TECHNICAL FIELD

[0001] The present invention relates to materials handling and in particular to control of tension for a conveyor belt cleaner.

BACKGROUND

[0002] Conveyor belt cleaners remove carry-back from the conveyor belt. Carry-back is a residual amount of conveyed material that remains on the belt after the unloading end roller and runs back along the underside of the conveyor belt. Carry-back can cause belt mis-tracking or mis-alignment, reduces productivity and can exacerbate premature belt failure.

[0003] Known conveyor belt cleaners utilise mechanical, hydraulic or pneumatic tensioning arrangements to apply a force to bias the cleaner, typically a scraper blade or a rotating brush, towards the conveyor surface. When the conveyor is running in its usual direction of travel and carrying material, the material limits heat build-up in the cleaner. However, if the conveyor is reversed or if the conveyor is unloaded and not carrying material for a period of time, the interaction of the cleaner and the conveyor can generate heat build-up. Furthermore, as the conveyor belt is typically, though not limited to, a belt of rubber, rubber composite or synthetic material, if the conveyor is stopped, a heated cleaner, particularly such as a hot scraper blade, can thermally and mechanically damage the conveyor, if the tensioning arrangement continues to apply a force to bias the cleaner onto the conveyor surface.

SUMMARY OF INVENTION

[0004] A first aspect of the present invention provides a conveyor cleaning arrangement for cleaning material from a moving surface of a conveyor, the conveyor cleaning arrangement including at least a first cleaner and at least a first cleaner biasing arrangement, wherein; the first cleaner biasing arrangement includes a first operational state biasing the first cleaner towards the moving surface and a second operational state reducing or releasing the biasing such that the first cleaner is able to move away from the moving surface.

[0005] Another aspect of the present invention provides a conveyor cleaning arrangement for cleaning material from a moving surface of a conveyor, the conveyor cleaning arrangement including at least a first cleaner and at least a first cleaner biasing arrangement, wherein: the first cleaner biasing arrangement has at least a first operational state and a second operational state; in the first operational state of the first cleaner biasing arrangement, the first cleaner is biased towards the moving surface; in the second operational state of the first cleaner biasing arrangement, the bias of the first cleaner towards the moving surface is reduced or removed.

[0006] While in the first operational state the first cleaner is biased towards the moving surface, the first cleaner may be able to move towards or away from the moving surface. For example, if stubborn material is not easily removed by the first cleaner, the first cleaner may be pushed away from the belt by the material which overcomes an activating force energising or biasing the first cleaner towards the moving surface, although the first cleaner may be always biased towards the moving surface in the first operational state.

[0007] In the second operational state of the first cleaner biasing arrangement, when the bias of the first cleaner towards the moving surface is reduced or removed, the first cleaner is preferably urged away from the moving surface or moves away from the moving surface.

[0008] The first cleaner biasing arrangement may include at least one first cleaner actuator and a fluid pressure source. For example, the at least one first cleaner actuator may be or include a pair of fluid rams or a pair of fluid bellows. The fluid pressure source may derive from or may be locally piped water, gas (e.g., nitrogen) or air supply. Alternatively, the fluid pressure source may be or include a pressurised fluid reservoir. [0009] The first cleaner biasing arrangement may include a variable volume fluid storage chamber. The variable volume fluid storage chamber may be adjustable between at least a contracted volume and an expanded volume, the expanded volume being larger than the contracted volume.

[0010] In the first operational state of the first cleaner biasing arrangement, the fluid pressure source may be in fluid communication (such as via at least one conduit arrangement) with the at least one first cleaner actuator. In the second operational state of the first cleaner biasing arrangement, the fluid communication between the fluid pressure source and the at least one first cleaner actuator may be blocked, the at least one first cleaner actuator may be in fluid communication with the variable volume fluid storage chamber, and the variable volume fluid storage chamber may be adjusted to the expanded volume.

[0011 ] It will be appreciated that fluid communication in this specification, may be via at least one conduit arrangement, such as by one or more rigid and/or flexible pipes, hoses, ports, orifices, valves, etc., providing for fluid flow (such as volumetric change) and/or pressure transmission through the fluid. Consequently, one or more embodiments of the present invention may incorporate and employ one or more conduits for such fluid communication.

[0012] The first cleaner biasing arrangement may further include: a volume adjuster for adjusting a volume of the variable volume fluid storage chamber; and a blocking valve for selectively blocking the fluid communication between the fluid pressure source and the at least one first cleaner actuator.

[0013] The first cleaner biasing arrangement may further include a first control shaft, and the volume adjuster may include a first adjuster cam located on the first control shaft or a first adjuster crank located on the first control shaft. The blocking valve may be actuated by a first valve cam located on the first control shaft or by a first valve crank located on the first control shaft.

[0014] Alternatively, the blocking valve may be electrically actuated. For example, the blocking valve may include a solenoid operated lockout valve. Additionally, or alternatively, the volume adjuster may include an electrical or electro-mechanical linear actuator. For example, the volume adjuster may include a motor driving a screw, or an electro-magnetic linear actuator, driving a piston diaphragm or other moveable wall in the variable volume fluid storage chamber.

