height, it is necessary that the vertical height of points F, E and G remain below that maximum vertical height at all times.

[0043] The overall vertical heights to points F, E and G can be calculated from the following:

where hvF is the vertical height of point F, ABv is the vertical height of point B from point A, BKv is the vertical height from point B to point K and KFv is the vertical height from point K two point F.

where hvE is the vertical height of point E, ABv is the vertical height of point B from point A, BCv is the vertical height from point B to point C, and DE is added on as a fixed height, That as the maximum possible vertical distance from point D to point E.

where hvG is the vertical height of point G, ABv is the vertical height of point B from point A, BCv is the vertical height from point B to point C, and DGv is the vertical height from point D to point G (in figure 1, points C and D coincide and therefore are always at the same vertical height).

[0044] For the front end loader 10 shown in figure 1, the distance from point A to point B is fixed and known, as point B is a fixed point on the body of the front end loader 10. In order to determine the vertical height from point A to point B, an angle sensor 45 is mounted to the body of the machine. In one embodiment, the angle sensor 45 is mounted so that a longitudinal axis thereof is parallel to the line extending between points A and B. The angle sensor 45 can measure angle "a" and the vertical height between points A and B can be determined from the distance from A to B multiplied by sin a.

[0045] In order to determine the vertical height from point B to point K, an angle sensor 46, in the form of an accelerometer, is mounted to boom arm 20. In one embodiment, the angle sensor 46 is mounted such that it has longitudinal axis is parallel to the line extending from point B to point K. The accelerometer 46 provides signals or data indicative of the angle of the boom arm 20. By use of appropriate geometrical calculations, the vertical height from point B to point K can be determined (BKv = (length from B to K) * sin b, where b is the angle of B to K).

[0046] In order to determine the vertical height from point K to point F, an angle sensor in the form of an accelerometer 48 is mounted to linkage member 38. In one embodiment, the longitudinal axis of angle sensor 48 is generally parallel to a line extending from point k to point F. Accelerometer 48 measures the angle from point K to point F. By use of appropriate geometrical calculations, the vertical height from point B to point K can be determined (KFv = (length from K to F) * sin k, where k is the angle of K to F).

[0047] The value of hvF can then be calculated.

[0048] In order to calculate the vertical height from point B to point C, the accelerometer 46 is used to measure the angle from point B to point C. By use of appropriate geometrical calculations, the vertical height from point B to point C can be determined (BCv = (length from B to C) * sin b, where b is the angle of B to C, which is the same as the angle from B to K).

[0049] The value of hvE can then be calculated by using equation (2). As mentioned above, in equation 2, DE is added on as a fixed height and that height is set at the maximum vertical distance between points D and E.

[0050] In order to calculate the vertical height from point C/D (as mentioned above, for the front end loader 10, C and D are coincident points) to point G, the angle "g" is determined as follows - the angle "d" of the hitch is converted using a polynomial equation from the angle "k" as determined by the sensor 48. A fixed, known d-g angle offset for each attachment is then added to arrive at the final angle for D-G. By use of appropriate geometrical calculations, the vertical height from point D to point G can be determined (DGv = (length from D to G) * sin g, where g is the angle of D to G).

[0051] The value of hvG can then be calculated.

[0052] The sensors 45, 46, and 48 send data or measurements relating to the angle of the respective components described above to the height calculator. The height calculator is a program that has the mathematical equations (1), (2) and (3) programmed into it. The height calculator then determines the vertical height of each of points F, E and G. If any of the vertical heights hvF, hvE or hvG reach the maximum allowed vertical height, the controller sends a signal to prevent further raising of the boom and/or the bucket. The signal that is sent by the controller may be a signal that is sent to a solenoid valve in the hydraulic system of the front end loader that prevents further raising caused by operation of the hydraulic cylinder 24 by operation of the hydraulic cylinder that moves linkage member 38.

[0053] Figure 3 shows a flowsheet outlining the logic used in the controller. In figure 3, the sensors (shown at 60) send data on the angle of the respective components discussed above to the controller 62. The controller 62 includes the height calculation means that determines the height of points F, E and G. The controller checks (at 64) if the vertical height of any one of points F, E and G is at the maximum allowed height. If all of the heights of points F, E and G are below the maximum allowable height, the controller awaits the next calculation from the height determining means. Effectively, the decision-making returns from box 64 back to box 62. If the controller determines at box 64 that any of points F, E and G are at the maximum allowable height, the controller sends a control signal to prevent further raising of the boom arm and/or the bucket (in box 66).

