CN102155465A - Zero-friction air cylinder with air bearing - Google Patents

Abstract

The invention discloses a zero-friction air cylinder with an air bearing. The zero-friction air cylinder comprises the air bearing and a piston, wherein the air bearing is matched with the piston rod; the piston is designed according to an air-float principle; and the zero-friction support of a moving part and a fixed part of the air cylinder can be realized by the air-float bearing and the piston, namely a high-pressure air film is formed at a contact surface to isolate two surfaces which are supported mutually. Air is provided for the piston in the inner part of the air cylinder by the zero-friction air cylinder through the hollow piston rod and a soft pipe, and spherical hinge connection is applied, thus the zero-friction air cylinder can bear certain radial loading, and the piston is not stuck in the air cylinder; by the zero-friction air cylinder provided by the invention, the friction of the air cylinder is reduced greatly, greater stroke can be realized without lubrication and sealing, the radial force in a certain range can be borne, and the structure is simple and is convenient to maintain.

Description

Frictionless cylinders with air bearings

technical field

The invention relates to a cylinder, in particular to a frictionless cylinder with an air bearing.

Background technique

The friction force of the cylinder is generated by contact friction, specifically the friction between the rubber seal ring and the cylinder barrel and the friction between the piston rod and the dust ring.

In order to reduce the friction force, a well-known method is to reduce the friction force of the cylinder by improving the machining accuracy of the cylinder, using special grease, and using materials with a small friction coefficient. This traditional low-friction cylinder reduces friction by improving the smoothness of the contact surface and improving lubrication conditions on the basis of ordinary cylinders. This traditional method reduces the frictional force of the cylinder to a certain extent, but has the defects of difficult processing, high cost, difficult maintenance and short service life.

Another well-known approach uses new technologies such as gap seals and ball guide bushings. This new type of low-friction cylinder greatly reduces the friction between the piston rod and the end cover through the use of gap seals. A ball guide sleeve is also used between the piston and the cylinder, and the use of ball support also effectively reduces the friction. The new low-friction cylinder has breakthroughs in uniform velocity, high and low pressure friction, high speed and high frequency. However, it also has some defects, such as sensitivity to radial load, complex structure, difficult manufacturing and high price.

There is also a well known diaphragm type low friction cylinder. This is an actuator that uses a diaphragm bag as a seal, no air leakage, no lubrication, and low friction. There is a diaphragm bag connected to each other between the piston and the inner wall of the cylinder, and there is no direct contact between the two, and the front end of the piston rod adopts a linear ball bearing, which greatly reduces the friction of the cylinder. Although this type of cylinder has many advantages, due to the limitation of the diaphragm structure, its cylinder stroke is generally not very large.

Contents of the invention

The purpose of the present invention is to provide a frictionless cylinder with an air bearing, which not only solves the complex structure, difficult processing and maintenance, radial load and Sensitivity and other defects, but also has the characteristics of large stroke and ultra-low friction.

The technical solution adopted by the present invention to solve the technical problem is: a frictionless cylinder with an air bearing, the cylinder has a piston and a piston rod with an internal air flow channel, the two pass through a ball joint The piston joint of the structure is connected, and there is a certain gap between the piston and the cylinder barrel, and the compressed air can be supplied to the gap through the orifice. It is characterized in that the front end of the piston rod is supported by the air bearing, and the rear end is The piston connector is connected to the piston.

Further, the piston is designed according to the principle of air bearing, and it is hollow inside, with orifices distributed in the circumferential direction so that the compressed air in the piston cavity can flow to the gap to form a high-pressure air film to support the piston.

Further, a certain number of orifices are evenly distributed along the circumference of the piston, and a pressure equalization cavity is provided at the end of the orifices.

Further, there are several rows of throttle holes distributed along the piston's circumferential direction in the axial direction of the piston, and are distributed symmetrically.

Further, the piston joint connecting the piston and the piston rod has a ball joint to ensure that the piston and the piston rod can have a certain eccentricity.

Further, the piston rod is hollow, and the air flow channel inside it communicates with the inner cavity of the piston through a hose.

