Surface throttling type frictionless balanced cylinder and working method

Abstract

The application discloses a surface throttling type frictionless balance cylinder and a working method, which comprises a front end cover, a cylinder body, a piston rod, a piston and a rear end cover; two circumferential grooves are formed on the outer surface of the piston, a circumferential groove adjacent to the front end cover is a gas supply groove, a circumferential groove adjacent to the rear end cover is a gas discharge groove, a gas discharge hole communicating with the inner cavity of the cylinder body is formed in the gas discharge groove, an axial gas supply channel is arranged on the end surface of the piston adjacent to the rear end cover, the gas discharge hole does not communicate with the gas supply channel, a gas supply hole communicating with the gas supply channel is formed in the gas supply groove, and three circumferential bosses are arranged on the outer surface of the piston so that gas enters the gap between the piston and the cylinder body to form a pressure gas film through surface throttling. The application has the advantages of small occupied space, simple machining and assembly, high precision and difficulty in damage, and can be reliably applied to the stable vertical movement of a vertical shaft of an ultra-precision machine tool.

Description

Technical Field

[0001] This invention belongs to the field of cylinder technology, and particularly relates to a surface-throttling frictionless balanced cylinder and its working method. Background Technology

[0002] Ultra-precision machine tools play a vital role in ultra-precision machining and measurement. In recent years, many scholars have conducted research on the vertical axis of ultra-precision machine tools. To ensure high-precision and stable vertical movement of the vertical axis, a suitable balancing system must be designed to counteract the gravity of the moving parts of the vertical axis. Furthermore, the balancing system must minimize friction to avoid affecting machining or measurement accuracy. Therefore, the balancing system plays a crucial role in ensuring the servo control accuracy and machining stability of the ultra-precision vertical axis. Currently, the most common vertical axis balancing systems are mechanical balancing and cylinder balancing.

[0003] Traditional cylinder structures typically reduce friction by improving the machining and assembly precision of components, using specialized low-friction materials, applying lubricant, and using diaphragm bladders. These methods only reduce friction through various means, but do not truly achieve frictionless operation. Currently, research on frictionless cylinders often uses air-bearing bearings to achieve frictionless performance. For example, CN116044859A involves a surface-throttling frictionless cylinder, employing a gas hydrostatic bearing and several small-orifice throttling devices to achieve throttling and frictionless contact. However, this approach increases assembly difficulty and affects operational accuracy. Domestic and international scholars have conducted extensive research and achieved significant results on the dynamic characteristics and operational stability of air-bearing bearings, and have also conducted considerable research on frictionless balancing cylinders. However, research on dedicated cylinders for the gravity balancing system of ultra-precision machine tool vertical axes is still relatively limited. Therefore, researching an air-bearing frictionless balancing cylinder suitable for the vertical axes of ultra-precision machine tools is imperative. Summary of the Invention

[0004] To overcome the limitations of existing technologies, this invention provides a surface-throttling frictionless balancing cylinder and its operating method. This throttling balancing cylinder is used for gravity balancing of the vertical axis of ultra-precision machine tools, meeting the requirements of high precision and smooth movement of the vertical axis.

[0005] A surface-throttling frictionless balanced cylinder includes a front cover, a cylinder body, a piston rod, a piston, and a rear cover. The cylinder body is arranged between the front cover and the rear cover and is sealed to both of them. The piston rod and the piston are arranged in the cylinder body. One end of the piston rod is slidably mounted on the front cover, and the other end of the piston rod is fixed to the piston. The piston is in sliding contact with the inner surface of the cylinder body.

[0006] Two circumferential grooves are formed on the outer surface of the piston. The circumferential groove adjacent to the front end cover is a gas supply groove, and the circumferential groove adjacent to the rear end cover is a gas release groove. A gas release hole communicating with the inner cavity of the cylinder is formed in the gas release groove. A gas supply channel is arranged axially on the end face of the piston adjacent to the rear end cover. The gas release hole is not connected with the gas supply channel. A gas supply hole communicating with the gas supply channel is formed on the gas supply groove. Three circumferential bosses are provided on the outer surface of the piston to allow gas to enter the gap between the piston and the cylinder for surface throttling and form a pressure gas film.