[0015] Alternatively, the volume adjuster may include a pneumatic actuator, such as a compressed air powered ram, that is configured to be pneumatically actuated to adjust the variable volume fluid storage chamber between the contracted volume and the expanded volume. Additionally or alternatively, the blocking valve may be pneumatically actuated.

[0016] It should be understood that any form of volume adjuster actuation (mechanical, pneumatic, electric or electro-mechanical) can be used with any form of blocking valve actuation (mechanical, pneumatic, electric or electro-mechanical). Similarly, where the at least a first cleaner includes multiple cleaners, the type of actuation of the volume adjuster for each cleaner individually may be of any form (mechanical, pneumatic, electric or electro-mechanical) and the type of actuation of the blocking valve of each cleaner individually may be of any form (mechanical, pneumatic, electric or electro-mechanical).

[0017] The fluid pressure source may be or include at least one hydraulic pressure accumulator. The at least one hydraulic pressure accumulator may include a liquid acted on by any one of, or a combination of, a weight, a pressurised gas and/or a mechanical spring. Pressurised gas accumulators for example, may utilise a diaphragm, piston, or bellows to form a boundary between the liquid and the pressurised (or compressed) gas. The at least one first cleaner actuator may be or may include a pair of hydraulic rams.

[0018] Alternatively, the fluid pressure source may be or include a compressed gas reservoir. The at least one first cleaner actuator may be or may include a pair of pneumatic actuators. Pneumatic actuators may be pneumatic rams, linear acting bellows, or air springs such as, but not limited to rolling lobe air bags. [0019] The moving surface of the conveyor may be a conveyor belt surface. The conveyor may be an endless conveyor. For example, the endless conveyor may be a continuous belt or a belt joined to form an endless loop. Alternatively, the conveyor may be a flexible metal mesh, or short sheets of material linked together forming an endless loop or any other known form.

[0020] The first cleaner may be or may include a scraper. For example, the scraper may include at least one scraper blade configured to contact or be biased towards the moving surface, in use. The scraper blade may be straight-edged, or the edge may be a smooth curve and/or the scraper blade may include teeth. Alternatively, the first cleaner may be or include a brush, such as for example a rotating brush. Flowever, if a brush is used, it is preferably a secondary or tertiary cleaner with the primary cleaner being a scraper. So, an arrangement having the scraper and the brush may be utilised.

[0021] The first biasing arrangement, when in the first operational state, may provide a substantially constant biasing force biasing the cleaner towards the moving surface. For example, this substantially constant biasing force can be most reliably achieved, with no additional regulating required, using a weight-loaded accumulator.

[0022] When the first biasing arrangement is in the second operational state, where the bias of the first cleaner towards the moving surface may be reduced or removed, the first cleaner may be urged to move away from, or may be moved away from the moving surface. For example, a cleaner actuator may be provided with a return spring, such as a mechanical return spring, so that when fluid pressure is reduced or released in the cleaner actuator, the actuator contracts, to pull the first cleaner away from the moving surface. If the fluid in the cleaner actuator is a gas, then the pressure of the gas may be reduced, but remain positive in the second operational state, requiring the return spring to overcome the force from the reduced pressure and retract the actuator. Flowever, if the fluid in the cleaner actuator is a liquid, the return spring may only be required if the suction from adjusting the variable volume fluid chamber to the expended volume does not generate sufficient reduction in pressure or a negative pressure in the cleaner actuators for the cleaner to drop or move away from the moving surface. Using the suction effect alone removes the need to overcome the return spring force when activating the cleaner towards the moving surface.

[0023] The at least a first cleaner may be or may include multiple cleaners. The at least a first cleaner may be or include a primary cleaner. Additionally, the at least a first cleaner may further include a secondary cleaner. Additionally, the at least a first cleaner may further include a tertiary cleaner.

[0024] Another aspect of the present invention may provide a method of controlling a conveyor cleaning arrangement, the conveyor cleaning arrangement for cleaning material from a moving surface of a conveyor, the conveyor cleaning arrangement including at least a first cleaner and at least a first cleaner biasing arrangement having a fluid pressure source, at least a first cleaner actuator, a variable volume fluid storage chamber, a volume adjuster for adjusting the variable volume fluid storage chamber between a contracted volume and an expanded volume, and a fluid source blocking valve; the first cleaner biasing arrangement having at least a first operational state and a second operational state, in the first operational state of the first cleaner biasing arrangement, the fluid pressure source is in fluid communication with the at least a first cleaner actuator such that the first cleaner is biased towards the moving surface, in the second operational state of the first cleaner biasing arrangement, fluid communication between the fluid pressure source and the at least a first cleaner actuator is blocked by the fluid source blocking valve and the variable volume fluid storage chamber is expanded, enabling (or for example, generating an effective) transfer of fluid from the at least a first cleaner actuator into the variable volume fluid shortage chamber, such that the first cleaner is released from being biased towards the moving surface, wherein the method of controlling the conveyor cleaning arrangement includes: selecting between the first operational state and the second operational state; wherein, when the first operational state is selected, the method includes adjusting the variable volume fluid storage chamber to the contracted volume, and opening the fluid source blocking valve to provide fluid communication between the fluid pressure source and the at least one cleaner actuator; and wherein when the second operational state is selected, the method includes closing the fluid source blocking valve to prevent fluid communication between the fluid pressure source and the at least a first cleaner actuator, and adjusting the variable volume fluid storage chamber to the expanded volume.

