Differential pneumatic down-the-hole hammer

Abstract

The present invention relates to the technical field of impactors for drilling, and in particular to a differential pneumatic down-the-hole hammer, in which an upper air chamber and a lower air chamber are formed in a cylinder body. In an initial state, the upper air chamber, the piston inner chamber and the lower air chamber are connected in sequence, so that the compressed gas entering through the air inlet joint can be introduced into the lower air chamber, thereby pushing the impact piston to move upward; the gas cut-off rod body of the gas distribution seat is constructed to be able to passively insert into the piston inner chamber based on the upward movement of the impact piston and cut off the connection between the upper air chamber and the piston inner chamber, so that the upper air chamber forms a pressure, and then can push the piston to move downward. The structure of the present invention eliminates the scheme of setting a fluid channel on the wall of the piston in the prior art, ensures the overall structural strength of the piston, and improves the service life; and enables the high pressure of the compressed gas to act directly on the piston without excessive loss, thereby improving the final impact velocity and impact frequency of the piston.

Description

Technical Field

[0001] The invention relates to a pneumatic impactor for drilling, in particular to a differential pneumatic down-the-hole hammer suitable for various types of drilling holes for fast drilling of hard rocks. Background Art

[0002] Pneumatic down-the-hole hammer is a relatively efficient hard rock drilling tool. It uses compressed air as the power medium and is widely used for a series of advantages such as high drilling efficiency and good drilling quality.

[0003] In the prior art, the positive cycle pneumatic impactor usually has an inner cylinder, which occupies the radial dimension of the impactor, resulting in a thinner outer tube thickness, a smaller piston diameter and an effective force-bearing area on the end face, which easily leads to problems such as piston breakage, low impact power and frequency. To solve this problem, a down-the-hole impactor without an inner cylinder has appeared in the prior art, such as disclosed in Chinese patent CN216240401U. However, the patent still has problems such as low piston movement frequency, low impact efficiency, and thin wall thickness of the outer cylinder.

[0004] To overcome the above problems, the applicant of the present patent has previously proposed a new positive circulation pneumatic down-the-hole hammer, specifically Chinese patent CN115977525B, which arranges a flow channel on the piston, eliminates the cylinder liner and its peripheral gas distribution structure, thereby simplifying the down-the-hole hammer structure and significantly increasing the wall thickness of the outer cylinder, thereby enhancing the wear resistance and greatly increasing the service life.

[0005] However, the technical solution disclosed in the patent has the following technical problems: since it is necessary to open a fluid channel on the wall of the piston, the processing is relatively complicated and the processing cost is relatively high; at the same time, since it is necessary to open a fluid channel on the wall of the piston, the load strength that the piston can withstand is weakened. Under high-intensity operation, it is easy for the piston to have cracks or cracks in the fluid channel, thereby affecting the service life of the piston and further affecting the overall service life of the impactor; in addition, since the reciprocating movement of the piston is switched by means of a narrow air flow channel opened on the wall of the piston, the instantaneous responsiveness required for the rapid switching of high and low pressures becomes relatively slow, that is, the impact frequency will be affected. Summary of the invention

[0006] In view of this, the present invention provides a differential pneumatic down-the-hole hammer, which eliminates the solution of setting a fluid channel on the wall of the piston in the prior art, thereby ensuring the overall structural strength of the piston and improving its service life; and the upper air cavity used for the piston stroke can be directly connected to the high-pressure air intake space, rather than relying on the circulation of multiple gas channels to form a pressure build-up, so that the high pressure of the compressed gas can directly act on the piston without excessive loss, thereby improving the final impact velocity and impact frequency of the piston.

[0007] The invention discloses a differential pneumatic down-the-hole hammer, comprising a cylinder body and an air inlet joint, a gas distribution seat, an impact piston and a drill bit body which are sequentially arranged in the cylinder body from top to bottom. The impact piston is constructed to be able to perform reciprocating axial movement in the cylinder body by means of a gas pressure difference. The gas distribution seat comprises a seat body part and a gas cut-off rod body part, and the seat body part is attached to the upper inner side of the cylinder body; in the cylinder body, an upper air cavity is formed between the top of the impact piston and the lower side of the seat body part, and the upper air cavity is always connected with the high-pressure air inlet cavity of the air inlet joint; a lower air cavity is also formed in the cylinder body corresponding to the lower outer side of the impact piston The impact piston has an axially through piston cavity. In the initial state, the upper air cavity, the piston cavity and the lower air cavity are connected in sequence, so that the compressed gas entering through the air inlet joint can be introduced into the lower air cavity, thereby pushing the impact piston to move upward; the air cut-off rod body is a solid body, which is located in the upper air cavity and extends toward the impact piston; and the air cut-off rod body is constructed to be able to passively insert into the piston cavity based on the upward movement of the impact piston and cut off the connection between the upper air cavity and the piston cavity, so that the upper air cavity forms a pressure, and then the piston can be pushed downward.

