CN116696889A

CN116696889A - Pressure self-releasing type extrusion oil cylinder

Info

Publication number: CN116696889A
Application number: CN202310963834.1A
Authority: CN
Inventors: 李江烨; 易发; 杨星辉
Original assignee: Sanhe Oil Cylinder Changzhou Co ltd
Current assignee: Sanhe Oil Cylinder Changzhou Co ltd
Priority date: 2023-08-02
Filing date: 2023-08-02
Publication date: 2023-09-05
Anticipated expiration: 2043-08-02
Also published as: CN116696889B

Abstract

The invention relates to the technical field of oil cylinders, in particular to a pressure self-releasing type extrusion oil cylinder which comprises a cylinder barrel, a cylinder cover, a piston and a piston rod, wherein the rear end of the cylinder barrel is of a closed structure, a first rear oil port is arranged on the side wall of the rear end of the cylinder barrel, and an oil leakage path is arranged on the middle side wall of the cylinder barrel; the side wall of the cylinder cover is provided with a first front oil port and a second front oil port, and the second front oil port is communicated with the oil drainage path; the oil drainage path comprises a first oil path and a second oil path, an oil path plug is arranged at the intersection of the first oil path and the second oil path, an adjusting stud is arranged in the first oil path, and a spring is arranged between the adjusting stud and the oil path plug; the oil pressure driving oil duct plug in the rodless oil cavity extrudes the spring, so that hydraulic oil enters the second front oil port through the first oil path and the second oil path, the oil pressure on two sides of the piston is balanced, the piston rod is pushed to the oil port position of the first oil path by the pressure released by deformation of the box body, the self-release of the pressure of the box body is realized, the occurrence of the outward protruding phenomenon of the side wall of the box body can be effectively avoided, and the forming quality of products is improved.

Description

Pressure self-releasing type extrusion oil cylinder

Technical Field

The invention relates to the technical field of oil cylinders, in particular to a pressure self-releasing extrusion oil cylinder.

Background

When carrying out extrusion to box class part, the extrusion hydro-cylinder that adopts sets up at last casing top more, through extrudeing downwards so that upper and lower casing realize the pressfitting, because the inside cavity structure that is of box, consequently the extrusion hydro-cylinder is when pressing upper and lower casing, causes the box lateral wall to appear the condition of evagination easily, influences product shaping quality.

Disclosure of Invention

The technical problems to be solved by the invention are as follows: the pressure self-releasing extrusion oil cylinder effectively solves the problems in the background technology.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the pressure self-releasing type extrusion oil cylinder is arranged above the compression box body and comprises a cylinder barrel with an opening at the front end, a cylinder cover arranged at the front end of the cylinder barrel, a piston and a piston rod, wherein the piston and the piston rod are arranged in the cylinder barrel in a sliding manner and are of an integrated structure, and a rod oil cavity and a rodless oil cavity are formed in the cylinder barrel by the piston;

the rear end of the cylinder barrel is of a closed structure, a first rear oil port communicated with the rodless oil cavity is formed in the side wall of the rear end of the cylinder barrel, and an oil leakage path is formed in the middle side wall of the cylinder barrel;

a first front oil port and a second front oil port which are communicated with the rod oil cavity are arranged on the side wall of the cylinder cover, and the second front oil port is communicated with the oil drainage path;

the oil drainage path comprises a first oil path penetrating along the radial direction and a second oil path penetrating towards the cylinder cover perpendicular to the first oil path, an oil path plug is arranged at the intersection of the first oil path and the second oil path, an adjusting stud is arranged in the first oil path, and a spring is arranged between the adjusting stud and the oil path plug;

when hydraulic oil in the rodless oil cavity enters the first oil way, the oil pressure drives the oil way plug to extrude the spring, so that the hydraulic oil in the rodless oil cavity enters the second front oil port through the first oil way and the second oil way, at the moment, the oil pressures at two sides of the piston are balanced, and the piston rod is pushed to the oil port position of the first oil way by the pressure released by deformation of the box body.

Further, an axial distance between a side surface of the cylinder cover facing the rodless oil cavity and the first oil path is greater than the thickness of the piston.

