Device for pressure monitoring

Abstract

A device for monitoring pressure within a gas space, which is filled with gas, preferably nitrogen, and/or is prestressed, of a pressure accumulator of a hydraulically driven percussive mechanism having a housing in which a piston is mounted, together with a display element which extends through the face surface of the housing, so as to be slidingly movable counter to the force of a spring, wherein the piston divides the housing into a pressure chamber and a spring chamber. The spring acts on a spring chamber-side working surface of the piston, and the pressure accumulator is at least indirectly operatively connected to the pressure chamber-side working surface of the piston, such that, in the event of a critical pressure within the pressure accumulator being undershot, the piston and the display element are displaced to such an extent that the display element protrudes out of the housing.

Claims

1. A device for monitoring a pressure, the device comprising: a hydraulically driven percussive mechanism comprising a pressure accumulator, the pressure accumulator having a gas space; a piston; a display element; a spring; and a housing, at least a portion of the piston being mounted in the housing such that the piston is slidingly movable counter to a force of the spring, wherein the display element is connected to the piston such that the display element extends through a face surface of the housing, wherein the piston divides the housing into a pressure chamber and a spring chamber, the spring acting on a spring chamber-side working surface of the piston, and the pressure accumulator is indirectly operatively connected to the pressure chamber-side working surface of the piston, such that, in an event of a critical pressure within the pressure accumulator being undershot, the piston and the display element are displaced to such an extent that the display element protrudes out of the housing, the spring chamber-side working surface being averted from the display element, the pressure chamber-side working surface facing toward the display element, the pressure chamber of the pressure accumulator being connected to a control surface of a spring-loaded pressure valve which can be transferred from a pass-through position into a blocking position counter to a force of a compression spring, the pressure chamber of the housing being connected via a check valve to the pressure line of the hydraulics and the pressure chamber of the housing is relieved of pressure to a tank in the pass-through position.

2. A device according to claim 1, wherein the display element has at least one marking which, after the undershooting of the critical pressure and displacement of the display element, appears and signals the undershooting of the critical pressure, the spring being located on one side of the piston, the hydraulically driven percussive mechanism being connected to the housing via a pressure line, the pressure line being connected to the housing at a housing location, the housing location being located on another side of the piston.

3. A device according to claim 2, wherein the display element has axially spaced-apart markings, wherein an appearance of said axially spaced-apart markings represents a measure for a value of the pressure.

4. A device according to claim 1, wherein the check valve is integrated in the spring-loaded pressure valve.

5. A device according to claim 1, wherein the check valve is arranged such that a flow of hydraulic fluid from the pressure line of the hydraulics via the check valve to the pressure chamber is possible, wherein a return flow from the pressure chamber is blocked via the check valve.

6. A device for monitoring a pressure, the device comprising: a hydraulically driven percussive mechanism comprising a pressure accumulator, the pressure accumulator having a gas space; a piston; a display element; a spring; and a housing, at least a portion of the piston being mounted in the housing such that the piston is slidingly movable counter to a force of the spring, wherein the display element is connected to the piston such that the display element extends through a face surface of the housing, wherein the piston divides the housing into a pressure chamber and a spring chamber, the spring acting on a spring chamber-side working surface of the piston, and the pressure accumulator is indirectly operatively connected to the pressure chamber-side working surface of the piston, such that, in an event of a critical pressure within the pressure accumulator being undershot, the piston and the display element are displaced to such an extent that the display element protrudes out of the housing, the spring chamber-side working surface being averted from the display element, the pressure chamber-side working surface facing toward the display element, the pressure accumulator being connected to a control surface of a spring-loaded pressure valve which can be transferred from a pass-through position into a one-way blocking position counter to a force of a compression spring, wherein the pressure chamber of the housing is relieved of pressure to a tank in the pass-through position and the pressure chamber of the housing is connected via a check valve to the pressure line of the hydraulics in the one-way blocking position.

7. A device according to claim 6, wherein the display element has at least one marking which, after the undershooting of the critical pressure and displacement of the display element, appears and signals the undershooting of the critical pressure, the spring being located on one side of the piston, the hydraulically driven percussive mechanism being connected to the housing via a pressure line, the pressure line being connected to the housing at a housing location, the housing location being located on another side of the piston.

