Hydraulic hammering device

Abstract

This hydraulic hammer device is provided with a dual damper having: a pushing piston (5); a damping piston (6); a hydraulic pushing chamber (51) that produces propulsion in the pushing piston (5); a hydraulic damping chamber (61) that produces propulsion in the damping piston (6); a drain circuit (81) that is provided to continuously isolate the hydraulic pushing chamber (51) and the hydraulic damping chamber (61) from each other, and returns oil leaked from points of sliding contact between the pistons (5) and (6) to a tank; and a first diaphragm (9) provided along the drain circuit (81). A pushing pathway (71) that connects the hydraulic pushing chamber (51) and a high-pressure circuit (7) is provided with only a check valve (10) that allows pressurized oil to be supplied to the hydraulic pushing chamber (51) from the high-pressure circuit (7) and restricts the pressurized oil from flowing in the opposite direction. A damping pathway (72) that connects the hydraulic damping chamber (61) and the high-pressure circuit (7) is provided with only a second diaphragm (11).

Description

Technical Field

[0001] 5 The present invention relates to a hydraulic hammering device, such as a rock drill and a breaker, for crushing bedrock and the like by delivering blows to a tool, such as a rod and a chisel. 10 Background Art

[0002] A drilling machine crushes bedrock R, which is a crushing target, by delivering blow energy generated in a hammering mechanism 3 of a rock drill main body 1 to a 15 tool including a shank rod 2, a rod 22, and a bit 21, as illustrated in a basic configuration in FIGS. 1A to 1C. The rock drill main body 1 is constantly provided with a propulsive force toward the bedrock R by a known feed mechanism, and the bit penetrates deep into the bedrock R 20 while crushing the bedrock R and drills a blast hole BH.

[0003] Not all of the blow energy is consumed for crushing the bedrock R, and a portion of the blow energy bounces back from the bedrock R as reflected energy Er. The 25 reflected energy Er on this occasion is transmitted from the bit 21 to the rock drill main body 1 by way of the rod 22 and the shank rod 2, and causes damage to a constituent device, such as the rock drill main body 1 or 2023357676   09 Jun 2026 the shank rod 2, and also becomes a factor causing reduction in drilling efficiency.

[0004] Therefore, the applicants have developed a "dual 5 damper" from early on as an effective means to counter the reflected energy Er and have improved the dual damper from day to day (PTLs 1 and 2). A dual damper 4 includes a pushing piston 5 and a damping piston 6 as major constituent components, and a 10 throttle 90 is provided in a high-pressure circuit 7 and check valves 91 and 92 are provided in a pushing passage 71 and a damping passage 72, respectively, as illustrated in a prior art in FIG. 6.

[0005] 15 The dual damper 4 achieves at the same time both a "cushioning action" to damp the reflected energy Er and thereby protect the rock drill main body 1 from being damaged and a "pushing action" to stably press the bit 21 against the bedrock R to transmit blow energy to the 20 bedrock without loss, at a high level. Since a detailed configuration of other constituent components and a mechanism of action of the dual damper 4 are described in detail in PTL 1 and PTL 2 (in particular, paragraphs 0070 to 0072 and FIG. 6), 25 description thereof will be omitted herein.

[0006] As used herein, the term "tool" may be synonymous with the bit (21), and the term "transmission members" 2023357676   09 Jun 2026 may be a term collectively referring to a group of members including the rod (22), a sleeve (23), the shank rod (2), and a bush (12). Note that, although a description is omitted herein, when the hydraulic 5 hammering device is a breaker, the rod (or the chisel) functions as both a "tool" and a "transmission member". Citation List Patent Literature 10

[0007] PTL1: JP H09-109064 A PTL2: WO 2017 / 110793 Summary of Invention 15

[0008] However, there is room for improvement in the dual damper. That is, there have been a case where in a hydraulic 20 hammering device capable of delivering a large number of blows by increasing the number of blows, response speed of the dual damper is insufficient and the cushioning action and the pushing action are not sufficiently exerted. In addition, there is a case where when an 25 operating condition for the hydraulic hammering device is not properly controlled according to conditions of the bedrock R, the cushioning action and the pushing action are not sufficiently exerted. 2023357676   09 Jun 2026

[0009] Accordingly, the present invention has been made in view of the problem in a hydraulic hammering device as described above. It may be desirable to provide a 5 hydraulic hammering device that is capable of exerting a cushioning action and a pushing action of a dual damper under various conditions.

[0010] 10 In this regard, there is provided a hydraulic hammering device including: a transmission member configured to transmit a propulsive force toward a crushing target side to a tool; a hammering mechanism 15 configured to strike a blow on a rear portion of the transmission member; a pushing piston disposed immediately behind the transmission member, the pushing piston having a smaller propulsive force (F5f) than a propulsive force (F1) of a device main body of the 20 hydraulic hammering device; a damping piston positioned behind the pushing piston and disposed to slide reciprocally against the pushing piston in forward and backward directions, the damping piston having a greater propulsive force (F6f) than the propulsive force of the 25 device main body of the hydraulic hammering device; wherein the following formula is satisfied: F5f < F1 < F6f; a pushing chamber configured to generate a propulsive force in the pushing piston; a damping chamber 2023357676   09 Jun 2026 configured to generate a propulsive force in the damping piston; a damper pressure source configured to supply the pushing chamber and the damping chamber with hydraulic fluid by way of a high-pressure circuit; a drain circuit 5 provided in constant isolation from the pushing chamber and the damping chamber and configured to discharge a leakage of hydraulic fluid from a location of sliding contact between the pushing piston and the damping piston to a tank; a first throttle interposed in the drain 10 circuit; a pushing passage connecting the pushing chamber and the high-pressure circuit; and a damping passage connecting the damping chamber and the high-pressure circuit, wherein in a supply path of hydraulic fluid from an outlet for hydraulic fluid of the damper pressure 15 source to the pushing chamber by way of the high-pressure circuit and the pushing passage, only a check valve configured to, while allowing supply of hydraulic fluid from the damper pressure source to the pushing chamber, restrict an outflow of hydraulic fluid from the pushing 20 chamber to the damper pressure source is provided as a hydraulic fluid control element, and in a supply path of hydraulic fluid from the outlet for hydraulic fluid of the damper pressure source to the damping chamber by way of the high-pressure circuit and the damping passage, 25 only a second throttle is provided as a hydraulic fluid control element.

