Abstract
A rotary piston and cylinder device (1) comprising a rotor (2), a stator (4) and a rotatable shutter (3), a rotary piston and cylinder device comprising a rotor, a rotatable shutter, the rotor comprising a piston (5), the piston comprising a first side (5b) and a second side (5a), the first side (5b) arranged to seal with a slot of the shutter, and comprises a working face, the second side being a substantially oppositely directed side to the first side, and the second side (5a) comprising a sealing portion arranged to seal with the shutter slot and/or stator and a non-sealing portion arranged not to seal with the shutter slot.
Claims
1. A rotary piston and cylinder device comprising a rotor, a stator adjacent and maintained relative to the rotor, a surface of the stator facing a surface of the rotor to together define a working chamber, and a rotatable shutter at least partially located within the working chamber, the rotor comprising a piston extending from the surface thereof, the piston comprising a first side and a second side, the first side being arranged to seal with a slot of the shutter, and comprising a working face, the second side being a oppositely directed side to the first side, and the second side comprising a sealing portion arranged to seal with at least one of the shutter slot or the stator and a non-sealing portion arranged not to seal with the shutter slot.
2. The rotary piston and cylinder device of claim 1, wherein the sealing portion is a distal region of the second side.
3. The rotary piston and cylinder device of claim 1, wherein the non-sealing portion is devoid of a sealing or close-running surface, with respect to a surface of the slot of the shutter.
4. The rotary piston and cylinder device of claim 1, wherein the non-sealing portion is spaced from a respective slot-defining surface of shutter such that a close-running or sealing relationship is not achieved.
5. The rotary piston and cylinder device of claim 1, wherein the non-sealing portion comprises one or more openings.
6. The rotary piston and cylinder device of claim 5, wherein the one or more openings are provided in a distal region of the second side.
7. The rotary piston and cylinder device of claim 6, wherein the second side defines a recessed region or pocket or internal volume or void.
8. The rotary piston and cylinder device of claim 7, wherein the sealing portion at least in part defines the opening(s).
9. The rotary piston and cylinder device of claim 1, wherein the piston is at least in part hollow.
10. The rotary piston and cylinder device of claim 1, wherein the second side comprises a plurality of pores or is porous.
11. The rotary piston and cylinder device of claim 1, wherein the second side comprises a honeycomb structure.
12. The rotary piston and cylinder device of claim 1, wherein the second side comprises at least one heat exchange formation.
13. The rotary piston and cylinder device of claim 12, wherein the heat exchange formation comprises one or more rib or fin formations.
14. The rotary piston and cylinder device of claim 12, wherein the at least one heat exchange formation is arranged to perform a cooling effect to the piston.
15. The rotary piston and cylinder device of claim 1, wherein the second side includes one or more strengthening formations.
16. The rotary piston and cylinder device of claim 15, wherein the one or more strengthening formations comprise one or more ribs.
17. The rotary piston and cylinder device of claim 1, wherein the non-sealing portion of the second side is offset or set back relative to the sealing portion.
18. The rotary piston and cylinder device of claim 1, wherein the sealing portion of the second side comprises a peripheral region of the second side.
19. The rotary piston and cylinder device of claim 1, wherein the sealing portion comprises an edge portion or region of the second side.
