GB2557946A

GB2557946A - Rotary engine

Info

Publication number: GB2557946A
Application number: GB1621647.5A
Authority: GB
Inventors: Pattakos Manousos; Pattakos John; Pattakos Efthimios; Pattakos Emmanouel
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-12-19
Filing date: 2016-12-19
Publication date: 2018-07-04
Also published as: GB201621647D0

Abstract

A rotary positive displacement machine and method of design, where the machine has a pair of relatively rotatable bodies 1,2 which have cooperating surfaces which define working chambers 7, and when during the rotation of the bodies the volume of the working chambers varies; with a groove on one body and a smooth working surface on the other, with a seal 5 mounted in the groove 3, and abutting, for at least part of a cycle, onto the smooth working surface, the smooth working surface comprising a pair of flat surfaces 4a & 4b which extend radially and a curved surface 4c which extends both radially and axially between the two flat surfaces. The curved surface may have a double curvature and may be 3D. The seal may be formed in a single piece, or two seal pieces may be used to form the seal for a single working chamber. The machine may be rotatably fixed to a frame, and rotate about fixed axes. The first body may be stationary and the second body rotate on an eccentric shaft mounted to the first body. Gear wheels may be used to synchronize the rotation of the two body parts.

Description

(71) Applicant(s):

Manousos Pattakos

Lampraki 406, Nikea Piraeus 18452, Greece

John Pattakos

Lampraki 406, Nikea Piraeus 18452, Greece

Efthimios Pattakos

Lampraki 406, Nikea Piraeus 18452, Greece

Emmanouel Pattakos

Lampraki 406, Nikea Piraeus 18452, Greece (72) Inventor(s):

Manousos Pattakos John Pattakos Efthimios Pattakos Emmanouel Pattakos (74) Agent and/or Address for Service:

Manousos Pattakos

Lampraki 406, Nikea Piraeus 18452, Greece (51) INT CL:

F01C 21/08 (2006.01) F01C 19/00 (2006.01) F04C 18/22 (2006.01) (56) Documents Cited:

EP 0310549 A DE 019708602 A

FR 002935022 A (58) Field of Search:

INT CL F01C, F02B, F04C Other: EPODOC, WPI (54) Title of the Invention: Rotary engine

Abstract Title: Rotary machine with double curved chamber walls (57) A rotary positive displacement machine and method of design, where the machine has a pair of relatively rotatable bodies 1,2 which have cooperating surfaces which define working chambers 7, and when during the rotation of the bodies the volume of the working chambers varies; with a groove on one body and a smooth working surface on the other, with a seal 5 mounted in the groove 3, and abutting, for at least part of a cycle, onto the smooth working surface, the smooth working surface comprising a pair of flat surfaces 4a & 4b which extend radially and a curved surface 4c which extends both radially and axially between the two flat surfaces. The curved surface may have a double curvature and may be 3D. The seal may be formed in a single piece, or two seal pieces may be used to form the seal for a single working chamber. The machine may be rotatably fixed to a frame, and rotate about fixed axes. The first body may be stationary and the second body rotate on an eccentric shaft mounted to the first body. Gear wheels may be used to synchronize the rotation of the two body parts.

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ROTARY ENGINE

BACKGROUND ART

This invention relates to rotary engines of the type including relatively rotatable inner and outer bodies having cooperating surfaces that during relative movement define variable volume chambers.

Closest prior art: the US3,064,880 (Wankel Felix et al) and the US8,523,546 (Shkolnik Nikolay et al) patents.

SUMMARY OF THE INVENTION

The abovementioned patents disclose sealing arrangements wherein several seals into grooves of the one body slide onto “working” surfaces cut on the other body of the rotary engine. Quote from the above US8,523,546 patent:

