Rotary vane actuator and vane assembly

Abstract

A vane assembly for use in a rotary vane actuator, the vane assembly comprising: a rotatable vane having a first side and a second side; a vane axle connected to the rotatable vane for converting pressure exerted on the rotatable vane into rotational motion; a vane seal on the first side of the rotatable vane, the vane seal being for sealing the rotatable vane; and a side-plate on the first side of the rotatable vane, the side-plate clamping the vane seal in position; wherein the side-plate comprises: an outer part providing an outer surface of the side-plate, the outer part defining an internal volume; and an inner part filling or substantially filling the internal volume defined by the outer part, the inner part being distinct from the outer part.

Claims

1. A rotary vane actuator having a housing and a vane assembly, wherein: the housing has a cavity accommodating the vane assembly, the vane assembly dividing the cavity into a first chamber and a second chamber; and the vane assembly comprises: a rotatable vane having a first side and a second side; a vane axle projecting from the housing and being connected to the rotatable vane to convert pressure exerted on the rotatable vane into rotational motion; a vane seal on the first side of the rotatable vane, the vane seal providing a seal between the rotatable vane and the housing; and a side-plate on the first side of the rotatable vane, the side-plate clamping the vane seal in position; wherein the side-plate comprises: an outer part providing an outer surface of the side-plate, the outer part defining an internal volume; and an inner part filling or substantially filling the internal volume defined by the outer part, the inner part being distinct from the outer part.

2. The rotary vane actuator according to claim 1, wherein the internal volume defined by the outer part is a space in the outer part.

3. The rotary vane actuator according to claim 2, wherein the outer part is a hollow shell.

4. The rotary vane actuator according to claim 2, wherein the inner part is a separate insert positioned in the space in the outer part.

5. The rotary vane actuator according to claim 2, wherein the inner part is moulded in situ in the space in the outer part.

6. The rotary vane actuator according to claim 2, wherein the space in the outer part is exposed at an inner side of the side-plate.

7. The rotary vane actuator according to claim 1, wherein the outer part is made of a first material and the inner part is made of a second material that is different to the first material.

8. The rotary vane actuator according to claim 1, wherein the inner part has a lower mechanical strength and/or a lower density than the outer part.

9. The rotary vane actuator according to claim 1, wherein the outer part and the inner part are made of the same material.

10. The rotary vane actuator according to claim 9, wherein a structure of the material in the outer part is different to a structure of the material in the inner part.

11. The rotary vane actuator according to claim 9, wherein a density of the material in the outer part is different to a density of the material in the inner part.

12. The rotary vane actuator according to claim 1, wherein the inner part is made of a foamed material.

13. The rotary vane actuator according to claim 12, wherein the outer part is made of a higher density skin of the same material.

14. The rotary vane actuator according to claim 1, wherein the inner part occupies a larger volume of the side-plate than the outer part.

15. The rotary vane actuator according to claim 1, wherein the side-plate comprises a further part providing a further outer surface of the side-plate for contacting a stop, the further part being distinct from the outer part.

16. The rotary vane actuator according to claim 15, wherein the further part forms an end part of the side-plate.

17. The rotary vane actuator according to claim 1, wherein the vane assembly further comprises a seal expander positioned between the vane seal and the side-plate, wherein the seal expander is configured to contact and apply outward force to the vane seal to maintain the seal between the rotatable vane and the housing.

18. The rotary vane actuator according to claim 1, wherein the side-plate forms at least 25% by volume of the vane assembly.

19. The rotary vane actuator according to claim 1, wherein the vane assembly occupies at least 20% by volume of the cavity of the housing.

20. The rotary vane actuator according to claim 1, wherein the vane assembly further comprises: a second vane seal on the second side of the rotatable vane, the second vane seal providing a seal between the rotatable vane and the housing; and a second side-plate on the second side of the rotatable vane, the second side-plate clamping the second vane seal in position.

21. The rotary vane actuator according to claim 20, wherein the second side-plate comprises: a second outer part providing an outer surface of the second side-plate, the second outer part defining an internal volume; and a second inner part filling or substantially filling the internal volume defined by the second outer part, the second inner part being distinct from the second outer part.

