Arrangement and method for heating hydraulic impact device

Abstract

An arrangement and method for heating an impact device of a rock treating machine (Rtm) in low-temperature operating conditions is provided. The arrangement includes a warm-up mode (WM) for feeding pre-heated hydraulic fluid through a feed channel to a hydraulic circuit of the impact device. One or more hydraulic accumulators are provided in the hydraulic circuit. The feed channel is provided with a control element for limiting the feeding of the pre-heated hydraulic fluid during the warm-up mode. The control element limits the feeding of the pre-heated hydraulic fluid in the feed channel so that separating elements of the pressure accumulators do not move.

Claims

1. An arrangement for heating a hydraulic impact device of a rock treating machine in low-temperature operating conditions, the arrangement comprising: a selectively executable warm-up mode for feeding pre-heated hydraulic fluid through at least one feed channel to a hydraulic circuit of the impact device, wherein the hydraulic circuit of the impact device is connected to at least one pressure accumulator provided with pre-charge pressure, wherein the feed channel is provided with at least one control element for limiting the feeding of the pre-heated hydraulic fluid in response to the selected warm-up mode, and wherein the control element is configured to limit feeding of the pre-heated hydraulic fluid in the feed channel so that a pressure is below a first pre-charge pressure of a first pressure accumulator, which is located first downstream of a flow of the fluid being fed.

2. The arrangement as claimed in claim 1, wherein the first pressure accumulator is a high-pressure accumulator arranged for storing pressurized hydraulic fluid for executing movement of a percussion piston of the impact device in an impact direction, wherein the hydraulic circuit includes a second pressure accumulator being a low-pressure accumulator provided with a second pre-charge pressure, which is lower than the first pre-charge pressure, and wherein the control element is configured to control the feeding of the pre-heated hydraulic fluid so that pressure at a first fluid space of the first pressure accumulator is lower than the first pre-charge pressure, and that pressure at a second fluid space of the second pressure accumulator is lower than the second pre-charge pressure.

3. The arrangement as claimed in claim 1, wherein the control element is a throttle.

4. The arrangement as claimed in claim 1, wherein the control element is a proportional valve having an adjustable opening arranged for throttling the pre-heated hydraulic fluid being fed.

5. The arrangement as claimed in claim 1, further comprising at least one control unit arranged for at least initiating and terminating execution of the selected warm-up mode.

6. The arrangement as claimed in claim 1, further comprising: at least one control unit; and at least one temperature sensor arranged for providing temperature data, wherein the selected warm-up mode is controlled in response to the temperature data.

7. A rock drilling rig comprising: a movable carrier; at least one drilling boom movably mounted to the carrier; at least one drilling unit mounted to the at least one drilling boom and including a feed beam; a rock drilling machine mounted on the feed beam (5) and including an impact device; and an arrangement in accordance with claim 1 arranged for heating the impact device in low-temperature operating conditions.

8. A method of heating an impact device of a rock treating machine in low-temperature operating conditions, the method comprising: conducting pre-heated hydraulic fluid selectively to a hydraulic circuit of the impact device for providing the rock treating machine with a warm-up mode; executing the warm-up mode before initiating a normal operational mode; conducting the pre-heated hydraulic fluid in a hydraulic circuit of the impact device via at least one pressure accumulator provided with a pre-charge pressure; conducting the pre-heated hydraulic fluid through at least one control element to the hydraulic circuit of the impact device during the warm-up mode; and limiting feeding of the pre-heated hydraulic fluid to the impact device by means of the control element for reducing pressure at a first pressure accumulator below a first pre-charge pressure of the first pressure accumulator, which is a first of the at least one pressure accumulator receiving the pre-heated hydraulic fluid in a downstream direction.

9. The method as claimed in claim 8, further comprising limiting properties of the conducted pre-heated hydraulic fluid by means of the control element so that an impact cycle of the impact device is operating with reduced operational frequency during the warm-up mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic side view of a rock drilling rig.

(2) FIG. 2 is a schematic view of a hydraulic rock drilling machine.

(3) FIG. 3 is a schematic view of an arrangement for preheating an impact device.

(4) FIG. 4 is a schematic view of pressure accumulators connected to a hydraulic circuit of an impact device.

(5) FIG. 5 is a schematic view of a pressure accumulator and movement of a separating element due to pressure difference in its pressure spaces.

