U.S. patent application number 10/266710 was filed with the patent office on 2004-04-08 for force-limiting rotary lock.
This patent application is currently assigned to Moog Inc.. Invention is credited to Gitnes, Seth E., House, William H., Nakashima, Kenneth K., Polcuch, Eric A..
Application Number | 20040065522 10/266710 |
Document ID | / |
Family ID | 32042711 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040065522 |
Kind Code |
A1 |
Gitnes, Seth E. ; et
al. |
April 8, 2004 |
FORCE-LIMITING ROTARY LOCK
Abstract
A force-limiting rotary lock (20) for a shaft (21) mounted on a
housing (22) for rotational and axial movement relative thereto,
broadly includes a lug member (28) provided on the shaft, and a
pawl (51) mounted on the housing. The pawl is movable relative to
the housing between first and second positions. The pawl is
operatively arranged to engage the lug when the pawl is in its
first position (shown in FIG. 3) to prevent further rotation of the
shaft in one angular direction, and to be disengaged from the lug
when the pawl is in its second position (shown in FIG. 2) to permit
rotation of the shaft in either angular direction. A cam (25) is
mounted on the shaft, and a follower (49) is mounted on the housing
for selectively moving the pawl between the first and second
positions when the shaft is axially displaced from its
predetermined position. When the shaft is axially displaced from
its predetermined position and the pawl engages the lug, the shaft
will be prevented from rotating further in the one angular
direction.
Inventors: |
Gitnes, Seth E.; (Everett,
WA) ; House, William H.; (Torrance, CA) ;
Nakashima, Kenneth K.; (Issaquah, WA) ; Polcuch, Eric
A.; (San Pedro, CA) |
Correspondence
Address: |
PHILLIPS LYTLE LLP
INTELLECTUAL PROPERTY GROUP
3400 HSBC CENTER
BUFFALO
NY
14203-3509
US
|
Assignee: |
Moog Inc.
|
Family ID: |
32042711 |
Appl. No.: |
10/266710 |
Filed: |
October 8, 2002 |
Current U.S.
Class: |
192/223.1 |
Current CPC
Class: |
Y10T 74/18704 20150115;
F16H 25/2021 20130101 |
Class at
Publication: |
192/223.1 |
International
Class: |
F16D 059/00 |
Claims
What is claimed is:
1. A rotary lock for a shaft mounted in a housing for rotational
movement about an axis, said shaft being axially movable relative
to said housing and being biased to move toward a predetermined
axial position, comprising: at least one member provided on one of
said shaft and housing; a pawl mounted on the other of said shaft
and housing, said pawl being movable relative to said other of said
shaft and housing between first and second positions; wherein said
pawl is operatively arranged to engage said member when said pawl
is in said first position to prevent further rotation of said shaft
in one angular direction, and to be disengaged from said member
when said pawl is in said second position to permit rotation of
said shaft in either angular direction; a cam mounted on one of
said shaft and housing; a follower operatively arranged to engage
said cam as said shaft is rotated when said shaft is axially
displaced from said predetermined position to selectively move said
pawl between said first and second positions and; such that when
said shaft is axially displaced from said predetermined position
and said pawl engages said member, said shaft will be prevented
from rotating further in said one angular direction.
2. A rotary lock as set forth in claim 1 wherein, when said shaft
is prevented from rotating in said one angular direction, said
shaft is not prevented from rotating in the opposite angular
direction.
3. A rotary lock as set forth in claim 2 wherein, when said shaft
is prevented from rotating in said one angular direction, said pawl
is retained in said first position independently of the axial
position of said shaft.
4. A rotary lock as set forth in claim 2 wherein, as said shaft is
rotated in said opposite angular direction and said shaft is not
axially displaced, said pawl will be moved from said first position
to said second position.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to force limiters,
and, more particularly, to an improved force-limiting rotary lock
that is particularly adapted to be utilized on an aircraft between
a driving shaft and one or more airfoil surfaces, such as flaps,
slats and the like.
