Hydraulic switch and drill hammer

Abstract

The invention relates to a hydraulic switch (1) comprising a separation chamber (2) which has an inlet opening, a first outlet opening (21) and a second outlet opening (22), wherein the inlet opening is connected to an inlet channel (4) and the first and the second outlet opening (21, 22) are each connected to an outlet channel (51, 52) each of which has a first longitudinal portion (521, 511) and a second longitudinal portion (522, 512), wherein the first longitudinal portion (511, 521) has, proceeding from the outlet opening (21, 22), a cross-sectional area that increases as the length increases, wherein the hydraulic switch (1) furthermore contains a first and a second feedback channel (31, 32), the inputs (311, 321) of which are located in the respective second longitudinal portion (512, 522) of one of the outlet channels (51, 52) and the outputs (312, 322) of which open out at opposite sides of the inlet channel (4). The invention also relates to a drill hammer having such a hydraulic switch.

Description

[0001] Hydraulic switch and hammer drill

[0002] The invention relates to a hydraulic switch with a separating chamber having an inlet opening, a first outlet opening, and a second outlet opening. The inlet opening is connected to an inlet channel, and the first and second outlet openings are each connected to an outlet channel. Hydraulic switches of this type can be used for a fluid drive of an oscillating consumer, which can be, for example, a piston.

[0003] A hydraulic switch of this type is known from US 3,016,066. This known hydraulic switch has a separating chamber with an inlet opening. When the hydraulic switch is in operation, a pressurized drive fluid is supplied to the inlet opening. The drive fluid leaves the separating chamber through one of the two opposite outlet openings. This utilizes the Coanda effect, which causes the drive fluid to adhere to one wall of the separating chamber. A pulse applied via a feedback channel can direct the drive fluid to the opposite boundary wall of the separating chamber, causing it to exit through the opposite second outlet opening. This switching process can be repeated cyclically. The known hydraulic switch thus operates as an oscillator without requiring mechanical switching elements subject to wear.Oscillating fluid machines can be operated using the fluid alternately exiting the openings. However, this known hydraulic switch has various shortcomings. For example, the oscillation starts only unreliably after a standstill or when the volume flow supplied via the inlet opening starts up. In some cases, it has been found that the oscillator only runs unstably, i.e., the oscillation stops after a certain period of operation, so that the drive fluid continuously exits from a single outlet opening. Finally, the known hydraulic switch has a high pressure drop, which limits its possible applications. Based on the prior art, the object of the invention is therefore to provide a hydraulic switch that starts reliably after a standstill, runs stably, maximizes frequency, and minimizes pressure drop.The object is achieved according to the invention by a hydraulic switch according to claim 1 and a hammer drill according to claim 12. Advantageous developments of the invention can be found in the subclaims. According to the invention, a hydraulic switch is proposed which has a separation chamber. The separation chamber has an inlet opening on one side. At the inlet opening on the opposite side of the separation chamber there are at least one first outlet opening and at least one second outlet opening. The separation chamber can have a substantially triangular base area so that the cross-section increases from the inlet opening to the outlet openings. The separation chamber can have a prism-shaped basic shape so that the boundary surfaces are flat. In other embodiments of the invention, the separation chamber can have a conical or tapered cross-section, i.e. the boundary walls are curved.When the hydraulic switch is operating, any fluid, such as water, alcohol, glycol, or oil, is supplied to the separating chamber via the inlet opening. The drive fluid can be supplied to the separating chamber at any flow rate and slightly increased pressure to generate a sufficiently fast fluid jet at the inlet. Due to the Coanda effect, the drive fluid supplied through the inlet opening adheres to a wall of the separating chamber and exits the separating chamber through the first or second outlet opening.

[0004] Each outlet opening is followed by an outlet channel whose cross-section or cross-sectional area increases with the length from the outlet opening. The increase in cross-sectional area can, for example, be linear or quadratic with the length of the first longitudinal section. The outlet channels can also have a polygonal or round cross-section, since the Coandæ effect does not apply here and therefore no longer requires straight surfaces. The diffusely shaped outlet channel serves to convert the previously kinetically converted energy of the incoming jet back into potential energy and slow it down. This increases the pressure again and can thus be used to operate the consumer.

