Title: Mechanical override release mechanism for cable tensioning systems
Abstract: The release mechanism includes a hollow abutment member fastened to one end of the flexible outer conduit of the cable. The abutment member is mounted for sliding movement in a housing, but is normally prevented from sliding by a stop member associated with the housing for engaging a shoulder on the abutment member. The stop member establishes a reaction surface against which the abutment member and outer conduit bear when the cable is tensioned. An actuating mechanism is provided to selectively move the stop member so that the stop member is out of engagement with the shoulder of the abutment member, for example by a rotary movement, to permit axial movement of the abutment member in the housing when it is desired to release tension in the cable.
Patent Number: 6,840,133 Issued on 01/11/2005 to Aubrey, et al.
| Inventors:
|
Aubrey; Michael Richard (Gloucester, GB);
Botham; Alan Samuel (Worcestershire, GB);
Capolongo; Roberto (Worcester, GB);
Williams; Neil Dean (Worcestershire, GB)
|
| Assignee:
|
Dura Global Technologies, Inc. (Rochester Hills, MI)
|
| Appl. No.:
|
225750 |
| Filed:
|
August 22, 2002 |
Foreign Application Priority Data
| Current U.S. Class: |
74/531; 188/2D |
| Intern'l Class: |
G05G 005/06 |
| Field of Search: |
74/501.5 R,527,529,531
188/2 D
403/321,322.1,322.3
|
References Cited [Referenced By]
U.S. Patent Documents
| 3729070 | Apr., 1973 | Le Marchand | 188/170.
|
| 5590744 | Jan., 1997 | Belmond | 188/265.
|
| 6386338 | May., 2002 | Powrozek | 188/156.
|
| 6533082 | Mar., 2003 | Gill et al. | 188/156.
|
| 6609595 | Aug., 2003 | Flynn et al. | 188/156.
|
Primary Examiner: Bucci; David
Assistant Examiner: McAnulty; Timothy
Attorney, Agent or Firm: Mescher; Richard M., Wright; Porter, Watson; Dean B.
Claims
What is claimed is:
1. An override mechanism for a cable tensioning mechanism in which a cable
is tensioned by a motor against the reaction thrust of a flexible outer
conduit for the cable, the release mechanism comprising:
a hollow abutment member fastened to one end of the flexible outer conduit
of the cable, the cable passing through the hollow center of the abutment
member for connection to a motor-actuated tensioning drive nut;
a housing in which the abutment member can slide axially;
a stop member associated with the housing for engaging with a shoulder on
the abutment member for arresting sliding movement of the abutment member
in the housing and establishing a reaction surface against which the
abutment member and the outer conduit bear when the cable is tensioned;
and
means for selectively moving the stop member so that the stop member is out
of engagement with the shoulder of the abutment member to permit axial
movement of the abutment member in the housing when it is desired to
release the tension in the cable.
2. The override mechanism according to claim 1, wherein the movement to
take the stop member out of engagement with the shoulder of the abutment
is a rotary sliding movement of the stop member.
3. The override mechanism according to claim 2, wherein the abutment member
comprises at least a portion which is non-cylindrical in shape, the
shoulder on the abutment member being defined by an axial end of the
non-cylindrical portion, the stop member comprising a sleeve within the
housing having a non-cylindrical channel therein of a size and shape
complementary to the size and shape of the non-cylindrical portion of the
abutment member, and the means for selectively moving the stop member
comprises means for rotating the stop member from an angular condition in
which the shapes of the non-cylindrical portion of the abutment member and
the non-cylindrical channel are out of alignment and the abutment member
is thus prevented from entering the channel, to an angular condition in
which the shapes are in alignment and the abutment member can enter the
channel to relieve tension in the cable.
4. The override mechanism according to claim 3, wherein the abutment member
further comprises a cylindrical guide portion of a diameter less than the
maximum width of the non-cylindrical portion of the abutment member, and
the shoulder on the abutment member is defined by a junction between the
non-cylindrical portion and the cylindrical guide portion of the abutment
member.