[0011] 2023357676   09 Jun 2026 According to the hydraulic hammering device of the first invention, since in the supply path of hydraulic fluid including the high-pressure circuit and the pushing passage, only the check valve configured to, while 5 allowing supply of hydraulic fluid from the damper pressure source to the pushing chamber, restrict an outflow of hydraulic fluid from the pushing chamber to the damper pressure source is provided and in the supply path of hydraulic fluid including the high-pressure 10 circuit and the damping passage, only the second throttle is provided, operational responses of the pushing piston and the damping piston are improved and a cushioning action and a pushing action can be exerted at a high level. That is, the first invention is suitable for a 15 hydraulic hammering device capable of delivering a large number of blows.

[0012] In addition, in a hydraulic hammering device of a 20 second invention, after the hammering mechanism strikes a blow on the transmission member, the pushing piston advances following the transmission member, the transmission member advancing preceding the pushing piston, and when reflected energy propagating from the 25 tool to a device main body of the hydraulic hammering device arrives at the pushing piston, the pushing piston and the damping piston are separated from each other.

[0013] 2023357676   09 Jun 2026 According to the hydraulic hammering device of the second invention, after the hammering mechanism strikes a blow on the transmission member, the pushing piston advances following the transmission member, the 5 transmission member advancing preceding the pushing piston, and when reflected energy propagating from the tool to the main body of the hydraulic hammering device arrives at the pushing piston, the pushing piston and the damping piston are separated from each other. 10 Therefore, the pushing piston is caused to separately receive the transmission tool that is to retract due to propagation of reflected energy, retract, and exert a first cushioning action, and subsequently, the pushing piston and the damping piston are caused to 15 retract in one body and exert a second cushioning action. Although during a time for which the transmission tool performs idle running during retraction (hereinafter, referred to as a retraction idle running time), a cushioning action is not exerted, the dual 20 damper can exert a cushioning action without delay as a whole since according to the second invention, the retraction idle running time is reduced by a time for which the first cushioning action is exerted.

[0014] 25 The second invention is suitable for a phase in which the pushing piston and the damping piston advance and retract in one body, that is, in a phase in which the dual damper advances and retracts in a region on a 2023357676   09 Jun 2026 negative displacement side, which will be described later. In particular, since in a state in which an advancing propulsive force of the rock drill main body is 5 dominant over an advancing propulsive force of the dual damper (hereinafter, referred to as a feed-dominant state), the dual damper advances and retracts in the region on the negative displacement side in all phases in which first reflected energy, that is, a first wave of 10 reflected energy, propagates and second and subsequent waves of reflected energy propagate, the second invention is suitable for the hydraulic hammering device in the feed-dominant state.

[0015] 15 Note that in the second invention, a mechanism in which the pushing piston and the damping piston are separated from each other when reflected energy arrives at the pushing piston is achieved by an improvement in a response when the pushing piston advances among 20 improvement in operational responses of the pushing piston and the damping piston, which is an advantageous effect of the first invention. Therefore, it is needless to say that a pushing action that is an original function of the pushing piston is also improved. 25

[0016] In addition, in a hydraulic hammering device of a third invention, after the hammering mechanism strikes a blow on the transmission member, only the pushing piston 2023357676   09 Jun 2026 advances relative to the damping piston that stops at an advancing stroke end, such that the pushing piston follows the transmission member, the transmission member advancing preceding the pushing piston, and before a 5 timing when first reflected energy propagating from the tool to a device main body of the hydraulic hammering device arrives at the pushing piston, the pushing piston comes into contact with a rear portion of the transmission member and presses the transmission member. 10

[0017] According to the hydraulic hammering device of the third invention, after the hammering mechanism strikes a blow on the transmission member, only the pushing piston advances following the transmission member, the 15 transmission member advancing preceding the pushing piston, relative to the damping piston, which stops at the advancing stroke end, and before a timing when first reflected energy propagating from the tool to the device body of the hydraulic hammering device arrives at the 20 pushing piston, the pushing piston comes into contact with a rear portion of the transmission member and presses the transmission member. Therefore, the pushing piston is caused to separately receive the transmission tool, which is to 25 retract due to propagation of reflected energy, while the pushing piston is in contact with the transmission tool, retract, and exert a first cushioning action, and subsequently, the pushing piston and the damping piston 2023357676   09 Jun 2026 are caused to retract in one body and exert a second cushioning action.

[0018] Therefore, the retraction idle running time of the 5 transmission tool during which a cushioning action is not exerted is eliminated, and the dual damper can exert a cushioning action further without delay as a whole. In particular, since in a state in which the advancing propulsive force of the dual damper is dominant 10 over the advancing propulsive force of the rock drill main body (hereinafter, referred to as a damper-dominant state) and a state in which the advancing propulsive force of the dual damper is proper with respect to the advancing propulsive force of the rock drill main body 15 (hereinafter, referred to as a damper-proper state), the pushing piston advances and retracts while largely protruding into a region on the positive displacement side, which will be described later, relative to the damping piston in a phase in which the first wave of 20 reflected energy propagates, the third invention is suitable for the hydraulic hammering device in the damper-dominant state and the damper-proper state.

[0019] Note that in the third invention, a mechanism in 25 which before a timing when the first reflected energy arrives at the pushing piston, the pushing piston comes into contact with the rear portion of the transmission member and presses the transmission member is achieved by 2023357676   09 Jun 2026 a more prominent improvement in a response when the pushing piston advances among improvement in operational responses of the pushing piston and the damping piston, which is an advantageous effect of the first invention. 5 Therefore, it is needless to say that in the third invention, the pushing action that is the original function of the pushing piston has also been considerably improved.

