The invention relates to a hydraulic arrangement for turning the actuator of a rock drilling machine about its turning axis to at least three different positions, the arrangement comprising a pressure medium cylinder provided with two cylinder spaces and two pistons, the cylinder being arranged to affect and turn the actuator, and at least one control valve with which pressure fluid can be fed into the cylinder spaces of the cylinder such that the two pistons can be simultaneously fully ejected or fully retracted, or one can be ejected while the other is retracted.

In rock drilling machines and especially in rock bolting machines, it is often necessary to turn the actuator, such as a bolting head, which comprises one or more devices, about an axis parallel to a drill rod. In rock bolting, first a drill rod, then a feed apparatus for feeding soldering material, and finally a bolt feeding apparatus can be turned, in succession, such that they align with the same axis, whereby the soldering material and then the bolt can be fed into the drill hole. Normally, this is effected by moving different apparatuses either along transverse rails by a linear movement or by turning the apparatuses about an axis parallel to the axis of the drill rod by means of hydraulic cylinders. The problem with known solutions is that accurate alignment requires either a separate cylinder for each movement or mechanic stoppers to effect sufficiently accurate alignment. Another problem is that to control different movements, a separate control lever is often needed for each movement, or a plural

number of control levers will have to be used simultaneously, which makes positioning difficult, subjecting the process to errors.

The object of the present invention is to provide a hydraulic arrangement by which control can be implemented in a simple and reliable manner. The hydraulic arrangement according to the invention is characterized in that the control valve can be placed in at least three control positions but in only one at a time; that in each control position the pressure fluid is arranged to affect both cylinder spaces of the cylinder so that in the control position concerned, the pistons always settle in a certain predefined position.

The essential idea of the invention is that each control valve is arranged to control both hydraulic cylinders at the same time such that when a control valve is in a certain position, the cylinders settle in a certain predefined position, thereby turning the drill machine to a certain predefined position.

The arrangement according to the invention makes it possible to always turn the actuator of the rock drilling machine to a correct predefined position.

In the following, the invention will be described in greater detail with reference to the attached drawings, in which fig. 1 shows a schematic view of a hydraulic arrangement according to the invention, figs. 2a to 2c show a schematic view of positioning of a bolting head with the arrangement according to fig. 1, fig. 3 shows a schematic view of another embodiment of a hydraulic arrangement according to the invention, and fig. 4a to 4c show a schematic view of

positioning of a bolting head with the arrangement according to fig. 3.

Fig. 1 shows a schematic view of an embodiment implementing a hydraulic arrangement according to the invention. In the figure, reference number 1 indicates a bolting head functioning as an actuator of a rock drilling machine. A cylinder 2 turning the bolting head is a double cylinder with cylinder spaces 2a and 2b, both of which comprise an independently moving piston 3a and 3b, respectively. Both cylinder spaces 2a and 2b are connected to pressure-controlled pilot-operated check valves 6, 7, 8 and 9 through pressure channels 4a, 4b and 5a, 5b, respectively, such that channels 4a and 5a are connected to pilot-operated check valves 6 and 8, and channels 4b and 5b are connected in parallel to pilot-operated check valves 7 and 9. Normally, when no pressure is fed to the pilot-operated check valves on their supply side, the valves close and stop the flow of the pressure medium to and from cylinder 2. Pilot-operated check valves 6 and 9 are connected to control valves 11 and 12 through pressure fluid channels 10a to 10c. Further, one pressure fluid channel lOd coming from pilot-operated check valves 8 and 9 is connected directly to a pressure fluid container 13. Control valves 11 and 12 receive pressure fluid along pressure fluid channel 14, and, correspondingly, pressure fluid channel 15 leads from valve 11 directly to the pressure fluid container 13.

Figs. 2a to 2c show how valves 11 and 12 together with cylinder 2 control the bolting head. All the figures show the positions of valves 11 and 12, cylinder 2 and the bolting head after a control movement. In a situation illustrated by fig. 1, cylinder 2 is at its shortest, i.e. in one extreme position. When control valve 11 is moved to a position

according to fig. 2a, the pressure fluid can flow through channel 10a to pilot-operated check valves 6 and 7. Valve 12 is then in free position as shown in fig. 2a, and so it does not affect the operation in any way. The pressure fluid then penetrates into the cylinder spaces 2a and 2b through pilot-operated check valves 6 and 7, behind the pistons 3a and 3b, whereby pistons 3a and 3b project as shown in fig. 2a. Since there is a partition wall between the cylinder spaces 2a and 2b in the double cylinder 2, the pressures prevailing in the cylinder spaces have no effect whatsoever on each other. The visible bolting head, which is arranged to pivot about an axis 17 in relation to a frame 16, is here in its extreme left-hand-side position, and the drilling axis of a drill machine 18 is in a predefined position. A bolt feeding apparatus 19 and a concrete feeding apparatus 20 are then off-set from line L.