5. The override mechanism according to claim 3, wherein the housing
comprises a guide portion cooperating with the non-cylindrical portion of
the abutment member to prevent angular rotation thereof.
6. The override mechanism according to claim 3, wherein the non-cylindrical
portion of the abutment member is hexagonal in shape.
7. The override mechanism according to claim 1, wherein the means for
selectively moving the stop member out of engagement with the shoulder of
the abutment member comprises a cable actuating mechanism acting to move
the stop member against the bias of a return spring.
8. The override mechanism according to claim 1, wherein the means for
selectively moving the stop member out of engagement with the shoulder of
the abutment member comprises a motor-operated actuating mechanism.
9. The override mechanism according to claim 1, wherein the stop member is
movable relative to the housing by the moving means.
10. An override mechanism for a cable tensioning mechanism in which a cable
is tensioned by a motor against the reaction thrust of a flexible outer
conduit for the cable, the release mechanism comprising:
an abutment member fastened to one end of the flexible outer conduit of the
cable, the cable passing through the abutment member for connection to a
motor-actuated tensioning drive nut;
a housing in which the abutment member can move;
a stop member associated with the housing for engaging the abutment member
to arrest movement of the abutment member in the housing and establish a
reaction surface against which the abutment member and the outer conduit
bear when the cable is tensioned; and
an actuator operably connected to the stop member to selectively move the
stop member between a first position wherein the stop member is in
engagement with the abutment member to arrest movement of the abutment in
the housing and establish the reaction surface and a second position
wherein the stop member is out of engagement with the abutment member to
permit movement of the abutment member in the housing and release the
tension in the cable.
11. The override mechanism according to claim 10, wherein the stop member
moves between the first and second positions with rotary sliding movement.
12. The override mechanism according to claim 11, wherein the abutment
member comprises at least a portion which is non-cylindrical in shape and
a shoulder defined by an axial end of the non-cylindrical portion, the
stop member comprises a sleeve within the housing having a non-cylindrical
channel therein of a size and shape complementary to the size and shape of
the non-cylindrical portion of the abutment member, and the actuator
rotates the stop member between an angular condition in which the
non-cylindrical portion of the abutment member and the non-cylindrical
channel are out of alignment preventing the abutment member from entering
the channel and an angular condition in which the non-cylindrical portion
of the abutment member and the non-cylindrical channel are in alignment
allowing the abutment member to enter the channel and relieve tension in
the cable.
13. The override mechanism according to claim 12, wherein the abutment
member further comprises a cylindrical guide portion of a diameter less
than the maximum width of the non-cylindrical portion of the abutment
member, and the shoulder on the abutment member is defined by a junction
between the non-cylindrical portion and the cylindrical guide portion of
the abutment member.
14. The override mechanism according to claim 12, wherein the housing
comprises a guide portion cooperating with the non-cylindrical portion of
the abutment member to prevent angular rotation thereof.
15. The override mechanism according to claim 12, wherein the
non-cylindrical portion of the abutment member is hexagonal in shape.
16. The override mechanism according to claim 10, wherein the actuator
comprises a cable actuating mechanism acting to move the stop member
against the bias of a return spring.
17. The override mechanism according to claim 10, wherein the actuator
comprises a motor-operated actuating mechanism.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO MICROFICHE APPENDIX
Not Applicable
FIELD OF THE INVENTION
This invention relates to override release mechanisms for cable tensioning
systems such as electrically actuated cable brake mechanisms of
automobiles. A typical electrically actuated cable brake mechanism would
be a mechanism for actuating a parking brake either automatically whenever
the engine stops (in which case the conventional hand or foot-operated
parking brake lever of the vehicle becomes redundant and may be omitted
from the vehicle design) or as a parking brake override mechanism in the
event the parking brake is not properly applied and vehicle movement is
sensed. Other cable tensioning systems can be found in a variety of
control systems, mainly but not extensively in the field of transport
where the cable tensioning systems are often used for brake actuation.
