Rotary piston and cylinder device having a dish ringed rotor

Abstract

A rotary piston and cylinder device (1) comprising a rotor (2), a stator (4), a rotatable shutter (3), the rotor and the stator comprising surface portions which define a chamber, wherein the rotor comprises a first surface portion (2A) and the stator comprises substantially two surface portions (4a; 4b′), and the two surface portions of the stator neighbour each other.

Claims

1. A rotary piston and cylinder device comprising: a rotor, a stator, a rotatable shutter, the rotor and the stator comprising surface portions which define a chamber into which the piston extends, wherein the chamber is a three-sided chamber defined by three surface portions as viewed in an axial cross-section of the chamber, wherein the rotor comprises a first surface portion and the stator comprises a second surface portion and a third surface portion of said three-sided chamber, and wherein the second surface portion and the third surface portion of the stator neighbor each other.

2. A rotary piston and cylinder device as claimed in claim 1 in which the second and the third surface portions are linear surface portions defining the chamber.

3. A rotary piston and cylinder device as claimed in claim 1 in which the axial cross-section of the chamber is taken along a plane that includes an axis of rotation of the rotor being disposed therein.

4. A rotary piston and cylinder device as claimed in claim 1 in which one of the second surface portion or the third surface portion of the stator, when viewed in the axial cross-section of the chamber, is substantially linear.

5. A rotary piston and cylinder device as claimed in claim 1 in which the second and the third surface portions, when viewed in the axial cross-section of the chamber, are each substantially linear.

6. A rotary piston and cylinder device as claimed in claim 1 in which the second and third surface portions, when viewed in the axial cross-section of the chamber, subtend an angle in range of 10 to 170 degrees.

7. A rotary piston and cylinder device as claimed in claim 1 in which the second and the third surface portions, when viewed in the axial cross-section of the chamber, are substantially orthogonal to each other.

8. A rotary piston and cylinder device as claimed in claim 1 in which the second and the third surface portions meet at, or are proximal to each other, at a junction region.

9. A rotary piston and cylinder device as claimed in claim 1 in which, when viewing the axial cross section of the chamber, the first surface portion of the rotor is curved.

10. A rotary piston and cylinder device as claimed in claim 1 in which the first surface portion of the rotor extends from or is proximal to a distal region of one of the second or the third surface portions of the stator, to or proximal to, a distal region of the other of the second or the third surface portions of the stator.

11. A rotary piston and cylinder device as claimed in claim 1 in which the second and the third surface portions comprise at least in part an annular surface portion and a cylindrical surface portion, respectively.

12. A rotary piston and cylinder device as claimed in claim 11 which the annular surface portion of the stator is substantially flat.

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. 1 is a perspective view of a rotary piston and cylinder device of a first type,

(3) FIG. 2 is an axial cross-section of the rotary piston and cylinder device in FIG. 1,

(4) FIG. 3 is a perspective partial view of the rotor of the rotary piston and cylinder device of FIG. 2,

(5) FIG. 4 is an axial cross-sectional view of a second type of rotary piston and cylinder device,

(6) FIG. 5 is a perspective partial view of the device of FIG. 4,

(7) FIG. 6 is an axial partial view of the rotor of the device of FIG. 4, and

(8) FIGS. 7 to 9 are axial cross-sections of further embodiments of the present invention in devices of the first type.

DETAILED DESCRIPTION

(9) Reference is made to the Figures which show various embodiments of a rotary piston and cylinder device of the type which comprises a rotor, a stator, and a rotatable shutter, and can be adapted for various operational guises. The stator and the rotor comprise surface portions which define a (generally) annular chamber through which a piston attached to the rotor passes. The shutter provides a partition in the chamber, and has a slot which allows the piston to pass therethrough, without baulking. In the described embodiments which follow particular mention is made to the advantageous geometrical characteristics of the working chamber.

(10) Turning first to FIGS. 1 and 2, there is shown a rotary piston and cylinder device 1 of a first type, which comprises a rotor 2, a stator 4 and a shutter disc 3. FIG. 1 shows a stator of a rotary piston and cylinder device. The stator 4 comprises what may be termed an inner stator and an outer stator. The inner stator 4a is of substantially cylindrical form and defines an outer surface 4a′. The outer stator 4b is of substantially annular form and defines an inwardly facing surface 4b′.

(11) The stator 4 further comprises a slot 25 which is provided to receive the shutter 3, to divide the annular chamber, or cylinder space, 10 defined by the above mentioned surfaces of the rotor and the stator.

(12) A transmission assembly is provided to synchronise the rotation of the rotor 2 and the shutter 3. The transmission assembly comprises a shaft 14 and a toothed gear 15. Further gears (not shown) comprising a gearbox, or another means of transmission, can connect the toothed gear to the shaft 9, which thereby ensures that the shutter 3 rotates in synchrony with the piston.

(13) A port 7 is provided in the outer stator 4b. Other ports may also be provided in the stator or in addition to the port 7.