[0005] When the hydraulic switch is operated, the fluid column of the drive fluid directed into an outlet opening is subjected to a switching pulse. This causes the jet of the inlet fluid to contact the opposite wall of the separating chamber and thus be directed into the opposite outlet opening and the outlet channel associated with this outlet opening. As soon as the operated consumer reaches its end position, the water column is subjected to another switching pulse, so that it is directed back over the opposite wall of the separating chamber into the original outlet opening. This switching process occurs cyclically and, depending on the selected parameters, can generate any adjustable frequency.

[0006] To generate the switching pulse, the invention provides a first and second feedback channel, the inputs of which are each located in the lower longitudinal section of one of the exhaust channels and the outputs of which open out on opposite sides of the intake channel. Compared to known switches whose feedback channels begin further upstream in the exhaust channels, it has been shown that the deeper positioning in the lower longitudinal section of the exhaust channels results in the switching pulse being stronger and being able to be transmitted with less loss, despite the greater length of the feedback channels. In this way, the switching operations of the hydraulic switch are more reliable, so that the operation of the switch is more stable and switching changes occur less frequently. Comparative tests have shown that the lengthening of the feedback channels and their deeper insertion in the second longitudinal section of the exhaust channels can amplify the switching pulses by up to 30%.

[0007] One possible application for the described hydraulic switch could be, for example, a conventional surface or underground hammer drill, which can be used, for example, underground for hard rock drilling in mining, geothermal energy, or oil and gas exploration. Such a hammer drill can have a piston / cylinder pairing in which a piston oscillating freely in the cylinder generates impact energy, which is transferred to a drilling tool and used to break up the rock. For this purpose, the piston is alternately pressurized with a drive fluid from its underside and its top side, so that the piston is cyclically raised from a lower end position and then accelerated downwards from the upper end position.If an upper and a lower connection of the cylinder are each connected to one of the outlet channels of the hydraulic switch, the latter ensures that the piston is cyclically pressurized with the drive fluid from above and below, thereby causing it to oscillate. Compared to known hydraulic switches, the hydraulic switch according to the invention has the advantage of stable and reliable operation and reliable starting of the piston or the connected consumer. Compared to known mechanical switching elements, the hydraulic switch according to the invention has the advantage of low-wear operation without moving parts. This also allows the use of drive fluids that have an abrasive effect due to dispersed particles, such as dirty water or rinsing fluids.

[0008] In some embodiments of the invention, at least one separation edge can be arranged in the wall of the separation chamber, the distance of which from the inlet opening influences the mode of action of the Coandæ effect. In the hydraulic switch according to the invention, this lies between approximately 40% and approximately 60% of the length of the separation chamber. In this way, the separation edge is arranged further upstream than in known hydraulic switching elements. This feature has the effect of stabilizing the Coandæ effect of the incoming jet, so that it is drawn more strongly to the inner wall of the separation chamber. This stabilizes the flow so that the hydraulic switch can be operated more reliably and the oscillation does not suddenly break off. The height of the separation edge above the wall of the separation chamber determines the resulting negative pressure.

[0009] In some embodiments of the invention, the hydraulic switch can further comprise at least a first discharge channel and a second discharge channel, wherein the first discharge channel is located in the upper longitudinal section and above the feedback channel of the first outlet channel, and the second discharge channel is located in the upper longitudinal section and above the feedback channel of the second outlet channel. According to the invention, in this case, the discharge channel and the outlet channel enclose an angle that is as sharp as possible. This angle can be between approximately 25° and approximately 50°. The discharge channels are designed to carry away the drive fluid ejected during the counter-movement of the consumer without influencing the flow exiting the separating chamber.The steeper arrangement of the outlet channels compared to known hydraulic switches provides the advantage that the drive fluid exiting the separating chamber reliably follows the outlet channel along its entire length and is not deflected into the discharge channel by the Coanda effect. Thus, the inventive geometry of the outlet channels contributes to the reliable operation of the hydraulic switch.

[0010] In some embodiments of the invention, the cross-section of the drainage channels can be between about 5 mm 2 and about 80 mm 2By selecting the cross-section of the discharge channels, the conserved pressure—that is, the ratio of the outlet pressure at the end of the outlet channels to the inlet pressure in the inlet channel—can be influenced within wide limits, allowing the hydraulic switch to be adapted to the requirements of a downstream, hydraulically driven device. The cross-sectional area of ​​the outlet determines the counterpressure when filling the piston chambers. In some designs, the openings can also have different cross-sectional areas if the consumer exhibits asymmetric pressure losses, for example, due to connecting channels of different lengths.

