The present invention relates to long wall hydraulic supply systems, to control units for use with the same, and to methods of operating the same.

Powered roof supports are electro-hydraulic structures used for supporting the roof of a mine, e.g. a long wall coal mine, in the region above a cutting machine working at the face. As the cutting machine moves across the face the powered roof supports are called upon to deal with changes in roof load, and also to advance themselves with the cutting machine. The roof supporting and advancing operations are driven by hydraulic pressure provided by a remote hydraulic pump station, located away from the face and typically comprising a plurality of pumps. Typically a mine will comprise of a long wall hydraulic system that includes the pump station and a large number of powered roof supports, each powered roof support working as if independent of the others to perform load supporting and advancing operations across the face. The pump station is arranged to supply hydraulic pressure to all the powered roof supports.

It is desirable to maintain a set pressure in the hydraulic system, and the pump station therefore typically comprises a pressure sensor. The pressure sensor at the pump station is used to control the pump station to raise pressure in response to a sensed pressure change at the pump station. However, each pump element at the pump station is constrained to operate at a fixed pumping capacity, and controlling the operation of the pump station to give a desired supply of fluid volume and therefore maintain a set pressure at the powered roof support system according to its varying operational demands is difficult.

GB 2 329 429, considered as the closest prior art, describes a roof support arrangement having a roof support leg, means a valve connected to a hydraulic fluid supply for controlling the flow of hydraulic fluid into the roof support leg, actuator means for opening and closing the valve according to a control signal, means for determining the pressure on the leg and for transmitting a signal dependent on the pressure to a control means, which control means generates a control signal according to the pressure determined by the pressure determining means, which control signal actuates the actuator means to open a valve.

It is an aim of example embodiments of the present invention to address at least one disadvantage of the prior art, whether identified herein or otherwise.

In a first aspect, the present invention provides a long wall hydraulic supply system comprising: a pump station operatively coupled to a remote powered roof support to supply hydraulic fluid thereto via a hydraulic line; a remote pressure sensor located remote from the pump station in the hydraulic line; and a control unit, wherein the control unit is operatively coupled to the remote pressure sensor and to the pump station, and characterised in that the control unit is arranged to control the pump station to supply hydraulic fluid to the powered roof support via the hydraulic line in response to a remote pressure signal received from the remote pressure sensor.

Suitably, the long wall hydraulic system comprises a plurality of powered roof supports. Suitably, the powered roof supports are in use arranged between a main gate end and a tail gate end of a face. Suitably, the remote pressure sensor is located local to the powered roof support. Suitably, the remote pressure sensor is located local to the powered roof supports. Suitably, the remote pressure sensor is located proximate to the tail gate end of the face. Suitably, the remote pressure sensor is located centrally between the main gate end of the face and the tail gate end of the face. Suitably, the remote pressure sensor is located proximate to the main gate end of the face. Suitably, the remote pressure sensor is located at the powered roof support.

Suitably, the control unit comprises a set point pressure input unit, arranged to receive and store a set pressure that the pump station is intended to provide. Suitably, the control unit is arranged to cause the pump station to supply a varying volume of hydraulic fluid to the powered roof supports according to variation in the remote pressure signals by controlling operation of one or more pumps in the pump station. Suitably, the control unit comprises part of a negative feedback loop. Suitably, the control unit comprises part of a negative feedback loop that aims to maintain the set point pressure at the remote pressure sensor by controlling operation of the pump station in response to variation in the remote pressure signal.

Suitably, the control unit is arranged to control a plurality of pumping elements within the pump station. Suitably, the pump station comprises one or more positive displacement pumping elements. Suitably, one or more of the pumping elements in the pump station are driven by a variable speed drive. Suitably, the control unit is operatively coupled to a variable speed drive to control operation of a positive displacement pumping element to supply a varying volume of hydraulic fluid to the powered roof supports in response to the variation in the remote pressure signal. Suitably, the control unit is arranged first to cause one or more primary pumping elements to be driven, and then secondly to cause one or more additional pumping elements to be driven in addition, in response to variation in the remote pressure signal. Suitably, the primary pumping elements are arranged in a group including a master pump and a secondary pump. Suitably, the primary pumping elements are arranged in a group including a master pump, a secondary pump and a tertiary pump. Suitably, the pumps in the group of primary pumping elements are driven by variable speed drives. Suitably, the one or more additional pumping elements are driven by a direct on line drive.

