Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Patent
1984-09-13
1986-06-24
Staab, Lawrence J.
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
74 44, F16H 2118
Patent
active
045961603
DESCRIPTION:
BRIEF SUMMARY
The crank mechanisms, which are usually used for transferring forces and movements between pistons in piston engines, such as combustion engines, compressors, etc., are of such a type that the pistons must necessarily be able to transfer substantial transversely directed forces to the walls of the engine cylinders. In certain piston engines this condition is not fulfilled and, therefore, the conventional drive mechanisms including a crank shaft and connecting rods cannot be used. This applies for example to the so-called Stirling and Vuilleumier engines in which it is not possible to use a lubricant for lubricating the inner surfaces of the cylinders. If conventional crank shaft mechanisms are used in connection with such engines it is therefore necessary to include complicated crosshead structures for taking up the transversely directed forces which would otherwise be transferred to the cylinder walls.
From the U.S. Pat. Nos. 1,039,492 and 4,138,897 it is known to insert a triangular connecting link between the cranked part of a shaft or an eccentric and connecting rods of pistons slidably arranged within two adjacent, parallel cylinders of a Stirling engine, whereby no substantial transversely directed forces are applied to the pistons of the engine. However, this known mechanism may only be used in a piston engine having parallel cylinders arranged side by side.
The mechanism according to the invention is of the above described type for transferring movements between first and second linearly displaceable bodies, such as pistons or displacers, and comprising a connecting member having first, second, and third pivots defining first, second and third vertices of a triangle, a rotary device, such as a crank or an eccentric, connected to the first pivot of the connecting member for rotating said first pivot about a fixed axis, the second pivot of the connecting member being connected to said first displaceable body.
The present invention provides a simple mechanism of the above type for transferring movement between a pair of linearly displaceable bodies or pistons without applying substantial transverse forces to these of bodies or pistons even when the pistons are slidably mounted in cylinders arranged in a non-parallel relationship.
The mechanism according to the invention is characterised in further comprising a lever having a fixed fulcrum and having a first arm connected to the third pivot of the connecting member and a second arm pivotally connected to said second, linearly displaceable body.
The cylinders in which the moveable bodies or pistons are mounted may then be arranged so that the axes of the cylinders define a desired angle therebetween, provided that a corresponding angle is defined between the arms of the lever. Furthermore, a desired ratio between the strokes of the two moveable bodies or pistons may be obtained if a similar ratio between the length of the lever arms is chosen. By a suitable dimensioning of the said triangle defined by the pivots of a connecting member it is possible to obtain a desired phase displacement of the movements of the displaceable bodies or pistons as well as desired stroke lengths of the pistons.
The length of the perpendicular of said triangle from the first vertex defined by said first pivot of the connecting member is preferably at least three times the length of the radius of the rotating movement of said first pivot. The movements of the second and third pivots of the connecting member by rotation of the crank or eccentric will then become approximately linear, which is desirable i.e. to avoid that transversely directed forces are applied to the first displaceable body or piston.
The triangle defined by the pivots of the connecting member is preferably an isosceles triangle, and the sides of equal length of the triangle may intersect each other at the first vertex defined by said first pivot. The second and third pivot of the connecting member will then move substantially linearly with substantially the same stroke length.
The mechanism is preferably dim
REFERENCES:
patent: 527356 (1894-10-01), Beaumont et al.
patent: 1039492 (1912-09-01), Courtwright et al.
patent: 1597080 (1926-08-01), Lewis
patent: 1612917 (1927-01-01), Grimes
patent: 1673280 (1928-06-01), Evans
patent: 1793975 (1931-02-01), St. Clair
patent: 1956922 (1934-05-01), Ingram
patent: 2590662 (1952-03-01), Van Weenen
patent: 4138897 (1979-02-01), Ross
Andersen Niels E.
Carlsen Henrik
AC Energi ApS
Staab Lawrence J.
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