EP0472982B1 - Hydraulically operated impact drilling device, especially for boltdrilling - Google Patents

Abstract

In order to prevent overstressing of the transmission elements (drill sleeve and insertion end) when using percussion drilling devices, especially for drilling anchor holes, it is proposed to equip the pressure line (24) for the supply of the drive medium to the percussion piston (3) with a first control member (25) which reduces the working pressure driving the percussion piston - after a limit value of the rotary-mechanism working pressure is exceeded - as the latter rises. In addition, there is a second control member (42), via which the push-out pressure against which the percussion piston (3) can be returned counter to the percussion direction (arrow 21) can be changed, after a limit value has been exceeded, as a function of the size of one of the working pressures - namely of the percussion-mechanism or rotary-mechanism working pressure - in such a way that the size of the push-out pressure increases or decreases with increasing working pressure. <IMAGE>

Description

The invention relates to a hydraulically operated percussion drilling device, in particular for anchor hole drilling, with a percussion piston and a control which alternately switches its direction of movement and with a tool insertion end which is actuated by the percussion piston and is displaceable in the longitudinal direction and is driven by a rotating mechanism.

An important area of application for rotary impact drilling devices is the so-called anchor hole drilling, in which work is carried out with large drilling diameters (possibly with a double rod consisting of drill pipes arranged one inside the other) and large drilling depths.
It is problematic that with the percussion rotary drilling devices suitable for such stresses, the two working units (percussion mechanism and slewing gear) can each have the required high output, but that a simultaneously occurring high decrease in power at both working units overloads the transmission elements of the rotating mechanism (drill sleeve and insertion end). has the consequence. When drilling with a high slewing rate, there is also the risk that the drill string will become stuck due to additional resistance - caused by changes in the drilling material (for example, through soft, hard or tough layers) or by jamming; such an incident either takes a considerable amount of time to loosen the drill pipe, possibly damage it or lose it.

For the area of application in question, it is therefore necessary to reduce the individual impact energy of the rotary impact drilling device without a sharp drop in the number of impacts if the output of the rotating mechanism or its torque increases beyond a predetermined limit value. Too much a drop in the number of blows generated by the striking mechanism would adversely affect the vibration behavior of the drill pipe, which is necessary for overcoming the casing friction with the drilling material.

So far, designs of hydraulically operated drilling rigs and impact devices are known in which the single impact energy can be changed while the number of impacts is changed by a control pressure supplied from outside (DE-PS 26 58 455). The reduction of the individual impact energy takes place by a step-wise shortenable shortening of the percussion piston stroke, combined with an increase in the number of impacts. Applied to rotary impact drilling devices, this type of control has the disadvantage that the increased number of impacts increases wear and friction welding on the transmission elements already mentioned, which are caused by a high surface pressure in conjunction with a large number of smallest movements in the axial direction. Furthermore, the step-like switching to shorten the working stroke has an unfavorable effect on the drilling process.

The document US-A-4 440 236 describes a generic percussion drilling device. As control elements of interest in this context, this has pressure limiting valves which can assume a closed or an open position. The known device is designed in such a way that the working pressure of the striking mechanism is influenced indirectly as a function of the working pressure of the rotating mechanism, namely via the pressure difference between the feed line and the return line of the associated feed unit. The pressure limiting valve, which may switch off the working pressure of the striking mechanism, is connected directly to the lines of the feed unit already mentioned via control lines; the latter is assigned a further pressure relief valve, which may reduce the pressure difference in the lines of the feed unit.

The invention has for its object to design a hydraulically operated rotary hammer drilling device in such a way that - after exceeding a predetermined limit - the performance of the hammer mechanism is continuously reduced depending on the load on the rotating mechanism; at the same time, the impact rate of the striking mechanism is influenced in such a way that it drops less than would otherwise be the case.

The object is achieved by a rotary impact drilling device which has the features of claim 1.

