WO2006054949A1

WO2006054949A1 - Percussion device having an adjustable stroke length

Info

Publication number: WO2006054949A1
Application number: PCT/SE2005/001758
Authority: WO
Inventors: Maria Pettersson; Per-Erik Larsson
Original assignee: Atlas Copco Rock Drills Ab
Priority date: 2004-11-22
Filing date: 2005-11-22
Publication date: 2006-05-26
Also published as: SE0402844D0

Abstract

The present invention relates to a percussion device including a hammer piston, and including a valve 9 for controlling the reciprocating movement of the hammer piston in a cylinder. The control is obtained by pressurization chambers in said cylinder. The percussion device includes means for adjusting the stroke length of said hammer piston by adjusting the switching speed of said valve using said means, to thereby obtain a desired stroke length. Thereby, a desired stroke length of the hammer piston is obtained in a simple and convenient manner. The present invention also relates to a method.

Description

Percussion device having an adjustable stroke length

Field of the invention

The present invention relates to a percussion device and a method for adjusting the stroke length of a hammer piston in a percussion device, as defined in the preamble of claim 1 and 17.

Background of the invention

During rock drilling, it is important to adjust the impact energy of a percussion device to prevailing conditions, e.g., quality and properties of the rock. The hardness of rock, and thereby drillability, may vary substantially, and impacting the rock using to much or to little power results in inefficient drilling with the risk of undesired reflections from the rock and shortened working life of drill steel and other equipment. The impact energy, which depends on impact velocity, is directly dependent of . the stroke length of the hammer piston. Therefore, it is important to be able to adjust the stroke energy to thereby obtain an impact power adapted to the rock in which drilling is performed. At rock drilling according to the prior art, the percussion device is usually set to a stroke length capable of coping with the "worst case", i.e., the impact power is set to the value that is necessary to be able to drill in what is expected to be the hardest rock during drilling. Consequently, variations occurring in the hardness of the rock, which may be substantial, are not taken into consideration. In order to adjust the stroke length, the percussion device has to be stopped, a valve adjustment has to be performed in order to adjust the stroke length and thereafter the percussion device has to be restarted. Accordingly, this is a complex and time consuming operation, and thereby costly as well. The above described method of adjusting the stroke length and thereby the impact energy includes a plurality of disadvantages. Apart from the fact that the above adjustment of the stroke length is time consuming due to the necessary percussion device stopping, usually there are only two stroke lengths. Consequently, it is only possible to choose between two different stroke lengths. This is a substantial disadvantage, since the quality of rock may vary substantially, and, thereby, the applied impact energy can not particularly well be adapted to the rock. Further, the impact energy may require adjustment by other reasons as well, apart from the a priori hardness of the rock, e.g., due to the par¬ ticular drill steel that is used and/or in relation to a par¬ ticular drill bit and/or drill bit wear. Therefore it is, for a number of reasons, important to be able to adjust the impact energy in a precise and correct manner.

EP 0112810A2 discloses a method for optimizing percussion rock drilling with regard to impact velocity and impact frequency. The stroke length, may in this known method, be adjusted by determining the impact velocity into the rock, and in depend¬ ence thereof select a specific pair of a plurality of pairs of available drainage channels, whereby a suitable stroke length is selected. In this known percussion device, the stroke length of the percussion device is dependent of which of a plurality of various pressure channels and/or drainage chan¬ nels that is used. The obtained stroke length is directly dependent on the number of pressure or drainage channels, and the obtainable number of various stroke lengths is thus lim¬ ited to the number of available pressure or drainage channels. Further, the method described in EP0112810A2 includes, due to the plurality of channels that are used, a plurality of potential sources of leakage. Even further, the prior art stroke length adjustment requires a setting of which channel to use, which, as described above, may be time consuming and result in further possible sources of stopped operation.

Consequently, there exists a need for a percussion device including an improved, yet simplified, adjustment of the stroke length of the hammer piston.

Object and most important features of the invention

It is an object of the present invention to provide an apparatus and a method that solves the above problem. More specifically, it is an object of the present invention to provide an improved percussion device and a method for adjusting the stroke length of a hammer piston in a percussion device, wherein, even during operation, it in a simple manner is possible to adjust the stroke length to a desired, arbitrary length, whereby the need of stopping the percussion device to set the stroke length of a hammer piston is eliminated.

