Bohrkopf

Abstract

Drill head for drilling boreholes in soil comprising a drill head housing, a drill bit (8) arranged at its lower end and a connection area arranged at its upper end for connection to a drill string, wherein the connection area has an inlet opening (1) for pressurized flushing fluid and the drill bit (8) has at least one outlet opening (4, 5) for pressurized flushing fluid, and a percussion piston (6) is arranged in the drill head housing, which can be accelerated against the drill bit (8) and lifted back from it in alternating hydraulic switching states from opposite directions with pressure generated by flushing fluid in opposing percussion piston chambers (19, 20), wherein a valve arrangement (12, 18) is provided in the drill head housing with which the alternating hydraulic switching states can be generated, characterized in that the valve arrangement (12, 18) has at least two valve actuators (12,18) and each valve actuator (12, 18) is displaceable relative to another along an axis and each valve actuator (12, 18) can be reversed between two axial positions by axial pressure with flushing fluid and the walls of the valve actuators (12, 18) are each penetrated by valve control channels (34, 35, 36, 37, 38, 39) that can be pressurized with flushing fluid, wherein at least three different radial opposite positions of valve control channels (34, 35, 36, 37, 38, 39) can be generated by axial reversal of the valve actuators (12, 18) and a specific hydraulic switching state can be generated with each opposite position.

Description

[0001] The invention relates to a drill head for drilling boreholes in soil, comprising a drill head housing, a drill bit arranged at its lower end, and a connection area arranged at its upper end for connection to a drill string, wherein the connection area has an inlet opening for pressurized flushing fluid and the drill bit has at least one outlet opening for pressurized flushing fluid, and a percussion piston is arranged in the drill head housing, which, in alternating hydraulic switching states, can be accelerated against the drill bit from opposite directions with flushing fluid in opposing percussion piston chambers and can be lifted off again, wherein a valve arrangement is provided in the drill housing with which the alternating hydraulic switching states can be generated.

[0002] A pressurized flushing fluid is understood to be a liquid, e.g., water with flushing additives, which has been filtered and preferably recirculated, or clear water, that has a pressure sufficient to force it out of the drill bit under the influence of the drilling pressure for flushing purposes, and furthermore, that the pressure is high enough to initiate the movement of the impact piston. The absolute pressure head is not relevant to the invention; however, the typical required operating pressure at the tool is in the range of 50 to 100 bar. The flushing fluid can be pressurized by a pump unit, particularly one operated above ground. Preferably, an operating pressure is selected that is higher than the hydrostatic pressure present at the end of the drill bit.

[0003] Drill heads of this type are typically supplied with drilling fluid via a drill string to which the drill head can be attached. The drill string serves as the conduit for the drilling fluid and simultaneously drives the drill head by rotation. The drilling fluid enters the drill head through the aforementioned inlet opening at the upper connection point and exits at the drill bit at the lower end of the drill head, typically controlled by the valve assembly. The purpose of this fluid is usually to flush the borehole or to generate jets of fluid that can themselves have a material-removing effect or at least assist in the removal of the drill cuttings loosened by the drill head.

[0004] In the already known designs of such drill heads with impact pistons, the hydraulic energy generated by the flushing fluid is made usable by the valve arrangement in the drill head insofar as the flushing fluid and the hydraulic pressure exerted by it can accelerate the impact piston in the drill head onto the drill bit and lift it off again, for which purpose alternating hydraulic switching states are generated by the valve arrangement, which cause the acceleration onto the drill bit and the lifting off the drill bit.

[0005] The design can be such that, with a constant flushing pressure, the valve arrangement automatically switches between hydraulic switching states, repeatedly accelerating the impact piston onto the drill bit and then lifting it again. Accordingly, valve arrangements in drill heads known in the prior art typically have exactly two interchangeable hydraulic switching states, with which precisely this acceleration and lifting action can be generated.

[0006] Especially when drilling in hard rock, a hammering drilling method can be implemented, in which the energy is introduced into the rock by impact and not just rotation through impulse transfer between the drill bit and the rock, in order to effect a corresponding removal of material.

[0007] The inherent problem here is that the flushing fluid is incompressible, meaning there is no damping when switching between different operating states. This results in high pressure peaks due to the imposition of a change in volume flow on the incompressible and inert flushing fluid, which can even lead to the destruction of the drill head. Switching between different operating states refers to the controlled change of the valve assembly from one operating state to another.

[0008] DE 35 12 734 C1 discloses a striking device in which a reduced degree of stress is achieved in the impact-loaded elements. According to DE 35 12 734 C1, this can be accomplished, for example, by moving two pipes with openings forwards or backwards by means of compressed air, depending on the position of the openings. This also allows a striking element to be moved forwards or backwards, and the forward movement of the striking element can then deliver a blow against a housing.

[0009] It is therefore an object of the invention to convert the hydraulic energy of the flushing fluid into a percussive movement while reducing the resulting pressure peaks.

