Rotary piston and cylinder device with flared curved rotor surface

Abstract

A rotary piston and cylinder device comprising a rotor (2), comprising a rotor surface (2a), a stator (4), a rotatable shutter (3), a piston (5) which extends from the rotor surface, the rotor surface and the stator together defining an annular chamber, and the piston arranged to rotate, through the annular chamber, and the rotor surface being orientated at an incline to a plane (P-P) substantially perpendicular to the axis of rotation (A-A) of the rotor and the rotor surface faces generally away from, or outwardly of, the axis of rotation of the rotor.

Claims

1. A rotary piston and cylinder device comprising: a rotor, having a rotor surface, a stator, a rotatable shutter disc, the rotatable shutter disc provided with a slot, a piston which extends from the rotor surface, said slot of the rotatable shutter disc arranged to allow the piston to pass therethrough during operation of the device, the rotor surface and the stator together defining an annular chamber, and the piston arranged to rotate through the annular chamber, and the rotor surface faces away from, or outwardly of, an axis of rotation of the rotor, and the rotor surface is of a curved flared profile when viewed in axial cross-section, and said curved flared profile extends between a first rotor surface end region and a second rotor surface end region, and the first rotor surface end region being spaced along the axis of rotation of the rotor with respect to the second rotor surface end region, and one of the rotor surface end regions having a greater radial extent than the other rotor surface end region, and the rotary piston and cylinder device further comprising a transmission assembly having a toothed gear, the transmission assembly configured to maintain timing of the rotatable shutter disc in synchrony with the rotor.

2. A rotary piston and cylinder device as claimed in claim 1 further comprising a rotational shaft which extends from at least one of the first rotor surface end region and the second rotor surface end region.

3. A rotary piston and cylinder device as claimed in claim 2 in which the at least one axial end of the rotor comprises two axial ends of the rotor, and a second end of the rotational shaft extends from the other of the two axial ends of the rotor.

4. A rotary piston and cylinder device as claimed in claim 2 in which the rotor comprises a through opening through which the shaft extends or is received.

5. A rotary piston and cylinder device as claimed in claim 1 in which the rotor surface is provided with a port to allow communication of fluid between the annular chamber and a space external of said annular chamber.

6. A rotary piston and cylinder device as claimed in claim 5 in which the rotor has an end surface in the second rotor surface end region and the port comprises an opening which extends inbound towards the shaft, and an edge of the opening at the rotor surface is axially spaced from the end surface of the rotor in a direction of the axis of rotation.

7. A rotary piston and cylinder device as claimed in claim 1, wherein the rotatable shutter disc is provided with exactly one slot.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various embodiments of the invention will now be described, by way of example only, with reference to the following drawings in which:

(2) FIG. 1a is a perspective view of components of a rotary piston and cylinder device,

(3) FIG. 1b is a perspective view of the rotary piston and cylinder device components in FIG. 1 from a different orientation,

(4) FIG. 2a is an exploded view of the rotary piston and cylinder device of the preceding Figures,

(5) FIG. 2b is a perspective view of the assembled device from FIG. 2a

(6) FIG. 3a is an exploded view of the rotary piston and cylinder device of FIG. 2a from a different orientation,

(7) FIG. 3b is a perspective view of the assembled device from FIG. 3a

(8) FIG. 4 is an axial cross-sectional view of the rotary piston and cylinder device of FIGS. 2 and 3,

(9) FIGS. 5a, 5b and 5c are axial cross-sectional views of a rotor of the device of FIG. 4,

(10) FIGS. 6, 7A, 7B, 8A and 8B show various alternative embodiments, and

(11) FIGS. 9, 10, 11 and 12 are cross-sections of various embodiments of a rotor.

DETAILED DESCRIPTION

(12) Reference is made to the Figures which show a rotary piston and cylinder device 1 which comprises a rotor 2, a stator 4, and a shutter disc 3. The stator, although not shown in some of the Figures for ease of representation, comprises a formation, such as a housing or casing, which is maintained relative to the rotor, and an internal surface of the stator facing a surface 2a of the rotor, together define an annular space or working chamber, shown generally at 100. The stator 4 effectively comprises two portions, wherein said stator portions together substantially enclose the rotor and shutter therebetween.