[0007] Furthermore, ball joints are connected to both ends of the piston rod. The ball joint at the rear end of the piston rod is connected to the connecting piston bolt through a fixed ball head nut. The connecting piston bolt is connected to the piston and is located at the center of the piston. The ball joint at the front end of the piston rod is connected to the fixed ball head bolt through a fixed ball head nut.

[0008] Furthermore, buffer bosses to prevent piston impact are fixed inside the front end cover and the rear end cover, respectively.

[0009] Furthermore, the three circumferential protrusions are respectively the first circumferential protrusion adjacent to the front end cover, the second circumferential protrusion and the third circumferential protrusion located on both sides of the unloading groove, and the third circumferential protrusion is arranged adjacent to the rear end cover.

[0010] A working method for a surface-throttling frictionless balancing cylinder: High-pressure gas first enters the cylinder body through the air inlet on the side of the rear end cover and the inner hole of the buffer boss. Part of the high-pressure gas entering the cylinder body flows into the gap between the piston and the cylinder body through the air supply channel inside the piston, and then through the air supply hole and air supply groove. Part of the high-pressure gas flowing into the gap through the air supply groove rises and encounters the first circumferential boss, where it undergoes surface throttling to form a pressure gas film, and then continues to move upward and is directly discharged from the cylinder body. Another part of the high-pressure gas flowing into the gap through the air supply groove falls and encounters the second circumferential boss, where it undergoes surface throttling to form a pressure gas film, and then enters the piston and cylinder body through the venting groove and venting hole and is discharged. Another part of the high-pressure gas entering the cylinder body directly enters the gap between the piston and the cylinder body from the bottom of the outer side of the piston near the rear end cover. The high-pressure gas moves upward and encounters the third circumferential boss, where it undergoes surface throttling to form a pressure gas film, and then enters the piston and cylinder body through the venting groove and venting hole and is discharged.

[0011] The advantages of this invention compared to the prior art are:

[0012] I. Existing frictionless cylinder air bearing throttling methods typically employ orifice throttling. Orifice throttling requires the additional installation of a throttling device, and the large number of throttling devices increases assembly difficulty and affects operational accuracy. Surface throttling, on the other hand, uses protrusions on the bearing's air film surface for throttling. Since there are no throttling orifices, there is no need to consider the limitation of reducing air film thickness, which can improve rigidity to a certain extent while reducing gas flow rate, making it widely used in precision shaft systems. Therefore, this invention adopts the surface throttling type.

[0013] II. Existing frictionless cylinders typically employ dual-supply systems to avoid gas backflow caused by pressure differences within the cylinder due to unidirectional air supply. This requires high precision in machining and assembly and consumes a large amount of air. This invention features two grooves on the piston: a venting groove at the lower part of the piston and a supply groove at the upper part. The venting groove ensures the pressure relief of high-pressure gas flowing upwards from the bottom and downwards from the upper supply groove, thus preventing gas backflow.

[0014] Third, the use of ball joints at both ends of the piston rod facilitates the assembly and adjustment of the piston rod and the vertical shaft connection, reducing the coaxiality requirements for the assembly and adjustment of the piston rod and the vertical shaft connection in traditional frictionless cylinders. The double ball joint design also avoids the additional bending moment of the surface throttling air bearing formed between the piston and the cylinder, ensuring that it is only subjected to radial loads. Simultaneously, the use of two simple structures—bolts and nuts at the fixed ball ends—ensures a stable connection between the piston and the piston rod.

[0015] Fourth, polyurethane buffer bosses are provided inside the cylinder, below the front end cover and above the rear end cover, to prevent large impacts from occurring during piston movement and thus avoid damaging the piston.

[0016] 5. An O-ring seal is used between the rear end cover and the cylinder body to ensure that the high-pressure gas will not leak from the bottom of the cylinder body.

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments: Attached Figure Description

[0018] Figure 1 This is a perspective view of the surface-throttling frictionless balancing cylinder of the present invention;

[0019] Figure 2 This is an exploded view of the surface-throttling frictionless balancing cylinder of the present invention;

[0020] Figure 3 This is a cross-sectional structural diagram of the present invention;

[0021] Figure 4 This is a perspective view of the piston of the present invention;

[0022] Figure 5This is a schematic diagram showing that the piston of the present invention has a circumferential boss.