22. A vane assembly for use in a rotary vane actuator, the vane assembly comprising: a rotatable vane having a first side and a second side; a vane axle connected to the rotatable vane for converting pressure exerted on the rotatable vane into rotational motion; a vane seal on the first side of the rotatable vane, the vane seal being for sealing the rotatable vane; and a side-plate on the first side of the rotatable vane, the side-plate clamping the vane seal in position; wherein the side-plate comprises: an outer part providing an outer surface of the side-plate, the outer part defining an internal volume; and an inner part filling or substantially filling the internal volume defined by the outer part, the inner part being distinct from the outer part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be discussed, by way of example only, with reference to the accompanying Figures, in which:

(2) FIG. 1 is an exploded view of a known vane assembly;

(3) FIG. 2(a) is a side view of the known vane assembly of FIG. 1;

(4) FIG. 2(b) is a cross-sectional view along the line A-A of FIG. 2(a);

(5) FIG. 3 is an exploded view of a rotary vane actuator including the known vane assembly of FIG. 1;

(6) FIG. 4 is a cross-sectional view of a rotary vane actuator including the known vane assembly of FIG. 1;

(7) FIG. 5 is an exploded view of a vane assembly according to a first embodiment of the present invention;

(8) FIG. 6(a) is a side view of the vane assembly of FIG. 1;

(9) FIG. 6(b) is a cross-sectional view along the line A-A of FIG. 6(a);

(10) FIG. 7 is a partially exploded view of a vane assembly according to a second embodiment of the present invention;

(11) FIG. 8(a) is a side view of the vane assembly of FIG. 7;

(12) FIG. 8(b) is a cross-sectional view along the line A-A of FIG. 8(a) according a third embodiment of the present invention;

(13) FIG. 9(a) is a side view of the vane assembly of FIG. 7;

(14) FIG. 9(b) is a cross-sectional view along the line B-B of FIG. 9(a) according to a fourth embodiment of the present invention;

(15) FIG. 9(c) is a cross-sectional view along the line C-C of FIG. 9(a) according to the fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND FURTHER OPTIONAL FEATURES OF THE INVENTION

(16) A vane assembly 39 according to a first embodiment of the present invention is illustrated in FIGS. 5, 6(a) and 6(b). In this embodiment, the vane assembly 39 is a modified version of the known vane assembly 1 illustrated in FIGS. 1 to 4 and described above, and therefore may have any of the features of the known vane assembly 1 described above.

(17) As shown in FIG. 5, the vane assembly 39 comprises a vane 40 that has a shaft 41 provided adjacent to an end of the vane 39 so that the vane 40 and shaft 41 are rotatable together about a central axis of the shaft 41. The vane 40 is generally in the form of a rigid paddle, and is made of rigid material.

(18) Typically the vane 40 is made of steel in a cast form, which may be machined in some areas. However, this is not essential.

(19) A first vane seal 43 is provided on a first surface of the vane 40. The first vane seal 43 is made of a flexible material such as polyurethane. The first vane seal 43 has a seal lip 45 around the outer periphery thereof. When the vane assembly 39 is positioned in an appropriate housing, so that the vane assembly 39 separates the housing into first and second cavities in a similar manner to the arrangement of FIG. 4, the seal lip 45 of the first vane seal 43 contacts an inner surface of the housing to form a seal between the vane assembly 39 and the housing that prevents, or substantially prevents, the leaking of pressurised fluid from the first chamber to the second chamber.

(20) A first seal expander 47, made from a springy material such as steel, is also provided. The first seal expander 47 is shaped to contact and apply force to an inner surface of the seal lip 45 of the seal 43, to keep the seal lip 45 in contact with an inner surface of the housing so as to maintain a good seal. The first seal expander 47 overcomes a problem of creep under stress of the seal material which may otherwise occur. However, the first seal expander 47 is not essential and can be omitted, for example where the seal 43 is made of a material having sufficient creep resistance.

(21) The first vane seal 43 and first seal expander 47 are clamped in position on the first side of the vane 3 by a first side-plate 49.

(22) The first side-plate 49 has a two-part (or two-portion) construction including an outer part 51 and an inner part 53.

(23) The outer part 51 is made of plastic, and is manufactured by injection moulding. However, in other embodiments the outer part 51 can be made differently, for example the outer part 51 may be moulded or formed of plastic or metal. The outer part 51 provides an external surface of the first side-plate 49 that comes into contact with pressurised fluid when the first side-plate 49 is used in a rotary vane actuator. The outer part 51 has sufficient strength to withstand pressures applied to the outer part 51 by pressurised fluid when the vane assembly 39 is used in a rotary vane actuator, and to withstand pressures applied to the outer part 51 when the first side-plate 49 contacts and is pressed against a stop in a cavity of a housing of the rotary vane actuator.

(24) As shown in FIGS. 5 and 6(b), the outer part 51 is substantially hollow and has an internal void 55. The internal void 55 is exposed on an inner surface of the outer part 51, so that the internal void 55 is accessible from the inner surface of the outer part 51. The outer part 51 therefore is in the form of a hollow shell (or part of a hollow shell) having a hollow opening that is (fully) exposed or open at a surface of the hollow shell.

(25) The inner part 53 is a separately formed insert or part that is shaped to correspond, or to substantially correspond, to the internal void 55 of the outer part 51.

(26) The inner part 53 is typically moulded, and may be made from plastic.

