Extra long stroke rack and pinion pneumatic actuator

Abstract

The present invention relates to an ultra-long stroke rack and pinion pneumatic actuator, which belongs to the technical field of actuators. It includes a cylinder body, a drive shaft and a rack piston; the cylinder body is cooperatively connected with the drive shaft, and the drive shaft is meshed with the rack piston; it is characterized in that: the cylinder body includes a left cylinder body, a middle cylinder body and a right cylinder body; the left cylinder body, the middle cylinder body and the right cylinder body are interconnected and combined into a cylinder body; the drive shaft and the rack piston are both located in the middle cylinder body. The ultra-long stroke rack and pinion pneumatic actuator provided by the present invention avoids the dilemma of a single cylinder body being too long while ensuring the movement stroke of the rack piston; at the same time, the design of the middle cylinder body avoids the loss of the rack piston guide ring and the sealing ring of the clamp due to the back and forth movement of the rack piston guide ring and the sealing ring at the joint.

Description

Technical Field

[0001] The invention relates to a gear rack pneumatic actuator with an ultra-long stroke, belonging to the technical field of actuators. Background Art

[0002] Pneumatic actuators are actuators that use air pressure to open, close or adjust valves. They are also called pneumatic actuators or pneumatic devices, but they are generally called pneumatic heads. Pneumatic actuators are sometimes equipped with certain auxiliary devices. Commonly used are valve positioners and handwheel mechanisms. The function of the valve positioner is to use the feedback principle to improve the performance of the actuator so that the actuator can achieve accurate positioning according to the control signal of the controller. The function of the handwheel mechanism is to use it to directly manipulate the control valve to maintain normal production when the control system fails due to power outages, gas outages, no output of the controller or failure of the actuator.

[0003] The pneumatic actuator pushes the piston toward the two ends of the cylinder body through the air source pressure in the air chamber. The rack of the piston meshes with the gear of the drive shaft, and the drive shaft starts to rotate. If the drive shaft needs to rotate in the opposite direction, the air source pressure in the other air chamber pushes the piston toward the middle of the cylinder body. The rack of the piston meshes with the gear of the drive shaft, and the drive shaft starts to rotate.

[0004] In actual use, in addition to the standard usage of 90-degree rotation stroke angle of the drive shaft, the gear rack pneumatic actuator also requires a larger rotation stroke angle of the drive shaft due to the diversity of valves, such as 120 degrees, 135 degrees, 180 degrees, 270 degrees, 360 degrees and other unconventional angles. The working principle of the gear rack pneumatic actuator is that the gear of the drive shaft meshes with the rack of the rack piston, the rack piston moves linearly in the bore of the cylinder body, and the gear drive shaft meshing with the rack rotates along the center axis of the cylinder body.

[0005] For a gear rack pneumatic actuator with a larger rotation angle, both the rack length of the rack piston itself and the linear motion stroke of the rack piston are longer than those of a gear rack pneumatic actuator with a rotation angle of 90 degrees. Therefore, as a carrier of the rack piston movement, the cylinder body also needs to be of sufficient length to ensure the linear motion stroke of the rack piston. A longer cylinder body length means greater processing difficulty for a cylinder body whose inner hole needs to be finely machined. When machining the inner hole of the cylinder body, a longer cylinder body length results in a longer machining stroke for the inner hole boring tool, which can only increase the tool handle length of the boring tool accordingly. A longer handle length means that as the boring stroke continues to increase, the boring tool head will continue to jump in the circumferential direction due to the influence of the long lever arm, which is commonly known as "the tool is thrown off" by technicians in the field, so it is impossible to ensure a better roundness and cylindricity of the cylinder body inner hole. The loss of control of these two geometric tolerances means that the rack piston will have greater losses when making linear motion in the inner hole of the cylinder body, resulting in the smoothness of the rack piston movement, and further resulting in a reduction in the torque output of the drive shaft. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide an ultra-long-stroke rack and pinion pneumatic actuator, which can provide an ultra-long-stroke cylinder structure, while ensuring the rack piston movement stroke, avoiding the problem of a single cylinder being too long.

