BACKGROUND OF THE INVENTION

[0001] The invention relates to equipment for binding dust in rock drilling by means of a drilling apparatus, the drilling apparatus comprising a rock drill for drilling a hole, means for supplying flushing air into a drilling hole, means for separating dust formed during drilling from the flushing air, and means for supplying liquid into rock dust formed during drilling in order to bind it, whereby the equipment comprises at least one control member for controlling the amount of liquid to be supplied into the rock dust.

[0002] To bind rock dust formed during rock drilling, it is today very common to employ liquid mist flushing, wherein air and liquid, typically water, are supplied into a drilling hole as mist-like droplets. Liquid mist flushing is typically applied mainly in overground drilling.

[0003] The amount of the liquid used in liquid mist flushing, such as water or solutions containing different additives, is very precise, because too small an amount of liquid does not bind rock dust sufficiently and too large an amount of liquid may block up the dust removal equipment.

[0004] At present, the water amount is controlled manually by a valve in the control cabin of the drilling apparatus. This requires that a liquid supply hose must be led through the control cabin, which complicates the installation and increases the amount of necessary hoses. Pressure variations of the process also cause continuous changes in liquid flow rates, wherefore the operator must constantly monitor the flow rate and fix it to an appropriate level. In theory, pressure-compensated flow control valves could be used, but, for example due to the corrosive effect of water, flow control valves suitable for water are expensive and also very sensitive even to a small amount of dirt. Thus, in practice they are unable to provide the desired control accuracy.

BRIEF DESCRIPTION OF THE INVENTION

[0005] It is an object of the present invention to provide a method and equipment, by which the supply volume of water in connection with liquid mist flushing can be controlled easily and reliably.

[0006] Characteristic of the equipment according to the invention is that the control member comprises a plurality of parallel on/off type control valves, which can, one or more at a time, be switched open and/or closed si- multaneously and that, by switching different valves open separately or simultaneously as different combinations, different liquid flow rates are achieved.

[0007] The essential idea of the invention is that the amount of liquid, such as water, used in liquid mist flushing or otherwise in dust binding is controlled by a digital volume flow control unit comprising a plurality of parallel on/off valves, which can be controlled, one or more at a time, to an open or closed position to achieve the desired amount of liquid. Further, an idea of an embodiment of the invention is that the sizing of the valves is binary-coded, which means that the flow rates of the open valves are always substantially twice as high as in the preceding valve with a smaller flow rate.

[0008] According to an embodiment of the invention, the pressure difference between the input side and output side of the valves is measured and the valves are controlled according to the pressure difference so that the flow rate remains substantially constant. According to another embodiment of the invention, such control based on pressure compensation is performed automatically.

[0009] The invention provides the advantage that the flow rate of liquid, such as water, can be adjusted to a desired level with a sufficient accuracy merely by selecting a suitable combination of open valves. Another advantage is that the control may be performed fully automatically, and the operator responsible for the drilling need not separately concentrate on controlling the water amount. Yet another advantage of the invention is that, in order to supply liquid and perform the controlling, hoses for carrying the liquid need not be led through the control cabin but may be laid along the shortest route, since the valves are controlled electrically. The invention also provides the advantage that the valves used in such a solution are simple valves in an open or closed position, whereby they are neither vulnerable to defects nor sensitive to dirt. Compared to proportional valves, the invention provides the advantage that a failure of one single valve does not interrupt the drilling, though, thereafter, the supply of liquid is not as accurate as desired. In addition, the valves of the invention are inexpensive and the pressure compensation does not require complex measuring devices but can be performed by a simple conventional pressure difference measurement. BRIEF DESCRIPTION OF THE FIGURES

[0010] The invention will be explained in greater detail in the attached drawings, in which

Figure 1 schematically shows a drilling apparatus employing liquid mist flushing,

Figure 2 schematically shows a simple connection applicable in liquid mist flushing and dust removal,

Figures 3a to 3c schematically show a digitally controlled and binary-coded valve connection used in the invention, and its operation as a schematic table,

Figures 4a and 4b schematically show the real characteristic curve of the program carried out with valves, and a compensated characteristic curve of the valve packet carried out in a corresponding manner,

