IE880639L - Rotary vane fluid device without any internal sealing gasket - Google Patents

Abstract

The invention relates to a fluid-operated rotary-vane device (actuator or pump), comprising a casing (3) traversed by a rotary shaft (1). A double vane (6, 6'), capable of rotating with the shaft, and two fixed partitions (5, 5') determine inside the casing two chambers (4a1, 2, 4b1, 2) of a complementarily variable volume. The vane is formed by a parallelepipedal bar attached to the shaft (1), which shaft is entirely cylindrical. The partitions (5, 5') are integral with a cover plate belonging to the casing. A very low level of inter-chamber leakage is maintained without an internal seal. <IMAGE>

Description

60733 r? C The present invention relates to a rotary vane fluid device for use either as a motor (rotary actuator), or as a receiver (reciprocating action pump), comprising a fixed casing having a shaft passing therethrough, which shaft is rotatable about 5 its axis and carries said vane8 whereas the inside space of the casing, forming an annular volume of revolution about the shaft has a section in a radial plane which is rectangular and which is delimited by two plane annular base surfaces and by two co-axial cylindrical surfaces, respectively constituting an inner and an 10 outer surface, is divided into two chambers of complementarilv variable volume by a radial partition, which is fixed with respect to the casing, and by said vane9 movable in rotation with the shaft. Said latter is machined in such a manner as to have a thickness - in the axial direction of the shaft - which is equal, 15 to within a small clearance, to the distance between the two plane annular surfaces delimiting the annular space in that same direction, as well as a length and cylindrical shape of its ends which are such that, once the vane is mounted on the shaft, the surface of its end is situated on a cylinder of revolution co-20 axial with the shaft and having the same radius, to within a very small clearance, as that of the cylindrical surface delimiting externally the annular space, and the partition is machined so as to have a thickness - in the direction of the axis - equal, to within a very small clearance, to the distance 25 separating said two annular surfaces, as well as a cylindrical shape of its edges radially adjacent to the shaft and to the casing such that, after assembly of the component parts of the devices the surfaces of said edges are situated on cylinders of revolution co-axial to the shaft, * ar ;30 Devices of this type, in particular devices usable as rotary actuators, are known, in which said vane and partition are ^ ;provided with respective sealing gaskets in order to prevent any fluid leakage (gas or hydraulic fluid) between the chambers. ;The presence of such internal sealing gaskets gives rise to several drawbacks: subject to wear, they can cause drifts in the duration of the performances of the device, while polluting the fluid used; in addition, they constitute specially shaped members which are complex to assemble and inspect, and which are high in price. ;It is important to reduce as much as possible, any fluid leakage between the chambers which would necessarily affect the accuracy and the hydraulic stiffness of the device. The internal leakage phenomenon must therefore be brought under control in order to limit its magnitude and to reduce dispersion in a series of devices. ;It is the object of the present invention to improve a fluid device of the type under consideration so as to enable it in spite of the omission of any internal sealing gasket, to keep leakage between the chambers to a very low and well defined level, with a pressurized fluid which may be liquid or gaseous, notably by creating precise clearance between the different elements of the device, and by creating leakage lines as long as possible. ;To this effect the device according to the invention is characterized by the fact that its component parts are made of a single material, that the casing is composed of a one-piece bell-shaped body and of an end plate applied to the body, that the fixed partition is formed integrally with the end plate, the surfaces of the cylindrical edges of said partition having radiuses which are respectively equal, to within a very small clearance, to the radiuses of the inner and outer cylindrical surfaces delimiting the annular space, that the shaft has, at least in the portion thereof extending inside the casing and into the bores provided in said casing for the shaft to pass through, a cylindrical lateral surface of constant diameter, and that the vane is constituted by the end of a bar of substantially parallelepipedic shape assembled on the shaft, and mounted in a housing formed in the latter, the lateral surface of the shaft being evlindrically machined before the vane is mounted, so that. ;in the assembled device, the vane and the partition provide small, predetermined and stable fluid leakage between the two chambers of the annular space without the addition of sealing gaskets, that the end plate comprises, co-axially surrounding the central bore allowing the shaft to pass therethrough, a first plane annular surface which forms one of the base surfaces of the annular space and from which projects the partition, delimited radially by the surfaces of radiuses respectively equal to the limiting radiuses of said first annular surface, the latter being surrounded by a second plane annular surface, against which rests the body after assembly, the assembled body and end plate sharing the same axis which coincides with the axis of the shaft, and that the first annular surface of the end plate is axially offset relative to the second annular surface, said two annular surfaces being interconnected by a circularly cylindrical shoulder over which the bore of the body which defines the outer cylindrical surface delimiting the annular space, fits exactly. ;In the assembled device, the vane and the partition, without requiring sealing gaskets, ensure negligible fluid leakage between the two chambers of the annular space. Moreover, the fact of using a shaft and a vane which are constituted by two distinct parts, enables to ensure that the shaft has an extremely accurate circularly cylindrical surface, which is not possible when the shaft and the vane are made as a single piece. Further, this same characteristic means that the edges of the re-entrant angles which appear between the surface of the shaft and the two faces of the vane extending perpendicularly to the axis of the shaft can be given exact geometrical shapes, whereas a re-entrant angle cannot be accurately machined in a single piece. That is why it has been observed that leaks located at the interconnecting edges or at the discontinuities between the surfaces of the components of a rotary vane device are the most difficult leaks to control. The danger of localized leaks is limited by making the shaft and the vane as two assembled parts, while simultaneously simplifying the shapes of these two parts. ;5 ;The disposition according to which the first annular surface of the end plate is axially offset relative to its second annular surface, with these two surfaces being interconnected by a circularly cylindrical shoulder over which the first bore of the body fits exactly, ensures extremely accurate mutual positioning