[0008] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, an air hole is provided on the seat body of the air distribution seat, and the upper air cavity is always connected with the high-pressure air inlet cavity by means of the air hole.

[0009] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, an air flow channel is provided on the lower end of the impact piston, and the lower air cavity and the inner cavity of the piston are kept in constant communication through the air flow channel.

[0010] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, a bottom hole slag discharge air duct for blowing away drill cuttings at the bottom of the hole is provided in the drill bit body; an opening and closing member is also provided on the lower end of the impact piston, and the opening and closing member is constructed so that in the initial state, the connection between the lower air cavity and the air flow channel and the bottom hole slag discharge air duct can be cut off, and based on the upward movement of the impact piston, the lower air cavity and the air flow channel can be connected with the bottom hole slag discharge air duct.

[0011] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, the opening and closing member is a grooved member having an air passage channel thereon, so that the inner cavity of the piston is connected with the air flow channel and the lower air cavity by means of the air passage channel.

[0012] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, a radial inner flange of the cylinder body is formed on the inner side of the cylinder body, which protrudes inwardly from the inner wall of the cylinder body in the radial direction; the upper part of the piston forms a circumferentially tight fit with the radial inner flange of the cylinder body and can perform reciprocating axial motion in the cylinder body under the guidance of the radial inner flange of the cylinder body.

[0013] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, a piston radial outer flange is formed on the outer side of the piston, which protrudes outward from the side wall of the piston in the radial direction; the piston radial outer flange is located below the radial inner flange of the cylinder body, and it forms a tight fit with the inner wall of the cylinder body to form a guide when the piston moves.

[0014] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, the lower air chamber is formed by the cylinder space portion located below the radial outer flange of the piston and surrounding the lower end of the piston, and the upper air chamber is formed by the cylinder space portion between the radial outer flange of the piston and the radial inner flange of the cylinder.

[0015] According to the differential pneumatic down-the-hole hammer disclosed in the present invention, in the cylinder body, the cylinder space portion between the radial outer flange of the piston and the radial inner flange of the cylinder body is formed as a middle air cavity, and an air outlet hole is provided on the side wall of the cylinder body. As the piston moves upward, the gas in the middle air cavity can be discharged from the cylinder body through the air outlet hole.

[0016] Beneficial effects: The present invention has a simple structure, a large piston force area, a high final impact velocity and impact frequency, and all parts of the drill tool are relatively "solid", with significantly increased service life. Specifically, the scheme of setting a fluid channel on the wall of the piston in the prior art is eliminated, which ensures the overall structural strength of the piston and increases the service life; and the upper air cavity used for the piston stroke can be directly connected to the high-pressure air intake space, rather than relying on the circulation of multiple gas channels to form a pressure blockage, so that the high pressure of the compressed gas can directly act on the piston without excessive loss, thereby increasing the final impact velocity and impact frequency of the piston.

[0017] The differential pneumatic down-the-hole hammer of the present invention will be disclosed in detail below with reference to the embodiments shown in the accompanying drawings and the accompanying reference numerals. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The overall structural diagram of the present invention is shown.

[0019] Reference numerals

[0020] 1 cylinder body, 2 air intake joint, 3 valve seat, 4 impact piston, 5 drill body, 6 opening and closing parts, 7 spline sleeve, 8 retaining ring, 9 limit bushing, 10 valve body, 11 valve spring.

[0021] 201 high pressure air intake chamber, 202 high pressure air intake passage.

[0022] 101 upper air cavity, 102 lower air cavity, 103 radial inner flange of cylinder body, 104 middle air cavity, 105 air outlet.

[0023] 301 seat body, 302 gas cut-off rod body, 303 gas hole, 304 valve seat.

[0024] 401 is a piston inner cavity, 402 is an air flow channel, and 403 is a piston radial outer flange.

[0025] 501 hole bottom slag discharge channel, 502 hole bottom gas outlet channel.

[0026] 601 air passage. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0029] Combination Figure 1 As shown, the present invention discloses a differential pneumatic down-the-hole hammer, comprising a cylindrical cylinder 1, an impact piston 4, an air inlet joint 2 and a drill bit 5. In addition, it also includes a gas distribution seat 3, an opening and closing valve, a spline sleeve 7, a retaining ring 8 and a limit bushing 9.