[0020] 10 Incidentally, the third invention is made by focusing only a relation between the first wave of reflected energy and the pushing piston, and no relation between the second and subsequent waves of reflected energy and the pushing piston is defined. 15 This is because the first wave of reflected energy is extremely larger than the second and subsequent waves of reflected energy and in order to cause the entire reflected energy to die out in a short period of time, it is most important to cushion the first wave of reflected 20 energy without time lag. Advantageous Effects of Invention

[0021] As discussed above, according to the present inventions, it is possible to provide a hydraulic 25 hammering device that is capable of exerting a cushioning action and a pushing action of a dual damper under various conditions. 2023357676   09 Jun 2026 Brief Description of Drawings

[0022] FIGS. 1A to 1C are explanatory diagrams of a basic configuration a rock drill indicative of one embodiment 5 of a hydraulic hammering device according to the present invention, and illustrate a state in which a pushing piston and a damping piston come into contact with each other and the damping piston is positioned at a front stroke end thereof at the time of striking (a damper- 10 proper state), a state in which the pushing piston has advanced relative to the damping piston at the time of striking (a damper-dominant state), and a state in which both the pushing piston and the damping piston have retracted at the time of striking (a feed-dominant 15 state), respectively; FIG. 2 is a longitudinal sectional view of a cushioning mechanism of the rock drill indicative of the one embodiment of the present invention; FIG. 3 is an operational explanatory diagram of the 20 cushioning mechanism in FIG. 2 and illustrates a relationship between displacements of the pushing piston (in the drawing, also referred to as PP) and the damping piston (in the drawing, also referred to as DP) in the damper-proper state and arrival times of reflected 25 energy; FIG. 4 is another operational explanatory diagram of the cushioning mechanism in FIG. 2 and illustrates a relationship between displacements of the pushing piston 2023357676   09 Jun 2026 (in the drawing, also referred to as PP) and the damping piston (in the drawing, also referred to as DP) in the damper-dominant state and arrival times of reflected energy; 5 FIG. 5 is still another operational explanatory diagram of the cushioning mechanism in FIG. 2 and illustrates a relationship between displacements of the pushing piston (in the drawing, also referred to as PP) and the damping piston (in the drawing, also referred to 10 as DP) in the feed-dominant state and arrival times of reflected energy; FIG. 6 is a longitudinal sectional view of a cushioning mechanism of a conventional rock drill; and FIG. 7 is a longitudinal sectional view of a 15 cushioning mechanism of a rock drill indicative of a variation of the present invention. Detailed Description of Specific Embodiments

[0023] 20 Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate. Note that the same constituent components as or corresponding constituent components to those in the above-described prior art or a known structure are 25 designated by the same reference signs and detailed description thereof will be omitted as appropriate. In addition, the drawings are schematic. Therefore, it should be noted that relations between thicknesses and 2023357676   09 Jun 2026 planar dimensions, ratios, and the like are different from actual ones and portions having different dimensional relationships and ratios from one another among the drawings are included. 5 In addition, the following embodiment indicates devices and methods to embody the technical idea of the present invention by way of example, and the technical idea of the present invention does not limit the materials, shapes, structures, arrangements, and the like 10 of the constituent components to those described below.

[0024] (Basic Configuration) In a basic configuration of a rock drill of the present embodiment, as illustrated in FIGS. 1A to 1C, a 15 shank rod 2 is inserted into a front end section of a rock drill main body 1 and a hammering mechanism 3 for delivering a blow to the shank rod 2 is disposed behind the shank rod 2. A rod 22 having a bit 21 for drilling attached thereto is connected to the shank rod 2 by means 20 of a sleeve 23.

[0025] The rock drill main body 1 includes a known chuck driver (illustration is omitted) that provides rotation to the shank rod 2 through a known chuck (illustration is 25 omitted). To the chuck driver, a bush 12 that comes into contact with a large diameter section rear end 2a of the shank rod 2 is held slidably in the forward and backward 2023357676   09 Jun 2026 directions inside the chuck driver, as illustrated in FIG. 2. A pushing piston 5 and a damping piston 6 are disposed behind the bush 12 and form a dual damper 4.

[0026] 5 A middle step section 13, a rear step section 14, and a front step section 15 are formed on the rock drill main body 1. The damping piston 6 is a cylindrical piston and is held movable in the forward and backward directions between the middle step section 13 and the 10 rear step section 14. In the damping piston 6, a fluid feeding hole 62 and drain holes 63a and 63b are formed. An annular pushing chamber 51 is formed on the inner diameter side of the fluid feeding hole 62.

[0027] 15 The pushing piston 5 is a flanged cylindrical piston and is held movable in the forward and backward directions between the front step section 15 and a front end face of the damping piston 6. An outer diameter surface of the pushing piston 5 and an inner diameter 20 surface of the damping piston 6 are in sliding contact with each other. Note that a position of the middle step section 13 is defined as a reference position u0 of movement of the dual damper 4 and displacements on a front side and a 25 rear side of the reference position u0 are assumed to be positive displacement u+ and negative displacement u-, respectively.

[0028] 2023357676   09 Jun 2026 On an inner peripheral surface of the rock drill main body 1, a pushing port 16 is formed at a position facing the fluid feeding hole 62 of the damping piston 6. On the inner peripheral surface of the rock drill main 5 body 1, drain ports 17 are formed in the front and rear of the pushing port 16. Further, on the inner peripheral surface of the rock drill main body 1, a damping chamber 61 is formed between the pushing port 16 and a front drain port 17. 10 To the rock drill main body 1, a hydraulic pump P serving as a damper pressure source is connected by way of a high-pressure circuit 7 and a tank T is also connected by way of a drain circuit 8.

[0029] 15 In the present embodiment, one end of the high-pressure circuit 7 is connected to the hydraulic pump P and the other end splits into a pushing passage 71 and a damping passage 72, and the pushing passage 71 and the damping passage 72 are connected to the pushing port 16 20 and the damping chamber 61, respectively. In the above configuration, only a check valve 10 is interposed in the pushing passage 71 as a hydraulic fluid control element. The check valve 10 is provided as a direction-restricting means for, while allowing an inflow 25 of hydraulic fluid from the side on which the hydraulic pump P is placed to the side on which the pushing port 16 is formed, restricting an outflow of hydraulic fluid from 2023357676   09 Jun 2026 the side on which the pushing port 16 is formed to the side on which the hydraulic pump P is placed.

[0030] In addition, only a throttle 11 is interposed in the 5 damping passage 72 as a hydraulic fluid control element. The throttle 11 is provided as a direction-restricting means for, while allowing an inflow of hydraulic fluid from the side on which the hydraulic pump P is placed to the side on which the damping chamber 61 is formed, 10 restricting an outflow of hydraulic fluid from the side on which the damping chamber 61 is formed to the side on which the hydraulic pump P is placed. That is, while resistance of hydraulic fluid passing through a throttle increases in proportion to a square of 15 flow velocity, the throttle 11 of the present invention acts as a direction-restricting means since outflow velocity is higher than inflow velocity.

