ARRANGEMENT FOR CONTROLLING PRESSURE-FLUID-OPERATED DRILLING EQUIPMENT

[0001] The invention relates to an arrangement for controlling pres- sure-fluid-operatecl drilling equipment, the arrangement comprising a rock drill equipped with a percussion device and a rotating motor, a feed motor for feeding the rock drill with a feed motion in a direction of drilling and, correspondingly, for returning the same, at least one pressure fluid pump and pressure fluid channels connected thereto for feeding pressure fluid to the percussion device, to the rotating motor and, similarly, to the feed motor, at least one pressure fluid return channel leading to a pressure fluid reservoir for returning the pressure fluid to the pressure fluid reservoir, valves for controlling a flow of pressure fluid to the percussion device and to the rotating motor, as well as a feed control valve for conveying the flow of pressure fluid to the feed motor, a pressure compensator arranged in a pressure fluid channel leading to the feed motor and connected with a first pressure sensing channel from a feed pressure channel received by the feed control valve and a second pressure sensing channel connected with a feed channel from the feed control valve to the feed motor, a pressure limit having a predetermined pressure limit value and being connected with the pressure fluid feed channel of the feed motor and the second pressure sensing channel leading to the pressure compensator as well as with the pressure fluid reservoir, wherein when the pressure of the pressure fluid in the feed channel, due to drilling conditions, tends to exceed the limit value for the pressure limit, the pressure limit allows pressure fluid to flow therethrough, thus controlling the pressure compensator such that it chokes the flow of pressure fluid to the feed motor and thus keeps the pressure in the feed channel substantially at a value set by the pressure limit.

[0002] In rock drilling, a major problem arises from the fact that the properties of rocks to be drilled may change quite rapidly, so that controlling the drilling equipment is not always suitable for the drilling. In sedimentary rocks, for instance, the structure and hardness of the rock material in different layers may vary from one extreme to another, from a hard rock type to almost a soft, sandy type. When a hole is being drilled into such a rock, e.g. at a

propagation speed of 4 m/min, the conditions change quite rapidly. In such circumstances, it is impossible to manually control the drilling process, although attempts have been made at using various control devices in different drilling equipment.

[0003] An object of the present invention is to provide an arrangement for controlling drilling equipment so as to enable a drilling process including all its stages to be implemented easily and efficiently as well as to enable the feed pressure of a feed motor for a rock drill to be automatically controlled to suit the hardness of rock and thus the feed rate. The arrangement according to the invention is characterized in that a pressure loss generated by the pressure fluid flowing through the pressure limit is proportional to a volume of flow of pressure fluid flowing through the pressure limit such that when the flow of pressure fluid through the pressure limit increases, the pressure loss increases proportionally to the volume of flow, and that a pressure difference acting over the pressure limit is a sum of the limit value set at the pressure limit and the pressure loss generated by the flow of pressure fluid, whereby a decrease in the flow of pressure fluid through the feed motor causes the flow of pressure fluid to increase through the pressure limit, the result being that the pressure difference acting over the pressure limit increases and controls the pressure compensator such that the pressure in the feed channel increases and, correspondingly, the increase in the flow of pressure fluid through the feed motor causes a decrease in the flow of pressure fluid through the pressure limit, the result being that the pressure difference acting over the pressure limit decreases and controls the pressure compensator such that the pressure in the feed channel decreases.

[0004] An idea of the invention is that the pressure value of the pressure limit depends on the volume of pressure fluid flowing therethrough, such that when the flow increases, the pressure value of the pressure limit increases, so that when feed drops when the drilling conditions change, i.e. mainly when the hardness of rock increases, whereby the flow of pressure fluid passing through the feed motor decreases, the flow through the pressure limit increases and produces an increase in the pressure in the feed channel of the feed motor.

[0005] An advantage of the arrangement according to the invention is that when the properties of a rock to be drilled in changing conditions change, the arrangement automatically controls the pressure of the feed inversely proportionally to the feed rate or, if the pressure drops below a limit value, keeps the feed rate at a set maximum value. A further advantage of the invention is that when pressure control is used, it may also be used for controlling the pressure of the pressure fluid to be fed to the percussion device, and thus, correspondingly, the striking power.

[0006] The invention is described in closer detail in the accompanying drawings, in which

[0007] Figure 1 schematically shows an embodiment of an arrangement according to the invention, and

[0008] Figure 2 schematically shows another embodiment of the arrangement according to the invention.