[0010] This problem is solved according to one aspect of the invention in that the valve arrangement has at least two valve actuators and each valve actuator is displaceable relative to another along an axis common to all valve actuators, particularly preferably on an axis common to all valve actuators, and each valve actuator can be reversed between two axial positions by axial, in particular axial end-face, pressure application with flushing fluid, and the wall of each valve actuator is penetrated, preferably in at least a radial direction, by valve control channels that can be pressurized with flushing fluid, wherein at least three, preferably four different radial opposite positions of valve control channels can be generated by axial reversal of the valve actuators, and a specific, in particular a different, hydraulic switching state can be generated with each opposite position.

[0011] The axial, and in particular end-face, pressure application to a respective valve actuator can be achieved by having an axial, and in particular end-face, surface of each valve actuator form a valve piston surface on which the pressure of the flushing fluid acts. The valve actuators thus move back and forth between at least two opposing valve piston chambers. Preferably, the direction of movement of the valve actuators is in the axial direction of the drill head, i.e., also coincides with the drilling direction. The aforementioned radial direction is a direction perpendicular to the drilling direction, or the longitudinal direction of the drill head.

[0012] The invention, like the prior art, can provide that the valve arrangement is designed to automatically switch between the different possible switching states when hydraulic pressure is applied, which is generated or at least transmitted by the flushing fluid, so that these different switching states can be generated successively and repeatedly.

[0013] The invention preferably provides for switching the switching states depending on the movement of the piston, in particular depending on the axial positions of the piston assumed during the movement. For this purpose, the piston, especially with its radially outer surface, can open and close control channels that pressurize and depressurize the valve piston chambers of the valve actuators. Such control channels can be located in the cylindrical surface surrounding the piston and can be pressurized with, or be pressurized with, flushing fluid.

[0014] In contrast to the prior art, such an arrangement does not merely generate two hydraulic states, but at least three, preferably exactly four, and possibly more than four switching states.

[0015] In addition to a typical switching state that generates a force acting on the impact piston in the direction of the drill bit, and in addition to a typical switching state that causes the impact piston to lift off the drill bit after an impact, at least one further switching state can be generated, in particular one that does not cause an abrupt switch between the force or pressure that causes the lifting and the force or pressure that causes the acceleration onto the drill bit. Preferably, one of the at least three, preferably four, hydraulic switching states is provided to achieve a damped movement of the impact piston between the two aforementioned states, at least temporarily.In such a damped movement, the absolute magnitude of the volume flow change imposed on the rinsing fluid by the switching state change should preferably be limited.

[0016] The invention preferably provides this by ensuring that the impact piston chamber, with which the impact piston can be accelerated towards the drill bit when pressurized, can not only be pressure-relieved to the environment of the drill head in one switching state and pressurized with the maximum available flushing pressure in a further switching stage, but that in a further switching state a pressure level can be applied to this impact piston chamber which is lower than the maximum flushing pressure, in particular at least 30% lower.

[0017] By using at least two valve actuators, each movable between two axial positions within the drill head, it is possible to achieve a total of four different possible positions of the valve arrangement with exactly two valve actuators. Each position can, for example, generate a hydraulic switching state. Optionally, it may also be possible to generate a state in one position that is identical to a switching state in another position, or a state in which no change to the system occurs—that is, a state that corresponds to a specific position but does not produce any hydraulically changing effect.

[0018] Thus, when using two valve actuators in the valve arrangement, a maximum of four, but also possibly fewer, switching states can be achieved, and when using more than two valve actuators, generally N valve actuators, a maximum of 2^N different switching states can be achieved. According to the invention, it can therefore be provided to include at least one, and optionally more than one, switching state in order to reverse the force acting on the drill bit, with the effect of at least one switching state that dampens the impact piston movement.

[0019] According to the invention, the valve actuators are displaceable at least along an axis common to all valve actuators, which can mean that the valve actuators are all displaced in parallel, although the individual axis for each valve actuator may differ. Particularly preferably, the valve actuators are arranged such that they are all displaceable on a common axis, i.e., the displacement axis is the same for each valve actuator.

[0020] The invention provides that in the valve arrangement, at least two, and in particular exactly two, valve actuators slide along one another in contact and are arranged side by side or, more preferably, nested within one another. In a particularly preferred nested arrangement, the valve arrangement can have at least one outer and at least one inner valve actuator, wherein the valve actuators are arranged coaxially within one another. Here, the displacement then takes place on a common central axis.

[0021] Particularly preferably, each of the valve actuators in such an arrangement is designed as a hollow cylinder and has the aforementioned valve control channels within its respective cylinder wall. The coaxially nested design of the valve actuators is particularly advantageous here, since this allows the valve actuators to form mutual guides and prevents any tilting moments from occurring when axial actuating forces are exerted by the flushing fluid, preferably acting on the axial end faces of the respective valve actuators.To generate actuating and / or holding forces, different valve piston surfaces can be formed on the axially opposite sides of the valve actuators, wherein one of the valve piston surfaces serves to exert a force to adjust the valve actuator in its position and another serves to exert only a, in particular lesser, force by means of which the achieved actuating position is maintained, e.g. after a switch-off of the actuating force.

[0022] Furthermore, the still preferred hollow cylindrical design of the respective valve actuators, and especially of the innermost valve actuator, allows for the arrangement of components of the drill head or the valve assembly participating in the control system inside the innermost valve actuator, for example, one or more channels for guiding flushing fluid. This also makes it possible to guide the flushing fluid not only radially to the outside of the valve assembly, but also from within.