between the body and the end plate. Further, given that it implies that the re-entrant angle situated at the root end of the partition is at a distance from the chambers, it considerably reduces the influence of possible leaks that could occur at this location. ;The fact that the shaft, at least in its portion which extends inside the casing and through the shaft-passing bores in the casing, provides a cylindrical lateral surface which has the same diameter throughout, results in a simplicity of shape which contributes to eliminating leaks or their effect between the chambers. ;Further, it is appropriate for the lateral surface of the shaft and for the surfaces of the vane which face the base surfaces and the outer cylindrical surface of the annular space with very small clearances to be coated with respective thin layers of an anti-adhesive coating. ;The shaft must be guided in the casing of the device by a pair of bearings suitable for ensuring that a rotary part is accurately positioned, such as smooth bearings, ball bearings having no radial play, hydrostatic bearing or passive or active magnetic bearings, the latter type of bearings being capable of providing the shaft with both radial and axial guidance. ;When the device includes, in a conventional disposition which is advantageous because of its symmetry, a second vane and a second partition identical to the above-mentioned vane and partition and disposed diametrically opposite them, each chamber is thus split into two diametrically opposite compartments between which is provided a respective communication channel through the shaft, the two vanes are, in accordance with the invention, constituted by the opposite ends of said bar which passes right through the shaft, while the second partition is shaped and ;0 ;disposed in the same manner as the first partition. Said bar may either be fixed to the shaft by means of a centering member, or else it may be slidably mounted in the shaft. ;The vane or each of the two vanes in the device may be made of composite material. The fact of producing the component parts of the device from the same material, enables it to operate over a large temperature range. ;By virtue of its special structure and the extremely simplified geometrical shapes given to its active surfaces, a device in accordance with the invention does not need to have an internal sealing gasket since the leaks between the chambers remain very low. As a result it operates without friction and without wearing its component parts, thereby providing excellent linearity and remarkable accuracy, and also giving very long service life with exceptionally stable performance. That is why it is particularly well adapted for use as a drive member in high quality position servo-control systems. ;Other characteristics and advantages of the invention will be more readily understood on reading the following description, given with reference to the accompanying drawings, of a non-restrictive embodiment. ;Figures 1 and 2 are diagrammatical cross-sections through fluid devices having one rotary vane and two rotary vanes, respectively. ;Figures 3 shows the Figure 2 device adapted to operate as a pumping device. ;Figure 4 is a cross-section through a device in accordance with the invention on a line IV-IV of Figure 5. ;Figure 5 is an axial section of the device along line V-V of Figure 4. ;Figure G is a perspective exploded view of the main component parts of the device shown in Figures 4 and 5, prior to assembly. ;Figure 7 is a perspective view of some of the parts shown in Figure 6„ after assembly. ;7 ;Figure 1 shows a rotary vane fluid device of the type under consideration. It comprises a shaft 1 capable of rotating about its axis 2 inside a coaxial cylindrical casing 3- Inside the casing there is an internal space 4 in the form of a rectangular 5 section circular ring delimited by the lateral surface la of the shaft lf by the surface of the internal bore 3a of the casing 3, and by two plane annular surfaces centered on the axis 2 and belonging to a pair of circular end plates, not visible in the drawing. The annular space 4 is divided into two chambers 4a and 4b 10 by a fixed partition 5 and by a moving vane 6 which rotates with shaft 1. The chambers 4a and 4b are connected to an external pressure fluid (hydraulic or pneumatic) circuit via orifices 7a and 7b formed through the side wall of the casing 3. It is clear that when fluid under pressure is applied to chamber 4a via orifice 7a, 15 with orifice 7b of the chamber 4b being connected to the exhaust side of the external circuit, then shaft 1 is rotated in the direction indicated by the arrow, with the angle of rotation being limited to about 280°. The device thus constitutes a rotary actuator. ;20 In the case shown in Figure 2. the shaft 1 has a second vane 6', with the two vanes 6 and 6® projecting from opposite ends of a common diameter of the shaft. Similarly, a second partition 5' is provided diametrically opposite the partition 5. Thus, each of the chambers 4a and 4b is split into two diametrically opposite 25 compartments respectively referenced 4al, 4a2 and 4bl, 4b2, with the two compartments of each chamber being interconnected by a corresponding duct 8 or 9 running through the shaft 1. This symmetrical disposition balances the action of the fluid under pressure on the shaft, but at the price of reducing the maximum 30 angle of rotation to about 100°. ;Either of the devices outlined above can operate as a motor (actuator) as mentioned with respect to the Figure 1 device. Since they are reversible, they may also be used as receptors (pumps or compressors). For example. Figure 3 shows a double action 35 pump circuit using the Figure 2 device, and provided in addition ;with two complementary orifices 7'a and 7'b opening out into the chamber compartments 4a2 and 4bl. Each of the orifices 7a, 7b, 7!a and 7'b is associated with a non-return valve 10 which is mounted in the fluid circuit shown in such a direction that by applying a reciprocating rotary motion to the shaft 1, continuous suction effects are obtained at point A and continuous lift effects are obtained at point B of the fluid circuit. ;A device in accordance with the invention as described below with reference to Figures 4 et seq has the configuration shown in Figure 2 as is immediately clear on comparing Figure 2 with Figure 4„ It comprises a stator having a casing 3 and two partitions 5 and 5' together with a rotor having a shaft 1 about an axis 2 and a pair of vanes 6 and 6* which, together with two fixed partitions 5 and 5', defines two chambers each of which is split into two compartments that communicate through the shaft via ducts 8 and 9. These chambers extend in the annular space of rectangular section inside the casing 3 coaxially surrounding the axis 2 and delimited on the outside by the bore 3a in the casing 3, on the inside by the lateral surface la of the shaft 1, and axially by two plane annular surfaces 11 and 12 belonging to the casing 3 (Figure 5)„ The pair of vanes 6, 6' is constituted by a bar 13 of rectangular section whose length is equal to the diameter of the bore 3a, its ends being rounded to the radius of curvature of said bore. Said bar is mounted in a housing 14 passing diametrically through the shaft 1 (Figure 6) with dimensions such that it receives exactly the bar 13 (Figure 7).