BACKGROUND OF THE INVENTION
A (non-limiting) example of a cable tensioning system with which the
override release mechanism of the invention can be used is a known
electrically actuated cable brake mechanism which comprises a cable
tensioning drive nut threaded onto a lead screw. A motor rotates the lead
screw on instructions from an electronic control unit (ECU) to cause
tensioning of a brake cable when it is desired to actuate the brake. The
reaction force to cable movement is established through a flexible outer
conduit for the cable.
Other malfunctions that might prevent the intended brake release would be a
loss of power from the vehicle battery, an electrical fault in the ECU, a
fault in the wiring connecting the ECU to the motor driving the lead
screw, failure in the motor itself, damage to the bearings mounting the
lead screw, or damage to one or more of the gears between the driving
motor and the lead screw. If any of the above faults takes place while the
brakes are engaged, then in the absence of an override release mechanism,
the vehicle is immobilized and cannot even be towed to a garage for
repair.
It has been proposed to provide a flexible drive shaft from a manual
control wheel to a shaft of the electric motor driving the electrically
activated cable brake mechanism, so that in the event of motor failure,
the lead screw can be rotated manually through the drive shaft so as to
release the tension in the cable brake, permitting the vehicle to be towed
to a repair garage. That is, however, only a partial solution to the
problem because if the drive nut is cross-threaded on the lead screw, or
if the brake malfunction is due to a fault in the gear box or a bearing
fault and the electrically actuated cable brake mechanism becomes seized
solid in the brake-applied condition, then no manual hand wheel will
permit the lead screw to be rotated so as to release the cable tension.
It is an object of this invention to provide an override release mechanism
which can rapidly and reliably release the tension in the cable,
irrespective of whether the malfunction in the electrically actuated cable
tensioning mechanism is an electrical malfunction that results in a total
seizure of the cable tensioning mechanism.
SUMMARY OF THE INVENTION
The invention provides an override mechanism for a cable tensioning
mechanism in which a cable is tensioned by a motor against the reaction
thrust of a flexible outer conduit for the cable, the release mechanism
comprising: a hollow abutment member fastened to one end of the flexible
outer conduit of the cable, the cable passing through the hollow center of
the abutment member for connection to a motor-actuated tensioning drive
nut; a housing in which the abutment member can slide axially; a stop
member associated with the housing for engaging with a shoulder on the
abutment member for arresting the sliding movement of the abutment member
in the housing and establishing a reaction surface against which the
abutment member and outer conduit bear when the cable is tensioned; and
means for selectively moving the stop member out of engagement with the
shoulder of the abutment member to permit axial movement of the abutment
member in the housing when it is desired to release the tension in the
cable
In normal use, when the override release mechanism is not actuated, the
cable tensioning mechanism can apply and release the tension in the cable
by moving the tensioning drive nut axially of a lead screw. The lead screw
is conventionally driven from an electric motor acting through a reduction
gearbox, and as the drive nut moves one axial end of the cable in a cable
tensioning direction, so the hollow abutment fastened to that end of the
flexible outer conduit of the cable is in abutment with the stop member so
as to provide the necessary reaction force to establish the operative
tension in the cable. According to the invention if the cable tension is
locked ON for any reason and it is desired to actuate the override release
mechanism, then the stop member is simply moved out of engagement with the
shoulder of the abutment member to permit axial movement of the abutment
member in the housing. The reaction force to the tension in the cable is
therefore released, which releases the cable tension and thus releases the
vehicle parking brake or the other mechanical device engaged by the cable
tension.
Preferably the movement necessary to take the stop member out of engagement
with the shoulder of the abutment member is a rotary sliding movement of
the stop member, but equally the override mechanism can be designed so
that the necessary movement of the stop member is a linear sliding
movement. The important consideration is that when the stop member is in
its operating position, it should engage the shoulder of the abutment
member so as to establish the reaction force to the tensioning of the
cable. When it is moved out of engagement, the abutment member is
permitted to move axially relative to the housing in a
tensioning-releasing direction.