[0023] The invention can also provide for the impact piston to be designed as a hollow sleeve, in particular a hollow cylindrical sleeve or at least a partially hollow cylindrical sleeve. This allows for the internal guidance of components, such as channels carrying flushing fluid. Furthermore, the upper and lower impact piston chambers arranged around the impact piston can be annular. The impact piston can slide back and forth or up and down on a guide centrally located within the chamber, and this guide can also contain channels for flushing fluid, in particular channels that carry the flushing fluid to the drill bit for discharge.

[0024] In a preferred embodiment of the drill head, the invention may provide that the drill head housing has a pressure peak compensation device by means of which pressure peaks caused by changes in volume flow in the supplied flushing fluid can at least be reduced, in particular depending on changes in switching state.

[0025] According to one possible embodiment, the drill head can comprise at least two housing elements arranged one behind the other in the flow direction and detachably connected to each other. A downstream element comprises the drill bit and the impact piston, while an upstream element houses the pressure peak compensation device. The flushing fluid is preferably transferred through the upper housing element, which follows first in the flow direction, into the lower housing element, which follows next. This has the advantage that the pressure peak compensation device can be designed in various ways, and one of several possible pressure peak compensation devices can be selectively connected to a further housing element containing the drill bit. Likewise, a given pressure peak compensation device can be operated in this way with various types of drill bits.

[0026] In one embodiment, the invention may provide that the pressure peak compensation device comprises a displacement chamber in which a compressible gas bubble surrounded by the purge fluid is arranged.

[0027] Such a gas bubble can, for example, be formed by a volume of gas enclosed by a flexible membrane. In a possible and preferred embodiment, the membrane of the gas bubble can be pressurized on the inside by the gas and on the outside by the purge fluid located in the displacement chamber. For example, the gas bubble can be arranged centrally within the displacement chamber. Such a displacement chamber only needs to be in fluid communication with the inlet opening for the purge fluid, preferably permanently, i.e., in every possible switching state of the valve arrangement. If a pressure spike occurs during a change of switching state, this can lead to compression of the gas bubble and thus be dissipated. With progressive compression, kinetic energy of the piston is stored in the gas bubble, and the piston slows down, i.e., its movement is dampened.

[0028] Preferably, the valve arrangement is further controlled such that, during the subsequent expansion of the gas bubble, the flushing fluid displaced by the gas bubble can flow into the upper piston chamber, which serves to accelerate the piston towards the drill bit. In this way, energy stored from the pressure peak can be directly recovered.

[0029] In another embodiment, the pressure peak compensation device may comprise a nozzle arrangement with at least one nozzle, preferably more than two nozzles connected in series, through which the inlet opening for flushing fluid is connected to an outlet channel, through which flushing fluid is permanently directed into the external environment of the drill head, particularly wherein the outlet channel is arranged on the drill bit, and especially preferably wherein this outlet channel on the drill bit is an outlet channel with the smaller cross-section of two outlet channels. Although this nozzle arrangement reduces the maximum achievable pressure level due to the permanent connection to the environment of the drill head, this connection ensures that any pressure peak that occurs is reduced.While this design reduces the overall energy efficiency of the drilling device, it is easy to implement and requires little maintenance, especially since this design has no moving parts.

[0030] Both design options thus achieve a situation where the switch between the lifting movement and an acceleration of the impact piston towards the drill bit is not abrupt, but rather a damped movement in which the impact piston is braked, passes through a dead point of movement and is then accelerated again towards the drill bit.

[0031] This helps to avoid pressure peaks and thus to increase the overall service life of a drill bit according to the invention.

[0032] In particular, the pressure peak compensation device now makes it possible to implement damped reversing movements with four switching states, in which not all hydraulic energy is directed to the impact piston.

[0033] During these reversal movements, either the gas bubble or the nozzles of the pressure peak compensation device are located parallel to the pressure supply, enabling pressure reduction and providing a permanently continuous path for the hydraulic fluid.

[0034] The 4 states are: 1. Reverse the piston upwards just before and after impact (both valve actuators are preferably in the lower actuating position) 2. Raise the piston (inner valve actuator is preferably at the top, outer valve actuator preferably at the bottom) 3. Slow down and reverse the piston movement (both valve actuators are preferably at the top) 4. Accelerate the piston downwards (outer valve actuator is preferably at the top, inner valve actuator is preferably at the bottom)

[0035] This circuit sequence prevents the full pressure supply from the flushing fluid being applied to the impact piston, which moves against the flushing fluid. The relative position of the valves to each other is preferably used to open outlet channels for this process on the drill head. In the axial direction of movement around the impact piston, the invention provides, in a manner known per se, an upper and a lower impact piston chamber, wherein the upper impact piston chamber is, for example, formed directly adjacent to the upper axial end face, e.g., the annular end face of the impact piston, and wherein the lower piston chamber is, for example, formed as an annular chamber laterally around the piston in order to utilize the lower axial end face for impulse transmission. However, a fundamentally different mechanical design of the lower or upper impact piston chamber is also possible using the invention.The only essential point here is that the pressure in the two piston chambers acts on piston surfaces whose normal vectors are opposite.