Further, a first groove is formed in one side face, facing the rodless oil cavity, of the piston, and the first groove is located at the outer edge of the piston;

and the depth of the first groove is smaller than or equal to the radius of the oil inlet hole of the first oil way, and when the piston is pushed back and displaced to a position close to the oil port of the first oil way by releasing pressure, one end face of the piston protruding out of the first groove is coplanar with the axis of the first oil way.

Further, a rear ring groove is formed in the position, close to the first rear oil port, of the inner hole of the cylinder barrel.

Further, the first front oil port and the second front oil port both comprise a main oil inlet path along the radial direction and a branch oil inlet path vertically arranged at the end part of the main oil inlet path;

the end part of the main oil inlet path of the second front oil port, which is far away from the branch oil inlet path, is provided with a sealing plug, the main oil inlet path of the second front oil port is provided with a connecting oil path, the second oil path is communicated with the connecting oil path, and the branch oil inlet path is communicated with the rod oil cavity.

Further, a front ring groove is formed in one end face, facing the piston, of the cylinder cover;

the front ring groove is communicated with the two branch oil inlets of the first front oil port and the second front oil port.

Further, a second groove is formed in the contact surface of the cylinder barrel and the piston, and the second groove is arranged in the center of the bottom of the cylinder barrel and is coaxial with the piston;

and the first rear oil port radially penetrates through the cylinder barrel, and the first groove and the second groove are arranged in the projection range of the first rear oil port along the axis, so that a stepped oil inlet cavity is formed between the first groove and the second groove, and centering oil pressure is applied to the piston.

Further, the first oil path comprises a first cavity and a second cavity along the axis direction, the diameter of the first cavity is larger than that of the second cavity, and a thread structure is arranged at one end, away from the second cavity, of the first cavity;

the adjusting stud is fixed at the end part of the first cavity through the thread structure;

the oil duct plug is arranged at one end of the first cavity close to the second cavity, the second oil way is blocked through the side surface of the oil duct plug, and the distance between the adjusting stud and the oil duct plug is larger than the length of the shaft section of the oil duct plug, which is beyond the second oil way, towards one end of the second cavity.

Further, positioning grooves for embedding the ends of the springs are formed in the opposite surfaces of the adjusting studs and the oil duct plugs;

a positioning column is arranged at the center of the positioning groove between the adjusting stud and the oil duct plug, and protrudes out of the upper surface of the positioning groove;

the outer cylindrical surface of the oil duct plug is provided with a plugging shaft section and a guide shaft section along the axial direction, when the oil duct plug is closed, the plugging shaft section corresponds to the second oil way, and the guide shaft section gradually contracts inwards along the direction away from the plugging shaft section.

Further, a boss extends out of the contact surface of the cylinder cover and the cylinder barrel, and the boss is embedded into an oil cavity of the cylinder barrel;

a first sealing structure is arranged at the joint of the contact end surface of the cylinder cover and the cylinder barrel at the second oil way, and a second sealing structure is arranged on the boss;

and a sliding bearing and a third sealing structure are arranged on the sliding contact surface of the cylinder cover and the piston rod.

The beneficial effects of the invention are as follows: according to the invention, through the arrangement of the oil discharging way and the second front oil port, the oil passage plug arranged in the first oil way can be opened by utilizing the oil pressure in the rodless oil cavity in the state that the piston rod is completely extended, so that the oil pressure balance at two sides of the piston is realized, the piston can freely move between the rodless oil cavity and the rod-containing oil cavity, the piston rod is enabled to be retracted by the pressure generated by the deformation of the box body so as to realize the self-release of the pressure of the box body, the occurrence of the outward protruding phenomenon of the side wall of the box body can be effectively avoided, and the forming quality of products is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.

