U.S. patent number 3,792,937 [Application Number 05/187,981] was granted by the patent office on 1974-02-19 for bladed rotors.
This patent grant is currently assigned to Dowty Rotol Limited. Invention is credited to John Alfred Chilman.
United States Patent |
3,792,937 |
Chilman |
February 19, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
BLADED ROTORS
Abstract
A bladed rotor includes a hub defined by two casing parts having
portions which, when the parts are held together by securing means,
form sockets in which the blades of the rotor are mounted. A guide
is provided in one of said parts and another guide is provided in
the other of said parts. The guides are separated by space defining
means and support a control member movable with respect thereto.
Means provided in said space connect said control member to the
blades and movement of that member adjusts the blades.
Inventors: |
Chilman; John Alfred (Stroud,
EN) |
Assignee: |
Dowty Rotol Limited
(Gloucester, EN)
|
Family
ID: |
10464371 |
Appl.
No.: |
05/187,981 |
Filed: |
October 12, 1971 |
Current U.S.
Class: |
416/157R;
416/167; 416/137 |
Current CPC
Class: |
B64C
11/06 (20130101); B64C 11/32 (20130101) |
Current International
Class: |
B64C
11/32 (20060101); B64C 11/06 (20060101); B64C
11/00 (20060101); B64c 011/38 () |
Field of
Search: |
;416/157,157A,61,167,165,166,164,137,208,206,162,154,156 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
666,385 |
|
Oct 1938 |
|
DD |
|
283,406 |
|
Jan 1965 |
|
NL |
|
173,842 |
|
Dec 1960 |
|
SW |
|
Primary Examiner: Powell, Jr.; Everette A.
Attorney, Agent or Firm: Young and Thompson
Claims
I claim:
1. A bladed rotor including a hub casing defined by two casing
parts, each having a first portion including
radially-outwardly-directed projections, the two portions being of
substantially identical form so that when said parts are held
together in assembled relation by securing means said projections
form radially-outwardly-directed sockets of circular cross-section
in which the blades of the rotor are mounted with freedom for
pitch-change adjustment about their longitudinal axes, the plane in
which the said two parts are in engagement being disposed
diametrically of all the sockets, each of said casing parts also
having a single cylindrical portion projecting from its said first
portion, the two cylindrical portions being of substantially
identical form and extending from the first portions away from each
other with their axes coincident with the axis of rotation of the
rotor, space-defining means which separate the two cylindrical
portions, the one axially from the other, one end closure wall
provided at the end of one of said cylindrical portions remote from
said plane, another end closure wall positioned at that end of the
other of said cylindrical portions remote from said plane, a piston
comprising a hollow rod, which is disposed with one end portion
thereof in slidable engagement with respect to the inner wall of
said one cylindrical portion, and a piston head formed by an end
wall which closes the other end portion of the hollow rod and which
is disposed in slidable engagement with respect to the inner wall
of said other cylindrical portion, and means provided in said space
which connect the piston to the blades, said other cylindrical
portion and its end closure wall forming a chamber for said piston
into which fluid is suppliable under pressure for effecting axial
sliding movement of the piston with respect to the cylindrical
portion and thus adjustment of the blades about their longitudinal
axes.
2. A bladed rotor including a hub casing defined by two casing
parts, each having a first portion including
radially-outwardly-directed projections, the two portions being of
substantially identical form so that when said parts are held
together in assembled relation by securing means said projections
form radially-outwardly-direction sockets of circular cross-section
in which the blades of the rotor are mounted with freedom for
pitch-change adjustment about their longitudinal axes, the plane in
which the said two parts are in engagement being disposed
diametrically of all the sockets, each of said parts also having a
single cylindrical portion projecting from its said first portion,
the two cylindrical portions being of substantially identical form
and extending from the first portions away from each other with
their axes coincident with the axis of rotation of the rotor,
space-defining means which separate the two cylindrical portions,
the one axially from the other, one end closure wall provided at
that end of one of said cylindrical portions remote from said
plane, another end closure wall positioned at that end of the other
of said cylindrical portions remote from said plane, a piston
comprising a hollow rod, whic is disposed with one end portion
thereof in slidable engagement with respect to the inner wall of
said one cylindrical portion, and a piston head formed by an end
wall which closes the other end portion of the hollow rod and which
is disposed in slidable engagement with respect to the inner wall
of said other cylindrical portion, mechanical spring means, whose
axis is coincident with said axis of rotation, which means at one
end engages said one end closure wall and which so projects into
said hollow rod as at its other end to engage said end wall forming
said piston head, and means provided in said space which connect
the piston to the blades, said other cylindrical portion and its
end closure wall forming a chamber for said piston into which fluid
is suppliable under pressure for effecting axial sliding movement
of the piston against said spring means and thus adjustment of the
blades about their longitudinal axes.