[0007] The technical solution of the present invention is an ultra-long stroke rack and pinion pneumatic actuator, comprising a cylinder body, a drive shaft and a rack piston; the cylinder body is cooperatively connected with the drive shaft, and the drive shaft is meshed with the rack piston; its characteristics are: the cylinder body comprises a left cylinder body, a middle cylinder body and a right cylinder body; the left cylinder body, the middle cylinder body and the right cylinder body are interconnected and combined into a cylinder body; the drive shaft and the rack piston are both located in the middle cylinder body.

[0008] Furthermore, each of the left cylinder body, the middle cylinder body and the right cylinder body is provided with a cylinder inner hole; the cylinder inner hole runs through the entire cylinder body; and the cylinder inner holes on the three combined cylinder bodies are of the same size and at the same position.

[0009] Furthermore, the left cylinder body is provided with a first positioning countersunk hole, a first connecting through hole and a first positioning pin hole; a first positioning countersunk hole is provided on the edge of one end of the inner hole of the cylinder body located on the left cylinder body; and a plurality of first connecting through holes and first positioning pin holes are provided on the end surface on one side where the left cylinder body is connected to the middle cylinder body.

[0010] Furthermore, the intermediate cylinder body is provided with a positioning step, a vent hole, a connecting sealing ring groove, a connecting threaded hole and a positioning pin matching hole; the edges at both ends of the cylinder body inner hole located on the intermediate cylinder body are provided with positioning steps; the positioning step is also provided with a connecting sealing ring groove, and vent holes, connecting threaded holes and positioning pin matching holes are provided on both side end faces of the intermediate cylinder body.

[0011] Furthermore, the right cylinder body is provided with a second positioning countersunk hole, a second connecting through hole and a second positioning pin hole; a second positioning countersunk hole is provided on the edge of one end of the inner hole of the cylinder body located on the right cylinder body; and a plurality of second connecting through holes and second positioning pin holes are provided on the end surface on one side where the right cylinder body is connected to the middle cylinder body.

[0012] Furthermore, the left cylinder body is provided with a first positioning countersunk hole, the middle cylinder body is provided with a positioning step, and the right cylinder body is provided with a second positioning countersunk hole; the left cylinder body and the middle cylinder body are connected by the first positioning countersunk hole and the positioning step; the right cylinder body and the middle cylinder body are connected by the second positioning countersunk hole and the positioning step.

[0013] Further, the left cylinder body is provided with a first connecting through hole and a first positioning pin hole; the middle cylinder body is provided with a connecting threaded hole and a positioning pin matching hole; the right cylinder body is provided with a second connecting through hole and a second positioning pin hole;

[0014] The left cylinder body and the middle cylinder body are fixed by the first connecting through hole and the connecting threaded hole, the first positioning pin hole and the positioning pin matching hole; the middle cylinder body and the right cylinder body are fixed by the connecting threaded hole and the second connecting through hole, the positioning pin matching hole and the second positioning pin hole.

[0015] Furthermore, it also includes a connecting sealing ring; the connecting sealing ring is arranged in a connecting sealing ring groove; the edge of the vent hole is also provided with a vent hole sealing ring groove, and a corresponding sealing ring is arranged in the groove.

[0016] Beneficial effects of the present invention: The ultra-long-stroke rack and pinion pneumatic actuator provided by the present invention avoids the problem of a single cylinder body being too long while ensuring the movement stroke of the rack piston; at the same time, the design of the intermediate cylinder body avoids the wear of the rack piston guide ring and the sealing ring of the clamp due to the back-and-forth movement of the rack piston guide ring and the sealing ring at the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a sectional view of the three-dimensional structure of the present invention.

[0018] Figure 2 It is a schematic diagram of the left cylinder structure.