Fig. 1 is a schematic diagram of a state in which a first rear oil port starts to be filled in an embodiment of the present invention;

FIG. 2 is a schematic diagram showing a state where oil pressure in a rodless oil chamber is insufficient to open an oil passage plug in an embodiment of the present invention;

fig. 3 is a schematic diagram showing a state in which an oil pressure in a rodless oil chamber opens an oil passage plug in an embodiment of the present invention;

FIG. 4 is a schematic view showing a state in which a piston is pushed to retract by a release pressure in an embodiment of the present invention;

fig. 5 is a schematic diagram illustrating a state in which the first front oil port starts to be filled in the embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view of a rear ring groove according to an embodiment of the present invention;

FIG. 7 is a schematic cross-sectional view of a front ring groove according to an embodiment of the present invention;

FIG. 8 is a schematic diagram illustrating installation of an adjustment stud and an oil passage plug in a first oil passage according to an embodiment of the present disclosure;

fig. 9 is a schematic structural diagram of an adjusting stud and an oil passage plug according to an embodiment of the present invention.

Reference numerals: 100. a cylinder; 200. a cylinder cover; 300. a piston; 400. a piston rod; 500. a rodless oil chamber; 600. a rod oil cavity; 1. a first rear oil port; 2. an oil discharge path; 21. a first oil passage; 211. a first cavity; 212. a second cavity; 22. a second oil path; 3. a first front oil port; a. a main oil inlet path; b. an oil inlet path is branched; c. a connecting oil path; 4. a second front oil port; 5. an oil passage plug; 51. plugging the shaft section; 52. a guide shaft section; 6. adjusting the stud; 7. a spring; m, a positioning groove; n, positioning columns; 8. a first groove; 9. a rear ring groove; 10. a sealing plug; 11. a front ring groove; 12. a second groove; 13. a first sealing structure; 14. a second sealing structure; 15. and a third sealing structure.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.

It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

The pressure self-releasing type squeeze cylinder as shown in fig. 1 to 9 is provided above a press-fit case, and includes a cylinder tube 100 having an opening at a front end, a cylinder head 200 provided at a front end of the cylinder tube 100, and a piston 300 and a piston rod 400 slidably provided in the cylinder tube 100 in an integrated structure, and a rod oil chamber 600 and a rodless oil chamber 500 are formed in the cylinder tube 100 in the piston 300;

the rear end of the cylinder barrel 100 is of a closed structure, a first rear oil port 1 communicated with a rodless oil cavity 500 is arranged on the side wall of the rear end of the cylinder barrel 100, and an oil leakage path 2 is arranged on the middle side wall of the cylinder barrel 100; a first front oil port 3 and a second front oil port 4 which are communicated with the rod oil cavity 600 are arranged on the side wall of the cylinder cover 200, and the second front oil port 4 is communicated with the oil drain path 2;

the oil drain path 2 comprises a first oil path 21 penetrating along the radial direction and a second oil path 22 penetrating towards the cylinder cover 200 perpendicular to the first oil path 21, an oil path plug 5 is arranged at the intersection of the first oil path 21 and the second oil path 22, an adjusting stud 6 is arranged in the first oil path 21, and a spring 7 is arranged between the adjusting stud 6 and the oil path plug 5; when the hydraulic oil in the rodless oil cavity 500 enters the first oil path 21, the oil pressure drives the oil path plug 5 to squeeze the spring 7, so that the hydraulic oil in the rodless oil cavity 500 enters the second front oil port 4 through the first oil path 21 and the second oil path 22, at this time, the oil pressures at two sides of the piston 300 are balanced, and the rod of the piston 300 is pushed to the oil port position of the first oil path 21 by the pressure released by the deformation of the box body.

The preferred implementation process of the invention is that after the assembly of all parts in the extrusion oil cylinder is completed, hydraulic oil enters through the first rear oil port 1 and pushes the piston rod 400 to rapidly extend, and after the piston 300 is abutted against the cylinder cover 200, the hydraulic oil is continuously introduced into the first rear oil port 1, the oil pressure in the rodless oil cavity 500 is continuously increased, when the oil pressure is increased until the oil duct plug 5 opens the oil discharge duct 2, the hydraulic oil enters into the second front oil port 4 through the oil discharge duct 2, and the first front oil port 3 is in a free oil port state, so that the oil pressure in the rod oil cavity 600 and the rodless oil cavity 500 at two sides of the piston 300 tend to be in an equilibrium state, the piston rod 400 drives the piston 300 to move back to the position of the first oil duct 21 under the action of the pushing force generated by the deformation of the box body, but the oil port of the first oil duct 21 is not blocked, and the reverse pressure generated by the deformation of the box body is released.