3. A bladed rotor including a hub casing defined by two casing
parts, each having a first portion including
radially-outwardly-directed projections, the two portions being of
substantially identical form so that when said parts are held
together in assembled relation by securing means said projections
form radially-outwardly-directed sockets of circular cross-section
in which the blades of the rotor are mounted with freedom for
pitch-change adjustment about their longitudinal axes, the plane in
which the said two parts are in engagement being disposed
diametrically of all the sockets, each of said casing parts also
having a single cylindrical portion projecting from its said first
portion, the two cylindrical portions being of substantially
identical form and extending from the first portions away from each
other with their axes coincident with the axis of rotation of the
rotor, space-defining means which separate the two cylindrical
portions, the one axially from the other, one end closure wall
provided at that end of one of said cylindrical portions remote
from said plane, another end closure wall positioned at that end of
the other of said cylindrical portions remote from said plane, a
piston comprising a hollow rod, which is disposed with one end
portion thereof in slidable engagement with respect to the inner
wall of said one cylindrical portion, and a piston head formed by
an end wall which closes the other end portion of the hollow rod
and which is disposed in slidable engagement with respect to the
inner wall of said other cylindrical portion, means provided in
said space which connect the piston to the blades, and said piston
and said cylindrical portions being dimensioned to afford a range
of sliding movement of the piston corresponding to a range of
movement of the blades which includes positive and negative pitch,
a first mechanical spring means and a second mechanical spring
means the axes of which are coincident with said axis of rotation,
said first spring means at one end engaging said end wall forming
said piston head and at the other end engaging said second spring
means, and said second spring means at its end remote from the
first spring means engaging said one end closure wall, and said
other cylindrical portion and its end closure wall forming a
chamber for said piston into which fluid is suppliable under
pressure for effecting axial movement of the piston against said
spring means and thus adjustment of the blades.
4. A bladed rotor including a hub defined by two casing parts
having portions which, when the parts are held together in
assembled relation by securing means, form
radially-outwardly-directed sockets of circular cross-section which
house anti-friction bearing means by way of which the blades of the
rotor are mounted with freedome for pitch-change adjustment about
their longitudinal axes, the plane in which said two parts are in
engagement being disposed diametrically of all the sockets, and
said two parts each having a respective bore portion provided with
an end closure wall remote from said plane, the axis of one bore
portion being coincident with that of the other bore portion,
space-defining means which separate said bore portions axially one
with respect to the other, a hollow piston wholly enclosed within
said two assembled casing parts with one end portion thereof
slidably supported in said one bore portion and the other end
portion thereof slidably supported in said other bore portion, said
piston closed at said other end portion and there forming with said
other bore portion an expansible pitch-change motor chmber which is
connectible with fluid under pressure, means provided in said space
which connect the piston to the blades whereby sliding movement of
the piston with respect to the bore portions under the pressure of
fluid in said chamber effects adjustment of said blades, a
mechanical coil spring so extending within said hollow piston as at
one end to engage the closed end portion thereof, and a Belleville
washer stack which at one end is engaged by the other end of said
coil spring and which, at its other end, engages the end closure
wall of said one bore portion, said stack being engageable by said
piston and compressible thereby as the piston moves through part of
its range of movement, and both said coil spring and said stack
being arranged with their axes coincident with the rotational axis
of the rotor.