(14) FIGS. 2 and 3 shows the rotor 2, which comprises a dished or concave ring. The rotor 2 fits over the inner stator 4a to define an annular cylinder space 10. The rotor 2 is provided with a fluid port 16. The port 16 can correspond with a further port in a stator portion (not shown) which is located on the radially opposite side of the rotor to the annular cylinder space or working chamber 10, which comprises a structure arranged to be outermost of both the stator and the rotor, to form a valved port. Alternatively, another form of valving or porting may be used.

(15) Alternatively further ports in the rotor 2 or in the additional stator portion, described above, may be employed.

(16) In FIG. 3 it can be seen that the rotor 2 comprises piston 5. The piston is shaped so that it will pass through the slot 3a of the shutter, without bulking, and forming a seal therewith. The piston 5 comprises side surfaces 5a and 5b. The surface 5a opposes the surface 4b of the stator and forms a seal therewith, and the surface 5b opposes the surface 4a, and forms a seal therewith. By ‘seal’ we include allowance for a leak path of fluid, by way of the (close) spacing between opposing surfaces, and not necessarily forming a fluid-tight seal. For example, a seal may be achieved by way of a close-running line or close-running region between opposed moving surfaces.

(17) The chamber 10, as seen in FIG. 2, comprises the curved rotor surface 2a, and the two stator surfaces 4a′ and 4b′. As can be seen, in cross-section, the stator surfaces 4a′ and 4b′ can be non-curved and linear. Said stator surfaces 4a′ and 4b′ are arranged substantially orthogonally to each other, and meet at a junction region. Both of the chamber-defining stator surfaces 4a′ and 4b′ can be said to be located generally radially inwardly of the rotor 2. The chamber 10 may be referred to as a three-sided chamber, and has benefits which include:

(18) Reduced manufacturing/inspection costs due to the presence of only one junction region on the stator

(19) The surface area/volume ratio of the chamber is reduced to thereby advantageously maximise the volume available for use in the chamber.

(20) In more detail, for a given rotor 2, the linear cross-sections of 4a and 4b′ can be made possible by the relocation of the first transmission gear 15 away from the shutter disc 3. This is the first gear of the transmission means which synchronises the rotation of shutter disc 3 to rotor 2. Whereas in known devices it was located close to shutter disc 3 to reduce package size and shaft stiffness requirements, this can make it difficult to also have the linear surfaces 4a′ and 4b′ that enable a larger/maximised working chamber 10, and hence greater volumetric capacity of the device. Moving the first transmission gear to a position substantially outside the working chamber 10 and of the device in general allows for a larger swept volume 10, but also increases the length of the transmission (lower transmission stiffness, potentially greater backlash if more gears are required), and bulk of the overall machine. This means that the present invention can be more suitable, but not limited, to smaller machines.

(21) Easier assembly of the device is facilitated since the inner stator is not necessarily required to locate on another curved surface of the piston 5, as would be the case if the chamber were defined by an additional curved surface interface (between stator 4 and piston 5). Rather than resting the inner stator on said curved surface, it can rest on the flat surface 4b′ of the outer stator 4b. Radial alignment is achieved by the mating cylindrical surfaces 4a′ and cooperating surface of the rotor. This effectively removes the need to control and adjust an extra clearance as part of the assembly process.

(22) Turning now to FIGS. 4 and 5, there is shown a rotary piston and cylinder device 150 of a second type, comprising a rotor 102, a stator 104, and a shutter disc 103. The rotor 102 is mounted to rotate about an axis of rotation A-A. The stator 104, comprises formations 104a and 104b, such as a housings or casings, which are maintained relative to the rotor, and internal surfaces 104a′ and 104b′ of the stator facing a surface 102a of the rotor, together define an annular cylinder space or working chamber, shown generally at 100. The surface 104a′ can be described as being part of a substantially cylindrical portion of the stator, and the surface 104b′ can be described as being part of an annular end of the cylindrical portion. As can be seen, the two stator surfaces 104a′ and 104b′ are arranged substantially orthogonally to each other, when viewed in cross-section. It will be appreciated that the cross-section is taken on a radial plane, which includes the axis of rotation of the rotor A-A.

(23) Integral with or attached to the rotor and extending from the surface 102a there is provided a piston 105. A slot or opening 103a provided in the shutter disc 103 is sized and shaped to allow passage of the piston therethrough. Rotation of the shutter disc 103 can be geared to the rotor by way of a transmission means which may comprise gearing and which is arranged to ensure that the rotation of the rotor remains in synchrony with the rotation of the shutter disc. A possible geared component of the transmission means is shown by toothed gear 115. The shutter disc 103 is rotationally mounted by way of shaft 107 which may comprise portions on one or both sides of the shutter disc.

(24) In use of the device, a circumferential surface 130 of the shutter disc faces the surface 102a 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.

(25) The geometry of the surface 102a of the rotor can be governed by the circumferential surface 130 of the rotating shutter disc.