These and other objects are, according to the present invention, achieved by an apparatus as defined in claim 1 and a method as defined in claims 17 and 31. According to the present invention, the above mentioned objects are achieved by a percussion device including a hammer piston, and further including a valve for controlling the reciprocating movement of a hammer piston in a cylinder by pressurizing chambers in said cylinder. The cylinder may be divided into various chambers, e.g., by lands on the hammer piston. According to the invention the percussion device includes means for adjusting the stroke length of the hammer piston by adjusting a switching parameter of said valve using said means. Thereby, a desired stroke length may be obtained in a continuous manner, wherein this continuous adjustment may also be performed in operation. According to the present invention, there is provided a percussion device wherein the impact power in a simple and convenient manner, and in operation, may be adapted to existing circumstances, to thereby obtain an improved working life for drill steel and other parts of the drilling equipment. The pressure levels in said chambers may be determined by channels that open and close by lands on the hammer piston.

According to a preferred embodiment of the present invention, the switching parameter is adjusted by throttling the discharge flow, and in accordance with another embodiment the inflow is throttled. Thereby, a flexible solution is obtained, which may be adapted to various circumstances and conditions.

According to another embodiment said throttling is performed remote from the percussion device. This makes it simple for an operator to adjust the stroke length of the hammer piston as desired, and a useful percussion device is provided.

According to a further embodiment of the present invention, the valve switching parameter is adjusted by a throttle valve or a variable constant flow valve. Thereby, flow adjustment and in that way valve switching may be obtained by frequently occurring valves on the market, which results in an economic percussion device with easily obtainable spare parts.

According to one embodiment of the present invention, the adjustment of the stroke length of the hammer piston is continuous. This results in a very flexible percussion device, wherein the stroke length of the percussion device may be set to an arbitrary length within limitations set by the physical dimensions.

According to another embodiment of the present invention, the adjustment is performed by a number of fixed preset throttlings. Thereby, a simple solution is provided, wherein an operator comfortably, and still during operation of the percussion device, may choose a suitable throttling and thereby appropriate stroke length.

The setting of the valve switching parameter may be automatic or manual. During manual setting an operator may, e.g. during operation, adjust the valve switching parameter and thereby the stroke length of the hammer piston, e.g., using a knob.

During automatic adjustment, the valve switching parameter may, for example, be adjusted by adjustment means, e.g., in form of an adjustment computer, wherein said adjustment means adjusts the valve switching and thereby the stroke length of the hammer piston at least partly based on, e.g., one or more parameter values representing the reflected energy. For example, the stroke length of the hammer piston may be adjusted in such a manner that reflected energy is minimized. Said value or values representing the reflected energy may be generated by sensing, monitoring, measurement, or calculation of a representative quantity representing the reflected energy, wherein the representative quantity representing the reflected energy may consist of at least one damping pressure in at least one damping chamber. As an alternative to, or in addition to the above adjustment, the adjustment may be performed based on the penetration rate.

Said adjustment parameter may consist of one or more from the group: adjustment speed, adjustment time, adjustment length. According to further embodiments of the present invention the percussion device is a hydraulic or pneumatic percussion device.

The present invention further relates to a method for adjusting the stroke length of a hammer piston in a percussion device. The above described advantages are achieved by this method. Further advantages are achieved by various aspects of the invention and will be apparent from the following detailed description.

Brief description of the drawings Figure 1 discloses a percussion device according to one embodiment of the present invention.

Figure 2 discloses a percussion device according to an alternative embodiment of the present invention.

Figure 3 discloses a percussion device according to another alternative embodiment of the present invention.

Figure 4 discloses a percussion device according to a further alternative embodiment of the present invention.