BACKGROUND ART
[0002] In fixed wing aircraft, flaps are used to redefine the
contour of the wing during takeoff and landing. In some cases, a
ball screw actuator is used to drive a rotary shaft that controls
movement of a plurality of individual flaps that are spaced along
the wing. It is generally desirable to provide a force limiter to
prevent damage to the actuator structure in the event that an
overload condition is sensed.
[0003] Various types of rotary locking mechanisms are shown and
described in U.S. patent application Ser. No. 09/778,600, filed
Feb. 7, 2001, which is assigned to the assignee of the present
application, and in U.S. Pat. Nos. 6,109,415, 4,697,672, 4,579,
201, 3,898,817 and 5,582,390. The aggregate disclosures of this
application and these patents are hereby incorporated by
reference.
DISCLOSURE OF THE INVENTION
[0004] With parenthetical reference to the corresponding parts,
portions or surfaces of the disclosed embodiment, merely for
purposes of illustration and not by way of limitation, the present
invention provides an improved force-limiting rotary lock (20) for
a shaft (21) mounted in a housing (22) for rotational movement
about an axis (x-x). The shaft is also axially movable relative to
the housing, and is biased (via Belleville spring stacks 33, 34) to
move toward a predetermined axial position relative to the housing.
The improved rotary lock broadly comprises: at least one member
(28) provided on one of the shaft and housing; a pawl (51) mounted
on the other of the shaft and housing, the pawl being movable
relative to the member (28) between first and second positions;
wherein the pawl is operatively arranged to engage the member when
the pawl is in the first position (e.g., as shown in FIG. 3) to
prevent further rotation of the shaft in one angular direction, and
is operatively arranged to be disengaged from the member when the
pawl is in the second position (e.g., as shown in FIG. 2) to permit
rotation of the shaft in either angular direction; a cam (25)
mounted on one of the shaft and housing; a follower (49) associated
with the pawl for selectively moving the pawl between the first and
second positions, and operatively arranged to engage the cam when
the shaft is axially displaced from the predetermined position such
that when the shaft is axially displaced from the predetermined
position and the pawl (51) engages the member (28), the shaft will
be prevented from rotating further in the one angular
direction.
[0005] In the illustrated embodiment, each member (28) is a lug or
dog that extends outwardly from the shaft. However, in an
alternative arrangement, such members (be they dogs, lugs or
otherwise) could be mounted on the housing.
[0006] Also, in the preferred embodiment, the device is shown as
having a single pawl (51) which is operatively mounted for
selective movement between any one of three spring-biased
positions: a first position (e.g., as shown in FIG. 3) in which the
pawl (51) engages a member (28) to prevent rotation of the shaft in
one angular direction, a second position (e.g., as shown in FIG. 2)
in which the pawl is disengaged from such member and permits
rotation of the shaft in either angular direction, and a third
position in which the pawl engages a member (28) and prevents
further rotation in the opposite angular direction. However, in an
alternative embodiment, multiple pawls could be provided.
[0007] When the shaft is prevented from rotating in one angular
direction, the shaft is not prevented from rotating in the opposite
angular direction. Moreover, when the shaft is prevented from
rotating in the one angular direction, the pawl is retained in its
position independently of the axial position of the shaft. When the
pawl is in its first or locked position (i.e., to prevent further
rotation in the one angular direction), and the shaft is rotated in
the opposite angular direction, even when the shaft is not axially
displaced, the pawl will be moved from its locked or first position
to its unlocked or second position.
[0008] Accordingly, the general object of the invention is to
provide an improved force-limiting rotary lock.
[0009] Another object is to provide a force-limiting rotary lock
for use in controlling airfoil surfaces, such as flaps, slats and
the like.
[0010] These and other objects and advantages will become apparent
from the foregoing and ongoing written specification, the drawings,
and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a perspective cutaway view of the improved
force-limiting rotary lock, this view showing the shaft, the
housing, the lug-like members, and the pawl.
[0012] FIG. 2 is a fragmentary vertical sectional view thereof,
taken generally on line 2-2 of FIG. 1, showing the pawl as being in
its disengaged or second position.