8. A device according to claim 7, wherein the display element has axially spaced-apart markings, wherein an appearance of said axially spaced-apart markings represents a measure for a value of the pressure.

9. A device according to claim 6, wherein the check valve is integrated in the spring-loaded pressure valve.

10. A device according to claim 6, wherein the check valve is arranged such that a flow of hydraulic fluid from the pressure line of the hydraulics via the check valve to the pressure chamber is possible, wherein a return flow from the pressure chamber is blocked via the check valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic view of a hydraulic percussive mechanism according to a first embodiment;

(3) FIG. 2a is a schematic view of a hydraulic percussive mechanism according to a second embodiment;

(4) FIG. 2b is a schematic view of a hydraulic percussive mechanism according to a second embodiment; and

(5) FIG. 3 is a schematic view of a hydraulic percussive mechanism according to a third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) Hydraulically operated percussive mechanisms 1 are used in mounted implements such as hydraulic hammers, drilling hammers etc., wherein the mounted implements are mounted on carrier vehicles, such as for example mobile excavators, and are connected to the hydraulic system 2 thereof via a pressure line 3 and a return line 4. On the carrier vehicle there is provided a switching valve which can break or establish the connection between the pump of the carrier vehicle and the pressure port of the percussive mechanism and between the tank of the carrier vehicle and the return port, in order to deactivate or activate the percussive mechanism.

(7) Percussive mechanisms have a percussive piston 5 which has one or more hydraulic drive surfaces 6, 7, at least one of which can, by way of a valve 8 associated with the percussive mechanism, be connected alternately to a return line, which is at low pressure, to the tank 9 of the carrier vehicle or via a pressure line, which is at high pressure, to the pump 10 of the mounted implement, such that the percussive piston 5 performs oscillating movements along its longitudinal axis. During normal operation, at the end of its movement in one movement direction, the percussive piston strikes a tool 11, wherein the tool is a chisel, an adapter for piledriving or pipe driving, or an anvil arranged between the percussive piston and the tool.

(8) Hydraulically operated percussive mechanisms have, in some cases, a pressure accumulator 12 in the form of a piston accumulator in order to store kinetic energy of the percussive piston. The upper, cylindrical end 13, situated opposite the tool, of the percussive piston projects into a gas-filled gas space 14 of the pressure accumulator, wherein a seal (not illustrated) which bears against the end of the piston prevents an escape of the gas along the percussive piston.

(9) As the piston moves in the direction of the gas space during the return stroke, the end of the piston displaces gas within the gas space, which thus decreases in size, leading to an increase in the gas pressure. The gas exerts a force on the end of the piston, said force increasing as the gas volume decreases in size. Said force is utilized to accelerate the piston 5 in a direction of movement toward the tool 11.

(10) During operation, there are thus three characteristic piston positions which can be associated with a respective gas pressure. For example, if a hydraulic hammer which has a percussive mechanism 1 is raised or set down horizontally, its percussive piston is situated in the lowermost position, the rest position, in which the percussive piston bears against a piston stop 16 of the percussive mechanism housing and in which the gas pressure in the piston accumulator assumes its lowest value. Every time the processing of a piece of material using a hydraulic hammer is ended and the operation of the percussive mechanism is stopped, in order to position the chisel 11 on a different piece of material 100, the percussive piston assumes said rest position. If the chisel, as illustrated in FIG. 1, is pressed with its tip against material, the chisel is pushed into the housing of the percussive mechanism until it comes to rest against a stop 15. In this case, the percussive mechanism is likewise pushed in the upward return stroke direction, in the direction of the gas space, and assumes the impact position, and the gas pressure in the piston accumulator assumes a value higher than that in the rest position. When the percussive mechanism is activated, the percussive piston 5 is then hydraulically moved further in the return stroke direction until it reaches its upper reversal point, at which the gas pressure assumes its highest value, wherein the position at the upper reversal point is dependent on the usage conditions of the percussive mechanism 5 and the operating pressure and the gas fill pressure in the piston accumulator, and may vary slightly.

(11) The percussive mechanism illustrated in FIG. 1 has a gas pressure indicator device 50, in the case of which the gas pressure, after reaching or undershooting a particular gas fill pressure, outputs a signal by virtue of a bar 23 being deployed out of a housing and protruding beyond the housing surface 29. The bar 23 provides a display element 23.