Further, the compressed air enters from the air inlet of the bearing, and enters the inner cavity of the piston through the air flow channel and the hose to realize air supply.

The beneficial effect of the invention is that the invention greatly reduces the friction force of the cylinder, can realize a larger stroke, does not need lubrication and sealing, can bear radial force within a certain range, has a simple structure, and is convenient for maintenance.

Description of drawings

Figure 1 is a perspective view of a frictionless cylinder made in accordance with the present invention;

Fig. 2 is a sectional view of the movable part of the cylinder;

Fig. 3 is a partial sectional view of the air bearing;

Fig. 4 is the piston sectional diagram of example 1;

Fig. 5 is the piston air flotation principle diagram of example 1;

Fig. 6 is the piston sectional sketch of example 2;

Fig. 7 is the piston air flotation principle diagram of example 2;

Fig. 8 is a cutaway sectional view of the piston rod;

In the figure, 1. Air flow channel, 2. Piston rod, 3. Piston joint, 4. Piston, 5. Gap, 6. Orifice, 7. Air bearing, 8. Cylinder barrel, 9. Flexible hose, 10. Piston inner cavity, 11, bearing air inlet, 12, pressure equalization chamber, 13, air pipe joint, 14, air pipe joint, 15, cylinder air inlet, 16, cylinder air inlet, 17, air bearing air inlet, 18, front end cover, 19, rear end cover, 20, fixed part, 21, moving part, 22, connecting rod, 23, ball hinge, 24, baffle plate, 25, rear buffer head, 26, elastic circlip, 27, Sealing ring, 28, buffer sealing ring.

Detailed ways

The present invention designs the piston part of the cylinder according to the principle of the air bearing on the basis of the ordinary cylinder, so that it forms a static pressure air bearing journal bearing with the inner wall of the cylinder barrel, and the contact part between the piston rod and the front end cover of the cylinder is the same The air bearing is used to connect, so that the non-contact connection between the movable part and the immovable part of the cylinder is realized, and the friction force is greatly reduced. The cylinder piston designed according to the principle of air bearings sprays compressed air from the inside of the piston to the tiny gap between the piston and the cylinder barrel through the orifices distributed in the circumferential direction of the piston, so that a high-pressure air film is formed in the gap Keep the piston out of contact with the cylinder barrel. When the piston is subjected to a certain radial force, such as a vertical downward force, the axis of the piston will deviate downward from the central axis of the cylinder barrel under the action of this force, and the small gap between the piston and the cylinder barrel will also According to the knowledge of fluid mechanics, the pressure in the lower part of the gap is higher than the pressure in the upper part so that the piston is subjected to an upward resultant force until the resultant force is balanced with the external force received by the piston, and the position of the piston tends to be stable . According to this principle, the cylinder has the ability to resist radial load. In order to prevent the piston from being stuck in the cylinder barrel when subjected to radial force, the present invention uses a ball hinge connection at the connection between the piston and the piston rod. The application of the ball joint allows a certain angle between the axis of the piston rod and the axis of the piston, which avoids the defect that the piston may be stuck in the cylinder barrel. The piston designed according to the principle of air bearing, its air supply is through the hollow piston rod, and the connection between the piston rod and the piston is passed through the hose to the inside of the piston.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, and the purpose and effect of the present invention will become more obvious.

FIG. 1 shows a three-dimensional perspective view of the frictionless cylinder comprising a fixed part 20 and a moving part 21 . Among them, the fixed part 20 includes the front end cover 18, the rear end cover 19, the cylinder barrel 8 and the air bearing 7 fixed on the front end cover 18, while the moving part 21 is composed of the piston 4, the piston joint 3 and the hollow piston rod 2. . The part where the fixed part 20 is in contact with the moving part 21 is at the piston 4 and the air bearing 7, and these two places are supported by the principle of air flotation, that is, the two surfaces that support each other are not in direct contact but pass through a layer air film.

Figure 2 and Figure 3 show the cross-sectional views of the moving part of the frictionless cylinder respectively, the piston joint 3 contains a ball joint, which can improve the piston stuck caused by poor neutrality when the cylinder stroke is large Case.

