Piston engine
AssigneeU.S. Philips Corporation
InventorsMarc J. M. Wolfs, Andreas J. Garenfeld
Life of this patent
Estimating the term…
Abstract
A piston engine comprising a piston movable in a recriprocating manner in a cylinder, while during operation a wedge-shaped gap is present between piston and cylinder. The piston divides the cylinder into a first chamber and a second chamber, which communicate with each other through the gap. A stable central position of the piston is obtained by means of the wedge-shaped gap, which mainly determines a pressure difference between the first chamber and the second chamber. A particular application of the piston engine is a cryo-cooler, by means of which, for example, processors of computers are cooled.
Claims21
An apparatus comprising a piston which is reciprocable in a gas-filled cylinder and divides the cylinder into a first chamber and a second chamber, between which chambers a gas pressure difference exists during piston reciprocation, the outer wall of the piston and an inner wall of the cylinder defining a gap therebetween which gap communicates the first chamber with the second chamber and is different in size in annular cross-sections transverse to the direction of movement of the piston, characterized in that:
- The gap is concave and on either side of a reversing plane transverse to the direction of movement of the piston the gap is tapered such that a cross-section of the gap located near a first boundary plane of the gap and a cross-section of the gap located near a second boundary plane of the gap have a smaller surface area than a cross-section of the gap near the reversing plane of the gap, and the pressure difference across the gap between the first and the second boundary plane is substantially equal to the pressure difference between the first and second chambers, the tapered form of the gap extending on either side thereof beyond the boundary planes of the gap over a distance at least equal to half a piston stroke in the central position of the piston.
An apparatus comprising:
- a cylinder having a cylinder wall defining a cylinder axis and having a working fluid;
- a free piston having an outer wall and reciprocable in said cylinder, a fluid pressure difference existing across said piston during piston reciprocation, said piston having a clearance fit with said cylinder forming a leakage path between said piston outer wall and said cylinder wall allowing leakage of working fluid across the piston during piston reciprocation, the fluid pressure difference causing an inequality in the mass flow of the working fluid in opposite directions per reciprocation cycle causing the position equilibrium piston to shift from a fixed cylinder position, the improvement comprising:
- the geometry of the piston outer wall and cylinder inner wall comprising means for causing a leakage of working fluid across the piston in the direction of movement of the position equilibrium piston for equalizing the mass flow of the working fluid and restoring the position equilibrium piston to the fixed cylinder position during each reciprocation cycle.
Dependencies are inferred from the claim text.