[0009] Figure 1 schematically shows a hydraulic connection for controlling drilling equipment. This connection comprises a pressure fluid pump 1 , preferably a pressure-controlled volume flow pump. It further comprises a percussion device 2 and a feed motor 3 to be operated by pressure fluid fed by the pressure fluid pump 1. Depending on different implementations, the feed motor 3 may be either a hydraulic motor or a cylinder, but in the present application and claims, both are called a feed motor. In order to control the operation of the feed motor, a pressure relief valve 5 is connected to a pressure fluid channel 4 provided from the pressure fluid pump 1 for decreasing the pressure of the pressure fluid to a pressure level suitable for the operation of control valves provided in the connection. From the pressure relief valve 5, a control pressure channel 6 is led to a control valve 7 to control feed of the feed motor 3. The control valve 7 is a pressure control valve known per se, whose position, and thus the pressure of pressure fluid being discharged, is controlled by a control arm 7a. From its middle, i.e. neutral, position, the control arm 7a may be controlled into both directions as indicated by arrow A ₁ which enables both forward feed and return motion to be controlled by the same control device. Extending from the control valve 7, two feed control channels 8a and 8b are provided that are connected to control a feed control valve 9. The feed control vaϊve 9 is a two-way proportional valve, the flow of pressure fluid passing therethrough being proportional to the control pressures affecting the same. The channel 4 provided from the pressure fluid pump 1 is further connected to a

pressure compensator 10 to control the pressure of the pressure fluid coming from the pressure fluid pump. The pressure compensator 10 is connected to the feed control valve 9 by a feed pressure channel 11, via which the pressure fluid flows to the feed motor 3, controlied by the feed control valve 9. A pressure sensing channel 10a is also connected from the feed pressure channel 11 to affect the pressure compensator 10.

[0010] From the feed control valve 9, a return channel 13 is further provided to a pressure fluid reservoir 12 such that a return flow of pressure fluid from the feed motor 3 is conveyed to the pressure fluid reservoir via the return channel 13. From the feed motor 3, a feed channel 14a and a return channel 14b are further connected to the feed control valve 9 to enable the feed motor 3 to operate in a desired direction, depending on the control by the feed control valve 9. When the feed control valve 7 is used for controlling the pressure of the pressure fluid into the channel 8a, the pressure fluid flows to the feed motor 3 via the feed channel 14a, and it flows back via the return channel 14b. Consequently, the feed motor 3 feeds the rock drill, and thus the drill rod, forward. Similarly, when the control arm 7a is rotated in another direction, pressure is generated in the control pressure channel δb, the result being that the spool of the feed control valve 9 moves into a position wherein pressure fluid is fed to the feed motor 3 via the return channel 14b such that it flows back via the feed channel 14a. In this situation, the feed motor 3 generates a return motion. The rate of motion produced by the feed motor 3 is proportional to the pressure value produced in the channels 8a and 8b, respectively, so that by changing the position of the control arm 7a, it is possible to produce a rate of motion of a desired magnitude.

[0011] From the pressure fluid pump 1, the high-pressure pressure fluid is further conveyed via the channel 4 to an impact valve 15, by means of which, via a channel 16, it may be connected to flow to the percussion device 2. From the percussion device 2, in turn, a separate pressure fluid return channel 17 is provided to the pressure fluid reservoir 12. The impact valve 15 is controlled by a control channel 18 from the control valve 7, so that when feed is switched on, the control pressure is at the same time switched on via the channel 18 to the impact valve 15, connecting the pressure fluid from the channel 4 to the percussion device 2. Naturally, the impact valve 15 may also be controlled in a manner known per se by an impact control valve separate

from the control valve 7 or by a mechanical arm or in a similar manner known per se.

[0012] In order to control the pressure of the pressure fluid coming from the pressure fluid pump 1, a control pressure channel 19 is connected from the pressure channel 16 to a shuttle valve 20. From the shuttle valve 20, a control channel 21 is further provided to the pressure fluid pump 1 to its pressure control circuit.

[0013] From the feed channel 14a and the return channel 14b, load sensing channels 22a and 22b are further provided via chokes 23a and 23b, respectively, to a shuttle valve 24. The shuttle valve 24, in turn, is connected by a channel 25 to the shuttle valve 20, by a second pressure sensing channel 10b to the pressure compensator 10, and by a branch 25a to a pressure limit 26. The pressure compensator 10 is thus connected such that it is affected by a pressure difference acting over the feed control valve via the pressure sensing channels 10a and 10b and, during drilling and forward feed, the pressure compensator keeps this pressure difference constant, in which case the flow of pressure fluid through the feed control valve 9 similarly stays constant.