(6) FIG. 6 is a schematic side view of a work machine provided with a hydraulic breaking hammer.

(7) For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION

(8) FIG. 1 shows a rock drilling rig 1 intended for surface drilling. The rock drilling rig 1 includes a movable carrier 2 and at least one drilling boom 3 connected to the carrier 2. At a distal end portion of the drilling boom 3 is a drilling unit 4 provided with a feed beam 5 and a rock drilling machine 6 supported on it. A drilling tool 7 is connectable to the drilling machine 6. The rock drilling machine 6 may include a shank adaptor 8 at a front end of the rock drilling machine 6 for connecting the tool 7. The rock drilling machine 6 includes an impact device 9 and a rotating device 10. The rock drilling machine 6 may be moved on the feed beam 5 by means of a feed device 11. The rock drilling machine 6 is hydraulically operated and is connected to a hydraulic system HS. When initiating operation at cold temperatures, hydraulic fluid of the hydraulic system HS and the hydraulic rock drilling machine 6 needs to be pre-heated before the actual drilling process can be started. If not properly pre-heated, risk of damages to components of the impact device 9 occurs. Thus, the disclosed rock drilling rig 1 may be provided with the disclosed pre-heating arrangement.

(9) FIG. 2 illustrates a rock drilling machine 6, which is one type of rock treating machine Rtm. The rock drilling machine includes a body 12, an impact device 9, a rotating device 10, a flushing housing 13, a shank adaptor 8, a gear housing 14 mounted at a front end of the body 12. The impact device 9 includes an impact piston for generating impact pulses to the shank adapter 8. The piston moves in a reciprocating manner in the impact direction and return direction.

(10) FIG. 2 also shows a first pressure accumulator Pa1 and a second pressure accumulator Pa2, which are part of the hydraulic circuit of the impact device 9. The first pressure accumulator Pa1 may be a high pressure accumulator and the second pressure accumulator Pa2 may be a low pressure accumulator. The pressure accumulators Pa1 and Pa2 store and release pressurized hydraulic in accordance with the movements of the impact piston.

(11) FIG. 3 discloses by means of a simplified hydraulic diagram an arrangement wherein preheated hydraulic fluid can be circulated through an impact device 9 in a gentle limited manner when a warm-up mode WM is activated in a control unit CU. The hydraulic fluid can be preheated by means of a preheating device 15 which may include heating means arranged in connection with a tank 16, or alternatively the preheating device 15 may circulate the hydraulic fluid through a hydraulic throttle for heating it. The preheating device 15 may be controlled by means of the control unit CU. A hydraulic pump 17 pumps the hydraulic fluid to flow in a hydraulic circuit 18 through the impact device 9 and back to the tank 16. During the warm-up mode WM, the hydraulic fluid is conveyed via a feed channel 19 and by means of a control valve CV through a control element CE to a feed port 20 of the impact device 9. The control element CE limits feeding of the preheated hydraulic fluid so that percussion piston 21 executes it reciprocating movement at lower impact rate and pressures at a first pressure accumulator Pa1 and a second pressure accumulator Pa2 remain lower than their pre-charge pressures. The preheated hydraulic fluid flows inside the impact device 9 gently and does not overstress the structures being at low temperatures. The preheated hydraulic fluid passes hydraulic channels inside the impact device 9 and allow the heat of the preheated fluid to spread effectively therein. Finally, the hydraulic fluid flow is discharged through an outlet port 22. When a normal mode NM is connected, the preheating is terminated and the control valve CV directs the fluid flow through a channel 23 that passes the control element CE. In the normal mode NM, the fluid flow is not limited whereby the impact device 9 can operate at its designed impact rate and pressure accumulators Pa1 and Pa2 can receive greater pressures inside their fluid spaces. The first pressure accumulator Pa1 can assist movement of the percussion piston 21 in impact direction A and the second pressure accumulator Pa2 can assist movement in return direction B.

(12) Hydraulic connections of the control valve CV, the channel 23, and the control element CE can of course differ from the exemplary solution shown in FIG. 3.