Figure 5 shows how pressure compensation is used for controlling the flow rate of water,

Figure 6 schematically shows a connection according to the embodiment of the invention, and

Figure 7 schematically shows a further connection according to the embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Figure 1 shows a rock drilling apparatus, which comprises, in a manner known per se, a carrier 1 , to which a boom 2 is arranged. A feed beam 3 with a rock drilling machine is provided at the end of the boom 2. The rock drilling apparatus also typically comprises a non-shown compressor for supplying pressurized air through a drill rod into a drilling hole and, when the air exits through the circular space between the drill rod and the drilled hole, it brings drill cuttings, i.e. rock dust and coarser material, with it from the hole. These apparatuses and the operation thereof are known per se in the field and obvious to a person skilled in the art, wherefore they need not be explained in greater detail herein. At the front end of the feed beam there is a suction nozzle 4, which is arranged around the drill rod so that, during drilling, it can be pushed around the hole to be drilled tightly against the soil. A suction hose 5 leads from the suction nozzle 4 to a pre-separator 6, where the coarse material is separated from the dust. From the pre-separator 6, the dust and the suction air proceed along a hose 7 into a dust separator 8, which is usually located at the rear part of the rock drilling equipment. In the dust separator, the dust is separated from the suction air and it accumulates in the dust separator 8. The accumulated dust is removed from the dust separator 8 at suitable intervals by passing the accumulated dust to the ground. The operation of the dust separator is explained in detail in connection with Figure 2.

[0012] Figure 2 schematically shows a diagram of dust separation equipment suitable for implementing the invention. Such dust separation equipment and dust separators are generally known per se, wherefore they need not be explained in greater detail in this context. The figure shows a flushing air duct 9 with a flushing valve 10. Air supplied by a compressor 11 along the flushing air duct 9, controlled by the flushing valve 10, is supplied through a drill rod 12 into a drilling hole 13 in order to remove the drill cuttings formed during drilling. Simultaneously, liquid inside a liquid container 14 is supplied through a channel 15, controlled by a valve 16, into the flushing air. The amount of liquid is controlled by a separate controller 17, whereby the liquid is mixed into the flushing air preferably in a mist-like form. The liquid carried by the flushing air moistens and thus binds the majority of the formed rock dust. The flushing air that has exited the drilling hole is sucked by a sucking fan 8a through the hose 5 into the pre-separator 6 and further through a hose 7 into the dust separator 8. In the pre-separator of Figure 1 , which is not as such necessary to the invention, a coarser material is separated from the flushing air and the dust-like material proceeds with the air further to the dust separator 8. In the dust separator 8 the dust remains in filters 8b while the air flows through the filters 8b and out of the dust separator substantially in a dust-free manner. Dust is removed in batches from the dust separator 8 at suitable intervals. To remove dust, the dust separator 8 is at its upper part connected with the pressure air duct 9 via a valve 18. When the drilling has been stopped and no flushing air need be sucked into the dust separator, an impulse of pressurized air is supplied to the dust separator 8 by means of the valve 18, after which the dust is removed from the filter and falls to the bottom part of the dust separator. By means of a controller 19, liquid is supplied from the chamber 14 via a channel 20 to the bottom part of the dust separator 8 and, in a mist-like form or as very small droplets, through nozzles 21 or the like before and/or during the impulse of pressurized air. To supply the liquid, a solution shown in the figure, for instance, can be used, whereby pressurized air is supplied along a channel 22 to the upper part of the liquid container through a valve 23 in such a man- ner that the liquid is pushed out of the container 14 under the pressure of the pressurized air. If necessary, liquid can be supplied both before and during the impulse of pressurized air, i.e. substantially and immediately before the dust removal and/or during the entire process of dust removal. As a result of the liquid supplied to the bottom part of the dust separator, dust that falls from the filters 8a moistens so much that when it falls out of the bottom part of the dust separator, it consists of substance that does not dust. The principle and operation of the controllers 17 and 19 are explained in closer detail in connection with Figures 3a to 3c as well as 4a and 4b.

