Surface restricted frictionless air cylinder

Abstract

The application relates to a surface throttling type frictionless air cylinder, which belongs to the technical field of air cylinders. The air cylinder has the advantages of simple structure, good stability, high precision, small gas consumption, small size and convenient machining. The front end of a piston rod is supported in the inside of a cylinder barrel through a gas static pressure bearing, the rear end of the piston rod is connected with a piston, the piston is arranged in the inside of the cylinder barrel, the rear end of the cylinder barrel is provided with a rear end cover, and the front end of the cylinder barrel is provided with a front end cover. The air cylinder only needs single-way gas supply. High-pressure gas is subjected to surface throttling in the micron-level wedge-shaped gap between the piston and the cylinder barrel to form a pressure gas film. The piston is provided with a pressure relief groove, and the excess gas is discharged through the pressure relief groove. The gas film gap is different, and the gas pressure gradient distribution is different, so that the gas backflow can be avoided while the bearing capacity of the gas film is ensured, the pipeline is simple, the machining and assembly are convenient, the gas consumption is minimum in all frictionless air cylinder schemes, and the pneumatic noise is minimum. According to the air floating principle, the frictionless movement is realized, the precision is high due to the self-centering characteristics of the conical surface, and the reliability is improved.

Description

Technical Field

[0001] This invention belongs to the field of cylinder technology, specifically relating to a surface-throttling frictionless cylinder. Background Technology

[0002] Cylinders are common pneumatic actuators used to transmit displacement and control thrust. Traditional cylinders typically employ mechanical seals during assembly. This involves using a sealing ring fitted over the piston and piston rod with an interference fit. This leads to sliding friction between the piston and cylinder, and between the piston rod and guide sleeve, during reciprocating motion. The frictional force generated by this sliding friction is a non-linear viscous resistance, changing with the piston's speed. Furthermore, friction always hinders the movement of the component. Even with a constant cylinder air pressure, the presence of sliding friction causes the thrust on the piston to fluctuate continuously. Therefore, traditional mechanical seals have a certain impact on the accuracy and stability of cylinder thrust, limiting their application in ultra-precision machining. Current ultra-precision machine tools often employ air hydrostatic bearing lubrication for cylinder balancing. This involves evenly distributing throttling holes and grooves on the piston rod guide sleeve and creating throttling holes on the piston itself. An air hydrostatic bearing pair is formed between the piston rod guide sleeve, the piston rod, and the piston and cylinder, achieving contactless sealing and frictionless movement of the cylinder.

[0003] There are many existing air-static pressure-guided frictionless cylinder structures, and the choice of throttling method and air supply scheme has a certain impact on the stability and accuracy of cylinder movement. Ordinary single-acting frictionless cylinders have a single-path air supply on one side of the cylinder. Although the machining and assembly are relatively simple and the air consumption is small, there is a large pressure difference between the high-pressure and low-pressure chambers. This causes a pressure flow within the gap between the piston and the cylinder body, resulting in gas backflow into the high-pressure chamber. This affects the formation of the air film within the gap. Simultaneously, errors cause the piston to be conical and eccentric, resulting in different pressure drops across the gap, creating a radial imbalance force that increases the piston's eccentricity and causes jamming. Ordinary double-acting cylinders have air supply ports in both the rod-side and rodless-side chambers, preventing gas backflow. However, the structure is more complex, the air consumption is higher, and the volume is larger, making it unsuitable for environments with limited working space. Throttling methods typically employ the relatively mature small-orifice throttling technique. Throttling orifices are evenly distributed radially on the piston, allowing high-pressure gas to pass through the throttler and form a supporting gas film within the gap, suspending the piston in the working chamber and achieving frictionless reciprocating motion. However, this method of creating throttling orifices on the piston is difficult to manufacture, and the throttler is prone to clogging and maintenance. Therefore, it is necessary to design a space-saving, simple to manufacture and assemble, low-gas-consumption, high-precision, and reliable air-float frictionless cylinder. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a unidirectional air supply surface throttling frictionless cylinder with simple structure, good stability, high precision, low air consumption, small size and convenient processing.