(13) The control unit CU may be provided with a processor for executing one or more control programs including control principles for controlling at least the control element CE, control valve CV, and the preheating device 15. The control unit CU may be arranged to automatically control the disclosed arrangement, or alternatively in assistance with an operator. There may be a user interface UI for communication between the control unit CU and the operator. The control unit CU may receive temperature data from one or more temperature sensors TS. There may be one or more temperature sensors TS for sensing ambient temperatures, hydraulic fluid temperatures, and component temperatures. The temperature data received by the control unit CU can be taken into consideration when controlling the operation mode between the normal mode NM and the warm-up mode WM.

(14) The control unit CU may also be configured to control operation of the hydraulic pump 17. The control unit CU may provide the hydraulic pump 17 with a lower fluid flow and pressure request during the warm-up mode WM. The hydraulic pump 17 may be provided with adjustable displacement capacity, for example.

(15) FIG. 3 further discloses some embodiments of the control element CE mountable to the feed channel 19. The control element CE may be a throttle 24, either with a fixed orifice 24a or with an adjustable orifice 24b. Alternatively, the control element CE may be a proportional valve 25 with adjustable opening for throttling the fed pre-heated hydraulic fluid. The proportional valve 25 may be electrically controlled under control of the control unit CU.

(16) In the simplified hydraulic diagram of FIG. 3, no control valve is disclosed controlling operating cycle of the percussion piston 21 of the impact device 9. The control valve may be a sleeve structure surrounding the percussion piston 21, for example.

(17) FIG. 4 discloses two successive hydraulic actuators Pa1 and Pa2 arranged to a hydraulic circuit 18 of an impact device. A feed channel 19 is provided with a control element CE for limiting flow, pressure, or flow and pressure, of the fed pre-heated hydraulic fluid during a warm-up mode. The control element limits the feeding so that hydraulic fluid pressure Fp1 at a first pressure accumulator Pa1 is below first pre-charge pressure Pcp1 at a gas space GS of a first pressure accumulator Pa1 which is located first in downstream of the fed flow. The pressure Fp1 prevails in a fluid space Fs1 of the first pressure accumulator Pa1. At a second pressure accumulator Pa2 hydraulic fluid pressure Fp2 is lower since the hydraulic fluid flows through the impact device and hydraulic energy is utilized for making reciprocating movement of a percussion piston. The first pressure accumulator Pa1 is a high-pressure accumulator for storing pressurized hydraulic fluid for executing movement of the percussion piston in impact direction and the second pressure accumulator Pa2 is a low-pressure accumulator provided with second pre-charge pressure Pcp2, which is lower than the first pre-charge pressure Pcp1. The control element CE is configured to control the feeding of the pre-heated hydraulic fluid also so that hydraulic fluid pressure Fp2 at a second fluid space Fs2 of the second pressure accumulator Pa2 is lower than the second pre-charge pressure Pcp2. Thus, the pressures Fp1 and Fp2 do not cause movements to separating elements Se1 and Se2 whereby gentle heating can be provided for the pressure accumulators Pa1, Pa2.

(18) In some hydraulic circuits of impact devices, there may be only one pressure accumulator, or there may be three or even more pressure accumulators. However, the same principles for the feeding of the pre-heated hydraulic fluid applies then too.

(19) FIG. 5 discloses a pressure accumulator Pa connected to a hydraulic circuit 18, wherein pre-heated hydraulic fluid is fed through a control element CE controlled by a control unit CU. Pre-charge pressure can be set to a gas space Gs through a gas port 26. A separating element Se, such a membrane, can move 27 from a fluid space Fs towards the gas space Gs when pressure inside the fluid space Fs is greater than pressure inside the gas space Gs. This movement 27 of the separating element Se can be detected by sensing pressure Psg inside the gas space Gs. When the pressure increases in the gas space Gs, it means that the separating element Se has been moved. Pressure Psf prevailing inside the fluid space Fs can also be sensed. The control unit CU can take the gathered pressure data into account when controlling operation of the control element CE.

(20) FIG. 6 discloses a mobile work machine 27 provided with a boom 28 and a hydraulic rock breaking hammer 29 mounted to the boom 28. The rock breaking hammer 29 is a rock treating machine Rtm, which includes an impact device 9 configured to provide impact pulses for a breaking tool 30 for breaking rock material. The impact device 9 is connected to a hydraulic system HS which is provided with the disclosed arrangement for pre-heating the impact device 9 when needed.

(21) Although the present embodiment(s) has been described in relation to particular aspects thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred therefore, that the present embodiment(s) be limited not by the specific disclosure herein, but only by the appended claims.