According to the invention, through the arrangement of the oil discharging way 2 and the second front oil port 4, the oil passage plug 5 arranged in the first oil way 21 can be opened by utilizing the oil pressure in the rodless oil cavity 500 in the state that the piston rod 400 is completely extended, so that the oil pressure balance at two sides of the piston 300 is realized, the piston 300 can freely move between the rodless oil cavity 500 and the rod-containing oil cavity 600, the pressure generated by the deformation of the box body is retracted through the piston rod 400, the self-release of the pressure of the box body is realized, the occurrence of the outward protruding phenomenon of the side wall of the box body can be effectively avoided, and the forming quality of products is improved.

After the piston 300 is abutted against the cylinder cover 200, hydraulic oil in the rodless oil cavity 500 can enter the first oil channel 21 of the oil leakage channel 2 and form axial jacking force on the oil channel plug 5, and in order to ensure that the bearing surface of the oil channel plug 5 is uniformly stressed in the axial direction, preferably, the axial distance between one side surface of the cylinder cover 200, which faces the rodless oil cavity 500, and the first oil channel 21 is greater than the thickness of the piston 300, so that the first oil channel 21 is prevented from being blocked when the piston 300 is retracted, the first oil channel 21 is effectively ensured to be fully communicated with the rodless oil cavity 500, hydraulic oil enters along the axial direction of the first oil channel 21, and the same jacking force is applied to the oil channel plug 5 along the circumferential side wall, so that the oil in the first oil channel 21 is effectively prevented from being whirled, and the sliding stability of the oil channel plug 5 in the first oil channel 21 is improved.

As shown in fig. 4, in the present invention, the piston rod 400 drives the piston 300 to retract inwards under the action of external force, in order to ensure that the oil drain path 2 is always in an open state, the oil passage plug 5 needs to have enough oil pressure to keep the open state of the oil drain path 2, preferably, a first groove 8 is provided on a side surface of the piston 300 facing the rodless oil cavity 500, and the first groove 8 is located at an outer edge of the piston 300; and the depth of the first groove 8 is smaller than or equal to the radius of the oil inlet hole of the first oil path 21, when the piston 300 is pushed and displaced by the release pressure to be close to the oil port of the first oil path 21, one end surface of the piston 300 protruding out of the first groove 8 is coplanar with the axis of the first oil path 21.

When oil is fed, a centering oil pressure is applied to the piston 300 from the side surface so as to ensure the centering of the movement of the piston 300, when the piston 300 is abutted against the end surface of the cylinder cover 200, hydraulic oil enters into a section of the first oil path 21 below the oil path plug 5, and the oil pressure in the rodless oil cavity 500 is smaller than the jacking force of the spring 7 at the moment, so that the oil path plug 5 is used for blocking the second oil path 22, the oil leakage path 2 is in a closed state, and the piston 300 is subjected to single-side oil pressure at the moment; with the gradual increase of the oil pressure in the rodless oil chamber 500, the oil passage plug 5 compresses the spring 7 upward to open the second oil passage 22, at this time, the piston 300 receives the oil pressure from both sides, and the oil pressures in the rodless oil chamber 500 and the rod-containing oil chamber 600 tend to be balanced, and after the piston 300 is retracted, the first groove 8 communicates with the rodless oil chamber 500, so that the annular cavity formed on the circumferential side wall covers the oil inlet hole of the first oil passage 21, to ensure the stability of the oil pressure entering the first oil passage 21.

In the preferred embodiment of the present invention, the inner hole of the cylinder barrel 100 is provided with a rear ring groove 9 near the first rear oil port 1, hydraulic oil enters the rear ring groove 9 through the first rear oil port 1, and oil pressure is formed on the side surface of the piston 300 to ensure the centering of the piston 300.

