Vane-type rotary hydraulic actuator device intended for driving an aircraft control surface

Rotary hydraulic actuator comprising a vane (1) which is mounted rotatably and sealingly in a chamber (2) made in a body (3) and on the faces of which a hydraulic fluid pressure is exerted, the vane being fixed mechanically to an element to be driven in rotation; the vane (1) comprises two parts (4, 5) extending radially on either side of its axis of rotation (XX), and these two parts are each movable in a chamber (8, 9) extending over an angular sector less than half a circumference, this chamber being divided into two compartments by the said part (4, 5); the actuator has a hydraulic circuit for feeding the chambers (8, 9), which is designed so as to be capable of driving the vane (1) in rotation in one direction or the other. This arrangement reduces the overall size of the actuator and increases its reliability.

The subject of the present invention is a rotary hydraulic actuator 
intended for driving in rotation an element, such as an aircraft control 
surface. However, this use is not restrictive, and this actuator can be 
put into effect for driving a wide variety of elements. 
The actuator with which the invention is concerned is of the type 
comprising a vane which is mounted rotatably and sealingly in a chamber 
made in a body and on the faces of which a hydraulic fluid pressure is 
exerted, the vane being fixed mechanically to the element to be driven in 
rotation. 
According to the invention, the vane comprises at least two parts extending 
radially on either side of its axis of rotation, and these two parts are 
each movable in a chamber extending over an angular sector less than half 
the circumference, this chamber being divided into two compartments by the 
said part, and the actuator is equipped with a hydraulic circuit for 
feeding fluid to the chambers, which is designed so as to be capable of 
driving the vane in rotation in one direction or the other. 
Thus, when the hydraulic pressure exerted on two opposite faces of the vane 
is higher than the pressure exerted on the other two faces, the vane 
rotates and drives in rotation the element fixed to its axle. 
This solution is useful for ensuring the direct driving in rotation of a 
shaft or a pivot, whenever this rotation is less than one revolution, as 
occurs particularly with regard to a control surface of an aircraft 
(aeroplanes, helicopters). 
In fact, in comparison with the devices known at the present time, its 
overall size is considerably less, all intermediate components, such as 
articulated connecting rods between the element to be driven and its 
control member, being omitted. 
In accompaniment with this, the invention provides greater reliability than 
the known systems. 
According to one embodiment of the actuator, the vane comprises four radial 
parts arranged at an equal angular distance from one another and rotating 
in four respective chambers, into each of which open an inlet conduit and 
an outlet conduit for the hydraulic fluid. 
According to another particular feature of the invention, the hydraulic 
circuit has feed conduits formed in the body and in the central hub of the 
vane. 
In one embodiment of the actuator, the hub has a shaft of a rotary 
distributor passing axially through it, on the periphery of which are 
formed passage grooves for the hydraulic fluid, and this shaft is designed 
to close off simultaneously the fluid-feed and fluid-return conduits when 
the distributor is in the position of equilibrium relative to the vane, 
whilst the rotation of this shaft through a specific angle puts the 
conduits of the body and of the vane hub in communication with one 
another, thereby causing a correlative rotation of the vane, with the 
position of the latter being subject to the new angular position of the 
shaft.

The hydraulic actuator illustrated in FIG. 1 comprises a vane 1 which is 
mounted rotatably about an axis X--X in a chamber 2 made in a body 3 and 
on the faces of which a hydraulic fluid pressure can be exerted. 
The vane 1 comprises 2 parts 4, 5 extending radially on either side of the 
axis of rotation X--X and a cylindrical central hub 6 integral with the 
two radial parts 4, 5. The hub 6 is in sealing contact with two radial 
protuberances 3a, 3b of the body 3, two gaskets 7 being received in these. 
The hub 6 and the protuberances 3a, 3b divide the chamber 2 into two 
compartments 8, 9, the cylindrical walls 8a, 9a of which extend over at 
least half a circumference and are in sealing contact with the ends of the 
radial parts 4, 5 by means of the gaskets 11, 12 received in the grooves 
made at the ends of the said parts 4, 5. 
