Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Producing multilayer work or article
Reexamination Certificate
2003-05-12
2004-08-03
McDowell, Suzanne E. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Producing multilayer work or article
Reexamination Certificate
active
06770237
ABSTRACT:
INCORPORATED BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-325455 filed on Oct. 25, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to techniques associated with a dust cover to be attached to a shock absorber used in a suspension mechanism of an automotive vehicle. More particularly, the present invention is concerned with a novel dust cover assembly that permits an easy and firmly attachment thereof to the shock absorber without looseness thereof, a method of producing the dust cover assembly, and a product equipped with the dust cover assembly.
2. Description of the Related Art
There is known a shock absorber used in a suspension system of an automotive vehicle, which is interposed between and fixed to a member on the side of a body of the vehicle and a member on the side of a wheel of the vehicle so as to damp or attenuate a vibrational load applied from the wheel to the body of the vehicle. The shock absorber includes a cylinder filled with a fluid and a piston rod reciprocally slidably received by the cylinder. In the known shock absorber, a tubular dust cover is employed in order to cover a fluid-tight sealing portion between the cylinder and the piston rod. The dust cover is disposed radially outwardly of the shock absorber so as to cover a substantially entire area of a part of the piston rod that is protruded from the cylinder.
In general, the tubular dust cover is mounted on the shock absorber. For instance, JP-U-57-1927 discloses a first example of known mounting structures in which the tubular dust cover is press-fitted at its upper axial open end portion on an outer circumferential surface of a bound stopper. Further, JP-A-8-261267 discloses a second example of known mounting structures in which a tubular dust cover made of a synthetic resin material is press-fitted at its upper axial open end portion on a fixing metal member which is fixed to a protruding end portion of the piston rod of the shock absorber.
However, the first example of the known mounting structures may give an adverse effect on the elastic property of the bound stopper, and may cause an disengagement of the dust cover from the bound stopper upon elastic deformation of the bound stopper. The second example of the known mounting structure does not ensure a firmly engagement between the dust cover made of a synthetic resin material and the rigid fixing metal member, so that the dust cover needs to be forcedly pressed on the fixing metal member by means of a snap ring or the like in order to prevent disengagement of the dust cover from the fixing metal member. This results in an increase of the number of required components and a resultant cumbersome manufacturing process. In addition, the dust cover fixed by the snap ring is likely to come loose or be disengaged from the fixing member, whereby the dust cover tends to contact or interfere with the other components, possibly causing wound or injury of the dust cover and/or other components and undesirable impact noise. In the second example of the known mounting structure, it has been proposed to employ a rubber dust cover in order to ensure the easy and firmly attachment of the dust cover to the fixing metal member. However, the rubber dust cover inevitably suffers from a problem of secular change of its property due to ozone contained in a surrounding atmosphere. This leads to a reduced elastic force of the dust cover and occurrence of ozone cracks in the rubber dust cover, possibly causing a disengagement of the dust cover from the fixing metal member. Therefore, the known mounting structures for mounting the dust cover on the shock absorber are still insufficient to ensure the ease and firmly attachment of the dust cover to the shock absorber.
SUMMARY OF THE INVENTION
It is therefore one object of this invention to provide a dust cover assembly having a dust cover made of a synthetic resin material, which permits an easy and firmly attachment of the dust cover to the shock absorber without looseness thereof.
It is another object of this invention to provide a method of producing such a dust cover assembly which permits easily and firmly attached of a dust cover to the shock absorber.
It is yet another object of this invention to provide a shock absorber equipped with such a dust cover assembly.
The above and/or other objects may be attained according to at least one of the following aspects of the invention. The following preferred forms of the respective aspects of the invention may be adopted at any possible optional combinations. It is to be understood that the present invention is not limited to the following forms or combinations of these forms, but may otherwise be recognized based on the thought of the present invention that described in the whole specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
According to one aspect of the invention, it is provided a method of producing a dust cover assembly having a tubular dust cover disposed radially outwardly of a shock absorber for covering a protruding part of a piston rod of the shock absorber, said method comprising the steps of: (a) preparing a fixing member including a mounting bore to which a protruding end portion of the piston rod is inserted and fixed, and an engaging portion formed in an outer circumferential surface thereof and having an undercut shape in an axial direction thereof; (b) preparing a tubular parison having a large diameter portion at one of axially opposite end portion thereof; (c) positioning the parison with respect to the fixing member such that the large diameter portion of the parison is disposed radially outwardly of the outer circumferential surface of the fixing member including the engaging portion; (d) closing a blow mold so as to form a mold cavity around the parison and so as to hold the large diameter portion of the parison in close contact with the outer circumferential surface of the fixing member for molding the large diameter portion of the parison; and (e) executing a blow molding of the parison by introducing a compressed gas into the blow mold through the mounting bore of the fixing member, so as to form the tubular dust cover.
According to this method of the invention, when the blow molding is executed for producing the dust cover, one of the axially opposite end portions of the parison is pressed onto and held in close contact with or stick firmly to the outer circumferential surface of the fixing member including the engaging portion by the blow mold, so that one of axially opposite end portion of the dust cover is formed on and covers the outer circumferential surface of the fixing member. It is noted that the engaging portion of the fixing member has an undercut shape in the axial direction of the fixing member, in other words, the engaging portion is retracted radially inwardly from other portions of the fixing member which are located axially opposite sides of the engaging portion. The present method ensures that one of axially opposite end portions of the dust cover integrally formed with the other part of the dust cover is formed on and stick firmly to the outer circumferential surface of the radially retracted engaging portion of the fixing member, at the same time when the other part of the dust cover is produced by blow molding.
Accordingly, the present method makes it possible to fixedly mount the dust cover on the fixing member simultaneous with the blow molding of the dust cover, without requiring a special facilities or process of mounting the dust cover on the fixing member, resulting in an improved efficiency of assembling of the dust cover with the shock absorber. The present method is able to form the dust cover to be held in close contact with the outer circumferential surface of the fixing member, thus preventing looseness or disengagement of the dust co
McDowell Suzanne E.
Rossi & Associates
Tokai Rubber Industries Ltd.
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