Fluid reaction surfaces (i.e. – impellers) – Working member foldable – pivotable or collapsible to non-use...
Reexamination Certificate
1999-12-08
2001-12-18
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Working member foldable, pivotable or collapsible to non-use...
C416S24400R
Reexamination Certificate
active
06331099
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to hydraulic apparatus and, more particularly, to flexible hoses for communicating hydraulic fluid between a deployable ram air turbine powered hydraulic pump, and the hydraulic system of an aircraft.
The hydraulic return fluid, also known as the pressure fluid, for an aircraft is furnished by a hydraulic pump powered by a propulsive engine or by a turbine having rotatable blades located in and turned by the airstream adjacent the fuselage when the aircraft is airborne. As an aircraft typically has redundant backup systems, it may use both of the foregoing power sources to power, respectively, several hydraulic pumps. The latter power source is commonly referred to as a ram air turbine. A hydraulic pump is commonly attached to the ram air turbine, and directly powered by the turbine's drive shaft. The ram air turbine and attached pump together form a hydraulic power assembly.
Such a hydraulic power assembly is used in two ways. Firstly, it is rigidly mounted external to the fuselage so that the ram air turbine is always exposed to the airstream and thus operates whenever the aircraft is airborne. Alternatively, the assembly is stored in an up position out of the airstream of the airborne aircraft or is housed within the fuselage and rotatably deployed into the airstream of an airborne aircraft only when called on in an emergency.
The rigidly mounted, permanently deployed hydraulic power assembly is commonly called an auxiliary power unit, and is used to generate continual hydraulic return fluid whenever the aircraft is airborne. The deployable hydraulic power assembly is rotated into the airstream only in an emergency, for example, the failure of an engine or a hydraulic pump powered by a main engine, or running out of fuel.
Storing the hydraulic power assembly in an up position or housing it within the fuselage and deploying it only when necessary offers several advantages over using a permanently deployed auxiliary power unit as an emergency backup for hydraulic return fluid. Firstly, the deployable configuration reduces the coefficient of drag for the aircraft because the ram air turbine is seldom going to be exposed to the airstream. Secondly, since the rotatable blade and connected turbine will be rotating only during an emergency, the aforementioned components need not be engineered to the same demanding specifications as an auxiliary power unit generating the same hydraulic return fluid. This results in a savings in cost and weight, as well as an improvement in reliability.
The hydraulic power assembly is typically attached to one end of a strut, with the other end of the strut being mounted on a trunion attached to the airframe. The hydraulic power assembly is deployed by activating an actuator which rotates it around the trunion. The challenge posed by the foregoing configuration lies in communicating the hydraulic fluid between the hydraulic pump of the hydraulic power assembly and the hydraulic system of the aircraft, given the necessary rotation of the hydraulic power assembly relative to the airframe. A conventional approach to this problem is shown in
FIGS. 1
,
2
and
3
.
More particularly,
FIG. 1
is a side view of ram air turbine
21
in its deployed position. Ram air turbine includes blades
23
. Hydraulic pump
25
is attached to and powered by ram air turbine
21
. Hydraulic power assembly
26
is comprised of ram air turbine
21
and hydraulic pump
25
.
Strut
27
includes distal end
29
and proximal end
31
. Hydraulic power assembly
26
is attached to distal end
29
. The foregoing are integral components of aircraft
33
, which also includes airframe
35
, fuselage skin
37
and trunion
39
. The position of hydraulic power assembly
26
in its stowed position within fuselage skin
37
is shown in phantom.
FIG. 2
is a front view of proximal end
31
of strut
27
and illustrates its connection to airframe
35
in greater detail. Proximal end
31
is attached to hydraulic swivel
41
and is also mounted on trunion
39
by means of coaxial annular openings
42
and
43
, allowing strut
27
and hydraulic power assembly
26
to rotate about axis of rotation
44
.
Referring again to
FIG. 1
, hydraulic power assembly
26
is deployed by means of actuator
45
. Actuator
45
is fixedly attached to airframe
35
and rotatably attached to proximal end
31
of strut
27
at pivot
47
. Return tube
49
and supply tube
51
fluidly communicate hydraulic fluid between hydraulic swivel
41
and hydraulic interface
53
. Tubes
49
and
51
are rigid metal tubes. The hydraulic system for aircraft
33
fluidly communicates with hydraulic interface
53
.
FIG. 3
is a frontal section view of hydraulic swivel
41
. Hydraulic swivel
41
includes fitting
55
, journal housing
57
, and annular seals
59
. Fitting
55
is located over and around journal housing
57
, and in slidable abutment thereto. Journal housing
57
includes attachment flange
61
. Proximal end
31
of strut
27
is attached to hydraulic swivel
41
and journal housing
57
at attachment flange
61
. Thus, hydraulic power assembly
26
, strut
27
and journal housing
57
are free to rotate about axis of rotation
44
, relative to fitting
55
and airframe
35
.
Journal housing
57
contains return passageway
63
and supply passageway
65
. Fitting
55
contains return passageway
66
and supply passageway
67
. Return conduit
68
in strut
27
fluidly communicates with pump
25
. Return passageway
63
fluidly communicates return passageway
66
with conduit
68
. Return passageway
66
is sealably connected with return tube
49
. Thus, the return hydraulic fluid from pump
25
fluidly communicates with hydraulic interface
53
.
Supply conduit
69
in strut
27
fluidly communicates with pump
25
. Supply passageway
65
fluidly communicates supply passageway
67
with supply conduit
69
. Supply passageway
67
is sealably connected to supply tube
51
. Thus, the supply hydraulic fluid from hydraulic interface
53
fluidly communicates with pump
25
.
As may be discerned from the foregoing description, seals
59
are necessarily composed of a flexible material, yet are subjected to pressure, corrosive hydraulic fluid, and friction from the rotation of journal housing
57
relative fitting
55
. Thus, as is typical for devices having fluid seals, the reliability and life of hydraulic swivel
41
is primarily limited by the reliability and life of seals
59
.
Furthermore, should seals
59
stick or otherwise fail to allow the free rotation of journal housing
57
relative to fitting
55
, fitting
55
would be subjected to torque about axis of rotation
44
. Since fitting
55
is coupled to return tube
49
and supply tube
51
, the application of such torque would create a lateral force against fitting
55
and, more particularly, against the respective connections between return tube
49
and return passageway
66
, and supply tube
51
and supply passageway
67
. As neither fitting
55
nor the respective connections are designed to resist lateral force, such loading could cause the leakage of hydraulic fluid from hydraulic swivel
41
.
In addition to concerns over leakage, the sticking of seals
59
could cause crimping in tubes
49
and
51
, which would restrict the flow of hydraulic fluid therethrough. With respect to supply tube
51
, crimping could result in the supply flow dropping low enough to cause cavitation in the supply flow to pump
25
, resulting in vaporization of hydraulic fluid and, ultimately, the failure of pump
25
to maintain the return pressure above the required minimum operational level.
Given the requirements that hydraulic swivel
41
communicate hydraulic fluid without leaking and that journal housing
57
rotate relative to fitting
55
, the components of hydraulic swivel
41
must be machined to very narrow tolerances. The manufacture of hydraulic swivel
41
is thus expensive. Furthermore, great care must be taken to colinearly align the axis of rotation of journal housing
57
relat
Eccles Steven Robert
Schindler Wayne Godoy
Allied-Signal Inc.
Look Edward K.
Nguyen Ninh
Zak, Jr. Esq. William J.
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