[0014] The pressure limit 26, in turn, is connected by a channel 27 to the pressure fluid reservoir 12. From the feed channel 14a of the feed motor, which has the pressure of the pressure fluid during forward feed, a channel 29 may also be connected to the pressure limit 26 via an additional, either a fixed or a controllable choke 28 and via the branch 25a of the channel 25 provided to the pressure limit 26. This is to ensure the volume of flow of pressure fluid flowing through the pressure limit 26 in a situation wherein the volume of flow conveyed through the load sensing channel 22a is not as such sufficient to produce a desired change in the pressure in tie channel 25.

[0015] Furthermore, the arrangement usually comprises a rotating motor 30 for rotating the drill rod during drilling, and a control valve 31 for controlling the rotating motor both in a rotating direction necessary during normal drilling and in an opposite direction for decoupling the drill rod. The rotating motor 30 receives pressure fluid from a separate pressure fluid pump 32 along a channel 33 and, similarly, the pressure fluid is discharged to the pressure fluid reservoir along a channel 34. Alternatively, the pressure fluid may be fed to the rotating motor 30 from a common pressure fluid pump 1. The above is not, however, substantially relevant to the present invention, so it is thus not described in closer detail herein.

[0016] The arrangement operates in the following manner. At the beginning of a drilling procedure, the pressure level acting in the channel 8a is controlled by the valve 7 such that it controls a valve spool known per se, provided inside the feed control valve 9, into a position which allows a flow of pressure fluid necessary for a desired maximum feed rate to flow through the feed control valve 9 to the feed motor 3 and, similarly, therethrough, back to the pressure fluid reservoir 12.

[0017] If the rock to be drilled is such that the volume of flow of pressure fluid rises to a value which equals a desired feed rate, the apparatus operates on flow control, i.e. the pressure compensator 10 keeps the flow of pressure fluid conveyed to the feed motor 3 substantially constant, so that the pressure in the system remains below a value set for the pressure limit valve 26. This takes place such that the feed pressure compensator 10 is affected, on one hand, by the pressure in the channel 11 and, on the other hand, by the pressure of the pressure fluid fed to the feed motor 3. If the drilling resistance decreases, the pressure acting over the feed motor in the channel 14a drops and more pressure fluid tends to flow through the feed control valve. Similarly, the decreasing pressure also acts in the pressure sensing channel 10b of the pressure compensator 10, which results in the pressure compensator choking the flow of pressure fluid such that the pressure difference over the pressure compensator increases. The result is that the pressure in the feed pressure channel 11 leading to the feed control valve 9 drops until the flow of pressure fluid is at a desired value and the pressure difference over the feed control valve 9 is at a similar value. Consequently, the pressure difference acting over the feed control valve 9 stays substantially constant, so that when an opening in the feed control valve 9 stays constant, the volume of flow of pressure fluid conveyed to the feed motor 3 also stays constant. If ₁ for instance, due to the hardness of rock, the feed rate is lower than the set maximum rate, which is usually the case in a normal drilling situation, it is not possible for the set volume of pressure fluid to flow through the feed motor. Since, however, the pressure difference over the feed valve 9 remains constant, the pressure in the feed channel 14a tends to increase, and the system changes into operating on pressure control. When the pressure exceeds the set value of the pressure limit 26, pressure fluid flows therethrough to the pressure fluid reservoir, and the pressure level of the feed channel 14a of the feed motor is determined by the set value of the pressure limit 26.

[0018] When the pressure in the load sensing channel 22a tends to increase, pressure fluid flows therethrough and through the choke 23a to the pressure limit 26. The choke 23a is responsible for restricting the volume of flow of pressure fluid passing through the pressure limit 26. In a situation wherein the feed rate equals the set maximum rate, the pressure level is so low that the pressure limit 26 is closed and no pressure fluid flows via the channel 22a, but substantially all pressure fluid is conveyed to the feed motor 3.

[0019] In the present invention, the properties of the pressure limit 26 are such that the value of the pressure difference acting over the pressure limit is dependent on the volume of pressure fluid flowing therethrough. A pressure loss generated by the pressure fluid flowing through the pressure limit 26 is proportional to the volume of flow. The pressure difference, in turn, is a sum of the limit value set at the pressure limit 26 and the pressure loss generated by the flow of pressure fluid. Hence, the pressure difference increases when the volume of flow of pressure fluid passing through the pressure limit 26 increases, the result thus being an increase in the value of pressure in the channel 25. Consequently, the lower the penetration rate, the smaller the volume of pressure fluid flowing through the feed motor and, correspondingly, the larger the volume of pressure fluid allowed to flow through the choke 23a and possible choke 28 as well as through the pressure limit 26. When the flow of pressure fluid flowing through the pressure limit 26 increases, the pressure in the channel 25 and in the branch 25a thereof, as well as in the pressure sensing channel 10b, increases, whereby the control pressure of the pressure compensator 10 also increases. Consequently, the pressure level of the pressure fluid to be fed to the feed motor 3 increases. Similarly, when the penetration rate is high, a larger volume of pressure fluid passes through the feed motor while a smaller volume suffices to flow through the pressure limit 26, so that the pressure level of the pressure fluid to be fed to the feed motor is lower. In connection with pressure control, the flow of pressure fluid through the choke 23a naturally causes a small pressure difference over the choke 23a. In such a case, the pressure compensator 10 is controlled by the common pressure difference shared by both the feed control valve 9 and the choke 23a. This, however, is not substantially relevant to the invention. If desired, the pressure sensing channel 10b leading to the pressure compensator 10 may be connected to the feed channel 14a or to the channel 22a prior to the choke. If the