Suitably, the control unit is operatively coupled to the remote pressure sensor and to the pump station by a wired, or wireless connection.

Suitably, the control unit comprises a first input unit arranged to receive a set point pressure. Suitably, the control unit comprises a second input unit arranged to receive a remote pressure signal. Suitably, the control unit comprises a subtraction operator to determine a difference between the set point pressure and a remote pressure signal. Suitably, the control unit comprises a control unit arranged to store information relating the pressure difference to characteristics of the pump station. Suitably, the control unit comprises an output interface for coupling to the pump station.

In a further aspect, the present invention provides a method of operating a long wall hydraulic supply system comprising: a pump station operatively coupled to a remote powered roof support to supply hydraulic fluid thereto via a hydraulic line; a remote pressure sensor located remote from the pump station in the hydraulic line; and a control unit, the method comprising: receiving a pressure signal from the remote pressure sensor; and characterised by the step of controlling the pump station to supply hydraulic fluid to the powered roof support in response to the pressure signal received from the remote pressure sensor.

Suitably, the method comprises receiving and storing a set point pressure. Suitably, the method comprises determining a difference between the set point pressure and the pressure signal received from the remote pressure sensor. Suitably, the method comprises supplying a control signal to the pump station to cause the pump station to match the pressure signal received from the remote pressure sensor with the set point pressure. Suitably, the method comprises a feedback control method. Suitably, the method comprises operating one or more primary pumping elements in response to sensed variation in the demand for hydraulic fluid, and then according to the pressure signal received from the remote pressure sensor additionally operating one or more additional pumping elements. Suitably, the method comprises operating one or more of the primary pumping elements using a variable speed drive. Suitably, the method comprises operating one or more of the additional pumping elements using a direct on line drive.

In a further aspect, the present invention provides a computer program product, recorded on a machine-readable data carrier, and containing instructions arranged, when loaded on a suitable computing platform to cause the system according to the first aspect to perform a method according to the third aspect of the present invention.

According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

• Figure 1 shows a schematic illustration of a long wall hydraulic supply system according to an example embodiment of the present invention;
• Figure 2 shows a schematic illustration of a control unit for a long wall hydraulic supply system according to an example embodiment of the present invention;
• Figure 3 shows a schematic flow diagram illustrating a method of maintaining a set pressure to operate a powered roof support system, the method according to an example embodiment of the present invention; and
• Figure 4 shows a group of machine-readable carriers containing instruction thereon, each machine-readable carrier in the group according to an example embodiment of the present invention.

Example embodiments of the present invention will be described in detail with reference to the accompanying drawings. Referring now to Figure 1 there is shown a long wall hydraulic supply system 100 comprising: a pump station 10 operatively coupled to a set of remote powered roof supports 20 to supply hydraulic pressure thereto via a hydraulic line 30. The powered roof supports comprise a number of independently actuatable powered roof support elements, all coupled to the hydraulic line 30. The pump station 10 comprises a pump 12 and a drive 14 to actuate the pump 12. A remote pressure sensor 40 is located in the hydraulic line 30 at a position local to the powered roof supports 20 and remote from the pump station 10. A control unit 50 is operatively coupled to the remote pressure sensor 40 and to the pump station 10, and is arranged to control the pump station 10 to supply hydraulic pressure to the powered roof supports 20 via the hydraulic line 30 in response to a remote pressure signal received from the remote pressure sensor 40. In this document, "remote" means away from the pump station, and includes locations at or proximate to the powered roof supports 20.

The long wall hydraulic supply system 100 operates with feedback control, such that the control unit 50 compares the remote pressure signal with a set point pressure, and controls the pump station 10 to try to maintain the set point pressure at the powered roof support 20 despite changes in pressure caused by changes in loading of and operation of the powered roof supports 20. The feedback control operation of the control unit 50 is illustrated schematically by the subtraction operator 52 shown in the control unit 50. The set point pressure is determined according to the load rating of the powered roof supports 20, which itself is a dependent on the characteristics of the installation in which the powered roof support system is to operate. The set point pressure is received and stored at a set point pressure input unit of the control unit 50, for example in response to user input.