[0036] Different pressure levels must be switched within the respective piston chambers by means of the valve arrangement. For example, a high pressure level in the upper piston chamber is used to accelerate it towards the drill bit, while simultaneously the lower piston chamber is switched to a low pressure level. The pressure difference between the piston chambers then causes the downward movement of the piston towards the drill bit, preferably while simultaneously displacing drilling fluid from the lower piston chamber, preferably towards the surrounding environment. The lower pressure level is thus preferably generated by switching the lower piston chamber to the external environment of the drill head.

[0037] During the lifting movement of the piston, the pressure levels are reversed, and the flushing fluid, which is switched from the upper piston chamber to a lower pressure level, is then preferably moved towards the external environment.

[0038] The aforementioned high and low pressure levels differ in their effective absolute pressure magnitude in that the high pressure level is higher than the low pressure level, and conversely, the low pressure level is lower than the high pressure level. The exact absolute values ​​are not crucial for the invention's effect. There can also be several low and high pressure levels. What is essential is that a pressure difference exists between a high and a low pressure level, generating a sufficiently large force to move the piston.

[0039] In a further preferred embodiment, the invention may provide that the drill bit has a first and a second outlet channel through which drilling fluid can be drained from the drill head to the external environment, for example towards the bottom of the borehole, wherein the first outlet channel has a larger cross-section than the second outlet channel and the upper, and in particular also the lower, impact piston chamber can be selectively hydraulically switched to the first or to the second outlet channel via the valve arrangement to generate a low pressure level in the respective impact piston chamber when this impact piston chamber is switched to the first, in particular larger, outlet channel and to generate a high pressure level when the impact piston chamber is switched to the second outlet channel.Since pressure reduction to the environment also occurs in the case of the piston chamber being connected to the second, especially smaller in cross-section, outlet channel, the high pressure level thus generated is also lower than the maximum possible pressure level if the flushing fluid is not discharged to the outside through any channel or, in one version of the pressure peak compensation, is permanently discharged through the nozzles.

[0040] According to the invention, essentially at least three pressure levels are provided which can be selectively switched to at least the upper, and optionally also the lower, piston chamber of the piston, namely 1) Low pressure level when the rinsing fluid is routed to the environment via the outlet channel with a larger cross-section 2) High pressure level when the rinsing fluid is routed to the environment via the outlet channel with a smaller cross-section, 3) Maximum possible pressure level when the rinsing fluid is not or only connected to the environment via the nozzles of the pressure peak compensation device.

[0041] The same applies to the valve piston chambers of the valve actuators. In particular, when a respective piston chamber (of a percussion piston or valve actuator) is connected to the large-cross-section outlet channel, not only is the pressure level low, but flushing fluid can be displaced to the surroundings and out of the piston chamber. The two outlet channels mentioned, which are preferably arranged in the drill bit, are further preferably connected to channels that lead through the inner hollow area of ​​the sleeve-shaped percussion piston and / or the sleeve-shaped hollow valve actuators.

[0042] Accordingly, depending on whether the flushing fluid is directed to the outlet channel with the larger or smaller cross-section, a greater or lesser pressure drop is generated. The pressure difference between the two possible pressure drops generates the driving force acting on the impact piston. Depending on the direction of action between the upper and lower impact piston chambers, this force either accelerates the impact piston towards the drill bit or lifts it away from the drill bit. The valve actuators can be moved in the same way.

[0043] The invention may provide that in the simultaneous upper positions of the valve actuators, in particular the exactly two valve actuators, and in the simultaneous lower positions of the valve actuators, in particular the exactly two valve actuators, the inlet opening of the rinsing fluid is hydraulically connected at least to the second outlet channel.

[0044] However, the valve arrangement can still generate 4 switching states, e.g. one that does not cause a reversal of direction or acceleration at the piston, but by which a valve actuator is switched.

[0045] In a further embodiment, the invention may provide that the volume of a gas bubble, which may be intended for pressure peak compensation, is compensated against depth-dependent compression / expansion by controlled release of fluid from the gas bubble or addition of fluid to the gas bubble.

[0046] This design offers the possibility to compensate for the gas volume within the gas bubble against external pressure influences resulting from different depths of the drill head at which it is located during a drilling process.

[0047] For example, the pressure increase with increasing depth causes the volume of the gas bubble to be reduced by the hydrostatic pressure at depth, so that the damping of the piston movement is also changed depending on the depth, unless the gas bubble is compensated against this influence according to the invention.

[0048] For example, the drill head housing or an overlying section of the drill string may be provided with a gas reservoir from which gas can be introduced into the gas bubble as the drill bit deepens. Thus, if the volume is compressed with increasing depth due to the hydrostatic pressure, the volume can be increased again by introducing gas into the gas bubble. In particular, the invention may provide that the gas pressure remains constant despite increasing depth.