[0025] When the variable volume fluid storage chamber is adjusted to the contracted volume of the first operational state, the fluid displaced therefrom preferably enters the at least one cleaner actuator to bias the cleaner towards the moving surface. Conversely, when the variable volume fluid storage chamber is adjusted to the expanded volume of the second operational state, the fluid drawn into it is preferably drawn from the at least one cleaner actuator to reduce or remove the bias of the cleaner towards the moving surface, and preferably moves the cleaner away from the moving surface.

[0026] The selecting between the first operational state and the second operational state may include determining at least one operational parameter, and selecting the operational state in dependence on the at least one operational parameter. The at least one operational parameter may include one or more parameters selected from conveyor surface speed, conveyor surface motion direction, cleaner temperature and/or an external signal such as conveyor load weigher or weightometer data (load of material being carried and moved by the conveyor), a cleaner biasing arrangement switch position or a signal from a control system. It will be appreciated that a conveyor weightometer is known in the art and can include conveyor belt scales or continuous weighers, such as used at bulk material handling facilities. For example, a belt conveyor scale system weigher weighs items on a moving conveyor belt by weighing the belt load and measuring belt speed.

[0027] The first cleaner biasing arrangement may further include a fluid storage blocking valve for selectively permitting or blocking fluid communication between the variable volume fluid storage chamber and the at least a first cleaner actuator: when the first operational state is selected, the method may include closing the fluid storage blocking valve after adjusting the variable volume fluid storage chamber to the contracted volume; and when the second operational state is selected, the method may include opening the fluid storage blocking valve before adjusting the variable volume fluid storage chamber to the expanded volume.

[0028] The fluid storage blocking valve may therefore be used to effectively communicate the variable volume fluid storage chamber with the cleaner actuator(s) when the variable volume fluid storage chamber is adjusted in volume, but then isolate the variable volume fluid storage chamber. For example, the fluid storage blocking valve may be used to isolate the variable volume fluid storage chamber while the first cleaner biasing arrangement is in the first operational state, but permitting fluid communication between the variable volume fluid storage chamber and the at least a first cleaner actuator during transitions between the first and second operational states and whilst in the second operational state.

[0029] Alternatively, the fluid storage blocking valve may only be open to permit fluid communication between the variable volume fluid storage chamber and the at least a first cleaner actuator during transitions between the first and second operational states and then be re-closed when the first cleaner biasing arrangement is in the second operational state.

[0030] To this end, when the first operational state is selected, the method may further include opening the fluid storage blocking valve before adjusting the variable volume fluid storage chamber to the contracted volume; and when the second operational state is selected, the method may include closing the fluid storage blocking valve after adjusting the variable volume fluid storage chamber to the expanded volume.

[0031] Conversely, the fluid storage blocking valve may be omitted and the variable volume fluid storage chamber may be in fluid communication with the first cleaner actuator(s) at all times.

[0032] The adjusting the variable volume fluid storage chamber to the contracted volume may include rotating a control shaft; and the adjusting the variable volume fluid storage chamber to the expanded volume may include rotating said control shaft. Additionally, the step of opening the fluid source blocking valve may include the step of rotating the control shaft and the step of closing the fluid source blocking valve may include the step of rotating the control shaft. Additionally or alternatively, the step of selecting between the first and second operational state may be manual or may include a manual override, the or each step of rotating the control shaft being a manually triggered rotation or a physical manual rotation of said control shaft.

BRIEF DESCRIPTION OF DRAWINGS

[0033] In the drawings:

[0034] Figure 1 is a schematic diagram of at least one cleaner biasing arrangement for a conveyor cleaning arrangement according to one possible embodiment of the present invention.

[0035] Figure 2 shows a side view of a primary cleaner and a secondary cleaner on a portion of a conveyor.

[0036] Figure 3 is a schematic diagram of a cleaner biasing arrangement for a conveyor cleaning arrangement such as shown in Figure 1 in a first operational state according to at least one possible embodiment of the present invention.

[0037] Figure 4 is a schematic diagram of the cleaner biasing arrangement of Figure 3 in a second operational state according to at least one possible arrangement of the present invention.

[0038] Figure 5 is a schematic diagram of a cleaner biasing arrangement for a conveyor cleaning arrangement of an embodiment of the present invention using a two-port valve.

[0039] Figure 6 is a schematic diagram of a cleaner biasing arrangement for a conveyor cleaning arrangement of an embodiment of the present invention using two two-port valves.

[0040] Figure 7 is a schematic diagram of a partially electrically actuated cleaner biasing arrangement for a conveyor cleaning arrangement of an embodiment of the present invention. [0041] Figure 8 is a schematic diagram of a partially pneumatically actuated cleaner biasing arrangement for a conveyor cleaning arrangement of an embodiment of the present invention.

[0042] Figure 9 is a schematic diagram of a more pneumatically actuated cleaner biasing arrangement for a conveyor cleaning arrangement of an embodiment of the present invention.

[0043] Figure 10 is a schematic diagram of a more electrically actuated cleaner biasing arrangement for a conveyor cleaning arrangement of an embodiment of the present invention.

[0044] Figure 11 is a flow diagram of the operation of an embodiment of the present invention.

