Stock material or miscellaneous articles – All metal or with adjacent metals – Intermediate article
Reexamination Certificate
2000-05-30
2002-05-28
Zimmerman, John J. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Intermediate article
C428S577000, C428S583000
Reexamination Certificate
active
06395404
ABSTRACT:
This application claims priority under 35 U.S.C. §119 to Japanese patent application no. 11-152239 filed May 31, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing a blank used for manufacturing a single-headed piston, and more particularly to techniques for reducing the weight of the blank.
2. Discussion of the Related Art
A single-headed piston is used in a swash plate type compressor, as described in JP-A-9-256952, for example. The single-headed piston disclosed in this publication includes a head portion, and a neck portion formed integrally with the head portion. The head portion is axially movably fitted in a cylinder bore formed in a housing of the compressor, while the neck portion engages the opposite surfaces of a swash plate of the compressor through a pair of shoes such that the swash plate is movable relative to the neck portion, so that the single-headed piston is reciprocated by rotation of the swash plate to effect suction and compression of a gas.
The publication identified above proposes a method of producing two single-headed pistons from one blank. The method includes steps of: forming by casing or forging a blank wherein two neck portions for the two single-headed pistons are integrally formed in series arrangement in the axial direction of the blank; machining the outer circumferential surfaces of head portions and the other portions of the blank; applying a coating to the outer surface of the starting blank; grinding the outer circumferential surfaces of the head portions; cutting the starting blank into two pieces, namely, the two single-headed pistons. In this method, the blank consists of two sections which correspond to the respective two single-headed pistons and whose neck portions are arranged in series connection with each other in the axial direction, so that the productivity of the blank per se is improved. In addition, the method permits easy and efficient machining, coating (e.g., forming a polytetrafluoroethylene film) and other operations to be performed on the blank, since these operations are performed simultaneously on the two sections of the blank for the respective two single-headed pistons. Further, the method permits easy and stable grinding operations on the outer circumferential surfaces of the two head portions, by a centerless grinder, since the blank has a sufficiently large distance between the two head portions.
JP-A-10-159725 proposes a method of producing a single-headed piston which uses a hollow head portion, for the purpose of reducing the weight of the piston. Described in detail, the head portion includes a cylindrical container portion which is closed at one of its opposite ends and open at the other end, and a closure member which closes the open end of the cylindrical container portion. The open end of the container portion is closed by first fitting the closure member in the opening of the container portion and then fixing the closure member in the opening by calking the edge of the open end. This single-headed piston, whose head portion is hollow, has a reduced weight. Although the piston consists of two members one of which includes the neck portion and the container portion and the other of which is the closure member, there is not a risk that the closure member is removed upon compression of the gas by the piston, since a force produced by compression of the gas acts on the closure member in a direction that causes the closure member onto the container portion. During reciprocation of the single-headed piston, an inertial force acts on the closure member in a direction that causes the closure member to be moved away from the container portion. However, there is not a risk that the closure member is removed from the container portion, since the mass of the closure member is small and the inertial force is accordingly small. The single-headed piston receives a side force from the swash plate during the reciprocation, in a direction perpendicular to the direction of reciprocation. But, a bending moment based on this side force is small at the position of the closure member, and therefore there is not a risk that the closure member is removed due to the bending moment.
However, the blank for the single-headed pistons used in the method disclosed in JP-A-9-256952 is heavy, and it is difficult to reduce the weight of each single-headed piston produced according to this method. On the other hand, the method disclosed in JP-A-10-159725 has a risk that the closure member is rotated relative to the cylindrical container portion during an operation to machine the outer circumferential surface of the blank after the closure member is fixed to the container portion by calking. JP-9-256952 teaches the provision of a holding portion on the closure member, as an example of chucking means for the blank, so that the blank is chucked at the holding portion for transmitting a torque to the blank for rotating the blank during the machining operation. However, the force by which the closure member is fixed to the container portion by calking is not sufficient to withstand the torque applied to the closure member, whereby the closure member may be rotated relative to the container portion, causing the blank to be damaged.
Although the methods described above apply to the compressors of swash plate type in which the neck portion of the piston engages the opposite surfaces of the swash plate through the shoes, problems similar to those described above may be encountered with respect to a method of producing a blank for the single-headed piston used in compressors other than the swash plate type, such as wave cam type compressors. The term “single-headed piston” used herein is collectively used to mean single-headed pistons used not only in the swash plate type compressors but also the other types of compressors. Accordingly, the term “neck portion” of the piston means a portion of the single-headed piston at which the piston engages a driving member or device.
SUMMARY OF THE INVENTION
The present invention was made in the light of the background prior art described above. It is a first object of the present invention to provide a method of producing a blank which permits easy manufacture of a hollow single-headed piston having a reduced weight. It is a second object to provide such a blank.
The first or second object indicated above may be achieved according to any one of the following forms or modes of the present invention, each of which is numbered like the appended claims and depends from the other form or forms, where appropriate, to indicate and clarify possible combinations of technical features of the present invention, for easier understanding of the invention. It is to be understood that the present invention is not limited to the technical features and their combinations described below. It is also to be understood that any technical feature described below in combination with other technical features may be a subject matter of the present invention, independently of those other technical features.
(1) A method of producing a blank for manufacturing a single-headed piston including a head portion and a neck portion which is formed integrally with the head portion, for engagement with a drive member, the method comprising the steps of: manufacturing a body member including a twin neck section and two cylindrical hollow head sections formed integrally with the twin neck section such that the two hollow head sections extend from opposite ends of the twin neck section, the twin neck section consisting of two portions which are mutually integrally formed in series with each other and which correspond to the neck portions of respective two single-headed pistons, each of the two hollow head sections being open at at least one of opposite ends thereof which is remote from the twin neck section; manufacturing two closing members each for closing an open end of a corresponding one of the two hollow head sections; and fixing each of the two closing members to the body memb
Fukushima Shigeo
Katayama Seiji
Kato Takayuki
Takamatsu Masato
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Woodcock & Washburn LLP
Zimmerman John J.
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