As can be seen in Figures 5 and 6, the casing is made in two parts, which after assembly, are symmetrical about the axis 2 of the shaft 1: a body 15 which is bell-shaped and an end plate 16 which closes the space inside the body 15. Both the body 15 and the end plate 16 have respective central bores 17 and 18 allowing the shaft 1 to pass therethrough. The body 15 has another bore of larger diameter which constitutes the bore 3a delimiting the outside of the annular space inside the casing and disposed around the shaft 1. Between these two bores 3a and 17 there is a plane annular shoulder 11 which forms one of the base surfaces delimiting said space in the axial direction, with the other annular base surface 12 appearing on the end plate 16 around the bore 18. The annular surface 12 is surrounded by another plane annular surface 19 constituting an assembly flange, on which is applied the casing 15 by a plane annular surface 20 provided on the latter. The end plate 19 has holes 21 disposed in a ring around the axis 2 and extending parallel thereto, said holes being intended to receive bolts 22 for screwing into conjugate tapped holes 23 drilled in the annular surface 20 of the body 15, said bolts thus enabling the body 15 to be assembled to the end plate 16 in order to constitute the casing 3. In addition, an angular positioning peg 24 projects from the surface 20 of the body 15. The peg is received in a corresponding hole 25 drilled in the surface 19 of the end plate '16.

