GB1562861A

GB1562861A - Rotary machine

Info

Publication number: GB1562861A
Application number: GB2670377A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-06-25
Filing date: 1977-06-25
Publication date: 1980-03-19

Description

(54) ROTARY MACHINE (71) I, RALPH MELVIN HOFFMANN, a citizen of the United States of America, residing at 15950 North Hillcrest Court, Eden Prairie, Minnesota, U.S.A., do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to rotary machines, for example rotary expansion steam power units of the type having a planetating rotor.

It provides, inter alia a unidirectional rotary expansion steam power unit which is free from external valving arrangements and independent starting mechanisms, and which is adapted for multiple use in a system selectively using direct energization and compounding of the units. The power fluid is supplied through a hollow rotor, and is conducted to working chambers and exhausted therefrom by strategically located passages in the walls of a housing under the control of seal means carried by the rotor.

When driven in the reverse direction instead of by steam, the power unit functions as an air compressor.

In rotary expansion steam engines of the Wankel type, the flow of pressure or working fluid into the working chambers is controlled by valves external to the engine cavity, the action of which valves is synchronized with the rotor motion through the crankshaft and gear trains or like systems. Such engines are known as variable cutoff or variable displacement engines because the amount of steam admitted, and hence the expansion thereof, may be varied by altering the time during which the inlet valves are open. This necessity for external valves and mechanisms for timing their operation results in an expansion engine of relatively great complexity, bulkiness and cost. Therefore, expansion engines of the Wankel type have not heretofore been competitive with sliding vane type expansion engines, in spite of the greater capability and efficiency of the Wankel type engines.

Internal combustion single rotor engines produce intermittent torque, and, depending on port design, may produce a negative torque during a portion of one single rotation, thus requiring a flywheel and operation with minimum rotational speeds of approximately 500 rpm. According to the present invention a single rotor engine can deliver uninterrupted torque moments; it is capable of slow speed operation and does not require a flywheel as does a Wankel type internal combustion engine.

The present invention provides a rotary machine comprising: a housing having mutually opposite end walls spaced apart along a first axis by a peripheral wall shaped to define an epitrochoidal cavity symmetrical about the first axis and having two lobes intersecting at lobe junctures which lie at opposite ends of a minor axis of the cavity and which is normal to the first axis, one of the lobes lying in first and second quadrants about the first axis and the other lying in third and fourth quadrants thereabout;; a hollow rotor symmetrical about a further axis parallel with and spaced apart from the first axis, the rotor having opposite side wall surfaces adjacent the end walls of the housing, and interconnected by a plurality of peripheral flank surfaces which intersect at apices to define lines of sealing contact with the peripheral wall of the housing, at least one of said side wall surfaces being in slightly spaced relation to the respective adjacent end wall of the housing to provide an interstice therebetween; means, including a crankshaft on which the rotor rotates on said further axis eccentrically with respect to the first axis, for limiting motion of the rotor in the cavity to planetating movement about the first axis in the direction from the fourth quadrant to the first quadrant, so that the apices sweep through the lobes;; mutually spaced seal means, including radially inward valving seal means and radially outward chamber-isolating seal means, carried by one or each side wall surface of the rotor to move in the interstice between said side wall surface and the adjacent end wall of the housing, an aperture in said side wall surface communicating with the interior of the rotor and being encircled by the valving seal means so that the rotor and the housing jointly define a plenum sealed by the valving seal means, and there being defined by the rotor and the housing a plurality of distinct working chambers each radially outward of the chamber-isolating seal means and lying between adjacent apices, which move about the first axis and successively increase and decrease in volume with said movement of the rotor;; passage means for the working fluid said passage means communicating through the hollow rotor between the outside of the housing and the inside of the housing at a site inward of the valving seal means; bridging passage means in the inner surface of one or each of said end walls, locating and sized to conduct working fluid between the plenum and the working chambers during first predetermined portions of said movement; and further passage means in said inner surface of said one or each of the end walls for affording fluid connection with the working chambers during second predetermined portions of said movement.