Description
BRIEF DESCRIPTION OF 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,
(3) FIG. 2 is a cross-section of the device of FIG. 1, taken on a plane containing the rotational axis of the rotor,
(4) FIG. 3 is a perspective view of the device of FIG. 1, with the stator omitted,
(5) FIGS. 4a and 4b are perspective views of a rotor piston,
(6) FIG. 5 is a perspective view of an embodiment of a piston,
(7) FIG. 6 is a perspective view of an embodiment of a rotor, which includes a further embodiment of a piston,
(8) FIGS. 7a and 7b show perspective views of an embodiment of a piston,
(9) FIGS. 8a and 8b show perspective views of an embodiment of a piston,
(10) FIGS. 9a and 9b show perspective views of an embodiment of a piston,
(11) FIGS. 10a and 10b show a perspective and a cross-sectional view of an embodiment of a piston,
(12) FIGS. 11a and 11b show perspective views of an embodiment of a piston,
(13) FIGS. 12a and 12b show perspective views of an embodiment of a piston,
(14) FIGS. 13a and 13b show perspective views of an embodiment of a piston,
(15) FIG. 14 shows a perspective view of an embodiment of a piston,
(16) FIGS. 15a and 15b show perspective views of an embodiment of a piston,
(17) FIGS. 16a and 16b show perspective views of an embodiment of a piston,
(18) FIGS. 17a and 17b show perspective views of an embodiment of a piston,
(19) FIGS. 18a and 18b show perspective views of an embodiment of a piston,
(20) FIGS. 19a and 19b show perspective views of an embodiment of a piston.
(21) FIGS. 20a and 20b show perspective views of an embodiment of a piston.
(22) FIGS. 21a and 21b show perspective views of a piston of a further type of rotary piston and cylinder device.
(23) FIGS. 22a and 22b show perspective views of a piston from yet another type of rotary piston and cylinder device.
DETAILED DESCRIPTION
(24) Reference is made to FIGS. 1, 2 and 3, which show a rotary piston and cylinder device 1 which comprises a rotor 2, a stator 4, and a shutter disc 3, which can be can be configured for use in numerous operational guises.
(25) The stator 4, although not shown in FIG. 3 for ease of representation, but shown in part in FIGS. 1 and 2, comprises a formation, such as a housing or casing, which is maintained relative to the rotor, and a surface of the stator facing the surface 2a of the rotor, together define an annular cylinder space or working chamber, shown generally as 100.
(26) 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.
(27) Integral with or fixed to the rotor and extending from the surface 2a there is provided a piston 5. A slot 3a provided in the shutter disc 3 is sized and shaped to allow passage of the piston therethrough, without baulking. Rotation of the shutter disc 3 is geared to the rotor by way of a transmission assembly. The transmission assembly synchronises the rotation of the rotor 2 and the shutter 3. The transmission assembly comprises a toothed gear 150. Further gears (not shown) or other transmission, such as comprising a gearbox, to connect the toothed gear to the shaft 9, which thereby ensures that the shutter 3 rotates in synchrony with the piston. It will be understood that different forms/types of transmission to synchronise the rotation of the shutter and the rotor and piston are possible.
(28) The stator 4 further comprises a slot which is provided to receive the shutter 3, to divide the annular chamber, or cylinder space, 100 defined by the above mentioned surfaces of the rotor and the stator. 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.
(29) 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 working chamber.
(30) The geometry of the surface 2a of the rotor is governed by at least part of the circumferential surface of the rotating shutter disc. Since the shutter disc 3 penetrates/intersects only one side of the (annular) chamber, the axes of the disc and rotor will not generally intersect.
(31) The shutter 3 comprises a shutter slot 3a to allow the piston 5 to pass therethrough. The slot 3a is defined by surfaces 13, 14 and 15
(32) In the described embodiments which follow particular mention is made to the advantageous characteristics of the piston configuration.
(33) With reference in particular to FIG. 3, the rotor 2 comprises a dished, concave (in cross-section on a radial plane which includes the axis of the rotor) surface. The rotor 2 fits over the inner stator 4a to define the annular cylinder space 100. The rotor 2 is provided with a fluid port 16. The port 16 can correspond with a further port in a further stator portion (not shown) on the opposite side of the rotor relative to the annular cylinder space, to form a valved port. In this embodiment such a stator portion will be substantially radially outward of the rotor. Alternatively, another form of valving or porting may be used.
(34) In use, the shaft 9 is arranged to transmit torque to or from the rotor.