[0011] In some embodiments of the invention, an input filter can be arranged at the inlet of the first and / or second feedback channel. Such an input filter prevents the feedback channel from becoming blocked, for example, by dispersed particles when dirty water is used as the drive fluid. This feature can thus increase the reliability of the hydraulic switch.

[0012] In some embodiments of the invention, the hydraulic switch can have a base plate and a cover plate, wherein a plurality of fitting elements are introduced at a distance between the base plate and the cover plate, such that these distances between the fitting elements form at least one separation chamber, one inlet channel, a first and second outlet channel, a first and second feedback channel and at least two drain channels. Such a construction of the hydraulic switch has the advantage that the fitting elements can be manufactured separately. This increases the design diversity of the hydraulic switch so that the geometry of the switch, which influences its performance, can be adjusted within wide limits. Furthermore, the inner surfaces of the hydraulic switch are prepared for a coating orHardening process accessible so that the inner surface of the separating chamber, the inlet channel, the first and second outlet channels, the first and second feedback channels and / or the optional drain channels can be at least partially hardened and / or coated with a wear protection layer.

[0013] In some embodiments of the invention, a wear-resistant layer may comprise a layer of diamond-like carbon with or without metal doping. In other embodiments of the invention, the wear-resistant layer may contain or consist of a carbide or a nitride, for example, titanium nitride and / or hard chromium and / or silicon nitride. The wear-resistant layer may be applied in a conventional manner by plasma spraying, flame spraying, thermal evaporation, magnetron sputtering, or other conventional thin-film processes.

[0014] In some embodiments of the invention, the separating chamber between the first outlet opening and the second outlet opening can be convex. Compared to known embodiments of a hydraulic switch, in which the separating chamber between the outlet openings is concave, the geometry according to the invention results in more stable operation and a lower pressure loss at the end of the outlet channels.

[0015] In some embodiments of the invention, the distance between the base plate and the cover plate, and thus the depth of the channels, can be varied. The thickness of the fitting elements directly influences the cross-section of the hydraulic switch, so that the relationship between pressure and volume can be adapted within wide limits to the requirements of the device operated with the hydraulic switch. The resulting pressure across the hydraulic switch decreases with increasing channel depth.

[0016] In some embodiments of the invention, the inlet channel can have a width of approximately 2.05 mm. This allows the pressure loss in the inlet channel to be adjusted within wide limits. This dimension also determines the velocity of the incoming jet and thus the stability of the hydraulic switch.

[0017] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0018] Figure 1a shows a hydraulic switch according to a first embodiment with the cover plate removed. Figure 1b shows the hydraulic switch according to the first

[0019] Embodiment in section.

[0020] Figure 2 shows an embodiment of an input of a

[0021] feedback channel .

[0022] Figure 3a shows a hydraulic switch according to a second embodiment with the cover plate removed.

[0023] Figure 3b shows the hydraulic switch according to the second

[0024] Embodiment in section.

[0025] Figure 3c shows individual parts of the hydraulic switch according to the second embodiment.

[0026] Figure 4 shows the relationship between volume flow and inlet pressure for different inlet channel widths.

[0027] Figure 5 shows the pressure against the volume flow as a function of the milling depth or the distance between the base plate and the cover plate.

[0028] Figure 6 shows the pressure ratio of a working fluid between the inlet channel and the outlet of the hydraulic switch.

[0029] Figure 7 shows the influence of the position of the separation edge on the switching frequency as a function of the inlet pressure.

[0030] A first embodiment of a hydraulic switch according to the present invention is explained in more detail with reference to Figure 1. The hydraulic switch 1 consists of a piece of material 15 provided with milled recesses. The piece of material 15 has a flat front side, which can be closed with a cover plate 11 after the separating chamber and the other components of the hydraulic switch have been produced by milling recesses into the material block 15.

[0031] Of course, the hydraulic switch 1 can be manufactured not only by milling, but also by a generative manufacturing process, in particular by layer-on-layer deposition and subsequent melting of a metallic powder. In other embodiments of the invention, the hydraulic switch can be manufactured by means of a casting process, at least in its raw form, which can subsequently be finished by optional machining.