(12) The gas pressure indicator device 50, which is composed of a piston 22 guided in movable fashion in a housing equipped with a bore 21, has a bar 23 connected fixedly in terms of motion to the piston and has a spring 24. The piston divides the bore 22 into two chambers, in which in each case one piston surface 25, 26 is situated. A first piston surface 26 (pressure chamber-side working surface) is connected by way of a line 27 to the gas space 14 of the pressure accumulator 12, such that the gas pressure prevailing in the gas space acts on the piston surface 26 and exerts on the piston a gas force which can displace the latter toward the left, in the direction away from the housing surface 29. The space surrounding the second piston surface 25 is either connected to the atmosphere or sealingly closed off and filled with air at low pressure, such that the pressure on said surface does not have a significant influence on the movement of the piston. A spring 24 bears against the (spring chamber-side) working surface 25 of the piston, and exerts on the piston a force acting counter to the gas force.

(13) The surface area of the pressure chamber-side working surface 26 and the force of the spring 24 are configured such that, during the operation of the percussive mechanism, and in the presence of an adequate gas fill pressure in the gas space 14, the gas pressure is sufficient to displace the piston into its left-hand end position and hold it there, in which position the spring length is at its shortest and the bar is retracted into the housing to such an extent that it no longer protrudes beyond the housing surface 29.

(14) Only when the percussive mechanism is deactivated and the percussive piston 5 assumes its lowermost rest position, in which the percussive piston bears against a stop 16 of the percussive mechanism housing and in which the gas pressure is to be measured, does the volume in the gas space assume its greatest value and the gas pressure assume its lowest value within the range of the possible percussive piston movement.

(15) When the percussive piston is situated in the rest position, if the gas pressure is below the predefined target value, the gas force falls below the spring force, whereby the piston is displaced to the right, and the bar 23 is likewise displaced and emerges from the housing and protrudes beyond the housing surface 29. The lower the gas pressure, the further the bar protrudes beyond the housing surface. In the position of the percussive piston illustrated in FIG. 1, it would be necessary, contrary to the illustration, for the bar to be retracted fully into the housing, as the gas pressure always rises in percussive piston positions above the rest position and always lies above the target value when the gas fill pressure is correctly set.

(16) A signal is output to the user, by way of the appearance of the bar, only when the percussive piston is situated in the rest position, in which the gas pressure is to be meaningfully measured and the gas pressure has fallen below the required target pressure.

(17) The risk of the percussive mechanism being operated with an excessively low gas pressure in the accumulator, which can lead to performance losses and damage to the components of the percussive mechanism, is greatly reduced by way of this embodiment, as the signal of the protruding bar is clearly visible to the user, that is to say if the bar appears, the gas fill pressure has fallen below the target value and the gas space must be replenished with gas.

(18) The embodiment of the gas pressure indicator device 70 for a percussive mechanism illustrated in FIG. 2a differs from that illustrated in FIG. 1 in that the space 75 in which the first piston surface 26 is situated is not connected to the gas space 14 of the pressure accumulator 12 but is connected by way of two valves 71, 72 either to the pressure line 3 or to the tank line 4 in a manner dependent on the position of the valves. The gas pressure acts via a line 27 on a control surface 73 of a pressure switching valve 71, wherein the pressure switching valve assumes a blocking position when the gas pressure reaches or exceeds the required gas fill pressure. The required gas fill pressure, at which the valve switches into the blocking position, is defined by the force of a spring 74, said force being directed counter to the gas force acting on the control surface 73. The pressure switching valve is connected by way of one port to the space 75 and by way of the other port to the tank line 4. If the valve is situated in the blocking position, as illustrated, the connection between the space 75 and the tank line is blocked, and oil cannot flow out of the space 75 to the tank 9. A check valve is arranged between the space 75 and the pressure line 3 such that pressurized oil can flow from the pressure line via the check valve into the space 75, that is to say onto the surface 26, but not in the opposite direction.