Rotary machines of the invention require no external valves and timing mechanisms, and hence can be relatively small in size, simple in construction and inexpensive to operate. The planetating rotor itself functions in cooperation with the passages in the housing walls to control the timing and duration of the flow of pressure or working fluid to and from the working chambers. An advantage of expansion power units of the invention is the fact that they are suitable for starting without the use of a separately power external starting system, and for operation always in a single direction. The units are also well adapted for either direct or compound energization with the power fluid.

The passage means in the housing end wall can be so located as to prevent power fluid from being supplied to any working chamber prematurely to the extent of creating an undesirable negative torque, a defect usually found in fixed-displacement or fixedcutoff engines lacking external valves and valve gear. As a result my engine may be designed to provide positive and uninterrupted torque at any speed above zero rpm.

There is now described, by way of example and with reference to the accompanying drawings, an embodiment of a rotary machine of the invention, which is a power unit.

In the drawings, FIGURE 1 is a view of a power unit according to my invention seen axially, with an end wall removed for clarity of illustration; FIGURE 2 is an enlarged sectional view of the power unit, taken generally along the line 2-2 of FIGURE 1 and showing the rotor in a "dead-center" position; FIGURES 3, 4 and 5 are views like FIGURE 2 showing the rotor in other positions; FIGURE 6 is a diagram illustrating the principles determining the shapes and locations of passage mean essential to the invention; and FIGURE 7 shows a power system made up of a plurality of power units as disclosed in FIGURES 1-5.

As shown in FIGURES 1-5, a power unit according to my invention comprises a housing 11, a rotor 12, and a crankshaft 13. Housing 11 comprises a pair of opposite end walls 14 and 15, spaced apart along the axis 16 of crankshaft 13 by a peripheral wall 17 shaped to define a cavity 20 symmetrical about axis 16 and having a pair of epitrochoidal lobes 21 and 22 which intersect at lobe junctures 23 and 24 which define the minor axis of the housing.

Crankshaft 13 is mounted in bearing inserts 18 and 19 in end plates 14 and 15, and includes an eccentric 25 which is itself circular in traverse section to engage a hollow circular bearing 26 in rotor 12. The rotor is symmetrical about the axis 27 of bearing 26 and eccentric 25 and hence is radially displaced from axis 16 by an eccentricity e.

It comprises a pair of opposite side wall surfaces 30 and 31, adjacent and in slightly spaced relation to housing end walls 14 and 15, and interconnected by a plurality of smooth epitrochoidal flank surfaces 32, 33 and 34 which intersect at apices 35, 36 and 37. The rotor includes a rim 40 of varying thickness, a web 41, and a hub 42 containing bearing 26. Web 41 is provided with a plurality of paraxial apertures 43. Rotor 12 is referred to as hollow to define apertures 43 and the spaces 44 and 45 inward from rim 40 on each side of web 41 which function as a plenum space. An external gear 46 is fixed to bearing insert 19 concentric with axis 16 and hence with crankshaft 13, and an internal gear 47 is fixed in rotor 12 concentric to axis 27 to mesh with gear 46. Sidewalls 30 and 31 each has a central circular aperture: the aperture in sidewall 30 is shown in Figure 2 but that in sidewall 31 is obscured by internal gear 47.

For the structure shown, where housing 11 has two lobes and rotor 12 has three apices, the tooth ratio between gear 47 and gear 46 is 3: 2: It will be appreciated that epitrochoidal cavities of more lobes can be used, with rotors of more apices, and that the gear ratio will change accordingly.

Crankshaft 13 is mounted for rotation in bearings 50 and 51 carried by inserts 18 and 19, respectively.

Eccentric 25 and gears 46 and 47 combine to limit the movement of rotor 13 in housing 11 to a combination of rotation about axis 27 and revolution about axis 16, which I have defined as planetating movement. Apices 35, 36 and 37 define the location of lines of sealing contact between the rotor and the housing, and may be provided with suitable seal blades 52, 53 and 54. Rotor flanks 32, 33 and 34 and housing lobes 21 and 22 combine to define a plurality of working chambers 55, 56 and 57, which move about axis 16 with movement of flank surfaces 32, 33 and 34 respectively of the rotor, decreasing and increasing in volume cyclically as they do so.