Detailed description of preferred embodiments

With reference to figure 1, a hammer piston 2 in a percussion device is arranged to perform a reciprocating movement within a cylinder 3, which is divided into sections or chambers 3a, 3b, 3c by lands 2' , 2'' arranged on the hammer piston, wherein the chambers 3a, 3b, 3c may be individually pressurized. A valve switching channel 7 is either connected to pressure (by the channel 4a) or drainage (by the channel 6) depending on the position of the hammer piston waist. However, when the hammer piston is in a position as described in fig. 1, i.e. in a position wherein the hammer piston lands 2' , 2" ' blocks both the channel 4a and the channel 6, the pressure in the chamber 3b depends on whether the piston is performing an impact movement or a return movement. If an impact movement is performed, i.e., the piston moves to the left in the figure, the chamber 3b has lastly been connected to channel 6 and is accordingly drained, which further means that, as is shown in fig. 1, the valve 9 is in the shown position 9c with the drive area Al pressurized and the drive area A2 pressure relieved. As is shown in the figure, the chamber 3c is permanently pressurized over the channel 4b to achieve the piston 2 return motion. However, the drive area 3c' is smaller than the drive area 3a' , which has as result that as soon as the chamber 3a is pressurized over the channel 15 by means of the valve 9 the force acting on the hammer piston 2 will be greater in the direction towards the drill steel shank 8, whereupon the piston will perform a stroke. When, however, the chamber 3a then is drained by means of the valve 9 over the same channel 15 a force in return direction will act on the hammer piston. In figure 1 is further shown a preferred embodiment of the present invention. The percussion device 1 according to the invention is preferably a hydraulic device. However, pneumatic percussion devices may also use the principle of the present invention.

The drive chamber 3a with drive area 3a' is according to the present invention alternately connected, in accordance with the prior art and according to the above, over the channel 15 to a pressure source P and to a drainage (tank) T, by the valve 9. Instead of, as in the prior art, adjust movement of the hammer piston 2 by letting the position and switching of the valve 9 be determined by pressure geometrically affected by a plurality of drilled channels, which open and close by the lands on the hammer piston, the stroke length of the hammer piston is, according to the present invention, adjusted by adjusting the switching speed of the valve 9 at the rear piston direction switching, i.e., at the position where the hammer piston 2 is on its way back after having impacted the drilling steel shank 8 and again is about turn towards the drilling steel shank for a new stroke. The switching speed, or the time it takes until the valve switches position, is affected by flow regulation, wherein said flow regulation may be achieved in a number of ways. The position of the valve is adjusted by the pressure in the chamber 3b between the two lands of the hammer piston 2. As is shown in the figure, the drive area Al of the valve 9 is constantly pressurized, and when the chamber 3b is pressure relieved the valve will be in the position 9c, shown in figure 1. When the chamber 3b is pressurized, however, which occurs when the hammer piston 2 has moved enough to the left in the figure so that the land 2'' sets free the opening to the channel 4a, the valve will, due to a larger drive area A2 on the end of the valve pointing towards the chamber 3b, switch position such that the valve configuration 9a prevails, i.e., the chamber 3a will be drained towards a tank T at the same time as pressurization of the chamber 3a is blocked. The intermediate valve position 9b, shown in the figure, will only prevail shortly during the actual valve switching. A steady state with the setting 9b will not occur. It may, however, be advantageous to first block the flows prior to reversing them. Naturally, as is apparent to a person skilled in the art, a valve lacking this intermediate position may be used. Further with reference to figure 1, a preferred way of achieving the required flow adjustment according to the present invention, is shown. The adjustment may be obtained by throttling 10 the drainage flow of the chamber 3b, i.e., the drainage flow (channel 6) of the valve 9, wherein, for example, common throttle valves may be used. In this way only one drainage channel 6 is required, instead of drilling a plurality of channels in the cylinder bore. The switching time of the cylinder 9 at the rear piston direction switching may be varied according to the following. If there is no throttling at all, i.e., the chamber 3b is drained as soon as the land 2' sets free the opening of the channel 6, whereupon the pressure on the drive area Al of the valve 9 switches the valve so that the chamber 3a, and thereby its drive area 3a' is pressurized, a fast rear piston direction switching is achieved (the hammer piston has not reached so far to the right in the figure before it changes direction) . Thereby, a short stroke length /low impact energy is obtained, which, for example, may be suitable when drilling in soft rock. If, on the other hand, there is a heavy throttling 10 of the drainage flow, the movement of the valve will be slowered by the throttling pressure fall, and a late rear piston direction switching is obtained (i.e., the hammer piston will reach considerably further to the right in the figure before the chamber 3a is pressurized) , and thereby a long stroke length /high impact energy is obtained, which may be desirable if, for example, the rock is hard. Accordingly, the present invention provides a continuously adjustable stroke length, wherein a user need not stop the percussion device to change the drainage channel to use. The adjustment of the drainage flow, and accordingly stroke length and impact energy, may thereby be performed during operation of the percussion device 1, and also at a certain distance from the percussion device 1, e.g., on the rig or at another central location, e.g., manually by an operator turning, e.g., a knob or automatically by means of some sort of adjustment means, as described above.

