Piston or plunger and a method for making the same

Details Piston or plunger and a method for making the same Piston or plunger and a method for making the same

1999-12-06

2001-12-11

Look, Edward K. (Department: 3745)

Expansible chamber devices

Piston

Side wall portion includes peripheral axially extending...

C092S249000

Reexamination Certificate

active

06327963

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method of making a piston or plunger which comprises a piston body defining a central outer cylindrical surface part thereon with a maximum outer diameter and extending between first and second circular edges, and a sealing member made from a deformable material and being in tight engagement with said cylindrical surface part. Such pistons or plungers may co-operate with hydraulic or pneumatic cylinders or may form part of a kind of a piston pump. As an example, the piston or plunger of this type may be used in schock absorbers for cars or other vehicles.
1. Description of Prior Art
It is known to produce such pistons or plungers by applying a disc-shaped angular sealing member blank to the piston body and by deforming the blank into a tubular sealing member being in close contact with the outer surface of the piston body. The sealing member blank is usually applied to the piston body by means of a female mandrel having an inner diameter slightly exceeding the maximum outer diameter of the peripheral outer surface of the piston body, and the tubular sealing member is positioned on the piston body by having the trailing edge of the sealing member blank being deformed, received in an annular channel or groove formed in the peripheral outer surface of the piston body. The leading edge of the tubular sealing member extends radially from the peripheral outer surface of the piston body and defines a sealing lip.
2. General Description of the Invention
The present invention provides a method of producing a piston or plunger of the above type having a sealing lip at opposite ends of the sealing member. Thus, the present invention provides a method comprising forming the piston body, forming peripherally extending, axially spaced grooves or depressions in the central cylindrical surface part of the piston body, passing and annular sealing member blank with an inner diameter being substantially smaller than the maximum diameter of the central outer cylindrical surface part around a first end of said piston body and moving it towards said first circular edge, and deforming the sealing member blank into tight engagement with the central outer cylindrical surface part and into the grooves or depressions formed therein so as to form a tubular sealing member extending axially along said central outer surface part and having opposite first and second ends extending beyond said first and second circular edges, respectively, whereby said opposite end portions of the tubular sealing member may function as sealing lips.
The piston body may have end portions extending from the central outer cylindrical surface part, and these end portions may have an outer diameter being substantially the same as that of the central cylindrical surface part. In the preferred embodiment, however, the piston body has stepped configuration with opposite end portions extending from said central outer cylindrical surface part, and the outer diameter of each of the end portions are then smaller than the diameter of the central outer cylindrical surface part so as to define said first and second edges there between. It is important that the tubular sealing member is positioned correctly in relation to the piston body. This may, for example, be obtained by having the said first end or trailing end of the sealing member temporarily received or located in an annular groove formed in the outer peripheral surface of the piston body axially spaced from the adjacent first end. This means, that such groove may be defined in an end portion of the piston body which may have a slightly smaller maximum outer diameter than the central cylindrical surface part.
The annular grooves or depressions formed in the central outer peripheral outer surface part of the piston body receives sealing member material therein when the sealing member blank is being deformed whereby an interlocking engagement between the sealing member and the piston body is obtained. It has been found that the formation of the first end of the tubular sealing member into a sealing lip is facilitated when the grooves or depressions in the central outer peripheral surface of the piston body are such that a first axial spacing of said first circular edge from the adjacent peripherally extending groove or depression in the central outer peripheral surface part of the piston body substantially exceeds a second axial spacing of the second circular edge of the piston body from the adjacent groove or depression in the central part. Usually the said first axial spacing should exceed 3 mm and, preferably, the first axial spacing is at least twice the second axial space.
The annular sealing member blank may, for example, be a disk or tube, or it may have any other suitable form, such as a strip or band or a piece of sheet material, which—in an annular shape—is applied to the piston body. When applying the sealing member blank to the piston body by plastic deformation of the sealing member blank the piston body and/or the sealing member blank may be heated to a temperature, usually in the range of 20-100° C. Furthermore, when the sealing member blank has been transformed into a tubular sealing member, the piston or plunger thus produced may be exposed to a heat treatment so as to calibrate the effective outer diameter of the piston or plunger and so as to cause at least one of the opposite ends of the tubular sealing member to move radially outwardly to form said sealing lips. Doing the heat treatment last mentioned the piston or plunger may be heated to a temperature within the range 150-260° C. The annular sealing member blank may be substantially flat and may be made from sheet material, for example by punching. Preferably, however, the sealing member blank is made by slicing a tubular member.
The sealing member blank may be applied to the piston body in any suitable manner. Preferably, however, the sealing member blank is passed on to the piston body via a tapered or frusto-conical member having its wide end positioned in abutting engagement with one end of the piston body. Thereafter, the sealing member blank may be exposed to radially inwardly directed forces so as to deform the blank into engagement with the central outer peripheral surface part of the piston body. In the preferred embodiment the sealing member blank is deformed by means of a compression tool having an opening defined therein with a diameter exceeding the maximum outer diameter of the central outer cylindrical surface part of the piston body, and the piston body with the sealing member blank arranged thereon may then be moved axially in relation to the compression tool through the opening thereof so as to deform the sealing member blank into the grooves or depressions of the piston body.
The present invention further provides a piston or plunger comprising a piston body defining an outer cylindrical surface part thereon extending between first and second axially spaced circular edges of the piston body, peripherally extending, mutually axially spaced grooves or depressions being formed in the outer cylindrical surface, and an annular sealing member made from a deformable material being deformed into tight engagement with said peripheral surface part, the sealing member having opposite first and second ends extending beyond said first and second circular edges respectively, of the piston body, so as to define opposite end portions of the tubular sealing member functioning as sealing lips.
According to a further aspect the present invention provides a piston body for use in a piston or plunger of the type described above, said piston body defining an outer cylindrical surface part thereon extending between first and second axially spaced circular edges of the piston body, peripherally extending, mutually axially spaced grooves or depressions being formed in the outer cylindrical surface for retaining thereon an annular sealing member made from a deformable material, said grooves or depressions in the outer peripheral surface part of the piston body

Affiliated with

Also associated with

Rating

Piston or plunger and a method for making the same does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Piston or plunger and a method for making the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Piston or plunger and a method for making the same will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2590500