Rotary vane hydraulic actuator

Abstract

 A rotary actuator for operation at fluid pressures in the order of 8000 psi utilizes a generally cylindrical housing (l0) with top and bottom flat portions to enable operation along the hinge line of a control surface forming part of a thin section wing. An output shaft (l8) passing through the housing (l0) and supported in endcaps (l2, l4) attached thereto is rotable over a range of up to about ± forty degrees and is moved by means of fluid pressure acting on a pair of diametrically opposed vanes (50, 52). A pair of elongated ribs (42, 44) are formed in the inside of the cylindrical housing (l0) opposite the flat portions which ribs (42, 44) have arcuate surfaces (46, 48) supporting the shaft (l8). Elongated dynamic seals (34, 36) are carried in the ribs (42, 44) which seal against the shaft (l8). The vanes (50, 52) constitute relatively thick lobes with arcuate surfaces (54, 56) movable adjacent the inside walls of the housing (l0). Elongated dynamic seals (66, 68) are carried in the internal housing walls and the endcaps (l2, l4) which seal against the arcuate surfaces (54, 56) and the end surfaces of the vanes (50, 52). Other dynamic seals (l05) are carried in the endcaps (l2, l4) which seal against the shaft (l8). An alternate embodiment (90) utilizes a single vane (l00).

Description

[0001] This invention relates to rotary vane hydraulic actuators and more particularly to such an actuator designed to operate within the confines of thin wings or control surfaces of modern aircraft.

[0002] A rotary vane actuator normally includes a housing connected to a source of fluid under pressure, a chamber within the housing, a shaft passing through the housing and vane members attached to the shaft and moveable in the housing in one direction or the other in response to directed hydraulic fluid under pressure to cause rotation of said shaft, usually over a limited travel such as ± forty degrees. A control surface may be attached to the shaft and movable therewith. Suitable seals must be employed to prevent excessive leakage and loss of power.

[0003] Such rotary vane hydraulic actuators are not new but have come into greater use recently because of advantages as compared with linear actuators for operating control surfaces of aircraft where the space available for the actuator is very limited. Because of the shape of an airfoil such as a wing, for example, it may be advantageous to incorporate a rotary vane actuator which can operate along the hinge line of a movable surface such as an aileron rather than a linear cylinder which may require increasing the thickness of the wing or adding protrusions to the wing to contain the actuator. Recent trends toward unusually thin wing construction for supersonic aircraft has made interest in the rotary actuator even greater because such protrusions or extra thickness adversely affect the performance of the aircraft. In the past, rotary actuators have been subject to the disadvantages of high fluid leakage losses and high manufacturing costs. Both of these problem areas have been largely related to the number and types of seals involved. With increased operating pressures, sealing problems have been magnified; nevertheless, there is great interest in operating aircraft hydraulic systems at 8000 psi or even higher pressure rather than the 3000 psi which is currently in general use. Thus there is a need for a rotary vane hydraulic actuator which is of such dimensions that it will fit in a thin section wing or control surface, which operates at 8000 psi or more while having tolerable fluid leakage losses and which is not excessively costly to manufacture.

[0004] The rotary vane hydraulic actuator of the present invention has a generally cylindrical housing having endcaps with flattened walls top and bottom to minimize its height and including a pair of elongated ribs internally of the flattened walls which have arcuate surfaces acting in cooperation with the operating shaft to effectively divide the internal chamber of the housing into what might be termed left and right chambers. The shaft carries oppositely directed vanes, one in each of the left and right chambers, which vanes are quite thick and have an arcuate surface of substantial length adjacent the internal walls of the left and right chambers. A pair of elongated dynamic seals are carried in grooves in the internal walls of the chamber and also in the endcaps such that they seal radially against the arcuate surfaces of the vanes and also axially against the end surfaces of the vanes. Other dynamic seals are carried in the arcuate surfaces of the internal ribs such that they seal against the shaft. Additional static seals are positioned between the housing and endcaps. Dynamic seals are also incorporated into the endcaps to seal against the rotatable shaft.

[0005] The high pressures which are used to operate the actuator tend to cause significant physical deformation such as distortion of the housing itself which complicates the sealing problems. Also, temperature effects tend to cause some variations in the clearances between the vane and the housing, yet the dynamic seals must remain effective. In the actuator described herein, the dynamic seals are carried in the housing and seal against the surfaces of the vanes and the shaft which have minimal distortion as a function of pressure differentials. The seals themselves are of flexible materials such as polytetrafluoroethylene (Teflon), filled Teflon, or polymides such as Vespel or Torlon which will maintain contact by their inherent characteristics or they may be augmented by means of additional spring-type expander members in the seal grooves to provide mechanical spring loading to assure contact with the vanes and shaft. The seals against the vanes are preferably single piece seals which have 90 degree corner projections to assure radial contact on the vane outer diameter and axial contact on the vane end faces. Sufficient end length interference must be provided to accommodate the differential expansion of the seal material and vane material over the required temperature range.