The hydraulic circuit of this actuator comprises two pairs of similar 
conduits which feed hydraulic fluid to the compartments 8, 9: an inlet A 
opens, on the one hand, into a conduit 13 which is made in the body 3 and 
which opens into the chamber 9 and, on the other hand, into a branch 14 
located outside the body 3 and extended by a conduit 15 in the body 3. The 
conduit 15 is diametrically opposite the conduit 13 and opens into the 
chamber 8 on the opposite side to the conduit 13. 
As a complement to this, a fluid outlet B communicates, on the one hand, 
with a conduit 16 opening into the chamber 8 on the side of the radial 
part 4 opposite to that where the conduit 15 opens and, on the other hand, 
with a branch 17 located outside the body 3. This branch 17 is extended by 
a conduit 18 in the body 3, which is diametrically opposite the conduit 16 
and which opens into the part of the compartment 9 opposite that which 
receives the conduit 13. 
If a hydraulic fluid at the pressure P1 is introduced via the inlet A, this 
fluid runs through the conduits 13, 14, 15 along the path indicated by the 
arrows, so as to feed the respective compartments 9 and 8 and, more 
specifically, the sub-compartments contained between the vane 1 and the 
walls of the body 3, in which are made the conduits 13, 15. Thus, the vane 
1 rotates about the axis X--X in the direction of the arrow represented by 
an unbroken line (the clockwise direction), whilst the fluid at the 
pressure P0 is expelled from the two sub-compartments opposite the two 
sub-compartments receiving the pressure P1 and returns to the tank via the 
conduits 16, 17 and 18. 
Conversely, if the pressure P1 higher than P0 is exerted at the inlet B, 
the vane 1 rotates in the opposite direction to the preceding direction, 
and the fluid returns to the tank via the conduits 13, 14 and 15, as 
indicated by the arrows represented by broken lines. 
The vane 1 is fixed by means of its hub 6 to the element to be driven in 
rotation (not shown) which can be, for example, an aircraft control 
surface. 
In the second embodiment illustrated in FIG. 2, the vane 21 comprises four 
radial parts 22, 23, 24, 25 arranged at an equal angular distance from one 
another, and a central hub 26 integral with the parts 22 to 25. The hub 26 
is in sealing contact with the ends of four radial extensions 27, 28, 29, 
31 of the body 32 by means of four gaskets 33. These four extensions 27 to 
31 delimit between them four chambers 34, 35, 36, 37 having cylindrical 
outer walls 34a, 35a, 36a, 37a in sealing contact with the ends of the 
radial parts 22 to 25 by means of gaskets 30 received in the ends of the 
said radial parts 22 to 25. 
The hydraulic circuit feeding this actuator is composed as follows: a fluid 
inlet A' feeds an annular conduit 38 located outside the body 32 and 
communicating with four radial conduits 39, 41, 42, 43 passing through the 
body 32 and opening into the respective compartments 37, 36, 35, 34 
opposite the corresponding faces of the four radial parts 25, 24, 23, 22. 
As a component to this, a fluid outlet B' communicates with a peripheral 
conduit 44 located outside the body 32 and feeding four radial conduits 
45, 46, 47, 48 passing through the body 32 and opening into the respective 
compartments 37, 34, 35, 36 on the side of the radial parts 25, 22, 23, 24 
opposite the conduits 39, 43, 42, 41. 
If a hydraulic pressure P1 is exerted at the inlet A', the fluid travels 
along the path indicated by the arrows represented by unbroken lines and 
exerts on the radial parts 25, 22, 23, 24 of the vane 21 the pressure P1 
which causes the vane to rotate in the clockwise direction. In correlation 
with this, the fluid at the pressure P0, less than P1, is expelled from 
the opposite compartments of the chambers 34 to 37 via the conduits 45 to 
48 and the conduit 44, up to the outlet B' leading to the tank. Of course, 
the vane 21 rotates in the opposite direction to the preceding direction 
if the pressure P1 is exerted at B', whilst the outlet A' is at the 
pressure P0. 
A third embodiment of the actuator will now be described with reference to 
FIGS. 3, 4A, 4B, 5A and 5B. 