[0023] Figure 6 This is a cross-sectional view of the piston;

[0024] Figure 7 for Figure 6 Cross-sectional view at point AA;

[0025] Figure 8 for Figure 6 Cross-sectional view at point BB;

[0026] Figure 9 This is a schematic diagram of the gas flow direction in this invention;

[0027] Explanation of icon numbers:

[0028] 1. Fixed ball head bolt; 2. Fixed ball head nut; 3. Ball joint; 4. Fixed nut; 5. Front end cap; 6. Buffer boss; 7. Cylinder body; 8. Piston rod; 9. Connecting piston bolt; 10. Piston; 10-1. Air supply groove; 10-3. Air supply channel; 10-2. Air vent groove; 10-4. First circumferential boss; 10-5. Second circumferential boss; 10-6. Third circumferential boss; 10-10. Air supply hole; 10-20. Air vent hole; 11. O-ring; 12. Universal connector; 13. Rear end cap. Detailed Implementation

[0029] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art.

[0030] Combination Figures 1-8 This embodiment of a surface-throttling frictionless balancing cylinder includes a front end cover 5, a cylinder body 7, a piston rod 8, a piston 10, and a rear end cover 13. The cylinder body 7 is arranged between the front end cover 5 and the rear end cover 13 and is sealed to both of them. The piston rod 8 and the piston 10 are arranged inside the cylinder body 7. One end of the piston rod 8 is slidably mounted on the front end cover 5, and the other end of the piston rod 8 is fixed to the piston 10. The piston 10 is in sliding contact with the inner surface of the cylinder body 7.

[0031] Two circumferential grooves are formed on the outer surface of the piston 10. The circumferential groove adjacent to the front end cover 5 is the air supply groove 10-1, and the circumferential groove adjacent to the rear end cover 13 is the air release groove 10-2. An air release hole 10-20 communicating with the inner cavity of the cylinder 7 is formed in the air release groove 10-2. An air supply channel 10-3 is arranged axially on the end face of the piston 10 adjacent to the rear end cover 13. The air release hole 10-20 is not connected with the air supply channel 10-3. An air supply hole 10-10 communicating with the air supply channel 10-3 is formed on the air supply groove 10-1. Three circumferential bosses are provided on the outer surface of the piston 10 to allow gas to enter the gap between the piston 10 and the cylinder 7 for surface throttling to form a pressure gas film.

[0032] In this embodiment, two circumferential grooves are provided on the piston. The groove located at the rear of the piston is a venting groove, and the groove located at the front of the piston is a supply groove. The venting groove ensures the depressurization of high-pressure gas from the bottom upward and high-pressure gas from the upper supply groove downward, thereby avoiding the phenomenon of gas backflow.

[0033] This embodiment designs air supply grooves, air supply holes, and air discharge grooves, air discharge holes, and air supply channels, and their interrelationships, and incorporates circumferential bosses to allow gas to enter the gap between the piston 10 and the cylinder 7 for surface throttling, forming a pressure gas film. This ensures non-contact between the piston and the cylinder, achieving frictionless reciprocating motion. This overcomes the weaknesses of conventional methods that only reduce friction, such as improving the machining and assembly precision of parts, using special low-friction materials, applying lubricant, or using diaphragms. This throttling-type balanced cylinder has a small overall footprint, simple machining and assembly, high precision, and is reliably applicable to the high-precision, stable vertical motion of ultra-precision machine tools.

[0034] Specifically, such as Figure 4 and Figure 5 As shown, the three circumferential protrusions are the first circumferential protrusion 10-4 adjacent to the front end cover 5, the second circumferential protrusion 10-5 and the third circumferential protrusion 10-6 located on both sides of the unloading groove 10-2, and the third circumferential protrusion 10-6 is arranged adjacent to the rear end cover 13.

[0035] The first circumferential boss 10-4 and the second circumferential boss 10-5 respectively ensure that a portion of the high-pressure gas flowing into the gap from the air supply groove 10-1 is throttled upwards by the circumferential boss to form a pressure gas film, and another portion of the high-pressure gas flowing into the gap from the air supply groove 10-1 is throttled downwards by the circumferential boss to form a pressure gas film. The third circumferential boss 10-6 ensures that another portion of the high-pressure gas entering the cylinder 7 moves upwards by throttled upwards by the circumferential boss to form a pressure gas film.

[0036] Specifically, such as Figure 3As shown, buffer bosses 6 are fixed inside the front cover 5 and the rear cover 13 to prevent the piston 10 from impacting. Furthermore, the buffer bosses 6 are made of polyurethane. This design avoids large impacts during piston movement that could damage the piston.

