AU673957B2 - Pivoted piston for radial cylinder machine - Google Patents

Description

I- -I I WO 95/08696 PCT/AU94/00569 1 PIVOTED PISTON FOR RADIAL CYLINDER MACHINE Technical Field The present invention relates to rotary machines and more particularly to piston arrangements for a rotary machine.

Background Art The contents of International patent applications PCT/AU89/00275; PCT/AU91/00224; and PCT/AU94/00529 are incorporated herein by reference.

Disclosure of Invention The piston arrangement as shown in International patent application No PCT/AU94/00529 is varied by the present invention whereby each piston is mounted on an arm and which arm is pivotally mounted about a pivot axis substantially orthogonal to the axis of the cylinder, said axis being spaced from the path of movement of the piston such that motion of the piston between its bottom dead centre and top dead centre closely approximates linear motion as would be understood within tolerances associated with piston-in-cylinder motion.

In one embodiment the present invention provides that each piston is pivotally mounted to one end of an arm and which arm is pivotally mounted at its other end at a location which is fixed relative to the cylinder in which the piston travels, said location being sufficiently remote from the axis of the path of movement of the piston such that motion of the piston pivot, as the piston moves between its bottom dead centre and top dead centre, closely approximates linear motion as would be understood within tolerances associated with piston-in-cylinder motion.

As discussed in International patent application No PCT/AU94/00529 the arrangement employing lobed shafts as depicted in Figs. 6, 7 and 9 thereof enables the piston stroke to be, say, 6mm or less and where the bore of the

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WO 95/08696 PCT/AU94/00569 2 cylinder is, say, up to 50ru-. As the stroke of such a piston is relatively small compared with conventional piston-in-cylinder arrangements it lends itself to a pivoting of that piston via an arm projecting laterally of the cylinder at a relatively small distance so that the 6mm of stroke can very closely approximate linear motion of the piston within the cylinder.

A construction having such a short stroke can considerably lower the radial dimensions of the rotary machine and with the pivotal arm of each piston in accord with the invention providing an additional stabilizing means for each piston.

It is contemplated that the piston stroke can be even further reduced while employing an arrangement in accord with the present invention so that where, say, the stroke of the piston is reduced to 3mm the path of travel of the piston will even more closely approximate linear motion within its cylinder for a constant length of pivotal arm.

By increasing the distance between pivot locations of the arm in an embodiment where the arm is pivoted at both ends, the path of travel of the piston will again more closely approximate linear motion within its cylinder.

Typically, for an embodiment in accord with the present invention having a pivot arm with 50mm between pivot centres mounted at the centreline of a piston having a 50mm bore and 6mm stroke aith the pivot arm orthogonal to the axis of the piston at bottom dead centre there is an out of centreline movement of the piston pivot of about 0.4mm.

Where the pivot arm is orthogonal to the axis of the piston when the piston is at the mid point of its stroke, the out of line movement of the piston pivot over each stroke will be only about 0.2mm. The result of embodiments of the invention as discussed will be that tiit motion applied to a piston will be minimal.

1 WO 95/08696 PCT/AU94/O0569 3 Brief Description of Drawings The present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic arrangement of the relevant parts of a rotary machine of Fig. 9 of International patent application No PCT/AU94/00529 incorporating a piston arrangement in accord with a first embodiment of the present invention showing a piston at bottom dead centre; Fig. 2 is a schematic arrangement similar to Fig. 1 but showing the piston at top dead centre; Fig. 3 is a schematic arrangement of the relevant parts of a rotary machine of Fig. 9 of International patent application No PCT/AU94/00529 incorporating a piston arrangement in accord with a second embodiment of the present invention showing a piston at bottom dead centre; and Fig. 4 is a schematic arrangement similar to Fig. 3 but showing the piston at top dead centre.

Best Modes Referring now to the drawings wherein Figs. 1-4 show part of an array of inter-fitting lobes 10 on separate lobed shafts rotatably mounted with their axes on a common circle.

As shown in Figs. 1 and 2, only a single piston 11 and its associated pivoting arm 12 are depicted for reasons of clarity. The piston 11 as shown in Fig. 1 is fitted within a cylinder 13 of an engine having a spark plug 14 mounted therein. The lobes 10 on the lobed shafts directly contact the underside 15 of the piston 11 with a progressive transition from one lobe to the next as the lobed shafts rotate anticlockwise about their respective axes and the shafts move in a circular path indicated by arrow 17 so that piston 11 moves between bottom dead WO 95/08696 PCTIAU94/O0569 4 centre in Fig. 1 and top dead centre in Fig. 2 while arm 12 pivots about axis 16.

As shown in Figs. 3 and 4, only a single piston 11 and its associated arm 12 are depicted' for reasons of clarity. The piston 11 as shown in Fig. 1 is fitted within a cylinder 13 of an engine having a spark plug 14 mounted therein. The lobes 10 on the lobed shafts directly contact a hard steel pad 15 mounted to the underside of piston 11 with there'being a progressive transition from one lobe 10 on a shaft to another lobe on the next shaft as the lobed shafts rotate clockwise about their respective axes and the shafts move in an anticlockwise circular path indicated by arrow 17 so that piston 11 moves between bottom dead centre in Fig. 1 and top dead centre in Fig. 2 while arm 12 pivots about axes 16 and 18.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodimnents without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (4)

1. In a rotary machine having a piston moving in a cylinder wherein the piston is pivotally mounted to part of the machine which is stationary relative to the cylinder, said pivotal mounting comprising an arm extending substantially orthogonal to the axis of the piston and being fixedly connected to the piston, said pivotal mounting on part of the machine having an axis substantially orthogonal to both said piston and said arm and wherein motion of the piston in the cylinder is substantially linear as the piston moves between top dead centre and bottom dead centre and wherein said arm does not function as part of a force transmitting system between said piston and an output or input to said machine.

2. In a rotary machine as claimed in claim 1 wherein the arm is fixedly pivotally connected to the piston.

3. In a rotary macnine as claimed in claim 1 or 2 wherein the stroke of the piston is 6mm or less.

4. In a rotary machine as claimed in claim 1 or 2 wherein the stroke of the piston is 3mm or less. A rotary machine comprising a piston in cylinder configuration substantially as hereinbefore described with reference to the Figs. 1 and 2 or 3 and 4 of the accompanying drawings. #AMENDED SHEET /V7- 05 JPENA