[0032] An optional seal can be inserted between the material block 15 and the cover layer 11 to prevent liquid from escaping from the gap formed between the material block 15 and the cover layer 11.

[0033] The cover layer 11 can be attached to the material block 15 by screws (not shown). In other embodiments of the invention, the cover layer 11 can also be connected by gluing or welding, which can simultaneously create a seal. In yet other embodiments of the invention, the cover layer 11 can also be connected by one or more clamping elements.

[0034] The hydraulic switch 1 has a separation chamber 2, which has an inlet opening shown at the top in Figure 1a, as well as at least a first outlet opening 21 and a second outlet opening 22 opposite. The inlet opening of the separation chamber 2 is connected to an inlet channel 4. The inlet channel 4 has, at its end opposite the inlet opening of the separation chamber 2, a connecting piece 40, which can be provided, for example, with a screw thread. During operation of the hydraulic switch, the connecting piece 40 can be connected to a hose line through which a drive fluid can be supplied. The drive fluid can, for example, contain or consist of water, an oil, a glycol, or an alcohol. Abrasive particles can be dispersed in the drive fluid.

[0035] The drive fluid supplied to the separation chamber via the inlet channel 4 adheres to a wall 20 of the separation chamber 2 due to the Coanda effect and thus reaches the first or second outlet opening 21 or 22.

[0036] An outlet channel 51 and 52 begins at each of the outlet openings. Each outlet channel has a first longitudinal section 511 and 521. In the first longitudinal section 511 of the first outlet channel 51, the cross-section or cross-sectional area of ​​the outlet channel increases with the length, starting from the first outlet opening 21 of the separation chamber 2. In the same way, the cross-section of the second outlet channel 52 increases in its first longitudinal section 521, starting from the second outlet opening 22 of the separation chamber 2. The increase in the cross-section can, for example, be linear or quadratic. The first longitudinal section 511 and 521 is followed by a second longitudinal section 512 and 522, in which the respective outlet channel has a constant or almost constant cross-sectional area. At the end of the second longitudinal section 512 or 522 of the outlet channels 51 and 52 there is an outlet opening 61 and 62 respectively.When the switch is operated, the drive fluid exits alternately from the outlet openings 61 and 62 and can be supplied to a tool, for example a hammer drill.

[0037] The cross-section of the outlet channels can be polygonal or round. If the separating chamber, the inlet channel, and the outlet channels are created by milling the material block 15, a square or rectangular cross-section is particularly suitable, which is easily controlled by the milling depth and milling width and can be adapted to different applications of the hydraulic switch.

[0038] The inlet 311 of a first feedback channel 31 is located in the lower longitudinal section of the first outlet channel. The end 312 of the first feedback channel 31 is located in the separation chamber 2. In the illustrated embodiment, the end 312 of the first feedback channel 31 is arranged at the end of the inlet channel 4. In other embodiments of the invention, the end 312 can also be arranged further downstream within the separation chamber 2, for example in a region between approximately 5% and approximately 20% of the length of the separation chamber 2 measured in the flow direction.

[0039] In the same way, the inlet 321 of a second feedback channel 32 is located opposite in the second longitudinal section 522 of the second outlet channel 52. The end 322 of the second feedback channel 32 is also located in the separating chamber 2 opposite the end 312 of the first feedback channel 31.

[0040] When the hydraulic switch is in operation, a pressure fluctuation in the outlet channel caused by the consumer reaching its end position is introduced as a switching pulse into the respective feedback channel 31 or 32 and acts at its end 312 or 322 on the fluid jet coupled in via the inlet channel 4, causing it to detach from the wall 20 of the separating chamber 2 and be guided into the opposite outlet opening. A pressure peak then arises again in the outlet channel, which is guided as a switching pulse via the respective feedback channel 31 or 32 into the separating chamber 2, so that the drive fluid is again directed into the original outlet opening. In this way, a stable oscillation of the supplied drive fluid is created without the use of moving parts, which exits alternately through the outlet openings 61 and 62.The drive fluid can thus be used to operate one or more hydraulic devices and drive the oscillating piston of, for example, a hammer drill. In this case, the first outlet port 61 is connected, for example, to the lower end of the cylinder, and the second outlet port 62 is connected to the upper end of the cylinder, so that the piston located in the cylinder is alternately pressurized with the drive fluid from above and below, thereby oscillating and exerting impact energy on a drilling tool connected to the hammer drill.