[0045] Figure 12 shows an electronic control arrangement of an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

[0046] Referring initially to Figure 1 , there is shown a conveyor cleaning arrangement 1. There are two cleaners shown in this example, a first cleaner 4 such as a primary scraper and a second cleaner 5 such as a secondary scraper. The first cleaner 4 is actuated by two first cleaner actuators 14, 15 which are part of a first cleaner biasing arrangement 11. When the first cleaner 4 is in use, the first cleaner actuators 14, 15 are in fluid communication with the first fluid pressure source 23 via the first cleaner actuator conduit 20, the first fluid pressure source conduit 26 and the first fluid source blocking valve 30. In this case, the fluid source blocking valve 30 would be open to permit said fluid communication between the first cleaner actuator conduit 20 and the first fluid pressure source conduit 26.

[0047] Similarly, when the second cleaner 5 is in use, the second cleaner actuators 16, 17 of the second cleaner biasing arrangement 12 are in fluid communication with the second fluid pressure source 24 via the second cleaner actuator conduit 21 , the second fluid pressure source conduit 27 and the second fluid source blocking valve 31. In this case, the second fluid source blocking valve 31 would be open to permit said fluid communication between the second cleaner actuator conduit 21 and the second fluid pressure source conduit 27.

[0048] As shown in Figure 2, the first cleaner 4 can be a primary cleaner such as primary scraper 7, which can be biased towards the moving surface 3 of conveyor 2 by part of the first cleaner biasing arrangement 11 including the first cleaner actuator 14. The second cleaner 5 can be a secondary cleaner such as secondary scraper 8 which can be biased towards the moving surface 3 of conveyor 2 by part of the second cleaner biasing arrangement 12 including the second cleaner actuator 16.

[0049] Returning to Figure 1 , the first and second fluid pressure sources 23 and 24 each include a respective weight-loaded hydraulic accumulator 45. Each hydraulic accumulator 45 has an accumulator chamber 47 formed in part by a moveable wall such as piston 48, which is acted on by the weight of a mass 49. In this way, the pressure in the conduits 26, 27 is substantially constant, providing in use, when the first and second fluid pressure source conduits 26, 27 are in fluid communication with the respective first or second cleaner actuator conduits 20 or 21 , a substantially constant actuating force urging the respective first or second cleaner 4 or 5 towards the conveyor. These actuating forces are primarily determined by the mass 49 and gravity, so do not vary significantly within the range of travel of the cleaner actuators 14, 15, 16, 17 and the range of travel of the weight-loaded hydraulic accumulators 45.

[0050] A supply arrangement 50, such as a hydraulic handpump and a fluid tank, can be selectively connected by supply valves 53 to the accumulator chambers 41 via supply conduits 54. This can be used, for example, to service the cleaner biasing arrangements 11, 12, such as depressurising the hydraulic conduits and volumes, or adding fluid to ensure the cleaner actuators 14, 15, 16, 17 and the hydraulic accumulators 45 are within a working range. Flowever, the supply arrangement 50 is not required to perform the function of releasing the cleaners 4, 5 away from the moving surface of the conveyor when required, such as when the conveyor is not carrying load past the cleaners 4, 5, either because the conveyor has stopped or no material is in the vicinity of the cleaners 4, 5. Other reasons can be the conveyor direction is temporarily reversed or that the cleaners 4, 5 are too hot. Such events can be detected, or if any of these situations are anticipated, a control signal can be sent by an operator or control system to change the operational state.

[0051 ] To allow the first cleaner 4 to be released away from the conveyor surface, the fluid communication between the first cleaner actuator conduit 20 and the first fluid pressure source conduit 26 is blocked by the first fluid source blocking valve 30. Then the first variable volume fluid storage chamber 33 can be expanded in volume, by for example driving the first storage volume adjuster 42 upwards in the manifold 39 of Figure 1. The expansion of the first variable volume fluid storage chamber 33 draws fluid from the first cleaner actuators 14, 15, via the first cleaner actuator conduit 20 in the release direction as indicated by the arrow R, through the first storage volume conduit 36 into the first variable volume fluid storage chamber 33.

[0052] Similarly, to allow the second cleaner 5 to be released away from the conveyor surface, the fluid communication between the second cleaner actuator conduit 21 and the second fluid pressure source conduit 27 is blocked by the second fluid source blocking valve 31. Then the second variable volume fluid storage chamber 34 can be expanded in volume, by for example driving the second storage volume adjuster 43 upwards in the manifold 39 of Figure 1. The expansion of the second variable volume fluid storage chamber 34 draws fluid from the second cleaner actuators 16, 17, via the second cleaner actuator conduit 21 in the release direction as indicated by the arrow R, through the second storage volume conduit 37 into the second variable volume fluid storage chamber 34.

[0053] Conversely, the flows are reversed when the variable volume fluid storage chambers 33, 34 are contracted, driving fluid in the opposite, actuating direction A to actuate the first and second cleaner actuators 14, 15, 16, 17 to urge the first and second cleaners 4, 5 towards the conveyor.

[0054] The first and second blocking valves 30, 31 and the first and second variable volume fluid storage chambers 33, 34 can be controlled by any known means, but in Figure 1 , a displacement driver 40 such as a motor is shown to drive a control shaft arrangement 41. The control shaft arrangement can for example include multiple cams on the shaft, timed to actuate the blocking valves and the first and second storage volume adjusters 42, 43 and adjust the variable volume fluid storage chambers 33, 34 in the desired sequence and for the desired displacement.

