CN115178759B - Main shaft clamping device for numerical control longitudinal cutting lathe - Google Patents

Abstract

The invention discloses a main shaft clamping device for a numerical control longitudinal cutting lathe, which comprises a shell, a main shaft and a piston, wherein the piston is slidably arranged in the shell, a closed cavity is formed between the piston and the inside of the shell, a pneumatic device for controlling the piston to axially move is arranged on the shell, a sliding sleeve is arranged in the piston, a shaft sleeve is sleeved on the main shaft, a plurality of accommodating grooves are formed in the circumferential direction of the shaft sleeve, rotatable clamping jaws are arranged in the accommodating grooves, and the piston drives the sliding sleeve to move so as to realize the rotation of the clamping jaws. The beneficial effects of the invention are as follows: through the removal of control piston, realized the clamp of main shaft and loosen, only need stop the air feed moreover after the main shaft is pressed from both sides tightly, the piston then moves certain distance to the right under the spring restoring force effect of dish spring and rubber circle to make keep off ring and wear ring separate, and then realize the high-speed rotation of main shaft, and when need press from both sides tight main shaft again, only need to let in a small amount of gas in the cavity on shift fork right side can realize the clamp of main shaft.

Description

Main shaft clamping device for numerical control longitudinal cutting lathe

Technical Field

The invention relates to a numerical control longitudinal cutting lathe, in particular to a main shaft clamping device for the numerical control longitudinal cutting lathe.

Background

In the longitudinal cutting lathe, namely the lathe adopting a transverse cutting process method, the movement track of a cutter is vertical relative to the central axis of a workpiece in metal cutting machining, namely the workpiece is rotated and moved in turning machining, and a lathe tool does not need to move along with the workpiece, so that the longitudinal cutting lathe has an essential difference from a conventional lathe.

The longitudinal cutting lathe features that the spring chuck in the main shaft holds bar for rotation and axial feeding movement, the cutter moves radially, the main shaft box is turned to excircle if the cutter is stationary, the main shaft box is stationary, the cutter is radially fed to form or cut off, and the turning of conic or forming surface is completed when the two parts move together.

The cyclic process of the machine tool generally clamps the bar material by the spindle to perform various cutting operations, and then cuts off the bar material. After the part is cut off, the spring chuck is loosened, the spindle box is retracted, and the bar stock is supported on the cutting knife by means of the force of the heavy hammer in the feeding frame. After the spindle box is retracted to the original position, the collet chuck clamps, then the cutter is retracted, and the next cycle is started. When one bar is used up, the machine tool is automatically stopped by the action of two parallel safety switches on the feeding frame and behind the machine tool body, and the integrity of the last part is ensured.

When a thin and long part or a part with higher precision is machined, a center frame is needed to be used for cutting, and at the moment, the front end of a bar is supported in a jacket of the center frame of the hard alloy to rotate, so that the excessive deformation of the part during machining is avoided, and higher machining precision is obtained. In order to reduce the remaining length of the cut bar stock, a centerless cutting may also be used when machining low precision, short parts.

The clamping of the main shaft of the existing numerical control longitudinal cutting lathe is always a difficult point, and accurate control is difficult to realize, so that the reliability of the main shaft in use is not ensured.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a main shaft clamping device for a numerical control longitudinal cutting lathe.

The aim of the invention is achieved by the following technical scheme: the utility model provides a main shaft clamping device for numerical control slitting lathe, including the main shaft, the cylinder body, lid and piston, the lid is connected with the left end of cylinder body, the right-hand member of cylinder body and the connection of the box of installation main shaft, the left end slidable mounting of piston is in the right-hand member inner chamber of lid, the right-hand member sliding fit of piston is in the cylinder body, and the cylinder body, the right-hand member of lid, the surface of piston constitutes a inclosed cavity, have the shift fork ring on the piston, the shift fork ring is located the cavity, be provided with a plurality of tracheal joint on the cylinder body, wherein the venthole of at least one tracheal joint is in communication with the cavity on shift fork ring left side, the venthole of at least one tracheal joint is in communication with the cavity on shift fork ring right side, the rubber circle of protruding shift fork ring terminal surface is all installed to the both sides of at least one tracheal joint, the piston has set up the step through-hole, install the wear ring on the step through-hole's the step surface, the internal thread connection of step through-hole has the nut, also install the wear ring on the left end face of nut, form the accommodation gap between two wear-resistant rings, the main shaft top sleeve, the axle sleeve has a plurality of accommodation grooves on the circumference direction, the accommodation groove, be located the jack catch and the tip and the second contact hole is located the tip and the second contact hole, the tip is located the tip and the tip is located on the tip and the tip hole is located on the tip hole when the tip hole is located on the tip hole.

