U.S. patent application number 12/568144 was filed with the patent office on 2010-04-01 for actuator.
This patent application is currently assigned to Goodrich Actuation Systems Limited. Invention is credited to Michael Paul Somerfield, Alan M. Thompson.
Application Number | 20100078608 12/568144 |
Document ID | / |
Family ID | 40019708 |
Filed Date | 2010-04-01 |
United States Patent
Application |
20100078608 |
Kind Code |
A1 |
Somerfield; Michael Paul ;
et al. |
April 1, 2010 |
Actuator
Abstract
An actuator comprises a gear arrangement operatively connected
to a rotatable input of a linearly extendable actuator device,
wherein the gear arrangement comprises a pinion gear and a face
gear in meshing engagement with one another.
Inventors: |
Somerfield; Michael Paul;
(Stoke on Trent, GB) ; Thompson; Alan M.; (West
Markham, GB) |
Correspondence
Address: |
ANDRUS, SCEALES, STARKE & SAWALL, LLP
100 EAST WISCONSIN AVENUE, SUITE 1100
MILWAUKEE
WI
53202
US
|
Assignee: |
Goodrich Actuation Systems
Limited
Solihull
GB
|
Family ID: |
40019708 |
Appl. No.: |
12/568144 |
Filed: |
September 28, 2009 |
Current U.S.
Class: |
254/103 ;
74/416 |
Current CPC
Class: |
F16H 25/20 20130101;
F16H 25/2204 20130101; Y02T 50/671 20130101; Y10T 74/18704
20150115; F05D 2260/4031 20130101; Y10T 74/1966 20150115; F16H
2025/2093 20130101; F16H 1/12 20130101; F02K 1/763 20130101; Y02T
50/60 20130101; F05D 2250/292 20130101; F16H 2055/173 20130101;
Y10T 74/18696 20150115; Y10T 74/18688 20150115 |
Class at
Publication: |
254/103 ;
74/416 |
International
Class: |
B66F 3/02 20060101
B66F003/02; F16H 1/12 20060101 F16H001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2008 |
GB |
0817775.0 |
Nov 27, 2008 |
GB |
0821678.0 |
Apr 15, 2009 |
GB |
0906400.7 |
Claims
1. An actuator comprising a gear arrangement operatively connected
to a rotatable input of a linearly extendable actuator device,
wherein the gear arrangement comprises a pinion gear and a face
gear in meshing engagement with one another.
2. An actuator according to claim 1, wherein the face gear includes
a series of teeth, each of which extends radially of the face
gear.
3. An actuator according to claim 2, wherein the tip of each tooth
tapers in width from a maximum relatively close to an axis of
rotation of the face gear to a minimum remote therefrom.
4. An actuator according to claim 2, wherein the root of each tooth
tapers in width from a minimum relatively close to the axis of
rotation and the face gear to a maximum remote therefrom.
5. An actuator according to claim 1, wherein the gear arrangement
is a dry running gear arrangement.
6. An actuator according to claim 1, wherein the linearly
extendable actuator device comprises a screw jack device.
7. An actuator according to claim 6, wherein the screw jack device
incorporates dry running and/or sealed-for-life bearings.
8. An actuator according to claim 6, wherein the screw jack device
includes a dry running no-back device.
9. An actuator according to claim 1, further comprising a motor
arranged to transmit drive to the actuator and to at least one
further actuator.
Description
[0001] This invention relates to an actuator, and in particular to
an actuator suitable for use in a thrust reverser system for an
aircraft.
[0002] It is commonplace to provide each engine of an aircraft with
a thrust reverser system to assist in the deceleration of the
aircraft on landing. A typical thrust reverser system comprises a
series of movable components each of which is driven between a
stowed, inactive position and a deployed, operative position by
associated actuators when deployment of the thrust reverser system
is instructed, for example by a control unit controlling operation
of the engine. Typically four or six such actuators are provided.
Traditionally, the actuators used in such applications have taken
the form of linear hydraulic actuators. However, such actuators are
typically heavy. Further, the need to provide high pressure pipe
work between the actuators and the associated pumps adds additional
weight and complexity to the system.