[0019] Figure 3 It is the right view of the left cylinder block.

[0020] Figure 4 It is the front view of the middle cylinder structure.

[0021] Figure 5 It is a side view of the intermediate cylinder structure.

[0022] Figure 6 It is a schematic diagram of the right cylinder structure.

[0023] Figure 7 It is the left view of the right cylinder structure.

[0024] Explanation of the accompanying drawings: 1. cylinder body; 11. left cylinder body; 111. first positioning countersunk hole; 112. first connecting through hole; 113. first positioning pin hole; 12. middle cylinder body; 121. positioning step; 122. vent hole; 123. connecting sealing ring groove; 124. connecting threaded hole; 125. positioning pin matching hole; 13. right cylinder body; 131. second positioning countersunk hole; 132. second connecting through hole; 133. second positioning pin hole; 14. cylinder body inner hole; 2. drive shaft; 3. rack piston. DETAILED DESCRIPTION

[0025] In the actual application of the rack and pinion pneumatic actuator, in addition to the standard usage of the drive shaft rotation stroke angle of 90 degrees, due to the diversity of the valves, the required rack and pinion pneumatic actuator drive shaft needs a larger rotation stroke angle, such as 120 degrees, 135 degrees, 180 degrees, 270 degrees, 360 degrees and other unconventional angles. Because of the meshing characteristics of the gear of the drive shaft and the rack of the rack piston, the gear and the rack use the same tooth module. Here is a simple formula for calculating the linear motion distance of the rack piston: L = π*m*Z*θ / 360. Among them, L represents the linear distance of the rack piston required to move, π is pi, m is the tooth module of the drive shaft gear, Z is the number of gear teeth of the drive shaft, and θ is the angle that the drive shaft needs to rotate. The larger the rotation angle θ of the drive shaft, the larger the linear motion stroke L of the corresponding rack piston, and the more teeth on the rack that mesh with the drive shaft gear are required, that is, the longer the rack piston tooth plate needs to be.

[0026] For a gear rack pneumatic actuator with a larger rotation angle, both the rack length of the rack piston itself and the linear motion stroke of the rack piston are longer than those of a gear rack pneumatic actuator with a rotation angle of 90 degrees. Therefore, as the carrier of the rack piston movement, the cylinder body also needs to be long enough to ensure the linear motion stroke of the rack piston. A longer cylinder body length means greater processing difficulty for cylinder bodies whose inner holes need to be finely processed.

[0027] From the perspective of processing technology, the inner hole of the cylinder body needs to control two geometric tolerances to ensure low loss and smoothness of the rack piston during movement. One is the roundness of the inner hole of the cylinder body, and the other is the cylindricity of the inner hole of the cylinder body.

[0028] Taking a cylinder with a cylinder bore diameter of 210mm as an example, the length of the cylinder with a drive shaft rotation angle of 90 degrees is 361mm. Under the existing processing conditions, the shape and position tolerance of the cylinder bore roundness of 0.05mm and the shape and position tolerance of the cylinder bore cylindricity of 0.05mm can be guaranteed; however, the length of the cylinder with a drive shaft rotation angle of 180 degrees is 614mm, which is about 1.7 times the original cylinder length. Under the existing processing conditions, only the cylinder bore roundness of 0.15mm can be guaranteed. m, and the shape and position tolerance of the cylinder bore cylindricity is 0.20mm. This is because when machining the cylinder bore, the longer cylinder length causes the inner bore boring cutter to require a longer machining stroke, and the corresponding only way is to increase the boring cutter handle length. The longer handle length means that as the boring stroke continues to increase, the boring cutter head will continue to increase its circumferential runout due to the influence of the long lever arm, which is what we commonly call "the cutter is thrown off", so it is impossible to guarantee a better cylinder bore roundness and cylindricity. The loss of control of these two shape and position tolerances means that the rack piston will have greater losses when making linear motion in the cylinder bore, resulting in the smoothness of the rack piston movement, and further resulting in a reduction in the torque output of the drive shaft.

