Internal-combustion engines – Free piston – Single chamber; one piston
Reexamination Certificate
1999-08-06
2001-06-12
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Free piston
Single chamber; one piston
C123S0460SC, C123S193400
Reexamination Certificate
active
06244226
ABSTRACT:
TECHNICAL FIELD
The present invention relates to free piston internal combustion engines, and, more particularly, to piston and cylinder configurations within such engines.
BACKGROUND ART
Free piston internal combustion engines include one or more pistons which are reciprocally disposed within corresponding combustion cylinders. However, the pistons are not interconnected with each other through the use of a crankshaft. Rather, each piston is typically rigidly connected with a plunger rod which is used to provide some type of work output. For example, the plunger rod may be used to provide electrical power output by inducing an electrical current, or fluid power output such as pneumatic or hydraulic power output. In a free piston engine with a hydraulic output, the plunger is used to pump hydraulic fluid which can be used for a particular application. Typically, the housing which defines the combustion cylinder also defines a hydraulic cylinder in which the plunger is disposed and an intermediate compression cylinder between the combustion cylinder and the hydraulic cylinder. The combustion cylinder has the largest inside diameter; the compression cylinder has an inside diameter which is smaller than the combustion cylinder; and the hydraulic cylinder has an inside diameter which is still yet smaller than the compression cylinder. A compression head which is attached to and carried by the plunger at a location between the piston head and plunger head has an outside diameter which is just slightly smaller than the inside diameter of the compression cylinder. A high pressure hydraulic accumulator which is fluidly connected with the hydraulic cylinder is pressurized through the reciprocating movement of the plunger during operation of the free piston engine. An additional hydraulic accumulator is selectively interconnected with the area in the compression cylinder to exert a relatively high axial pressure against the compression head and thereby move the piston head toward the top dead center (TDC) position.
With conventional free piston engines, each piston is reciprocally disposed within a corresponding combustion cylinder, but is not rotated within the combustion cylinder. As the piston moves from a TDC position toward a bottom dead center (BDC) position, the piston head moves past and uncovers the exhaust outlet to allow the combustion products within the combustion chamber to flow therefrom. Since the piston head does not rotate within the combustion cylinder, the same portion of the piston head is continually disposed adjacent to the exhaust outlet. The portion of the piston head adjacent to the exhaust outlet has been found to have higher temperatures when compared with other portions of the piston head (e.g., when compared with the portion of the piston head adjacent to the combustion area inlet associated with the air scavenging channel). These thermal gradients and distortions of the piston head may cause thermal fatigue of the piston head over time, resulting in a decreased life expectancy of the piston head.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the invention, a free piston internal combustion engine includes a housing with a combustion cylinder, a second cylinder, and a fluid port disposed in communication with the second cylinder for transporting a pressurized fluid into the second cylinder. A piston within the housing is movable between a top dead center position and a bottom dead center position. The piston includes a piston head reciprocally disposed within the combustion cylinder, a second head reciprocally disposed within the second cylinder, and a plunger rod with a first end attached to the piston head and a second end attached to the second head. A flow impingement device is positioned adjacent to the plunger rod and is attached to the plunger rod and/or second head. The flow impingement device includes a plurality of vanes which cause the piston to rotate upon movement toward the top dead center position.
In another aspect of the invention, a free piston internal combustion engine includes a housing with a combustion cylinder and a second cylinder. A piston includes a piston head reciprocally disposed within the combustion cylinder; a second head reciprocally disposed within the second cylinder; a plunger rod with a first end attached to the piston head, a second end attached to the second head, and a longitudinal axis; and a plurality of radially extending vanes attached to the plunger rod and the second head. The radially extending vanes face toward the piston head and are disposed at an acute angle relative to the longitudinal axis.
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patent: 2995122 (1961-08-01), Randall
patent: 3044452 (1962-07-01), McCrory et al.
patent: 3606591 (1971-09-01), Fotma
patent: 3610217 (1971-10-01), Braun
patent: 4705460 (1987-11-01), Braun
patent: 5473893 (1995-12-01), Acten et al.
patent: 5482445 (1996-01-01), Acten et al.
patent: 6105541 (2000-08-01), Berlinger
patent: 0 065 171 (1982-11-01), None
patent: WO 00/50756 (2000-08-01), None
TU Dresden—publication date unknown—earliest 1993 Dresden University in Germany.
Berlinger Willibald G.
Raab Francis J.
Sloma John M.
Benton Jason
Caterpillar Inc.
McMahon Marguerite
Taylor & Aust P.C.
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