Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
1999-02-02
2001-07-31
Rosenburg, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888043
Reexamination Certificate
active
06266878
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to a variable displacement compressor piston, and, more particularly, to a variable displacement compressor piston having a hollow piston body axially aligned and integral with an actuator rod.
Variable displacement compressor pistons are used in a variety of applications including, for example, compressors used in automobile air conditioning systems. One method of producing such a piston involves forging a solid piston body with an accompanying integral actuator arm. A piston ring is added to the solid piston body to maintain sufficient air compression as the piston slides in a bore in a reciprocal fashion during compressor operation. The two components of such a piston must be manufactured separately and be later assembled thereby increasing production time and cost. Further, the solid piston body has a relatively large mass which increases reciprocating inertia in the system, and thus, reduces efficiency of the piston.
Another method of producing a variable displacement piston involves manufacturing a hollow piston body, typically by extrusion, and welding the hollow piston body to an actuator arm, which is typically formed by forging. The outer surface of the hollow piston body is machined along its length such that a piston ring is not required to maintain sufficient air compression during piston strokes. However, two parts still must be manufactured and assembled. Further, the piston body and actuator arm require machining to produce an appropriate surface at the joint where the two parts are welded together. The machining operation requires that the piston body and the actuator arm be precisely aligned during welding which is difficult. Improper alignment, due to lack of straightness, concentricity, perpendicularity and runout can result in unusable pistons once the machining operation is performed.
Accordingly, there is a need for a process of producing variable displacement compressor pistons which can be machined with little or no possibility of rendering the pistons unusable due to the machining operations. Preferably, such a process would produce pistons having relatively little mass and requiring no piston rings. Further, to improve manufacturing efficiency and accordingly expense, the process should require fewer and/or more simplified manufacturing steps.
SUMMARY OF THE INVENTION
The present invention meets this need by providing a process for producing variable displacement compressor pistons more efficiently and wherein hollow piston bodies are integrally formed with associated actuator arms to ensure proper alignment of the bodies and rods and thereby substantially eliminate machining problems associated with prior art pistons. The process utilizes a two-axis press to first form a pair of actuator arms by working a blank of metallic material along a first axis between opposing members of a die assembly. With the die assembly still closed after formation of the actuator arms, a pair of hollow piston bodies are formed by extruding the remainder of the blank of metallic material along a second axis. The hollow piston bodies are axially aligned and integrally formed with respective ones of the actuator arms. A piston head is welded to the end of each hollow piston body which is then machined and the actuator arms are separated from each other. A pair of variable displacement compressor pistons having hollow piston bodies axially aligned and integrally formed with respective actuator arms are thus formed.
According to a first aspect of the present invention, a process for forming a piston having an integral actuator arm comprises providing a blank of metallic material. The blank of metallic material is worked along a first axis so as to form at least one actuator arm. The blank of metallic material is also worked along a second axis so as to form at least one hollow piston body axially aligned with and integrally formed with the one actuator arm.
The step of working the blank of metallic material along a first axis so as to form at least one actuator arm may comprise the step of working the blank of metallic material along the first axis so as to form interconnected first and second actuator arms while the step of working the blank of metallic material along a second axis so as to form at least one hollow piston body axially aligned with and integrally formed with the at least one actuator arm may comprise the step of working the blank of metallic material along the second axis so as to form a first hollow piston body axially aligned with and integrally formed with the first actuator arm and a second hollow piston body axially aligned with and integrally formed with the second actuator arm. The process may further comprise coupling a first piston head to the first hollow piston body and coupling a second piston head to the second hollow piston body. The step of coupling a first piston head to the first hollow piston body may comprise the step of welding the first piston head to the first hollow piston body and the step of coupling a second piston head to the second hollow piston body may comprise the step of welding the second piston head to the second hollow piston body. The process may further comprise the step of separating the first and second interconnected actuator arms. The step of separating the first and second interconnected actuator arms may comprise the step of severing the blank of metallic material between the first and second interconnected actuator arms.
The step of working the blank of metallic material along a first axis so as to form at least one actuator arm may comprise positioning the blank of metallic material in a first stationary portion of a split die assembly. A second portion of the split die assembly is positioned over the first portion of the split die assembly with the first and second portions of the split die assembly forming a cavity. A first portion of the cavity has a shape corresponding to the shape of the at least one actuator arm. Pressure is applied to the second portion of the split die assembly along the first axis thereby forcing the second portion of the split die assembly towards the first portion of the split die assembly and working the blank of metallic material between the first and second portions of the split die assembly.
The step of working the blank of metallic material along a second axis so as to form at least one hollow piston body axially aligned with and integrally formed with the at least one actuator arm may comprise inserting at least one punch through a second portion of the cavity of the split die assembly positioned substantially adjacent the first portion of the cavity and having a diameter corresponding to an outer diameter of the first hollow piston body. The punch has a diameter corresponding to an inner diameter of the hollow piston body. Pressure is applied with the punch along the second axis to the blank of metallic material thereby back extruding the hollow piston body over the punch. The step of inserting at least one punch through the second portion of the cavity of the split die assembly and applying pressure with the punch along the second axis to the metallic material are preferably carried out with the second portion of the split die assembly engaging the first portion of the split die assembly.
The step of providing a blank of metallic material may comprise providing a block of metallic material having first and second surfaces forming planes that are generally perpendicular to the first axis and third and fourth surfaces forming planes that are generally perpendicular to the second axis. A portion of the block of metallic material is removed from the first side along a central portion of the block of metallic material. The step of removing a portion of the block of metallic material along a central portion of the block of metallic from the first side of the block of metallic material may comprise the step of forming a plurality of notches thereby forming at least a pair of generally symmetrical ribs. Preferably, th
Durkin Robert John
Worthington Steven Lee
Amcast Industrial Corporation
Killworth, Gottman Hagan & Schaeff, L.L.P.
Rosenburg I Cuda
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