[0031] As described in the foregoing, in the present 20 embodiment, hydraulic fluid is supplied from an outlet for hydraulic fluid of the hydraulic pump P to the pushing chamber 51 by way of the high-pressure circuit 7 and the pushing passage 71. Further, only the check valve 10 is interposed in the pushing passage 71. In 25 other words, in the pushing passage 71 that is a supply path of hydraulic fluid to the pushing chamber 51, only the check valve 10 is interposed as a hydraulic fluid control element. 2023357676   09 Jun 2026 In addition, in the present embodiment, hydraulic fluid is supplied from the outlet for hydraulic fluid of the hydraulic pump P to the damping chamber 61 by way of the high-pressure circuit 7 and the damping passage 72. 5 Further, only the throttle 11 is interposed in the damping passage 72. In other words, in the damping passage 72 that is a supply path of hydraulic fluid to the damping chamber 61, only the throttle 11 is interposed as a hydraulic fluid control element. 10 Note that it may be configured such that a decompression means is disposed between the outlet for hydraulic fluid of the hydraulic pump P and the high-pressure circuit 7. This configuration is a configuration in which a damper pressure source is formed 15 by the hydraulic pump P and the decompression means.

[0032] The tank T is connected to one end of the drain circuit 8, and the other end of the drain circuit 8 splits into drain passages 81. The drain passages 81 are 20 connected to the drain ports 17. A variable throttle 9 is interposed in the drain circuit 8. Note that the variable throttle 9 constitutes a "first throttle" in the present invention and the throttle 11 constitutes a "second throttle" in the present invention. 25

[0033] When a forward propulsive force that is provided to the rock drill main body 1 by a feed mechanism is denoted by F1 and propulsive forces when the pushing piston 5 and 2023357676   09 Jun 2026 the damping piston 6 advance by hydraulic fluid supplied from the side on which the hydraulic pump P is placed to the sides on which the pushing chamber 51 and the damping chamber 61 are formed by the above-described 5 configuration are denoted by F5f and F6f, respectively, a relationship among F1, F5f, and F6f is set to satisfy the formula (1) below: F5f < F1 < F6f . . . (1).

[0034] 10 (States of Dual Damper) Next, a damper-proper state, a damper-dominant state, and a feed-dominant state of the dual damper will be described. When a relationship among propulsive forces of the 15 dual damper 4 and a propulsive force of the rock drill main body 1 is maintained in the above-described formula (1), the pushing piston 5 retracts and a rear end of the pushing piston 5 comes into contact with a front end of the damping piston 6, and the damping piston 6 advances 20 and the front end of the damping piston 6 comes into contact with the middle step section 13 and comes to a stop. That is, when a striking piston 31 strikes a blow on the shank rod 2, the rear end of the pushing piston 5 and 25 the front end of the damping piston 6 come into contact with each other and a contact surface therebetween is positioned at the reference position u0, and this state 2023357676   09 Jun 2026 is defined as the damper-proper state of the dual damper 4 (FIG. 1A).

[0035] There is a case where in the relationship among the 5 propulsive forces of the dual damper 4 and the propulsive force of the rock drill main body 1, the propulsive forces of the dual damper 4 are more dominant than the propulsive force of the rock drill main body 1. Examples of such a case include a case where to prevent a curved 10 hole from being generated in bedrock having many cracks, pressure of hydraulic fluid supplied to the feed mechanism is intentionally set to a pressure lower than a proper pressure. In this case, a behavior in which the damping piston 15 6 advances and comes to a stop with the front end thereof coming into contact with the middle step section 13 is the same as that in the damper-proper state. On the other hand, the pushing piston 5 separates from the damping piston 6, advances, and comes into contact with 20 the shank rod 2. On this occasion, since advancing speed of the rock drill main body 1 is low, the pushing piston 5 and the damping piston 6 are maintained separated from each other.

[0036] 25 That is, when the striking piston 31 strikes a blow on the shank rod 2, the rear end of the pushing piston 5 is located at a position where the rear end has advanced away from the reference position u0, and this state is 2023357676   09 Jun 2026 defined as the damper-dominant state of the dual damper 4 (FIG. 1B). Note that although in FIG. 1B, a state in which the pushing piston 5 is in contact with the front step section 15, which is an advancing stroke end of the 5 pushing piston 5, is illustrated for descriptive purposes, separation distance between the pushing piston 5 and the damping piston 6 is extremely small.

[0037] There is a case where in the relationship among the 10 propulsive forces of the dual damper 4 and the propulsive force of the rock drill main body 1, the propulsive force of the rock drill main body 1 is more dominant than the propulsive forces of the dual damper 4. Examples of such a case include a case where while drilling operation is 15 performed with the pressure of hydraulic fluid to be supplied to the feed mechanism set to a proper pressure, rock quality becomes soft, repulsion from the bedrock decreases, and the propulsive force of the rock drill main body 1 becomes relatively excessive. 20 In this case, the pushing piston 5 comes into contact with the damping piston 6, and further, the pushing piston 5 and the damping piston 6 retract in one body and come to a stop at a position where the propulsive force of the damping piston 6 and a reactive 25 force of the propulsive force of the rock drill main body 1 are balanced.

[0038] 2023357676   09 Jun 2026 That is, when the striking piston 31 strikes a blow on the shank rod 2, the front end of the damping piston 6 is located at a position where the front end has retracted beyond the reference position u0, and this 5 state is defined as the feed-dominant state of the dual damper 4 (FIG. 1C). Note that although in FIG. 1C, a state in which the damping piston 6 is in contact with the rear step section 14, which is a retracting stroke end of the damping piston 6, is illustrated for 10 descriptive purposes, retracting stopping distance of the damping piston is small.

[0039] Next, operation of the rock drill main body 1 and the dual damper 4 will be described with respect to a 15 cushioning action and a pushing action in this order. (Cushioning Action) As illustrated in FIGS. 1A to 1C, in a drilling operation, when the striking piston 31 of the hammering mechanism 3 strikes a blow on the shank rod 2, blow 20 energy of the striking piston 31 is transmitted from the shank rod 2 to the bit 21 by way of the rod 22, and the bit 21 penetrates and crushes bedrock R, which is a crushing target. On this occasion, the pushing piston 5 advances following the shank rod 2. Reflected energy Er 25 is transmitted from the bit 21 to the dual damper 4 by way of the rod 22, the shank rod 2, and the bush 12 and is cushioned.