As can be seen more particularly in Figure 6, the partitions 5 and 5® are integral with the end plate 16 and are constituted by projections from the annular surface 12 extending parallel to the axis 2, with their radially inner surfaces 26 directly extending the surface of the bore 18 through the end plate. Further, the surface 12 is raised with respect to the surface 19 so that the cylindrical skirt of the body 15 surrounding the bore 3a is fitted around said raised surface 12, with the bore 3a being a close fit around a circularly cylindrical shoulder 26 which appears between the surfaces 12 and 19 by virtue of their axial offset position. Under these conditions, the radially outer surface 28 of the partitions 5 and 5' extends as a direct extension of the cylindrical surface of the shoulder 26.

The main operations required to produce the component parts of the device described above are now explained. All of these parts are made of steel and share an axis of symmetry which, once they have been assembled, coincides with the general axis 2 of the device.

A bar 13 is machined so as to have the desired £ x Jd rectangular section for constituting the pair of vanes 6 and 6' (where £ is the circumferential dimension and is the axial dimension, i.e. the dimension parallel to the axis 2 about which the vanes operate after assembly). A blind hole 29 is drilled in the middle of one of the faces of dimension ja and the length of the bar is made slightly greater than the desired value by machining its end faces to take up a cylindrical surface about the same axis 2 as the hole 29. The ends of the faces of dimension lb are lightly milled at 30 so that in the assembled device the compartments 4al, 2, 4bl, 2 of the chambers have a non-zero minimum volume when the pair of vanes 6 and 6' is at either of its end-of-stroke positions (see Figure 4).

The shaft 1 is made in the form of a circular cylinder and the housing 14 is formed therein by electro-erosion having the same dimensions a x b as the bar 13 constituting the pair of vanes 6 and 6 - The bar 13 is inserted in the housing 14 through the shaft 1 and the bar is centered by means of a screw 31 engaged in a tapped hole 32 drilled axially from one of the ends of the shaft 1, said hole opening out into the housing 14 such that the non-threaded end 31a of the screw whose diameter matches the diameter of the hole 29 in the bar 13, penetrates into the hole 29 (Figure 5).