[0029] In view of the above problems, the present invention provides Figure 1-7 The solution shown is an ultra-long stroke rack and pinion pneumatic actuator, comprising a cylinder body 1, a drive shaft 2 and a rack piston 3; the cylinder body 1 is cooperatively connected with the drive shaft 2, and the drive shaft 2 is meshed with the rack piston 3; its characteristics are: the cylinder body 1 comprises a left cylinder body 11, a middle cylinder body 12 and a right cylinder body 13; the left cylinder body 11, the middle cylinder body 12 and the right cylinder body 13 are interconnected to form the cylinder body 1; the drive shaft 2 and the rack piston 3 are both located in the middle cylinder body 12.

[0030] The left cylinder body 11, the middle cylinder body 12 and the right cylinder body 13 are each provided with a cylinder body inner hole 14; the cylinder body inner hole 14 runs through the entire cylinder body 1; the cylinder body inner holes 14 on the three combined cylinder bodies are of the same size and at the same position.

[0031] The left cylinder body 11 is provided with a first positioning countersunk hole 111, a first connecting through hole 112 and a first positioning pin hole 113; the first positioning countersunk hole 111 is provided at one end edge of the cylinder body inner hole 14 located on the left cylinder body 11; and a plurality of first connecting through holes 112 and first positioning pin holes 113 are provided on the end face on one side where the left cylinder body 11 is connected to the middle cylinder body 12.

[0032] The intermediate cylinder body 12 is provided with a positioning step 121, a vent hole 122, a connecting sealing ring groove 123, a connecting threaded hole 124 and a positioning pin matching hole 125; the edges of both ends of the cylinder body inner hole 14 located on the intermediate cylinder body 12 are provided with positioning steps 121; the positioning step 121 is also provided with a connecting sealing ring groove 123, and the end faces of both sides of the intermediate cylinder body 12 are provided with vent holes 122, connecting threaded holes 124 and positioning pin matching holes 125.

[0033] The right cylinder body 13 is provided with a second positioning countersunk hole 131, a second connecting through hole 132 and a second positioning pin hole 133; the cylinder body inner hole 14 located on the right cylinder body 13 is provided with a second positioning countersunk hole 131 at one end edge; and a plurality of second connecting through holes 132 and second positioning pin holes 133 are provided on the end surface on one side where the right cylinder body 13 is connected to the middle cylinder body 12.

[0034] The left cylinder body 11 is provided with a first positioning countersunk hole 111, the middle cylinder body 12 is provided with a positioning step 121, and the right cylinder body 13 is provided with a second positioning countersunk hole 131; the left cylinder body 11 and the middle cylinder body 12 are connected by the first positioning countersunk hole 111 and the positioning step 121; the right cylinder body 13 and the middle cylinder body 12 are connected by the second positioning countersunk hole 131 and the positioning step 121.

[0035] The left cylinder body 11 is provided with a first connecting through hole 112 and a first positioning pin hole 113; the middle cylinder body 12 is provided with a connecting threaded hole 124 and a positioning pin matching hole 125; the right cylinder body 13 is provided with a second connecting through hole 132 and a second positioning pin hole 133;

[0036] The left cylinder body 11 and the middle cylinder body 12 are fixed by the first connecting through hole 112 and the connecting threaded hole 124, the first positioning pin hole 113 and the positioning pin matching hole 125; the middle cylinder body 12 and the right cylinder body 13 are fixed by the connecting threaded hole 124 and the second connecting through hole 132, the positioning pin matching hole 125 and the second positioning pin hole 133.

[0037] It also includes a connecting sealing ring; the connecting sealing ring is arranged in the connecting sealing ring groove 123; the edge of the vent hole 122 is also provided with a vent hole sealing ring groove, and a corresponding sealing ring is arranged in the groove.