[0055] The control shaft arrangement can include eccentric devices or features such as cranks or the aforementioned cams. When using cranks, additional devices such as connecting rods or scotch yokes can be used to accommodate the misalignment as the crank rotates and to assist in converting rotational motion into linear motion.

[0056] Figures 3 and 4 show the first cleaner biasing arrangement 11 in the first and second operational states respectively. The first operational state 60 is shown in Figure 3, which is essentially an actuating condition where the weight-loaded hydraulic accumulator 45 is controlling the pressure in the first cleaner actuators 14, 15, biasing the first cleaner 4 towards the conveyor with a substantially constant force. The generally small displacements of the cleaner 4 towards and away from the surface of the conveyor during use in this first operational state 60 transfer fluid back and forth between the first cleaner actuators 14, 15 and the weight-loaded hydraulic accumulator 45.

[0057] In this first operational state 60 in Figure 3, the displacement driver 40 has rotated the control shaft arrangement including control shaft 74 such that the first storage volume cam 75 has displaced the first storage volume adjuster 42 so that the first variable volume storage chamber 33 has the contracted volume 70. In other words, the first variable volume storage chamber 33 has the contracted volume 70 in the first operational state 60. The blocking valve cam 76 on the control shaft 74 has also been rotated to place the first blocking valve 30 in the open state for fluid communication between the first fluid pressure source 23 and the first cleaner actuators 14, 15. The control shaft arrangement also includes a handle 77 for manual operation. The first variable volume fluid storage chamber 33 includes a return spring 72 to ensure that the first storage volume adjuster 42 follows the first storage volume cam 75. A check valve 73 is shown between the fluid pressure source conduit 26 and the storage volume conduit 36. The check valve 73 is configured to prevent, or at least reduce the likelihood of over-pressure in the storage volume conduit 36 and variable volume fluid storage chamber 33. If the variable volume fluid storage chamber 33 is in permanent fluid communication with the cleaner actuators 14, 15, then the check valve 73 may not be necessary, but for example when utilising a blocking valve 30 of the type shown, then it is possible for the storage volume conduit to be blocked.

[0058] Depending on whether the blocking valve 30 is normally open or normally closed, the rotational position of the blocking valve cam 76 can be aligned with the rotational position of the of the first storage volume cam 75, or rotated by ninety or one-hundred-and-eighty degrees depending on the cam profile and the rotational angle that the control shaft 74 is rotated through.

[0059] In the second operational state 61 shown in Figure 4, the first cleaner 4 is in the retracted or released condition. The weight-loaded hydraulic accumulator 45 of the first pressure source 23 is now isolated by the fluid source blocking valve 30, with the displacement driver 40 having rotated the control shaft 74 to rotate the blocking valve cam 76. The storage volume cam 75 has also been rotated to allow the storage volume adjuster 42 to increase volume of the variable volume fluid storage chamber 33 to the extended volume 71 , assisted by the return spring 72. In other words, the first variable volume storage chamber 33 has the extended volume 71 in the second operational state 61. This has drawn fluid out of the cleaner actuators 14, 15 which may also incorporate return springs if required and released the first cleaner 4 from the conveyor.

[0060] As the first fluid pressure source 23 is isolated in the second operational state 61 as shown in Figure 4, the first cleaner 4 can be released without discharging pressure to a tank. The position of the weight-loaded hydraulic accumulator 45 does not change substantially. Then when returning to the first operational state 60 as shown in Figure 3, the first variable volume fluid storage chamber 33 reverts to the contracted volume 70, re-engaging the first cleaner 4 with or towards the conveyor.

If due to a temperature change or other reason for fluid volume changes, the first cleaner 4 is not quite engaged with the conveyor, or back to a working position, any small further displacement required will be supplied by fluid from the fluid pressure source 23 once the blocking valve 26 is opened to provide fluid communication once again between the first cleaner actuators 14, 15 and the fluid pressure source 23. Alternatively, if the contraction of the variable volume fluid storage chamber 33 to the contracted volume 70 displaces more fluid than required to return the first cleaner actuators 14, 15 to the working position on or close to the conveyor moving surface, the check valve 73 can allow excess fluid to pass back to the fluid pressure source 23, preventing excess pressure which could otherwise generate excess load on the first cleaner 4.

[0061 ] Figure 5 shows a modification to the first cleaner biasing arrangement 11 of Figures 3 and 4, in the first operational state 60 of Figure 3. The blocking valve 30 is another 2-position valve, but in this example, only 2-port for controlling fluid communication between the first fluid pressure source 23 and the cleaner actuators 14, 15. When in the first operational state 60, bidirectional flow is permitted through the fluid source blocking valve 30, between the fluid source 23 and the cleaner actuators 14, 15. In the other position of the blocking valve 30, flow can be blocked, or a check valve can be used to block flow from the fluid pressure source 23 to the cleaner actuators, 14, 15, but permit overpressure in the cleaner actuators 14, 15 and the variable volume fluid storage chamber 33 to be released to the fluid pressure source 23. In this example, the variable volume fluid storage chamber 33 is permanently in fluid communication with the cleaner actuators 14, 15.