In the preferred embodiment of the invention, the first front oil port 3 and the second front oil port 4 both comprise a main oil inlet path a along the radial direction and a branch oil inlet path b vertically arranged at the end part of the main oil inlet path a; a sealing plug 10 is arranged at the end part of the main oil inlet path a of the second front oil port 4, which is far away from the branch oil inlet path b, a connecting oil path c is arranged on the main oil inlet path a of the second front oil port 4, the second oil path 22 is communicated with the connecting oil path c, and the branch oil inlet path b is communicated with the rod oil cavity 600.

Specifically, the main oil inlet path a and the branch oil inlet path b are in an L-shaped structure, the branch oil inlet paths b of the first front oil port 3 and the second front oil port 4 are symmetrical along the axis of the piston rod 400, the connecting oil path c is parallel to the branch oil inlet path b, and the second oil path 22 is communicated with the main oil inlet path a through the connecting oil path c, so that after the piston 300 abuts against the cylinder cover 200, the second front oil port 4 and the oil drain path 2 form oil pressure balanced return oil paths at two sides of the piston 300, and the practicability of releasing the pressure of the oil cylinder is ensured.

On the basis of the above embodiment, the end face of the cylinder cover 200 facing the piston 300 is provided with the front ring groove 11; the front ring groove 11 is communicated with two branch oil inlet paths b of the first front oil port 3 and the second front oil port 4, and when the rod oil cavity 600 is filled with oil, hydraulic oil enters the rod oil cavity 600 from the front ring groove 11 so as to apply axial force to the piston 300, and the uniformity of stress of the piston 300 is ensured.

In the invention, the contact surface of the cylinder barrel 100 and the piston 300 is provided with a second groove 12, and the second groove 12 is arranged at the center of the bottom of the cylinder barrel 100 and is coaxially arranged with the piston 300; further, it is ensured that the piston 300 is uniformly stressed, the first rear oil port 1 penetrates through the cylinder barrel 100 in the radial direction, and the first groove 8 and the second groove 12 are arranged in the projection range of the first rear oil port 1 along the axis, so that a stepped oil inlet cavity is formed between the first groove 8 and the second groove 12, and centering oil pressure is applied to the piston 300. Enabling a quick start and maintaining centered movement of the piston 300.

In the preferred embodiment of the present invention, the first oil path 21 includes a first cavity 211 and a second cavity 212 along the axial direction, the diameter of the first cavity 211 is larger than that of the second cavity 212, and a threaded structure is arranged at one end of the first cavity 211 away from the second cavity 212; the adjusting stud 6 is fixed at the end position of the first cavity 211 through a thread structure; the oil duct plug 5 is arranged at one end of the first cavity 211, which is close to the second cavity 212, and the second oil path 22 is blocked through the side surface of the oil duct plug 5, and the distance between the adjusting stud 6 and the oil duct plug 5 is larger than the length of the shaft section of the oil duct plug 5, which exceeds the second oil path 22 towards one end of the second cavity 212, so that a sufficient moving distance exists between the oil duct plug 5 and the adjusting stud 6, and the oil pressure can be ensured to smoothly jack up the oil duct plug 5.

In order to ensure the position accuracy of the spring 7, positioning grooves m for embedding the end parts of the spring 7 are formed in the opposite surfaces of the adjusting stud 6 and the oil duct plug 5; a positioning column n is arranged at the center of the positioning groove m between the adjusting stud 6 and the oil duct plug 5, and protrudes out of the upper surface of the positioning groove m; the positioning column n is riveted into the placing groove and can be used for opposite to the two ends of the spring 7, so that the phenomenon of compression deflection of the spring 7 is avoided; the outer cylindrical surface of the oil duct plug 5 is provided with a plugging shaft section 51 and a guiding shaft section 52 along the axial direction, when the oil duct plug 5 is closed, the plugging shaft section 51 is arranged corresponding to the second oil way 22, and the guiding shaft section 52 gradually contracts inwards along the direction away from the plugging shaft section 51.