[0030] The specific structure is as follows: the lower end of the cylinder body 1 is connected to the spline sleeve 7 through a thread, the spline on the drill body 5 cooperates with the spline groove on the spline sleeve 7, the retaining ring 8 is stuck in the annular groove on the upper part of the spline of the drill body 5, and is blocked on the top surface of the spline sleeve 7 to prevent the drill body 54 from falling off the spline sleeve 7. In a preferred embodiment, the retaining ring 8 is a semicircular clamp; the limiting bushing 9 is sleeved on the upper periphery of the drill body 5, and the upper top surface of the limiting bushing 9 presses against the upper and lower bottom surfaces of the limiting step in the cylinder body 1 to limit the retaining ring 8. The piston is arranged in the cylinder body 1 through a sliding clearance fit, and can be pushed by gas to move axially back and forth relative to the cylinder body 1 to form impact work on the drill body 5.

[0031] Combination Figure 1As shown, in the present invention, the gas distribution seat 3 includes a seat body 301, a valve seat portion 304 and a gas cut-off rod body 302, and the seat body 301 is attached to the upper inner side of the cylinder body 1; in addition, the intake joint 2 has a high-pressure intake passage 202, and the lower part of the intake joint 2 is expanded to form a high-pressure intake cavity 201, the upper end of the valve seat portion 304 of the gas distribution seat 3 extends into the high-pressure intake cavity 201 of the intake joint 2, and the valve seat portion 304 of the gas distribution seat 3 is provided with An opening and closing valve is provided, which includes a valve body 10 and a valve spring 11. The valve body 10 and the valve spring 11 are sequentially arranged in the upper part of the valve seat part 304 from top to bottom. The bottom cylinder of the valve body 10 is interference fit in the valve spring 11. The top surface of the valve body 10 has a closed state that tightly closes the connection between the high-pressure air inlet chamber 201 and the high-pressure air inlet channel 202, and an open state that opens the connection between the high-pressure air inlet chamber 201 and the high-pressure air inlet channel 202.

[0032] In the cylinder body 1, an upper air chamber 101 is formed between the top of the impact piston 4 and the lower side of the seat body 301, and the upper air chamber 101 is always connected with the high-pressure air inlet chamber 201 of the air inlet connector 2; a lower air chamber 102 is also formed in the cylinder body 1 corresponding to the lower outer side of the impact piston 4, and the impact piston 4 has an axially penetrating piston inner chamber 401. In the initial state, the upper air chamber 101, the piston inner chamber 401 and the lower air chamber 102 are connected in sequence, so that the air entering through the air inlet connector 2 Compressed gas can be introduced into the lower air chamber 102, thereby pushing the impact piston 4 to move upward; the gas-cutting rod body 302 is a solid body, which is located in the upper air chamber 101 and extends toward the impact piston 4; and the gas-cutting rod body 302 is constructed to be able to passively insert into the piston inner chamber 401 based on the upward movement of the impact piston 4 and cut off the connection between the upper air chamber 101 and the piston inner chamber 401, so that the upper air chamber 101 forms a pressure, which can then push the piston to move downward.

[0033] That is, in the initial state, the air compressor operates, and the compressed air is pressed into the high-pressure air intake channel 202, pushing the opening and closing valve, and entering the high-pressure air intake chamber 201. Since the upper air chamber 101 and the high-pressure air intake chamber 201 are connected, the high-pressure gas can directly enter the upper air chamber 101, and then enter the piston inner chamber 401 through the upper air chamber 101, and then be introduced into the lower air chamber 102; at this time, the compressed gas in the lower air chamber 102 forms a pressure, thereby pushing the impact piston 4 to produce axial upward movement. After the impact piston 4 moves upward for a certain distance, specifically, when the cut-off rod body 302 moves to be passively inserted into the piston inner cavity 401, the cut-off rod body 302 blocks the air inlet end of the piston inner cavity 401, thereby cutting off the connection between the upper air cavity 101 and the piston inner cavity 401. At this time, the lower air cavity 102 is depressurized due to the connection with the bottom hole slag discharge airway (to be described below), so that the gas pressure in the upper air cavity 101 is greater than the gas pressure in the lower air cavity 102, so that the impact piston 4 decelerates upward and accelerates downward to impact the top of the drill bit body 5. The above process is repeated reciprocally, and the impact drilling work of the impactor of the present invention can be realized.