“Having very few moving parts it is not surprising that this simple design has attracted attention of many who attempted to design a rotary engine around it. The major problem that could be traced to all rotary engines, however, is difficulty in sealing the working fluid during the compression, combustion and expansion strokes of the engines. While theoretically most of the engines look feasible on paper, in practice, when machining tolerances and thermal expansion are taken into account and also when parts are starting to wear out, the sealing of working fluid is not possible without seals. The most famous version of gerotor-based engine and the only one used in production is the Wankel engine, in which 3-lobe rotor moves inside a 2-lobe housing, as shown in Fig. 1 (c). This engine was relatively successful for two main reasons. First, the outer rotor was not used to guide the inner rotor, but rather a pair of gears was used to synchronize the movement and rotation of the inner rotor with motion of the eccentric shaft. Second, the gap between the inner rotor and outer rotor, which is provided to allow for manufacturing tolerances, thermal expansion, and wear, was sealed by a grid work of seals, may be known as a “Wankel Grid”, consisting of face seals located on flat parts of the rotor and apex seals located within each apex of the rotor, and also “buttons” that connected both of these types of seals; all of these seals are located on the rotor, and therefore will move with the rotor. Together with rotor itself and the housing, in theory these seals completely encompassed the working fluid. Again, in practice, there are still gaps between the seals or seals and rotor and seals and housing, but they are relatively small and manageable and enable the engine to function. Having said this, it is well known that these engines have relatively low efficiency and high emissions and are unsuitable for compression ignition mode of operation due to:

1. Relatively high degree of leakage, despite the seal grid. For example, the bounching of fast moving apex seals, as well as holes into the engine to accommodate spark plug(s), contribute to leakage.”

End of quote.

However, as in the US3,064,880 patent of Wankel, similarly In the US8,523,546 patent (wherein: “a rotary engine has a cycloid rotor and a sealing grid including a face seal that rotates with the rotor, and including other seals that do not rotate with the rotor”), each “working chamber” is sealed by a set of eight (or more, depending on the version) seals: two side seals, two peak seals and four “button seals” (Fig 15(b), Fig 15(c)).

The main problem in the “gerotor” rotary engines of the prior art (like the one disclosed by Cooley in his US748,348 patent of 1903, or like the rotary engines of the closest prior US3,064,880 and US8,523,546 patents), is the leakage during the high pressure period of the cycle.

The poor sealing is mainly caused by the several gaps between a plurality of different sealing means (the “sealing grid”) arranged around each working chamber. For instance, in the arrangement shown in the Fig 8(a) of the US8,523,546 patent, there are eight such gaps between the seals. And because some seals are “stationary” (they are on the immovable casing) while some others are “movable” (they are on the moving part), and because the motion of the moving part is far from being geometrically perfect (there is, inevitably, a backlash / play in the synchronizing gearing, there is also a “play” in the bearings between the cooperating parts, there is also a deflection of the eccentric shaft due to the high pressure load and to inertia load, etc), the overall leakage cannot help being problematic.

The need for a “sealing grid” (which inevitably creates several “gaps” through which compressed fluid leaks) derives from the abrupt (edged at a 90 degrees corner) connection of the two side flat surfaces (these flat surfaces are parallel to each other) with a cylindrical surface, with the orthogonal projection of the cylindrical surface on a plane parallel to the flat surfaces being a curved line occupying no area on the projection plane.

Orthogonal projection is a parallel projection where all the projection lines are orthogonal to the projection plane.

The cylindrical surface is created by a generatrix straight line moving parallel to itself.

The sealing in the “gerotor” rotary engines has been proved in practice by far worse than that of the reciprocating piston engines.

Several modern 2-stroke reciprocating piston engines (like the Rotax E-TEC 850) use just one seal (i.e. one only piston ring) per combustion chamber. Also, several modern 4-stroke reciprocating piston engines operate with one only compression ring per combustion chamber.

This invention discloses a way to overcome the sealing problem in the “gerotor” rotary engines by using different shapes of working surfaces (edge-less / corner-less working surfaces) and different seals.

According this invention, a rotary engine of the gerotor (or cycloid) type can utilize just one seal per working chamber (which means just one gap per working chamber), similarly to the piston ring in a reciprocating piston engine.

According this invention, the working surface (which comprises a part of the walls of the working chamber) is derived from the motion of a curved line. The curved line moves properly and creates a surface whereon the actual seal will abut on. The working surface still comprises two flat surfaces at the sides (they are parallel to each other) and a curved surface mating smoothly / tangentially the two flat surfaces. In this case, the orthogonal projection of the curved surface on a plane parallel to the flat surfaces being an area on the projection plane (a surface occupying area, not just a closed curve occupying zero area).