When valve 11 is in free position, i.e. in the middle position, no pressure fluid flows from channel 14, and cylinder 2 remains in its current position. When valve 12 is pushed to the position shown in fig. 2b, the pressure fluid flows from channel 14 through valve 12 to channel 10c and further through pressure- controlled pilot-operated check valves 8 and 9 to channels 4a and 5b. The piston 3a of cylinder 2a remains ejected, but the piston 3b of cylinder 2b slides inside until it is fully retracted. Here the distance between the positions to which the piston rods of the cylinder 2 are fixed is between the extreme positions of the piston rods, but is always exactly of a certain size. The bolting head 1 is here turned such that the concrete feeding apparatus 20 is at line L, in alignment with the above drilling axis. When valve 11 is moved to the position shown

in fig. 2c, the pressure fluid channel 14 is connected to channel 10b, while channel 10a is connected through channel 15 to the pressure fluid container. Valve 12 is here in free position and does not affect the operation in any way. The pressure fluid here flows from channel 10b through pilot-operated check valves 6 and 7 to both cylinder spaces 2a and 2b so that the pressure pushes the pistons 3a and 3b inside the cylinder. Since piston 3a is already inside the cylinder, pressure fluid flows only through pilot-operated check valve 7, also pushing piston 3b inside the cylinder so that the cylinder 2 is at its shortest, in the position shown in fig. 1. The axis of the bolt feeding apparatus 19 and thereby the bolt thereon align with the drilling axis at line L. In accordance with figs. 2a to 2c, hydraulic control is hereby effected: the pistons 3a and 3b of the double cylinder 2 can be moved to three predefined positions in order to pivot the bolting head about its axis. In practice, valves 11 and 12 are preferably cross- connected valves in one and the same valve unit: when the control rod is moved forward or backward, the cylinder 2 moves to the extreme positions, and movement of the control lever from the middle position in the transverse direction produces the intermediate positions as shown in fig. 2b.

Fig. 3 shows an arrangement corresponding to the one shown in fig. 1, with the exception that it comprises a separate change-over switch, which is needed since the cylinders of the double cylinder 2 are designed to differ in length such that control of the cylinder in different ways gives four predefined positions. The operation and arrangement according to fig. 3 are otherwise exactly the same as in fig. 1, but the figure shows a separate directional control valve 22 that is arranged to change channels lOd and 10c with

each other such that it is possible to make a choice between two middle positions. In this embodiment, the operation of valve 11 is exactly the same as and corresponds to the positions shown in figs. 2a and 2c. Likewise, the control of the middle position, i.e. the operation and connections of valve 12, completely correspond to fig. 2b, but the position of the double valve 2 depends on the position of valve 22.

Figs. 4a to 4c, in turn, show the control of the arrangement according to fig. 3 with the different positions of directional control valve 22. Fig. 4a shows the position of valves 11 and 12 when the operation of the arrangement is to be controlled with directional control valve 22. The position of directional control valve 22 can be selected either before using valve 12 or during its use. Fig. 4b shows a situation where by the use of valve 12, one of the pistons of the double cylinder 2, i.e. here piston 3a, is retracted, while piston 3b is ejected. The change of the position of directional control valve 22 in accordance with fig. 4c produces a situation where the positions of pistons 3a and 3b are reversed, i.e. piston 3a is ejected and piston 3b is retracted. Because of the different impact lengths of pistons 3a and 3b, there are two different distances between the heads of the piston rods of the cylinder 2, and so there are two accurately defined positions between the extreme positions of the ends of the piston rods of the cylinder 2, whereby, e.g. when the bolting head is turned, four permanent turning positions are provided for different actuators. This embodiment is useful when there are four actuators and when it must be possible to use each one of them in exactly the same position in the axial direction. An example for this is a bolting head comprising a drill machine for drilling a hole, a

solder resin feeding apparatus, a concrete feeding apparatus, and a bolt feeding apparatus. In a situation like this, a valve can be used for choosing whether to use the resin feeding apparatus or the concrete feeding apparatus, since both are not necessarily needed simultaneously. When resin is to be fed into a drill hole, the shorter piston rod 3a is retracted into its cylinder space, whereby the bolting head 1 turns about axis 17, and a tube 21 of the resin feeding apparatus aligns with the drilling axis of the above drill machine 18 in accordance with fig. 4b. If concrete is to be used instead of resin, piston 3a remains ejected from its cylinder space, whereas piston 3b is retracted into its cylinder space, whereby a concrete delivery hose 20 aligns with the drill hole as shown in fig. 4c.

Sometimes all four alternative positions are needed in succession. Valve 12 can be connected in the same way as valve 11: channel lOd is connected to one channel of valve 12, and so a change-over can be conducted between channels 10c and lOd by controlling the valve so as to achieve the desired intermediate position. On the basis of the above, this solution as such is obvious to a person skilled in the art.

The invention is described in the above speci- fication and the accompanying drawings only by way of an example, and it is not in any way limited thereto. The essential feature is that the control valves are arranged to control both cylinders by forced control so that a certain control movement always makes the cylin- ders settle in a certain predefined position. Valves 11 and 12 are preferably cross-connected valves controlled by a single control lever. The second position of valve 12 shown in the figures is not needed in the control when only three control positions are used. Valve 12 can then have a simpler structure, or the second posi-

tion can be used for controlling some other actuator. When the same lever is to be placed in four control positions, valve 12 must be implemented as depicted in the figure.