DUST BOOT

Abstract

A bellows (2) of a dust boot (1, 30) having large diameter parts (3) and small diameter parts (4) disposed alternately covers a piston rod (R) projecting from a cylinder (C). A bump stopper (B) fixed to the cylinder (C) projects into the bellows (2) as a projecting portion. The bellows (2) comprises a first section (M) which passes a projecting end of the projecting portion according to the elongation and contraction of the piston rod (R) and a second section (L) located therebelow. By making the small diameter parts in the second section (L) have a smaller inner diameter than the small diameter part located at a boundary between the first section (M) and the second section (L), the bellows (2) can be made slim without interfering with the bump stopper (B).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a hydraulic shock absorber in a maximum elongated position, provided with a dust boot according to this invention.

FIG. 2 is an enlarged view of a projecting end of a piston rod of the hydraulic shock absorber.

FIG. 3 is an enlarged view of the dust boot in FIG. 1.

FIG. 4 is a longitudinal sectional view of essential parts of a hydraulic shock absorber in a maximum elongated position, provided with a dust boot according to a further embodiment of this invention.

Claims

1. A dust boot covering at least a part of a piston rod projecting from a cylinder or a cylinder fixed member, comprising: a cylindrical bellows comprising large diameter parts and small diameter parts which are disposed alternately;wherein,an end of the bellows is supported by a support on the outside of the cylinder;the cylinder or the cylinder fixed member comprises a projecting portion which projects into the bellows;the bellows is divided into several sections including a first section which passes a projecting end of the projecting portion when the piston rod elongates and contracts with respect to the cylinder, and a second section located between the first section and the support; andthe inner diameter of small diameter parts in the second section is set to be smaller than the inner diameter of a small diameter part located at a boundary between the first section and the second section.

2. The dust boot as defined in claim 1, wherein the inner diameter of the small diameter parts in the second section gradually decreases towards the support.

3. The dust boot as defined in claim 1, wherein the inner diameter of the small diameter parts in the first section gradually increases as a distance from the second section along the piston rod increases.

4. The dust boot as defined in claim 3, wherein an outer diameter of the large diameter parts in the first section is constant.

5. The dust boot as defined in claim 1, wherein a large diameter part and a small diameter part adjacent thereto are connected by a tapered face, and the tapered faces in the first section are greater than the tapered faces in the other sections.

6. The dust boot as defined in claim 1, wherein the bellows comprises a cylindrical part with a bottom which is continuous with another end of the bellows, and the piston rod penetrates the bottom of the cylindrical part.

7. The dust boot as defined in claim 6, wherein the dust boot is disposed inside a coil spring which is disposed between the cylinder and the piston rod, and the cylindrical part is fixed to the piston rod together with a spring seat supporting the coil spring on the piston rod.

8. The dust boot as defined in claim 1, wherein the dust boot is disposed inside a coil spring which is disposed between the cylinder and the piston rod, and another end of the bellows is supported by a spring seat which supports the coil spring on the piston rod.

9. The dust boot as defined in claim 7, wherein the coil spring is supported by a second spring seat provided on the outer circumference of the cylinder and comprises a decreased diameter part on the outside of the cylinder which decreases in diameter towards the second spring seat, and the outer diameter of the large diameter parts of the bellows in the second section is smaller than the outer diameter of the large diameter parts in the other sections.

10. The dust boot as defined in claim 1, wherein the cylinder fixed member comprises a bump stopper which is fixed to an end of the cylinder and prevents the piston rod from contracting beyond a predetermined position by coming into contact with a rubber cushion which is fixed to the projecting end of the piston rod.