(19) If, by activation of the pump 10, the percussive mechanism is supplied with pressurized oil via the pressure line 3, the percussive piston performs repeated working cycles and impacts against the tool 11. Oil flows out of the pressure line via the check valves 72 into the space 75 and exerts on the piston 22 an oil force which opposes the spring force. The spring is configured such that the oil force exceeds the spring force and the piston is displaced to the left into the initial position, such that the spring is compressed and the bar connected to the piston likewise moves to the left, and the right-hand end of the bar no longer protrudes beyond the housing surface 29 and is no longer visible. If the gas fill pressure in the gas space 14 corresponds to or is higher than the required gas fill pressure, the pressure switching valve assumes the blocking position and the oil cannot flow out of the space 75, that is to say the piston and the bar remain in the initial position, in which the bar is not visible. Only if the gas pressure undershoots the required gas fill pressure is the pressure switching valve switched into the pass-through position, allowing oil to flow out of the space 75 to the tank via the pressure switching valve. This has the result that the pressure in the space 75 falls, and the spring force of the spring 24 displaces the piston and the bar to the right, whereby the bar protrudes beyond the housing surface 29 and appears, which signals to the operator that the gas fill pressure has been undershot. At the same time, with correspondingly large dimensioning of the lines and of the valves, pressurized oil can flow out of the pressure line via the check valve and the pressure switching valve to the tank, such that the pressure in the pressure line falls to such an extent that the percussive mechanism comes to a standstill and no longer imparts a percussive action. In this way, operation with an excessively low gas fill pressure is prevented. The pressure switching valve may be equipped with a seat valve, preferably with an integrated check valve, such that in the blocking position, the connection between the space 75 and the tank is shut off in a leakage-free manner. In this way, the indicator, that is to say the piston 22 and the bar 23, would maintain their position for as long as the gas pressure does not undershoot the target value, even over a relatively long period of time. The control surface 73 on the pressure switching valve is sealed off by way of a seal or elastic diaphragm such that no gas can escape from the system via the control surface.

(20) As an alternative to the embodiment as per FIG. 2a, it is possible, as illustrated in FIG. 2b, for the pressure switching valve 71 to be connected to the pressure line 3 rather than to the tank line 4. When the percussive mechanism is deactivated, which is necessary in order to bring the percussive piston into the lowermost position, which is required for the measurement of the gas pressure, the pressure line is unpressurized owing to the pump-side valve controller (not illustrated) or as a result of leakage at said controller, such that in this state, oil can flow out of the space 75 when the pressure switching valve has been switched into the open position as a result of undershooting of the required gas fill pressure. When oil flows out of the space 75 by the pressure switching valve, the spring 24 displaces the piston 22 and the bar 23 to the right, whereby a signal is output to indicate that the gas fill pressure has been undershot.

(21) Furthermore, the check valve 72, which is arranged between the space 75 and the pressure line, is integrated into the pressure switching valve 71 such that, in the illustrated blocking position, when the percussive mechanism is deactivated and the pressure line is unpressurized, no oil can flow out of the space 75 to the pressure line, but during the operation of the percussive mechanism, when measurement of the gas pressure is not expedient, oil can flow out of the pressure line into the space 75 in order to displace the indicator into its initial position, in which the piston and bar assume their left-hand position.

(22) The gas pressure acts on the piston of the indicator no longer directly but indirectly, and controls the pressure switching valve, which defines the end position of piston and bar. The piston and the bar no longer assume intermediate positions but can assume only two positions, specifically the initial position, in which the piston and bar are displaced to the left, and the signal position, in which the bar protrudes beyond the housing surface and is clearly visible, as a change in gas pressure to a level above a threshold value no longer directly leads to a corresponding displacement of the piston and of the bar. If the gas pressure exceeds the required gas fill pressure, the pressure switching valve switches and leads to a considerable decrease in pressure in the space 75, triggering the displacement of the piston and of the bar from one position into the other position.

