CN211715887U

CN211715887U - Gear and rack type pneumatic actuator

Info

Publication number: CN211715887U
Application number: CN202020094189.6U
Authority: CN
Inventors: 丁毅
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-01-16
Filing date: 2020-01-16
Publication date: 2020-10-20
Anticipated expiration: 2030-01-16

Abstract

The utility model discloses a rack formula pneumatic actuator belongs to the pneumatic actuator field. Two piston semi-rings are fixed in a piston gap, the sections of the piston semi-rings are inclined planes, a piston sealing ring is installed in a gap groove between the two piston semi-rings, and the piston sealing ring winds from one side of one piston semi-ring to the other side of the other piston semi-ring through a section gap; based on the same idea, a piston seal ring groove is formed in one end of the piston around the circumference of the piston, the piston seal ring groove is in a Z shape similar to transverse stretching, two straight line portions are parallel to the end face of the piston, an oblique line portion and the straight line portions form an obtuse angle and are in arc transitional connection, the Z-shaped groove is formed in the half circumference of the cylindrical surface of the piston, an inverted Z-shaped groove is formed in the other half circumference, the two Z-shaped grooves are symmetrical relative to the symmetrical plane of the rack, a complete closed seal ring groove is formed in the circumference of the piston, and the piston seal ring is fixedly installed in the piston seal ring groove. The device has the advantages of long service life of the actuator, low maintenance frequency and simple, convenient and quick maintenance.

Description

Gear and rack type pneumatic actuator

Technical Field

The utility model relates to a pneumatic actuator technical field specifically is rack and pinion formula pneumatic actuator.

Background

The pneumatic actuator is an actuating device for opening and closing a valve, is widely used in the industrial fields of petrochemical industry, metallurgy and the like, and is mostly used in remote control. The actuating mechanism of the existing pneumatic actuator mainly comprises a piston type, a shifting fork type, a diaphragm type and a rack and pinion type, wherein the rack and pinion type pneumatic actuating mechanism has the advantages of simple structure, small volume and attractive appearance, so that the application is very wide. Rack and pinion pneumatic actuators are particularly common with integrated cylinders, but they are also deficient: the gear rack tooth row indexing plane is a stress central plane, deviates from a gas pressure central line of the piston by a gear indexing circular radius, generates very large torque to the piston in work, and needs to limit the piston ring and the gear rack bearing pad through the cylinder wall to counteract the torque of the gas pressure to the piston, so that the cylinder wall, the piston ring and the gear rack bearing pad are quickly abraded, and the service life is shortened. And when the double-acting type gear rack pneumatic actuator is designed, the diameter of a gear shaft cannot be designed to be larger, namely, the torque cannot be made larger under the condition of the same cylinder diameter. The same drawback exists with single-acting rack-and-pinion pneumatic actuators in which the direction of the return force of the spring also acts on the piston centerline.

SUMMERY OF THE UTILITY MODEL

For solving the deficiencies existing in the prior art, the utility model provides a rack and pinion formula pneumatic actuator.

The technical scheme of the utility model is that:

the utility model provides a rack and pinion formula pneumatic actuator in a first aspect, including cylinder block, left piston, right piston, left rack, right rack, gear shaft, piston seal ring and the left and right end lid of fixed mounting at cylinder block both ends; the left piston and the right piston are respectively arranged on the left side and the right side in the cylinder body; the left piston and the right piston are connected with a gear shaft through a left rack and a right rack which are respectively arranged on the left piston and the right piston; the gear shaft penetrates through the inner center of the cylinder block up and down; the piston sealing ring is characterized in that two piston semi-rings are respectively fixed on the left piston and the right piston in a clearance mode, the sections of the piston semi-rings are inclined planes, a piston sealing ring is installed in a clearance groove between the two piston semi-rings, and the piston sealing ring winds the other side of the other piston semi-ring from one side of one piston semi-ring through the section clearance.

Preferably, each of the piston half rings is fixed to the piston by a screw.

