Internal-combustion engines – Transmission mechanism from piston – Crankshaft and connecting rod
Reexamination Certificate
1998-07-28
2001-04-03
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Transmission mechanism from piston
Crankshaft and connecting rod
C123S197200
Reexamination Certificate
active
06209510
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention relates to an assembly of a multipart piston and a connecting rod adapted for use with the piston. More particularly, the invention relates to a multipart piston including a bearing component mounted within the piston body and a connecting rod configured to contact and movably associate with the bearing component. The piston and connecting rod assembly of the present invention may be used in, for example, an internal combustion engine such as a piston aircraft engine, and also may be applied in any other suitable application incorporating a reciprocating or otherwise movable piston element.
BACKGROUND OF THE INVENTION
Internal combustion engines have incorporated pistons of two general types: single-piece pistons and pistons having multiple parts. Known multiple-part pistons have included a piston head and a separate piston skirt that are connected together by a connecting element to form the piston portion of a piston and connecting rod assembly. The different parts of the piston may be constructed of differing materials and, for example, the piston head may be fabricated from materials that withstand the high temperatures and pressures encountered in the combustion region of the cylinder and in the vicinity of the piston rings, while the piston skirt may be constructed of lighter weight materials so as to reduce engine weight. In both one-piece and multiple-part pistons, a connecting rod is connected to the piston through a bearing member, commonly provided as an integral element of the piston head, so that the connecting rod may pivot relative to the piston as the piston reciprocates within the cylinder.
An example of the known piston constructions is provided in U.S. Pat. No. 4,377,967, which discloses a two-piece piston assembly having an upper part or piston head made of cast iron, malleable iron or similar material and a lower part or piston skirt made of an aluminum-containing metal. The piston head and piston skirt are secured in desired relative positions and are movably connected to a connecting rod by a piston pin. More specifically, the piston head includes downwardly extending pedestals having bosses at their lower portions defining holes for receiving the piston pin. Similarly, the piston skirt includes holes that register with the pedestal bosses and also receive the piston pin coaxially with the holes of the piston head to thereby connect the piston head, piston skirt, and the connecting rod.
U.S. Pat. No. 5,701,802 discloses a multiple-part piston having separate piston head and piston skirt components and wherein each of the piston head and piston skirt integrally incorporate a bearing block having a bearing surface. A coupling device is provided for interconnecting the piston head and the piston skirt and for interconnecting the individual integral bearing blocks of those two components. The two bearing blocks are configured so that when interconnected they form a bearing for rotatably coupling a connecting rod to the piston.
U.S. Pat. No. 5,713,262 provides a piston including a piston head having a pair of pin bosses extending downward from the piston head. Two identically configured piston skirts extend from the piston bead and are arranged symmetrically about the bosses. Side walls are provided around the bosses and connect the bosses to the piston skirts. A piston pin is provided in the two bosses and pivotally couples a connecting rod to the piston.
Manufacturing the piston head to include elements of the bearing for coupling the connecting rod to the piston body complicates the manufacturing process and increases the associated costs. Moreover, integrating bearing elements for the connecting rod into the piston head allows for the ready conduction of heat to the bearing elements from regions of the piston head that encounter the temperatures of combustion and that experience frictional heat generated by moving contact between the piston rings and the cylinder. The heat conduction increases the temperature experienced at the piston/connecting rod interface (bearing) and may adversely affect the wear properties at the bearing. The integration of connecting rod bearing elements into the piston head also may complicate the assembly of the piston to the connecting rod and, as seen in existing piston designs, may require that the piston skirt have a complicated, non-uniform construction and, for example, include voids therethrough so that the piston pin may be inserted into the piston body to interconnect the connecting rod and the piston body.
Thus, based upon at least the foregoing deficiencies in existing piston and connecting rod assembly designs, the need exists for an improved design for a piston and connecting rod assembly that reduces the complexity and costs associated with manufacturing the assembly, reduces piston/connecting rod bearing temperatures so as to enhance bearing life, and reduces the weight of the final assembly.
SUMMARY OF THE INVENTION
The present invention addresses the foregoing needs, among others, by providing an improved piston and connecting rod assembly including: a piston crown; a piston skirt that is a component separate from the piston crown; a connecting rod having first and second ends and including a first bearing surface on the first end; and a bearing insert that is a component separate from the piston crown, the piston skirt, and the connecting rod. The piston crown and piston skirt are connected together to provide a piston body, and the bearing insert is fixedly disposed within the piston body and is contacted by the connecting rod's first bearing surface, thereby providing an articulating joint, or in other words, a movable association, between the piston body and the connecting rod.
The piston crown and piston skirt may be threadedly connected together by, for example, providing the piston crown with a threaded annular inner surface region and the piston skirt with a corresponding annular outer surface region. However, any other suitable means of connecting the piston skirt and piston crown together also may be used.
The piston crown includes an inner surface and the bearing insert is disposed intermediate the inner surface of the piston crown and the first bearing surface. (As used herein, a first element is “intermediate” second and third elements even if one or more other elements are interposed between the first element and the second and/or third element.) The first bearing surface of the connecting rod may contact the bearing insert on a second bearing surface which is defined by a bearing portion of the bearing insert, and at least a region of the first bearing surface at least partially conforms to and articulates with at least a region of the second bearing surface. To provide for the conforming regions of the first and second bearing surfaces, one of the first and second bearing surfaces may be, for example, a concave surface and the other may be a convex surface, and at least a region of the concave surface conforms to and articulates with the convex surface. More particularly, such concave and convex bearing surfaces may be shaped as, for example, concave and convex surfaces defined by cylindrical or spherical radii of curvature or may be shaped as concave and convex regions of a barrel-shaped surface.
In one particular arrangement, the bearing portion of the bearing insert has a cylindrical perimeter, the bearing insert's second bearing surface is a concave surface defined by a spherical radius of curvature, and the first bearing surface of the connecting rod is a convex surface defined by a spherical radius of curvature that is generally identical to the spherical radius of curvature defining the insert's second bearing surface. At least a region of the concave spherical second bearing surface of the bearing insert contacts and articulates with at least a region of the convex spherical first bearing surface of the connecting rod.
The bearing inse
Brogdon James William
Chatten John K.
Gill David Keith
Benton Jason
Kirkpatrick & Lockhart LLP
McMahon Marguerite
Teledyne Technologies Incorporated
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