[0054] In one embodiment, if the controller determines that point F is at the maximum height, then the boom arm 20 cannot be raised any further and the linkage 38 cannot be moved to a more vertical orientation. The control signal sent from the controller to the hydraulic system can ensure that occurs. If the controller determines that the height of point E is at the maximum, then the control signal sent from controller means that the boom arm 20 cannot be raised any further and the linkage 38 cannot be moved to a more vertical orientation. If the controller determines that the height of point G is that the maximum allowed height, then the controller sends a signal that means that the boom arm 20 cannot be raised any further and the linkage 38 cannot be moved or more vertical orientation and the bucket 32 cannot be further raised or rotated upwardly.

[0055] Figure 4 shows a side schematic view of excavator 100 in accordance with the present invention. The excavator 100 includes a cabin 102. Cabin 102 is mounted to rotate about a base 104. The excavator 100 has tracks 106 to allow the excavator to move along the ground.

[0056] The excavator 100 includes a boom having a first arm 108 and a second arm 110. In this particular art, the first arm 108 is typically referred to as a boom and the second arm 110 is typically referred to as a dipper and these terms will be used hereinafter in describing figure 4. The boom 108 is pivotally mounted to the chassis or body of the excavator 100 at point B. The dipper 110 is pivotally mounted to the boom 108 at point C/K (which is that the distal end of the boom 108).

[0057] A hydraulic cylinder 112 is pivotally mounted at its lower end to the chassis or body of the excavator 100 and pivotally mounted at its upper end to point 114 of the boom 108. Point 114 is located between the respective ends of the boom 108. In order to raise the boom 108, hydraulic cylinder 112 is extended. In order to lower the boom 108, hydraulic cylinder 112 is retracted.

[0058] A hydraulic cylinder 116 is pivotally mounted at one end to point 118 on the boom 108 and pivotally mounted at its other end to point 120 on the dipper 110. In order to raise and lower the dipper 110 relative to the boom 108, the hydraulic cylinder 116 is actuated. Retracting the hydraulic cylinder 116 causes the dipper 110 to be raised relative to the boom. Extending the hydraulic cylinder 116 causes the dipper 110 to lower relative to the boom 108.

[0059] A bucket attachment 122 is attached to the distal end of the dipper 110. The bucket 122 pivots about point D. In order to control pivoting of the bucket 122 relative to the dipper 110, a linkage member 124 is pivoted at one end to the dipper 110 at point 126 and pivoted at its upper end to a further linkage member 128. Further linkage member 128 is pivotally connected to the bucket 122. A hydraulic cylinder 130 is pivoted at point 132 to the dipper 110 and pivoted at point E to linkage members 124, 128. Extension of the hydraulic cylinder 130 causes the bucket 122 to rotate in an anticlockwise direction (as shown in figure 4) which effectively lowers the bucket. Retraction of the hydraulic cylinder 130 causes the bucket 122 to rotate in a clockwise direction (which effectively raises the bucket).

[0060] The construction of the boom arm and bucket attachment of the excavator 100 shown in figure 4 is essentially conventional and will be well understood by person skilled in the art.

[0061] There are three points on the boom arm of the excavator 100 that may form a maximum height of the boom arm, these being points F, E and G. The overall vertical heights to points F, E and G can be calculated from the following:

where hvF is the vertical height of point F, ABv is the vertical height of point B from point A, BKv is the vertical height from point B to point K and KFv is the vertical height from point K two point F.

where hvE is the vertical height of point E, ABv is the vertical height of point B from point A, BCv is the vertical height from point B to point C, CDv is the vertical height from point C to point D, and DE is added on as a fixed height, as the maximum possible vertical distance from point D to point E.

where hvG is the vertical height of point G, ABv is the vertical height of point B from point A, BCv is the vertical height from point B to point C, CDv is the vertical height from point C to point D, and DGv is the vertical height from point D to point G.

[0062] For the excavator 100 shown in figure 4, point C and point K are coincident points and may be interchanged in the above equations (la) to (3a).

[0063] For the excavator 100 shown in figure 4, the distance from point A to point B is fixed and known, as point B is a fixed point on the body of the excavator 100. In order to determine the vertical height from point A to point B, an angle sensor 133 is mounted to the body of the machine. In one embodiment, the angle sensor 133 is mounted so that a longitudinal axis thereof is parallel to the line extending between points A and B. The angle sensor 133 can measure angle "a" and the vertical height between points A and B can be determined from the distance from A to B multiplied by sin a. In order to determine the vertical height from point B to point K, an angle sensor, in the form of an accelerometer 134, is mounted to boom 108. The accelerometer 134 provides signals data indicative of the angle of the boom 108. By use of appropriate geometrical calculations, the vertical height from point B to point K can be determined (BKv = (length from B to K) * sin b, where b is the angle of B to K).

[0064] In order to determine the vertical height from point K to point F, angle k is calculated by adding a fixed known ck angle offset value to the value for the dipper angle from angle sensor 138 is mounted to the dipper arm 110. By use of appropriate geometrical calculations, the vertical height from point K to point F can be determined (KFv = (length from K to F) * sin k, where k is the angle of K to F).