The utility model provides a rack and pinion pneumatic actuator in a second aspect, which comprises a cylinder body, a left piston, a right piston, a left rack, a right rack, a gear shaft, a piston seal ring, and a left end cover and a right end cover which are fixedly arranged at two ends of the cylinder body; the left piston and the right piston are respectively arranged on the left side and the right side in the cylinder body; the left piston and the right piston are connected with a gear shaft through a left rack and a right rack which are respectively arranged on the left piston and the right piston; the gear shaft penetrates through the inner center of the cylinder block up and down; piston sealing ring grooves are formed in one ends of the left piston and the right piston around the circumference of the pistons; the groove shape of the piston sealing ring is Z-shaped like transverse stretching, two straight line parts are parallel to the end surface of the piston, an obtuse angle is formed between the oblique line part and the straight line parts, the oblique line parts and the straight line parts are in arc transition connection, the Z-shaped groove is formed in the half circumference of the cylindrical surface of the piston, an inverted Z-shaped groove is formed in the other half circumference, the two Z-shaped grooves are symmetrical relative to the symmetrical plane of the rack, and a complete closed sealing ring groove is formed in the circumference of the piston; the piston sealing ring is fixedly arranged in the piston sealing ring groove.

The rack and pinion pneumatic actuator according to the first or second aspect, further comprising a spring independent body; the spring independent body consists of a shell, a spring group and a spring ejector rod; one end of the spring group is fixed at one end in the shell, and the other end of the spring group is fixedly connected with one end of the spring ejector rod; the other end of the spring ejector rod penetrates out of the other end in the shell; the outer sides of the left end cover and the right end cover are fixedly connected with spring independent bodies; the left end cover and the right end cover are both provided with through holes for the spring ejector rod to move; the head of the spring ejector rod is embedded into the outer end faces of the left piston and the right piston through holes formed in the left end cover and the right end cover respectively, and the stress centers of the independent left spring body and the independent right spring body are superposed with the centers of the indexing planes of the left rack tooth row and the right rack tooth row respectively.

Preferably, the through holes are matched with the sealing plugs.

Preferably, the outer sides of the left end cover and the right end cover are both in threaded connection with the independent bodies of the springs.

The utility model has the advantages that: the utility model discloses a drive the design of dislocation sealing washer groove and the spring independence on rack and pinion formula pneumatic actuator piston semi-ring, the piston and can eliminate most piston ring to the pressure of cylinder wall, the wearing and tearing of the piston ring that has significantly reduced have also reduced the wearing and tearing of piston seal circle, rack cushion and cylinder, increase the life of executor, reduce maintenance frequency. The pressure of a piston ring and a rack bearing pad on the cylinder wall can be eliminated by changing the dislocation size of a piston sealing ring, so that the diameter of a gear shaft can be increased to increase the torque of the actuator, and the large-torque pneumatic actuator is realized; furthermore, the spring independent body can also realize quick conversion between the single-acting and double-acting gear and rack type pneumatic actuators, the practicability is enhanced, and the installation, the replacement and the maintenance are simple.

Drawings

FIG. 1 is a front cross-sectional view of an embodiment of a double-acting pneumatic actuator with piston half rings in a 0 operating position;

FIG. 2 is a top cross-sectional view of an embodiment of a double-acting pneumatic actuator with piston half rings in a 0 operating position;

FIG. 3 is a top cross-sectional view of an embodiment two piston slotted dual action pneumatic actuator operating at a 0 position;

FIG. 4 is a schematic diagram of a right piston rack assembly with an offset piston seal ring groove according to a second embodiment;

FIG. 5 is a schematic diagram of the structure and stress condition of a piston in a conventional rack and pinion pneumatic actuator;

FIG. 6 is an installation pattern of piston half rings and pistons of an embodiment of a pneumatic actuator;

FIG. 7 is a top cross-sectional view of an embodiment of a dual-action pneumatic actuator having piston half rings in a 90 operating position;