The basic idea of the invention is to additionally equip the rotary impact drilling device with two throttle valves, via which the impact of the impact mechanism is reduced by influencing the working pressure driving the impact piston or by influencing the push-out pressure against which the impact piston can be traced against the direction of impact, whose impact rate changes leaves. Specifically, the pressure line for supplying the drive means to the percussion piston is equipped with a first throttle valve, which reduces the working pressure driving the percussion piston - after a limit value of the slewing gear working pressure has been exceeded - directly and more and more with its rise. The second throttle valve, which, like the first throttle valve, influences the size of an outlet cross section connected to a return line, changes the push-out pressure against which the percussion piston is returned against the direction of impact, after a limit value has been exceeded, either as a function of the size of the striking mechanism working pressure, that with increasing hammer mechanism working pressure the size of the push-out pressure increases or is changed in dependence on the size of the slewing gear working pressure such that the size of the push-out pressure decreases with increasing slewing gear working pressure.
The smaller return stroke area of the percussion piston, which causes the return stroke movement, is constantly subjected to working pressure and the control alternately switching the direction of movement of the percussion piston is designed as a control slide which, depending on the position of the percussion piston, alternately connects its larger working stroke area in the impact direction to the pressure line and a return line , wherein the second throttle valve is operatively arranged in the connecting channel between the controller and the return line.

In order to be able to influence the operation of the percussion drilling device without great effort and delicately, at least the first throttle valve should be designed in such a way that its limit value setting can be influenced by changing the bias of its return spring (claim 2).

In a further development of the subject matter of the invention, each throttle valve has at least one piston which is pushed against a restoring force under pressure under the working pressure in question (claim 3).
The first throttle valve is preferably equipped with a control piston which can be displaced against a restoring element and on which a throttle piston which limits the outlet cross section is resiliently supported (claim 4). The restoring element for the control piston can in particular be designed as a mechanically effective spring element.

The displacement of the pressurized control piston has the consequence that the preload force acting on the throttle piston drops: The working pressure limit value, which can move the throttle piston against the preload and thus open an outlet cross-section, is accordingly lower. In a preferred embodiment of the first throttle valve, the biasing force of the restoring element for the control piston is adjustable (claim 5). The control piston therefore only executes a corresponding movement when the working pressure of the slewing gear acting on it generates an adjusting force which exceeds the preloading force.

Depending on whether the second throttle valve is actuated via the slewing gear or the striking mechanism working pressure, this may influence the push-out pressure in such a way that its size increases with decreasing slewing gear working pressure or decreases with decreasing striking mechanism working pressure and accordingly the number of strokes (with increased ejection pressure) decreases or (with lowered ejection pressure) increases.
If both throttle valves are adjusted directly as a function of the slewing gear working pressure, its rise above a predetermined limit value leads in parallel to a lowering of the striking mechanism working pressure and a relative increase in the number of blows.
In another embodiment, the lowering of the hammer mechanism working pressure results in a relative increase in the number of strokes.

The design and the resulting mode of operation of the throttle valves must be adapted to the expected operating conditions, taking into account the design of the rotary hammer drilling device.

• das erste Drosselventil wird erst wirksam, falls die Belastung des Drehwerks 50 bis 80 % seiner Nennleistung überschreitet;
• unter Einwirkung des ersten Drosselventils ist die Schlagwerkleistung höchstens um 50 % seiner Nennleistung absenkbar und
• das Absenken der Schlagwerkleistung mittels des ersten Drosselventils hat aufgrund der Einwirkung des zweiten Drosselventils eine relativ höhere Schlagzahl zur Folge als ohne seine Einwirkung.

Unless special circumstances necessitate changes, the object of the invention can have the following features with regard to the design of the two throttle valves:

• the first throttle valve only becomes effective if the load on the slewing gear exceeds 50 to 80% of its nominal output;
• under the action of the first throttle valve, the impact power can be reduced by a maximum of 50% of its nominal output and
• lowering the percussion power by means of the first throttle valve results in a relatively higher number of blows due to the action of the second throttle valve than without it.

Fig. 1

stark schematisiert einen Teilschnitt durch eine hydraulisch betriebene Schlagdrehbohrvorrichtung, die als Hauptbestandteile ein Schlagwerk und ein mit diesem zusammenwirkendes Drehwerk aufweist,

Fig. 2

in gegenüber Fig. 1 vergrößertem Maßstab einen Teilausschnitt des Schlagwerks mit einem andersartig ausgebildeten ersten Drosselventil und

Fig. 3

in gegenüber Fig. 1 vergrößertem Maßstab einen Teilausschnitt des Schlagwerks mit einem andersartig ausgebildeten zweiten Drosselventil.