[0003] Rather than use hydraulic actuators, it is known to use
electrically driven actuators. One form of such an actuator is
described in U.S. Pat. No. 5,960,626 and comprises an electrically
powered motor, the output shaft of which drives an input of a
linear screw actuator. The provision of separate motors associated
with each actuator has significant weight penalties and the control
arrangement necessary to ensure that all of the actuators
associated with the thrust reverser system operate in synchronism
is also required to be of complex form.
[0004] To reduce the weight and complexity of such arrangements, it
is known to transmit drive to several actuators from a single
motor, for example using flexible drive shafts and associated
gearboxes. An arrangement of this type is described in U.S. Pat.
No. 4,522,358, this arrangement using a hydraulic motor.
[0005] Where gearboxes are provided, the gears are lubricated to
reduce wear and improve the performance of the gearbox. The
lubricants used in such applications become extremely viscous when
at low temperatures. Where an aircraft has been at high altitude
for a relatively long period of time, the lubricant temperature may
fall to a very low temperature, for example, approximately
-50.degree. C. The viscosity of the lubricant at such low
temperatures is sufficient to cause significant drag within the
gearbox which must be overcome by the operation of the motor. Where
driven by linear hydraulic actuators, these loads are relatively
easy to accommodate as sufficient excess hydraulic power to
overcome the drag loads is present. However, where electrically
powered motors are used, the motor and associated control equipment
is typically required to be of increased size, to ensure that the
drag loads can be accommodated, increasing the cost of the system
and incurring additional weight penalties due to the requirement
for the components driven by the higher power capability of the
motor to be larger and heavier to resist damage from potentially
greater loads. Further, the lubricant itself adds to the
maintenance requirements and weight of the system.
[0006] The gearboxes used in such systems typically use
straight-toothed bevel gears. Such gears are advantageous in that
relatively little sliding contact occurs between the teeth in use,
most contact being rolling contact, with the result that when
properly lubricated they can remain in a serviceable condition for
a long time. However, if operated under load for significant
periods of time with inadequate lubrication, considerable wear
occurs. Further, in order to correctly locate the gears it is
important to ensure that the two axes of rotation are accurately
positioned relative to one another, and that the axial positions of
the gears are correct. Assembly is thus complex. Additionally, the
bearings supporting the gears have to be able to withstand the
separating loads which are generated between the gears when large
torques are transmitted therebetween. As a result, the bearings are
larger and heavier than would otherwise be the case.
[0007] Rather than use straight-toothed bevel gears, spiral bevel
gears are increasingly being used in some applications as they are
quieter running and more readily available. However, they are
susceptible to considerable levels of wear when inadequately
lubricated and, unlike straight-toothed arrangements, are not of
good bi-directional efficiency.
[0008] It is an object of the invention to provide an actuator in
which at least some of the disadvantages set out hereinbefore are
overcome or are of reduced effect.
[0009] According to the present invention there is provided an
actuator comprising a gear arrangement operatively connected to a
rotatable input of a linearly extendable actuator device, wherein
the gear arrangement comprises a pinion gear and a face gear in
meshing engagement with one another.
[0010] The use of such a gear arrangement is advantageous in that
assembly is simplified and that torque transmission results in the
application of fewer axial or side loadings to the gears, thus
permitting a reduction in the size of the associated bearings.
[0011] The face gear conveniently includes a series of co-planar
teeth, each of which extends radially of the face gear. The tip of
each tooth is preferably of tapering width, tapering from a maximum
close to the axis of rotation of the face gear to a minimum remote
therefrom. The root of each tooth preferably tapers in thickness
from a maximum remote from the axis of rotation to a minimum closer
to the axis of rotation.
[0012] Preferably the gear arrangement is a dry running gear
arrangement. The absence of lubricant is advantageous in that the
low temperature viscosity problems are reduced, allowing a smaller
motor to be used. Further, maintenance requirements are reduced and
the weight of the lubricant is saved.