[0006] Advantages of the present invention are that it provides a vane type linear actuator which has a low height such that it can be placed along a hinge line of control surfaces of thin wing aircraft, it affords a sealing arrangement allowing for minimum leakage at high operating pressures despite physical distortion of the housing with pressure variations and yet the actuator is not excessively costly to manufacture.

[0007] The invention will now be described with reference to the accompanying drawings wherein:

Figure l is a sectional view of an actuator according to my invention;

Figure 2 is a sectional view taken along line 2-2 of Figure l;

Figure 3 is a sectional view taken along line 3-3 of Figure l;

Figure 4 is a sectional view taken along line 4-4 of Figure l;

Figure 5 is a partial sectional view of the actuator of Figures l and 2 showing details of the vane seals; and

Figure 6 is a partial sectional view of the actuator of Figures l and 2 showing details of the shaft seals.

Figure 7 is a sectional view of still another embodiment of my invention.

[0008] Refering now to Figure l, a generally cylindrical housing or barrel l0 is shown having endcaps l2 and l4 attached thereto by means of screws l6. A shaft l8 is supported in the endcaps l2, l4 which carry dynamic seals 22, 24 and 22ʹ, 24ʹ, respectively, consisting of combination O-rings and low friction rings in contact with shaft 20. A pair of static seals 26 and 28 are positoned between endcaps l2 and l4, respectively, and the cylinder barrel l0. Shaft 20 actually includes two concentric cylindrical parts including an inner splined output drive member 20 held in axial alignment with member l8 by means of wire retainers 30, 32. Alternatively, shaft 20 may be made of a single piece with a spline output. Carried in slots in barrel l0 and extending into the endcaps l2 and l4 are a pair of elongated shaft seals 34 and 36. These seals are preferably of a flexible plastic material having low friction such as polytetraflouroethelyne (Teflon or filled Teflon) or polymides (such as Vespel or Torlon). They may also be backed by metal springs 38, 40 if it is found that the barrel l0 distorts substantially under pressure such that there is excessive leakage past the seals 34, 36 Shaft seals 34 and 36 should preferably have an interference fit with or insert in grooves formed in additional ring seals l05 surrounding shaft 20 at each endcap.

[0009] Figure 2 is a cross sectional view taken along line 2-2 of Figure l. In this view it will be observed that barrel l0 is formed with parallel flattened surfaces top and bottom and that a pair of inwardly extending ribs 42, 44 are formed on the inside of the barrel directly opposite the flattened sides. Seals 34 and 36 are carried in longitudinal grooves in ribs 42, 44 which have arcuate surfaces 46, 48 respectively adjacent the surface of shaft l8 such that the seals 34, 36 seal against the shaft. Carried on shaft l8 and extending radially into the interior of barrel l0 are a pair of vanes 50, 52 which have considerable thickness and which terminate in arcuate surfaces 54, 56, respectively. Each of vanes 50, 52 serves to separate the half of the internal part of barrel l0 in which it is located into two chambers, vane 50 separating chambers 58 and 60 and vane 52 separating chambers 62 and 64. Located in the wall of barrel l0 are elongated dynamic seals 66 and 68 which seal against the arcuate surfaces 54 and 56, respectively. These seals are, or may be, essentially the same as shaft seals 34 and 36, and may also include metal spring members to assure contact against the surfaces 54 and 56 irrespective of internal pressures which may tend to distort barrel l0. Also visible in this view are the seal 26, described above and the several threaded holes for receiving screws l6.

[0010] Figure 3 is a sectional view taken along line 3-3 of Figure l and gives some detail of the endcap l2 and its internal passages. In this view is shown a boss 70 having an internal port 72 which is suitably connected to a conduit, not shown, from a source of operating fluid under pressure. Boss 70 communicates with an axially directed passage 74 which is connected to chamber 60 and also with channels 76 and 78 which communicate with a second axially directed passage 80 which communicates with chamber 62. The channels 76 and 78 are preferably located between shaft seals 22 and 24 or 22ʹ and 24ʹ. Passages 74 and 80 must be located away from shaft 20 so that they do no intersect with the seal grooves. With the inlet port 72 connected to the high pressure side of the fluid source and chamber 58 and 64 connected to a low pressure source as controlled by an external control valve, not shown, this pressure differential supplied to the chambers causes the vanes 50 and 52 to be rotated in a clockwise direction as shown in Figure 2. Endcap l4 is essentially identical to that described above but, as attached at the opposite end of the barrel l0, the ports 74 and 80 then communicate with chambers 58 and 64. When the external control valve is adjusted to port high pressure fluid into endcap l4, pressurizing chambers 58 and 64 and to vent chambers 60 and 62 to a low pressure source, the vanes 50 and 52 are caused to move counterclockwise.