[0013] To control the supply of liquid and the dust removal, it is possible to use a separate control unit 24, which is connected to control said valves as well as the compressor and the sucking fan of the dust separator. The control unit is most preferably connected by means of a control channel 25 to the equipment known per se for controlling the actual drilling in such a manner that it receives through the control channel 25 a control signal, according to which the control unit 24 directs, if necessary, the liquid supply either into the flushing air or to the dust separator for the time of dust removal. The control unit 24 may be connected to control the equipment in various ways. Thus, the control may be based on, for example, switching the rock drilling machine to a return motion or to some other signal or indicator indicating a certain drilling stage. The control unit 24 may also form a part of the equipment controlling the actual drilling and act as a unit provided specifically for this purpose, or it may be implemented by software, if the equipment controlling the actual drilling is a computer or a similar device. If desired, pressurized air may be supplied to the bottom part of the dust separator 8 through a valve 26, though this is not necessary.

[0014] Figures 3a and 3c schematically show the structure of a digitally controlled controller, wherein a plurality of parallel on/off valves V1 to V4 with different flow rates are used. In theory, the flow rates could be selected in many different ways, but preferably the ports of different valves are of different sizes, wherefore there is choking effect to water flow, schematically shown by chokes K1 to K4, is different at each valve. At its simplest, this can be done by selecting the ports or choking of the valves in such a manner that the flow rates Q of liquid passing through the valves with the same pressure difference over the valve are always twice as high as the previous, lower flow rate of water, i.e. 1xQ, 2xQ, 4xQ and 8xQ, as shown by the figure. In practice, it is not absolutely possible to manufacture valves thus proportioned and particularly to have them readily available on the market, wherefore, to maintain the accuracy, the control may be performed as shown in Figures 4a and 4b.

[0015] Figure 3b shows schematically a connection of four parallel valves according to Figure 3a, depicted as one valve. Here, the diagram shows a stepped control valve, in which the control is performed by a four-figure binary code (n = 4).

[0016] Figure 3c shows schematically flow rates of the valve according to Figure 3a, controlled by a four-bit binary code. The liquid flow rate through the valve V1 is 1 x Q, through the valve V2 2 x Q, through the valve V3 4 x Q, and through the valve V4 8 x Q. When the binary code is 0, no liquid flows through any valve. When the binary code is 1000, only the valve V1 is open and the liquid flow rate is Q. With the binary value 0100, only the valve V2 is open and the flow rate is then 2 x Q. With the binary value 3, i.e. 1100, both the valve V1 and V2 are open and the flow rate is 3 x Q. Thus, by changing the binary code, the binary code 1111 , i.e. 15, produces the maximum flow rate of 15 x Q. Thus, the liquid flow rate can in theory be controlled in exactly 15 steps when four parallel on/off valves are used, and the amounts of liquid flowing through these valves with the same pressure difference are proportioned in such a manner that the liquid flow rate through the valve is always exactly twice as high as the liquid flow rate through the immediately smaller valve.

[0017] With this digital volume flow control system, it is possible to avoid weaknesses caused by pressure variations and impurities of known proportional valves while achieving sufficient control accuracy. The control accuracy may be selected simply according to the need by mounting a sufficient number of on/off valves in parallel so that the flow rate of the smallest valve corresponds to the smallest required flow rate or change in the flow rate and the combined flow rate of all valves corresponds to the desired maximum flow rate. Furthermore, if one of the valves becomes damaged or its flow channel is blocked, the flow rate of water can be adjusted, though the control accuracy and the maximum flow rate will be reduced. Also, compared to reliable proportional valves of good quality, the purchase price of such valves is quite low and it is rather cheap to replace a faulty valve by a new one that is working.

[0018] Figures 4a and 4b show the real flow rates of a controller provided with a packet of several (i.e. 7) valves, and a usable working charac- teristic curve provided by binary code correction. Figure 4a shows flow rates of the controller when it is controlled logically with all successive binary values 0 to 127.

[0019] Figure 4a shows clear deviations in the flow rates at control signals of the multiples of 8 bits and, more significantly, 32 bits. At these points, the flow rate of water dropped or remained the same at the successive values, irrespective of the increase in the binary value. This is because the proportions of the valves do not absolutely correspond to the binary code but differ from one another to some extent. In this experiment, this is due to the fact that the properties of the flow channels of commercially supplied valves, i.e. the choking effect they provided, deviated from the binary values of the standard valves to some extent.