[0013] FIG. 3 is a view generally similar to FIG. 2, but showing
the pawl as having been moved from its unlocked or second position
to its first or locked position, and further showing the pawl as
operatively engaging one of the lug-like members to prevent further
rotation of the shaft in a counterclockwise direction.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] At the outset, it should be clearly understood that like
reference numerals are intended to identify the same structural
elements, portions or surfaces, consistently throughout the several
drawing figures, as such elements, portions or surfaces may be
further described or explained by the entire written specification,
of which this detailed description is an integral part. Unless
otherwise indicated, the drawings are intended to be read (e.g.,
cross-hatching, arrangement of parts, proportion, degree, etc.)
together with the specification, and are to be considered a portion
of the entire written description of this invention. As used in the
following description, the terms "horizontal", "vertical", "left",
"right", "up" and "down", as well as adjectival and adverbial
derivatives thereof (e.g., "horizontally", "rightwardly",
"upwardly", etc.), simply refer to the orientation of the
illustrated structure as the particular drawing figure faces the
reader. Similarly, the terms "inwardly" and "outwardly" generally
refer to the orientation of a surface relative to its axis of
elongation, or axis of rotation, as appropriate.
[0015] Referring now to the drawings, and, more particularly, to
FIG. 1 thereof, the present invention broadly provides an improved
force-limiting rotary lock, of which the presently-preferred
embodiment is schematically indicated at 20. This embodiment
broadly includes a horizontally-elongated shaft, generally
indicated at 21, which is operatively mounted within a housing,
generally indicated at 22. More particularly, shaft 21 is mounted
for both rotational and axial movement relative to the housing.
[0016] The shaft is shown as having a generally horizontal axis
x-x. The shaft has an external screw thread, schematically
indicated at 23, at its left marginal end portion; a collar portion
24 spaced rightwardly from the screw thread; a plurality of cam
members, severally indicated at 25, extending outwardly from a
portion of the shaft; an annular disk-like member 26 provided with
four circumferentially-spaced dog- or lug-like members 28 extending
radially outwardly therefrom; and a series of splined teeth 29
operatively engaging a mating set of splined teeth on a driving
member 30. Member 30 is arranged-to be rotated about axis x-x by a
suitable mechanism (not shown). Because of the splined connection,
shaft 21 is constrained to rotate with member 30, but is permitted
to move axially relative to driving member 30 and housing 22.
[0017] Screw thread 23 at the left end of the shaft is operatively
connected to a screw-and-nut mechanism (not shown) for driving
another member or element (not shown). As long as the reaction
force from the screw-and-nut mechanism is less than the preload on
Belleville springs 36 or 38 (as described in detail below), there
will be no discernable axial movement of the shaft relative to the
housing. However, should such driven member lock up for any reason,
then continued rotation of shaft 21 will produce a reaction force
in excess of the preload, and thus cause axial movement of shaft 21
relative to housing 22.
[0018] The housing is shown as being a horizontally-elongated
specially-configured tubular member that is penetrated by the
shaft. The housing has a leftward portion 31 of reduced diameter,
and a rightward portion 32 of enlarged diameter. The housing
leftward portion 31 has two axially-spaced chambers 33, 34
separated by an inwardly-extending annular portion 35. A Belleville
spring stack 36 is arranged in left chamber 35, and another
Belleville spring stack 38 is arranged in right chamber 34. These
two Belleville spring stacks act via preload-adjusting shims 39, 40
on shaft collar portion 24, and urge the shaft to move toward a
predetermined axial position relative to the housing. Shims 39 and
40 are selected to provide the desired preload on the respective
springs, and need not be of the same axial thickness. Indeed, they
may be of different axial thicknesses, depending on the particular
application.