(23) The percussive mechanism illustrated in FIG. 3 is equipped with a gas pressure indicator device 60 which differs from the embodiment illustrated in FIG. 1 in that the surface 26 of the piston 22 is connected to the gas space 61 of the hydraulic accumulator 62. The hydraulic accumulator can store pressurized oil of the hydraulic system. The gas space of the hydraulic accumulator is separated from an oil space 64 by way of an elastic separating element 63. The oil space is connected to the pressure line 3 directly or indirectly via a throttle or a valve and a line 65. For filling purposes or in order to release the gas charge, corresponding fittings such as for example hoses and pressurized gas bottles can be connected to the gas space 61 by way of a valve which is connected to the gas space. If an operating pressure higher than the gas pressure within the gas space prevails in the pressure line, oil flows into the oil space and displaces the separating element in the direction of the gas space, whereby the volume of the oil space is increased and that of the gas space is decreased. In this way, the gas is compressed up to a pressure which corresponds approximately to the pressure of the oil. Thus, when the oil demand of the percussive mechanism 1 is low, the oil that is delivered by the pump 10 can be stored in the hydraulic accumulator in order to reduce the pressure increase in the pressure line, and when the demand of the percussive mechanism is high, oil can be released from said hydraulic accumulator into the pressure line in order to reduce the pressure drop in the pressure line. Intense pressure fluctuations and pressure peaks in the pressure line are thus prevented, performance is increased owing to the more constant operating pressure, and damage to components owing to intense pressure changes is prevented.

(24) If the percussive mechanism has been deactivated and pressure built up by the pump 10 no longer prevails in the pressure line 3, it is also the case that pressure no longer prevails in the oil space 64 of the accumulator, and the gas pressure displaces the separating element downward, toward the oil space, until the gas space has assumed its maximum possible volume and the oil space has assumed its minimum possible volume. In this state of the hydraulic accumulator, the gas fill pressure of the gas space can be measured. If an adequate gas pressure (target fill pressure) prevails in the gas space, the gas pressure effects a gas force acting on the surface 26 of the piston. The surface 26 and the spring 24 arranged on the opposite side of the piston, which spring generates a spring force opposed to the gas force, are configured such that the gas force compresses the spring to such an extent that the piston assumes its right-hand end position, in which the piston is fully retracted into the housing. If the gas pressure were to lie below the required target gas fill pressure, the spring force would exceed the gas force generated by the gas, and the piston would be displaced to the right, such that the bar is deployed out of the housing and appears clearly to the user, thus signaling to the user that the required gas fill pressure has been undershot and replenishment of gas is necessary. Since the gas fill pressure is lower than the oil pressure prevailing in the pressure line during the operation of the percussive mechanism, it is the case that, during operation, oil flows into the oil space, displaces the separating element and thus reduces the volume of the gas space, whereby the gas pressure increases to approximately the level of the oil pressure. In the presence of adequate gas fill pressure, the piston and the bar remain in their left-hand end positions during operation. The pressure indicator devices as per FIGS. 1, 2a and 2b may, like that in FIG. 3, be used for monitoring the gas fill pressure of a hydraulic accumulator.

(25) The gas pressure indicator device may be arranged directly on the housing of the percussive mechanism or on a component connected to the housing of the percussive mechanism, such as a valve block, or on the accommodating housing surrounding the percussive mechanism.

(26) The gas space or those components of the gas pressure indicator device which are connected to the gas space of the accumulator may be equipped with valves and connection means in order for a manometer or other pressure indicator devices for determining the gas pressure to additionally be connected, or in order for the gas pressure to be reduced or released through a discharge of the gas or for the gas pressure to be increased through a supply of gas into the gas space. Said valves and connections are not illustrated in the exemplary embodiments but are known from known filling and testing devices for pressure accumulators of percussive mechanisms.

(27) The bar may be equipped with several markings which denote different gas pressures.

(28) Since, in the case of a constant volume, the gas pressure changes with changing gas temperature, the bar may have provided on it multiple markings which denote the attainment of the target gas pressure at different temperatures. In this way, it is possible for the gas pressure to be indicated even in the presence of gas temperatures which deviate from a predefined measurement temperature that is to be adhered to.

(29) The position of the bar of the piston may be detected by way of electronics components for the purposes of triggering a signal, via an electrical signal transmission means, to other locations, for example to the carrier vehicle, or for the purposes of intervention into the hydraulic control of the percussive mechanism such that, in the event of undershooting of the target gas pressure, the hydraulic supply to the percussive mechanism is shut off or the operation of the percussive mechanism is stopped by intervention into the hydraulic control.

(30) Contrary to the embodiments described above, in which, in the right-hand end position of the piston, the bar is fully retracted into the housing and is not visible to the user, the indicator may also be designed such that, in said end position, a part of the bar protrudes beyond the housing surface but said part is distinguished, by way of a marking, so as to clearly differ from that region of the bar which additionally appears when the piston and the bar are moved to the right in the direction of the other end position.

(31) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.