Pressure fluid is supplied to the hollow rotor from a source such as a steam boiler, not shown, through a conduit 59 and an inlet connection 60 to an annular channel 61 in wall 14, and it is intended to be supplied to working chambers 55, 56, and 57 at appropriate times to act on the rotor flanks 32, 33 and 34 respectively so as to cause rotor planetation in a generally clockwise direction as seen in FIGURE 1. To this end, O-rings 62 or other suitable means are provided between wall 17 and walls 14 and 15, respectively, and similar O-rings 63 are provided to seal inserts 18 and 19 to housing walls 14 and 15. Side wall surfaces 30 and 31 are also provided with seal means to control the flow of pressure fluid in the interstices 64 and 65 between them and housing end walls 14 and 15, all respectively.These seal means comprise valving seal means and working chamber isolation seal means respectively. The former comprises sealing rings 66 of sealing material received in circular grooves 70 in the rotor side wall surfaces. The latter comprises sealing members 67, 68 and 69 received in grooves 71 in the side wall faces and suitably sealed at their ends to blades 52, 53 and 54.

In the inner surface of wall 15, in the area of lobe 22 near lobe junction 23 (FIG.

1), there is provided first passage means comprising a plurality of grooves 72a, 72b, 72c extending generally radially from axis 16, and for a double acting engine similar grooves 73a, 73b and 73c, are similarly located in the like area of lobe 21. The purpose and location of these passage means is to conduct pressure fluid from the hollow rotor to the cavity lobes at appropriate times to cause the desired motion of rotor 12 by pressure on a flank thereof.

In the "dead-center" position of the crankshaft, shown in FIGURE 1, working chamber 57 is at its smallest volume, and passage means 73 conducts pressure fluid past seal means 66 and 69 to lobe 21 to act on flank surface 34 of rotor 12, while passage means 72 does not reach past seal means 66 and hence does not supply pressure fluid to lobe 22 to act on flank surface 33.

Other conditions are illustrated in FIG URES 3-5 and will be discussed presently below.

Further passage means 74, 75 are provided in wall 15 at locations near lobe junctions 23 and 24. The purpose of these passages is to provide egress for pressure fluid from cavity lobes 21 and 22 at appropriate times, and for this purpose, they are connected through apertures 76, 77 and conduits 80 and 81 to an exhaust connection, not shown, which may be a condenser for reducing the exhaust steam to water and turning it to the boiler. As shown in FIGURE 1, working chamber 55 is in communication with passage 74, while passage 75 is isolated by seal means 66 and 69.

Again, other conditions are illustrated in FIGURES 3-5.

In FIGURES 1 and 2, there are shown additional conduits 82 and 83 leading to passages 72 and 73, and connected as at 84 to inlet conduit 59 through a starting valve 85.

For an understanding of the principles underlying the location and shaping of passage means 72, 73, reference should now be made to FIGURE 6. In this Figure O is the axis of rotation of the crankshaft, e is the eccentricity of the eccentric 25, and R is the inside radius of sealing ring 66.

Two angles A and B are of interest, and will presently be defined. It will be realized that the circle 0 of radius e traces the path of the center of the circular eccentric around the crankshaft axis, and the circle O of radius R + e is the outer limit of all positions of the sealing ring. Dead center of the crankshaft is a position in which eccentric 25 is nearest to a lobe juncture, and is also as has been pointed out, the position of minimum volume of a working chamber. Moreover, at this crankshaft position the moment arm of pressure acting on the rotor flank defining that working chamber is zero. Power fluid admitted to the working chamber later in the rotation of the crankshaft cannot have a negative torque effect on the rotor, and passage means 72, 73 could be designed not to admit fluid before then.However, a finite interval is required for the passage of power fluid into the chamber, and practically the fluid admission can begin a few degrees ahead of dead center, to have the minimum volume of the working chamber fully charged with power fluid by the time the rotor is in the dead-center position, without building up a significant reverse torque, particularly since the moment arm is ap proaching zero. A lead angle of ten degrees not only may be tolerable, but is desirable to insure adequate filling of the working chamber with power fluid. This is the angle A of FIGURE 6.