In this way the control unit 50 is able to accurately match the output of the pump station 10 to variations in requirement for hydraulic fluid volume of the powered roof supports 20. Providing a remote sensor 40 at the powered roof supports 20 enables the control unit 50 to provide an improved response over systems that measure the pressure at a point close to the pump station. The feedback from the pressure sensor to the pump station is not distorted by factors such as losses in a long run of hydraulic hose between the pump station and the powered roof support, or a mis-match in the capacity of the hydraulic hose and the capacity of the pump station for fluid delivery. A wired or wireless connection between the remote pressure sensor and the control unit, such as a connection 60 shown in Figure 1, can be made more robust and accurate than operating the control unit solely based on sensed pressure at the pump station in combination with unknown and possibly variable characteristics of the hydraulic coupling between the pump station and the powered roof support.

Further improvements are provided by increasing flexibility of the pump station 10 to respond in stages according to variable demand for hydraulic fluid volume supply. The pump 12 and drive 14 in this example embodiment are provided as multiple pumping and driving elements. The pumping elements are positive displacement pumps driven by a plurality of drives. The control unit 50 is arranged in such example embodiments to control the plurality of pumping elements within the pump station 10. In example embodiments of the present invention one or more of the pumping elements in the pump station are driven by a variable speed drives. The control unit 50 is arranged first to cause the primary pumping element to be driven, for example by a variable speed drive to respond quickly and efficiently to a change in demand according to the remote pressure signal, and then secondly to cause further pumping elements to be simultaneously driven with and in addition to the primary pump, for example by a direct on line drive to provide a base pumping capacity. This allows greater variability of supply, while maintaining the ability to achieve fine control. Using this type of scheme allows the pumps to operate away from their maximum capacity rating for more of the time, despite variations in demand. The pump station 10 suitably also includes a local pressure sensor (not shown) as a safety feature to prevent over-pressuring the system.

Figure 2 shows a schematic illustration of the control unit 50 for a long wall hydraulic supply system according to an example embodiment of the present invention. The control unit 50 comprises a first input unit 501 arranged to receive a set point pressure and a second input unit 502 arranged to receive a remote pressure signal. The set point pressure and remote pressure signal are compared in the subtraction operator 52, with the results of the subtraction passed to a controller54. The controller 54 stores information relating the pressure difference to characteristics of the pump station 10, in terms of its pump(s) 12 and drive(s) 14, and provides an output interface 503 for controlling the drive(s) 14 to operate the pump(s) 12.

Figure 3 shows a schematic flow diagram illustrating a method of operating a long wall hydraulic supply system according to an example embodiment of the present invention. At step S101 the controller is arranged to receive and store a set point pressure. The set point pressure may be provided at a user interface such as a touch screen, control panel or the like. At step S102 the remote pressure sensor information is received at the controller. The controller then determines the difference between the set point pressure and the remote pressure signal to determine a pressure error at step S103. The controller then transforms the pressure error into a control signal for the pump station, before supplying the control signal to the pump station in steps S104 and S105 respectively.

The method of Figure 3 may be described as machine readable program instructions provided on a data carrier 200 such as the example data carriers shown in Figure 4. The carriers 200 comprise a machine-readable optical disc, a Universal Serial Bus (USB) memory stick, and an application specific solid state memory device.

By enabling more accurate control and increasing pump station efficiency as above, it is possible to improve the availability of hydraulic fluid at the powered roof supports, which in turn enables increased speed of response and therefore operation. Increased speed of operation of powered roof supports is a major advantage in mining operations.

The present invention will be understood readily by reference to the above description of example embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the example embodiments described above. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art. The present invention is defined by the statements of aspects of the invention in the summary of invention section above, and with reference to any appended claims.

The example embodiments are described above with reference to flowchart illustrations, methods, and computer program products. It is to be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart block or blocks.

These computer program instructions may also be stored in a computer usable or computer-readable memory or data carrier that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer usable or computer-readable memory or data carrier produce an article of manufacture including instruction means that implement the function specified in the flowchart block or blocks.

The computer program instructions may also be loaded into a computer or other programmable data processing apparatus to cause a series of operational steps to be performed in the computer or other programmable apparatus to produce a computer implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.

And each block of the flowchart illustrations may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved.

The terms "module" or "unit", as used herein, means, but is not limited to, a software or hardware component, such as a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC), which performs certain tasks. A module or unit may advantageously be configured to reside in an addressable storage medium and configured to execute on one or more processors. Thus, a module or unit may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionality provided for in the components, units and modules may be combined into fewer components, units and modules or further separated into additional components, units and modules.

Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.