[0040] 2023357676   09 Jun 2026 When the reflected energy Er is transmitted to the dual damper 4, first, the pushing piston 5 separately retracts and comes into contact with the damping piston 6, and subsequently, the pushing piston 5 and the damping 5 piston 6 retract in one body relatively with respect to the rock drill main body 1. When the damping piston 5 separately retracts, hydraulic fluid in the pushing chamber 51 has the pressure thereof raised because an outflow thereof to the 10 side on which the hydraulic pump P is placed is restricted by the check valve 10 and leaks accompanied by heat generation from clearance at a location of sliding contact. When the damping piston 6 retracts, hydraulic fluid 15 in the damping chamber 61 has the pressure thereof raised because an outflow thereof to the side on which the hydraulic pump P is placed is restricted by the throttle 11 and leaks accompanied by heat generation from clearance at a location of sliding contact. Note that 20 when the pushing piston 5 and the damping piston 6 retract in one body, hydraulic fluid does not flow out from the pushing chamber 51.

[0041] Since the hydraulic fluid having leaked from the 25 clearance at the locations of sliding contact is collected to the tank T with heat energy retained, the reflected energy Er is damped by consuming energy equivalent to the heat energy. 2023357676   09 Jun 2026 On this occasion, while the leaking hydraulic fluid is discharged to the tank T by way of the drain ports 17, the drain passages 81, and the drain circuit 8, the variable throttle 9 is interposed in the drain circuit 8 5 and controls the upper limit of the amount of leakage of the leaking hydraulic fluid, that is, the amount of consumed fluid in the dual damper 4. As described above, since the dual damper 4 of the present invention constantly exerts a cushioning action 10 in all of the damper-proper state, the damper-dominant state, and the feed-dominant state, it is possible to prevent damage to the rock drill main body 1, a tool, and transmission members.

[0042] 15 When reactive forces when the pushing piston 5 and the damping piston 6 retract, that is, cushioning propulsive forces, are denoted by F5r and F6r, respectively, since a forward propulsive force of the rock drill main body 1 is F1 as described above and a 20 reactive force from the bedrock is thus equally F1, a relationship among F1, F5r, and F6r is set to a relationship between the formulae (2) and (3) below by setting the amount of adjustment of the variable throttle 9. 25 (Degree of Opening of Variable Throttle 9: Maximum) F1 < F5r < F6r . . . (2) (Degree of Opening of Variable Throttle 9: Full Close) F1 < F5r = F6r . . . (3) 2023357676   09 Jun 2026

[0043] (Pushing Action) The rock drill main body 1, which temporarily retracted due to the reflected energy Er from the bedrock 5 R, advances until reaching a state in which the bit 21 comes into contact with the bedrock R, that is, to a predetermined striking position, by the time a next strike is performed. On this occasion, since the total mass of the 10 transmission members including the tool is substantially smaller than the mass of the rock drill main body 1, the pushing piston 5 and the damping piston 6 advance more rapidly than the rock drill main body 1, advance until reaching an advancing stroke end of the damping piston 6, 15 that is, until the dual damper 4 is brought into the damper-proper state, and come to a stop.

[0044] If the bit 21 has not come into contact with the bedrock R at the timing when the damping piston 6 reaches 20 the advancing stroke end, the pushing piston 5, separating from the damping piston 6, advances and brings the bit 21 into contact with the bedrock R by means of the transmission members. While pushing action of a conventional dual damper 25 brings the bit 21 into close contact with the bedrock R on this occasion, the pushing action of the dual damper 4 of the present embodiment is reinforced since operational 2023357676   09 Jun 2026 responses of the pushing piston 5 and the damping piston 6 have been improved. Although subsequently, the rock drill main body 1 advances, the hammering mechanism 3 strikes a next blow 5 in one of the damper-proper state, the damper-dominant state, and the feed-dominant state according to a setting of a propulsive force of the rock drill main body 1 with respect to characteristics of the bedrock R and a relative relationship between a propulsive force of the 10 rock drill main body 1 and propulsive forces of the dual damper 4, as described before.

[0045] (Reflected Energy and Displacement of Dual Damper) Next, a manner in which the dual damper 4 cushions 15 transmitted reflected energy Er will be described. FIGS. 3 to 5 illustrate behaviors of the pushing piston 5 and the damping piston 6 after the hydraulic hammering device of the present invention strikes a blow in the damper-proper state, the damper-dominant state, 20 and the feed-dominant state of the dual damper 4, respectively. In addition, behaviors of the dual damper 4 of the prior art are illustrated in the same drawings for comparison. The ordinates in the drawings represent displacement 25 of the pushing piston 5 and the damping piston 6, and the position of the front end of the damping piston 6 when the damping piston 6 is in a state of coming into contact with the middle step section 13, which is the advancing 2023357676   09 Jun 2026 stroke end of the damping piston 6, is defined as the reference position u0 and displacement in the forward direction (the leftward direction in FIGS. 1A to 1C) and displacement in the rearward direction (the rightward 5 direction in FIGS. 1A to 1C) are defined as positive displacement and negative displacement, respectively. Note that in the drawings, the upper side of the reference position u0 and the lower side of the reference position u0 are defined as a positive displacement region 10 and a negative displacement region, respectively.

[0046] The abscissae in the drawings represent time, and t1 to t7 are defined as follows: t0: an initial time before the striking piston 31 15 strikes a blow; t1: a time when the striking piston 31 strikes a blow on the shank rod 2; t2: a time when a first wave of reflected energy arrives at the pushing piston 5; 20         t3: a time when the pushing piston 5 retracts due to the first wave of reflected energy and comes into contact with the damping piston 6; t4: a time when a second wave of reflected energy arrives at the pushing piston 5; 25         t5: a time when a third wave of reflected energy arrives at the pushing piston 5; t6: a time when fourth and subsequent waves of reflected energy arrive at the pushing piston 5; and 2023357676   09 Jun 2026 t7: a time when all the reflected energy disappears in a stable manner.

[0047] The displacement of the pushing piston 5 of the 5 present embodiment is illustrated by a double line provided with shading (hereinafter, refer to as "shaded line"), and the displacement of the damping piston 6 of the present embodiment is illustrated by a solid line. The displacements of the conventional pushing piston 10 5 and damping piston 6 are illustrated by a single dashed line without using different line types since the pushing piston 5 separately operates in the positive displacement region and the pushing piston 5 and the damping piston 6 constantly operate in one body in the negative 15 displacement region.