[0013] The linearly extendable actuator device preferably comprises
a screw jack device. Preferably the screw jack device incorporates
dry running and/or sealed for life bearings, thereby reducing
servicing of the actuator.
[0014] Conveniently a single motor is arranged to transmit drive to
several actuators. Flexible drive shafts may be used in the
transmission of drive to the actuators.
[0015] The gear arrangement preferably provides a reduction in
rotary speed, for example by a factor of around 2. Thus, the motor
may be arranged to rotate at a speed of around 7000 rpm whilst the
input of the linearly extendable actuator device may be driven at a
speed of around 3500 rpm.
[0016] The invention will further be described, by way of example,
with reference to the accompanying drawings, in which:
[0017] FIGS. 1 and 2 are sectional views illustrating an actuator
in accordance with an embodiment of the invention; and
[0018] FIG. 3 is a perspective view of the face gear of the
embodiment shown in FIGS. 1 and 2.
[0019] The actuator illustrated in FIGS. 1 and 2 comprises a
linearly extendible actuator device in the form of a screw jack 10
having a rotary drive input 12 to which drive is supplied, in use,
through a gear arrangement 14. The screw jack 10 comprises a nut
component 16, only part of which is visible in the accompanying
drawings, which is formed integrally with or rigidly secured to the
drive input 12 and supported for rotation within a housing 18 by
means of bearings 20. The bearings 20 serve not only to support the
nut component 16 for rotation, but also serve as thrust bearings,
limiting axial movement of the nut component 16. The bearings 20
are preferably of dry-running or sealed-for-life form, and thus do
not require lubrication during servicing.
[0020] An output shaft 22 is in threaded engagement with the nut
component via a ball or roller screw coupling (not shown). The
shaft 22 is mounted to a component to be driven for movement by the
actuator, the mounting of the shaft 22 being such that it is held
against angular movement.
[0021] In use, rotation of the drive input 12 and nut component 16
causes axial movement of the shaft 22, thereby driving the
component to which the shaft 22 is mounted for movement between its
stowed and deployed positions.
[0022] A no-back device 24 is provided, the no-back device 24 being
arranged to allow substantially unrestricted rotational movement of
the drive input 12 and nut component 16 in one rotary direction,
but to apply a braking load to resist externally applied aiding
loads acting on the actuator in the reverse direction. The no-back
device 24 comprises a stainless steel ratchet disc 26 which
encircles the drive input 12. The ratchet disc 26 is formed, about
its periphery, with a series of ratchet teeth with which pawls 28
pivotally mounted to the housing 18 are engageable. A flange
arrangement 30 is mounted upon the drive input 12 so as to be
rotatable therewith, a carbon brake disc 32 being interposed
between the arrangement 30 and the ratchet disc 26. In use, the
carbon brake disc 32 engages the ratchet disc 26, urging the
ratchet disc 26 to rotate with the drive input 12. As a result,
rotation of the drive input 12 in a first direction results in
rotation of the ratchet disc 26, such movement being permitted by
the pawls 28, the pawls riding up and over the ratchet teeth of the
ratchet disc 26 when the ratchet disc 26 rotates in this
direction.
[0023] When the drive input 12 is rotated in the reverse direction,
it will be appreciated that rotation of the ratchet disc 26 is
resisted by the engagement of the pawls 28 with the ratchet teeth
of the ratchet disc 26. Rotation of the drive input 12 in this
reverse direction is thus resisted by the braking load resulting
from the engagement of the brake disc 32 with the ratchet disc
26.
[0024] The no-back device 24 is intended to be of dry-running,
non-lubricated form. In order to withstand the wear and high
temperatures which may occur in use, the ratchet disc 26 is
conveniently of Pyrowear.RTM. (Carpenter Technology Corp.) or a
similar material having a high degree of hardness and a capability
for maintaining those qualities during high temperature
operation.
[0025] As described in co-pending British Patent Application Nos.
0817775.0 and 0821678.0, a lock arrangement 48 may be provided to
secure the drive input 12 against rotation, thereby locking the
actuator 10 against movement, other than when desired.