FIG. 8 is a schematic diagram of an embodiment of a spring in an isolated configuration;

FIG. 9 is a top cross-sectional view of a third embodiment of a single-acting rack and pinion pneumatic actuator having piston half rings;

FIG. 10 is a top cross-sectional view of a 0 position of a third embodiment single-acting rack and pinion pneumatic actuator with misaligned piston seal ring slots;

wherein, 1-cylinder block; 2-left end cap; 3-right end cover; 4-left piston; 5-right piston; 6-left rack; 7-right rack; 8, a piston semi-ring; 9-piston semi-ring screw; 10-piston seal ring; 11-rack bearing pad; 12-middle chamber vent; 13-two end cavity vent holes; 14-gear shaft; 15-end cover fixing screws; 16-a spring ejector rod; 17-a left end cover provided with a through hole; 18-a right end cover provided with a through hole; 19-left spring independent body; 20-right spring independent body; 21-piston ring 22-piston seal ring groove; 23-a housing; 24-a spring set; 25-through hole.

Detailed Description

The following detailed description will be given to specific embodiments of the present invention with reference to the accompanying drawings 1 to 10.

The first implementation mode comprises the following steps:

the gear rack type pneumatic actuator provided by the first aspect of the present invention, as shown in fig. 1 and 2, includes a cylinder block 1, a left piston 4, a right piston 5, a left rack 6, a right rack 7, a rack bearing pad 11, a gear shaft 14, a piston semi-ring 8, a piston seal ring 10, and a left end cap 2 and a right end cap 3 fixedly installed at two ends of the cylinder block; the left piston 4 and the right piston 5 are respectively arranged on the left side and the right side in the cylinder body 1; the left piston 4 and the right piston 5 are linked with a gear shaft 14 through a left rack 6 and a right rack 7 which are respectively arranged on the left piston and the right piston; the left side of the left rack 6 is integrated with the left piston 4, and the right side of the right rack 7 is integrated with the right piston 5; rack bearing pads 11 are arranged on the back of the right side of the left rack 6 and the back of the left side of the right rack 7; the gear shaft 14 penetrates through the inner center of the cylinder block 1 up and down; piston semi-rings 8 are respectively fixed on the left piston 4 and the right piston 5 in a clearance mode, the sections of the piston semi-rings 8 are inclined planes, piston sealing rings 10 are installed in clearance grooves between the two piston semi-rings 8, and the piston sealing rings 10 are wound to the other side of the other piston semi-ring 8 from one side of one piston semi-ring 8 through the clearance of the sections.

The second embodiment:

based on the same idea of the rack and pinion pneumatic actuator provided by the first aspect, the rack and pinion pneumatic actuator provided by the second aspect of the present invention, as shown in fig. 3, comprises a cylinder block 1, a left piston 4, a right piston 5, a left rack 6, a right rack 7, a rack bearing pad 11, a gear shaft 14, a piston seal ring 10, a piston ring 21, a piston seal ring groove 22, and a left end cap 2 and a right end cap 3 fixedly mounted at two ends of the cylinder block; the left piston 4 and the right piston 5 are respectively arranged on the left side and the right side in the cylinder body 1; the left piston 4 and the right piston 5 are linked with a gear shaft 14 through a left rack 6 and a right rack 7 which are respectively arranged on the left piston and the right piston; the left side of the left rack 6 is integrated with the left piston 4, and the right side of the right rack 7 is integrated with the right piston 5; rack bearing pads 11 are arranged on the back of the right side of the left rack 6 and the back of the left side of the right rack 7; the gear shaft 14 penetrates through the inner center of the cylinder block 1 up and down; as shown in fig. 4, piston seal ring grooves are respectively formed at one ends of the left piston 4 and the right piston 5 around the circumference of the pistons; the groove shape of the piston sealing ring is Z-shaped like transverse stretching, two straight line parts are parallel to the end surface of the piston, an obtuse angle is formed between the oblique line part and the straight line parts, the oblique line parts and the straight line parts are in arc transition connection, the Z-shaped groove is formed in the half circumference of the cylindrical surface of the piston, an inverted Z-shaped groove is formed in the other half circumference, the two Z-shaped grooves are symmetrical relative to the symmetrical plane of the rack, and a complete closed sealing ring groove is formed in the circumference of the piston; the piston sealing ring is fixedly arranged in the piston sealing ring groove.