(13) Integral with the rotor and extending from the surface 2a there is provided a piston 5. A slot or opening 3a provided in the shutter disc 3 is sized and shaped to allow passage of the piston therethrough. Rotation of the shutter disc 3 is arranged to ensure that the timing of the shutter remains in synchrony with the rotor by a suitable transmission.

(14) One of the geared components of a transmission assembly is shown by toothed gear 6. The shutter disc 3 is rotationally mounted by way of shaft portions 7a and 7b.

(15) In use of the device, a circumferential surface 30 of the shutter disc faces the surface 2a of the rotor so as to provide a seal therebetween, and so enable the shutter disc to functionally serve as a partition within the annular cylinder space.

(16) The geometry of the interior (i.e. facing into and in part defining the chamber) surface 2a of the rotor is governed by the part of the circumferential surface 30 of the rotating shutter disc.

(17) The rotor and the stator are configured to provide the annular cylinder space with one or more inlet port/s and one or more outlet port/s for the working fluid. One of the ports is described in more detail below.

(18) With reference in particular to FIGS. 1A and 1B, there are shown different perspectives the rotor and shutter arrangement, excluding the stator or housing. As can be seen in both views, there is provided a shaft 9, which comprises end portions 9a and 9b, which extends through the rotor 2.

(19) To achieve this arrangement, the rotor 2 is provided with a central through-hole (not referenced). Advantageously, during assembly, the rotor can be assembled onto the shaft 9 by any suitable method. This can be achieved for rotors such as rotor 2 due to the large axial extent of the rotor, which allows for accurate alignment and secure attachment using means such as brazing or an interference fit.

(20) The rotor 2, with the shaft in position in an assembly process, is then arranged so that relative movement to the shaft is prevented in operation. The rotor 2 is located intermediate of the end portions 9a and 9b. Depending on how the device 1 is used, in terms of its operational application, the shaft may be used to provide rotational input or output.

(21) As is evident, since the piston 5 is of relatively wide dimension, the opening 3a of the shutter 3 must be accordingly proportioned, in order to allow the piston to pass through the opening. It will be appreciated, and is to some extent evident in the drawings, that the boundary of the opening 3a has to be suitably configured/profiled to take account of the relative movement between the piston and the shutter disc.

(22) The rotor 2 is provided with an (internal) port 10 which extends from the surface 2a through to the opposite, or what could be termed ‘rearward’ surface of the rotor, since this extends away from the rotor surface 2a in a generally axial direction.

(23) As will be described further below, this conveniently allows for fluid to be transferred to or from the annular or working chamber of the device. This may be for example compressed fluid.

(24) Reference is now made to FIGS. 2, 3 and 4, in relation to the structure and configuration of the stator 4. As can be seen in FIG. 2, the stator 4 comprises two parts, 4a and 4b.

(25) As can be seen from FIGS. 2a and 3a, these two parts are brought together during assembly so as to house both the rotor and shutter disc. The stator part 4a can be seen as that part which accommodates both the rotor and the shutter disc. The part 4a is formed of two in part cylindrical portions which are arranged substantially orthogonal to each other.

(26) In this embodiment the two portions are integral, with the portion which receives the shutter disc 3 shown as 4a′. This part also includes a portion 4a″ which is arranged to receive a respective end portion 9a of the shaft 9, as well as a respective rotational bearing 20.

(27) The part 4b includes a substantially cylindrical portion 4b″ which is arranged to receive a bearing 20 and the shaft end portion 9b.

(28) Depending from the part 4b, there is provided a formation 15, which in this example may be described as a spigot. This feature provides a port, such as an outlet port, for working fluid from the device. The formation 15 comprises a passageway 16, which forms a conduit between openings 16a and 16b. The opening 16b is provided on a face 17 of the part 4, and the above described port 10 of the rotor 2 is arranged to periodically come into register with the opening 16b.

(29) The surface 17 is arranged to face, and be in close cooperation with, the rearward surface (unreferenced) of the rotor 2.

(30) This means that as the rotor 2 rotates and the port 10 comes into alignment with the opening 16b, a passage is opened through which fluid can flow into and/or out of the annular chamber 100.

(31) During assembly or manufacture of the device 1, the parts 4a and 4b can be rigidly attached together by way of fasteners or by some other way.