[0011] Figure 4 is a schematic drawing showing an alternative porting arrangement for my rotary vane hydraulic actuator. In this view, which could be a cross-section taken along the barrel l0 of Figure l at any desired location such as along line 4-4 of Figure l, a pair of fluid passages 82 and 84 which communicate with a high pressure source are connected to chamber 58 and 60 respectively. A pair of non-intersecting diagonal ports 86 and 88 are drilled through a solid portion of shaft 20 such that high pressure in chamber 58 will be communicated through passage 86 to chamber 64 and at the same time passage 84 will communicate with the low pressure side of the fluid pressure source. This low pressure will also be communicated through port 88 with chamber 62 which would cause the vanes to move counterclockwise. Similarly, with high pressure in passage 84 and chambers 60 and 62 and low pressure connected to passage 82 and chambers 58 and 64, the vanes will move clockwise. With this arrangement the endcaps l2 and l4 will not include porting as described with respect to Figure 3. In this view it will be observed that barrel l0 is relieved at its internal surfaces on opposite sides of vane seals 66 and 68 to preclude possible binding of the vanes from thermal expansion and/or pressure distortion.

[0012] Figure 5 is a partial sectional view showing details of the vane seals and showing the manner in which the seal seals against the vane both along its axial length and against its ends. In this view the shaft l8 carries vane 50 which makes contact against seal 66. Seal 66 is carried in barrel l0 through its length and extends into slots 70 and 72 in endcaps l2 and l4, respectively, making 90 degree corner projections at the ends. As described above, the seal member 66 may be backed by metal springs or expander members to assure sealing contact against the vane despite some distortion of the barrel l0. Sufficient end length interference is provided to account for the differential expansion of the seal material and vane material over the required temperature range. This end section will also engage in an interference fit slot on seal rings l05 in the end caps l2 and l4 to provide axial sealing of the shaft, i.e. prevent leaking from one chamber to the adjacent chamber at the shaft ends.

[0013] Figure 6 is a partial sectional view similar to Figure 5, but displaced approximately ninety degrees to show details of the shaft seal 34 and associated structure. As described, seal 34 and back up springs or expander members 38 are carried in a slot in the longitudinal rib 34 which is part of barrel l0. Seal 34 extends into notches in ring seals l05 in endcaps l2 and l4 or otherwise makes an interference fit against the seals l05 to provide axial sealing as described above.

[0014] The above described actuator would typically be attached to the main shaft of a control surface forming part of a wing, for example, and would turn the output shaft over a range of up to about forty degrees. By providing the flattened top and bottom, the height of the actuator can be reduced substantially to fit within a thin wing or control surface. The longitudinal ribs 42 and 44 provide strength and stiffness to the barrel l0 while also providing means for sealing between operating chambers containing hydraulic fluid. The thick vanes 50 and 52 include arcuate surfaces of such length that the seals 66 and 68 maintain contact against the vanes at all travel positions of the vane.

[0015] Figure 7 is a sectional view of another embodiment of my invention utilizing a single vane. This embodiment can be made in a form having even less height for installation in thin section wings or control surfaces. In this embodiment, a housing 90 includes an internal cavity 92 which contains a rotatable shaft 94 effectively separated into chambers 96 and 98 by a single vane l00 carried on the shaft. Carried in housing 90 are a single shaft seal l02 and a single vane seal l04 which are of the same type and which seal in the same manner as do shaft seals 34, 36 and vane seals 66, 68. Vane l00 has a long arcuate surface as do vanes 50, 52 so that the sealing engagement is maintained over the entire travel of vane l00. A pair of ports l06 and l08 are connected to a control valve directing fluid under high pressure to chamber 96 and returning to the low pressure side of the fluid source from chamber 98 to cause clockwise rotation of the shaft 94, or directing high pressure fluid to chamber 98 and connecting chamber 96 to the low pressure return side of the source to cause counter-clockwise rotation of shaft 94. The vane seal l04 extends along the length of vane l00 and on the end faces as described with respect to Figure 5. The shaft seal is essentially as described with respect to Figure 6. Each of shaft seal l02 and vane seal l04 toe into a ring seal on the vane shaft as described above with respect to endcaps l2 and l4, but not including the porting described above. these endcaps also include slots which carry the ninety degree projections of the vane seals l04 which seal against the ends of vane l00. This single vane embodiment has a practical travel limitation of about ± eighty degrees rotation; however, it is most useful as a flat pack wherein the rotation is limited to not more than about ± thirty degrees from center. It will have higher friction than the two vane embodiment since it is not balanced around the center but will fit in some locations where the two vane actuator will not fit.