The angle B is defined purely geometrically. It is the position of the rotor at which the volume Z of the working chamber reaches a value, compared to the maximum volume, which is the reciprocal of the expansion ratio. The later is chosen as a matter of design, having a bearing on the efficiency of the engine and its power output. An expansion ratio of 8:1 is representative. In determining the volume it is necessary to consider not only the space between a flank of the rotor and the ap posed housing wall, but also the volumes of the grooves making up passage means 72 and 73: these passages should therefore be as shallow as can be without restricting the flow of power fluid unduly. As shown in the Figure, a typical value for angle B is 1050.

The shaded area in FIGURE 6 is defined by the circle of radius R plus e centered on 0, and by two circles of radius R centered on the circle of radius e at the radii defining angles A and b respectively. Passage means 72 should terminate inwardly within this area for optimum operation of my engine. To the extent that the inner edges of the grooves lie further inward than this area, the power of the engine suffers because power fluid is then permitted to enter the working chamber prematurely, resulting in a negative torque component at the crankshaft. Outwardly the passage means must extend quite close to wall 17 to communicate with the working chambers in their minimum volume condition. The same principles apply in respect to passage means 73a, 73b and 73c.

I have shown three grooves in side-byside relation. One advantage of this arrangement over a single wider groove is that it is less wearing on sealing member 66 as it sweeps over the area when support ridges are present. The actual shape of the grooves is not critical: in FIGURE 6 I have shown grooves 73a, 73b and 73c as having a slightly different configuration from grooves 72a, 72b and 72c, but it is to be noted that they all terminate inwardly within the critical shaded area.

Passage means 74 are not so critical. It is only necessary that they be poitioned for uncovering by sealing members 67, 68, 69 when the working chambers have reached their maximum volume and for re-covering before power fluid is next admitted to the working chambers, and that they be large enough to prevent restriction in the exhaust flow of power fluid. This function may indeed be performed by an outlet passage properly positioned in wall 17, as suggested by the dotted line passage 78 in FIGURE 6. For convenience of description it may be said that inlet passages are located in the first and third quadrants, and outlet passages are located in the second and fourth quadrants.

A cycle of driven operation of my crankshaft 13 will now be traced through FIG URES 1, 3, 4 and 5. For the locations of passage means 72, 73, 74 and 75 shown, the rotation of the crankshaft is clockwise, as is the planetation of rotor 12 in cavity 20.

In the position of the rotor shown in FIG URE 1, working chamber 55 is free to exhaust at passage means 74, chamber 56 is closed off but filled with pressure fluid, although not yet at its maximum volume, and chamber 57 is open at passage means 73 to admit power fluid, and is at its minimum volume. The moment arm of power fluid force on flank 34 acting on crankshaft 13 through eccentric 25 is momentarily zero, but the fluid force on flank 33 has a moment arm in a direction to rotate the crankshaft clockwise, and as soon as the "dead-center" position is passed, the moment arm of the fluid force on flank 34 increases in the same direction, while that on flank 33 decreases.

Rotation of crankshaft results, and is accompanied by planetation of rotor 12.

After 90 degrees of rotation of crankshaft 13, which accompanies 30 degrees of rotation of rotor 12 about axis 27, sealing ring 66 closes off passage means 73 from communication with chamber 57, isolating the power fluid in chamber 57 to give up its energy by expansion. After about 150 degrees rotation of the crankshaft, which accompanies 50 degrees of rotation of rotor 12 about axis 27, sealing member 67 closes off passage means 74 and sealing ring 68 opens passage means 75. FIGURE 3 shows the relative position of the parts after 180 degrees of rotation of the crankshaft, accompanied by 60 degrees of rotation of the rotor.

FIGURES 4 and 5 show respectively the relative positions of the parts after 210 degrees and 300 degrees respectively of crankshaft rotation, which accompanies 70 degrees and 100 degrees respectively of rotation of rotor 12.

It will be appreciated that each rotation of the crankshaft by 360 degrees is accompanied by rotor rotation of 120 degrees, in which the cycle just described for flank 34 is repeated for flank 33 and then for flank 32. Three crankshaft cycles are needed for a single rotor cycle.