[0062] In Figure 6 a first fluid storage blocking valve 80, operated by a blocking valve cam 81 on control shaft 74, is shown in the first storage volume conduit 36.

The first cleaner biasing arrangement 11 is shown in the second operational state 61. The blocking valve 80 is another 2-port, 2-position valve, but is in the blocked position when in the first operational state, where it can include a check valve to only block fluid flow into the variable volume fluid storage chamber 33. This can protect the variable volume fluid storage chamber from the operating pressure and particularly any spikes in operating pressure of the cleaner actuators 14, 15, but allow over-pressure from the variable volume fluid storage chamber 33 to be released back via the similar check valve in the first fluid source blocking valve 30. However, as shown in Figure 6 fluid storage blocking valve 80 is shown open as the first cleaner biasing arrangement 11 is shown in the second operational state 61 or at least in the transition into the second operational state 61. If the first cleaner biasing arrangement 11 is to be held in the second operational state 61 for a significant period of time, the first fluid storage blocking valve 80 can be closed, until the transition to the first operational state is required for example.

[0063] The use of adjuster cams and/or valve cams can be exchanged for adjuster cranks and/or valve cranks driven by the control shaft, but although the timing of the cranks can be altered between the adjuster 42 and the valve(s) 30, 80, cams can also permit variation in throw profile vs rotation, so the blocking valve 80 could indeed be closed in the first operational state 60 and the second operational state 61 and only open for the transitions between the two states.

[0064] Figures 7 to 10 show other valve and adjuster actuation types. For example, Figure 7 shows the first cleaner biasing arrangement 11 in the first operational state 60, similar to Figure 3. However in Figure 7, while the first storage volume adjuster 42 is again actuated by the first storage volume cam 75 on the control shaft 74 driven by a stepper motor or similar displacement driver 40, the first fluid source blocking valve is a solenoid operated blocking valve 30b operated by a valve solenoid 90. The solenoid operated blocking valve 30b can also be operated manually using a manual override input 91. Using a solenoid operated valve 30b allows the valve operation to be variably timed relative to the operation of the adjuster 42.

[0065] Figure 8 shows the first cleaner biasing arrangement 11 in the second operational state 61 , similar to Figure 4. However in Figure 8, while the actuation of the first storage volume adjuster 42 is again unchanged, the first fluid source blocking valve is a pneumatically actuated blocking valve 30c actuated by an external pneumatic pilot pressure signal 93. The pneumatically actuated blocking valve 30c can also include a manual override input 91 to permit manual operation. [0066] Figure 9 shows the first cleaner biasing arrangement 11 in the first operational state 60, similar to Figures 3 and 7. Flowever in Figure 9 the control of the adjuster 42 and the first fluid source blocking valve is pneumatic. The first fluid source blocking valve is a pneumatic-pilot operated blocking valve 30c actuated by an external pneumatic pressure signal 93. The pneumatic-pilot operated blocking valve 30c can also include a manual override input 91 to permit manual operation. The first storage volume adjuster 42 is operated by a pneumatic actuator 95. The pneumatic actuator for the volume adjuster can also include an override lever 96 for manually operating the adjuster 42.

[0067] Additionally in Figure 9, the fluid pressure source 23 is a hydro-pneumatic piston-type accumulator 97. If the gas charging arrangement is connected to a source of pressurised air on site, the piston-type accumulator 97 can optionally be used as an air-to-hydraulic-fluid separating device, with the pressurised air being permanently applied on one side of the piston. In this case, if the pressure required in the hydraulic portion of the arrangement is higher than the air supply pressure, a rod can extend through the fluid chamber to reduce the pressure area on the hydraulic fluid side of the piston to the air side of the piston. If the gas pressures are relatively low, such as typical pressurised air supply pressure, then using air can be acceptable. Flowever, if the gas volume is charged from the site supply when the hydraulic pressure is vented through the supply arrangement (such as described for Figure 1), then the gas volume closed off from the site supply and the hydraulic arrangement pressurised using the supply arrangement, then the pressure in the gas volume can rise above safe pressure for air, so nitrogen or a similar inert gas is preferably used.

[0068] Figure 10 shows the first cleaner biasing arrangement 11 in the second operational state 61 , similar to Figures 4 and 8. Flowever in Figure 10 the control of the adjuster 42 and the first fluid source blocking valve 30b is electrical or electro mechanical. The blocking valve 30b is actuated by the valve solenoid 90 or optionally, by a manual override input 91. The first storage volume adjuster 42 is actuated by an electrical or electro-mechanical linear actuator 100 such as an electro-magnetic actuator, or as shown a displacement driver 40 such as a stepper motor driving a screw 101. If the displacement driver 40 outputs a rotation, then a crank handle 77 can be provided for manual operation. Alternatively, if the actuator 100 is entirely linear, a lever can be used as was shown in Figure 9 for manual override of the fluid storage chamber actuator 42.

[0069] Additionally in Figure 10, the fluid pressure source 23 is a hydro-pneumatic bladder-type accumulator 102. The use of hydro-pneumatic accumulators rather than weight- or mass-loaded accumulators provides a spring rate determined by the gas volume in the hydropneumatic accumulator, rather than providing a constant force of the cleaner actuators on the scraper.