[0005] The technical solution adopted in this invention is: a surface-throttling frictionless cylinder, including a piston, a piston rod, and a cylinder barrel; the front end of the piston rod is supported inside the cylinder barrel by a gas hydrostatic bearing, the rear end of the piston rod is connected to the piston, the piston is disposed inside the cylinder barrel, the rear end of the cylinder barrel is provided with a rear end cover, and the front end of the cylinder barrel is provided with a front end cover.

[0006] Compared with the prior art, the present invention has the following advantages:

[0007] 1. Existing air-static pressure-guided frictionless cylinders typically employ dual-path air supply to avoid gas backflow caused by the pressure difference between the rodless and rod chambers due to unidirectional air supply. This requires high precision in machining and assembly and consumes a large amount of air. This invention requires only a single-path air supply. High-pressure gas undergoes surface throttling in the micron-level wedge-shaped gap between the piston and cylinder to form a pressure film. Excess gas is discharged using a pressure relief groove on the piston. By utilizing the different gas pressure gradient distribution due to varying gaps in the gas film, backflow is avoided while ensuring the load-bearing capacity of the gas film. The piping is simple, machining and assembly are convenient, and it has the lowest air consumption and pneumatic noise among all frictionless cylinder designs. The structure is compact, and the axial sealing length can be designed with a short shaft, resulting in a small overall footprint and facilitating integration of the cylinder into a vertical axis counterweight system. Frictionless motion is achieved based on the principle of air flotation, and the self-centering characteristic of the conical shape ensures high precision and improved reliability.

[0008] 2. The radial stiffness of the gas film between the piston and cylinder of the present invention, i.e. the anti-overturning ability, is related to the gas supply pressure. Therefore, accurate design and calculation are required. Thus, the present invention adopts a ball joint or similar structure at the connection between the piston rod and the piston and at the connection between the piston rod and the external actuator to relax this limitation. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the axial cross-sectional structure of the present invention;

[0010] Figure 2 This is a schematic axial cross-sectional view of the piston of the present invention;

[0011] Figure 3 yes Figure 2 AA cross-section view;

[0012] Figure 4 yes Figure 2 BB cross-section;

[0013] Figure 5 This is a schematic diagram of the gas flow direction of the present invention;

[0014] The components are: 1. Piston rod; 2. Front end cover; 3. Bearing housing; 4. Air inlet; 5. Bearing air inlet passage; 6. Working air inlet passage; 7. Throttling device; 8. Gas static pressure bearing; 9. Cylinder; 10. Ball head; 11. Ball pin seat; 12. Wedge clearance; 13. Piston; 14. Rear end cover; 15. Air outlet; 16. Pressure relief hole; 17. Pressure relief groove; 18. Sealing ring A; 19. Elastic retaining ring A; 20. Elastic retaining ring B; 21. Sealing ring B; 22. Fixing nut; 23. Thread. Detailed Implementation

[0015] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0016] Reference Figures 1-5 As shown, the surface throttling frictionless cylinder of the present invention includes a piston 13, a piston rod 1, and a cylinder 9; the front end of the piston rod 1 is supported inside the cylinder 9 by a gas hydrostatic bearing 8, the rear end of the piston rod 1 is connected to the piston 13, the piston 13 is disposed inside the cylinder 9, the rear end of the cylinder 9 is provided with a rear end cover 14, which is fixed by bolts, and the front end of the cylinder 9 is provided with a front end cover 2, which is fixed by bolts.

[0017] like Figure 1 As shown, an air inlet 4 is provided at the front end of the cylinder 9, making the front end of the cylinder 9 a high-pressure chamber and the rear end a low-pressure chamber. An air outlet 15 is provided at the rear end of the cylinder 9. The air outlet 15 is specifically provided on the rear end cover 14. The air inlet 4 is specifically provided on the bearing seat 3.

[0018] like Figures 1-5 As shown, there is a micron-sized wedge-shaped gap 12 between the piston 13 and the cylinder 9. The piston 13 has a conical structure, with the small-diameter end of the piston 13 facing the high-pressure chamber of the cylinder 9. Multiple radial pressure relief grooves 17 are evenly distributed around the outer wall of the front end of the piston 13. Multiple axial pressure relief holes 16 are evenly distributed around the rear end of the multiple pressure relief grooves 17 and communicate with them. The rear end of each pressure relief hole 16 communicates with the low-pressure chamber of the cylinder 9. A gentle slope is provided at the outer wall of the piston 13 at the front end of the pressure relief groove 17 so that part of the gas in the high-pressure chamber flows into the wedge-shaped gap 12, and the other part flows into the pressure relief groove 17 and is discharged through the vent hole 15.