Referring again to FIGURES 3 and 2, the need for elements 82, 83 and 85 will now be apparent. If valve 85 is open momentarily, pressure fluid is admitted to the working chamber via passages 82 and 83. Although passage means 75 is open to exhaust, chamber 57 is sealed, so the fluid pressure on flank surface 34 causes rotation of the crankshaft in the desired direction. After starting is accomplished, valve 85 is closed and engine operation continues as originally described.

It will be appreciated that the power unit just described functions as the equivalent of a three-cylinder piston engine: each flank of rotor 12 is subject to two power strokes per rotation of the rotor about axis 27, which accomplishes three rotations of crankshaft 13 about axis 16.

The power obtainable from any engine is determined by its displacement. In piston engines, the total power available is increased not only by increasing the size of the cylinders but by increasing their number, the pistons acting about a common crankshaft, and the same principle is applicable to my power units, as is shown in FIGURE 7.The efficiency of power extraction from a pressure fluid is not affected if several power units on a common crankshaft are supplied individually with the fluid, but may be considerably increased by the practice known as compounding, which comprises passing the power fluid through more than one power unit in sequence, extracting a first portion of the power from the fluid in the first unit through initial expansion of the power fluid, and extracting more power in another unit through additional expansion of power fluid, the sum effect of the successive expansions being greater than can be practically obtained in only one expansion in one unit. To accomplish this, the displacement of the later unit must be greater than that of the first unit, to allow for effective expansion of the pressure fluid exhausting from the first unit.

FIGURE 7 also shows how three of my power units may be compounded, the fluid exhausting from one being fed to two others.

A still further aspect of my invention is also shown in FIGURE 7. Consider the case of a vehicle which does most of its traveling in relatively level country, but must occasionally traverse extended relatively steep grades. An engine designed for adequate power to traverse the grades at acceptable speeds would be operating at an inefficiently low power level in the substantially flat portions of its travel. I have devised a conduit system which operates three of my power units independently or in a compound relation, depending on the positioning of a set of valves, to drive a single crankshaft. By this arrangement, the compounding configuration can be used for greater efficiency in level terrain, and all units can be directly energized to obtain greater torque when mountainous country is encountered.This is the functional equivalent, in simpler form, of having a second engine to couple in when additional torque is needed.

FIGURE 7 specifically shows how three of my units may be arranged in a system for operation efficiently at a first power rating, or less efficiency at a higher power rating. Three power units 10a, 10b, and 10c are used, each like unit 10 described above, and their rotors are carried on a common crankshaft 89. Pressure fluid is provided to the engines in a conduit 90 to a manifold 91, which is connected by a first tap 92 to the inlet of unit 10a. The outlets 80a and 81a of unit 10a are connected by a conduit 93 to a second manifold 94, from which conduits 95 and 96 lead to a pair of valves 97 and 100. These valves are also connected by conduits 101 and 102 to manifold 91, and by conduits 103 and 104 to the inlets of units 10b and 10c. Manifold 94 is further connected through a valve 105 to a conduit 106.Conduit 106 and the outlets 80b, 80c, 81b and Sic of units 10b and 10c, are permanently connected to an exhaust or a condenser.

Valves 97, 100 and 105 may be interconnected by suitable means 107 for simultaneous operation between two system configurations, as follows. In the first configuration, valve 105 is closed, valve 97 connects conduit 95 to conduit 103, and valve 100 connects conduit 96 to conduit 104. In this configuration, power fluid is supplied directly to unit 10a, while units 10b and 10c are energized with the power fluid exhausted from unit 10a. The combined volumes of units 10b and 10c are approximately half that of unit 10a. By the familiar process of compounding, a first portion of the energy in the pressure fluid is extracted by unit 10a, and a second portion is extracted by units 10b and 10c.

If the occasion arises when greater power is needed and efficiency can be sacrificed, valves 97, 100 and 105 are moved to establish the second system configuration. Here pressure fluid is supplied to unit 10a directly as before, to unit lOb directly through manifold 91, conduit 101, valve 97, and conduit 103, and directly to unit 10c through manifold 91, conduit 102, valve 100 and conduit 104: units 10b and 10c exhaust as before, while unit 10a exhausts through conduit 93. manifold 94, valve 105, and conduit 106.