(35) The piston 5 may be considered to have a first side and a second side, each of the sides occupying respective positions with respect to the sense of rotation, and can be considered as oppositely facing in that regard. In the context of this particular embodiment of rotary piston and cylinder device, each side portion may be considered either as a leading/forward part and a trailing/reverse part, respectively, occupying distal regions of the piston. In the embodiments which are described below, particular attention is given to what may be termed the reverse or non-working side portion of the piston, and its structure and configuration. Furthermore, in relation to the embodiments described below, the same reference numerals are used where the same or substantially the same feature, or equivalent feature (from either a functional and/or structural perspective) is referred to.
(36) Reference is made to FIGS. 4a and 4b which shows a piston 5′, in which the working side is referenced 5b, and the reverse side 5a. In order to better understand the characteristics of the embodiments described below, FIGS. 4a and 4b are used to demonstrate the geometry of the sides of the piston to either effect or avoid sealing with, or be relatively close-running to, the shutter slot. The broken line of the side 5a illustrates the extent and configuration of that side if it were arranged to seal with respective slot-defining surface of the aperture of the shutter 3. As is evident, the reverse side is offset from that sealing position, towards the working side 5b. This means that as the piston passes through the slot of the shutter, the reverse side would not seal with the respective surface of the shutter slot 3a. However, the working side 5b, when passing through the shutter slot, forms a seal with the respective surface of the slot.
(37) The offset of the reverse side may often be required to prevent seizure of the piston inside the slot due to backlash (such as gear-tooth backlash or belt tension) of any transmission attached to the rotor, or to the shutter disc, or a transmission between the rotor and shutter disc.
(38) Backlash in gears, for example, can be present only temporarily during vibrations or unloaded cycles, but if there is no allowance for relative motion between piston and shutter disc then seizure or damage may occur during these conditions. It is possible to simply arrange for larger clearances between piston and slot on both working and reverse faces of the piston, such that seizure could never occur, but this would mean that for the majority of operating conditions the clearance between the working face of the disc and the respective surface of the shutter disc slot would be much larger, increasing leakage and reducing performance. The embodiment shown in FIG. 4 is to arrange for extra clearance required to accommodate the backlash to be on the reverse face of the piston (by way of the offset surface 5a). This way, timing between piston and shutter disc can be set at one extreme of backlash (which should be the predominantly expected operational backlash) and in the case of backlash being present at some point, it can be taken up by this clearance.
(39) By offsetting the entirety of face 5a, however, it can be seen that the sealing effect of faces 5c, 5d, 5e has been reduced due to the lower/shorter length, in the direction of piston motion, of their respective close-running lands. Since these faces are not likely to seize due to geartrain backlash like the opposing faces 5a and 5b, this reduction of sealing length does not have any counteracting benefit/effect.
(40) In the embodiments which follow, we have devised a way to maintain the long sealing lands of faces 5c, 5d and 5e (or any equivalently positioned surfaces), while at the same time reducing the likelihood of seizure between shutter disc and piston. This is achieved by having a greater extent of some or all of the distal regions of 5a, compared to the central region(s) of 5a. By central we include the region inwardly at least in part surrounding a marginal portion. The distal regions can preferably be those which are situated close to the perimeter or margin region of 5a along the sides that are not in contact with the rotor surface 2a. These regions are preferably those which are in close cooperation with the stator, and at a part of the cycle can be in close cooperation with the shutter slot.
(41) One additional benefit of this arrangement is that since the offset in the central region of the reverse face can be significantly larger than the required amount to accommodate backlash (since sealing between this portion and the shutter slot may not be important), this surface can be manufactured to a lower tolerance (as long as the offset at a given point on the surface is greater than the sum of expected backlash and maximum tolerance variation) than previously possible, which can reduce manufacturing costs. This offset may also allow other features to be incorporated into the piston without further disadvantage in terms of sealing or increased leakage.