[0048] FIG. 3 illustrates behaviors when the striking piston 31 strikes a blow on the shank rod 2 while the dual damper 4 is in the damper-proper state and 20 subsequently the dual damper 4 cushions reflected energy Er having propagated from transmission tools. At t0, a rear end section of the pushing piston 5 and a front end section of the damping piston 6 stop at the position u0. 25 At t1, when the striking piston 31 strikes a blow on the shank rod 2, the shank rod 2 advances forward according to the magnitude of provided blow energy. An 2023357676   09 Jun 2026 advance amount Smax at this time is a maximum displacement of the shank rod in a hammering cycle. The pushing piston 5 advances following the advancing shank rod 2 and comes to a stop while pressing 5 the shank rod 2. The pressing state appears in the diagram as a flat portion of the shaded line for a time At.

[0049] At t2, when the first wave of reflected energy Er is 10 transmitted from the shank rod 2 to the pushing piston 5, the pushing piston 5 retracts without delay since the pushing piston 5 had come into contact with and started to press the shank rod 2 at a time the time At before t2 and cushions the first wave of reflected energy Er. 15 At t3, the pushing piston 5 and the damping piston 6 come into contact with each other. Subsequently, the pushing piston 5 and the damping piston 6 retract in one body and cushion the first wave of reflected energy Er.

[0050] 20 Although a propulsive force (advancing force) due to hydraulic pressure acts on the pushing piston 5 and the damping piston 6 retracting in one body, the pushing piston 5 and the damping piston 6 turn to an advancing stroke when energy associated with the propulsive force 25 exceeds the reflected energy. On this occasion, since no throttle is disposed between the pushing piston 5 and a hydraulic source, a larger amount of hydraulic fluid is supplied to the 2023357676   09 Jun 2026 pushing piston 5 than to the damping piston 6. Therefore, advancing speed of the pushing piston 5 becomes faster than the damping piston 6, and the pushing piston 5 and the damping piston 6 separately advance. 5 In the meantime, inside the transmission tools, a portion of the reflected energy is reflected by a rear end section of the shank rod 2, propagates to the front side of the transmission tools, is reflected by a front end section of the bit 21, and propagates to the rear 10 side of the transmission tools again as a second wave of reflected energy Er.

[0051] At t4, the second wave of reflected energy Er is transmitted to the pushing piston 5. 15 On this occasion, the pushing piston 5 has advanced beyond the reference position u0 and has been brought into a state of being separated from the damping piston 6. When the reflected energy Er propagates, the pushing piston 5 retracts and cushions the second wave of 20 reflected energy Er. The pushing piston 5 comes into contact with the damping piston 6, and the pushing piston 5 and the damping piston 6 retract in one body and cushion the second wave of reflected energy Er. 25

[0052] The pushing piston 5 and the damping piston 6 having retracted in one body turn to an advancing stroke when 2023357676   09 Jun 2026 energy associated with the propulsive force thereof exceeds the reflected energy. On this occasion, since advancing speed of the pushing piston 5 is faster than advancing speed of the 5 damping piston 6, the pushing piston 5 and the damping piston 6 separately advance. In the meantime, inside the transmission tools, a portion of the reflected energy is reflected by the rear end section of the shank rod 2, propagates to the front side of the transmission tools, 10 is reflected by the front end section of the bit 21, and propagates to the rear side of the transmission tools again as a third wave of reflected energy Er.

[0053] At t5, the third wave of reflected energy Er is 15 transmitted to the pushing piston 5. On this occasion, the pushing piston 5 has advanced beyond the reference position u0 and has been brought into a state of being separated from the damping piston 6. When the reflected energy Er propagates, the pushing 20 piston 5 retracts and cushions the third wave of reflected energy Er. The pushing piston 5 comes into contact with the damping piston 6, and the pushing piston 5 and the damping piston 6 retract in one body and cushion the 25 third wave of reflected energy Er.

[0054] The pushing piston 5 and the damping piston 6 having retracted in one body turn to an advancing stroke when 2023357676   09 Jun 2026 the propulsive force thereof exceeds retracting propulsive force associated with the reflected energy. On this occasion, since advancing speed of the pushing piston 5 is faster than advancing speed of the 5 damping piston 6, the pushing piston 5 and the damping piston 6 separately advance. In the meantime, inside the transmission tools, a reflected wave propagates to the front side of the transmission tools with the rear end section of the shank 10 rod 2 as a free end and propagates to the rear side of the transmission tool again as a fourth wave of reflected energy Er with the front end section of the bit 21 as a free end.

[0055] 15 At t6, the fourth wave of reflected energy Er is transmitted to the pushing piston 5. On this occasion, the pushing piston 5 has the rear end in contact with the front end of the damping piston 6 and a contact surface therebetween is positioned at the 20 reference position u0. When the reflected energy Er propagates, the pushing piston 5 and the damping piston 6 retract in one body and cushion the fourth wave of reflected energy Er. At t7, the reflected energy Er is damped and dies 25 out by the cushioning action of the dual damper 4.

[0056] A positive gradient of the shaded line is steeper than the dashed line, and it can be seen that advancing 2023357676   09 Jun 2026 speed of the pushing piston 5 in the embodiment according to the present invention is faster than the prior art. In addition, when phases in which the second and third waves of reflected energy Er are transmitted are compared 5 between the embodiment according to the present invention and the prior art, it can be seen that in the embodiment according to the present invention, a cushioning action is exerted without delay since the pushing piston 5 is located in the positive displacement region. 10 Further, when focusing on the behavior of the damping piston 6, depths of valleys of the curve in the negative displacement region in the embodiment according to the present invention are shallower than that in the prior art, and it can be seen that the cushioning action 15 is reinforced. It can be seen that the embodiment of the present invention causes the reflected energy to die out faster than the prior art and performs the next strike with sufficient margin.

[0057] 20 Next, a relationship between the behavior of the dual damper 4 in the damper-proper state and the first to third inventions will be mentioned. An advantageous effect that the advancing speed of the pushing piston 5 is considerably improved in a phase 25 until the first wave of reflected energy arrives and an advantageous effect that the advancing speed of the pushing piston 5 is faster than the advancing speed of 2023357676   09 Jun 2026 the damping piston 6 in all phases are advantageous effects associated with the first invention. In addition, an advantageous effect that the pushing piston 5 is located in the positive displacement region 5 in a phase in which the second and third waves of reflected energy are transmitted is an advantageous effect associated with the second invention. Further, an advantageous effect that the pushing piston 5 has advanced the same distance as the maximum displacement 10 amount of the shank rod 2 and stopped in a phase in which the first reflected energy arrives is an advantageous effect associated with the third invention.