[0034] In the present invention, the upper air chamber 101 can be directly connected with the piston inner chamber 401, and the upper air chamber 101 is always connected with the high-pressure air inlet chamber 201, so that it is not necessary to form a connection with the air channel opened on the piston and / or the cylinder body 1 as in the prior art. This not only greatly reduces the number of grooves opened on the piston and / or the cylinder body 1, or even eliminates them, but also reduces the flow path of the high-pressure gas, thereby reducing the pressure loss of the high-pressure gas, and further improving the guarantee of the stroke force of the impact piston 4. Moreover, since the upper air chamber 101 is always connected with the high-pressure air inlet chamber 201, after the connection between the upper air chamber 101 and the piston inner chamber 401 is cut off, the high-pressure gas entering through the high-pressure air inlet chamber 201 can directly form a pressure in the upper air chamber 101, thereby improving the instantaneous responsiveness of the stroke movement of the impact piston 4, and can also ensure the impact terminal velocity and impact frequency.

[0035] The present invention has not only a simple structure, a large piston force area, a high final impact velocity and an impact frequency, but also a small number of drilling holes (or slots) in each component, making each component more "solid", thereby significantly increasing the service life.

[0036] In the embodiment of the present invention, an air hole 303 is provided on the seat body 301 of the gas distribution seat 3 , and the upper air cavity 101 is always connected with the high-pressure air inlet cavity 201 via the air hole 303 .

[0037] In the embodiment of the present invention, an air flow channel 402 is provided on the lower end of the impact piston 4 , and the lower air cavity 102 and the piston inner cavity 401 are always connected through the air flow channel 402 .

[0038] In a preferred embodiment, a bottom hole slag removal air channel 501 for blowing away drill cuttings at the bottom of the hole is provided in the drill bit body 5, so as to introduce gas into the drill bit body 5 and discharge it from the bottom hole gas outlet channel 502 provided at the end of the drill bit body 5 to blow away the drill cuttings at the bottom of the hole.

[0039] More preferably, the hole bottom slag discharge airway 501 and the lower air chamber 102 of the impactor are matched in a manner that they can be connected and cut off. Specifically, an opening and closing member 6 is attached to the lower end of the impact piston 4, and the opening and closing member 6 is configured to cut off the connection between the lower air chamber 102 and the air flow channel and the hole bottom slag discharge airway 501 in the initial state, and to enable the lower air chamber 102 and the air flow channel to be connected to the hole bottom slag discharge airway 501 based on the upward movement of the impact piston 4. In a preferred embodiment, the opening and closing member 6 is a plug, which can be a plastic body.

[0040] In the initial state, the opening and closing member 6 is inserted into the air inlet end of the bottom hole slag discharge airway 501 and blocks the bottom hole slag discharge airway 501. At this time, the high-pressure gas from the high-pressure air inlet chamber 201, the upper air chamber 101 and the piston inner chamber 401 will enter the lower air chamber 102 through the air flow channel. When the impact piston 4 produces an axial upward movement under the pressure of the lower air chamber 102, the opening and closing member 6 will move upward with the impact piston 4, so that at a certain moment (preferably, when or after the gas cut-off rod body 302 cuts off the connection between the piston inner chamber 401 and the upper air chamber 101), the opening and closing member 6 is removed from the bottom hole slag discharge airway 501, and then the lower air chamber 102 and the air flow channel are connected to the bottom hole slag discharge airway 501, and then the drill cuttings at the bottom of the hole are purged to achieve bottom hole slag discharge. Moreover, at this time, since the connection between the upper air chamber 101 and the piston inner chamber 401 is cut off, the connection between the lower air chamber 102 and the slag discharge air duct 501 at the bottom of the hole is realized, so that the lower air chamber 102 is depressurized, and the upper air chamber 101 will gradually form a pressure build-up, thereby slowing down the upward movement of the impact piston 4 and generating a downward accelerated movement to impact the top of the drill bit body 5.

[0041] In a preferred embodiment of the present invention, the opening and closing member 6 is a grooved member having an air passage 601 thereon, so that the piston inner cavity 401 is connected with the air flow channel and the lower air cavity 102 by means of the air passage 601 .

[0042] In a preferred embodiment of the present invention, a cylinder radial inner flange 103 is formed on the inner side of the cylinder 1, which protrudes inwardly from the inner wall of the cylinder 1 in the radial direction; the upper part of the piston is in close contact with the cylinder radial inner flange 103 in the circumferential direction and can make reciprocating axial movements in the cylinder 1 under the guidance of the cylinder radial inner flange 103. A piston radial outer flange 403 is formed on the outer side of the piston, which protrudes outwardly from the side wall of the piston in the radial direction; the piston radial outer flange 403 is located below the cylinder radial inner flange 103, and is in close contact with the inner wall of the cylinder 1 to form a guide when the piston moves.