5. A bladed rotor including a hub defined by two casing parts
having portions which, when the parts are held together in
assembled relation by securing means, form
radially-outwardly-directed sockets of circular cross-section which
house anti-friction bearing means by way of which the blades of the
rotor are mounted with freedom for pitch-change adjustment about
their longitudinal axes, the plane in which said two parts are in
engagement being disposed diametrically of all the sockets, and
said two parts each having a respective bore portion, the axis of
one bore portion being co-incident with that of the other bore
portion, space-defining means which separate said bore portions
axially one with respect to the other, a hollow piston wholly
enclosed within said two assembled casing parts with one end
portion thereof slidably supported in said one bore portion and the
other end portion thereof slidably supported in said other bore
portion, said piston being closed at said other end portion and
there forming with said other bore portion an expansible
pitch-chnge motor chamber which is connectible with fluid under
pressure, and the piston having surfaces spaced apart from the
adjacent end faces of the roots of at least certain of the blades
with portions upstanding from those surfaces which have such
sliding relationship with said faces and which are so disposed in
relation to the respective blade longitudinal axis, as
substantially to prevent angular displacement of said piston about
the rotational axis of the rotor with respect to said hub, the area
of the face associated with each upstanding portion which is in
engagement with the respective blade root end face being small in
relation to the area of that root end face, spring means disposed
between said piston and an abutment of said one bore portion, and
means provided in said space which connect the piston to the blades
whereby sliding movement of the piston with respect to the bore
portions under the pressure of fluid in said chamber and against
the effort of said spring means effects adjustment of said
blades.
6. A bladed rotor as claimed in claim 3, wherein said first spring
means comprises a coil spring and the second spring means comprises
a stack of spring washers, the external diameter of said stack
being substantially greater than that of said coil spring.
7. A bladed rotor as claimed in claim 4, wherein a ported tube is
connected to said piston and provides means by way of which fluid
under pressure is introduced into said chamber for effecting
movement of the piston against the effort of said coil spring and
stack in the direction corresponding to adjustment of the blades in
the pitch fining direction.
8. A bladed rotor as claimed in claim 4, wherein said casing parts
include stop means with which the piston is co-operable and which
afford the piston an extent of movement corresponding to movement
of the blades in the positive pitch range and the negative pitch
range, movement from the positive pitch range to the negative pitch
range, and vice versa, being through zero pitch, and said stack
being engaged by said piston only when the blades are in the
negative pitch range.
9. A rotor as claimed in claim 1, wherein said securing means
include bolts provided in the vicinity of the sockets.
10. A rotor as claimed in claim 2, wherein each blade is mounted in
an anti-friction bearing provided in its socket, each said bearing
being split in a diametral plane thereof.
Description
This invention relates to bladed rotors.
According to this invention a bladed rotor includes a hub defined
by two casing parts having portions which, when the parts are held
together by securing means, form sockets in which the blades of the
rotor are mounted, a guide in one of said parts and a guide in the
other of said parts, said guides being separated by a space and
supporting a control member movable with respect thereto, and means
in said space connecting said control member to the blades whereby
movement of that member adjusts the blades.
The securing means may include bolts provided in the vicinity of
the sockets.
Each blade may be mounted in an anti-friction bearing provided in
its socket, each said bearing being split in a diametral plane
thereof.
The bladed rotor may be a propeller suitable for an aerial vehicle,
and the blades thereof may be of variable-pitch. Alternatively the
blades may be of variable-twist or variable camber.
The guides may comprise bores and said control member comprise a
piston which together form a pitch-change motor.
The pitch-change motor may be of single-acting hydraulic type. The
motor may be operable under the control of a speed-sensitive
centrifugal governor and/or under the control of a
manually-operable hydraulic valve having a follow-up mechanism
associated therewith.
Movement of said piston under hydraulic pressure may be in a
direction appropriate to pitch-fining of the blades, such movement
being against the effort of first spring means.
The range of movement of the piston may be sufficient to afford
movement of the blades beyond fine pitch, through zero pitch into
the reverse pitch range for effecting braking of the associated
vehicle.
In this case further spring means may be provided, engageable by
said piston and compressed thereby as the piston moves through that
part of its range corresponding to reverse pitch of the blades.
The first said spring means may be a mechanical coil spring and
said further spring means may comprise a Belleville washer stack,
both said coil spring and said stack being arranged with their axes
coincident with the rotational axis of the rotor.
Blades of the rotor may carry fly-weights so disposed with respect
to each blade longitudinal axis as to assist said first spring
means in biassing the blades in the pitch-coarsening direction.
The piston may have surfaces spaced apart from the adjacent end
faces of the roots of at least certain of the blades with portions
upstanding from those surfaces which have such sliding relationship
with said faces and which are so disposed in relation to the
respective blade longitudinal axis, as substantially to prevent
angular displacement of said piston about the rotational axis of
the rotor with respect to said hub, the area of the face associated
with each upstanding portion which is in engagement with the
respective blade root end face being small in relation to the area
of that root end face.