[0065] The value of hvF can then be calculated.

[0066] In order to calculate the vertical height from point C to point D, an accelerometer 138 is used to measure the angle from point C to point D. By use of appropriate geometrical calculations, the vertical height from point C to point D can be determined (CDv = (length from C to D) * sin c, where c is the angle of C to D, or the angle from K to D).

[0067] The value of hvE can then be calculated by using equation (2a). As mentioned above, in equation 2a, DE is added on as a fixed height and that I had is set at the maximum vertical distance between points D and E.

[0068] In order to calculate the vertical height from point D to point G, an angle sensor in the form of an accelerometer 140 is mounted to the hitch that holds bucket 122. Accelerometer 140 measures the angle d. The angle from point D to point G is determined by adding the fixed known dg angle offset for each different attachment to the hitch angle d. By use of appropriate geometrical calculations, the vertical height from point D to point G can be determined (DGv = (length from D to G) * sin g, where g is the angle of D to G).

[0069] The value of hvG can then be calculated.

[0070] The sensors send data signals indicative of the respective angles that are being measured by the sensors to the controller. Software within the controller determines the height of points F, E and G. If any one of those points is at greater than the maximum allowable height, the controller sends a control signal to the hydraulic system to prevent further raising of that point. If point F is at the maximum height, the control signal limits raising of the boom 108. If point E is at the maximum height, the control signal prevents further raising of the boom 108 and the dipper 110. If point G is at the maximum height, the control signal prevents further raising of the boom, the dipper and the bucket.

[0071] A similar control logic diagram to that shown in figure 2 may be used with the excavator, albeit that the control signal has the ability to control the boom, the dipper and the bucket.

[0072] The sensors suitably send data relating to the angles that each sensor is measuring to the controller at an acceptable sampling rate. For example, the sensors may send data to the controller at a sampling rate of from 5 readings per second to 100 readings per second. It is envisaged that rates of 12 readings per second will provide commercially successful sampling rates. The height determining means calculates the height of the various points F, E and G at the same rate as the sampling rate. The data from the sensors may be sent via cables to the controller. The sensors and the controller may be interconnected by a CAN bus.

[0073] Figure 6 shows a front panel of a controller used with a height limiter in accordance with an embodiment of the present invention. As shown in figure 6, the front panel to the controller has a key slot 150. Key slot 150 enables a key to be inserted by the operator. Once the key has been inserted, the operator may turn the key to select an attachment that is attached to the machinery. These are set out in the front panel shown in figure 6 as "Att 1", "Att 2", "Att 3" and "Att 4". Each of these attachments corresponds to a particular attachment. For example, attachment 1 may be a standard bucket, attachment 2 may be a crib bucket, attachment 3 may be a grab or hammer and attachment 4 may be a hook, auger or tamper. The cabin of the vehicle will typically provided with a concordance table on which the attachment number is shown against the type of the attachment, thereby enabling very simple identification of the attachment for the operator.

[0074] Once the operator has determined what attachment has been attached to the vehicle, the operator inserts the key and turns the key to the relevant attachment number. This turns on the height limit. Further, the geometry and dimensions of the various attachments are included in the controller memory in the form of a lookup table. Once the operator has selected the particular attachment, the controller imports the relevant values into the height determining calculations.

[0075] After turning the key to the relevant attachment, the operator removes the key from the key slot 150 and the key is given to a site supervisor or spotter so that the operator cannot change the attachment number during operation. The operator should then check that the height limit is in operation by raising the attachment up and ensuring that it cuts out at maximum height and that any external signboards that may be mounted to the equipment are illuminated.

[0076] The height limiter of embodiments of the present invention, in having only the capability of allowing the operator to select the particular attachment that is attached to the equipment, makes training of operators for use of the height limiter very simple. Further, the system cannot be adjusted on-site or by the operator. The system cannot be adjusted by any mechanical means. This adds a further layer of safety to the height limiter. The maximum height value is entered into the controller by qualified technical staff prior to the height limiter of the machine being placed into operation on site. In instances where a fleet of machines is to be used in a similar environment (for example, where a fleet of machines is used to carry out work on railway lines having a maximum height that is set by the railway line operator in order to avoid electrocution risk), this "standard" maximum height can be entered into all of the height limiters used on the fleet of machines.

[0077] As can also be seen from figure 6, the front panel also includes lights to indicate that the limited is off, a light to indicate that the height limiter is on, a light to indicate that the height limit has been reached, a light indicating that the boom is to be lowered, a light indicating that the dipper is to be lowered, and a light indicating that the crowd is to be lowered. If a fault is determined in the system, a light next to the question mark on the front panel illuminates. If a fault is determined, the controller may act to prevent further upward operation of the arm and attachment until the fault has been corrected.