An additional advantage of my structure lies in the fact that it can function as an efficient compressor. Conduits 80 and SI of FIGURE 1 then comprise the inlet of the machine, and conduit 59 is the outlet: the shaft 13 must be mechanically driven in the direction opposite to that in which it runs as a motor. Check valving is desir able to prevent the compressor from being run as an air motor when not being mechanically driven.

From the foregoing, it will be evident that I have invented a new and improved rotary expansion power unit which retains the advantages of power to weight ratio and power to volume ratio which characterize rotary expansion engines, while avoiding the complications of external valving and starting mechanisms, which may operate at low or high speeds because of its continuous torque, and which is well adapted for use in a power system in which several units are energized either directly or in compound fashion to give the user an election between maximum available torque and maximum fuel economy.

WHAT I CLAIM IS: - 1. A rotary machine comprising: a housing having mutually opposite end walls spaced apart along a first axis by a peripheral wall shaped to define an epitrochoidal cavity symmetrical about the first axis and having two lobes intersecting at lobe junctures which lie at opposite ends of a minor axis of the cavity and which is normal to the first axis, one of the lobes lying in first and second quadrants about the first axis and the other lying in third and fourth quadrants thereabout;; a hollow rotor symmetrical about a further axis parallel with and spaced apart from the first axis, the rotor having opposite side wall surfaces adjacent the end walls of the housing, and interconnected by a plurality of peripheral flank surfaces which intersect at apices to define lines of sealing contact with the peripheral wall of the housing, at least one of said side wall surfaces being in slightly spaced relation to the respective adjacent end wall of the housing to provide an interstice therebetween; means, including a crankshaft on which the rotor rotates on said further axis eccentrically with respect to the first axis, for limiting motion of the rotor in the cavity to planetating movement about the first axis in the direction from the fourth quadrant to the first quadrant, so that the apices sweep through the lobes;; mutually spaced seal means, including radially inward valving seal means and radially outward chamber-isolating seal means, carried by one or each side wall surface of the rotor to move in the interstice between said side -wall surface and the adiacent end wall of the housing, an aperture in said side wall surface communicating with the interior of the rotor and being encircled by the-valving seal means so that the rotor and the housing jointly define a plenum sealed by the valving seal means, and there being defined by the rotor and the housing a plurality of distinct working chambers each radially outward of the chamber-isolating seal means and lying between adjacent apices, which move about the first axis and successively increase and decrease in volume with said movement of the rotor;; passage means for the working fluid said passage means communicating through the hollow rotor between the outside of the housing and the inside of the housing at a site inward of the valving seal means; bridging passage means in the inner surface of one or each of said end walls, located and sized to conduct working fluid between the plenum and the working chambers during first predetermined portions of said movement; and further passage means in said inner surface of said one or each of the end walls for affording fluid connection with the working chambers during second predetermined portions of said movement.

2. A rotary machine according to Claim 1, in which the bridging passage means is positioned off said minor axis in an oddnumbered one of said quadrants and extends inward from near the location of the peripheral wall to a site lying inward of the valving seal means during said first predetermined portions of said movement, and said further passage means is positioned off said minor axis in an even-numbered one of said quadrants to always lie outward of said valving seal means, and to be located between said valving and isolating seal means except during said second predetermined portions of said movement.

3. A rotary machine according to Claim 1 or Claim 2, in which the bridging passage means is such as to conduct pressure fluid from the plenum space to the working chambers during said first predetermined portions of said movement, and said further passage means is such as to afford egress of pressure fluid from said working chambers during said second predetermined portions of said movement.

4. A rotary machine according to Claim 1, 2 or 3, in which the valving seal means is circular at a known radius about said further axis, and the inward reach of said bridging passage means falls in the area Iving inside a first circle, centered on said first axis and having a radius equal to the sum of said known radius added to the eccentricity of said further axis about said first axis, and lying outside two further circles having said known radius and centered on the intersections, with the circle about said first axis traced bv said further axis, of two radii angularlv displaced about said first axis from said minor axis by two opposite angles of predetermined magnitudes.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. able to prevent the compressor from being run as an air motor when not being mechanically driven. From the foregoing, it will be evident that I have invented a new and improved rotary expansion power unit which retains the advantages of power to weight ratio and power to volume ratio which characterize rotary expansion engines, while avoiding the complications of external valving and starting mechanisms, which may operate at low or high speeds because of its continuous torque, and which is well adapted for use in a power system in which several units are energized either directly or in compound fashion to give the user an election between maximum available torque and maximum fuel economy. WHAT I CLAIM IS: -