One embodiment of the invention will now be particularly described
by way of example with reference to the accompanying drawings of
which,
FIG. 1 is a cross-section of a propeller hub and of a part of a
blade mounted in the hub,
FIG. 2 is a cross-section taken along line II--II,
FIG. 3 is a sectional view taken long the line III--III on FIG. 1,
and,
FIG. 4 is a partial view in the direction of the arrow IV on FIG.
1.
Referring to the drawings, a bladed rotor in the form of an
aircraft propeller 11 includes a hub 12 comprising two aluminum
alloy casing parts 13 and 14 held together by securing means which
take the form of four bolts 15 and four nuts 16, the bolts passing
through holes 17 and 18 provided in the parts 13 and 14.
The engaging faces 19 and 20 of the parts 13 and 14 lie in a plane
21. The parts 13 and 14 together define four sockets 22, 23, 24 and
25 which receive the root portions 26, 27, 28 and 29 of aluminium
alloy propeller blades 30, 31, 32 and 33 which are each mounted in
respective roller bearings 34, 35, 36 and 37 for pitch variation
about the respective longitudinal pitch-change axis 38.
The inner race 39, the roller cage 40 and the outer race 41 of each
of these bearings are split in a diametral plane thereof. Each
inner race 39 is held in a suitably-shaped seating 42 in its
respective blade root portion by a wire ring 43, while each outer
race 41 is located in a suitably-shaped recess 44 formed in the
respective hub socket.
Each blade has nylon bearing inserts 45 and 46 and a sealing ring
47 in the position shown. These components are also split in a
diametral plane.
Each blade also carries a fly-weight assembly 48 so positioned
thereon as in operation to produce moments about the blade
longitudinal axis which oppose the inherent centrifugal twisting
moments in the blades, and which bias the blades in the
pitch-coarsening direction. Each fly-weight assembly is held fast
to its blade by a U-bolt 49, the U-bolt and part of the fly-weight
assembly engaging a peripheral recess 50 in the blade.
As shown in FIG. 1, the part 13 is formed with a guide in the form
of a bore 51 whose axis is coincident with the rotational axis 52
of the rotor. The bore 51 is closed at its forward end portion by a
hard rubber plug 53 which engages an aperture 54 formed in the end
wall 55.
Similarly, the part 14 is provided with a guide in the form of a
bore 56, of the same diameter as the bore 51, which is
axially-spaced from the bore 51 and whose axis is also coincident
with the axis 52. The rearward end portion of the bore 56 is closed
by a wall 57 which has an aperture 58 through which an oil supply
tube 59 passes coaxially with the axis 52. The forward end portion
of the tube 59 is screw-threadedly connected at 60 to a flanged
member 61 which in turn is held fast with respect to a pitch-change
motor piston 62, which is of aluminium alloy, by means of set
screws as at 63. The piston 62 is hollow and is supported for axial
sliding movement in the axially-spaced bores 51 and 56, thus to
form a control member for the blades.
Although generally of cylindrical shape, the piston 62 is provided
with a central portion of generally square cross-sectional shape as
at 64 which includes four upstanding portions 65 each of which is
associated with a respective crank pin 66 projecting from each
blade root portion 26, 27, 28 and 29. Each crank pin 66 projects
into a bore provided in a respective slide block 67 which is itself
slidingly mounted in a channel of the respective upstanding portion
65, a washer 68 being provided between the end face of the
respective blade root portion and the portion 64.
As shown in FIG. 2, two slide buttons 69 forming further upstanding
portions are located in short bores 70 provided in the central
portion 64, being positioned between the end faces of the two blade
root portions 26 and 28 and the central portion 64 to prevent
tilting of the piston about its longitudinal axis during its axial
movement.
First spring means in the form of a mechanical coil spring 71 is
provided between the right-hand portion in FIG. 1 of the piston 62
and a Belleville washer stack 72 which forms an abutment for the
coil spring. The Belleville washer stack 72 is housed at the
forward end portion of the bore 51 and seats upon a tubular insert
73. The coil spring 71 is also located on the insert 73 so that
both the coil spring and the Belleville washer stack are co-axially
arranged with respect to the rotational axis 52.
The propeller is intended for fitment upon an engine output shaft
shown in dotted lines at 74 with a mounting flange 75 and spigot
portion 76. The rearward portion of the part 14 is so shaped as to
fit upon the spigot 76, and eight set bolts, one of which is shown
at 77, which pass through the flange 75 retain the propeller upon
the shaft 74, two locating dowels, one of which is shown at 78,
also being provided.