Here, the vane 51 consists of two diametrically opposite radial parts 52, 
53 integral with a cylindrical central hub 54. The parts 52 and 53 can 
move angularly about the axis X--X of the hub 54 in chambers 55, 56 formed 
in a body 57. Sealing between the two compartments of each chamber 55, 56 
is ensured by means of the gaskets 58 received in grooves in the ends of 
the radial parts 52, 53, whilst sealing between the hub 54 and the body 57 
is obtained by means of gaskets 59 seated in diametrically opposite 
grooves in the body 57. 
Here, the hydraulic circuit comprises return conduits 61 at the pressure of 
the tank R, which are machined in the hub 54 and the diametrically 
opposite ends of which open out opposite two transverse grooves 62 made on 
the periphery of a central shaft 63 received in an axial bore of the hub 
54. In the latter there are also four radial conduits 64, 65, 66, 67. The 
conduits 64, 65 open into two opposite compartments of the chamber 55 
which are separated by the radial part 52, whilst the conduits 66, 67 open 
into the two compartments of the chamber 55 which are separated by the 
radial part 53. The grooves 62 are machined in a portion 63a of 
cylindrical cross-section of the shaft 63. This portion 63a defines the 
distribution characteristics of the system. 
Two conduits 68 for feeding hydraulic fluid at the pressure P supplied by a 
hydraulic source (not shown) are formed within the hub 54 between the 
conduits 64 and 65 on the one hand and the conduits 66 and 67 on the other 
hand. 
The mode of operation of the actuator of FIGS. 3 and 4A-4B is explained 
with reference to FIGS. 5A and 5B. At rest, the actuator is in the 
position shown in FIG. 3, where it can be seen that the conduits 61 and 68 
are closed off by the rounded vertices of the central portion 63a of the 
shaft 63, so that no fluid circulates in the actuator. 
If the shaft 63 is rotated through a specific angle in the clockwise 
direction (FIG. 5A), the portion 63a of the shaft 63 exposes the feed 
conduits 68 which then communicate with the respective conduits 65 and 67. 
The fluid at the pressure P thus fills the compartments of the chambers 
55, 56, thereby causing the vane 51 to rotate in the clockwise direction, 
whilst the fluid at the pressure R flows off from the other two 
compartments of the chambers 55, 56 via the conduits 64, 66, 61 towards 
the tank at the pressure R. 
The circuit followed by the hydraulic fluid, the pressure exerted by the 
latter and the rotation of the vane 51 are symbolized by the arrows marked 
in FIG. 5A. 
The vane 51 continues to rotate until the conduits 68 and 61 are once again 
closed off by the portion 63a of the shaft 63, the vane 51 then having 
"copied" the new angular position of the latter and coming to a stop. 
If the shaft 63 experiences a rotation in the anticlockwise direction (FIG. 
5B), this rotation puts the conduits 68 and 64, 66 in communication with 
one another, so that the fluid causes the vane 51 likewise to rotate in 
the anticlockwise direction and leaves at the pressure R via the conduits 
65 and 67. As before, the rotation of the vane 51 stops when the conduits 
61 and 68 are closed off once more by the portion 63a, the position of 
which has been "copied" by the vane 51. 
In this particular use, therefore, the actuator functions as a device for 
copying the angular position of a control shaft. 
In the embodiment illustrated in FIGS. 6 to 9, the actuator 65 is equipped 
with a vane 66 comprising two diametrically opposite radial parts 70 
joined by means of an annular piece 69 and a hub 71 of annular 
cross-section which passes axially through the annular piece 69. The 
latter is fixed in rotation with the hub 71 by means of matching axial 
splines, such as 72. Likewise, to ensure that the shaft 73 seated in the 
axial recess of the hub 71 and fixed to an element (not shown) is driven 
in rotation, there is any suitable means, such as matching axial splines 
90 formed on the periphery of the shaft 73 and in the inner wall of the 
hub 71. On the opposite side to the shaft 73, a bolt 130 provided with a 
thread 190 is screwed into an internal thread of the hub 71 coaxially 
relative to the shaft 73 and makes it possible to clamp the bearings 92, 
93. 