An alternative embodiment of the present invention is shown in figure 2. In this embodiment, the user may, in advance, set a number of optional fixed throttlings 12a-12d. Although four such fixed throttlings are shown in the figure, it is to be understood that fewer or more than four throttlings may be used. Which of these throttlings 12a-d to be used at a specific occasion may be chosen by the operator, and the greater the number of fixed throttlings, the more various impact energies may be achieved, and the stroke length may almost be continuously adjustable. As is apparent to a person skilled in the art, the choice of throttling may also here be performed continuously during operation, e.g. manually by an operator turning, e.g., a knob, or automatically by means of some sort of adjustment means. Alternatively, a variable constant flow valve may be used instead of a throttle valve, which independently of pressure and temperature keeps the flow constant at a set, however adjustable, value.

The switching flow to and from the valve 9 may be adjusted by throttling the discharge flow (as disclosed above) . In figure 3 is shown an alternative embodiment wherein the inflow to the pressure area Al, facing away from the chamber 3b, is adjusted instead. This is performed using a throttle valve 11 and a non return valve 12 parallel to the throttle valve 11. As before, the drive area A2 is larger than Al, and when the hammer piston in figure 3 has moved enough to the left so that the chamber 3b is pressurized over the channel 4b, the valve 9 will switch through pressurizing over the channel 7, whereby front piston direction switching is initiated (i.e., the switching that occurs when the hammer piston is heading towards/reaches the drill steel shank) . During valve switching, hydraulic fluid is pressed backwards through the non return valve 12, and the function corresponds to the function of front piston direction switching according to figures 1-2. When the land 2' then sets free the inlet of the drainage channel into the chamber 3b, the chamber 3b will be drained. In this situation there will be a remaining pressure P acting on Al, whereby the valve 9 will move somewhat, but the amount of fluid in the channel between the throttle valve 11 and the surface Al will be so small that a valve switch will not occur until the pressure disappears. Accordingly, more fluid is needed to obtain a valve switching, and since this fluid is supplied through the throttle valve 11 the valve switching is slow and may thereby be arbitrary adjusted using the throttle valve 11. The more the flow is throttled, the slower the motion of the valve 9, and the stroke length of the hammer piston increases.

In figure 4 is shown a further alternative embodiment of the present invention, wherein the adjustable throttling in figure 3 is exchanged for a number of fixed throttlings lla-lld. The operator may, as before, choose which of these throttlings to be used at a specific occasion. Further, also in the embodiments shown in figures 3 and 4 the choice of throttlings may also be performed continuously during operation, e.g. manually by an operator turning, e.g., a knob or automatically by means of some sort of adjustment means, or according to what have been previously mentioned.

Irrespective of if the throttling is performed in the inflow line or in the discharge line the throttling may, as mentioned above, be controlled remote from the percussion device 1. This results in a simple and comfortable control of valve switching speed and thereby change of stroke length of the hammer piston 2 in accordance with prevailing operation conditions.

In the preferred embodiment of the present invention, only one inflow line 7 is used, and also only one drainage channel 6. Thereby, possible leakages are reduced. Further, the manufacturing of a percussion device 1 according to the present invention is thereby simplified.

The present invention has been described in connection with a hydraulically driven percussion device. However, a person skilled in the art realises that the used hydraulic valves easily may be exchanged for suitable pneumatic valves in a pneumatic percussion device.

Claims

1. Percussion device (1) including a hammer piston, and including a valve (9) for controlling the reciprocating movement of the hammer piston in a cylinder by controlling pressurization of a chamber or chambers in said cylinder, characterised in that the percussion device (1) includes means for adjusting a switching parameter of said valve (9) to thereby adjust the stroke length of said hammer piston (2) in such a manner that a desired stroke length is obtained.

2. Percussion device according to claim 1, wherein the pressures in said chamber or chambers is determined by channels (6, 4a) that are opened and closed by lands of the hammer piston (1) .

3. Percussion device according to claim 1 or 2, wherein said valve (9) is arranged, in a first position, to control pressurization of a chamber in said cylinder such that a force acting on the hammer piston in impact direction is obtained, whereby said means adjust switching to said first position (9a) from a second position (9c) .