After the bar 13 has been assembled, its faces of width £ are polished so that the axial dimension is very accurate; similarly, the cylindrical end faces are finished so as to have the desired radius and so as to be exactly coaxial with the lateral surface la of the shaft 1.

Thereafter, the end plate 16 is made from a thick disk in which a central bore 18 is machined, having a diameter which is very slightly greater than the diameter of the shaft 1, then the annular surface 19 is machined, and the two partitions 5 and 5' are formed from the remaining central ring by milling followed by radial grinding using a grinding wheel whose thickness is equal to the dimension £ of the bar 13, while ensuring that the ring has a residual height £ (Figure 6) corresponding to the extent to which the annular surface 12 is to be offset axially, and with the partitions 5 and 5' projecting over a height h^ from said surface, where h^ is very slightly greater than the dimension b of the bar 13.

The body 15 is machined by making a bore 17 about the axis which will become the axis 2 of the completed device, said bore being identical to the bore 18 in the end plate 16, with these two bores serving as bearings for the cylindrical shaft 1. Then the bore 3a is machined having a diameter which is slightly greater than the outside diameter of the ring of the end plate from which the partitions 5 and 5! were machined together with the offset annular surface 12 so that said bore fits exactly around the shoulder 29 which delimits the outside of the surface 12 and whose diameter is very slightly greater than the diameter of the cylindrical ends of the bar 13. The two bores 17 and 3a interconnect via annular shoulder 11 whose radial extent is equal to that of the annular surface 12 of the end plate. The height h^ of the bore 3a between the planes of the annular surfaces 12 and 20 is very slightly greater than the dimension t) of the vane plus the engagement depth £ of said bore (Figure 5).

The surfaces of the component parts of the device which define the internal chambers are very accurately machined so as to be dimensioned to very small tolerances and so as to have an excellent surface state. As a result, the clearances between the various pieces may be very small, for example about 5 pm. However, the clearance between the faces of the vanes 6 and 6® which are perpendicular to the axis 2 and the annular surfaces 11 and 12 are slightly greater, about 10 jum, in order to avoid any contact between the vanes and the casing even if the shaft 1 is at a small angle relative to the axis 2 by virtue of the minimal clearances which exist between said shaft and its bearings constituted by the bores 17 and 18. All of these very small clearances, which have been considerably exaggerated in Figures 4 and 5 in order to make 12 them visible, ensure that there is substantially no fluid leakage from one chamber to the other within the device, even though no sealing gasket is provided between vane and casing, between partition and casing, or between casing and shaft. However, external sealing gaskets are provided. A sealing ring 33 provides sealing between the body 15 and the end plate 16. It is received in an annular groove 34 formed in the surface 20 where the body meets the end plate. Alsos two sealing rings 35 and 36 are inserted between the shaft 1 and the casing 3 in annular grooves formed respectively in the bores 17 and 18 (not shown in Figure 6).

By way of example, a device as described above and as shown in Figures 4 to 7 may have the following characteristics: - abutment-to-abutment angle of rotation: 100° O - unit cylinder capacity: 1 to 500 cm°/rad - available couple: 0.1 H„m. rad/cm°.bar - maximum feed pressure: 500 bar - hysteresis under load: < 0.1% —6 - static accuracy: 10 rad/N.m.

Claims (10)