[0019] There is a micron-sized wedge-shaped gap 12 between the piston 13 and the cylinder 9. The high-pressure gas is throttled on the surface through the wedge-shaped gap 12, so that a bearing gas film with a certain rigidity is generated on the circumferential surface of the piston 13. Part of the gas film flows into the low-pressure chamber through the wedge-shaped gap 12 between the piston 13 and the cylinder 9, and the remaining gas flows into the low-pressure chamber through the pressure relief groove 17 opened on the piston 13. Finally, the gas in the low-pressure chamber is discharged to the atmosphere through the vent hole 15 of the rear end cover 14.

[0020] like Figure 1 As shown, the piston rod 1 has a ball joint structure at its rear end, and the piston 13 has a threaded hole on its front end face for connecting the ball joint structure.

[0021] like Figure 1 As shown, the ball joint structure includes a ball head 10 and a ball pin seat 11. The front end of the ball head 10 is connected to the rear end of the piston rod 1, and the rear end of the ball head 10 is mounted on the ball pin seat 11. The ball pin seat 11 is screwed into the threaded hole of the piston 13.

[0022] The piston rod 1 has a thread 23 at its front end and is fitted with a fixing nut 22 to achieve connection and fixation with external actuators.

[0023] like Figure 1 As shown, the gas static pressure bearing 8 adopts a relatively mature orifice throttling method. The gas static pressure bearing 8 has multiple rows of orifice channels evenly distributed along the circumference. An orifice throttling device 7 is provided inside the orifice channel. The gas static pressure bearing 8 and the piston rod 1 are fitted with a clearance. There is an annular gap I between the outer wall of the piston rod 1 and the inner wall of the gas static pressure bearing 8.

[0024] The gas static pressure bearing 8 is fitted with a bearing seat 3 on its outer side. An annular gap II is provided between the gas static pressure bearing 8 and the bearing seat 3 to ensure that the gas static pressure bearing 8 has sufficient radial movement space when the circumferential gas pressure field changes. The bearing seat 3 is connected to the front end of the cylinder 9. A radial air inlet 4 is provided on the bearing seat 3. The air inlet 4 is connected to the annular gap II through the bearing air inlet channel 5. An axial working air inlet channel 6 is provided on the bearing seat 3 to connect the high pressure chamber of the cylinder 9 and the bearing air inlet channel 5. The air inlet 4 supplies air to the high pressure chamber of the gas static pressure bearing 8 and the cylinder 9 respectively. When the high pressure gas flows into the small orifice throttle 7 in the gas static pressure bearing 8 through the bearing air inlet channel 5, a gas film with a certain load-bearing stiffness will be formed in the annular gap I, causing the piston rod 1 to float and achieve frictionless contact.

[0025] A rectangular chamfer is provided at the connection between the bearing inlet air passage 5 and the annular gap II, which facilitates the transformation of the point pressure source into a linear pressure source.

[0026] The gas static pressure bearing 8 is fitted with sealing rings B21 and A18 at its front and rear ends, respectively. Sealing ring A18 prevents gas from leaking into the annular gap II from the working air intake passage 6. An elastic retaining ring B20 and a bore elastic retaining ring A19 are provided on the inner sidewall of the bearing housing 3 near sealing rings B21 and A18 to prevent axial movement of the sealing ring B21 at the front end and the sealing ring A18 at the rear end of the gas static pressure bearing 8.

[0027] A schematic diagram of the gas flow direction inside the surface-throttling frictionless cylinder of this invention is shown below. Figure 5As shown, high-pressure gas enters through the working inlet passage 6 and flows through the micron-sized wedge-shaped gap 12 between the piston 13 and the cylinder 9. Part of the gas generates a pressure gradient within the wedge-shaped gap 12, causing surface throttling. The resulting pressure film causes the piston to float, forming a frictionless reciprocating motion. The remaining gas film flows into the low-pressure chamber through the wedge-shaped gap 12. The remaining high-pressure gas flows into the pressure relief groove 17 and then into the low-pressure chamber through the pressure relief hole 16. The gas in the low-pressure chamber is discharged to the atmosphere through the vent hole 15 on the rear end cover 14.