[0041] In the described application, the drive fluid ejected by the hammer drill during the respective counter-movement reaches the first and second outlet channels 51 and 52 via the respective outlet openings 61 and 62 in a backflow. In order to prevent disruption of the flow of drive fluid emerging from the hydraulic switch and to empty the opposite filled chamber, each outlet channel has an associated drain channel 71 and 72, which drains away the drive fluid ejected from the piston. For this purpose, the first drain channel 71 can start in the first longitudinal section 511 of the first outlet channel 51. The second drain channel 72 can start in the first longitudinal section 522 of the second outlet channel 52, wherein the respective drain channel 71 and 72 and the first longitudinal section 511 or 521 of the respective outlet channel 51 or 52 enclose an angle of between approximately 25° and approximately 50°.This steeper arrangement of the discharge channels compared to the prior art prevents the drive fluid from the respective outlet opening 21 or 22 from being discharged directly into the discharge channels 71 or 72 without reaching the outlet openings 61 or 62, respectively, and simultaneously facilitates the outflow of the used fluid during the countermovement. The milling depth within the material block 15 can be varied as desired in some embodiments of the invention. As will be explained below with reference to Figure 5, the milling depth influences the pressure applied to the outlet openings 61 and 62, so that the hydraulic switch can be adapted to future use during its manufacture.

[0042] Figure 2 shows another enlarged section of the hydraulic switch 1. Figure 2 shows the first outlet channel 51 and part of its first longitudinal section 511 and its second longitudinal section 512. As can be seen from Figure 2, an inlet filter 35 is located at the inlet 311 of the first feedback channel 31, which prevents particles from the drive fluid from entering the feedback channel 31 and clogging it. This can increase the reliability of the hydraulic switch because the risk of the oscillation of the drive fluid coming to a standstill can be reduced. For this purpose, the inlet filter 35 can contain a porous material, for example a polymer foam or a metal foam. In other embodiments of the invention, the inlet filter 35 can be a braid, a knitted fabric or a nonwoven fabric or random fibers made of a metal or plastic, or can contain such an element.

[0043] A second embodiment of the hydraulic switch 1 according to the present invention is explained in more detail with reference to Figure 3. Identical components of the invention are provided with the same reference numerals, so that the following description is limited to the essential differences.

[0044] As Figure 3b shows, the hydraulic switch according to the second embodiment differs from the first embodiment shown in Figure 1 essentially by a modified mechanical structure. According to the second embodiment, the hydraulic switch includes a base plate 10 and a cover plate 11, with a plurality of fitting elements being arranged between the base plate and the cover plate.

[0045] 151, 152, 153, 154, and 155. The thickness of these fitting elements, and thus the distance between the base plate and the cover plate 11, is based on the milling depth of the first embodiment described above. An optional seal can be inserted between the fitting elements and the cover plate 11 or the base plate 10 to prevent unwanted fluid leakage. The fitting elements 151, 152, 153, 154, and 155, the cover plate 11, and the base plate 10 can be connected to one another by a positive connection, a material connection, clamping, or screwing.

[0046] Figure 3a shows the base plate 10 and the fitting elements 151,

[0047] 152, 153, 154 and 155 with the cover plate 11 removed. Figure 3c shows some of the fitting elements independent of the base plate 10 and at a greater distance. As can be seen from Figures 3a and 3c, the fitting elements 151, 152, 153, 154 and 155 are designed such that they can be arranged at a distance from one another on the base plate 10, and these distances form at least one separation chamber 2, one inlet channel 4, first and second outlet channels 51 and 52, and first and second feedback channels 31 and 32. In the illustrated embodiment, the fitting elements 151, 152, 153, 154 and 155 also form optional first and second outflow channels 71 and 72. The fitting elements 151, 152, 153, 154 and 155 in the form shown can be manufactured, for example, by machining, by primary forming or by a generative manufacturing process.The fitting elements 151, 152, 153, 154, and 155 are preferably made of a metal or a plastic, in particular steel or stainless steel. A particular advantage of the second embodiment shown in Figure 3 is the accessibility of the inner surfaces of the separation chamber, inlet channel, and outlet channels during the manufacturing process, so that these surfaces can be provided with an optional coating that adjusts the surface quality to a desired target value in order to support the Coanda effect of the drive fluid on the wall 20 of the separation chamber 2. Alternatively or additionally, the coating can be a wear-reducing coating, which increases the service life of the hydraulic switch. Finally, the coating can have friction-reducing properties, so that the pressure loss of the drive fluid as it passes through the hydraulic switch is reduced.Finally, the modular design of the second embodiment of the hydraulic switch allows for easy repair by replacing individual fitting elements 151, 152, 153, 154 and 155.