[0043] In addition, the lower air chamber 102 is formed by the space portion of the cylinder body 1 located below the piston radial outer flange 403 and around the lower end of the piston, and the upper air chamber 101 is formed by the space portion of the cylinder body 1 between the piston radial outer flange 403 and the cylinder body radial inner flange 103. The space portion of the cylinder body 1 between the piston radial outer flange 403 and the cylinder body radial inner flange 103 is formed as a middle air chamber 104, and an air outlet hole is provided on the side wall of the cylinder body 1. As the piston moves upward, the gas in the middle air chamber 104 can be discharged from the cylinder body 1 through the air outlet hole 105. The formation of the middle air chamber can reduce the weight of the piston, and the axial reciprocating motion of the piston can be quickly responded to by means of the air outlet hole without delay caused by the gas in the middle air chamber.

[0044] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0046] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A differential pneumatic down-the-hole hammer, comprising a cylinder body and an air inlet joint, a gas distribution seat, an impact piston and a drill body arranged in the cylinder body from top to bottom, wherein the impact piston is configured to be able to perform reciprocating axial motion in the cylinder body by means of gas pressure difference, and characterized in that: The valve seat comprises a seat body and a gas cut-off rod body, wherein the seat body is attached to the inner side of the upper part of the cylinder body; in the cylinder body, an upper air cavity is formed between the top of the impact piston and the lower side of the seat body, and the upper air cavity is always connected with the high-pressure air inlet cavity of the air inlet joint; A lower air cavity is also formed in the cylinder body corresponding to the outer side of the lower part of the impact piston, and the impact piston has an axially penetrating piston inner cavity. In the initial state, the upper air cavity, the piston inner cavity and the lower air cavity are sequentially connected, so that the compressed gas entering through the air inlet joint can be introduced into the lower air cavity, thereby pushing the impact piston to move upward; The body of the gas-cutting rod is a solid body, which is located in the upper air cavity and extends toward the impact piston; and the body of the gas-cutting rod is configured to be passively inserted into the piston inner cavity based on the upward movement of the impact piston and cut off the communication between the upper air cavity and the piston inner cavity, so that the upper air cavity forms a pressure, and then the impact piston can be pushed to move downward; An air flow channel is provided on the lower end of the impact piston, and the lower air cavity and the piston inner cavity are kept in constant communication through the air flow channel; a bottom hole slag discharge air channel for blowing drill cuttings at the bottom of the hole is provided in the drill bit body; an opening and closing component is also provided on the lower end of the impact piston, and the opening and closing component is constructed to cut off the communication between the lower air cavity and the air flow channel and the bottom hole slag discharge air channel in an initial state, and to enable the lower air cavity and the air flow channel to be connected to the bottom hole slag discharge air channel based on the upward movement of the impact piston.

2. The differential pneumatic down-the-hole hammer according to claim 1, characterized in that: An air hole is arranged on the seat body of the gas distribution seat, and the upper air cavity is always connected with the high-pressure air inlet cavity by means of the air hole.

3. The differential pneumatic down-the-hole hammer according to claim 2, characterized in that: The opening and closing member is a grooved member having an air passage channel thereon, so that the inner cavity of the piston is connected with the air flow channel and the lower air cavity by means of the air passage channel.

4. The differential pneumatic down-the-hole hammer according to any one of claims 1 to 3, characterized in that: A cylinder radial inner flange is formed on the inner side of the cylinder body, which protrudes inwardly from the inner wall of the cylinder body in the radial direction; the upper part of the impact piston is circumferentially tightly fitted with the cylinder radial inner flange and can perform reciprocating axial movement in the cylinder body under the guidance of the cylinder radial inner flange.

5. The differential pneumatic down-the-hole hammer according to claim 4, characterized in that: A piston radial outer flange is formed on the outer side of the impact piston, which protrudes outward in the radial direction to impact the side wall of the piston; the piston radial outer flange is located below the radial inner flange of the cylinder body, and it forms a tight fit with the inner wall of the cylinder body to form a guide when the piston moves.

6. The differential pneumatic down-the-hole hammer according to claim 5, characterized in that: The lower air chamber is formed by a cylinder space portion located below a radially outer flange of the piston and surrounding a lower end of the piston, and the upper air chamber is formed by a cylinder space portion between the radially outer flange of the piston and a radially inner flange of the cylinder.

7. The differential pneumatic down-the-hole hammer according to claim 6, characterized in that: In the cylinder body, the cylinder space portion between the radial outer flange of the piston and the radial inner flange of the cylinder body is formed as a middle air cavity, and an air outlet hole is provided on the side wall of the cylinder body. As the impact piston moves upward, the gas in the middle air cavity can be discharged from the cylinder body through the air outlet hole.

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