(42) In all of the embodiments which are described below, at least a portion of the reverse side of the piston is configured not to seal with or run relatively close to the slot of the shutter for example by being formed as offset from its geometrically ideal position to do so, and a portion is arranged to run closer to the shutter slot with the further benefit that distal regions running closer to the shutter slot may also increase the length of at least part of the side regions or surfaces such as 5c, 5d, and 5e in the direction of travel of the piston to give potential sealing improvements.
(43) Reference is made to FIG. 5 in which a piston 25 is shown which is in part hollow, extending from an opening on the reverse side surface 25a. A pocket or void 28 is defined which extends from the reverse side, into the volume of the piston. The piston 25 is also provided with location features 29, which are fastener location features, such as blind bores, which allow the piston 5 to be surely attached to the rotor surface 2a. Face 25f is the face of the piston that is substantially in cooperation with rotor face 2a once assembled. The pocketed reverse face (maintaining the greater extent around all its peripheral surfaces 25c, 25d and 25e), advantageously provides a wide surface 25f facilitating bonding or fixing the piston to the rotor. The reverse side surface 25a is arranged to run closer to the shutter slot, and effectively defines a periphery which bounds the opening to void 28. Clearly, the opening forms a non-sealing and non-close-running portion of the reverse side.
(44) Turning to FIG. 6 this shows a rotor 2 which is provided with a variant hollow piston 35. As can be seen, the reverse side 35a is provided with an opening which extends into a void or hollow 38. The piston 35 further comprises surfaces 35c, 35d and 35e, which are arranged to seal, or preferably form a close-running arrangement, with respective surfaces of the inner and outer stator parts 4a and 4b. Similarly to FIG. 5, the reverse side surface 35a may seal or run relatively close to the shutter slot and the opening to the void 38 serves as a non-sealing portion. As with the previous and all following figures and embodiments it is understood that close running is a relative term when compared to other surfaces or regions and that a close running region or surface may still have substantial clearance to its opposing surface.
(45) In FIGS. 7a and 7b, a piston 45 is shown which comprises a reverse face or side 45a and additional faces or surfaces 45c, 45d, 45e, 45f, and which further comprises a rib 46 which defines two sub-chambers or voids 48a and 48b within the spatial envelope of the piston. The rib 46 is offset inwards (i.e. towards the working face) by constant amount. It will be appreciated that the side surface of the rib 46 could be viewed as providing a stepped back surface of the reverse side, with respect of the distal or ‘endmost’ surface 45a of that side. A significant volumetric proportion of the piston being hollowed advantageously allows for mass reduction. Although in this embodiment the rib is offset inwards by a constant amount, other embodiments are possible where the parts of the rib are offset inwards by a variable amount. Further the voids 48a and 48b may be completely separated or may be arranged to communicate at one or more regions.
(46) FIGS. 8a and 8b show a piston 55 which is somewhat similar to that shown in FIGS. 7a and 7b, with a reverse side surface 55a and additional faces or surfaces 55c, 55d, 55e, 57f, and the addition of ribs 57a and 57b to provide structural support, in particular to the surface 55d. The ribs and the rib 56, together define pockets or voids 58a, 58a′, 58b and 58b′ within the volume of the piston.
(47) FIGS. 9a and 9b show a piston 65 having a reverse side sealing surface 65a and additional faces or surfaces 65c, 65d, 65e, 65f. The reverse side surface is provided with apertures 66, which are in communication with a hollow interior volume 68 of the piston. The apertures 66 can create a resonant cavity inside the piston, which results in control/absorption of pressure pulsations (noise) in the working chamber 100 of the device (the portion of chamber that is in communication with features 65a and 66 at a given time). The apertures may also provide a way of further reducing mass of a hollow piston, advantageously with minimal effect on strength/stiffness. Furthermore, the apertures may also increase heat transfer between fluids on either side of the piston. It will be appreciated that the shutter slot will not form a seal with the openings 66.