In the rack and pinion pneumatic actuator of the first and second embodiments, the middle chamber vent hole 12 and the two end chamber vent holes 13 are formed in the upper portion of one side of the cylinder block 1, when air source pressure enters the two end air chambers of the actuator from the two end chamber vent holes 13, the left piston 4 and the right piston 5 move towards the middle direction of the cylinder block 1, air in the middle air chamber is discharged through the middle chamber vent hole 12, and the left piston rack and the right piston rack synchronous gear shaft 14 rotate anticlockwise. When air source pressure enters a middle air cavity of the actuator from a middle cavity vent hole 12, the left piston 4 and the right piston 5 respectively move towards the two ends of the cylinder body 1, air in the air cavities at the two ends is discharged through a two-end cavity vent hole 13, and meanwhile, the left piston rack synchronous gear shaft 14 and the right piston rack synchronous gear shaft rotate clockwise.

In the prior art, as shown in fig. 5, when the piston is subjected to a force F1 from one side, F1 passes through the center of the piston, and the resultant force point of the rack is at an engagement point P, since the two forces deviate from a reference circle radius, the piston rotates around the fulcrum P under the action of F1, so that the upper half of the circumference of the piston is pressed against the cylinder wall, and similarly, when the piston is subjected to a force from the other side, the lower half of the circumference of the piston is pressed against the cylinder wall, which is very large, so that the piston ring 21 is easily worn, and the piston seal ring 10 and the cylinder wall are also easily worn.

To solve the above problems, the first and second embodiments can reduce the lateral force of the piston circumference against the cylinder wall to a small value. In the first embodiment, the piston ring 21 is changed into two piston half rings 8 by changing the structure of the piston ring 21, the two piston half rings 8 are fixed on the left piston 4 and the right piston 5 respectively in a clearance manner, the cross sections of the piston half rings 8 are inclined surfaces, and each piston half ring 8 is fixed on the piston through a piston half ring screw 9. The symmetry plane of the two piston half rings 8 is coincident with the symmetry plane of the rack, and the installation direction is shown in fig. 6. Piston sealing rings 10 are embedded into clearance grooves of the two installed piston half rings 8, the piston sealing rings 10 are wound to the other side of the other piston half ring 8 from one side of one piston half ring 8 through a section clearance, the piston sealing rings 10 are fixed in a staggered distribution mode through the structure of the two piston half rings 8, one piston half ring 8 divides one half of the piston sealing ring 10 to one side, close to a gear shaft 14, of the piston, and the other piston half ring 8 divides the other half of the piston sealing ring 10 to one side, close to an end cover, of the piston. When the piston is acted by force from any end face direction, a corresponding acting force always acts on one side of the cylindrical surface of the piston, so that a torque is generated on the piston, which is just opposite to the torque generated by the previous acting force acting on the center of the end face of the piston, and the acting force of the piston semi-ring 8 and the rack bearing pad 11 on the cylinder wall is almost eliminated. Taking the right piston 5 in the double-acting rack-and-pinion pneumatic actuator shown in fig. 7 as an example to illustrate a specific implementation process, when air pressure enters the intermediate air cavity of the actuator from the intermediate air cavity vent 12, the right piston 5 is subjected to rightward air pressure F1, the force center is on the center of the right piston 5, the right piston 5 drives the right rack 7 to move rightward, the right rack 7 then drives the gear shaft 14 to rotate, the meshing point is at point P, the right piston 5 rotates counterclockwise around point P under the action of F1, because the piston seal rings 10 are arranged on the piston circumference in a staggered manner, the air pressure is distributed unevenly on the piston circumference, resulting force F2 is generated, the piston is rotated clockwise around point P by F2, and thus the deflection effect of the piston on the piston by F1 is counteracted. Similarly, in the following, taking the right piston 5 in the double-acting rack-and-pinion pneumatic actuator shown in fig. 2 as an example to explain the specific implementation process, when the air pressure enters the two end air chambers of the actuator from the two end chamber vents 13, the air pressure F1 and the resultant force F2 received by the right piston 5 are opposite to the situation in fig. 2, the right piston 5 rotates clockwise around the point P under the action of F1, and the piston rotates counterclockwise around the point P under the action of the resultant force F2, so that the two yawing moments are cancelled out. In the two working states shown in fig. 2 and fig. 7, the distance from F2 to point P is a variable, so the generated moment is also a variable, as long as the design is reasonable, most of the pressure of the piston ring on the cylinder wall can be eliminated, and because the design width of the piston half ring 8 is increased, the abrasion of the piston half ring 8 is greatly reduced, the abrasion of the piston sealing ring 10, the rack bearing pad 11 and the cylinder body 1 is also reduced, the service life of the actuator is prolonged, and the maintenance frequency is reduced. In addition, current pneumatic actuator, its piston is because it is big by deflection moment, and it is too big to lead to 14 diameters of gear shaft to do, and the utility model provides a technical scheme can eliminate the pressure of piston semi-ring 8 and rack cushion 11 to the cylinder wall through the dislocation size that changes piston seal ring 10, so can increase the moment of torsion that 14 diameters of gear shaft increased the executor, realize big moment of torsion pneumatic actuator.