Optionally, a disc spring is axially installed on the cover, and when the piston moves to a left stroke, the disc spring is abutted with the piston.

Optionally, a slot hole is formed in the outer circumference of the cover body, a sensing pin is mounted on the piston, the sensing pin penetrates out of the slot hole and can axially slide in the slot hole, two proximity switches are arranged on the outer side of the cover body, one proximity switch is used for detecting the left stroke of the sensing pin, and the other proximity switch is used for detecting the right stroke of the sensing pin.

Optionally, the outside of cylinder body is provided with the mounting panel, and air pipe joint and proximity switch are all installed on the mounting panel.

Optionally, an annular sealing groove is formed in the outer circumference of the shifting fork ring, and a sealing ring is arranged in the annular sealing groove.

Optionally, a sealing ring is installed on the inner cavity of the cover body at the left side of the cavity, and the sealing ring is sleeved at the left end part of the piston.

Optionally, the cylinder body on the right side of the cavity is provided with a convex ring, an annular sealing groove is formed in the inner side wall of the convex ring, and a sealing ring is arranged in the annular sealing groove.

The invention has the following advantages: according to the main shaft clamping device for the numerical control longitudinal cutting lathe, the clamping and loosening of the main shaft are realized by controlling the movement of the piston, after the main shaft is clamped, only the air supply is needed to be stopped, and the piston moves to the right for a certain distance under the action of the spring restoring force of the disc spring and the rubber ring, so that the baffle ring is separated from the wear-resisting ring, the high-speed rotation of the main shaft is realized, and when the main shaft is required to be clamped again, the main shaft can be clamped only by introducing a small amount of air into the cavity on the right side of the shifting fork.

Drawings

FIG. 1 is a schematic diagram of the structure of the present invention;

FIG. 2 is a schematic structural view of a sliding sleeve;

FIG. 3 is a schematic structural view of a claw;

FIG. 4 is a schematic view of the piston;

FIG. 5 is a schematic view of the installation of the jaws;

FIG. 6 is a schematic view of the installation of the rod body and the cover body, and the box body;

In the figure, 1-main shaft, 2-claw, 3-nut, 4-piston, 5-cylinder, 6-wear ring, 7-sliding sleeve, 8-disc spring, 9-sealing ring, 10-rubber ring, 1-air pipe joint, 12-proximity switch, 13-induction pin, 14-cavity, 15-baffle ring, 16-shifting fork ring, 17-taper hole, 18-first hole, 19-second hole, 20-slotted hole, 21-cover, 22-resisting convex part, 23-contact convex part, 24-step through hole, 25-accommodation gap, 26-shaft sleeve and 27-accommodation groove.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention.

In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without collision.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.

In the description of the present invention, it should be noted that, directions or positional relationships indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., are directions or positional relationships based on those shown in the drawings, or are directions or positional relationships conventionally put in use of the inventive product, or are directions or positional relationships conventionally understood by those skilled in the art, are merely for convenience of describing the present invention and for simplifying the description, and are not to indicate or imply that the apparatus or element to be referred to must have a specific direction, be constructed and operated in a specific direction, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless explicitly specified and limited otherwise, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