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

(27) With reference in particular to FIG. 5, there is shown a perspective view of the rotor and shutter arrangement, excluding the stator or housing (for ease of representation). As can be seen in both views, there is provided a shaft 109, which comprises end portions 109a and 109b, which extends through the rotor 102. To achieve this arrangement, the rotor 2 is provided with a central through-hole (not referenced). Advantageously, during assembly of the device, the rotor can be slid onto the shaft 109. The rotor 102, with the shaft in position in an assembly process, is then arranged to be fast with the shaft. The rotor 102 is located intermediate of the end portions 109a and 109b. Depending on the particular operational application of the device 150, the shaft may be used to provide rotational input or output.

(28) As is evident, since the piston 105 is of relatively wide dimension, the opening 103a of the shutter 103 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 103a is suitably configured/profiled, to take account of the relative movement between the piston and the shutter disc.

(29) The rotor 102 is provided with a port 110 which extends from the surface 102a through to the opposite, or what could be termed ‘rearward’ surface of the rotor.

(30) As will be described further below, this conveniently allows for fluid to flow into or out of the annular working chamber of the device, for example compressed fluid.

(31) With reference to FIGS. 4 and 5, depending from the part 104a, there is provided a formation 115. This feature provides a port, such as an outlet port, for working fluid from the device. The formation 115 comprises an opening, and the innards of the part 104a are configured to include a conduit or passageway 116 which communicates with the opening. The above described port 110 of the rotor 102 is arranged to periodically come into register with the passageway 116. As the rotor 102 rotates and the port 110 comes into alignment with the passageway 116 allowing continuous passage for fluid to flow into or out of the annular working chamber 100.

(32) During assembly or manufacture of the device 150, the parts 104a and 104b, can be rigidly attached together by way of fasteners or by other means

(33) The shaft 109 is rotatably mounted by bearings 120 is arranged to rotate about the rotational axis A-A. As alluded to previously, in addition to the porting provided by the passageway 116, typically providing an outlet port in a compressor arrangement, formed in the stator 104, there is also provided a port (not illustrated) which provides an inlet for working fluid. In use, a transmission between the rotor and the shutter ensures the required synchronisation therebetween. If the device 150 is used as a compressor, a suitable motive or drive source can be attached to an end portion 109a or 109b of the shaft 109.

(34) FIG. 6 serves to illustrate the geometric characteristic of the rotor 102 of the device 150. The surface 102a of the rotor 102 may be described as being asymmetric, or as being orientated at an incline. This asymmetry is with respect to a plane P-P, which extends through and bisects the rotor 102, at its mid-point 140. Its mid-point may be described as that which is midway between the distal end portions 112a and 112b, which define and bound the axial extent of the surface 102a. The plane P-P is also orthogonal to the axis of rotation A-A. It can be seen that the concave or curved in cross-section surface 102a 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 102a. It is thereby possible to determine an angle of orientation x between the tangent line T-T and the plane P-P. This angle is substantially 55 degrees.

(35) Other angles are possible, for example the angle could be between 20 and 70 degrees, or between 30 and 60 degrees.

(36) The transmission toothed gear 115 is spaced from the shutter disc 103, and this thereby allows a larger/maximised working chamber 100 (as can be seen from the modified opening 103a′ and piston 5), having the three sides 104a, 104b and 102a, on the same conceptual basis as described in relation to the above embodiments.

(37) FIG. 7 shows an alternative embodiment of a first type of rotary piston and cylinder device. Here the stator 4 is shown to comprise a single part, which forms two internal surfaces 4a′ and 4b′ in a similar fashion to the device shown in FIG. 2. The different orientation of the surface 4b′, however, allows for a greater volume of the working chamber 10 without alteration to the rotor 2 or other components of the assembly. This is achieved by the face 4b having a non-orthogonal orientation to face 4a′ when viewed in cross-section. Face 4b′ may be viewed as a frusto-conical surface around the axis of rotation of the rotor.

(38) FIG. 8 shows a further possible embodiment. Similarly to FIG. 7, one of the surfaces of the stator 4 which defines the chamber 10 can be thought of as frusto-conical. In this particular embodiment surface 4a′ is substantially frusto-conical and surface 4b′ is substantially planar 9 or straight in cross-section). This arrangement may be proffered to allow more space for transmission elements, such as gears, interacting with shaft 14 of the shutter disc 3.

(39) FIG. 9 shows yet another possible embodiment, which can be considered a variation of the device in FIG. 7. Here the stator 4 also comprises faces 4a′ and 4b′, but the face 4b′ is curved in cross-section. This can be considered to form a curved or dished annular surface. While such a surface can be more costly to machine and inspect, it allows for yet further volume increase of chamber 10 with minimal modifications to other components of the device.

(40) It will be appreciated that alternative embodiments, embodying the same underlying principles to those embodied in the examples above, may include a single curved surface, but more than two straight/linear profile chamber-defining surfaces (when viewed in cross-section). It will also be appreciated that these alternative embodiments may be incorporated in machines of the type seen in FIGS. 4 to 6.