Sealing arrangement in rotating control valve of pressure fluid-operated percussion device

The invention relates to a sealing arrangement in a rotating control valve of a pressure fluid-operated percussion device, to which percussion device a tool is mountable movable in its longitudinal direction, the percussion device containing a work chamber and a transmission piston mounted movable to compress the tool suddenly to generate a stress pulse to the tool, inlet and outlet channels for conducting pressure fluid to the percussion device and away from it, and a control valve having a rotating switch member with channels to connect inlet and outlet channels through the channels of the switch member to alternately conduct the pressure fluid through the channels to the work chamber and, correspondingly, away from the work chamber, and in the inlet channel of the pressure fluid at the switch member side end thereof at least one sealing sleeve for the purpose of sealing the inlet channel to the switch member. In the arrangement, the sealing sleeve is mounted obliquely to the surface of the switch member and the switch member side surface of the sealing sleeve is essentially in the shape of the switch member surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No. PCT/FI2010/050229, filed Mar. 24, 2010, and claims benefit of Finnish Application No. 20095317, filed Mar. 26, 2009, both of which are herein incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The invention relates to a sealing arrangement in a rotating control valve of a pressure fluid-operated percussion device, to which percussion device a tool is mountable movable in its longitudinal direction relative to the frame of the percussion device, the percussion device containing a work chamber having a transmission piston mounted movable in the axial direction of the tool to compress the tool suddenly in its longitudinal direction by the pressure of the pressure fluid acting on the transmission piston to generate a stress pulse to the tool, and a control valve, to which inlet and outlet channels lead to conduct the pressure fluid to the percussion device and away from it and which has a rotatably mounted switch member with channels for connecting said inlet and outlet channels with the switch member to alternately conduct the pressure fluid through the channels to the work chamber and, correspondingly, to release the pressure fluid from the work chamber and in the inlet channel of the pressure fluid at the switch member side end thereof at least one sealing sleeve extending under the pressure of the pressure fluid toward the surface of the switch member for the purpose of sealing the inlet channel in relation to the switch member.

In pressure fluid-operated percussion devices, pressure fluid is fed into and removed from them through feed and discharge channels, respectively. To these feed and discharge channels pressure fluid hoses are typically connected to supply the pressure fluid into the feed pump and pressure fluid container.

For percussion operation, the feed and discharge of the pressure fluid in the percussion device is controlled with various control valves. The control valve may either move linearly or rotate. In rotating valves in particular, one practical problem is the sealing between the valve and channels, because all clearances cause leaks and leaks, in turn, cause a lower operating efficiency. Sealing also includes the problem that too tight a seal increases the rotation resistance of the valve and, thus, uses up the power of the device in vain and lowers its operating efficiency.

U.S. Pat. No. 7,290,622 discloses a solution in which separate sealing sleeves are used to seal the rotating control valve and the sealing sleeves are pushed against the surface of the control valve by the pressure of the pressure fluid so that no clearance remains between them. Adjusting the supply pressure of the sealing sleeve so as to keep the generated friction as small as possible is, to some extent, hard to do, even though a separate sealing sleeve structure is useful per se.

BRIEF DESCRIPTION OF THE INVENTION

It is an object of this invention to provide a sealing arrangement implemented by sealing sleeves, with which sealing is achieved reliably and, at the same time, the friction between the sealing sleeve and rotating valve is reduced from before without affecting the reliability of the sealing.

The sealing arrangement of the invention is characterized in that the sealing sleeve is mounted obliquely with respect to the surface of the switch member in the rotation direction thereof and the surface of the sealing sleeve on the switch member side essentially equals the shape of the surface of the switch member.

The idea of the invention is that in the inlet channel of the pressure fluid at the switch member side end, the sealing sleeve is positioned obliquely with respect to the direction of movement of the surface of the rotating switch member of the valve. The idea of an embodiment of the invention is that the sealing sleeve is positioned obliquely in such a manner that the switch member side end of the sealing sleeve is before the opposite end of the sealing sleeve in the rotation direction of the switch member.