[0070] Although Figures 3 to 10 have been described with reference to the first cleaner 4 and first cleaner biasing arrangement 11 , it will be appreciated that similar description is applicable to the second cleaner 5 and the second cleaner biasing arrangement 12. That is, in some embodiments, the second cleaner biasing arrangement 12 may comprise the features described with reference to one or more of Figures 3 to 10. Similarly a third cleaner biasing arrangement may be provided and the above description of Figures 3 to 10 is also applicable to such a third cleaner biasing arrangement. The form of actuation (mechanical, pneumatic, electric or electro-mechanical) of the volume adjuster and/or the blocking valve can vary between such features of any second and third biasing arrangements where provided.

[0071] Figure 11 shows a flow diagram of an example of the steps of operation 120 of the first cleaner biasing arrangement. It will be appreciated that the flow diagram of Figure 11 may also be applicable to the second cleaner (or any additional) biasing arrangement. Initially the desired mode of operation is determined at the first step

121. This can be in dependence on any or all of conveyor speed, direction or scraper temperature, weight on the conveyor, or other inputs. In other words, the desired mode of operation is determined based on a value of one or more conveyor operating parameters. If the scraper should be in the first operational mode, in which the scraper is engaged towards the conveyor, the cleaner engaged mode is entered

122. From there the next step 123 is to determine whether the operational mode that the scraper is in matches the desired operational mode. If at step 123, the position of the scraper is already in the engaged position, a change of operational mode is not required, so the arrangement remains in the first operational mode 124, i.e. the cleaner engaged mode.

[0072] If at step 123, the position of the scraper is not already in the engaged position, a change of operational mode is required, so the volume in the variable volume fluid storage chamber is adjusted to the contracted volume at step 125. In this position, the fluid from the variable volume fluid storage chamber is pushed into the actuators towards the engaged position. Then in step 126, communication is opened between the fluid pressure source (such as a hydraulic accumulator) and the cleaner actuators, to ensure the actuators are loaded towards the conveyor belt.

The timing of the opening of fluid communication 126 and the adjustment of the volume of the fluid storage chamber 125 can be varied, with for example, the communication optionally being opened before the variable volume fluid storage chamber is fully compressed to the contracted volume. Then the operation returns to the determining the desired operational mode step 121.

[0073] If, when the mode of operation is determined in initial step 121 , the scraper should alternatively be in the second operational mode, in which the scraper is disengaged away from the conveyor, the cleaner disengaged mode is entered 127. From there the next step 128 is to determine once again whether the operational mode that the scraper is in matches the desired operational mode. If at step 128, the position of the scraper is already in the disengaged position, a change of operational mode is not required, so the arrangement remains in the second operational mode 129, i.e. the cleaner disengaged mode.

[0074] If at step 128, the position of the scraper is not already in the disengaged position, a change of operational mode is required, so communication between the fluid pressure source (such as a hydraulic accumulator) and the cleaner actuators is closed in the step 130, to prevent the fluid pressure source from continuing to energise the actuators towards the conveyor belt. Then at step 131 , the volume in the variable volume fluid storage chamber is adjusted to the expanded volume. In this position, fluid is drawn into the variable volume fluid storage chamber, drawing the actuators away from the engaged position into the disengaged position. Then the operation returns to the determining the desired operational mode step 121.

[0075] Figure 12 shows an electronic control arrangement 150 for the conveyor cleaning arrangement 1 such as shown by way of example in Figure 1. Parameter inputs such as scraper actuator pressure 151 , scraper temperature 152 and at least one scraper position 153 are sensed, using sensors, locally as they relate specifically to the conveyor cleaning arrangement and its scraper, and input to the local controller 156, which is in proximity to the scraper(s). The scraper actuator pressure can be sensed in the hydraulic conduits away from the actuators or in the actuators as the pressure should not vary significantly within the associated hydraulic (or pneumatic) volume if there are no damping orifices in the circuit. The pressure indicates the force applied by the actuator(s) to the scraper, with the force from each actuator being determined by the pressure and the effective pressure area of the actuator.

[0076] The scraper temperature can indicate, for example, that there is insufficient flow rate of material along the conveyor to take heat away from the scraper blade. Scraper wear can be detected by monitoring scraper position sensed at one position on the scraper, or at more than one position. For example, if there is a first scraper position sensor 153 at or towards one end of the scraper and a second scraper position sensor 154 at or towards the opposite end of the scraper, then if there is uneven wear from one end of the scraper to the other, due to offset loading on the conveyor for example, then a more representative picture of the wear can be obtained than using only one scraper position sensor. The scraper position sensor(s) can also be used to verify the expected position of the scraper from biased towards the conveyor, to released away from the conveyor.

[0077] Sensors for parameters such as conveyor load 155, conveyor speed 158, conveyor direction 159 and manual override 160 for the automatic control can also be located locally and input into the local controller 156. Alternatively, one or more of these parameter inputs can be sensed less directly. For example, in Figure 12 the load sensor 155 is a weightometer which is an important input to the plant programmable logic controller (PLU) 157, a rugged industrial computation device. Programmable logic controller may also be abbreviated as PLC. Weight of material conveyed is a commonly measured conveyor parameter. The PLU 157 is connected to other inputs and/or outputs 163 and either wired or wirelessly connected to the local controller 156 located near the scrapers, preferably for bi-directional communication. Some parameter inputs such as conveyor speed may be both remotely and locally sensed and the manual override input can also be provided by both a remote and a local switch.