1. A rotary machine comprising: a housing having mutually opposite end walls spaced apart along a first axis by a peripheral wall shaped to define an epitrochoidal cavity symmetrical about the first axis and having two lobes intersecting at lobe junctures which lie at opposite ends of a minor axis of the cavity and which is normal to the first axis, one of the lobes lying in first and second quadrants about the first axis and the other lying in third and fourth quadrants thereabout;; a hollow rotor symmetrical about a further axis parallel with and spaced apart from the first axis, the rotor having opposite side wall surfaces adjacent the end walls of the housing, and interconnected by a plurality of peripheral flank surfaces which intersect at apices to define lines of sealing contact with the peripheral wall of the housing, at least one of said side wall surfaces being in slightly spaced relation to the respective adjacent end wall of the housing to provide an interstice therebetween; means, including a crankshaft on which the rotor rotates on said further axis eccentrically with respect to the first axis, for limiting motion of the rotor in the cavity to planetating movement about the first axis in the direction from the fourth quadrant to the first quadrant, so that the apices sweep through the lobes;; mutually spaced seal means, including radially inward valving seal means and radially outward chamber-isolating seal means, carried by one or each side wall surface of the rotor to move in the interstice between said side -wall surface and the adiacent end wall of the housing, an aperture in said side wall surface communicating with the interior of the rotor and being encircled by the-valving seal means so that the rotor and the housing jointly define a plenum sealed by the valving seal means, and there being defined by the rotor and the housing a plurality of distinct working chambers each radially outward of the chamber-isolating seal means and lying between adjacent apices, which move about the first axis and successively increase and decrease in volume with said movement of the rotor;; passage means for the working fluid said passage means communicating through the hollow rotor between the outside of the housing and the inside of the housing at a site inward of the valving seal means; bridging passage means in the inner surface of one or each of said end walls, located and sized to conduct working fluid between the plenum and the working chambers during first predetermined portions of said movement; and further passage means in said inner surface of said one or each of the end walls for affording fluid connection with the working chambers during second predetermined portions of said movement.

5. A rotary machine according to any

of the preceding claims, which has means connected in driven relation to said crankshaft for taking mechanical energy of rotation therefrom.

6. A rotary machine according to Claim 1, in which the first named means comprises an eccentric revolvable about said first axis and engaging the rotor for relative rotation about said second axis, a first gear fixed in the housing concentric with said axis, and a second gear fixed to the rotor and meshing with the first gear.

7. A rotary machine according to any of the preceding claims, in which said seal means extends around a side wall surface of the rotor with the inlet valving seal means nearer said second axis than the working chamber seal means, said first passage means always extending outwardly past the working chamber seal means, but extending inwardly past the inlet valving seal means during said first predetermined portions of the movement.

8. A rotary machine according to any of the preceding claims, in which said seal means extends around a side wall surface of the rotor with the inlet valving seal means inwardly nearer said second axis than the working chamber seal means, said first passage means always extending outwardly past the working chamber seal means during said second predetermined portions of the movement.

9. A rotary machine according to any of the preceding claims, which has means momentarily operable to supply pressure fluid directly to at least one of the working chambers of the cavity.

10. A rotary machine according to any of the preceding claims, which is a rotary expansion steam power unit.

11. A rotary machine according to any of the preceding claims, arranged to operate as a power unit.

12. A rotary machine according to any of Claims 1 to 4 and 6 to 11, arranged to operate as a gas compressor.

13. A rotary machine according to any of the preceding claims, substantially as described herein with reference to Figures 1 to 6 of the accompanying drawings.

14. A rotary machine substantially as described herein with reference to and substantially as shown in Figures 1 to 5 of the accompanying drawings.

15. A compound rotary machine which comprises in combination two or more rotary machines as claimed in any of the preceding claims and substantially as described herein with reference to the accompanying drawings.

16. A compound rotary machine substantially as described herein with reference to and substantially as shown in Figure 7 of the accompanying drawings.