4. Percussion device according to claim 3, wherein said valve is arranged, in said second position, to control pressurization of a chamber in said cylinder such that a force acting on the hammer piston in a direction opposite to said impact direction is obtained.

5. Percussion device according to claim 3 or 4, wherein said means are arranged to adjust the time at which switching from said second position (9c) to said first position (9a) is to occur, so that a desired stroke length is obtained.

6. Percussion device according to any of the claims 1-5, wherein said valve is arranged to be controlled using pressurization and pressure relief of drive surfaces/drive areas arranged on the valve.

7. Percussion device according to any of the claims 1-6, wherein the switching parameter of said valve (9) is arranged to be adjusted by means for throttling a discharge flow (β) .

8. Percussion device according to any of the claims 1-7, wherein the switching parameter of said valve (9) is arranged to be adjusted by means for throttling an inflow (6) .

9. Percussion device according to claim 7 or 8, wherein said inflow and/or discharge flow constitutes inflow and/or discharge flow to/from a drive surface/drive area acting on the valve.

10. Percussion device according to any of the claims 7-9, wherein the adjustment of said throttling is arranged to be performed remote from said percussion device (1) .

11. Percussion device according to any of the claims 1-10, wherein the switching parameter of said valve (9) is adjusted by any of: a throttling valve or a variable constant flow valve.

12. Percussion device according to any of the preceding claims, wherein the adjustment of said stroke length^' is arranged to be performed continuously.

13.Percussion device according to any of the claims 1-12, wherein the adjustment of said stroke length includes a number of presetable throttlings (12) .

14. Percussion device according to any of the preceding claims, wherein said percussion device (1) is a hydraulic percussion device.

15. Percussion device according to any of the preceding claims, wherein said percussion device (1) is a pneumatic percussion device.

16. Percussion device according to any of the preceding claims, wherein said switching parameter consists of on or more from the group: switching speed, switching time, switching length.

17.Method at a percussion device including a hammer piston, and including a valve (9) for controlling the reciprocating movement of the hammer piston in a cylinder by controlling pressurization of a chamber or chambers in said cylinder, characterised in the step of adjusting a switching parameter of said valve (9) to thereby adjust the stroke length of said hammer piston (2) in such a manner that a desired stroke length is obtained.

18.Method according to claim 17, wherein the pressures in said chamber or chambers is determined by channels (6, 4a) that are opened and closed by lands of the hammer piston (2) .

19.Method according to claim 17 or 18, wherein said valve (9) in a first position (9a), controls pressurization of a chamber in said cylinder such that a force acting on the hammer piston in impact direction is obtained, whereby switching to said first position (9a) from a second position (9c) is adjusted.

20.Method according to claim 19, wherein said valve, in said second position, controls pressurization of a chamber in said cylinder such that a force acting on the hammer piston in a direction opposite to said impact direction is obtained.

21.Method according to claim 19 or 20, wherein the method includes the step of adjusting the time at which switch- ing from said second position (9c) to said first position (9a) occurs, so that a desired stroke length is obtained.

22.Method according to any of the claims 17-21, wherein said valve is controlled using pressurization and pressure relief of drive surfaces/drive areas arranged on the valve.

23.Method according to claim 22, wherein the switching speed of said valve (9) is adjusted by throttling a discharge flow (6) .

24.Method according to claim 22 or 23, wherein the switching speed of said valve (9) is adjusted by means for throttling a inflow (7) .

25.Method according to claim 23 or 24, wherein said inflow and/or discharge flow constitutes inflow and/or discharge flow to/from a drive surface/drive area acting on the valve.

26.Method according to any of the claims 17-25, wherein said throttling is adjusted remote from said percussion device (1) .

27.Method according to any of the claims 17-26, wherein the switching parameter of said valve (9) is adjusted by any of: a throttling valve or a variable constant flow valve.

28.Method according to any of the 17-27, wherein the adjustment of said stroke length is arranged to be performed continuously.

29.Method according to any of the claims 17-28, wherein said percussion device (1) is a hydraulic percussion device.

30.Method according to any of the claims 17-29, wherein said percussion device (1) is a pneumatic percussion device.

31.Method for adjusting the stroke length of a hammer piston in a percussion device including a valve (9) for control¬ ling the reciprocating movement of said hammer piston, characterised in that the method includes the step: - to adjust the switching speed of said valve (9) by flow adjustment, whereby the stroke length of said hammer pis¬ ton (2) increases the more the flow decreases.