[0028] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A surface-throttling frictionless cylinder, characterized in that: It includes a piston (13), a piston rod (1), and a cylinder (9); the front end of the piston rod (1) is supported inside the cylinder (9) by a gas hydrostatic bearing (8), the rear end of the piston rod (1) is connected to the piston (13), the piston (13) is located inside the cylinder (9), the rear end of the cylinder (9) is provided with a rear end cover (14), and the front end of the cylinder (9) is provided with a front end cover (2). An air inlet (4) is provided at the front end of the cylinder (9), so that the front end of the cylinder (9) is a high-pressure chamber and the rear end is a low-pressure chamber. An air outlet (15) is provided at the rear end of the cylinder (9). There is a wedge-shaped gap (12) between the piston (13) and the cylinder (9). The piston (13) has a conical structure. The small diameter end of the piston (13) faces the high pressure chamber of the cylinder (9). Multiple radial pressure relief grooves (17) are evenly distributed around the outer wall of the front end of the piston (13). Multiple axial pressure relief holes (16) are evenly distributed around the rear end of the multiple pressure relief grooves (17) and communicate with them. The rear end of each pressure relief hole (16) is connected to the low pressure chamber of the cylinder (9). A gentle slope is set at the outer wall of the piston (13) at the front end of the pressure relief groove (17) so that part of the gas in the high pressure chamber flows into the wedge-shaped gap (12) and generates a bearing gas film with a certain rigidity on the circumferential surface of the piston (13). Part of the gas film flows into the low pressure chamber through the wedge-shaped gap (12) between the piston (13) and the cylinder (9), and the other part flows into the pressure relief groove (17) and is discharged through the air outlet (15).

2. The surface-throttling frictionless cylinder according to claim 1, characterized in that: The piston rod (1) has a ball hinge structure at its rear end, and the piston (13) has a threaded hole at its front end for connecting the ball hinge structure.

3. The surface-throttling frictionless cylinder according to claim 2, characterized in that: The ball joint structure includes a ball head (10) and a ball pin seat (11). The front end of the ball head (10) is connected to the rear end of the piston rod (1), and the rear end of the ball head (10) is mounted on the ball pin seat (11). The ball pin seat (11) is helically mounted in the threaded hole of the piston (13).

4. The surface-throttling frictionless cylinder according to claim 2, characterized in that: The piston rod (1) has a thread (23) at its front end and is fitted with a fixing nut (22) to achieve connection and fixation with external actuators.

5. The surface-throttling frictionless cylinder according to claim 1, characterized in that: The gas static bearing (8) has multiple rows of small holes evenly distributed along its circumference. A small hole throttle (7) is provided inside the small hole channel. The gas static bearing (8) and the piston rod (1) are fitted with a clearance. There is an annular gap I between the outer wall of the piston rod (1) and the inner wall of the gas static bearing (8).

6. The surface-throttling frictionless cylinder according to claim 5, characterized in that: The gas static pressure bearing (8) is fitted with a bearing housing (3) on its outer side. An annular gap II is provided between the gas static pressure bearing (8) and the bearing housing (3). The bearing housing (3) is connected to the front end of the cylinder (9). An air inlet (4) is provided on the bearing housing (3). The air inlet (4) is connected to the annular gap II through the bearing air inlet channel (5). A working air inlet channel (6) is provided on the bearing housing (3) to connect the cylinder (9) and the bearing air inlet channel (5).

7. The surface-throttling frictionless cylinder according to claim 6, characterized in that: A rectangular chamfer is provided at the connection between the bearing inlet air passage (5) and the annular gap II, which facilitates the transformation of the point pressure source into a linear pressure source.

8. The surface-throttling frictionless cylinder according to claim 7, characterized in that: The gas static pressure bearing (8) is fitted with sealing ring B (21) and sealing ring A (18) at its front and rear ends respectively. An elastic retaining ring B (20) and a hole elastic retaining ring A (19) are provided on the inner side wall of the bearing seat (3) near the sealing ring B (21) and sealing ring A (18).

Images