(32) FIGS. 3a and 3b show the arrangement of the intersecting bores which are in the stator 4a, which conveniently, accommodates both passage of the piston as well as receipt of the shutter, and in combination form another port for fluid communicating fluid to the working chamber. In a compressor embodiment, this port can be an inlet port.

(33) The shutter and rotor are kept in synchrony by the transmission. The toothed gear 13 of FIGS. 2 and 3 shows part of such a transmission.

(34) Referring to FIG. 4, it can be seen that in the assembled condition, the rotor 2 and the stator 4 define the annular chamber 100. The shaft 9 being rotatably mounted by bearings 20 is arranged to rotate about an axis A-A. As alluded to previously, in addition to the porting provided by the passageway 16, typically providing an outlet port in a compressor embodiment of the device, formed in the stator 4, there is also provided a port (intersecting bores of FIG. 3) which in a similar embodiment provides an inlet for working fluid. In use, a transmission between the rotor and the shutter ensure the required synchronisation. If the device 1 is used as a compressor, a suitable motive or drive source can be attached to an end portion 9a or 9b of the shaft 9 or to the shaft 7 of the shutter means or to another part of the transmission.

(35) FIG. 5 serves to illustrate the geometric characteristic of the rotor 2 of the device 1. The rotor 2 may be described as being asymmetric. This asymmetry is with respect to a plane P-P, which extends through and bisects the rotor 2, at its mid-point 14. Its mid-point may be described as that which is midway between the distal end portions 12a and 12b, which define and bound the axial extent of the surface 2a.

(36) The plane P-P is also orthogonal to the axis of rotation A-A. It can be seen that the concave (in cross-section) surface 2a is asymmetrical about the plane P-P. The rotor surface itself, as indicated by the arrow, faces generally away and outwardly of the axis of rotation A-A. A measure of the angle of orientation can be determined by taking a tangent T at the point of intersection between the plane P-P, and the rotor surface 2a. It is thereby possible to determine an angle of orientation x between the tangent line T-T and the plane P-P.

(37) As an alternative way to describe the inclined, outward, orientation of the rotor surface 2a, reference is made to FIG. 5b. A straight line V is generated between the distal end regions 12a and 12b of the rotor surface 2a, and angle of inclination of the rotor surface could be determined by considering the angle between the connecting line V, and the axis of rotation A-A by extrapolating the line V, as shown in the Figure, and determining the subtended angle of incline z.

(38) Yet a further way to consider the orientation of the rotor surface 2a is shown in FIG. 5c. In FIG. 5c a cross section plane G (on which the cross-section of the Figure is shown) is a generating plane, which is the plane on which the circular circumference of disk defines the surface 2a. A reference line L is then drawn on G, along its intersection with a plane normal to the rotor axis (which is coincident with the disk axis intersection point on the generating plane). A plane Q is a plane normal to G, coincident with the disk axis and the reference line L. In the preferred case of a perpendicularly positioned disk, Q is parallel to P (see FIG. 5b). The extent of the chamber is then defined on plane G by two angles (alpha1 and alpha2) about the shutter axis from L. An asymmetric working chamber may be defined as one where alpha1 and alpha2 are not equal. Alpha1 and alpha2 may be of opposite sense around L. As an example, the two angles may be 15 deg and 65 deg, respectively. However, more generally, the angles may be in the ranges alpha1: 0-30 degrees and, alpha2: 50-90 degrees, respectively. These ranges correspond to an angular range of 60 degrees to 25 degrees for angle z described above.

(39) There are numerous and significant advantages of the device described above.

(40) Having a port or ports through the rotor communicating with a further port or ports in the stator allows fluid flow to or from the annular chamber to be controlled or effectively valved.

(41) The device 1 allows for easier assembly of rotor and shutter disk. Since the rotor does not symmetrically wrap around the disk, the order of assembly can be achieved in more different ways such that the stator can be designed for lower cost and/or more accurate manufacture. For example, in some known piston and cylinder devices, the shutter disk has to be inserted radially with respect to the rotor. In device 1, the rotor can also conveniently be assembled along axis A-A onto the shutter disc.

(42) The device 1 allows for inclusion of a stiffer piston 5. Because the chamber 100 receives around 90° of the shutter (rather than around 45° in the prior art), the piston is better supported, so it is stiffer for a given thickness

(43) Since there is no need for the shutter disk to fit within the radial constraints of the annular chamber, the shutter and rotor can be sized independently (while achieving a desired working chamber volume), which gives design flexibility for relative component sizes and bearing loads, as compared to some known types of rotary piston and cylinder devices.