[0037] The air supply port 10-10 and the air discharge port 10-20 are both set perpendicular to the axial direction of the cylinder body 7 to ensure stable gas flow.

[0038] Specifically, such as Figure 3 As shown, ball joints 3 are connected to both ends of the piston rod 8. The ball joint 3 at the rear end of the piston rod 8 is connected to the connecting piston bolt 9 via a fixing ball head nut 2. The connecting piston bolt 9 is connected to the piston 10, and the connecting piston bolt 9 is located at the center of the piston 10. The ball joint 3 at the front end of the piston rod 8 is connected to the fixing ball head bolt 1 via a fixing ball head nut 2. The purpose of this arrangement is to facilitate the assembly and adjustment of the piston rod and the vertical shaft connection by using a ball joint structure at both ends of the piston rod, reducing the coaxiality requirements for the assembly and adjustment of the piston rod and the vertical shaft connection of traditional frictionless cylinders. The double ball joint design can also avoid the additional bending moment of the surface throttling air bearing formed between the piston and the cylinder body by the piston rod, so that it is only subjected to radial load. At the same time, the use of two simple structures, the fixing ball head bolt and the fixing ball head nut, ensures the stable connection between the piston and the piston rod, realizing the connection and fixation with external actuators. The fixing ball head bolt 1 is provided with a threaded boss to facilitate the installation with the vertical shaft connection.

[0039] Specifically, the cylinder body 7 and the rear end cover 13 are sealed by an O-ring 11. This arrangement ensures that the introduced high-pressure gas will not leak from the bottom of the cylinder body.

[0040] Furthermore, an air inlet is provided on the side of the rear cover 13, which is connected to the air supply channel 10-3 and the universal connector 12. The purpose of this arrangement is that gas enters the cylinder through the air inlet and finally flows out of the cylinder through the inner hole of the front cover 5.

[0041] Based on any of the foregoing embodiments or combinations thereof, a surface-throttling frictionless balancing cylinder is also provided, along with a method for operating the surface-throttling frictionless balancing cylinder. Figures 6-9 illustrate( Figure 9 The direction indicated by the middle arrow is the direction of gas flow. Figures 7-9 In the diagram, points C, D, E, F, H, and G represent the corresponding circumferential bosses and the transition areas of the remaining piston surfaces, and... Figure 9The diagram shows the airflow direction and the pressure film formed by surface throttling in the magnified area. C and F represent the first circumferential boss 10-4, D and G represent the second circumferential boss 10-5, E and H represent the third circumferential boss 10-6, J represents the magnified view of the gap between the piston 10 and the cylinder 7 at the air supply groove, and I represents the magnified view of the gap between the piston 10 and the cylinder 7 at the air discharge groove to facilitate understanding of this embodiment.

[0042] High-pressure gas first enters the cylinder 7 through the side air inlet of the rear end cover 13 and the inner hole of the buffer boss 6. Part of the high-pressure gas entering the cylinder 7 flows into the gap between the piston 10 and the cylinder body 7 through the air supply channel 10-3 inside the piston 10, and then through the air supply hole 10-10 and the air supply groove 10-1. Part of the high-pressure gas flowing into the gap through the air supply groove 10-1 rises and encounters the first circumferential boss 10-4 (bore at C and F) for surface throttling to form a pressure gas film, and then continues to move upward and is directly discharged from the cylinder body 7; the other part of the high-pressure gas flowing into the gap through the air supply groove 10-1 falls downward ... The pressure gas film is formed by surface throttling at the second circumferential boss 10-5 (bosses at D and G), and then enters the piston 10 and cylinder 7 through the venting groove 10-2 and venting hole 10-20 and is discharged. Another part of the high-pressure gas entering the cylinder 7 directly enters the gap between the piston 10 and cylinder 7 from the bottom of the outer side of the piston 10 adjacent to the rear end cover 13. The high-pressure gas moves upward and encounters the third circumferential boss 10-6 (bosses at E and H) for surface throttling to form a pressure gas film. Then, it enters the piston 10 and cylinder 7 through the venting groove 10-2 and venting hole 10-20 and is discharged.

[0043] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed structure and technical content to create equivalent embodiments without departing from the scope of the present invention, and all such modifications or alterations shall still fall within the scope of the present invention.