(48) FIGS. 10a and 10b show a piston 75 which comprises a rearward sealing surface 75a and an additional face or surface 75b, and voids 78a and 78b, separated by partition 76. The rearward sealing surface 75a surrounds the opening to the void 78a and at that opening, sealing with the shutter does not occur. As can be seen in FIG. 10b, the surface 75f which faces rotor surface 2a once assembled, is formed partly by portion 76′. The provision of 76′ advantageously provides a wide area to achieve a high degree of bonding strength if the piston is attached to the rotor by brazing or adhesives or other similarly bonding method (of the surface 75f to the surface 2a of the rotor) rather than by way of mechanical fasteners. It can be seen that in this manner, a wide bonding area has been achieved, while reducing the chance of seizure due to the absence of the majority of surface 75a. Compared to FIG. 5, a stiffer piston is achieved due to the presence of partition 76.
(49) FIGS. 11a and 11b show a piston 85 with a porous (represented by a honeycomb-type structure here) interior 82. The porosity is shown to extend to the mounting face 85f. The piston 85 comprises reverse side surface 85a and additional faces or surfaces 85c, 85d, 85e. A ‘cut-out’ or recessed region 88 is provided adjacent to the porous interior portion and is set back or offset from the sealing surface 85a. This provides superior stiffness and lower mass compared to a hollow and solid piston respectively. The porosity features could be created by inserts into the casting, or purely by the casting method, or could be machined-in after casting. The porosity features need not be uniformly distributed. The porosity can be thought of as a further void within the piston.
(50) FIGS. 12a and 12b show a piston 95 which may be thought of as substantially devoid of a major reverse face with reverse surface 95a as well as additional faces or surfaces 95c, 95d, 95e, 95f, arranged to seal with or run relatively close to the shutter slot. This is best appreciated when comparing to the embodiment shown in FIGS. 7a and 7b in which the rib 46 is essentially omitted from this embodiment. The rearward surface of the rib provided an (offset) reverse surface of the piston. This, in the current embodiment, results in the creation of the large void 98. The piston 95 provides significant mass reduction and simplified machining.
(51) FIGS. 13a and 13b show a variant embodiment 105 of the piston shown in FIGS. 12a and 12b which comprises a structural rib 107 and reverse surface 105a as well as additional faces or surfaces 105c, 105d, 105e, 105f. The rib 107 assists in defining sub-chambers 108a and 108b. This increases stiffness of the piston, and provides additional space for additional location features 109, such as may be required when the piston subject to greater loading. This is just one example of a possible embodiment and in alternative embodiments further ribs or bosses may be employed.
(52) FIG. 14 shows a piston embodiment 115 which may be seen as a modified version of that shown in FIGS. 12a and 12b. The piston 115 includes a side surface 115a and further includes a mould gate 112a and rib 112b to help mould flow around the sharp change of direction, located within the hollow of the piston and which can be retained on the piston interior. Additionally, moulding by-products such as ejector pin recesses can be located on surfaces of a cavity inside the piston, and similarly do not need to be removed in further operations (which reduces cost and complexity of production) as they do not risk contacting a portion of the slot or stator. Alternatively, additional cast or machined features may be located within the hollow 118 of the piston to help mount the piston for manufacture or to form reference points or features for measurement of piston surfaces or regions.
(53) FIGS. 15a and 15b show a piston 125 which is provided with multiple spaced-apart fins 127. The distal reverse sealing side surface of the piston is shown by 125a, and the piston includes additional faces or surfaces 125c, 125d, 125e, 125f. The fins advantageously increase surface area for enhanced heat transfer between working fluid either side of the piston, through the piston. The fins can also have the effect of damping vibrations in chamber.
(54) FIGS. 16a and 16b show a piston 135, having faces or surfaces 135a, 135f, and in which a space 138 defined by the piston includes a high-stiffness structural insert 131 located between faces 138a and 138b. The piston can cast from a lower grade metal or material, which is then stiffened with the insert. This can significantly reduce the complexity and cost of producing the piston in its entirety out of the stiffer material (which may be more expensive and complex to process). The insert could be attached using fasteners or bonded using brazing or adhesives. It is noted that one or more inserts could be used and that many alternative shapes or forms of insert could be employed.