An object of the present invention is also to provide a method for the design of rotary engines of the gerotor family. According this method, the designer selects the form of the curved line (actually of the abutting “line” of a seal) and “moves” it as if it was secured on the “rotor”; the curved line forms / sweeps the required surface; the designer checks for “undercuts” or other issues and decides accordingly. The curved line can be plane of three dimensional, symmetrical or not. The resulting surfaces on the walls of the variable volume chamber can be symmetrical or not (which could be useful for the optimisation of the porting / breathing, for instance). Various such surfaces are shown in the figures. The geometrical design can then be translated into programming code for CNC milling machines to actually cut / grind the real pieces.

As in the known gerotor rotary engines (Wankel etc), the sealing means of this invention can be supported by spring-means located at their back. Oil control seals maybe, also, required, but these, too, are disclosed in the prior art. So the focus in the following will be on the cooperation of the “sealing grid” with the working surfaces.

This invention is for A rotary positive displacement machine of the type including a pair of relatively rotatable bodies 1,2, having cooperating surfaces that during relative movement define variable volume working chambers, comprising at least: a groove 3 on the one body and a smooth working surface 4 on the other body;

a seal 5 mounted into the groove 3 and abutting, at least for a part of a cycle, onto the smooth working surface 4 sealing a working chamber 7, the smooth working surface 4 comprising a pair of parallel, radially extending, flat surfaces 4a, 4b, and an axially and radially extending curved surface 4c smoothly / tangentially connecting the two flat surfaces 4a, 4b.

The orthogonal projection of the curved surface 4c onto a plane parallel to the flat surfaces 4a, 4b, being not a curved line but a surface having non-zero area

The sections of the curved surface 4c by planes perpendicular to the flat surfaces 4a, 4b, being not straight lines but curved lines. BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 shows a first embodiment. At top left it is shown, sliced, the casing and the stationary gearwheel. At top middle it is shown the rotor. At top right it is shown the “sealing grid”. At bottom right they are shown the three pieces comprising the “sealing grid” (which means one piece per working chamber). The grooves on the rotor are wherein the seals are mounted. At bottom left it is shown a slice of the rotor, and at its right side it is shown a slice of the casing showing the smooth transition from the curved working surface of the casing to the side flat working surfaces of the casing.

Fig 2 shows the engine of the first embodiment at six different instances. At the periphery of the casing there are shown inlet and exhaust ports, as well as a hole for a spark plug. The two intermeshed gearwheels do the synchronization The sealing means move together with the rotor and abut / slide onto the curved and the flat working surfaces of the casing.

Fig 3 shows a second embodiment, assembled at top left (the outer part is partly sliced to unhide the parts inside). At top right it is the outer body sliced, together with its ring gearwheel. At bottom left it is the inner body with its gearwheel. At bottom middle it is shown the “sealing grid” “assembled”, while at bottom right it is the “sealing grid” disassembled. Now the working surface, whereon the seals abut and slide, are on the inner body (curved “periphery, flat sides). The outer body comprises the grooves wherein the seals are mounted. It is interesting the similarity of the “sealing grid” of this embodiment with the “sealing grid” of the first embodiment. There is a difference: the seals of the second embodiment slide on the working surfaces with their inner edges, while the seals of the first embodiment slide on the working surfaces with their outer edges.

Fig 4 shows a third embodiment quite similar to the second embodiment. The difference is in the seals: each working chamber has its own, exclusive and complete, seal. For a part of its periphery each seal abuts on its groove-walls, for the rest periphery it abuts onto the seals of the neighbouring working chambers. At top middle it is shown a slice of the outer body, at top right it is shown a slice of the inner body showing the progressive I smooth transition from the curved working surface to the side flat working surfaces

Fig 5 shows an engine according the third embodiment at various angles of the inner and outer bodies. In the inner body there are inlet ports, exhaust ports and a hole for a spark plug and/or injector. Each of the three cavities in the outer body is wherein almost all the air I air-fuel-mixture is concentrated when the volume of the respective working chamber is minimized (Top Dead Center, TDC). The rotation angle of the inner body proceeds at 30 degrees steps, the rotation angle of the outer body proceeds at steps of (2/3)*30=20 degrees.