[0020] Figure 4b shows the final flow rate curve, where the binary values reducing the flow rate have been deleted from the control of the controller, as a result of which a controller with approximately 95 steps is achieved, in which the flow rate follows the input binary values almost linearly.

[0021] In practice, the control is performed, for instance, by compiling the acceptable binary values into a table, from which the control system then systematically takes the necessary binary code proportional to the flow rate in order to control the valves in the controller.

[0022] Since the pressure difference over the controller 17 and/or 19 does by no means remain constant, but changes to some extent, the volume flow of the supplied water could vary according to the variations in the pressure difference, which is not necessarily acceptable. This can be solved by measuring the pressure difference between the input side and output side of the controller 17 and/or 19. The controller can be calibrated by measuring, by means of all available binary codes and correspondingly between zero and maximum flows, the flow rates of water in the entire area with different pressure difference values. It is then possible, for instance, to create a plurality of tables defining the flow rate of water for each binary code with a different pressure difference value. In the automatic control, the pressure difference measurement may be employed to control the operation of the controller 17 and/or 19 in such a manner that, as the pressure changes, the control unit automatically selects the table closest to each pressure value and, from there, a binary code corresponding to the pre-set flow rate and uses the binary code to control the valves at the particular moment. This control connection is shown sche- matically and by way of example in connection with the controller 17 in Figure 5, wherein a pressure gauge Mp is connected to measure pressure p1 at the input side of the controller 17 and pressure p2 at its output side so that a pressure difference Δp over the controller 17 is achieved. After this, the pressure difference value Δp can be used by the control unit 24, and the control unit 24 switches a digital binary code for the controller to open and close valves according to the pressure difference value in such a manner that, controlled by the control unit 24, the value of the flow rate of the fed water remains as desired with a sufficient accuracy. Alternatively, on the basis of the pressure difference measurement it is possible to correct the flow rate value corresponding to each binary code according to, for instance, a predefined formula, in which case it is not necessary to use more than one table. Likewise, the pressure difference measurement may be applied in such a manner that a few tables are used and one or more intermediate values are interpolated between the table values on the basis of the pressure difference measurement for example linearly or according to a suitable curve. This may also be performed similarly in connection with the controller 19.

[0023] Figure 6 shows schematically another connection according to the embodiment of the invention. In other respects, this connection corresponds to that of Figure 2 and the corresponding parts are not explained anymore. This embodiment comprises an additional three-position valve 27, which may also be a conventional three-way valve, by which the channel 15 in connection with the controllers 17 and 19 and the liquid container 14 may be closed and the channel that ends at the controllers 17 and 19 may be switched open to the atmosphere. Thus, pressurized air can be supplied from the compressor through the controllers 17 and 19 against the flow direction of liquid normally flowing through them, as a result of which the valves are cleaned from dirt accumulated therein and the operation of the valves remains reliable a longer time.

[0024] Figure 7 shows schematically yet another connection according to the embodiment of the invention. This connection also corresponds to the connection of Figure 2 and the corresponding parts are not explained anymore herein. In this embodiment, a separate pressure air duct 22 leading to the liquid container 14 and the associated components have been omitted. Supply of air to the container 14 is in this case realized by supplying the air used for flushing the controller through the controller 17 along the channel 15 into the container 14, whereby the volume of the container 14 is selected so that the amount of air supplied thereto is sufficient to supply liquid during at least one drilling period. During the drilling stages, preferably while the controller 17 and/or 19 is/are cleaned, as much air is supplied to the container 14 as is needed for supplying water or other liquid during the next drilling stage. With this solution, the number of fewer pipes, hoses and components is smaller.

[0025] The invention is described above in the description and drawings by way of example only and it is by no means restricted thereto. As described in connection with the controller 17, the amount of liquid to be supplied into the dust separator 8 can be accurately controlled by means of the controller 19. The structure and operation of the controller 19 correspond to those of the controller 17 described above and, similarly, pressure difference measurement may be employed there to improve the control accuracy and provide a simpler control.