[0026] The gear arrangement 14 comprises a pinion gear 36 supported
by bearings 38 for rotation relative to the housing 18. Although
not illustrated, the pinion gear 36 is arranged to be driven for
rotation by a flexible drive shaft which, in turn, is driven for
rotation by an associated electric motor. The motor may also be
used to drive a number of actuators 10. The pinion gear 36 includes
teeth 40 which mesh with the teeth 42 provided on a face gear 44.
The face gear 44 is illustrated most clearly in FIG. 3. As shown in
FIGS. 1 and 2, the face gear 44 is splined or otherwise secured to
the drive input 12 such that rotation of the pinion gear 36 and
face gear 44 is transmitted to the drive input 12. Bearings 46
support the face gear 44 for rotation. The bearings 46 are
conveniently of dry-running or sealed-for-life form.
[0027] The face gear 44 includes an end face 44a of planar form in
which the teeth 42 are formed by machining, for example using a
technique similar to that described in U.S. Pat. No. 5,823,857.
Each tooth 42 extends radially, the teeth being co-planar with one
another, and is profiled in such a manner as to achieve meshing
with the teeth 40 of the pinion gear 36. As shown in FIG. 3, the
tip of tooth 42 tapers from a maximum width at its end closest to
the axis of rotation to a minimum at its end furthest from the axis
of rotation. The root of each tooth 42 tapers in width in the
opposite direction. It will thus be appreciated that the teeth 42
are of relatively complex profile.
[0028] The gear arrangement 14 comprising the pinion gear 36 and
face gear 44 is a dry running, non lubricated gear arrangement. It
will thus be appreciated that unlike many common gear arrangements,
the part of the housing 18 containing the pinion gear 36 and face
gear 44 is not provided with lubricating grease or the like. The
absence of lubricating grease or other lubricant materials in this
part of the housing 18 is advantageous in that the problems
resulting from the viscosity of the lubricant material increasing
at low temperatures, thereby causing drag, are avoided. As a
result, the motor used to drive the actuator 10, and the associated
control arrangement, can be of reduced size and power output
allowing further weight savings to be made in the actuators,
linkages and other components driven by the motor. Additionally,
maintenance requirements are reduced and the weight of the
lubricants is saved.
[0029] In addition to the system weight savings that can be made by
using an actuator including a face gear arrangement, the
arrangement 14 of the invention has other advantages. For example,
assembly of the gear arrangement is simplified as accurate
adjustment of the gears is only required along a single axis. The
axial position of the pinion gear 36 is not critical to the
operation of the gear arrangement, thus only the axial position of
the face gear 44 requires accurate positioning. Further, in use,
there are no axial separating forces applied to the pinion gear 36
thus the provision of bearings countering such movement can be
avoided. Similarly, the application of significant side loadings on
the face gear 44 during torque transmission is avoided thus the
bearings 46 associated with the face gear can be of reduced size,
providing further weight savings. Additionally, servicing and
maintenance procedures are simplified.
[0030] The ability to run the gear arrangement 14 without lubricant
largely arises from the fact that with such a gear arrangement the
contact between the pinion gear 36 and the face gear 44 is
primarily a rolling contact, virtually no rubbing or sliding
contact occurring between the teeth. In other words, the relative
velocities of the contacting surfaces of the pinion gear 36 and
face gear 44 are substantially zero throughout the period of
contact therebetween. The absence of sliding or rubbing contact
between the pinion gear 36 and face gear 44 allows the running of
the gear arrangement 14 without lubricant and this results in
reduced drag.
[0031] It is currently envisaged that, in use, the pinion gear 36
will be rotated at speeds of approximately 7000 rpm. The gear
arrangement 14 provides a 2:1 reduction in speed, thus the face
gear 44 and drive input 12 of the actuator 10 will typically be
driven at speeds of approximately 3500 rpm. To achieve this
reduction, it is envisaged that the pinion gear will have 16 teeth
whilst the face gear will have 31 teeth. However this need not
always be the case.
[0032] A range of modifications and alterations to the arrangement
described hereinbefore may be made without departing from the scope
of the invention.
* * * * *