The solution of the invention achieves that when the pressure fluid channel is only partially open, in which case the pressure of the pressure fluid acts on the sealing sleeve from the switch member side of the control valve and tries to push the sealing sleeve away, the friction of the surface opposite to the pressure slows down the movement of the sealing sleeve and, thus, the sealing sleeve remains better in place against the surface of the switch member. Further, the advantage of an embodiment of the invention is that as the switch member of the control valve rotates, the friction between it and the sealing sleeve tries to move the sealing sleeve with it in the direction of movement of the switch member, whereby the sealing sleeve in its oblique longitudinal direction extends away from the switch member and, thus, tries to detach from the surface of the switch member. In this situation, the friction and forces acting on the sealing sleeve become balanced, whereby the sealing sleeve presses against the switch member at a significantly smaller force than a sealing sleeve perpendicular to the switch member would.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic sectional view of a prior-art percussion device1with a frame2, inside which there is a work chamber3and inside the work chamber3a transmission piston4. The transmission piston4is coaxial with a tool5and they may move axially so that the transmission piston4touches the tool5directly at least when the stress pulse begins to form and during its formation or indirectly through a shank fastened to the tool and known per se. On the side of the transmission piston4opposite to the tool, there is a pressure surface facing the work chamber3. For forming the stress pulse, pressure fluid is led to the work chamber3from a pressure source, such as a pump6, along an inlet channel7through a control valve8. The inlet channel7may either be a single channel or, on arrival at the control valve, it may branch into several channels, from which the pressure fluid flows simultaneously to the control valve. The control valve has a moving switch member8awith one or, as shown in the figure, several channels, such as openings or grooves8b. As the switch member8aof the control valve8moves, the pressure fluid acts on the transmission piston4through the openings or grooves8band, correspondingly, as the switch member8acontinues to move, the pressure of the pressure fluid that acted on the transmission piston4discharges through a discharge channel9. A stress pulse is formed when the pressure fluid pressure pushes the transmission piston4toward the tool5and through this compresses the tool5against the material being crushed. As it moves through the tool's5tip, such as a drill bit, to the material being crushed, such as stone, in a manner known per se, the stress pulse breaks the material. When the switch member of the control valve8prevents the pressure fluid from entering the percussion device and then allows the pressure fluid that acted on the transmission piston4to discharge through the outlet channel9to a pressure fluid container10, the stress pulse stops, and the transmission piston4that has moved a short distance, only a few millimeters, toward the tool5, is allowed to return to its initial position. This is repeated as the switch member8aof the valve8moves and alternately switches the pressure to act on the transmission piston and then allows the pressure to discharge, whereby, as the switch member8amoves continuously, a series of consecutive stress pulses is formed.

During the use of the percussion device, it is pushed in a manner known per se by using a feed force F toward the tool5and, at the same time, toward the material being crushed. To return the transmission piston4, pressure medium may be supplied to the chamber3aas necessary between stress pulses or the transmission piston may be returned by mechanical means, such as spring, or by pushing the percussion device with the feed force in the drilling direction, whereby the transmission piston moves backward in relation the percussion device, that is, to its initial position. The tool may be a part that is separate from the piston or integrated to it in a manner known per se.

In the case ofFIG. 1, the control valve8has a rotatably moving switch member8acoaxial with the tool5, which is rotated around its axis in the direction of arrow A by using a suitable rotating mechanism, such as a motor11, by means of power transmission shown schematically by dashed line. Alternatively, the switch member8ais turned rotatably back and forth using a suitable mechanism. A rotatably moving switch member may also be mounted otherwise, for instance on the frame2on the side of the work chamber3. Further, it is possible to use in all cases a control valve, whose switch member8ahas only one channel to conduct the pressure fluid toward the work chamber and, correspondingly, away from it. However, the switch member8aof the control valve8preferably has several parallel channels.

FIG. 1further shows a control unit12that may be connected to control the rotating speed of the control valve or the rate of movement of a reciprocating control valve by means of control channels or signal lines13aand13b. This type of adjustment may be implemented by several different techniques known per se by using desired parameters, such as drilling conditions, the hardness of the stone being crushed, for instance.

FIG. 2is a detailed sectional view of a rotating control valve and a sealing arrangement of the invention. By way of example, it shows a disc-like rotating switch member8aof a control valve which rotates in the direction shown by arrow A. The switch member8ahas openings8bto allow pressure fluid through the sealing sleeve20and on to the piston7of the percussion device. At the switch member8aside end that ends in the switch member8a, the inlet channel7of the pressure fluid has a sealing sleeve20.

As shown inFIG. 2, the sealing sleeve20is mounted in a space2aat an oblique angle α relative to the switch member8aso that it is inclined away from the switch member toward the direction of movement of the switch member. Thus, the end of the sealing sleeve20that is on the switch member8aside is in the direction of movement of the switch member before the end of the sealing sleeve20that is further away from the switch member8a. The sealing sleeve20is mounted slidable in its longitudinal direction in the space2aformed in the frame2or part thereof and, at the outermost end of the sealing sleeve20, there is a plug22that closes the space21and is connected stationary to the frame2. The plug22has a through-channel23, through which the pressure fluid is allowed to flow inside the sealing sleeve20and onward through a channel20ainside the sealing sleeve20.

The sealing sleeve has for the plug22a space21that is larger in cross-section than the channel20aand has a pressure surface20bon its switch member8aside. The pressure p of the pressure fluid acts on the surface20band pushes the sealing sleeve20toward the switch member8a, as a result of which the sealing sleeve20is pressed against the surface of the switch member8a. The plug22is not absolutely necessary, and just the sealing sleeve20is enough when the sealing sleeve20and the inlet channel of the pressure fluid and the frame are designed suitably.