[0049] In a further embodiment of this invention, a liquid bladder is arranged within the gas bladder, from which liquid can be drained as the drill bit's depth increases. In particular, the draining can occur towards the vicinity of the drill head. The liquid in the liquid bladder is incompressible, so its volume does not change with increasing pressure as the drilling depth increases, while the volume of the gas bladder decreases. By draining liquid from the liquid bladder, its volume decreases, and thus the total volume available for the gas within the gas bladder increases, thereby also allowing for influencing the damping properties of the gas bladder. In particular, it can also be provided that the volume of the gas bladder is increased with increasing depth.

[0050] It may also be provided that the aforementioned fluid bladder can be switched on, at least temporarily, to a channel carrying flushing fluid for filling with flushing fluid.

[0051] The invention is explained in more detail below with reference to the figures.

[0052] Each of the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13, Fig. 14 to Fig. Figure 15 shows the same embodiment of the invention and the valve arrangement used therein in different movement positions of the piston and different switching stages.

[0053] The drill head shown in all figures comprises a valve arrangement with two valve actuators 12 and 18, which are hollow cylindrical and arranged coaxially inside each other, so that the inner cylindrical surface of the valve actuator 12 slides on the outer surface of the valve actuator 18.

[0054] Fig. Figure 1 shows the drill head according to the invention shortly after the impact of the impact piston 6 on the drill bit 8. The outer valve actuator 12 and the inner valve actuator 18 are in the lower position. The first switching state according to the invention has been reached.

[0055] Due to the relative positions of the valve actuators 12 and 18, the pressure distribution inlet 37 is connected via the connection 39 inside the valve actuator 18 to the liquid nozzles 4 on the drill bit 8 via the channel 3. These nozzles 4 form one of two outlet channels, namely the one with the smaller cross-section.

[0056] The lower end position of the outer valve actuator 12 connects the pressure supply through the inlet opening 1 via the channel 9 to the lower piston chamber 20 via the pressure distribution groove 37.

[0057] The upper piston chamber 19 is connected via channel 2, through the relief distribution groove 38 of the outer valve actuator 12, and via channel 10 to the large outlet opening 5 on the drill bit 8. This large outlet opening is the opening to the outer environment of the outlet channel, which has a larger cross-section.

[0058] Thus, the pressure in the lower piston chamber 20 is higher than in the upper piston chamber 19, causing the piston 6 to move upwards. The outer valve actuator 12 is held in the down position by the auxiliary holding channel 32, which is connected to the lower piston chamber via channel 9. The higher pressure is lower than the maximum possible pressure in the overall system.

[0059] The piston, through its upward movement, will open a connection between channel 11 and the lower piston chamber 20, which in Fig. Figure 2 shows that channel 11 is connected to the lower valve piston chamber 24 of the inner valve actuator 18, which is now pressurized. The upper valve piston chamber 26 of the inner valve actuator 18 is connected via channel 63 to the upper impact piston chamber 19 of the impact piston 6, where a lower pressure prevails. This results in an upward movement of the inner valve actuator 18. The outer valve actuator 12 cannot be carried upwards by friction or similar means, since the upper valve piston chamber of the outer valve actuator 12 is only connected to channel 14, which is closed by the impact piston 6 in this state.

[0060] Fig. Figure 3 shows the end of the upward movement of the inner valve actuator 18. The second switching state has now been reached.

[0061] The connection between the pressure distribution inlet 37 and the liquid nozzles 4 via channel 3 is now closed. The full supply pressure, i.e., the maximum possible pressure, is now directed to the lower impact piston chamber 20 to lift the impact piston with greater force. The upper relief passage 34 in the inner valve actuator 18 is now connected to the large outlet opening 5 on the drill bit 8 via channel 10 by reaching its upper end position.

[0062] As the piston continues to move upwards, as in Fig. As shown in Figure 4, the channel 13 to the lower piston chamber 20 is opened, so that the lower valve piston chamber 25 of the outer valve actuator 12 is under the same pressure as the lower piston chamber 20. Through the connection to the large outlet opening 5 of the upper valve piston chamber 23 of the outer valve actuator 12, the outer valve actuator can now be moved upwards, as shown in Figure 4. Fig. 5 shown.

[0063] The effective annular areas on the outer valve actuator 12, on which the auxiliary holding channels 32 and 33 act, are smaller than the end faces of the valve actuator 12, which is why the valve actuator can be moved upwards against the holding force applied by auxiliary holding channel 32.

[0064] The upward movement of the outer valve actuator 18 moves the relief distribution groove 38 and the pressure distribution groove 37. This switches the lower piston chamber 20 to the large outlet opening 5 on the drill bit 8 and the pressure supply via the inlet opening 1 to the upper piston chamber 19. As a result, channel 13 becomes depressurized during the movement, so the force for moving the valve is absent.

[0065] A connection from the upper piston chamber 19 via the auxiliary holding channel 33 to another annular surface on the outer valve actuator 18 now takes over the drive of the outer valve actuator as soon as the upper piston chamber is under pressure in order to continue the movement.

[0066] The transition of switching during the upward movement is in Fig. Figure 6 illustrates that the flushing fluid, which continues to move in its original direction due to inertia caused by the piston movement, now moves against the pressures now acting upon it. To prevent a resulting pressure spike, the pressure distribution inlet 37 is reconnected to the fluid nozzles 4 via the nozzle switching connection 39 by the valve movement.