As shown in fig. 1, a spindle clamping device for a numerical control slitting lathe comprises a spindle 1, a cylinder body 5, a cover body 21 and a piston 4, wherein the cover body 21 is connected with the left end of the cylinder body 5, the right end of the cylinder body 5 is connected with a box body for mounting the spindle 1, in the embodiment, the connection between the cylinder body 5 and the cover body 21 and the connection between the cylinder body 5 and the box body are all detachable, preferably, the cylinder body 5 and the cover body 21 are detachably connected through screws, the cylinder body 5 and the box body are detachably connected through screws, the left end of the piston 4 is slidably mounted in the inner cavity of the right end of the cover body 21, the right end of the piston 4 is slidably matched in the cylinder body 5, the right end face of the cover body 21 and the outer surface of the piston 4 form a closed cavity 14, in the embodiment, the right end of the cover body 21 is provided with an inward convex ring, the middle part of cylinder body 5 is provided with inwards protruding bulge loop, piston 4 is solid of revolution structure, after piston 4 installs, piston 4's right-hand member then with the bulge loop sliding fit on the cylinder body 5, further, annular seal groove has been seted up on this bulge loop, install sealing washer 8 in the annular seal groove, thereby be sealed between the bulge loop on the right-hand member of piston 4 and cylinder body 5, and piston 4's left end then with the bulge loop sliding fit on lid 21, likewise, annular seal groove has been seted up on this bulge loop, also install sealing washer 8 in the annular seal groove, thereby be sealed between the bulge loop on the left end of piston 4 and lid 21, consequently, the tightness of cavity 14 that cylinder body 5, lid 21's right-hand member face, piston 4's surface constitutes is good.

In this embodiment, as shown in fig. 4, a shift fork ring 16 is provided on the piston 4, the shift fork ring 16 is located in the cavity 14, a plurality of air pipe joints 11 are provided on the cylinder 5, wherein the air outlet hole of at least one air pipe joint 11 is communicated with the cavity 14 on the left side of the shift fork ring 16, the air outlet hole of at least one air pipe joint 11 is communicated with the cavity 14 on the right side of the shift fork ring 16, in this embodiment, two air pipe joints 11 are provided, one air pipe joint 11 is communicated with the cavity 14 on the left side of the shift fork ring 16, the other air pipe joint 11 is communicated with the cavity 14 on the right side of the shift fork ring 16, in this embodiment, the right end face of the cover 21 or the outer circumference of the left end of the cylinder 5 is provided with a chamfer, so that after the shift fork is abutted with the left end face of the cover 21, a cavity facilitating ventilation is still formed above the abutting face of the shift fork, and after the air is introduced into the cavity, the cylinder can be pushed by the air pipe joint 11 under the action of the air after the air enters the cavity, so that the piston 4 moves to the right side, and after the air pipe joint 11 is abutted with the cavity 5, and after the air inlet is abutted with the cavity 5.

In this embodiment, rubber rings 9 protruding from the end surfaces of the shifting fork ring 16 are mounted on two sides of the shifting fork ring 16, when the shifting fork ring 16 abuts against the right end surface of the cover 21, the rubber rings 9 on the left side of the shifting fork ring 16 are extruded and deformed, and when the two air pipe joints 11 stop air supply, the shifting fork ring 16 moves to the right under the action of elastic restoring force of the rubber rings 9 for a certain stroke, so that a certain gap is generated between the shifting fork ring 16 and the right end surface of the cover 21, and similarly, when the shifting fork ring 16 abuts against the left end surface of the convex ring of the cylinder 5, the rubber rings 9 on the right side of the shifting fork ring 16 are extruded and deformed, and when the two air pipe joints 11 stop air supply, the shifting fork ring 16 moves to the left under the action of elastic restoring force of the rubber rings 9 for a certain stroke, so that a certain gap is generated between the shifting fork ring 16 and the left end surface of the convex ring of the cylinder 5.

