JPS6236962Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealing structure in a hydraulic cylinder, particularly to a sealing structure between a cylinder head and a piston rod.

Conventionally, as shown in FIG. 1A, this type of sealing structure in a hydraulic cylinder has been provided with an annular groove in the cylinder head 1, a buffer ring B consisting of a seal member and a slide ring, and a groove with a cross section of approximately As is well known, it includes a U-shaped gasket R and a wiper ring W.

However, oil leaking little by little from the buffer ring B may enter the intermediate portion sealed by the seal R, and the oil pressure within the intermediate portion may become higher than that on the system side, resulting in a so-called pressure accumulation phenomenon.

Furthermore, as shown in Figure 1B, as the reciprocating motion is repeated under high pressure, the fluid pressure in the space between the U-shaped packing 1' and the ring-shaped packing 5' gradually increases, and the high pressure side Even if the pressure is reduced, the fluid pressure between the U-shaped packing 1' and the ring-shaped packing 5' does not escape to the reduced pressure side A, so the high fluid pressure accumulated between the U-shaped packing 1' and the ring-shaped packing 5' Since the sealing device always slides while being pressed against the mating sliding surface 7', frictional resistance increases and significant wear occurs, shortening the life of the sealing device.

As shown in Fig. 2, the present invention particularly relates to the sealing structure of the buffer ring B, and
In a state where high pressure is applied, the seal member 7 and slide ring 8 are brought into close contact with the low pressure side 5 of the annular groove 6, and pressure transmission to the intermediate portion 4 is prevented.

Furthermore, as shown in FIG.
Due to the high pressure, the sealing member 7 and the slide ring 8 are pressed against the cylinder side 5' of the annular groove 6, but the sealing member 7 is provided with several protrusions 9 as shown in the fourth figure. As a result, the groove 11 is left on the cylinder side 5', and since the seal member 7 is provided with the groove 10, the pressure on the intermediate part 4 side is transmitted through the low pressure side 5, the groove 10, and the groove 11. The slide ring 8 is made of hard resin such as nylon to prevent it from extruding into the system side 3 due to high pressure. As shown in the fifth diagram, the unevenness due to machining is the groove 12.
, and is discharged to the system side 3 through a passage means consisting of a groove 10 provided on the outer periphery of the seal member 7, a groove 11 formed on the side surface, and a groove 12 formed on the side surface of the slide ring 8. There is.

In addition, in Figure 6, the slide ring 8 is placed on the system side 3.
The seal member 7 is made of a hard nylon or the like to prevent it from protruding, and a phenomenon occurs in which the contact angle portion 13 of the seal member 7 made of an elastic material such as rubber is torn off.

Furthermore, in FIGS. 7 and 8, the material forming the slide ring 8' is changed from nylon to a relatively flexible synthetic resin material such as Teflon (registered trademark), and both outer peripheral ends of the slide ring 8' are Chamfers 14 and 15 are formed on the edges to prevent the seal member 7 from peeling off due to protrusion.

Further, a flow groove 16 is provided on the system side 3, and a flow path for hydraulic pressure return is formed at the close contact portion between the slide ring 8 made of a flexible material such as Teflon and the cylinder side 5'.

Therefore, when the intermediate portion 4 becomes high pressure, the hydraulic pressure is released to the system side 3 via the low pressure side 5, the groove 10, the groove 11, and the circulation groove 16.

As described above, the present invention provides passage means for releasing the pressure in the intermediate portion 4 to the system side 3 on the side surface of the slide ring 8 and on the outer periphery and side surface of the seal member 7 mounted on the slide ring. Since the pressure on the intermediate part 4 side can be released to the system side 3 via the passage means provided in the slide ring 8 and the seal member 7, high fluid pressure is not applied to the seal and its sliding surface. The advantages of this are enormous, such as not only can the life of the seal be extended, but also the so-called pressure accumulation phenomenon can be eliminated.

[Brief explanation of the drawing]

Figures 1A and 1B are longitudinal sectional front views with a part cut away of a conventional hydraulic cylinder, and Figures 2 to 8 show embodiments of the present invention. Figure 2 shows the main parts of the cylinder head. Fig. 3 is an enlarged sectional view showing the operating state when the oil pressure outside the buffer ring increases, Fig. 4 is an enlarged plan view of the slide ring, and Fig. 5 shows the slide ring. Microscopically enlarged sectional view of the contact surface with the cylinder head,
FIG. 6 is a side view showing the peeled state of the seal member;
FIG. 7 is a plan view of the slide ring, and FIG. 8 is an enlarged sectional view of the main parts. DESCRIPTION OF SYMBOLS 1... Cylinder head, 2... Piston rod, 3... System side, 4... Middle part, 5... Low pressure side, 6... Annular groove, 7... Seal member, 8...
...Slide ring, 9...Protrusion, 10...Concave groove,
11...Groove, 12...Groove, 13...Contact angle part, B
...Buff ring, W...wiper ring.

Claims (1)

[Scope of utility model registration request] In a hydraulic cylinder in which a buffer ring consisting of a seal member and a slide ring is disposed on a packing and one of the packing via an intermediate portion, the side surface of the slide ring and the outer periphery and side surface of the seal member mounted on the slide ring. A sealing structure for a hydraulic cylinder, characterized in that a passage means is provided for releasing pressure in the intermediate portion to a system side.