Based on the same thinking of the first piston semi-ring of the embodiment, the technical scheme that the second piston is provided with the dislocation grooves can be adopted to solve the same technical problem, the dislocation grooves are respectively machined on the circumferences of the left piston and the right piston, and then the piston sealing ring is installed in the piston sealing ring groove, so that the dislocation of the piston sealing ring is realized. As shown in fig. 4, the piston seal groove divides the piston seal 10 into a half on the side of the piston closer to the pinion shaft 14 and a half on the side of the piston seal 10 closer to the piston ring 21. When the piston is acted by force from any end face direction, a corresponding acting force always acts on one side of the cylindrical surface of the piston, so that a torque is generated on the piston, which is just opposite to the torque generated by the previous acting force acting on the center of the end face of the piston, and the acting force of the piston and the rack bearing pad 11 on the cylinder wall is almost eliminated.

The third embodiment is as follows:

based on the same idea of the rack and pinion pneumatic actuator provided by the first aspect of the present invention and the rack and pinion pneumatic actuator provided by the second aspect of the present invention, the rack and pinion pneumatic actuator provided by the first aspect and the rack and pinion pneumatic actuator provided by the second aspect of the present invention further include a spring independent body as shown in fig. 8; the spring independent body consists of a shell 23, a spring group 24 and a spring ejector rod 16; one end of the spring group 24 is fixed at one end in the shell 23, and the other end of the spring group 24 is fixedly connected with one end of the spring ejector rod 16; the other end of the spring ejector rod 16 penetrates out of the other end in the shell 23; as shown in fig. 9 and 10, spring independent bodies, i.e., a left spring independent body 19 and a right spring independent body 20, are fixedly connected to the outer sides of the left end cap 2 and the right end cap 3 of the rack and pinion pneumatic actuator according to the first and second embodiments; the left end cover 2 and the right end cover 3 are both provided with through holes 25 for the spring ejector rods 16 to move; the head parts of the spring ejector rods 16 of the left spring independent body 19 and the right spring independent body 20 are respectively embedded into the outer end surfaces of the left piston 4 and the right piston 5 through holes 25 formed in the left end cover 2 and the right end cover 3, and the stress centers of the left spring independent body 19 and the right spring independent body 20 are respectively superposed with the center of the indexing plane of the left rack tooth row and the right rack tooth row. More preferably, a seal plug may be disposed in the through hole 25 formed in both the left end cap 2 and the right end cap 3. Further preferably, the outer sides of the left end cover 2 and the right end cover 3 are both independent bodies connected with springs through threads.