In the situation shown inFIG. 2, the channels20aand8bin the sealing sleeve20and switch member8aare not fully in line, but the pressure of the pressure fluid acting in the channel8bof the switch member8aacts correspondingly on the surface20cof the sealing sleeve20facing the switch member8a. This tries to push the sealing sleeve20away from the surface of the switch member8a. A pressure pulse acts on the sealing sleeve20especially when the pressure fluid channel20aopens into the channel8bof the switch member, or the connection between them is closed. In this situation, the friction between the sealing sleeve20and the surface of the space2aprevents or slows down the movement of the sealing sleeve20away from the switch member8aand, this way, makes the sealing sleeve20remain essentially against the surface of the switch member8a.

As the switch member8arotates in the direction of arrow B, there is also friction between its surface and that of the sealing sleeve20, which tries to push the sealing sleeve in the direction of movement of the switch member8a. Due to the oblique position of the sealing sleeve20, the effect of the friction force also generates a force vector in the longitudinal direction of the sealing sleeve20, because the sealing sleeve20presses against the wall of the space2ain the frame2and, thus, cannot move directly with the switch member8a. As a result of this, the sealing sleeve20tries to move in its longitudinal direction away from the switch member8aand, this way, the friction force and correspondingly the force provided by the pressure pushing the sealing sleeve20toward the switch member8abecome balanced, and the friction between the switch member8aand sealing sleeve, and the power loss generated by it is smaller than it would be in a sealing sleeve that was perpendicular to the surface of the switch member8a.

FIG. 3is a schematic sectional view of an embodiment of the invention in detail. In it, separate pressure pockets8care formed in the switch member8ato reduce the friction and wear between the switch member8aand sealing sleeve20.

The pressure pockets8care recesses formed in the switch member8ain the area between the channels8bon the surface of the switch member8aon the sealing sleeve20side. As they move at the location of the sealing sleeve20and past it, a similar pressure effect is created on the bottom surface of the sealing sleeve20as at the location of the channels8bwhen their connection to the pressure fluid channel20arunning through the sealing sleeve opens or closes, whereby the sealing sleeve20tries to rise up away from the switch member8a. This reduces the friction between the switch member8aand sealing sleeve20and, consequently, also the power consumption and wear.

FIG. 4shows yet another embodiment of the invention. It shows how the rotating friction of the control valve8and thus also the power consumption may be reduced from before.

The inlet channel7of the pressure fluid, through which pressure fluid is fed to the switch member8ais furnished with sealing sleeves20in the manner described above, and the pressure p of the pressure fluid naturally acts on that side all the time.

The other side of the switch member8ais, in turn, on the work chamber3side of the transmission piston4. The essential thing for sealing is that it is good on the inlet side of the pressure fluid, but this is not a very significant factor on the work chamber side, because that side is connected to the work chamber3all the time. This, in turn, is because the channel on the work chamber side is pressurized only momentarily, whereas the inlet side of the pressure fluid is pressurized all the time. Therefore, the switch member8aof the control valve8is on the work chamber3side fitted with a thrust bearing24so that there is a clearance25between the switch member8aand percussion device frame. The size of the clearance may be adjusted for instance by using between the frame2and switch member8aa separate clearance plate or ring26having a suitable thickness. The thrust bearing24is, in turn, in the pressure fluid all the time and thus obtains both its lubrication and cooling from it. The switch member8ais rotated in a manner known per se via an axle27, for instance, by means of a suitable rotating device, such as a hydraulic or electric motor.

FIG. 5shows yet another embodiment of the invention. Herein, the obliqueness of the sealing sleeve20shown by arrow A is the opposite to what is shown inFIGS. 2 to 4. In this embodiment, the effect of the pressure fluid on the sealing sleeve20is similar to that in the other figures, but the lightening effect of the surfaces oblique in the direction of movement does not exist. Further, a cross A′ in a circle indicates that the direction of movement of the switch member8amay be transverse to the plane of the figure or something between arrow A and cross A′. In these embodiments, too, the effect of the pressure and friction between the sealing sleeve20and walls of the space2ais the same.

Above, the invention is described in the specification and drawings by way of example only and it is in no way limited to the description. Different details of embodiments may be implemented in different ways and they may also be combined with each other. Thus, details in different figures,FIGS. 1 to 5, may be combined with each other in different manners to obtain the required embodiments in practice. The rotation of the switch member8aof the control valve8may be implemented in any manner known per se mechanically, electrically, pneumatically or hydraulically. The cross-section of the sealing sleeve may be round, oval, angular, etc. Similarly, the angle of obliqueness may be 45° or between 30° and 80°, for instance. Instead of a plate-like switch member8a, the switch member may be cylindrical, conical, or spherical, as long as the shape of the end of the sealing member corresponds to the shape of the surface of the switch member. There may also be more than one sealing member.