Fig 6 shows details of the third embodiment like the gap of the left seal 5G and like the relative motion of the two seals depending on the rotation angle of the eccentric shaft.

Fig 7 shows a fourth embodiment disassembled and partly sliced.

The “sealing grid” comprises five seals: two circular side seals abutting on the side flat working surfaces of the inner body (shown at right), and three “peak seals” abutting on the curved peripheral working surfaces of the inner body. The inner body comprises a hole for the spark plug, an intake port and an exhaust port.

Fig 8 shows what Fig 7 with the inner body rotated to show the inlet and exhaust ports.

Fig 9 shows the “sealing grid” of the fourth embodiment, “assembled” at left and disassembled at right. Each peak seals has “U” shape and “D” cut view.

Fig 10 shows a fifth embodiment. At top left assembled, with the outer body partly sliced. At top right it is the inner body in the periphery of which there are inlet ports, exhaust ports and spark plug and/or injector holes. At bottom middle it is shown the “sealing grid” assembled. They are also shown the five seals comprising the “sealing grid”.

Fig 11 shows a version of the fifth embodiment wherein each of the five working chambers has its own seal. At top right the one only seal (of the five) is on the periphery of the inner body and encloses I surrounds completely the one working chamber.

Fig 12 shows the inner body of the fifth embodiment sliced. At top left the slicing plane cuts the inlet ports. At top right the slicing plane cuts the exhaust pots. At bottom left the slicing plane cuts the spark plug holes. At bottom right the slicing plane is perpendicular to that used in the bottom left cut-view. This figure makes clear the smooth / progressive / step-less transition from the curved working surface to the flat working surfaces.

Fig 13 shows what Fig 12 from a different viewpoint. It makes more clear how the various passageways are arranged, how they are cooperating or how they are isolated. This figure makes clear the smooth / progressive / step-less transition from the curved working surface to the flat working surfaces.

Fig 14 sows, at left, a slice of the outer body of the fifth embodiment. At right it shows the assembly of the inner and outer bodies looked from the side, also the synchronizing gearwheels.

Fig 15 shows at left a slice of the outer body of the fifth embodiment and at right the assembly on the inner and outer bodies with their synchronizing gearwheels.

Fig 16 shows, from two viewpoints, an engine according the fifth embodiment. The outer body comprises cooling fins. They are also shown the rolling bearings by which the inner body and the outer body are rotatably mounted on a frame / casing (not shown).

Fig 17 shows, at left, the rotary engine of Fig 16 driving a propeller; at right it shows the “frame” that keeps the roller bearings in place relative to each other.

Fig 18 shows what Fig 17 from a different viewpoint. At right it shows the frame of the engine and how the inner body is rotatably mounted on it.

Fig 19 shows, from two different viewpoints, the frame of the propulsion unit of Fig 16. It also shows a throttle valve and how it is supported on the casing.

Fig 20 shows at left how the working surfaces of the gerotor rotary engines of the art is derived. There are three distinct surfaces, the two side ones being flat, the peripheral one being “cylindrical” and normal I perpendicular to the other two. At right it is shown how the working surfaces of a gerotor rotary engine made according this invention can derive. Now there is just one continuous and smooth working surface (without edges / corners / steps).

Fig 21 shows what Fig 20 with the “surfaces” completed to close.

Looking from the “rotation axis” direction (top left and top right), the case seems identical. But looking from an oblique viewpoint, the one working surface (bottom right) is smooth at all directions while the other working surface (bottom left) comprises distinct surfaces and edges I corners of “zero” curvature.

Fig 22 shows the case wherein the generating curve line is oblique (it is on a plane, or planes, not passing thought the “rotation axis”). At left the viewpoint is on the “rotation axis”, at right the viewpoint is oblique.

Fig 23 shows stereoscopically the “sealing grid” (comprising three parts) at top, the seals onto the working surface of the inner body (middle), and the seals onto the working surface of the inner body which is located inside the outer body (bottom). As in Fig 22, the generating curved line is oblique.