(55) FIGS. 17a and 17b show a similar concept in which the piston 145, having faces or surfaces 145a, 145f, comprises an insert 141 located in the space 148 located between faces 148a and 148b, and the insert includes a reverse facing surface. The insert could be made from cheap materials using low-tolerance methods such as injection moulded plastics, and could be used to provide an approximation to the geometrically-correct working face, at a lower mass and cost compared to the piston being made from the stiff material (e.g. metal) using a high-accuracy process throughout. The purpose of providing the insert could be to reduce the thermal transfer between the working fluid on either side of the piston. The reverse facing surface of insert 141 may be offset from surface 145a to give additional clearance to the disc slot.
(56) FIGS. 18a and 18b show a further embodiment 155 along similar lines in which a honeycomb or porous insert 151 is attached into the space 158 defined internally of the piston. The insert may provide additional stiffness, or may be included solely for the purposes of reducing the volume of void 158, or for additional vibration absorption.
(57) FIGS. 19a and 19b show a piston embodiment 165, having faces or surfaces 165a, 165f, in which a sensor means 161 is included inside the hollow volume 168 of the piston. Since the reverse side portion of the piston is substantially open, the sensor will have access to the fluid in the chamber, and for example could be used to monitor pressure, temperature, humidity or contamination. The sensor could be a passive heat-sensitive paint that could be externally observed using a camera. The sensor could further be an active electronic module or device, which could be powered by a range of power sources such as a battery, inductive power transfer from external source, a thermal gradient across it, vibration, or another method. Other sensing means could also be used.
(58) FIGS. 20a and 20b show piston 175, which can be considered a variation of piston 45 in FIGS. 7a and 7b and includes a rib 176 and voids 178a and 178b. In this case, a further part of the distal region of the rear surface 175a has been recessed or offset. Although the sealing effect across the resultant shorter surface 175d is reduced, its impact on this surface may be lower than of surfaces 175c and 175e. In this way further mass reductions can be possible while the sealing benefits on the full length surfaces 165c and 175e can still be utilised. In an alternative embodiment, further parts of the distal region of rear surface 175a could be recessed or offset which may reduce the sealing surfaces of part or all of 175c and or 175e.
(59) FIGS. 21a and 21b show piston 185, having surfaces or faces 185b, 185c, 185e and 185f, from a further embodiment of a rotary piston and cylinder device. This is used to illustrate how the present invention can apply to such types of piston. Piston 185 has fewer external surfaces due to a different configuration of the shutter slot and inner stator. It will be seen that the second side portion can still be defined as being opposite to the working face 185b of the first side portion, comprising the distal surface region 185a. The rib 186 can be seen to represent a large non-uniform offset from the respective surface of the shutter, and is present to increase stiffness of the piston. Fastener locating features 189 are present to assist attachment of the piston to the rotor.
(60) FIGS. 22a and 22b show piston 195 embodying the current invention in yet another embodiment of rotary piston and cylinder device. The piston can be seen to have a more elongated shape, but it will be understood that a working face 195b on a first side of the piston, a distally-arranged reverse face region 195a on a second side of the piston, and at least one other surface or face 195f, can still be identified in a similar manner. The void 198 is bounded by the distal region 195a.
(61) It will be clearly apparent from the description above that there are numerous significant advantages to ensuring that the reverse side of the piston does not seal with or run relatively close to the shutter, and also in providing that an internal volume of the piston is hollow. In particular, the realisation that the reverse side does not need to completely seal, or run close to, or only partially seal with the shutter slot at all regions of the reverse side, eases manufacture of the piston, and having relaxed that requirement, it has been realised that additional functional features can be incorporated with the piston, while maintaining the sealing and or structural performance of other surfaces.