In FIG. 1 of the drawings the piston 62 is shown in its extreme
rearward position corresponding to maximum coarse pitch of the
blades 30, 31, 32 and 33. The chamber 79 to the rear of the piston
62 is chargeable with liquid under pressure supplied through the
tube 59 and passing into the chamber through ports 80 in the
tube.
The central portion 64 of the piston 62 is provided with a stop
face 81 at the position shown in FIG. 1 which comes into engagement
with the face 82 of the casing part 13 at the maximum reverse pitch
condition, while the face 83 at the rearward end portion of the
piston comes into engagement with the wall 57 at the
fully-feathered condition.
The construction of the hub hereinbefore described is of relatively
simple and inexpensive construction because the pitch-change motor
simply comprises the portions of the casing parts 13 and 14 having
the two bores 51 and 56 and the piston 62 supported by these bores.
The axial spacing between the bores gives a relatively large access
opening for connection of the piston to the roots of the propeller
blades for pitch-change.
In order to assemble the components of the propeller, the casing
part 14 is positioned with its face 20 horizontal and the
appropriate outer half-races 41 of the split roller bearing 34, 35,
36 and 37 are fitted into their recesses 44 complete with the
half-sets of rollers in their half-cages 40. The appropriate halves
of the inserts 45 and 46 and of the sealing rings 47 are also
fitted.
The four blades 30, 31, 32 and 33 each fitted with its two-part
inner race 39 held thereon by the wire ring 43 are placed in
position complete with their crank-pins 66 and washers 68. Such
placing is substantially simultaneous with the fitting of the
piston 62 complete with its slide blocks 67 and slide buttons 69,
the crank-pins being entered into the slide blocks.
The other outer half-races 41, complete with their half-sets of
rollers in the respective half-cages 40 are now placed in position
on the blade root portions. The other halves of the inserts 45 and
46 and of the sealing rings 47 are also fitted.
A special tool (not shown) is applied to the part 13 for
compression of the coil spring 71 and the Belleville washer stack
72. This tool is applied with the plug member 53 removed.
The part 13 complete with the tool in its operative position is
fitted to the assembly of components and secured by the bolts 15
and the nuts 16. The tool is then adjusted to allow the coil spring
71 and Belleville washer stack 72 to expand to their full free
length, whereupon the tool is released and removed from the
assembly and the plug member 53 is fitted to the aperture 54.
The fly-weight assemblies 48 are then fitted to the blades.
Suitable balance weights (not shown) are bolted in convenient
manner to the hub as necessary for balance of the structure. The
tube 59 is fitted to the flanged member 61 just prior to mounting
the propeller on the engine shaft 74.
In operation of the propeller, liquid under pressure admitted under
the control of a control valve assembly (not shown, but carried by
the engine structure) into the chamber 79 causes compression of the
coil spring 71 and movement of the piston 62 and thus of the blades
30, 31, 32 and 33 in the pitch-fining direction, to the left in
FIG. 1, the blocks 67 which are of nylon, sliding in their
respective upstanding portions 65, and the washers 68, which are
basically of polytetrafluoroethylene material, and the buttons 69,
which are also basically of polytetrafluoroethylene material,
affording low friction between the linearly moving piston 62 and
flat end faces of the blade root portions 26, 27, 28 and 29 as the
blades rotate about their pitch-change axes 38.
Such movement is also against the effort of the fly-weights 48
which assists the coil spring 71 is biassing the blades in the
pitch-coarsening direction.
As the blades reach the pitch piston required by the setting of the
control valve assembly, the tube 59 applies a follow up signal to
the control valve assembly to arrest the supply of pressure liquid
through the tube and to hold the piston 62 hydraulically against
the effort of the spring 71 so that the blades are held in the
selected position.
In practice, the blades are positioned at approximately 0.degree.
for engine starting, at approximately 18.degree. for take-off of
the aircraft, at approximately 35.degree. for flight cruise, and at
approximately 15.degree. for approach idling.
To move the blades into reverse pitch for aircraft braking upon
touch-down, they are caused to pass through the 0.degree. position
by suitable adjustment of the control valve assembly, the piston 62
then compressing the coil spring 71 until the -5.degree. blade
angle position is reached, whereupon the piston 62 commences to
compress the Belleville washer stack 72 as well as further to
compress the coil spring 71.