Fig 24 shows how, from the generating curved line it results a seal that cooperates with the working surface.

Fig 25 shows what Fig 24, but in this case each working chamber has its own seal. Worth to mention: the “inner” side of each seal (which abuts on the “inner” sides of the other two seals) is flat, while the external side (external with reference to the “assembly” of the three seals) is “wedge ended”.

Fig 26 shows what Fig 21 with the flat side surfaces removed. At top left and at top right they are shown the orthogonal projections in a plane parallel to the flat side surfaces. The one projection is a closed curve having no area, the other projection is an area (a zone) on the plane.

Fig 27 shows the inner body and the seals of a version of the fifth embodiment. The set of the five seals is shown arranged onto the inner body (as in operation), the same set of the five seals is shown alone at middle top. At middle right, at bottom left and at bottom right it is shown the one of the five seals from three different viewpoints. At bottom middle it is shown a flat piston ring like those used in the Honda NR750 engine wherein “oval” pistons enable the accommodation of eight poppet valves per combustion chamber. It is like taking a seal (or “piston ring”) from the Honda NR750 reciprocating piston engine, bending it properly (the area with R2 radius) and putting it to operate with its inner edge in the rotary engine. This drawing shows how similar can be the sealing of a rotary engine with curved working surface (not cylindrical as in the prior art rotary engines, but 3D curved). The simplicity and leakage-free characteristics of the reciprocating piston engines are applied in the rotary engines. The strange shape of the “shaft” enables the maximization of the intake and exhaust areas.

Fig 28 shows an engine according the fifth embodiment at various angles of the inner and outer bodies, and of the seals. The rotation angle of the inner body proceeds at 15 degrees steps, the rotation angle of the outer body proceeds at steps of (4/5)*15=12 degrees. Only a thin slice of the outer body is shown.

Fig 29 shows, similarly to Fig 28, another six “instances” of the operation. Two combustions happen per compete rotation of the inner body. Each chamber completes a cycle of operation into 225 degrees of rotation of the inner body.

Fig 30 shows the first embodiment with an eccentric shaft 8 rotatably mounted on the casing. The rotor is rotatably mounted on an eccentric pin of the eccentric shaft 8.

PREFERRED EMBODIMENTS

In a first embodiment, Figs 1,2, 30, the rotary engine resembles to the conventional Wankel rotary engine. However, the working surface on the casing (or outer body) whereon the seals abut and slide, is smooth without edges / corners. The side flat surfaces are smooth extensions / continuations of the central curved surface. The curvature changes smoothly / progressively.

In comparison to the prior art (wherein the side seals are different parts than the apex or peak seals), in this rotary engine the apex seal and the side seals are intergraded in one piece.

Figs 20 and 21 show how the working surface of the casing can derive “geometrically”. A curved line C2, starting at a point P2 and ending at the point P2’ and “moved” as if it was secured on the rotor as a seal, sweeps the working surface which is smooth and rid of corners. The transition from the point P2 (which is on the one flat surface) to the point P2’ (which is on the other flat surface), is smooth without abrupt points or corners.

The engine can have peripheral and/or side ports, as the conventional Wankel engine. For manufacturing and assembly reasons, the casing can be divided into two pieces (the one as shown in Fig 1 top left); alternately the casing can be divided into three pieces, each comprising a working chamber.

Under the seals, inside the grooves on the inner body, they can be added springs (as in the conventional Wankel engine) to preload the seals over the working surfaces.

Oil control seals can be added at the flat sides of the rotor (as in the conventional Wankel).

Combustion bowls can be cut on the rotor (as in the conventional Wankel engine).

The cooling and the lubrication can be according the prior art.

The curved working surface on the casing enables bigger peripheral ports.

The casing 1 is stationary. An eccentric shaft (shown in Fig 30) is rotatably mounted on the casing 1. The rotor 2 is rotatably mounted on an eccentric pin of the eccentric shaft. The ring gear wheel on the rotor is meshed with the stationary gear wheel on the casing for the synchronization.