When oil pressure enters the first oil path 21, hydraulic oil can be filled in an expansion joint formed by the guide shaft section 52 and the first oil path 21, so that even centering thrust is applied to the oil plug path, the stress of the oil path plug 5 is even, the stability of the movement of the oil plug path is ensured, when the oil pressure pushes the oil plug path to slide, the contact area of the oil plug path and the first oil path 21 is reduced by the guide shaft section 52, the force application area of the oil pressure to the oil plug path is increased, the oil plug path slides to the guide shaft section 52 to be close to the second oil path 22, and the hydraulic oil can quickly enter the second oil path 22 from the expansion joint, so that the oil path plug 5 can be quickly opened.

In the preferred embodiment of the invention, the contact surface of the cylinder cover 200 and the cylinder barrel 100 extends out of a boss, the boss is embedded into an oil cavity of the cylinder barrel 100, a first sealing structure 13 is arranged at the joint of the contact end surface of the cylinder cover 200 and the cylinder barrel 100 at the second oil path 22, a second sealing structure 14 is arranged on the boss, a sliding bearing and a third sealing structure 15 are arranged on the sliding contact surface of the cylinder cover 200 and the piston rod 400, the oil path tightness of the second oil path 22 and the second front oil port 4 is ensured by the arrangement of the first sealing structure 13, the sealing performance of the connection of the cylinder cover 200 and the cylinder barrel 100 is ensured by the second sealing structure 14, preferably, the first sealing structure 13 and the second sealing structure 14 both adopt the sealing form of a sealing ring, and the third sealing structure 15 adopts the sealing form of an oil seal, so that the axial sliding of the piston rod 400 is ensured, the axial leakage of hydraulic oil along the piston rod 400 is effectively avoided, and the stable oil pressure in the rod oil cavity 600 is further ensured.

It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. The pressure self-releasing type extrusion oil cylinder is arranged above the compression box body and comprises a cylinder barrel with an opening at the front end, a cylinder cover arranged at the front end of the cylinder barrel, a piston and a piston rod which are arranged in the cylinder barrel in a sliding manner and are of an integrated structure, and a rod oil cavity and a rodless oil cavity are formed in the cylinder barrel by the piston, and the pressure self-releasing type extrusion oil cylinder is characterized in that;

2. The pressure self-releasing type squeeze cylinder of claim 1, wherein an axial distance between a side of the cylinder head facing the rodless oil chamber and the first oil passage is greater than a thickness of the piston.

3. The pressure self-releasing type squeeze cylinder as claimed in claim 2, wherein a first groove is provided at a side of the piston facing the rodless oil chamber, the first groove being located at an outer edge of the piston;

4. The pressure self-releasing type extrusion cylinder as claimed in claim 1, wherein a rear ring groove is provided in a position of the inner bore of the cylinder barrel close to the first rear oil port.

5. The pressure self-releasing type squeeze cylinder of claim 1, wherein the first front oil port and the second front oil port each comprise a main oil inlet path along a radial direction and a branch oil inlet path vertically arranged at an end of the main oil inlet path;

6. The pressure self-releasing type squeeze cylinder of claim 5, wherein a front ring groove is provided at an end face of the cylinder head facing the piston;

7. The pressure self-releasing type extrusion cylinder as claimed in claim 3, wherein a second groove is formed in a contact surface of the cylinder barrel and the piston, and the second groove is formed in a center position of the bottom of the cylinder barrel and is coaxially arranged with the piston;

8. The pressure self-releasing type extrusion cylinder as claimed in claim 1, wherein the first oil path includes a first cavity and a second cavity along an axial direction, the diameter of the first cavity is larger than that of the second cavity, and a screw thread structure is provided at one end of the first cavity away from the second cavity;

9. The pressure self-releasing type extrusion cylinder as claimed in claim 1, wherein positioning grooves for embedding the spring ends are formed in opposite surfaces of the adjusting studs and the oil duct plugs;

10. The pressure self-releasing type extrusion cylinder as claimed in claim 1, wherein a boss is extended from a contact surface of the cylinder cover and the cylinder tube, and the boss is embedded into an oil cavity of the cylinder tube;