[0058] FIG. 4 illustrates behaviors when the striking 15 piston 31 strikes a blow on the shank rod 2 while the dual damper 4 is in the damper-dominant state and subsequently the dual damper 4 cushions reflected energy Er having propagated from the transmission tools. A difference from the damper-proper state is that 20 the striking piston 31 strikes a blow on the shank rod 2 at a position where the rear end of the pushing piston 5 has advanced beyond the reference position u0. Note that since behaviors of the pushing piston 5 and the damping piston 6 are similar to those in the damper-proper state, 25 detailed description thereof is omitted.

[0059] 2023357676   09 Jun 2026 Next, a relationship between the behavior of the dual damper 4 in the damper-dominant state and the first to third inventions will be mentioned. An advantageous effect that the advancing speed of 5 the pushing piston 5 is considerably improved in a phase until the first wave of reflected energy arrives and an advantageous effect that the advancing speed of the pushing piston 5 is faster than the advancing speed of the damping piston 6 in all phases are advantageous 10 effects associated with the first invention. In addition, an advantageous effect that the pushing piston 5 advances further than the conventional dual damper 4 in a phase in which the second and third waves of reflected energy arrive is an advantageous effect 15 associated with the second invention. Further, an advantageous effect that the pushing piston 5 has advanced the same distance as the maximum displacement amount of the shank rod 2 and stopped in a phase in which the first reflected energy arrives is an advantageous 20 effect associated with the third invention.

[0060] FIG. 5 illustrates behaviors when the striking piston 31 strikes a blow on the shank rod 2 while the dual damper 4 is in the feed-dominant state and 25 subsequently the dual damper 4 cushions reflected energy Er having propagated from the transmission tools. A difference from the damper-proper state is that the striking piston 31 strikes a blow on the shank rod 2 2023357676   09 Jun 2026 at a position where the pushing piston 5 and the damping piston 6 retract in one body beyond the reference position u0 and that the pushing piston 5 and the damping piston 6 operate in the negative displacement region. 5

[0061] Since the feed-dominant state is not an environment where the cushioning action and the pushing action of the dual damper 4 can be sufficiently exerted, it is reasonable that comparing the embodiment according to the 10 present invention with the prior art and asserting superiority of the embodiment as in the cases of the damper-proper state and the damper-dominant state are difficult. However, even in the case of the feeddominant state, it can be clearly seen that when the 15 pushing piston 5 advances, the pushing piston 5 is separated from the damping piston 6, that is, the advancing speed of the pushing piston 5 is faster than the advancing speed of the damping piston 6.

[0062] 20 Next, a relationship between the behavior of the dual damper 4 in the feed-dominant state and the first to third inventions will be mentioned. An advantageous effect that the advancing speed of the pushing piston 5 is faster than the advancing speed 25 of the damping piston 6 in substantially all the phases is an advantageous effect associated with the first invention. In addition, an advantageous effect that the pushing piston 5 is separated from the damping piston 6 2023357676   09 Jun 2026 in phases in which the first, second, and third waves of reflected energy are transmitted is an advantageous effect associated with the second invention. In the feed-dominant state, no advantageous effect associated 5 with the third invention is exerted.

[0063] (Variation) A variation of the present invention will be described below using FIG. 7 with reference to FIGS. 1A 10 to 1C and FIGS. 2 to 6. A hydraulic hammering device of the variation includes, as illustrated in FIG. 7, the above-described pushing piston 5, damping piston 6, pushing chamber 51, damping chamber 61, drain circuit 8, first throttle 15 (variable throttle) 9, pushing passage 71, damping passage 72, and high-pressure circuit 7. In addition to the above, the hydraulic hammering device of the variation includes, as illustrated in FIG. 7, a damper pressure source 100. 20

[0064] The damper pressure source 100 includes a hydraulic pump P that is shared by a plurality of pieces of hydraulic equipment. Further, the damper pressure source 100 includes a hammering pressure control means 101 and a 25 damper pressure control means 102. The hammering pressure control means 101 controls pressure of hydraulic fluid to be supplied from the hydraulic pump P to the hammering mechanism 3. 2023357676   09 Jun 2026 The damper pressure control means 102 is connected to the hydraulic pump P by way of the hammering pressure control means 101, and hydraulic fluid having pressure controlled by the hammering pressure control means 101 is 5 supplied to the damper pressure control means 102.

[0065] In addition, the damper pressure control means 102 includes a first decompression valve 102a, a second decompression valve 102b, a pilot operation switching 10 valve 102c, and a throttle 102d. The first decompression valve 102a is a decompression valve configured to control pilot pressure to be supplied to the second decompression valve 102b, based on feed pressure of the feed mechanism that 15 provides the rock drill main body 1 with a forward propulsive force. The second decompression valve 102b is a decompression valve configured to control hydraulic fluid to be supplied from the hydraulic pump P to the dual 20 damper 4 by way of the hammering pressure control means 101 to a damper pressure, based on the pilot pressure supplied from the first decompression valve 102a.

[0066] The pilot operation switching valve 102c is a 25 switching valve that is provided on the downstream side of the second decompression valve 102b and that is configured to selectively switch connections of the high- 2023357676   09 Jun 2026 pressure circuit 7 to a drain Dr and to the second decompression valve 102b. Although the pilot operation switching valve 102c communicates the high-pressure circuit 7 with the drain 5 Dr when a rotation mechanism configured to rotate the shank rod 2 does not operate, the pilot operation switching valve 102c communicates the high-pressure circuit 7 with the second decompression valve 102b when the rotation mechanism operates and pilot pressure based 10 on rotational pressure is supplied. The throttle 102d is interposed between the pilot operation switching valve 102c and the high-pressure circuit 7 and is a throttle configured to protect hydraulic control equipment from shock of hydraulic fluid 15 that, when the dual damper 4 exerts a cushioning action, propagates from the side on which the dual damper 4 is placed to the side on which the damper pressure control means 102 is placed by way of the high-pressure circuit 7. 20

[0067] Both rock drill main bodies 1 of the present invention are mounted on a guide shell of a drilling machine (illustration is omitted) that includes a known traveling carriage, boom, and guide shell, and the 25 hydraulic pump P, the hammering pressure control means 101, and the damper pressure control means 102 are mounted on the traveling carriage. 2023357676   09 Jun 2026 The damper pressure control means 102 and the rock drill main body 1 are connected to each other by a hose 7a, and between a connection point to the hose 7a and the pushing passage 71 and the damping passage 72, a main 5 body passage 7b is formed. The hose 7a and the main body passage 7b constitute the high-pressure circuit 7 of the present invention.