The piston in the double-acting rack and pinion type pneumatic actuator is acted by air pressure in a two-way mode to ensure that the piston disappears after being counteracted by deflection torque, however, the reality is that the first action of opening or closing some valves needs to be driven by air pressure, the second return action is completed by a spring device in the pneumatic actuator, namely, some valves need to be opened and closed by a single-acting rack and pinion type pneumatic actuator, the existing single-acting rack and pinion type pneumatic actuator is based on the double-acting rack and pinion type pneumatic actuator, a group of springs are added between each piston and an end cover, and the elastic force center of the spring group is still on the piston center and still has deflection force on the piston. To this technical defect, the utility model discloses do further improvement to rack and pinion formula pneumatic actuator, separate out spring assembly from the cylinder block, design into as the independent body of spring as shown in fig. 8, spring assembly 24 installs in independent casing 23, and the required restoring force of reply action is implemented through the spring ejector pin 16 that stretches out in the independent body. The stress centers of the left spring independent body 19 and the right spring independent body 20 are respectively superposed with the centers of the indexing planes of the left rack tooth row and the right rack tooth row, so that the spring independent bodies are in an offset design relative to the center of the piston, and the design eliminates the deflection moment to the piston. The single-acting gear and rack type pneumatic actuator works in two working processes: one is a pneumatic working process and the other is a spring return process. When air source pressure enters a middle air cavity of the actuator from a middle cavity vent hole 12, starting an air pressure working process, enabling the left piston 4 and the right piston 5 to move towards the two ends of the cylinder body 1 respectively by the air pressure, forcing the spring groups 24 in the independent bodies at the left end and the right end to compress, discharging air in the air cavities at the two ends through the two end cavity vent holes 13, and enabling the left piston rack synchronous gear shaft 14 and the right piston rack synchronous gear shaft to rotate clockwise; after the air source pressure is reversed, the spring recovery process is started, the two pistons move towards the middle direction under the action of the elastic force of the spring, the air in the middle air cavity is discharged from the middle cavity vent hole 12, and meanwhile, the left piston rack and the right piston rack synchronous gear shaft 14 rotate in the anticlockwise direction. Taking the right piston 5 shown in fig. 9 as an example to explain the specific working process, when the air source pressure enters the middle air cavity of the actuator from the middle air cavity vent 12, because P is the meshing point and is on the rack tooth row graduation plane, the elastic force of the right spring independent body 20 does not act on the rotation of the right piston 5 around the point P, and the direction of the air pressure F1 is coincident with the central line of the right piston 5, so that the right piston 5 rotates anticlockwise around the point P, the lateral pressure resultant force F2 is vertically downward on the upper side of the right piston 5, so that the right piston 5 rotates clockwise around the point P, and the two acting forces are offset, thereby the forced rotation condition of the right piston 5 is the same as that of the double-acting rack and pinion pneumatic actuator; in the spring return process, the return force of the spring group in the independent body also passes through the point P, the piston has no deflection moment, and the abrasion to the piston, the rack assembly and the cylinder is still eliminated. When the rack-and-pinion pneumatic actuator of the utility model is implemented on a single-acting rack-and-pinion pneumatic actuator, a sealing plug can be arranged for the through hole 25; only need to screw down the spring independent body, all install sealed stifled for the thru hole 25 of left and

right end cover

2, 3, can convert the two effect rack and pinion formula pneumatic actuator into fast, further, in order to accelerate conversion rate, can also be respectively through threaded connection left spring independent body 19 and right spring independent body 20 in the outside of left end cover 2 and right end cover 3, can realize convenient and fast ground screw down the spring independent body. Therefore, the spring independent body of the embodiment has the advantage of eliminating the deflection moment of the piston, can be quickly converted into the double-acting gear-rack type pneumatic actuator, and is high in practicability, and simple and quick to install, replace and maintain.