The invention is explained in detail below with reference to several exemplary embodiments shown in the drawing.
Show it:

Fig. 1

highly schematic a partial section through a hydraulically operated rotary hammer drilling device, which has a hammer mechanism and a rotating mechanism interacting with it as main components,

Fig. 2

in an enlarged scale compared to FIG. 1, a partial section of the striking mechanism with a differently designed first throttle valve and

Fig. 3

on a larger scale than in FIG. 1, a partial section of the striking mechanism with a differently designed second throttle valve.

The main rotary drilling device has a striking mechanism 1 with a housing 2, a striking piston 3 which can be reciprocated therein and a control 4 as well as a rotating mechanism 5 with one on the Housing 2 flanged slewing gear housing 6 and an attached hydraulic motor 7, with which a drive pinion 8 supported in the slewing gear housing 6 can be driven in both directions of rotation. The slewing gear housing further receives - supported on two axial bearings 9 and 10 - a counter bearing 11 designed as a gearwheel, in whose toothing 11a the drive pinion 8 engages.
An insertion end 12 for a drilling tool, not shown, is movably connected to the thrust bearing 11 via a torque connection in the form of a spline profile 12a; the freedom of movement of the insertion end with respect to the slewing gear housing 6 and the counter bearing 11 is limited by a paragraph 12b. The insertion end 12, set in rotation under the action of the hydraulic motor 7, the drive pinion 8 and the counter bearing 11, transmits the single impact energy generated by the percussion piston 3 to the drilling tool, not shown; the percussion piston tip 1a, the impact surface 12c of the insertion end 12 interacting with this and the surfaces of the spline profile 12a are exposed to considerable stress.

Within the housing 2 there are three spaces separated from each other by the percussion piston, namely (viewed in sequence from the percussion piston tip 1a) a pressure space 13, a reversing space 14 and a space 15 into which the rear end of the percussion piston 1b protrudes more or less. The latter space is kept depressurized in the illustrated embodiment; if necessary, however, it can also be filled with compressed gas. For sealing against the environment, the housing 2 is equipped on the side of the percussion piston tip 1a with two sealing elements 16 and in the area between the spaces 14 and 15 with two sealing elements 17, 18.
The range of motion of the percussion piston 3 is limited by an annular projection 1c located in the pressure space 13, which protrudes on the end of the percussion piston 1b facing side merges into a narrower cylinder section 1d. In the direction of the percussion piston tip 1a, the annular projection 1c has a truncated cone section 1e, which enables the formation of a pressure cushion which brakes the percussion piston movement.
The diameter of the cylinder section 1d is such that it can shut off the bore section 19 against the pressure chamber 13, which adjoins the former in the direction of the piston end 1b.

The percussion piston 3 is pressurized under the action of the known control 4 in such a way that it alternately executes a working stroke in the direction of impact (arrow 20) or a return stroke in the opposite direction (arrow 21). The smaller return stroke area 1f effective in the direction of the return stroke results from the difference in area between the cylinder section 1d and the percussion piston section 1h on the opposite side of the ring projection 1c.
The control essentially consists of a control slide 22 with a through bore 22a, which is held in a cylinder chamber 23 so that it can be pushed back and forth in the longitudinal direction and is connected via this to a pressure line 24 and via its extension 24a to the pressure chamber 13; the pressure line 24 is acted upon by a pressure oil source, not shown, during operation with the working pressure p _S provided for the striking mechanism 1.
The pressure line 24 with its extension 24a is connected to a return line 26, which is kept pressureless, with the interposition of a first throttle valve 25 to be described; A leakage channel 27 also opens into this, which drains leakage oil from the area between the two sealing elements 17, 18.

Depending on the position of the control slide 22 within the cylinder chamber 23, the reversing chamber 14 can be connected to the return line 26 via a reversing duct 28, the cylinder chamber 23 and a connecting duct 29 or to the pressure line 24 via the components 28 and 23.

The pressurization of the percussion piston 3 is designed in a manner known per se such that its return stroke surface 1f is acted upon by working pressure via the pressure line 24, 24a. In contrast, the larger working stroke area 1g which triggers the working stroke is only temporarily subjected to working pressure when the control slide 22 moves (by executing a movement to the left) into the other end position, not shown. The movement of the control slide 22 to the left has the result that the connection between the channels 28 and 29 is interrupted by the section 22b and at the same time the reversing channel 28 is connected to the pressure line 24.