(27) As shown in the cross-sectional view of FIG. 6(b), when the vane assembly 39 is constructed the inner part 53 is inserted into the internal void 55 of the outer part 51 to fill, or substantially fill, the internal void 55 of the outer part 51.

(28) The resulting first side-plate 49 is substantially solid but has a two-part form.

(29) To increase the strength of the outer part 51, strengthening ribs may be provided in the internal void 55 of the outer part 51. In this case, the inner part 53 is shaped to accommodate and fit around the ribs.

(30) The first side-plate 49 has a shape for taking up more volume of a cavity of a housing of a rotary vane actuator than a simple flat metal side-plate. Specifically, as shown in FIGS. 5 and 6(b), the outer part 51 of the first side-plate 49 includes a protruding curved portion, or bulbous portion, 57 proximal to the position of the shaft 41. In the curved, or bulbous, portion 57 an outer surface of the outer part 51 is curved outwards, so that the overall volume of the first side-plate 49 is increased relative to a simple flat metal side-plate.

(31) In particular, the curved, or bulbous, portion 57 occupies space when the vane assembly 39 is at an extreme of its range of rotational motion that would otherwise be dead/empty space. Thus, the dead volume of the cavity is reduced, and in particular the ratio of the dead volume to the total volume or to the swept (displaced) volume is reduced.

(32) Thus, the volume of the cavity in the housing occupied by the vane assembly 39 is increased relative to a simple flat metal side-plate. This has an advantage of reducing a volume of pressurised fluid that needs to be supplied to the first or second chamber of the cavity to cause rotational movement of the vane assembly 39, because the empty volume of the cavity is reduced.

(33) Of course, the specific shape of the side-plate illustrated in FIG. 5 is not essential, and the side-plate may instead have a different shape.

(34) The inner part 53 fills the internal void 55 of the outer part 51 so that the resulting first side-plate 49 is substantially solid without any internal voids. Thus, there is no empty, or dead, space inside the outer part 51 that becomes filled with pressurised fluid during operation of the rotary vane actuator. This reduces the amount of pressurised fluid that is needed to cause the vane assembly 39 to rotate, and therefore increases the efficiency of the rotary vane actuator.

(35) The inner part 53 may be made of a same material as the outer part 51, or a different material. In practice, the inner part 53 is made from a lower cost material than the outer part 51, so typically the inner part 53 will have a lower mechanical strength and/or a lower density. The inner part 53 therefore provides low cost volume filling.

(36) A corresponding arrangement of a second vane seal 59, second seal expander 61 and second side-plate 63 is provided on an opposite second side of the vane 40. The arrangement on the second side of the vane 40 is a mirror image of the arrangement on the first side of the vane 40, and the descriptions given above of the first vane seal 43, first seal expander 47 and first side-plate 49 also apply to the corresponding second vane seal 59, second seal expander 61 and second side-plate 63. However, it is not essential to have this corresponding arrangement on the second side of the vane.

(37) As with the known vane assembly 1 shown in FIG. 1, the vane assembly 39 is held together using threaded screws and nuts. The parts are the same as in FIG. 1, and description thereof is not repeated for conciseness. Of course, other ways of holding the vane assembly together may be used instead, for example by providing studs or bolts and corresponding nuts.

(38) In the first embodiment, the inner part 53 is formed separately as a separate part and inserted into the internal void 55 of the outer part 51 to produce the first side-plate 49. In an alternative embodiment, the inner part 53 is instead moulded in-situ inside the outer part 51 to form the first side-plate 53, for example by pouring liquid material into the internal void 55 of the outer part 51.

(39) Various different materials can be used for the inner part 53 and outer part 51 in the first embodiment, and the present invention is not limited to the materials being plastic, or to the parts 51, 53 being formed by moulding. For example, the outer part 51 could alternatively me made of metal. Instead, it is only important that the outer part 53 has sufficient mechanical strength to withstand pressures applied to the side-plate during operation of the rotary vane actuator. The inner part 53 can have a lower mechanical strength, and therefore is typically made of a cheaper material that is weaker and lower density, to provide low-cost volume filling.

(40) As mentioned above, the outer part 51 of this embodiment includes strengthening ribs to increase the strength of the outer part 51. However, it is not essential for these strengthening ribs to be provided, and instead the outer part 51 itself may have sufficient strength.

(41) A second embodiment of the present invention is shown in FIG. 7.

(42) Some features which are the same as the first embodiment are shown with the same reference signs and description thereof is not repeated for conciseness.

(43) The second embodiment differs from the first embodiment in terms of the structure of the side-plate. In the second embodiment, the side-plate 65 comprises two different parts that each provide external surfaces of the side-plate 65.