[0048] The hydraulic switch according to the invention has geometric parameters whose dimensioning has far-reaching effects on performance. According to the invention, relationships were identified that can be approximated using cubic planes, so that the influence of the geometry on the behavior of the hydraulic switch can be predicted and the hydraulic switch can be optimized for the intended application without the need for complex test series.

[0049] Figure 4 shows the expected inlet pressure p at the beginning of the inlet channel on the abscissa and the volume flow V of the drive fluid on the ordinate. The expected inlet pressure depends largely on the cross-sectional area at the narrowest point of the inlet channel 4. The pV curves are shown for six different inlet channel widths with a constant milling depth or thickness of the fittings. The respective widths of the inlet channel 4 and the outlet channels 71 and 72 for the different measurement curves are summarized in the following table:

[0050] The corresponding plane equation for the width b of the inlet channel 4 allows the determination of the pressure at different volume flows within the investigated measuring range: p(V,b)= 0.00422•V 2 + 9.02262•b 2 -0.31560•V •b+ 1.60487•V-36.53840•b+ 0.30664

[0051] This relationship applies to a flow rate of 601 / min to 1401 / min and an intake port with a width of 1.5 to 4 mm. The deviation has been shown to be less than 5%.

[0052] As Figure 5 shows, a similar relationship can be established for the milling depth t of the entire geometry. The milling depth also primarily determines the cross-sectional area of ​​the inlet channel 4, but also affects the overall flow cross-section of the hydraulic switch. The ratio of the measured inlet pressures p when the milling depth is doubled from 10 mm (curve A) to 20 mm (curve B) is approximately 0.36. This ratio remains constant across the entire measuring range, causing curves A and B in Figure 5 to diverge further and further with increasing flow rate.

[0053] The corresponding equation for the dependence of the inlet pressure p on the milling depth t and the volume flow V is: p(y,t)= 0.00334•V 2 + 0.01941•t 2 - 0.01974•V •t+ 0.29973•V- 0.31235•t-0.04695 This equation also applies to a flow rate between 60 and 140 rpm and a milling depth of 5 mm to 30 mm. It has been shown that the deviation of the actual measured values ​​from the predicted values ​​is less than 7%.

[0054] The cross-sectional area of ​​the first and second discharge channels 71 and 72 influences the pressure loss, or rather the actual pressure, which can be measured at the outlet openings 61 and 62. Figure 6 shows the inlet pressure on the abscissa and the average pressure loss on the ordinate. Six curves are again shown for different widths of the discharge channels 71 and 72 and the width b of the inlet channel 4, as follows:

[0055] The relationship between inlet pressure and outlet pressure can be modeled as follows:

[0056] — (7,v)= 0.00026•V 2 - 1.15189•v 2 + 0.001194•V •v-0.033860•V + Pout

[0057] 8.48938-v-8.41896

[0058] This relationship applies for a flow rate of 60 to 140 l / min and for a width of the discharge channels 71 and 72 between 2.5 mm and 4.5 mm. It has been shown that the deviations are less than 10%. All described plane equations intersect the coordinate origin, which is physically valid, since no pressure is to be expected if there is no flow rate.

[0059] Figure 7 explains the influence of the position of the separation edge 25 in the wall 20 of the separation chamber 2. The input pressure is shown on the abscissa and the switching frequency of the hydraulic switch on the left ordinate for two different positions of the separation edge. Curve C shows the measured values ​​for a separation edge arranged approximately in the middle of the separation chamber 2. Curve D shows the measured values ​​for a separation edge 25 arranged in a conventional manner at the lower end of the separation chamber 2. The comparative example shows that the inventive arrangement of the separation edge 25 approximately in the middle of the separation chamber 2 can enable a higher switching frequency and more stable switching processes.