The actuator 65 also possesses an annular body 74 which surrounds the 
radial parts 70 and the central piece 69 and on the periphery of which are 
machined two circumferential grooves 75, 76 coaxial relative to the 
general axis Y--Y of the actuator. The groove 75 communicates, on the one 
hand, with a feed conduit 77, 78 made in an outer casing 79 and a sleeve 
80 and, on the other hand, with two radial conduits 81 made in the body 74 
and opening into respective chambers 82, 83. In like manner, the groove 76 
communicates, on the one hand, with a feed conduit 84 made in the casing 
79 and opening into a bore 130 of a second sleeve 87 and, on the other 
hand, with two radial conduits 86 located in the body 74 and opening into 
the other two hydraulic chambers 88, 89. The body 74 is equipped with an 
annular gasket 74a seated in a groove which is located in the body and 
which is formed between the grooves 75, 76. 
The chambers 82, 83 and 88, 89 are delimited by the body 74, by the radial 
parts 70 and by the central piece 69. The latter and the radial parts 70 
are mounted sealingly relative to the body 74 by means of gaskets 91, 120 
received in the respective grooves in the body 74 and in the ends of the 
radial parts 70. 
The actuator 65 is also equipped with two bearings 92 which have balls 93 
and which are interposed between the hub 71 and an annular body 94 
contained in the casing 79. The latter is equipped with two radial collars 
97, 98 inserted between the radial parts 70 and the bearings 92 which, in 
a complimentary way, are held in place axially by means of an end collar 
99 of the hub 71. The assembly is closed, on the opposite side to the 
collar 99, by means of a cover 101 retained by fastening screws 102 
engaged in the casing 94. 
When the hydraulic fluid under feed pressure enters the conduits 78, 77 and 
the groove 75, this fluid reaches the two opposite chambers 82, 83 via the 
radial perforations 81 and causes the vane 66 to rotate in the clockwise 
direction. The fluid returns to the tank from the chambers 88, 89 via the 
conduits 86, the groove 76, the conduit 84 and the sleeve 87. This rotary 
movement is reversed if the hydraulic pressure is supplied via the groove 
76. 
FIG. 10 shows an actuator 100 identical to the actuator 65, except that its 
cover 101 is replaced by a collar 103 which receives the end 104 of an 
electrical potentiometer 105 having the shaft 73. This potentiometer 105 
is equipped with a slide 106 driven in rotation in a way known per se by 
means of the shaft 73 in response to the resistance of the potentiometer, 
when this shaft is itself rotated, as described above with reference to 
FIGS. 6 to 9. 
Alternatively, it is possible to associate any rotary position-detecting 
element with the shaft 73 of the actuator 65, 100, the potentiometer 105 
being given only as an example. Such an arrangement makes it possible to 
insert these elements in an electro-hydraulic control loop. 
FIGS. 11 and 12 illustrate a series connection of several coaxial actuators 
107, each vane 109 of which is equipped with a male/female coupling 124, 
125, the male elements 124 fitting into the female elements 125. Each 
actuator 107 is of the type shown in FIG. 1, and its vane 109 therefore 
comprises, in addition to the coupling 124-125, two radial parts 111 which 
are connected by means of a central hub 112 and which can move angularly 
in two chambers 113 fed via perforations 114, 115, 116, 117 made in the 
body 118. 
Since each actuator 107 has its own hydraulic circuit, the series 
connection of several coaxial actuators 107 makes it possible to ensure 
the redundancy necessary for safety reasons where the actuation of an 
aircraft control surface is concerned. 
In all the embodiments described, the chambers or compartments (8, 9; 55, 
56; 83 to 88, 82; 113) extend over angular sectors less than half a 
circumference. 
The vane 130 of FIGS. 13 to 15 is equipped, on the two opposite faces of 
its hub 131, with two sealing rings 132 connected by means of sealing 
cords 133, 134 extending in diametric extensions of the rings 132. The 
rings and the cords 133, 134 are seated in corresponding grooves 135, 136 
made in the opposite faces of the hub 131 and in the radial parts 137, 138 
of the vane 130. The cords 133, 134 extend on either side of the hub 131 
in a plane containing a diameter of the rings 132. The latter and the 
cords 133, 134 ensure excellent sealing between the vane 130 and the wall 
of the chamber of the actuator.