[0038] The present invention avoids the problem of a single cylinder body being too long while ensuring the motion stroke of the rack piston. Taking a cylinder body with an inner hole diameter of 210 mm as an example, the length of the cylinder body when the drive shaft rotates 180 degrees is 614 mm, and the total length is maintained unchanged, and the original cylinder body is decomposed into three cylinder bodies, namely the left cylinder body 11, the middle cylinder body 12 and the right cylinder body 13.

[0039] The length of the middle cylinder body 12 is 276 mm, and the lengths of the left cylinder body 11 and the right cylinder body 13 are both 169 mm, which are shorter than the cylinder body with a length of 361 mm when the drive shaft rotates at an angle of 90 degrees. Therefore, under the existing process conditions, the form and position tolerance of the cylinder body inner hole roundness of 0.05 mm and the form and position tolerance of the cylinder body inner hole cylindricity of 0.05 mm can be fully guaranteed.

[0040] In the prior art, the bottom connecting shaft hole, bottom connecting thread, top connecting thread and vent interface of the cylinder body 1 of the rack and pinion pneumatic actuator are all parts that connect the pneumatic actuator to other valve accessories or valves, that is, functional holes of the cylinder body. The intermediate cylinder body 12 of the present invention assumes these connecting functions of the cylinder body in the prior art, so the bottom connecting shaft hole, bottom connecting thread, top connecting thread and vent interface are all processed on the intermediate cylinder body.

[0041] In order to ensure the connection accuracy of the three cylinders, positioning steps 121 are processed at both ends of the middle cylinder 12, which are matched and connected with the first positioning countersunk holes 111 and the second positioning countersunk holes 131 processed on the left cylinder 11 and the right cylinder 13. The matching relationship between the step and the countersunk hole is a transition fit, and the matching tolerance is an upper deviation of +0.02mm and a lower deviation of -0.02mm, so that the shape and position tolerance of the inner cylindricity of the cylinder body assembled by the three cylinders is guaranteed to be 0.05mm.

[0042] At both ends of the middle cylinder 12, there are also connecting sealing ring grooves 123 and vent holes 122. The sealing rings arranged therein prevent air leakage when the three cylinders are assembled and working. The left cylinder 11, the middle cylinder 12 and the right cylinder 13 are all provided with positioning pin holes that match each other. When the three cylinders are assembled, the relative positions of the three cylinders are fixed with positioning pins. By positioning the connecting steps and the connecting countersunk holes in the circumferential direction and the position positioning of the pin holes, it can be ensured that after assembly, the surfaces of the three cylinders in the same direction are on the same horizontal plane, ensuring the aesthetics.

[0043] The left cylinder body 11 and the right cylinder body 13 are not provided with an axial hole for the drive shaft, and only the inner hole 14 of the cylinder body and the connecting through hole corresponding to the end thread of the middle cylinder body 12 are left. The two are connected by a connecting piece, so that the actuator end cover is fixed on the cylinder body 1.

[0044] The design principle of the middle cylinder 12 is that the length must be controlled within a design range so that after the rack piston is assembled into the cylinder 1, the plastic guide ring groove and the sealing ring groove of the rack piston do not contact the joints of the three cylinder assemblies during movement. This design principle avoids the wear of the rack piston guide ring and the sealing ring of the fixture due to the back and forth movement of the rack piston guide ring and the sealing ring at the joint. Correspondingly, the design lengths of the left cylinder 11 and the right cylinder 13 are designed to ensure that the long-stroke rack piston has sufficient movement stroke.