[0060] Furthermore, Figure 7 shows the inlet pressure on the abscissa against the maximum force generated by the drive fluid at the outlet openings 61 and 62 on the right-hand ordinate. Curve A shows the force curve against the inlet pressure when the separating chamber 2 has a separation edge 25 which is arranged approximately in the middle of the separating chamber 2. Curve B shows the curve of the maximum force for a separation edge 25 which is arranged in a conventional manner at the end of the separating chamber 2. At least for an inlet pressure between approximately 25 and approximately 60 bar, the inventive arrangement of the separation edge in the separating chamber results in a higher pressure of the drive fluid at the outlet, so that a higher drive power can be transmitted to a hammer drill connected to the hydraulic switch.

[0061] Of course, the invention is not limited to the illustrated embodiments. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood as meaning that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing a priority.

[0062] The research that led to these results was funded by the European Union.

Claims

Claim 1. Hydraulic switch (1) with a separating chamber (2) having an inlet opening, a first outlet opening (21) and a second outlet opening (22), wherein the inlet opening is connected to an inlet channel (4) and the first and second outlet openings (21, 22) are each connected to an outlet channel (51, 52) which each have a first longitudinal section (521, 511) and a second longitudinal section (522, 512), wherein the first longitudinal section (511, 521) has a cross-sectional area increasing with length from the outlet opening (21, 22) and the second longitudinal section (512, 522) has a constant cross-sectional area, characterized in that the hydraulic switch (1) further comprises a first and a second feedback channel (31, 32) whose inputs (311, 321) are each located in the second longitudinal section (512, 522) one of the outlet channels (51, 52) are located and their outlets (312,322) open on opposite sides of the inlet channel (4).

2. Hydraulic switch according to claim 1, characterized in that at least one separation edge (25) is arranged in the wall (20) of the separating chamber (2), the distance of which from the inlet opening (4) can be varied and, in the hydraulic switch according to the invention, lies between about 40% and about 60% of the length of the separating chamber (2).

3. Hydraulic switch according to claim 1 or 2, further comprising a first outlet channel (71) which opens in the first longitudinal section (511) of the first outlet channel (51) and a second outlet channel (72) which opens in the first longitudinal section (522) of the second outlet channel (52), wherein the outflow channel (71, 72) and the first longitudinal section (511, 521) of the respective outlet channel (51, 52) enclose an angle between approximately 25° and approximately 50°.

4. Hydraulic switch according to claim 3, characterized in that the cross-section of the outflow channels (71, 72) is between approximately 5 mm 2 and about 80 mm 25. Hydraulic switch according to any one of claims 1 to 4, characterized in that an input filter (35) is arranged at the input (311, 321) of the first and / or second feedback channel (31, 32).

6. Hydraulic switch according to any one of claims 1 to 5, characterized in that it comprises a base plate (10) and a cover plate (11), wherein a plurality of fitting elements (15, 151, 152, 153, 154, 155) are spaced apart between the base plate (10) and the cover plate (11), such that these spaces form at least one separating chamber (2), one inlet channel (4), one first and one second outlet channel (51, 52), one first and one second feedback channel (31, 32), and optional drain channels (71, 72).

7. Hydraulic switch according to claim 6, characterized in that the distance between the base plate (10) and the cover plate (11) is between about 5 mm and about 30 mm, but can be adjusted according to the desired volume flow.

8. Hydraulic switch according to one of claims 1 to 7, characterized in that the inner surfaces of the separating chamber (20), the inlet channel (4), the first and.

9. Hydraulic switch according to any one of claims 1 to 8, characterized in that the separating chamber (2) between the first outlet opening (21) and the second outlet opening (22) is convexly shaped.

10. Hydraulic switch according to any one of claims 1 to 9, characterized in that the inlet channel (4) has a width of approximately 2.05 mm and can be varied depending on the desired inflow velocity.

11. Hydraulic switch according to any one of claims 8 to 10, characterized in that the wear-resistant layer contains or consists of DLC and / or TiN and / or Cr and / or SiN. 12.Piston-operated consumer, for example a rotary hammer, with a percussion mechanism and a hydraulic switch (1) according to one of claims 1 to 11.

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