(44) Specifically, the side-plate 65 comprises a main body part 67 and an end part 69. The end part 69 is positioned adjacent to the main body part 67 at an end of the side plate 65 opposite to the end adjacent to the shaft. A structure of the main body part 67 may be the same, or substantially the same, as the structure of the first side-plate 49 of the first embodiment discussed above. Alternatively, a structure of the main body part 67 may be as described in the embodiments discussed below.

(45) The end part 69 provides an external surface of the side-plate 65 that will contact a stop in the cavity of the rotary vane actuator. In practice, the part of the side-plate that contacts the stop will experience the greatest pressure, and therefore needs to be the strongest part of the vane assembly. Therefore, an end part 69 having a greater mechanical strength than the main body part 67 is provided at the end of the side-plate 65 to contact the stop.

(46) In this embodiment, the end part 69 is made of plastic and is manufactured by injection moulding. However, in other embodiments the end part 69 may be made of different materials, for example metal or plastic that is moulded or cast.

(47) The end part 69 is connected to the main body part 57. In this embodiment, the end part 69 is connected to the main body part 57 by the same screws (or bolts, etc.) that connect the side plate 65 to the rest of the vane assembly.

(48) FIG. 8 shows the structure of main body part 67 of FIG. 7 in a third embodiment of the present invention. In this embodiment, the main body part 67 has an outer part in the form of a thin shell 71. The thin shell 71 is a hollow shape having a thin outer wall that partially surrounds an internal hollow space of the thin shell 71. The thin shell 71 is filled by an inner part 73 that comprises material that is moulded in-situ in the thin shell 71 to fill the hollow space in the thin shell 71.

(49) The thin shell is made by moulding or casting, and may be made of plastic or metal.

(50) Thus, the resulting main body part 67 is a solid main body part 67 having a thin shell 71 outer part and an inner part 73 filling the hollow space in the thin shell 71.

(51) The material of the thin shell 71 is chosen to have a mechanical strength sufficient to withstand the pressures applied to the main body part 67 during operation of the rotary vane actuator.

(52) The inner part 73 can have a lower mechanical strength and therefore is typically made of cheaper, lower density material. In one example, the inner part 73 may be made of a foamed material. In another embodiment, the inner part 73 may be made of a non-porous material, i.e. a non-foamed material.

(53) As discussed above in relation to FIG. 7, the end part 69 adjacent to the main body part 67 contacts the stop. Thus, it is not necessary for the main body part 67 to be strong enough to withstand contacting the stop.

(54) In the embodiment of FIG. 8, the end part 69 is made from moulded plastic. In other embodiments the end part may be made from other materials, for example metal or plastic that is moulded or case.

(55) Of course, where the thin shell 71 has sufficient strength to withstand the pressures of contacting the stop itself, for example where the thin shell is made of metal or another material with sufficient mechanical strength, it is not essential for the end part 69 to be present, and instead the main body part 67 can form the whole, or substantially the whole, of the side plate.

(56) FIG. 9 shows the structure of the main body part 67 of FIG. 7 in a fourth embodiment of the present invention.

(57) In this embodiment, the main body part 67 comprises a solid foam inner part 75 completely surrounded by a higher density skin 77 of the same material.

(58) The solid foam inner part 75 provides low-cost space filling.

(59) The higher density skin 77 provides the necessary mechanical strength for the main body part 67 to be able to withstand the pressures applied to the main body part 67 during operation of the rotary vane actuator. For example, the higher density skin can be provided by over-filling a mould with foaming material, i.e. providing more foaming material than is necessary to provide a continuous foamed article, so that a non-porous, or substantially non-porous, skin or layer is formed at the surface of the moulded object.

(60) As in the previous embodiment, a moulded plastic end part 69 is provided that has sufficient strength to contact the stop during operation of the rotary vane actuator.

(61) As with the known vane assembly, the vane assembly of this embodiment is fixed together using screws and nuts. Alternatively, other connection methods such as studs or bolts and nuts may be used. In order to locally strengthen the material of the main body part 67 in the location of the studs or bolts of screws, where larger forces will be experienced, additional strengthening inserts 79 can be embedded in the main body part 67 to give higher strength locally under the fixing screws.

(62) Of course, where the higher density skin 77 has sufficient strength to withstand the pressures of contacting the stop itself, it is not essential for the end part 69 to be present, and instead the main body part 67 can form the whole, or substantially the whole, of the side plate.

(63) The vane assembly according to any of the embodiments of the present invention can be included in a rotary vane actuator as illustrated in FIGS. 3 and 4, so that the vane assembly is located in a cavity in a housing and separates the cavity into first and second chambers, as shown in FIG. 4.

(64) Where plastic is used in the present invention, for example for the moulded plastic end part 69, the plastic may be a low cost plastic capable of withstanding the typical environmental conditions experienced in the rotary vane actuator, for example Nylon.