[0019] The housing enlarged-diameter portion 32 is shown as having
(from left to right in FIG. 1): a rightwardly-facing annular
vertical wall 41, an inwardly-facing horizontal cylindrical wall 42
extending rightwardly therefrom, a leftwardly-facing annular
vertical surface 43, an inwardly-facing horizontal cylindrical
surface 44, a rightwardly-facing annular vertical surface 45, an
inwardly-facing horizontal cylindrical surface 46, and an
leftwardly-facing annular vertical surface 48. The cam members 25
are arranged in two axially-spaced groups of four each, with the
cam members of each group being spaced equidistantly about the
shaft axis by intervals of about 90 degrees. Thus, there are a
total of eight cam members 25, and these extend outwardly so as to
face toward housing surface 44. Disk member 26 is arranged in the
housing recess defined between surfaces 45, 46 and 48. As
previously indicated, member 26 is an annular disk-like member from
which four lug-like members 28 extend radially outwardly. These
four members are spaced equidistantly about the outer cylindrical
surface of disk member 26.
[0020] Cam follower 49 is mounted on the left marginal end portion
of a rod 50 that is pivotally mounted in a hole that extends
between housing surfaces 43 and 45. Follower 49 is mounted on one
end of rod 50, and a pawl 51 is mounted on the other end of this
rod. Follower 49 has a inner portion 52 that is normally arranged
to be axially positioned between the axially-spaced cams 25, 25.
Thus, when the shaft is in its predetermined axial position
relative to the housing and driving member 30 is rotated, shaft 21
will rotate and will cause the desired movement of the flap. In
other words, during normal operation, the shaft will rotate in
response to an input from driving member 30, but will not move
axially relative to the housing.
[0021] However, in the event that the flap drive becomes jammed,
such impeded movement of the drive will be transmitted back through
screw thread 23 and will cause axial shifting of shaft 21. As this
occurs, the inner end of follower 49 will be engaged by one of the
cams 25. Continued rotation of the shaft will cause follower 49 to
pivot about the axis of rod 50, and will cause pawl 51 to move from
its second or unlocked position (as shown in FIG. 2)to its first or
biased locked position (as shown in FIG. 3).
[0022] As best shown in FIGS. 2 and 3, the pawl is a
specially-configured member having three concave recesses 53, 54
and 55, respectively. A ball 56 is mounted on the housing and is
biased by a spring 58 to move toward the pawl and to snap into one
of recesses 53, 54 or 55.
[0023] When the shaft is in its predetermined axial position
relative to the housing, normal rotational movement of the shaft
does not cause any movement of pawl 51. Thus, the pawl is normally
retained in its unlocked or second position, as shown in FIG. 2.
However, should the shaft move in either axial direction, as by a
flap being overloaded or locked up and the threaded connection
causing axial shifting of the shaft within the housing, follower 49
will engage the cams 25 on the axially-shifted shaft and will pivot
the pawl from its unlocked position (shown in FIG. 2) to its
alternative locked position (shown in FIG. 3). In this condition,
the locked position of the pawl will preclude further rotation of
the shaft in the same direction by blocking one of the lugs 28 on
disk 26, this being shown as being counter-clockwise in FIG. 3.
[0024] However, even when locked against further rotation in one
angular direction, the shaft is free to rotate in the opposite
(i.e., clockwise) angular direction. As this occurs, the advancing
lug will then engage the off-center pawl and return it from its
locked position back to its normal position.
[0025] It should be noted that the design shown in FIGS. 1-3 is
capable of locking the shaft against further rotation in the event
of a overload, in either angular direction, with the shaft in all
cases being free to be moved in opposite angular direction so as to
selectively unlock the mechanism.
[0026] Thus, the invention provides an improved force-limiting
rotary lock for a shaft mounted on a housing.
[0027] Modifications
[0028] As indicated above, many changes and modifications may be
made. For example, the form illustrated in the drawings is intended
to be viewed as a schematic. The actual implementation of this
schematic may take varied and other forms. While it is presently
preferred to use opposed Belleville spring stacks with
preload-adjusting shims, other types of centering devices may be
used. Similarly, other types of cams and followers may be used. The
pawl may be mounted on either the shaft or the housing, with the
lugs being mounted on the other of the shaft and housing.
Connections other than the splined connection may be substituted
therefor.
[0029] Therefore, while the presently preferred form of the
improved force-limiting rotary lock has been shown and described,
and certain changes and modifications thereof discussed, persons
skilled in this art will readily appreciate that various additional
changes and modifications may be made without departing from the
spirit of the invention, as defined and differentiated by the
following claims.
* * * * *