[0078] In the present specification and claims (if any), the word ‘comprising’ and its derivatives including ‘comprises’ and ‘comprise’ include each of the stated integers but does not exclude the inclusion of one or more further integers.

[0079] Reference throughout this specification to ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

[0080] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.

Claims (20)

1. A height limiter for a machine having a boom with an attachment mounted to the end of the boom, the height limiter including an operator input device for enabling an operator to select an attachment that is attached to the boom, a plurality of sensors, at least one sensor associated with the boom and at least one sensor associated with the attachment, a height determination means for receiving data from the plurality of sensors and for determining a height of the boom and a height of the attachment from the data, and control means for preventing further raising of the boom or attachment if the boom or attachment is at a height that is at a maximum height.

2. A height limiter as claimed in claim 1 wherein the at least one sensor associated with the boom comprises at least one sensor attached to the boom and the at least one sensor associated with the attachment comprises at least one sensor attached to the attachment.

3. A height limiter as claimed in claim 1 or claim 2 wherein the plurality of sensors includes a sensor for determining an angle of an arm of the boom and a sensor for determining an angle of the attachment that is attached to the boom.

4. A height limiter as claimed in claim 3 wherein the plurality of sensors includes a sensor for determining an angle of a first arm of the boom that is attached to the machine, a sensor for determining an angle of a second arm of the boom that is attached to the first arm, and a sensor for determining an angle of the attachment, the attachment being attached to the second arm of the boom.

5. A height limiter as claimed in claim 3 or claim 4 wherein the plurality of sensors further includes a sensor for determining an angle of a linkage member for controlling movement of at least part of the boom or the attachment.

6. A height limiter as claimed in any one of the preceding claims wherein the boom and attachment has at least two potential points of maximum height and the height determination means determines the height of each of those at least two potential points of maximum height, and if any one of the at least two potential points of maximum height reaches a predetermined height, the height limiter will prevent further raising of the boom or attachment.

7. A height limiter as claimed in any one of the preceding claims wherein the height limiter prevents further raising of the boom by automatically controlling hydraulics that control the height of the boom or attachment.

8. A height limiter as claimed in any one of the preceding claims wherein the height determination means comprises calculation means that receives data from each of the plurality of sensors relating to an angle of the boom and an angle of the attachment, the height determination means determining the height of the boom and the attachment from calculations based on geometry or dimensions of the boom and geometry or dimensions of the attachment and the data relating to the angle of the boom and the angle of the attachment.

9. A height limiter as claimed in claim 8 wherein the height determination means comprises calculation means that receives data from each of the plurality of sensors relating to an angle of a first arm of the boom, a second arm of the boom where the boom has a second arm and an angle of the attachment, the height determination means determining the height of the boom and the attachment from calculations based on geometry or dimensions of the first arm of the boom, the second arm of the boom and the attachment and the data relating to the angle of the first arm of the boom, the second arm of the boom and the angle of the attachment.

10. A height limiter as claimed in claim 9 wherein the height determination means also receives data from a sensor in relation to an angle of a linkage member for controlling movement of at least part of the boom or the attachment,

11. A height limiter as claimed in any one of the preceding claims wherein the only input to the height limiter available to an operator of the machine is selection of the attachment that is attached to the boom.

12. A height limiter as claimed in claim 11 wherein the operator selects the attachment attached to the boom by turning a key to an appropriate position to select an attachment from a set of attachments.

13. A height limiter as claimed in any one of the preceding claims wherein the height limiter includes a control module having an operator's selection input, the operator selection input allowing an operator to only select an attachment type for an attachment that is attached to the boom.

14. A height limiter as claimed in claim 13 wherein the control module includes a key slot for receiving a key, the operator inserting a key into the key slot and turning the key to select an attachment that is attached to the boom.

15. A height limiter as claimed in claim 14 wherein the key is turned from an off position to select the particular attachment that has been attached to the boom, and turning the key from an off position to select the particular attachment also acts to turn on the height limiter.

16. A height limiter as claimed in any one of the preceding claims wherein the sensors comprise accelerometers.

17. A height limiter as claimed in any one of the preceding claims wherein the sensors transmit data to the height determination means through one or more cables.

18. A height limiter as claimed in claim 17 wherein the one or more cables comprise part of a CAN bus system.

19. A height limiter as claimed in any one of the preceding claims wherein geometry and/or dimensions of the boom may be preloaded into the height calculation means and when the operator selects the attachment that is attached to the boom, the calculation means obtains details as to the geometry and dimensions of the attachment and uses those details in order to calculate the height of the attachment.

20. A height limiter as claimed in any one of the preceding claims wherein the height limiter sends a control signal to a hydraulics system to prevent further raising of the boom or attachment if the height limiter determines that one of the boom or the attachment has reached a maximum allowable height.