[0078] It will be appreciated that a conveyor weightometer is known in the art and can include conveyor belt scales or continuous weighers, such as used at bulk material handling facilities. For example, a belt conveyor scale system weigher weighs items on a moving conveyor belt by weighing the belt load and measuring belt speed.

[0079] The local controller 156 also outputs control signals to control devices such as the valve 161 and the motor 162. If the valve(s) and the variable volume fluid storage change adjuster are driven by cams or other eccentric devices on a common control shaft, then just one displacement driver such as motor 162 may be used as the output to drive the rotation of the control shaft. Alternatively, as shown, the valve 161 can be controlled by a separate output to the displacement driver or motor 162 driving the variable volume fluid storage change adjuster, which allows more flexibility in the timing between the valve and adjuster operations.

[0080] Although Figure 12 is discussed in relation to a single cleaner biassing arrangement, such as the first cleaner biasing arrangement, it should be readily appreciated that, it can be extended to monitor and control the biasing arrangements of multiple local cleaners such as a second and optionally a third cleaner arrangement. When more than one cleaner arrangement is present (i.e. when the primary cleaner is supplemented by a secondary and optionally a tertiary cleaner), while some inputs such as conveyor speed, direction and load carried may be common between the primary, secondary and tertiary cleaners, other inputs and outputs are specific to the individual first, second or third cleaner. For example, the scraper actuator pressure, scraper temperature and the scraper first (and where provided second) position inputs are duplicated for each additional cleaner as they can be different for each cleaner.

[0081 ] In this case, if the wear of the scraper of one cleaner is greater than a pre-determ ined amount, that scraper can be released or drawn away from the moving surface, leaving another scraper operating normally. The local controller 156 can signal the plant PLC 157 that the scraper needs attention. The wear of the individual scraper can be overall wear as sensed by a single scraper position sensor or by an average of the first and second position sensors 153, 154 for the individual scraper. So when such overall wear is larger than a predetermined amount, the controller can release the respective scraper. Additionally, the wear can be uneven wear, when the wear is greater towards one end of the scraper blade than the other by more than a predetermined measurement (as sensed by the first and second scraper position sensors), so again the respective scraper can be released from operation.

[0082] Therefore control outputs such as the valve 161 (where a separate control of the valve is required) and the displacement driver or motor 162 can be duplicated for any additional cleaners such as a second cleaner and optionally a third cleaner.

This will permit the biasing of each cleaner towards the moving surface to be individually controlled, allowing overly or unevenly worn cleaners to have the bias towards the moving surface removed, selectively releasing the individual cleaner while maintaining the operation of other cleaners within the individually predetermined wear ranges. Similarly as the temperature of the scraper of each cleaner is sensed, overly hot cleaners can be selectively released. The type of fault, overall wear, uneven wear or overheating, can be communicated back to the plant PLC 157 to enable personnel to be dispatched to the location to physically inspect, repair or replace the individual scraper blade.

[0083] The monitoring of the position of individual scrapers can also be used to verify expected operation and again if outside predetermined ranges, a possible fault can be communicated by the local controller 156 to the plant PLC 157 to enable personnel to be dispatched and remedial action taken.

[0084] Throughout this specification, the fluid pressure source can be a site supply of liquid or gas, or it can be a hydraulic pressure accumulator, or it can be a pressurised gas reservoir. Examples of hydraulic pressure accumulators include mechanical spring-loaded hydraulic accumulators in addition to the illustrated weight-loaded hydraulic accumulators or pressurised gas hydraulic accumulators. Accumulators can use pistons or diaphragms as shown, or bellows as is also known. Where the fluid pressure source is hydraulic, the cleaner actuators can be hydraulic rams. Where the fluid pressure source is gas or pneumatic, the cleaner actuators can be pneumatic actuators.

[0085] Although the cleaners are labelled first, second and third cleaners, these may include, or be referred to as a primary scraper, a secondary scraper and a tertiary scraper respectively. At least one of the cleaners may be a different form of known cleaner, such as a rotating brush instead of a scraper. Any scrapers may be of know types such as rigid scrapers mounted to scraper beams by flexible bushings as shown in Figure 2, or flexible scrapers such as polyurethane scrapers.

[0086] Although the fluid in the description is preferably hydraulic liquid, it may be water or another liquid or it may be a gas such as compressed air or nitrogen.

[0087] By withdrawing the scraper blades away from the conveyor belt when not required and reapplying them when desired, many benefits can be provided. For example, excessive heating of scraper blades can be prevented as leaving them in contact with the conveyor without material to be cleared (which material also takes away heat), can prevent heat build-up of blades unnecessarily energised against an empty conveyor belt. Blade wear can be optimised by only applying the blades when required. Similarly belt wear can be reduced by preventing needless energising of scraper blades into the conveyor belt. When the belt is stopped, the blades are withdrawn by the present invention, so are not left energised into the belt. Possibly hot blades being energised against a recently empty, now stationary belt, can damage the belt. Similarly energising the scraper blades into the belt when the conveyor is running in a reverse direction can damage the belt and/or the scraper blades.

[0088] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

[0089] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

[0090] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.