Claims

1. An ultra-long stroke rack and pinion pneumatic actuator, comprising a cylinder body (1), a drive shaft (2) and a rack piston (3); the cylinder body (1) is cooperatively connected with the drive shaft (2), and the drive shaft (2) is meshed with the rack piston (3); the characteristics are: The rotational stroke angles of the ultra-long-stroke rack and pinion pneumatic actuator are 120 degrees, 135 degrees, 180 degrees, 270 degrees and 360 degrees; the cylinder body (1) comprises a left cylinder body (11), a middle cylinder body (12) and a right cylinder body (13); the left cylinder body (11), the middle cylinder body (12) and the right cylinder body (13) are interconnected to form the cylinder body (1); the drive shaft (2) and the rack piston (3) are both located in the middle cylinder body (12); The left cylinder body (11), the middle cylinder body (12) and the right cylinder body (13) are each provided with a cylinder inner hole (14); the cylinder inner hole (14) passes through the entire cylinder body (1); the cylinder inner holes (14) on the three combined cylinder bodies are of the same size and at the same position; The intermediate cylinder body (12) is provided with a positioning step (121), a vent hole (122), a connecting sealing ring groove (123), a connecting threaded hole (124) and a positioning pin matching hole (125); the inner hole (14) of the cylinder body on the intermediate cylinder body (12) is provided with a positioning step (121) at both ends; the positioning step (121) is also provided with a connecting sealing ring groove (123), and the end surfaces on both sides of the intermediate cylinder body (12) are provided with a vent hole (122), a connecting threaded hole (124) and a positioning pin matching hole (125); The plastic guide ring groove and the sealing ring groove of the rack piston (3) do not contact the joints of the three combined cylinder bodies during movement.

2. The ultra-long-stroke rack and pinion pneumatic actuator according to claim 1, characterized in that: The left cylinder body (11) is provided with a first positioning countersunk hole (111), a first connecting through hole (112) and a first positioning pin hole (113); an edge of one end of the cylinder body inner hole (14) on the left cylinder body (11) is provided with a first positioning countersunk hole (111); and a plurality of first connecting through holes (112) and first positioning pin holes (113) are provided on an end surface of a side where the left cylinder body (11) is connected to the middle cylinder body (12).

3. The ultra-long-stroke rack and pinion pneumatic actuator according to claim 1, characterized in that: The right cylinder body (13) is provided with a second positioning countersunk hole (131), a second connecting through hole (132) and a second positioning pin hole (133); a second positioning countersunk hole (131) is provided at one end edge of the cylinder body inner hole (14) on the right cylinder body (13); and a plurality of second connecting through holes (132) and second positioning pin holes (133) are provided on an end surface of a side where the right cylinder body (13) is connected to the middle cylinder body (12).

4. The ultra-long stroke rack and pinion pneumatic actuator according to claim 1, characterized in that: The left cylinder body (11) is provided with a first positioning countersunk hole (111), the middle cylinder body (12) is provided with a positioning step (121), and the right cylinder body (13) is provided with a second positioning countersunk hole (131); the left cylinder body (11) and the middle cylinder body (12) are connected by the first positioning countersunk hole (111) and the positioning step (121); and the right cylinder body (13) and the middle cylinder body (12) are connected by the second positioning countersunk hole (131) and the positioning step (121).

5. The ultra-long stroke rack and pinion pneumatic actuator according to claim 1, characterized in that: The left cylinder body (11) is provided with a first connecting through hole (112) and a first positioning pin hole (113); the middle cylinder body (12) is provided with a connecting threaded hole (124) and a positioning pin matching hole (125); and the right cylinder body (13) is provided with a second connecting through hole (132) and a second positioning pin hole (133); The left cylinder body (11) and the middle cylinder body (12) are fixed via a first connecting through hole (112) and a connecting threaded hole (124), a first positioning pin hole (113) and a positioning pin matching hole (125); the middle cylinder body (12) and the right cylinder body (13) are fixed via a connecting threaded hole (124) and a second connecting through hole (132), a positioning pin matching hole (125) and a second positioning pin hole (133).

6. The ultra-long stroke rack and pinion pneumatic actuator according to claim 1, characterized in that: It also includes a connecting sealing ring; the connecting sealing ring is arranged in a connecting sealing ring groove (123); the edge of the vent hole (122) is also provided with a vent hole sealing ring groove, and a corresponding sealing ring is arranged in the groove.

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