In a second embodiment, Fig 3, the working surface (whereon the seals abut and slide during operation) is on the inner body 2. The “sealing grid” can be similar to that of the first embodiment, but now it is the “inner” edge of the seal that works. Each combustion chamber is served by two seals, with the ends of the one abutting on the other (Fig 3, bottom right). An engine or pump or compressor made according this embodiment can operate as a conventional rotary engine (say, like the engine proposed in the US8,523,546, wherein an eccentric shaft rotatably mounted on the outer body, holds / drives (by an eccentric pin) the inner body. An engine or pump or compressor made according this embodiment can, alternatively, operate as a true rotary engine wherein the inner and outer bodies perform pure rotations about two stationary (and parallel) rotation axes.

In a third embodiment, Figs 4 and 6, each combustion chamber uses its own seal (i.e. the working medium “sees” one only seal “surrounding” the working chamber). The gap on a seal can be arranged properly (as in Fig 6, for instance) to minimize the leakage. An internal combustion engine made according the third embodiment is shown at various instances of operation in Fig 5. The outer body comprises a cavity per combustion chamber.

Intake and exhaust ports on the inner body (and passageways not shown) allow the breathing of the engine. The shaft of the inner body can be hollowed, with the intake at one side and the exhaust at the other side of the engine. Inside the inner body it is secured a spark plug (not shown) that, through a hole in the inner body, sees the working chambers one by one. There is plenty of space inside the inner body wherein the circuitry for the ignition can be mounted, even the electric generator for the ignition.

In a fourth embodiment, Figs 7 to 9, the inner body comprises intake and exhaust ports. The outer body comprises grooves wherein the seals are mounted, it also comprises cavities wherein the fluid is concentrated at the end of the compression. The outer body needs not to have ports on it. The working fluid is inserted into the engine through the one end of the holed shaft of the inner body. The exhausted fluid leaves the engine through other end of the holed shaft of the inner body. The spark plugs and/or injectors can be mounted either on the outer body, or preferably on the inner body. In such a case, a single spark plug or injector can serve all three working chambers. As in the third embodiment, the spark plugs and the entire ignition system can be mounted inside the inner body. Even the required electric power for the ignition can be generated inside the inner body. The required circuitry can be located nearby, or inside, the intake passageways to remain cool.

In a fifth embodiment, Figs 10 to 19 and 27 to 29, the rotary engine has five working chambers. Each working chamber can have its own seal (as in Fig 11). The working surfaces whereon the seals abut and slide, are on the inner body. There are intake and exhaust ports cut in, and on, the inner body.

As shown in Figs 12 and 13, the inner body has passageways through which the engine breaths; at top left they are shown the passageways though which the working fluid is provided to the inlet ports, at top right they are shown the passageways through which the exhausted gas exiting from a working chamber leaves the engine. At bottom left they are shown the passageways through which the spark plugs and/or the injectors are inserted I mounted in the inner body. At bottom right they are shown the isolated intake and exhaust, also the available space into the inner body for auxiliary equipment (like a complete ignition system including the generation of the required electric power, or like the high pressure pump in case of a direct injected spark ignition or compression ignition engine.

In the Wankel rotary engine the casing holes that accommodate spark plug(s) cause significant leakage of compressed gas to the neighbour working chambers. In the engine of the fifth embodiment (as well as in the engines of the second, third and fourth embodiments) the leakage from the inner body holes that accommodate spark plugs and/or injectors is by far smaller because they pass over the seals at the end of the expansion.

The synchronizing gearwheels have a 4:5 transmission ratio.

Given the distance E (or “eccentricity”) of the two rotation axes, the pitch circle diameter of the small gear is 4*E while the diameter of the pitch circle of the ring gear is 5*E (in comparison, the pitch circle diameter of the small gear of the embodiments with the three working chambers (Figs 1 to 9, wherein the synchronizing gearwheels have a 2:3 ratio), is only 2*E). The big diameter synchronizing gearwheels of the fifth embodiment allows big diameter intake and exhaust ducts and freer breathing. It also allows auxiliary means (like the spark plugs) to pass and get installed, or be controlled, from outside the inner body.