In this embodiment, a step through hole 24 is formed in the piston 4, a wear-resistant ring 6 is installed on a step surface of the step through hole 24, a nut 3 is connected with a large hole of the step through hole 24 in a threaded manner, a wear-resistant ring 6 is also installed on a left end surface of the nut 3, a containing gap 25 is formed between the two wear-resistant rings 6, a shaft sleeve 26 is sleeved on the main shaft 1, as shown in fig. 5, a plurality of containing grooves 27 are formed in the shaft sleeve 26 in the circumferential direction, a rotatable claw 2 is installed in the containing groove 27, as shown in fig. 3, a resisting convex part 22 and a contact convex part 23 are arranged on the claw 2, an annular groove is formed on the main shaft 1, as shown in fig. 2, an inner hole of the sliding sleeve 7 comprises a first hole 18, The second hole 19 and the conical hole 17, the conical hole 17 is positioned between the first hole 18 and the second hole 19, the second hole 19 is positioned at the left side of the first hole 18, the diameter of the first hole 18 is smaller than that of the second hole 19, a baffle ring 15 is arranged at the outer side of the sliding sleeve 7, the baffle ring 15 is positioned in a containing gap 25, the contact convex part 23 is always contacted with the inner hole of the sliding sleeve 7, when the piston 4 moves to the left stroke, the abutment convex part 22 is abutted with the groove wall at the right side of the annular groove, when the piston 4 moves to the right stroke, the contact convex part 23 is contacted with the wall of the second hole 19, when the main shaft 1 needs to be clamped, the air is supplied in the cavity 14 at the right side of the shifting fork, and the cavity 14 at the left side of the shifting fork is deflated, At this time, the piston 4 moves to the left, the piston 4 drives the sliding sleeve 7 to move to the left in the process of moving to the left, because the position of the claw 2 is unchanged, in the process of moving to the left of the sliding sleeve 7, when the contact convex part 23 of the claw 2 enters the conical hole 17, the claw 2 rotates, so that the resisting convex part 22 of the claw 2 gradually approaches to the center of the main shaft 1, when the contact convex ring of the claw 2 passes through the conical hole 17 and enters the second hole 19, at this time, the claw 2 does not rotate any more, and the resisting convex part 22 abuts against the groove wall on the right side of the annular groove, so that the claw 2 clamps the main shaft 1, and because the sliding sleeve 7 moves to the left, the resisting ring 15 contacts with the wear-resisting ring 6 on the nut 3, so the main shaft 1 will brake at this moment, the spindle will stop rotating gradually, then, the cavity 14 on the right side of the shifting fork ring 16 continues to supply air, the piston 4 continues to move to the left, after the left end face of the shifting fork contacts with the right end face of the cover 21, the shifting fork moves to the left stroke at this moment, if the cavity 14 on the right side of the shifting fork ring 16 continues to keep the air supply state, the spindle is in the clamping state for a long time at this moment, the wear-resisting ring 6 on the nut 3 always contacts with the baffle ring 15, therefore, the main shaft 1 is in the rotation stopping state, and after the cavity 14 on the right side of the shifting fork ring 16 stops supplying air, the rubber ring 9 applies an elastic restoring force to the shifting fork at this moment, so that the shifting fork moves to the right side by a certain gap, the gap is generated between the baffle ring 15 and the wear-resistant ring 6 on the nut 3, at this time, the spindle 1 can continue to rotate at a high speed, after the spindle 1 needs to be clamped and locked again, only a small amount of gas is introduced into the cavity 14 on the right side of the shifting fork, so that the shifting fork can move leftwards, further the wear-resistant ring 6 on the nut 3 is contacted with the baffle ring 15, thus realizing the locking of the spindle 1, when the spindle 1 needs to be loosened, the gas is introduced into the cavity 14 on the left side of the shifting fork ring 16, the cavity 14 on the right side of the shifting fork ring 16 is deflated, at this time, the piston 4 drives the sliding sleeve 7 to move rightwards, and the contact convex part 23 enters the conical hole 17 from the first hole 18 in the process of moving rightwards, Then the retaining collar is moved into the second hole 19 from the tapered hole 17, and then the retaining collar is rotated away from the rotating shaft, and when the retaining collar is moved into the second hole 19, the retaining collar is separated from the right groove wall of the annular groove, and then the spindle 1 can continuously rotate at a high speed.

