Sealing Device for Hydraulically or Pneumatically Operated Equipment

This invention relates to a boot which prevents muddy water, dust, etc. from outside from entering a sliding part between a piston and a cylinder in a hydraulically or pneumatically operated equipment. It is the principal object of this invention to provide a boot of a shape which ensures an improved sealing effect.

FIG. 1 is a sectional view illustrating a part of a hydraulically or pneumatically operated equipment with a conventional boot mounted thereon.

FIG. 2 is a sectional view illustrating a boot prepared in accordance with this invention as being in a mounted position and

FIG. 3 a sectional view illustrating the same boot of this invention as in a free, unmounted condition.

FIG. 4 is a sectional view illustrating a modification of the boot shown in FIG. 3. In these drawings, reference numberals indicates parts as shown below:

1: Hydraulically or pneumatically operated equipment

2: Cylinder body

3: Piston

4: Cylinder

5: Seal

6 AND 9: Boot

7: Circumferential groove

8: Resilient ring

6A AND 9A : Internal thick portion

6B AND 9B : External thick portion

6C AND 9C : Flexible portion

9D : Recess

9E AND 9F : Protrusion

In comparison with the boot prepared in accordance with this invention as illustrated in FIGS. 2, 3 and 4, the conventional boot which is represented by FIG. 1 is first described as follows:

In FIG. 1 which illustrates the conventional boot, a cylinder body 2 of a hydraulically or pneumatically operated equipment 1 is provided with cylinder 4 in which a piston 3 is fitted. A seal 5 is arranged to prevent a pressurized hydraulic oil or air from leaking. A boot 6 which is arranged to prevent muddy water etc. from entering a sliding part between the piston and the cylinder from outside is made of a resilient material and comprises an internal thick portion 6a, an external thick portion 6b and a flexible portion 6c with the flexible portion 6c being disposed to connect the thick portions 6a and 6b. The internal thick portion 6a receives stress in the direction of its circumference and is pressed tightly against the outer edge of the piston 3 to give a sufficient sealing effect. On the other hand, the external thick portion 6b is fitted in a circumferential groove 7 of a rectangular shape provided in the inner edge of the cylinder body 2 with stress applied by a resilient ring 8 to the external thick portion 6b from the inner circumference of it toward the circumference thereof. However, in the surface pressure distribution in the external thick portion 6b of the boot 6 at the bottom of the groove 7, the pressure is high only in the middle part which corresponds to the resilient ring 8 and is low at both ends. Furthermore, since the width of the groove 7 of the external thick portion 6b is somewhat less than that of the groove 7, there is almost no surface pressure at both sides of the external thick portion 6b. Thus, in the conventional boot 6, the external thick portion 6b is pressed only at the part which is pushed by the resilient ring 8. Therefore, the sealing effect attained with the conventional boot has been insufficient.

FIG. 2 illustrates a boot 9 which is prepared in accordance with this invention as being applied to an equipment while FIG. 3 illustrates it as in a free, unmounted condition.

In the peripheral part of an external thick portion 9b, there are provided a recess 9d in the direction of the width, the recess 9d forming an annularly continuous curve and forming either protrusions 9e and 9f on both sides of the external thick portion 9b or a protrusion on one side only. The width of the external thick portion 9b at the protrudent part is arranged to be greater than a groove 7 disposed in the body of the equipment to correspond to the external thick portion. As shown in FIG. 2, the recess 9d of the boot 9 is pushed by a resilient ring 8 against the bottom of the groove 7 of the body and is thus kept in close contact with the bottom with its recessed shape resiliently flattened out by the force of the ring 8. This ensures that the surface pressure at both edges of the recessed side of the external thick portion is greater than the conventional boot. In addition to that, the protrusions 9e and 9f also come into resilient contact with the sides of the groove 7 of the body 2 to ensure an enhanced sealing effect.

FIG. 4 illustrates a modification of the boot shown in FIG. 3. In this modification, in the external part thereof the protrudent side of the external thick portion 9b which is to be brought into contact with the side wall of the circumferential groove of the cylinder body is provided with a cutaway part 9g which is cut in the lower part of the side 9e either at a right angle to or at a smaller angle 9h in respect to the side 9e. This arrangement further enhances the sealing effect.