[0016] Those skilled in that art will recognize that the above described actuators offer several advantages. Although they have a low height to fit into thin wing sections, they may be made comparatively long so that the high pressure will operate on a substantial area and provide a high actuating force. The use of only one or two vanes simplifies sealing problems and reduces costs. Where space requirements dictate, it is not impractical to make a two vane actuator with one vane longer then the other. By placing the longitudinal internal ribs opposite the flattened barrel portions, the barrel is strengthened in an area where it might otherwise be thin and subject to distortion. The vane seals and shaft seals are both dynamic seals which are carried in the stationary barrel and endcaps rather than on movable parts such as the vanes and these seals may be backed by spring members or expanders to force the seals into contact with the opposing movable surfaces despite any distortion in the housing which might be caused by the large operating pressure variations. It will thus be apparent that the above actuator, while having the desired limited height, is simple and rugged in construction, and provides an effective sealing structure to minimize fluid leakage losses despite operating a substantially higher fluid pressures than are currently in general use.

Claims

1. A rotary vane hydraulic actuator including a housing having a generally cylindrical internal chamber, endcaps covering each end of said housing, ports communicating said chamber with a source of fluid under pressure, a shaft passing through the center of said housing and supported in said passages, and radially extending vanes attached to said shaft and movable with said shaft in said housing.
    characterized in that said housing includes parallel flattened walls on opposite sides, elongated axially directed ribs are located in said chamber internally of said flattened walls, said ribs including arcuate surfaces adjacent the surface of said shaft and seals in said arcuate surfaces in contact with said shaft, said vanes extend on opposite sides of said shaft and include arcuate surfaces adjacent the walls of said internal chamber with seals in said chamber walls in contact with said arcuate surfaces and continuing against the end surfaces of said vanes, and sealing means positioned between said endcaps and said housing and between said shaft and the internal surfaces of said passages.

2. A rotary vane actuator as claimed in claim l wherein said arcuate surfaces of said vanes are of such length that said seals in the walls of said internal chamber remain in contact with said arcuate surfaces throughout the limits of travel of said vanes.

3 . A rotary vane actuator as claimed in claim 2 wherein said housing contains elongated axially directed ribs at the top and bottom of said internal chamber internally of said flattened walls.

4 . A rotary vane actuator as claimed in claim 3 wherein each of two vanes is attached to said shaft such that said vanes and said axially directed ribs effectively divide said internal chamber into four elongated compartments for receiving fluid from said source.

5. A rotary vane actuator as claimed in claim 4 wherein said endcaps include fluid passages connected to said source such that fluid will be connected to compartments at the top of one vane and the bottom of the other vane to cause said shaft to be rotated in one direction and to the bottom of said one vane and the top of said other vane to cause said shaft to be rotated in the opposite direction.

6. A rotary vane actuator as claimed in claim 5 wherein said seals in the walls of said internal chamber and in the arcuate surfaces of said ribs are carried in grooves and are held in contact against said arcuate surfaces of said vanes and against the surface of said shaft by means of loading members between the bottom of said grooves and said seals.

7. A rotary vane hydraulic actuator including a housing having a generally cylindrical internal chamber, endcaps covering each end of said housing including axial passages therethrough, ports communicating said chamber with a source of fluid under pressure, a shaft passing through the center of said housing and supported in said passages, and at least one radially extending vane attached to said shaft and movable with said shaft in said housing
    characterized in that said housing includes at least one elongated axially directed rib located in said chamber, said rib including an arcuate surface adjacent the surface of said shaft and a seal in said arcuate surface in contact with said shaft, said vane extends outwardly from said shaft and includes an arcuate surface adjacent the wall of said internal chamber with a seal in said chamber wall in contact with said arcuate surface and continuing against the end surfaces of said vane, and sealing means positioned between said endcaps and said housing and between said shaft and the internal surfaces of said passages.

8. A rotary vane actuator as claimed in claim 7 wherein said arcuate surface of said vane is of such length that said seal in the wall of said internal chamber remains in contact with said arcuate surface throughout the limits of travel of said vane.

9. A rotary vane actuator as claimed in claim 8 wherein said housing has parallel flattened walls top and bottom causing said housing to be of substantially greater width than height thus permitting said housing to be placed within a space whose internal height is significantly less than the width of said housing.

l0. A rotary vane actuator as claimed in claim 9 wherein said housing contains elongated axially directed ribs at the top and bottom of said internal chamber internally of said flattened walls.

11. A rotary vane actuator as claimed in claim l0 wherein each of two vanes is attached to said shaft such that said vanes and said axially directed ribs effectively divide said internal chamber into four elongated compartments for receiving fluid from said source.

12. A rotary vane actuator as claimed in claim ll wherein said ports communicate with two of said elongated compartments, and passages are formed through said shaft communicating each of said two elongated compartments with another of said elongated compartments diametrically across said shaft.

Drawing