In this embodiment, the disc spring 8 is axially installed on the cover 21, when the piston 4 moves to the left stroke, the disc spring 8 is abutted with the piston 4, at this time, the disc spring 8 is in a compressed state, the disc spring 8 gives the piston 4a right elastic restoring force, and when the cavity 14 on the right side of the shifting fork stops supplying air, the piston 4 moves a certain distance to the right under the action of the elastic restoring force, so that the stop ring 15 is separated from the wear-resistant ring 6 on the nut 3, and since the rubber ring 9 and the disc spring 8 both have a right elastic restoring force on the piston 4, the reliability of the piston 4 moving to the right after the cavity 14 on the right side of the shifting fork stops supplying air is further ensured.

In this embodiment, the outer circumference of the cover 21 is provided with a slot 20, the piston 4 is provided with a sensing pin 13, the sensing pin 13 penetrates out of the slot 20, the sensing pin 13 can axially slide in the slot 20, the outer side of the cover 21 is provided with two proximity switches 12, one proximity switch 12 is used for detecting the left stroke of the sensing pin 13, the other proximity switch 12 is used for detecting the right stroke of the sensing pin 13, the proximity switch 12 is used for detecting the position of the sensing pin 13, so that ventilation and exhaust of the air pipe joint 11 can be controlled, in this embodiment, a PLC controller can be arranged, the signal output end of the proximity switch 12 is connected with the PLC controller, and the PLC controller controls ventilation and exhaust of the air pipe joint 11.

In this embodiment, the outside of the cylinder 5 is provided with a mounting plate on which the air connection 11 and the proximity switch 12 are mounted.

The working process of the invention is as follows: when the main shaft 1 needs to be clamped, the cavity 14 on the right side of the shifting fork is filled with air, the cavity 14 on the left side of the shifting fork is deflated, at the moment, the piston 4 moves leftwards, the sliding sleeve 7 is driven to move leftwards by the piston 4 in the leftwards moving process, and as the position of the claw 2 is unchanged, in the leftwards moving process of the sliding sleeve 7, after the contact convex part 23 of the claw 2 enters the conical hole 17, the claw 2 rotates, so that the abutment convex part 22 of the claw 2 gradually approaches the center of the main shaft 1, and after the contact convex ring of the claw 2 passes through the conical hole 17 and enters the second hole 19, the claw 2 does not rotate any more, the abutment convex part 22 abuts against the groove wall on the right side of the annular groove, so that the claw 2 clamps the main shaft 1, and as the sliding sleeve 7 moves leftwards, the abutment ring 15 contacts with the wear-resisting ring 6 on the nut 3, at the moment, the main shaft 1 brakes, the rotating shaft gradually stops rotating, then, the cavity 14 on the right side of the shifting fork ring 16 continues to supply air, the piston 4 continues to move left, when the left end face of the shifting fork contacts with the right end face of the cover 21, the shifting fork moves to the left stroke, the proximity switch 12 on the left side detects the sensing pin 13, the cavity 14 on the right side of the shifting fork ring 16 is controlled to stop supplying air, the rubber ring 9 applies a right elastic restoring force to the shifting fork, the disc spring 8 applies a right elastic restoring force to the piston 4, so that the shifting fork moves to the right side by a certain gap, the stop ring 15 and the wear ring 6 on the nut 3 generate a gap, the main shaft 1 can continue to rotate at a high speed, and after the main shaft 1 is clamped and locked again, only a small amount of air is required to be introduced into the cavity 14 on the right side of the shifting fork, so that the shifting fork moves to the left, and the wear ring 6 on the nut 3 contacts with the stop ring 15, thus realizing locking of the main shaft 1, when the main shaft 1 needs to be loosened, air is introduced into the cavity 14 at the left side of the shifting fork ring 16, the cavity 14 at the right side of the shifting fork ring 16 is deflated, at the moment, the piston 4 drives the sliding sleeve 7 to move rightwards, the contact convex part 23 enters the conical hole 17 from the first hole 18 and then enters the second hole 19 from the conical hole 17 in the right moving process of the sliding sleeve 7, at the moment, the retaining convex ring is far away from the rotating shaft to rotate, when the retaining convex ring enters the second hole 19, the retaining convex ring is separated from the right side groove wall of the annular groove, at the moment, the main shaft 1 can continuously rotate at a high speed, and after the sensing pin 13 is detected by the right connector switch, the air supply in the cavity 14 at the left side of the shifting fork is controlled to stop.