[0067] In Fig. 7 the outer valve actuator 12 is almost at the end of its movement, the pressure from the pressure supply is now counteracted by the flow from the upper piston chamber 19, this overpressure can now be reduced by the liquid nozzles 4.

[0068] The valve movement is continued at this moment by the auxiliary device with the auxiliary holding channel 33. Fig. 8 The outer valve actuator 12 has reached its end position; it is held in the upper position by the auxiliary holding channel 33, which is pressurized via the connection from channel 2 to inlet opening 1 through the pressure distribution groove 37. The third switching state is thus reached.

[0069] Due to the higher pressure in the upper piston chamber 19 than in the lower piston chamber 20, but not the maximum possible pressure, the piston 6 is now decelerated in a controlled manner until it reaches top dead center as described in Fig. 9 shown, achieved.

[0070] To reduce pressure surges, the invention provides the previously described pressure peak compensation device according to the first or second embodiment. This is shown in the following figures.

[0071] The impact piston 6 is now accelerated downwards towards the drill bit 8 by the applied pressure; this is in Fig. 10 shown.

[0072] During the downward movement of the piston 6 according to Fig. In step 11, channel 63 is opened, which is connected to the upper valve piston chamber 26 of the inner valve actuator 18 and establishes a connection to the upper impact piston chamber 19. Since the lower valve piston chamber 24 of the inner valve actuator 18 is connected to the lower impact piston chamber 20, which has a lower pressure, the inner valve actuator 18 is now moved downwards.

[0073] In Fig. 12. The inner valve actuator 18 has now reached its lower end position, thereby interrupting the connection to the liquid nozzles 4 via the nozzle switching connection 39. The fourth switching state has been reached.

[0074] The full maximum pressure is now available to accelerate the impact piston 6 further towards the drill bit 8. In its final position, the lower relief passage 35 connects the lower valve piston chamber 25 of the outer valve actuator 12 to the large outlet opening to the environment.

[0075] Shortly before the impact piston 6 strikes the drill bit 8, the impact piston opens the channel 14, which connects the upper valve piston chamber 23 of the outer valve actuator 12 with the pressure in the upper impact piston chamber 19. This is in Fig. 13 shown.

[0076] The valve is currently held in the upper position by the auxiliary holding channel 33. However, since the effective areas of the upper and lower valve piston chambers are larger, the outer valve actuator 12 is now moved downwards. This again switches the pressure and relief sides to the upper and lower piston chambers. During the downward movement, the pressure in the upper piston chamber 19 drops due to the switching process and builds up in the lower piston chamber 20, so that the upper auxiliary holding channel 32 continues the movement and subsequently holds the valve in the lower position.

[0077] In Fig. Figure 14 also illustrates an unfavorable braking movement of the impact piston by the hydraulics, which must be kept as short as possible in order to utilize as much of the kinetic energy as possible for the impact. Here again, a hydraulic pressure surge is avoided by directing the pressure supply to the fluid nozzles 4 in the drill bit via the nozzle switching connection 39. After the impact, the impact piston is retracted as in Fig. As described in section 1, the process is lifted, and the process begins again.

[0078] The figures illustrate that each of the possible switching stages, generated by the different axial positions of the two valve actuators, is achieved by opening or closing control channels during the movement of the piston. This results in the sequential pressurization of the upper and lower valve piston chambers of the inner and outer valve actuators, thus automatically switching the valve arrangement between its four switching states. The invention preferably provides that, at any given time, only one of the two valve actuators is moved by pressurizing the valve piston chambers, never both simultaneously.

[0079] In Fig. Figure 15 shows the deactivation of the impact device. If the drill bit is pulled out of the housing as shown, the impact piston can be moved further towards the drill bit, and the small outlet opening is connected to the nozzles 4, the large outlet opening 5, and the upper impact piston chamber 19 via channel 40. This generates a pressure level as shown in Fig. The position shown in step 1, used to lift the impact piston, is no longer possible. This state is particularly useful for flushing the borehole without using the hammer drill.

[0080] The Fig. Figure 16 shows a first possibility for achieving pressure peak compensation in the drill head according to the invention. Here it can be seen that the inlet opening 1 is permanently connected via the nozzle arrangement 64, with its four nozzles connected in series, to the nozzles 4 and thus to the outlet channel, which has a smaller cross-section, via the channel 65. Flushing fluid is thus permanently discharged to the environment in each switching stage, particularly by means of a high flow resistance, in order not to reduce the maximum possible pressure too much. This permanent connection allows pressure peaks to be reduced. Here it is shown that the nozzles 64 are integrated into the upper end of the drill head.

[0081] In contrast, it shows Fig. 17 Another embodiment of the pressure peak compensation device. Here, the drill head according to the invention is equipped with a two-element housing. The drill bit and the impact piston, as well as the valve arrangement, are integrated in the lower, downstream housing.

[0082] A gas bubble 17 is arranged in the upper, upstream housing element. This bubble is enclosed by a rubber diaphragm 60 and, in turn, by a grid 54. The gas bubble 17 is directly integrated into the connecting path through which purge fluid is guided from the inlet 41 of the upper element to the inlet 56 of the lower element. Thus, the gas bubble acts permanently and can absorb pressure peaks, as described above.