The control slide 22 is dimensioned with regard to the size of its two end faces 22c, 22d and the other two ring faces in such a way that it assumes the return stroke position shown in FIG. 1, as long as the annular face 22e adjacent to the end face 22c (as shown in the drawing) via the channel 30 ) is sufficiently pressurized.
As soon as - depending on the position of the percussion piston 3 - the pressure in the channel 30 drops, the control slide 22 moves under the action of the then greater compressive force on the end face 22d to the left with the already mentioned consequence that by acting on the reversing chamber 14 with the working pressure the working stroke is triggered in the direction of arrow 20. The changeover of the control slide 22 is brought about by the fact that in the course of the return stroke movement Cylinder section 1d subsequent annular groove 1i connects the channel 30 to the return line 26 via an outlet channel 50; this entails the pressure drop already mentioned on the ring surface 22e.

The already mentioned first throttle valve 25 for influencing the operating behavior of the rotary impact drilling device has a control piston 31 which is held in abutment against a stop surface 33 under the action of a prestressed return spring 32. An essentially frustoconical throttle piston 35 is supported on the narrower front section 31a of the control piston with the interposition of a spring 34; its guide consists of a guide pin 35a held movably in the housing 2.

As long as the throttle piston 35 bears against the wall of the bore section 36 under the action of the spring 34, there is no outlet cross section, ie there is no connection between the pressure line 24, 24a and the return line 26.
The stop surface 33 is part of an annular chamber 37, into which a control line 38 opens. This in turn is connected via a changeover valve 39 to the line (for example line 7a) which is subjected to the working pressure for the operation of the hydraulic motor 7. This can therefore work in both directions of rotation without influencing the function of the control line 38.
In order to rule out the build-up of an undesirable back pressure in the area of the return spring 32, the chamber 40 receiving the parts 31 and 32 is connected to the return line 26 via a relief channel 41.

If - due to a corresponding load on the slewing gear 5 - the associated working pressure also in the Control line 38 reaches a limit value which is greater than the restoring force generated by the restoring spring 32, the control piston 31 is moved away from the stop surface 33, as a result of which the spring force acting on the throttle piston 35 changes. This releases an outlet cross section between the lines 24a and 26 and thus brings about a reduction in the working pressure which reduces the performance of the striking mechanism 1. The subject of the invention thus responds to an increased decrease in power at the rotating mechanism 5 by reducing the impact power and in this way prevents excessive stress in the area of the transmission elements, ie in the area of the drill sleeve and the insertion end.

In order to be able to additionally influence the number of blows of the hammer mechanism 1, a second throttle valve 42 is provided. This consists of a control piston 43 which, in the rest position, bears against a stop surface 45 under the action of a prestressed return spring 44; in the area of which the control piston 43 can be acted upon by a control line 46 connected to the pressure line 24.
On the side facing the return spring 44, the control piston 43 has a throttle pin 43a with a frustoconical end section 43b, which more or less closes the cross section of the connecting channel 29.
On the side opposite the return spring 44, the chamber 47 receiving the control piston 43 is connected to the return line 26 via a relief channel 48 and is thus relieved of pressure.

Since the position of the end section 43b with respect to the connecting channel 29 determines the size of the outlet cross section in the return line 26 and thus the push-out pressure which the percussion piston during the return stroke must overcome, by moving the control piston 43 depending on the working pressure for the striking mechanism 1 against the action of the return spring 44, the number of strokes of the striking piston 3 can be changed. If the working pressure in the pressure line 24 exceeds a predetermined value (due to the prestressing of the return spring 44), the previously mentioned outlet cross section in the connecting channel 29 is reduced via the control piston 43, as a result of which the push-out pressure increases during the return stroke and the number of strokes decreases.
Starting from an operating position of the control piston 43, which is caused by a working pressure above the associated limit value, a drop in the working pressure leads to an increase in the outlet cross section at the connecting channel 29 and thus to a relatively lower drop in the number of strokes.

The interaction of the two throttle valves 25 and 42 thus ensures that a reduction in the impact mechanism performance caused by the rotating mechanism working pressure may result in a desired, less severe reduction in the number of strokes, since a comparatively higher one automatically occurs due to the reduced impact mechanism working pressure Sets stroke rate.