In the Figs 17 and 18 it is shown the engine of the fifth embodiment driving a propeller at the back of an airplane (not shown). The 3 dimensional net / frame keeps the two pairs of roller bearings at the proper position relative to each other; it also serves for the mounting of the engine.

The inner and outer bodies are both rotating about constant rotation axes.

There is no need for balance webs. With the inner body fully balanced as it rotates alone on its bearings (Fig 18, right), and with the outer body fully balanced as it rotates alone on its bearings, the engine is perfectly rid of unbalanced inertia force, moment and torque.

A throttle valve (shown in Figs 18 and 19) can be supported on the stationary frame / casing to control the entrance of the rotating shaft of the inner body at the intake side.

A silencer (Figs 17 and 18) can rotate with the inner body. A small gap between the exhaust pipe and the hollowed shaft prevents the overheating of the shaft and of the bearings whereon it is supported.

There is no eccentric shaft. This saves a lot of weight. It also saves space at the centre of the engine.

The simplicity, smoothness, reliability, lightweight etc makes such a propulsion unit a good choice especially for flying applications (airplanes, helicopters, portable flyers etc).

The previous are applicable in internal combustion engines, in external combustion engines (Stirling cycle etc), in air compressors, in pumps etc.

Although the invention has been described and illustrated in detail, the spirit and scope of the present invention are to be limited only by the terms of the appended claims.

Claims

1. A rotary positive displacement machine of the type including a pair of relatively rotatable bodies (1,2) having cooperating surfaces that during relative movement define variable volume working chambers, comprising at least:

a groove (3) on the one body and a smooth working surface (4) on the other body;

a seal (5) mounted into the groove (3) and abutting, at least for a part of a cycle, onto the smooth working surface (4) sealing a working chamber (7), the smooth working surface (4) comprising a pair of parallel, radially extending, flat surfaces (4a, 4b) and an axially and radially extending curved surface (4c) smoothly / tangentially connecting the two flat surfaces (4a, 4b).

2. A rotary positive displacement machine according claim 1 wherein the orthogonal projection of the curved surface (4c) onto a plane parallel to the flat surfaces (4a, 4b) being not a curved line but a surface having non-zero area.

3. A rotary positive displacement machine according claim 1 wherein the section of the curved surface (4c) by planes perpendicular to the flat surfaces (4a, 4b) being not straight lines but curved lines.

4. A rotary positive displacement machine according claim 1 wherein the curved surface (4c) is a three dimensional surface in the meaning that its sections by planes parallel to the flat surfaces (4a, 4b) are not the same.

5. A rotary positive displacement machine according claim 1 wherein the same seal (5) abuts onto the curved working surface (5) and onto one, or both, of the flat working surfaces (4a, 4b).

6. A rotary positive displacement machine according claim 1 wherein a single piece seal (5) abutting onto the smooth working surface (4), together with the two rotatable bodies (1,2), completely encompasses a working chamber (7).

7. A rotary positive displacement machine according claim 1 wherein a pair of seals (5) abutting on the smooth working surface (4), together with the two rotatable bodies (1,2), encompasses and seals a working chamber (7).

8. A rotary positive displacement machine according claim 1 wherein the rotatable bodies (1,2) are rotatably mounted on a frame to rotate about fixed axes.

9. A rotary positive displacement machine according claim 1 wherein a first body (1) of the pair of relatively rotatable bodies being stationary, and wherein a second body (2) of the pair of relatively rotatable bodies being rotatably mounted on an eccentric shaft (8), and wherein the eccentric shaft being rotatably mounted on the first body (1).

10. A rotary positive displacement machine according claim 1 wherein the rotatable bodies (1,2) comprising intermeshed gearwheels to synchronize their motions.

11. A method for the design of rotary positive displacement machines of the type including a pair of relatively rotatable bodies (1,2) having cooperating surfaces that during relative movement define variable volume working chambers, wherein:

a curved line moving as if it was secured on the one rotatable body forms a working surface on the other rotatable body whereon a seal mounted on a groove of the other rotatable body abuts completely encompassing, together with the two rotatable bodies, a working chamber.

Intellectual

Property

Office

Application No: GB1621647.5