[0083] For depth compensation, a liquid bubble 55 is arranged inside the gas bubble, from which liquid is automatically drained when the pressure increases due to compression of the gas bubble at increasing depth.

[0084] Further details will be provided based on the Fig. 18 explains which is merely the upper element of the Fig. 17 shows.

[0085] The gas bubble 17, located in the lower part of the upstream upper housing element and separated from the purge fluid in the chamber by a rubber diaphragm 60, can be compressed by a compression volume when the pressure is increased. The gas bubble 17 can expand within the rubber diaphragm 60 up to the grid 54 and thus be pre-compressed to a gas pre-pressure, in particular one that is higher than the pressure of the purge fluid in the surrounding chamber 61.

[0086] Inside the gas bubble 17 is a liquid bubble 55. This liquid bubble comprises a rubber membrane that can be filled with a liquid.

[0087] The pressure peak compensation device in the upper element is equipped with a gas tank or gas reservoir 30 into which a high-pressure gas can be filled through a filling nozzle 53 before use. The pressure can be approximately 600 bar, for example, at great depths. The gas reservoir must be filled to such a pressure that even at great depths (where, advantageously, the temperature also increases and thus the pressure in the heated gas reservoir also increases) the gas pressure is higher, preferably significantly higher, than the ambient pressure.

[0088] The following explains the function that results from increasing ambient pressure at increasing depth.

[0089] It is a prerequisite that drill rods are repositioned, during which the working pressure in the entire drill head is briefly equal to the ambient pressure outside the drill head.

[0090] The minimum gas pressure regulating device 29 is connected to the environment via the channel 57 with the opening 52. The minimum gas pressure regulator comprises two pressure regulators 42 and 43, which reduce the high pressure at shallow depths to the actual minimum gas pressure regulator 44. The regulating elements include pistons that are connected on one side to the ambient pressure p0 via channel 57 and have a spring on the same side that also presses against this surface.

[0091] The other side of the piston is connected to the outlet of the regulating element. Such a pressure reducer reduces the pressure to a specific pressure above the ambient pressure p0. However, due to the plunger that lifts the valve above the piston, a control deviation remains, which can be kept negligibly small by using multiple pressure stages. For example, the first pressure regulator 42 would regulate the pressure to p0+250 bar, and the pressure regulator 43 would regulate the pressure to p0+10 bar.

[0092] If the ambient pressure p0 at depth rises above 250 bar due to hydrostatic pressure, the pressure regulator 42 will no longer close and will become inactive. This is the desired outcome. The pressure regulator 43 then continues to regulate to p0 + 10 bar. The minimum gas pressure regulator 44 is now connected to the gas bladder 17 via channel 58. The spring in the minimum gas pressure regulator 44 and the piston area allow for the adjustment of the pre-pressure of the gas cushion 17, which presses the gas cushion 17 against the grid 54.

[0093] As the ambient pressure decreases, the gas pre-charge pressure must be reduced. During operation, the gas cushion is compressed, which is why the operating pressure regularly exceeds the maximum gas pre-charge pressure. The maximum gas pre-charge pressure regulator 27 includes a pressure regulating valve 49, the rear of which is connected to the environment at p0 via channel 57. The maximum gas pre-charge pressure can be adjusted via the valve area and the spring constant.

[0094] If the gas pressure becomes too high, the gas can be released into the annular space outside the tool. The retaining piston 48 is connected to the tool's pressure supply via channel 62 on its upper side. The underside of the retaining piston is also connected to the environment via channel 57. During operation, when compression of the gas cushion also occurs and no maximum gas pressure control is desired, the retaining piston 48, due to the working pressure in the tool, additionally pushes the pressure regulating valve 49 downwards, thus keeping the regulating valve 49 closed. Maximum gas pressure control therefore only engages when the tool is not in operation.

[0095] If gas is supplied via the minimum gas pressure control device 29 to compensate for the increasing depth, the volume of the gas bubble 17 must still be increased to maintain the desired ratio of compression volume to pressure increase. If the volume of the gas bubble 17 is too small, the gas pressure increases by the same volume during compression. This results in larger measurable pressure peaks. When such excessively high pressure peaks occur, indicating an insufficient gas volume, the liquid in the liquid bubble 55 is released by the liquid maximum pressure regulator 51 via the channel 57 into the annular space through opening 52. This provides the gas bubble 17 with more volume. The missing gas pressure is automatically compensated for by the minimum gas pressure control device 29 after the next compression.The liquid maximum pressure regulator 51 is a pressure regulating valve whose opening pressure can be determined by spring constant and valve area.

[0096] A safety valve 50 is also provided, which is intended to limit the gas pressure in the gas bladder 17 to the ambient pressure p0. The liquid maximum pressure regulator 51 is set to a lower pressure, so that the liquid is forced out of the liquid bladder before the safety valve 50 opens.

[0097] Due to static friction or leaks, it can never be guaranteed that the exact correct amount of liquid has been drained, and as the ambient pressure p0 decreases, liquid must also be added to the liquid bladder 55 to reduce the gas volume again.