In the embodiment of the first throttle valve 25 according to FIG. 2, the biasing force exerted by the return spring 32 on the control piston 31 can be changed continuously. For this purpose, the component 32 is supported on the housing 2 by means of a threaded bushing 49 with an external hexagon head 49a.
By turning the threaded bushing 49 in the direction of the control piston 31 bearing against the stop surface 33, the pretension of the return spring 32 can be increased continuously, as a result of which the working pressure limit value rises, after which the throttle valve 25 responds.

In the embodiment in question, the components 31 and 49 for receiving the return spring 32 are partially hollow; the relief channel 41 lies in the area between the named components 31 and 49.

The second throttle valve 42 shown in FIG. 3 is controlled - in contrast to the embodiment according to FIG. 1 - after a limit value has been exceeded (predetermined by the pretension of the return spring 44) as a function of the working pressure for the slewing gear; The control piston 43 is accordingly connected to the control line 38, as is the first throttle valve 25 (shown in FIG. 1).
The return spring 44 is located on the side of the control piston 43 facing away from the throttle pin 43a, which is partially hollow.
The embodiment in question can - based on the design of the first throttle valve according to FIG. 2 - be easily changed by installing a threaded bushing in such a way that the biasing force of the return spring 44 can also be adjusted.
The connection of the control piston 43 to the control line 38 has the result that both throttle valves are actuated immediately after a predetermined limit value has been exceeded as a function of the size of the slewing gear working pressure.

The throttle valve 42 is designed and switched such that a sufficient pressure increase in the control line 38, the displacement of the control piston 43 counter to the action of the return spring 44, an increase in the outlet cross section in the connecting channel 29 and thus a reduction in the push-out pressure (with a relative increase in the number of strokes) has the consequence.

The advantage achieved by the invention is that under certain conditions the percussion performance is influenced as a function of the load on the slewing gear and at the same time the ejection pressure to be overcome by the percussion piston is changed in such a way that the number of impacts is not undesirable even when the percussion performance is reduced drops sharply. The rotary impact drilling device designed in this way is particularly suitable for anchor hole drilling and applications with comparable working conditions.

Claims (5)

1. Hydraulically operated impact drilling device, in particular for bolt drilling, with a percussion piston (3) and a control means (4) alternately switching over its direction of movement, and with a tool chuck (12), which is subjected to the impact of the percussion piston, is displaceably held in its longitudinal direction and is driven by means of turning gear (5), characterised in that the pressure line (24) for the supply of the drive medium to the percussion piston (3) is fitted with a first throttle valve (25), which increasingly reduces the working pressure driving the percussion piston - after a limit value of the working pressure of the turning gear has been exceeded - directly on its increase; and that a second throttle valve (42) is provided, which, like the first throttle valve (25), influences the size of an outlet cross-section (35, 36 or 29, 43b) connected to a return pipe (26) and by means of which the exhaust pressure, against which the percussion piston (3) is returned contrary to the direction of impact (arrow 20), is changed after a limit value has been exceeded either in dependence on the magnitude of the working pressure of the impact device in such a way that as the working pressure of the impact device increases, the magnitude of the exhaust pressure increases, or is changed in dependence on the magnitude of the working pressure of the turning gear in such a way that as the working pressure of the turning gear increases, the magnitude of the exhaust pressure decreases; that the smaller return stroke surface of the percussion piston (3) effecting the return stroke movement is constantly subjected to working pressure and the control means (4) is constructed as a control valve (22), which - dependent on the position of the percussion piston (3) - connects the larger working stroke surface acting in the direction of impact alternately to the pressure line (24) and to a return pipe (26); and that the second throttle valve (42) is functionally arranged in the connection duct (29) between the control means (4) and the return pipe (26).
2. Device according to Claim 1, characterised in that the limit value adjustment of at least the first throttle valve (25) may be influenced by changing the initial stress of its restoring spring (32).
3. Device according to Claim 1, characterised in that each throttle valve (25, 42) has at least one piston (31 or 43) which on application of pressure is shifted against the restoring force of a restoring spring (32 or 44).
4. Device according to at least one of Claims 1 to 3, characterised in that the first throttle valve (25) has a control piston (31), which may be shifted against a restoring element (32) and on which a throttle piston (35) also bordering the outlet cross-section of the hole section (36) is resiliently supported.
5. Device according to Claim 4, characterised in that the initial stress of the restoring element (32) is adjustable for the control piston (31).

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