There is a small gap 5 between the piston 4 and the cylinder barrel 8, and the compressed gas is ejected from the orifice 6 in the piston inner cavity 10, and fills the entire gap 5, thus forming a high-pressure gas film in the gap 5, for friction-free support.

The piston 4 is connected with the hollow piston rod 2 through the piston joint 3, and the air pipe joint 13 on the piston 4 and the air pipe joint 14 on the piston rod 2 are connected with a flexible pipe 9 to form a hollow piston rod 2. The air flow channel, through which the compressed air is sent to the inner chamber 10 of the piston, realizes the air supply of the air floating piston.

Before starting the cylinder, ensure that the bearing inlet 11 and the air bearing inlet 17 are connected to the air source, and the air cylinder can be started after the air bearing starts to work.

In one example shown in Figures 1-5, the piston 4 has two rows of orifices 12, each having eight rows. As mentioned above, the cylinder is ready, and the air bearing inlet 11 and the air bearing inlet 17 are supplied with air, and the air cylinder can be started after the air bearing 7 and the piston 4 work normally. When the cylinder starts to work, because there is almost no friction, the stroke is relatively large. In order to avoid damage to the cylinder due to high-speed collision, an air buffer structure is also designed in the cylinder. When using the small hole throttling effect of the gas buffer structure, the pressure in the low-pressure chamber of the cylinder can rise rapidly, slowing down the forward speed of the piston. As the gas in the low-pressure chamber is gradually discharged from the small throttling hole to the outlet, the piston reaches the end of the stroke. Baffle plate 24 also contacts with cylinder front end cover 18, and piston 4 stops moving, and so far, cylinder has just completed the motion of a stroke.

The structure of the air floating piston 4 involved in the present invention can have various changes. Figures 6 to 7 show a sectional view and a sectional view of another example of the piston of the present invention. In this example the piston 4 has three rows of 12 orifices 12 each.

Although the invention has been described in detail based on specific examples, various changes and modifications exist within the scope of the invention as defined by the following claims.

The above-mentioned embodiments are used to illustrate the present invention, rather than to limit the present invention. Within the spirit of the present invention and the protection scope of the claims, any modification and change made to the present invention will fall into the protection scope of the present invention.

Claims (8)

1. A frictionless cylinder with an air bearing, the cylinder has a piston (4) and a piston rod (2) with an internal air flow channel (1), the two pass through a ball joint structure The piston joint (3) is connected, and there is a certain gap (5) between the piston (4) and the cylinder barrel (8), and the compressed air can be supplied to the gap (5) through the orifice (6). It is characterized in that , the front end of the piston rod (2) is supported by the air bearing (7), and the rear end is connected with the piston (4) through the piston connecting head (3). 2. The frictionless cylinder according to claim 1, characterized in that, the piston (4) is designed according to the principle of air bearing, and it is hollow inside, and there are orifices (6) distributed in the circumferential direction to make the piston The compressed air in the inner chamber (10) can flow to the gap (5) to form a high-pressure air film to support the piston (4). 3. The frictionless cylinder according to claim 2, characterized in that a certain number of orifices (6) are distributed along the circumference of the piston (4), and are evenly distributed. 4. The frictionless cylinder according to claim 3, characterized in that a pressure equalization chamber (12) is provided at the end of the orifice (6) distributed along the circumferential direction of the piston (4). 5. The frictionless cylinder according to claim 2, characterized in that the orifices (6) distributed along the circumferential direction of the piston (4) have several rows in the axial direction of the piston (4) and are distributed symmetrically. 6. The frictionless cylinder according to claim 1, characterized in that the piston joint (3) connecting the piston (4) and the piston rod (2) has a ball joint to ensure that the piston (4) and the piston rod (2) There may be some eccentricity. 7 . The frictionless cylinder according to claim 1 , characterized in that the piston rod ( 2 ) is hollow, and the air flow channel ( 1 ) inside it communicates with the piston cavity ( 10 ) through a hose ( 9 ). 8. The frictionless cylinder according to claim 1, characterized in that the compressed air enters from the bearing inlet (11) and enters the piston cavity (10) through the airflow channel (1) and the hose (9) , to achieve air supply.

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