1.IS CLAIMS 1„ Rotary vane fluid device for use either as a motor (rotary actuator) or as a receiver (reciprocating action pump), comprising a fixed casing having a shaft passing 5 therethrough, which shaft is rotatable about its axis and carries said vane, while the inside space of the casing, forming an annular volume of revolution about the shaft has a section in a radial plane which is rectangular and which is delimited by two plane annular base surfaces and by two co-axial 10 cylindrical surfaces, respectively constituting an inner and an outer surface, is divided into two chambers of complementarilv variable volume by a radial partition, which is fixed relative to the casing, and by the vane, movable in rotation with the shaft , device in which the vane is 15 machined in such a manner as to have a thickness - in the axial direction of the shaft - which is equal, to within a very small clearance, to the distance between the two plane annular surfaces delimiting the annular space in that same direction, as well as a length and cylindrical shape of its 20 ends which are such that, once the vane is mounted on the shaft, the surface of its end is situated on a cylinder of revolution co-axial with the shaft and having the same radius, to within a very small clearance, as that of the cylindrical surface delimiting externally the annular space, and the partition is 25 machined so as to have a thickness - in the direction of axis equal, to to within a very small clearance, to the distance separating said two annular surfaces, as well as a cylindrical shape of its edges radially, adjacent to the shaft and to the casing such that, after assembly of the 30 components parts of the device, the surfaces of said edges are situated on cylinders of revolution co-axial to the shaft, characterized by the fact that its component parts are made of a single material, that the casing is composed of a one-piece bell-shaped body and of an end plate applied to the body. 35 that the fixed partition is formed integrally with the end 14 plate , the surfaces of the cylindrical edges of said partition having radiuses which are respectively equal, to within a very small clearance, to the radiuses of the inner and outer cylindrical surfaces delimiting the annular space, that the shaft has, at least in the portion thereof extending inside the casing and into the bores provided in said casing for the shaft to pass through, a cylindrical lateral surface of constant diameter, and that the vane is constituted by the end of a bar of substantially parallelepipedic shape assembled on the shaft , and mounted in a housing formed in the latter, the lateral surface of the shaft being cylindrically machined before the vane is mounted, so that, in the assembled device, the vane and the partition provide small, predetermined and stable fluid leakage between the two chambers of the annular space without the addition of sealing gaskets, that the end plate comprises, co-axially surrounding the central bore allowing the shaft to pass therethrough, a first plane annular surface which forms one of the base surfaces of the annular space and from which projects the partition, delimited radially by the surfaces of radiuses respectively equal to the limiting radiuses of said first annular surface , the latter being surrounded by a second plane annular surface , against which rests the body after assembly, the assembled body and end plate sharing the same axis which coincides with the axis of the shaft, and that the first annular surface of the end plate is axially offset relative to the second annular surface , said two annular surfaces being interconnected by a circularly cylindrical shoulder over which the bore of the body which defines the outer cylindrical surface delimiting the annular space, fits exactly.

2. Device according to claim 1, characterized by the fact that it comprises a second vane and a second partition identical to said vane and partition and disposed diametrically opposite thereto, each chamber ! being thus split into two diametrically opposite compartments, between ' which is provided a respective communication channel through the shaft, the two vanes being constituted by the ends of said bar , which passes right through the shaft, while the second partition is shaped and disposed in the ^ same manner as the first partition a

3. Device according to claim 2, characterized by the fact that the bar is fixed to the shaft by means of a centering member „

4. Device according to claim 2, characterized by the fact 1q that the bar is slidably mounted through the shaft.

5. Device according to any one of claims 1 to 4, characterized by the fact that the lateral surface of the shaft as well as the surfaces of the vane situated opposite, with very little play, the base surfaces and •j 5 the external cylindrical surface of the annular space, comprise a thin layer of an anti-adhesive coating.

6. Device according to any one of claims 1 to characterized by the fact that the shaft is guided in casing by a pair of smooth bearings. 20

7. Device according to any one of claims 1 to characterized by the fact that the shaft. is guided in casing by a pair of roller bearings having no radial play.

8. Device according to any one of claims 1 to characterized by the fact that the shaft is guided in 25 casing by a pair of hydrostatic bearings.

9. Device according to any one of claims 1 to characterized by the fact that the shaft is guided in casing by a pair of passive or active magnetic bearings.

10. A device according to claim 1, substantially as 30 hereinbefore described with particular reference to and as il lustrated in the accompanying drawings. 5, the 5, the 5, the 5, the F. R, KELLY & CO., AGENTS FOR THE APPLICANTS.