The above-mentioned embodiment is only to describe the preferred embodiment of the pneumatic actuator of the present invention, and not to limit the concept and scope of the present invention, without departing from the present invention, the skilled person in the art will be right the various shape modifications and improvements made by the technical solution of the present invention all fall into the protection scope of the pneumatic actuator of the present invention.

Claims

1. A rack and pinion type pneumatic actuator comprises an air cylinder body, a left piston, a right piston, a left rack, a right rack, a gear shaft, a piston sealing ring, a left end cover and a right end cover, wherein the left end cover and the right end cover are fixedly arranged at two ends of the air cylinder body; the left piston and the right piston are respectively arranged on the left side and the right side in the cylinder body; the left piston and the right piston are connected with a gear shaft through a left rack and a right rack which are respectively arranged on the left piston and the right piston; the gear shaft penetrates through the inner center of the cylinder block up and down; the method is characterized in that: the piston sealing ring is characterized in that two piston semi-rings are respectively fixed on the left piston and the right piston in a clearance mode, the sections of the piston semi-rings are inclined planes, a piston sealing ring is installed in a clearance groove between the two piston semi-rings, and the piston sealing ring winds the other side of the other piston semi-ring from one side of one piston semi-ring through the section clearance.

2. The rack and pinion pneumatic actuator according to claim 1, wherein: each piston semi-ring is fixed on the piston through a screw.

3. A rack and pinion type pneumatic actuator comprises a cylinder body, a left piston, a right piston, a left rack, a right rack, a gear shaft, a piston ring, a piston seal ring, a left end cover and a right end cover, wherein the left end cover and the right end cover are fixedly arranged at two ends of the cylinder body; the left piston and the right piston are respectively arranged on the left side and the right side in the cylinder body; the left piston and the right piston are connected with a gear shaft through a left rack and a right rack which are respectively arranged on the left piston and the right piston; the gear shaft penetrates through the inner center of the cylinder block up and down; the method is characterized in that: piston sealing ring grooves are respectively formed in one ends of the left piston and the right piston around the circumference of the pistons; the groove shape of the piston sealing ring is Z-shaped like transverse stretching, two straight line parts are parallel to the end surface of the piston, an obtuse angle is formed between the oblique line part and the straight line parts, the oblique line parts and the straight line parts are in arc transition connection, the Z-shaped groove is formed in the half circumference of the cylindrical surface of the piston, an inverted Z-shaped groove is formed in the other half circumference, the two Z-shaped grooves are symmetrical relative to the symmetrical plane of the rack, and a complete closed sealing ring groove is formed in the circumference of the piston; the piston sealing ring is fixedly arranged in the piston sealing ring groove.

4. The rack and pinion pneumatic actuator of claim 1 or 3, wherein: the spring independent body is also included; the spring independent body consists of a shell, a spring group and a spring ejector rod; one end of the spring group is fixed at one end in the shell, and the other end of the spring group is fixedly connected with one end of the spring ejector rod; the other end of the spring ejector rod penetrates out of the other end in the shell; the outer sides of the left end cover and the right end cover are fixedly connected with spring independent bodies; the left end cover and the right end cover are both provided with through holes for the spring ejector rod to move; the head of the spring ejector rod is embedded into the outer end faces of the left piston and the right piston through holes formed in the left end cover and the right end cover respectively, and the stress centers of the independent left spring body and the independent right spring body are superposed with the centers of the indexing planes of the left rack tooth row and the right rack tooth row respectively.

5. The rack and pinion pneumatic actuator according to claim 4, wherein: the through hole is matched with the sealing plug.

6. The rack and pinion pneumatic actuator according to claim 4, wherein: and the outer sides of the left end cover and the right end cover are both in threaded connection with a spring independent body.