[0068] As described in the foregoing, the damper pressure 10 source 100 is formed by the hydraulic pump P configured to supply the plurality of pieces of hydraulic equipment with hydraulic fluid, the hammering pressure control means 101 configured to control pressure of hydraulic fluid supplied from the hydraulic pump P to the hammering 15 mechanism 3, and the damper pressure control means 102 configured to further control pressure of hydraulic fluid having pressure controlled by the hammering pressure control means 101 and supply the high-pressure circuit 7 with the hydraulic fluid. 20 That is, the damper pressure source 100 supplies the pushing chamber 51 and the damping chamber 61 with hydraulic fluid by way of the high-pressure circuit 7.

[0069] In addition, in the hydraulic hammering device of 25 the variation, as with the above-described embodiment, only the check valve 10 that, while allowing supply of hydraulic fluid from the damper pressure source 100 to the pushing chamber 51, restricts an outflow of hydraulic 2023357676   09 Jun 2026 fluid from the pushing chamber 51 to the damper pressure source 100 is provided in the supply path of hydraulic fluid including the high-pressure circuit 7 and the pushing passage 71. 5 Further, in the hydraulic hammering device of the variation, as with the above-described embodiment, only the second throttle (throttle 11) is provided in the supply path of hydraulic fluid including the high-pressure circuit 7 and the damping passage 72. 10

[0070] Although the embodiment of the present invention was described above with reference to the accompanying drawings, the hydraulic hammering device according to the present invention is not limited to the above-described 15 embodiment, and it is apparent that, unless departing from the spirit and scope of the present invention, other various modifications and alterations to the respective components can be made. 20

[0071] It is to be understood that, for any prior art referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other 25 country.

[0072] In the claims which follow and in the preceding description, except where the context requires otherwise 2023357676   09 Jun 2026 due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to 5 preclude the presence or addition of further features in various embodiments of the invention. Reference Signs List

[0073] 10 1 Rock drill main body (device main body of hydraulic hammering device) 2 Shank rod 2a Large diameter section rear end 3 Hammering mechanism 15 4 Dual damper 5 Pushing piston 6 Damping piston 7 High-pressure circuit 7a Hose 20 7b Main body passage 8 Drain circuit 9 Variable throttle (first throttle) 10 Check valve 11 Throttle (second throttle) 25 12 Bush 13 Middle step section (reference position) 14 Rear step section 15 Front step section 2023357676   09 Jun 2026 16 Pushing port 17 Drain port 21 Bit 22 Rod 5 23 Sleeve 31 Striking piston 51 Pushing chamber 61 Damping chamber 62 Fluid feeding hole 10 63a, 63b Drain hole 71 Pushing passage 72 Damping passage 81 Drain passage 90 Throttle 15 91 Check valve 92 Check valve 100 Damper pressure source 101 Hammering pressure control means 102 Damper pressure control means 20 102a First decompression valve 102b Second decompression valve 102c Pilot operation switching valve 102d Throttle Er Reflected energy 25 P Hydraulic pump R Bedrock Smax Shank rod maximum displacement amount (advance amount) 2023357676   09 Jun 2026 T Tank u Displacement of dual damper u+ Positive displacement u- Negative displacement 5 u0 Reference position

Claims

1. A hydraulic hammering device comprising: a transmission member configured to transmit a5 propulsive force toward a crushing target side to a tool;a hammering mechanism configured to strike a blow on a rear portion of the transmission member;a pushing piston disposed immediately behind the transmission member, the pushing piston having a smaller10 propulsive force (F5f) than a propulsive force (F1) of a device main body of the hydraulic hammering device;a damping piston positioned behind the pushing piston and disposed to slide reciprocally against the pushing piston in forward and backward directions, the15 damping piston having a greater propulsive force (F6f) than the propulsive force (F1) of the device main body of the hydraulic hammering device; wherein the following formula is satisfied: F5f < F1 < F6f;a pushing chamber configured to generate a20 propulsive force in the pushing piston;a damping chamber configured to generate a propulsive force in the damping piston;a damper pressure source configured to supply the pushing chamber and the damping chamber with hydraulic 25 fluid by way of a high-pressure circuit;a drain circuit provided in constant isolation from the pushing chamber and the damping chamber and configured to discharge a leakage of hydraulic fluid from2023357676   09 Jun 2026a location of sliding contact between the pushing piston and the damping piston to a tank;a first throttle interposed in the drain circuit;a pushing passage connecting the pushing chamber and5 the high-pressure circuit; anda damping passage connecting the damping chamber and the high-pressure circuit, whereinin a supply path of hydraulic fluid from an outlet for hydraulic fluid of the damper pressure source to the10 pushing chamber by way of the high-pressure circuit and the pushing passage, only a check valve configured to, while allowing supply of hydraulic fluid from the damper pressure source to the pushing chamber, restrict an outflow of hydraulic fluid from the pushing chamber to15 the damper pressure source is provided as a hydraulic fluid control element, andin a supply path of hydraulic fluid from the outlet for hydraulic fluid of the damper pressure source to the damping chamber by way of the high-pressure circuit and20 the damping passage, only a second throttle is provided as a hydraulic fluid control element.

2. The hydraulic hammering device according to claim 1, wherein25 after the hammering mechanism strikes a blow on the transmission member,2023357676   09 Jun 2026the pushing piston advances following the transmission member, the transmission member advancing preceding the pushing piston, andwhen reflected energy propagating from the tool to a5 device main body of the hydraulic hammering device arrives at the pushing piston, the pushing piston and the damping piston are separated from each other.

3. The hydraulic hammering device according to10 claim 1 or 2, whereinafter the hammering mechanism strikes a blow on the transmission member,only the pushing piston advances relative to the damping piston that stops at an advancing stroke end,15 such that the pushing piston follows the transmission member, the transmission member advancing preceding the pushing piston, andbefore a timing when first reflected energy propagating from the tool to a device main body of the20 hydraulic hammering device arrives at the pushing piston, the pushing piston comes into contact with a rear portion of the transmission member and presses the transmission member.25

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