[0098] For this purpose, pump 28 pumps a volume of liquid from the working medium into the liquid bladder. The pump comprises two check valves 46 and 47 and a spring-returned pump piston 45. The top is connected to the pressure supply, the bottom to ambient pressure. When the tool is switched on, i.e., when the working pressure increases, the piston is pushed downwards and forces a volume of liquid at the lower end of the plunger through the check valve 46 into the liquid bladder. When the tool is switched off, the piston 45 is returned to its original position by a spring, and the valve 47 refills the volume below the plunger with liquid from the working medium. As the depth increases, this volume is released back into the environment through the liquid maximum pressure regulator 51.

Claims

[1] Drill head for drilling into soil comprising a drill head housing, a drill bit (8) arranged at its lower end and a connection area arranged at its upper end for connection to a drill string, wherein the connection area has an inlet opening (1) for pressurized flushing fluid and the drill bit (8) has at least one outlet opening (4, 5) for pressurized flushing fluid and a percussion piston (6) is arranged in the drill head housing, which can be accelerated against the drill bit (8) and lifted off again from it in alternating hydraulic switching states from opposite directions with pressure generated by flushing fluid in opposing percussion piston chambers (19, 20), wherein a valve arrangement (12, 18) is provided in the drill head housing with which the alternating hydraulic switching states can be generated, characterized by, that the valve arrangement (12, 18) has at least two valve actuators (12, 18) and each valve actuator (12, 18) is displaceable relative to another along an axis and each valve actuator (12, 18) can be reversed between two axial positions by axial pressure with flushing fluid and the walls of the valve actuators (12, 18) are each penetrated by valve control channels (34, 35, 36, 37, 38, 39) that can be pressurized with flushing fluid, wherein at least three different radial opposite positions of valve control channels (34, 35, 36, 37, 38, 39) can be generated by axial reversal of the valve actuators (12, 18) and a specific hydraulic switching state can be generated with each opposite position. [2] Drill head according to claim 1, characterized by, that the at least two valve actuators (12, 18) are designed to slide along each other in contact and are arranged side by side or inside each other, in particular in an interlocking arrangement formed by at least one outer (12) and at least one inner valve actuator (18). [3] Drill head according to any of the preceding claims, characterized by , that the drill head housing has a pressure peak compensation device (17 / 61, 64) by means of which pressure peaks caused by volume flow changes in the supplied flushing fluid can at least be reduced. [4] Drill head according to claim 3, characterized by , that it comprises at least two elements lying one behind the other in the direction of flow, which are detachably connected to each other, wherein a downstream element comprises the drill bit (8) and the impact piston (6) and the pressure peak compensation device (17 / 61, 64) is arranged in an upstream element. [5] Drill head according to claim 3 or 4, characterized by , that the pressure peak compensation device (17 / 61) comprises a displacement chamber (61) in which a compressible gas bubble (17) surrounded by the purge fluid is arranged. [6] Drill head according to claim 3 or 4, characterized by , that the pressure peak compensation device (64) comprises a nozzle arrangement with at least one nozzle (64) via which the inlet opening (1) for flushing fluid is connected to an outlet channel (4) via which flushing fluid is permanently directed into the external environment of the drill head. [7] Drill head according to one of the preceding claims, characterized by, that the drill bit (8) has a first and a second outlet channel (4, 5) through which flushing fluid can be discharged from the drill head to the external environment, wherein the first outlet channel (5) has a larger cross-section than the second outlet channel (4) and the upper and lower piston chambers (19, 20) can be selectively hydraulically switched to the first or second outlet channel (4, 5) via the valve arrangement (12, 18) to generate a low pressure level in the respective piston chamber (19, 20) when the piston chamber (19, 20) is switched to the first outlet channel (5) and to generate a high pressure level when the piston chamber (19, 20) is switched to the second outlet channel (4). [8] Drill head according to claim 7, characterized by, that in the simultaneous upper position of both valve actuators (12, 18) and in the simultaneous lower position of both valve actuators (12, 18) the inlet opening (1) of the flushing fluid is hydraulically connected at least to the second outlet channel (4) and / or in the upper position of the inner valve actuator (18) and lower position of the outer valve actuator (12) the flushing fluid is switched to the lower piston chamber (20) and / or in the lower position of the inner valve actuator (18) and upper position of the outer valve actuator (12) the flushing fluid is switched to the upper piston chamber (19). [9] Drill head according to claim 5, characterized by , that the volume of the gas bubble (17) is compensated against depth-dependent compression / expansion by controlled release of fluid or controlled addition of fluid. [10] Drill head according to claim 9, characterized by, that the drill head housing has a gas reservoir (30) from which gas can be introduced into the gas bubble (17) as the depth of the drill bit increases. [11] Drill head according to one of the preceding claims 9 or 10, characterized by , that a liquid bubble (55) is arranged in the gas bubble (17), from which liquid can be drained as the depth of the drill bit increases. [12] Drill head according to claim 11, characterized by , that the fluid bladder (55) can be connected to a channel carrying flushing fluid for filling with flushing fluid.

Images