AS the blades reach their -15.degree. position, which in this
embodiment is the maximum reverse (negative) pitch angle, the face
81 engages the face 82. FIG. 4 indicates the range of pitch-change
movement, showing the extreme crank-pin positions at 66 and
66'.
The Belleville washer stack 72 is of higher rate than the coil
spring 71 and serves to overcome the aerodynamic twisting moments,
(otherwise effective upon the blades to move them in the
pitch-fining direction), thus to move the blades back into the
positive pitch range when the hydraulic pressure in the chamber 79
is sufficiently relieved by appropriate selection of the control
valve assembly.
Subsequent movement of the blades in the pitch-coarsening direction
in the positive range is under the effort of the coil spring 71 and
also the fly-weights 48 which oppose the centrifugal twisting
moments inherent in the blades, the rate of pitch-change then being
dependent upon the out-flow of liquid from the chamber 79 as is
permitted by the control valve assembly.
As the blades approach the feathered (85.degree. position) the
rotational speed of the propeller naturally falls and the
fly-weights 48 in themselves would be inadequate to move the blades
to their fully feathered condition. The coil spring 71 is of
sufficient rate as to ensure completion of the feathering
movement.
During such pitch-change movement, tilting of the piston 62 about
the rotational axis 52 is substantially prevented in one direction
(the clockwise direction when viewed in FIG. 2) by each of the two
buttons 69 which are in sliding engagement with the respective
blade root end face and is substantially prevented in the other
direction (the anti-clockwise direction when viewed in FIG. 2) by
the upstanding portions 65 and the associated washers 68, the
latter also engaging the respective blade root end face. Since the
area of the face of each button 69 and of the face of each washer
68 in engagement with the respective blade root end face is small
in relation to the area of the root end face, since the material of
each button and each washer is basically polytetrafluoroethylene,
and since the slide blocks 67 are of nylon, low friction is
afforded between the linearly moving piston 62 and the flat root
end faces of the blades as the blades are driven about their
longitudinal axes for pitch-change. Thus the arrangement provides a
low-friction pitch-change connection between the pitch-change motor
and the blades.
The piston is thus constructed in a manner which avoids the use of
splines or rods in its mounting in the hub and in its connection to
the blades.
It will be seen that by the simplified construction the forgings
from which the hub parts 13 and 14 are produced can be of the same
basic shape, the differences between the forward portion of the hub
structure and the rearward portion of the hub structure being
obtained by machining. However, lhe fact that only one basic
forging shape is required contributes to the inexpensiveness of
this propeller construction.
The invention is not limited to the provision of four blades on the
hub as any other desired number of blades, with a piston of
suitable cross-sectional shape in the zone of the blade root end
portions, may be provided.
Further the invention is not limited to aircraft propellers as with
advantage it may well be applied to any other bladed rotor, for
example propellers for air-cushion vehicles, for boats, ships and
the like, or alternatively, fans for vehicles or fixed
installations, or the bladed rotors of ram-air turbines.
Although in the embodiment described with reference to the drawings
the blades each have fly-weights attached thereto, in other
embodiments no such fly-weights may be provided, or alternatively
in yet other embodiments further fly-weights may be provided.
Again, on a four-bladed propeller, only two fly-weights may be
provided on opposite blades.
Further, although in the embodiments described with reference to
the drawings the blades of a bladed rotor are variable in pitch, in
other embodiments they may instead be variable in twist, or
variable in camber. Also, the rotor may instead be of
non-reversible pitch type.
Again, although in the embodiment above described with reference to
the drawings the piston moves rearwardly of the propeller for
pitch-coarsening, in alternative embodiments in the piston instead
moves forwardly of the propeller for pitch-coarsening.
Further, in alternative embodiments of the invention, instead of
the pitch-change motor of the bladed rotor being controlled by a
manually-operable control valve assembly, it may be controlled by a
speed-sensitive centrifugal governor, or by a manually-operable
control valve assembly and a speed-sensitive cntrifugal
governor.
The invention is not limited to the type of pitch-change motor
described with reference to the drawings, as in other embodiments
it may be of double-acting hydraulic type, or again in other
embodiments the motor may not be of hydraulic type but instead may
be of pneumatic type.
Again, instead of the control member taking the form of a piston
movable in bores, in other embodiments the control member may be a
device other than a piston mounted in guides other than bores and
displaceable with respect to the guides by mechanical, electrical
or other suitable means.
* * * * *