Claims

1. A surface-throttling frictionless balancing cylinder, comprising a front end cover (5), a cylinder body (7), a piston rod (8), a piston (10), and a rear end cover (13), wherein a cylinder body (7) is arranged between the front end cover (5) and the rear end cover (13) and is sealed to both of them, the piston rod (8) and the piston (10) are arranged inside the cylinder body (7), one end of the piston rod (8) is slidably disposed on the front end cover (5), and the other end of the piston rod (8) is fixed on the piston (10), and the piston (10) slides in contact with the inner surface of the cylinder body (7); Its features are: Two circumferential grooves are formed on the outer surface of the piston (10). The circumferential groove adjacent to the front end cover (5) is a gas supply groove (10-1), and the circumferential groove adjacent to the rear end cover (13) is a gas discharge groove (10-2). A gas discharge hole (10-20) communicating with the inner cavity of the cylinder (7) is formed in the gas discharge groove (10-2). A gas supply channel (10-3) is arranged axially on the end face of the piston (10) adjacent to the rear end cover (13). The gas discharge hole (10-20) is not connected to the gas supply channel (10-3). A gas supply hole (10-10) communicating with the gas supply channel (10-3) is formed on the gas supply groove (10-1). Three circumferential bosses are provided on the outer surface of the piston (10) to allow gas to enter the gap between the piston (10) and the cylinder (7) for surface throttling to form a pressure gas film. The three circumferential bosses are respectively adjacent to the front end cover (5). The first circumferential boss (10-4), the second circumferential boss (10-5) and the third circumferential boss (10-6) located on both sides of the unloading groove (10-2), the third circumferential boss (10-6) is arranged adjacent to the rear end cover (13), the front end cover (5) and the rear end cover (13) are respectively fixed with buffer bosses (6) to prevent the piston (10) from impacting. The buffer bosses (6) are made of polyurethane. The two ends of the piston rod (8) are respectively connected to ball joints (3). The ball joint (3) at the rear end of the piston rod (8) is connected to the connecting piston bolt (9) through the fixing ball head nut (2). The connecting piston bolt (9) is connected to the piston (10). The connecting piston bolt (9) is located at the center of the piston (10). The ball joint (3) at the front end of the piston rod (8) is connected to the fixing ball head bolt (1) through the fixing ball head nut (2).

2. The surface-throttling frictionless balancing cylinder according to claim 1, characterized in that: Both the air supply port (10-10) and the air discharge port (10-20) are arranged perpendicular to the axial direction of the cylinder body (7).

3. The surface-throttling frictionless balancing cylinder according to claim 1, characterized in that: The cylinder (7) and the rear end cover (13) are sealed by an O-ring (11).

4. The surface-throttling frictionless balancing cylinder according to claim 1, characterized in that: An air inlet is provided on the side of the rear cover (13), and the air inlet is connected to the air supply channel (10-3) and the universal connector (12) respectively.

5. A method for operating a surface-throttling frictionless balancing cylinder according to claim 1, characterized in that: High-pressure gas first enters the cylinder body (7) through the side air inlet of the rear end cover (13) and the inner hole of the buffer boss (6). Part of the high-pressure gas entering the cylinder body (7) flows into the gap between the piston (10) and the cylinder body (7) through the air supply channel (10-3) inside the piston (10) and then through the air supply hole (10-10) and the air supply groove (10-1). Part of the high-pressure gas flowing into the gap through the air supply groove (10-1) rises and encounters the first circumferential boss (10-4) for surface throttling to form a pressure gas film, and then continues to move upward and is directly discharged from the cylinder body (7). The other part of the high-pressure gas flowing into the gap through the air supply groove (10-1) As it moves downward, it encounters the second circumferential boss (10-5) for surface throttling to form a pressure gas film. Then, it enters the piston (10) and cylinder (7) through the venting groove (10-2) and venting hole (10-20) and is discharged. Another part of the high-pressure gas entering the cylinder (7) directly enters the gap between the piston (10) and cylinder (7) from the bottom of the outer side of the piston (10) near the rear end cover (13). The high-pressure gas moves upward and encounters the third circumferential boss (10-6) for surface throttling to form a pressure gas film. Then, it enters the piston (10) and cylinder (7) through the venting groove (10-2) and venting hole (10-20) and is discharged.

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