operation of the feed and percussion devices has been connected to depend on one another, the result is that the drilling power is automatically controlled according to the hardness of rock, so that with a soft rock, the drilling power is lower and, when the rock becomes harder, the drilling power increases. The control channel 22b and the choke 23b therein are designed to control the feed pressure of the pressure fluid of the pressure fluid pump 1 in a situation wherein the feed motion has been connected to the return motion and the feed pressure is acting in the return channel 14b of the feed motor 3.

[0020] Figure 2 simply and schematically shows an embodiment of the arrangement according to the invention. For the sake of simplicity and clarity, only components substantially related to the special features of the particular embodiment are described herein. Otherwise the components and operation are similar to the components and their operation disclosed in Figure 1.

[0021] In this embodiment, the pressure compensator 10 is arranged between the feed control valve 9 and the feed motor 3. Thus, pressure fluid is fed from the pressure pump along the channels 4 and 11 directly to the feed control valve 9. Furthermore, the channel 11 received by the feed control valve 9 is connected to the pressure compensator 10 by the pressure sensing channel 10a. Similarly, from the feed channel 14a, a control channel 25' is through a choke 23' connected, on one hand, to affect the pressure compensator 10 by the pressure sensing channel 10b and, on the other hand, to the control channel 21' of the pressure fluid pump 1, as well as to the pressure limit 26 by the branch 25a'. For the sake of clarity, the figure shows neither the pressure control associated with feed return motion nor the pressure control of the pressure fluid pump 1 associated with the pressure fluid channel of the percussion device, both being shown in connection with Figure 1. They may be applied in a similar manner to the embodiment of Figure 2 as well.

[0022] In this embodiment as well, the invention operates in a manner similar to that shown in Figure 1. When the feed control valve 9 has been controlled to a position corresponding with a desired feed rate, the flow of pressure fluid from the pressure fluid pump via the feed control valve 9 and the channel 14a through the pressure compensator 10 reaches the volume of flow determined by the feed control valve 9, provided that the resistance of the rock being drilled does not prevent this. The pressure compensator 10 then keeps the pressure over the feed control valve 9 constant, and the pressure in the channel 14a stays below the set value of the pressure limit 26, so that no pres-

sure fluid thus flows through the pressure limit 26. If the hardness of rock prevents the maximum rate from being achieved, as is usually the case during normal drilling, the pressure in the channel 14a exceeds the pressure value set for the pressure limit 26, and pressure fluid flows via the choke 23' and the channel 25' through the pressure limit 26. The larger the volume of pressure fluid compelled to flow through the pressure limit 26, the higher the pressure value of the pressure limit 26 becomes, controlling the pressure fluid pump 1 via the channel 21'. As long as the the value of the pressure in the channel 14a does not exceed the predetermined pressure value of the pressure limit 26, the feed operates on "flow control", i.e. the volume of flow of pressure fluid conveyed to the feed motor 3 is kept substantially constant by means of the feed control valve 9 and the pressure compensator 10 as described in connection with Figure 1. When the pressure in the channel 14a exceeds the predetermined pressure value of the pressure limit 26, the feed, by means of the pressure limit 26, changes into a "pressure control" feed and operates on pressure control until the pressure in the channel 14a again drops to the predetermined pressure value of the pressure limit 26, or therebelow.

[0023] In the above description and drawings, the invention has been disclosed only by way of example and it is by no means restricted thereto. It is of course apparent that the feed control valve may in a manner known per se also be electrically or mechanically controllable. Similarly, it may be not only proportional but it may also change the volume of flow stepwise. Furthermore, it may be only unidirectional such that the direction of feed is changed by a separate reverse valve. The point is that the pressure acting in the pressure fluid channel of the feed motor and, therethrough, the pressure of the percussion device and the pressure compensator of the feed motor, is controlled by the pressure limit, the pressure acting over the pressure limit being proportional to the flow of pressure fluid flowing through the pressure limit.