(44) A smaller rotor diameter for given chamber dimensions can be achieved. The rotor does not have to extend radially beyond the chamber, which means that for a given chamber cross-section and volume the maximum rotor diameter is smaller. This reduces cost, distortion during running, and reduces total machine size.

(45) Furthermore, due to the design flexibility as described above, the chamber can be designed to have a larger cross-section and hence a smaller outer diameter for a given chamber volume. This in combination with the immediately preceding point above means that the rotor can have a significantly lower outer diameter than possible with known rotor designs.

(46) In relating to existing devices, reduced bearing loads can also be achieved. The chamber has a lower surface area to volume ratio.

(47) This means that the forces exerted by the working fluid (due to its pressure being different to external or atmospheric pressure) will generally be lower. Specifically, the axial and radial forces exerted on the rotor may be reduced.

(48) Since the rotor structure is now (generally) internal of the chamber, with no need for any other recesses once assembled, it can be made much stiffer. This can be seen as a reduction in the length of thin-walled sections on the rotor. A stiffer rotor means less deformation during running, which can reduce the clearances around the working chamber during operation and can reduce the amount of leakage of working fluid.

(49) Reduced bearing loads. In addition to the reduced forces exerted by the working fluid, the rotor design allows a bearing to be simply placed on either side of the chamber, whilst known rotor designs require the chamber to overhang the bearings. This greatly reduces the bearing loads, increasing service life and/or reducing the size/cost of bearings.

(50) Reduced leakage. Due to the reduced surface area/volume, as outlined above, the leakage paths have a smaller extent for a given chamber volume.

(51) Reduced maximum casting dimensions, from simpler and smaller parts, assuming the main rotor and housing parts are cast, which can reduce the cost of casting by enabling the use of smaller machines. The machining cutting speed can also be faster (or tolerance can be finer), as it can be simpler to support the rotor closer to the machined faces.

(52) The rotor can be press-fitted to the shaft or otherwise assembled to the shaft as mentioned above, which reduces manufacturing complexity as the two constituent parts can be simpler to manufacture than if made as a single component. This assembly also allows the rotor and shaft to employ different materials in their construction.

(53) Reference is made to the remaining Figures which show some examples of variant embodiments, but all still embodying the same principle as that described above. Firstly, reference is made to FIG. 6, which shows a variant transmission toothed gear 106 is spaced from the shutter disc 3, and thereby allowing a larger chamber (as can be seen from the modified opening 103′ and piston 5′).

(54) FIGS. 7A and 7B show an alternative embodiment in which the rotor includes axial extensions 102a and 102b which can be used for enhanced sealing by provisioning a greater sealing area. Although the surface 102b may be geometrically continuous with surface 2a; 102b is not functionally a continuation of 2a as it does not define an aspect of the working chamber.

(55) FIGS. 8a and 8b show an embodiment where shaft 9 extends substantially only in one direction from the rotor. This means that it is required to be supported by bearings spaced only on that same side of the rotor. While this increases bearing loads for a given chamber, it may be advantageous in other ways, such as more compact bearing oil systems, or to distance the bearings from the generally increased temperatures around the working chamber.

(56) FIGS. 9, 10, 11 and 12 show variant embodiments of a rotor in which the rearward regions 150 of the rotor can be defined by undercuts, or spaces in that region, thus demonstrating that the rotor surface body need not necessarily be solid. The regions 150 may in part be defined by a rearward wall or face denoted generally by reference numeral 151. In FIG. 9 the rearward face 151 is substantially planar which is simple to machine and results in high stiffness, but increases the volume of port 110, which can lead to decreased performance. In FIG. 10, the rearward face 151 is of a similar curvature to the surface 2a, such that the rotor has a generally constant thickness. This can reduce the volume of port 10, but is more complicated to machine. In FIG. 11, the rearward face 151 is substantially frusto-conical, which is cheaper to machine (or can allow it to be repeatedly machined to a higher accuracy), while also minimising the volume of port 10. Finally in FIG. 12 the rearward face 151 is composed of both a frusto-conical and a planar portion. This serves to reduce the volume of port 10, reduce the cost of manufacture, and also to increase the stiffness of rotor 2, to better resist distortion.