Although the present invention has been described with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements and changes may be made without departing from the spirit and principles of the present invention.

Claims (5)

1. A main shaft clamping device for numerical control slitting lathe which characterized in that: comprises a main shaft, a cylinder body, a cover body and a piston, wherein the cover body is connected with the left end of the cylinder body, the right end of the cylinder body is connected with a box body provided with the main shaft, the left end of the piston is slidably arranged in an inner cavity at the right end of the cover body, the right end of the piston is slidably matched in the cylinder body, the right end face of the cover body and the outer surface of the piston form a closed cavity, a shifting fork ring is arranged on the piston and is positioned in the cavity, a plurality of air pipe joints are arranged on the cylinder body, an air outlet hole of at least one air pipe joint is communicated with the cavity at the left side of the shifting fork ring, an air outlet hole of at least one air pipe joint is communicated with the cavity at the right side of the shifting fork ring, rubber rings protruding out of the end faces of the shifting fork ring are arranged at two sides of the ring, step through holes are formed in the piston, a wear-resisting ring is arranged on the step face of the step through holes, the nut is connected with the large hole of the step through hole in an internal thread way, the wear-resisting rings are also arranged on the left end face of the nut, an accommodating gap is formed between the two wear-resisting rings, the spindle is sleeved with the shaft sleeve, a plurality of accommodating grooves are formed in the circumferential direction of the shaft sleeve, rotatable clamping claws are arranged in the accommodating grooves, the clamping claws are provided with resisting convex parts and contact convex parts, the spindle is provided with an annular groove, the inner hole of the sliding sleeve comprises a first hole, a second hole and a conical hole, the conical hole is positioned between the first hole and the second hole, the second hole is positioned at the left side of the first hole, the diameter of the first hole is smaller than the diameter of the second hole, a baffle ring is arranged at the outer side of the sliding sleeve and positioned in the accommodating gap, the contact convex parts are always contacted with the inner hole of the sliding sleeve, when the piston moves to the left stroke, the resisting convex part is abutted with the groove wall on the right side of the annular groove, when the piston moves to the right stroke, the contact convex part is in contact with the wall of the second hole, an annular sealing groove is formed in the outer circumference of the shifting fork ring, a sealing ring is arranged in the annular sealing groove, a sealing ring is arranged on the inner cavity of the cover body on the left side of the cavity, and the sealing ring is sleeved at the left end part of the piston.

2. A spindle clamp for a numerically controlled slitting machine as set forth in claim 1, wherein: and when the piston moves to a left stroke, the disc spring is abutted with the piston.

3. A spindle clamping device for a numerically controlled slitting machine as set forth in claim 1 or 2, wherein: the outer circumference of the cover body is provided with a slotted hole, the piston is provided with a sensing pin, the sensing pin penetrates out of the slotted hole and can axially slide in the slotted hole, the outer side of the cover body is provided with two proximity switches, one proximity switch is used for detecting the left stroke of the sensing pin, and the other proximity switch is used for detecting the right stroke of the sensing pin.

4. A spindle clamp for a numerically controlled slitting machine as set forth in claim 3, wherein: the outside of cylinder body is provided with the mounting panel, the air pipe joint with proximity switch is all installed on the mounting panel.

5. A spindle clamp for a numerically controlled slitting machine as set forth in claim 3, wherein: the cylinder body on the right side of the cavity is provided with a convex ring, an annular sealing groove is formed in the inner side wall of the convex ring, and a sealing ring is arranged in the annular sealing groove.