In the case where the movement to take the stop member out of engagement
with the shoulder of the abutment member is a rotary sliding movement, the
abutment member preferably comprises at least a portion which is
non-cylindrical in shape, the shoulder on the abutment member being
defined by an axial end of the portion. The stop member comprises a sleeve
within the housing. The sleeve has a non-cylindrical channel therein of a
size and shape complementary to the size and shape of the non-cylindrical
portion of the abutment member. The means for selectively moving the stop
member comprises means for rotating the sleeve from an angular condition
in which the shapes of the non-cylindrical portion of the abutment member
and the non-cylindrical channel are out of alignment and the abutment
member is thus prevented from entering the channel, to an angular
condition in which the shapes are in alignment and the abutment member can
enter the channel to relieve the tension in the cable. The abutment member
preferably further comprises a cylindrical guide portion of a diameter
less than the maximum width of the non-cylindrical portion of the abutment
member. The shoulder on the abutment member is thus defined by the
junction between the non-cylindrical portion and the cylindrical guide
portion of the abutment member. In such an arrangement he housing itself
preferably includes a guide portion cooperating with the non-cylindrical
portion of the abutment member to prevent angular rotation thereof.
For example, when the non-cylindrical portion of the abutment member is
hexagonal in shape, the end wall of that non-cylindrical portion comprises
six angularly spaced shoulders which in one angular configuration of the
stop member engage an end face of the stop member, preventing axial
movement of the abutment member in the housing. When the stop member is
rotated to bring the hexagonal shapes of the non-cylindrical portion of
the abutment member and the non-cylindrical channel in the sleeve into
angular alignment, then the abutment member enters the channel, moving
axially of the housing so as to relieve the tension in the cable.
The means for moving the stop member out of engagement with the shoulder of
the abutment member may be a two-way electric motor or a lever or cable
actuating mechanism. If a cable actuating mechanism is used, then it
should act against the bias of a return spring so that the after the
jammed or faulty cable tensioning mechanism has been repaired, the
override release mechanism automatically resets as soon as the abutment
member is moved past the stop member into a fully-brake-released
condition.
BRIEF DESCRIPTION OF THE DRAWINGS
These and further features of the present invention will be apparent with
reference to the following description and drawings, wherein:
FIG. 1 is a side view of an electrically actuated cable brake mechanism for
the parking brake of an automobile, illustrated only schematically;
FIG. 2 is an exploded view of the components of the electrically actuated
cable brake mechanism of FIG. 1;
FIG. 3 is an exploded view of the components of an override release
mechanism according to the present invention, for use with the cable brake
mechanism of FIGS. 1 and 2;
FIG. 4 is a perspective view of the assembled override release mechanism of
FIG. 3, shown partly cut-away and sectioned;
FIG. 5 is a perspective view similar to that of FIG. 4 but with the
components in their relative positions and orientations after override
brake release operation;
FIG. 6 is a block diagram of the cable brake mechanism of FIGS. 1 and 2
utilizing the override release mechanism of FIGS. 3 to 5; and
FIG. 7 is a block diagram similar to FIG. 6 but showing an alternative
embodiment of means for selectively moving a stop member of the override
release mechanism.
It should be understood that the appended drawings are not necessarily to
scale, presenting a somewhat simplified representation of various
preferred features illustrative of the basic principles of the invention.
The specific design features of an override release mechanism as disclosed
herein, including, for example, specific dimensions, orientations,
locations, and shapes will be determined in part by the particular
intended application and use environment. Certain features of the
illustrated embodiments have been enlarged or distorted relative to others
to facilitate visualization and clear understanding. In particular, thin
features may be thickened, for example, for clarity or illustration. All
references to direction and position, unless otherwise indicated, refer to
the orientation of the override release mechanism illustrated in the
drawings.
DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
It will be apparent to those skilled in the art, that is, to those who have
knowledge or experience in this area of technology, that many uses and
design variations are possible for the override release mechanism
disclosed herein. The following detailed discussion of various alternative
and preferred embodiments will illustrate the general principles of the
invention with reference to an electrically actuated cable brake mechanism
for the parking brake of an automobile. Other embodiments suitable for
other applications will be apparent to those skilled in the art given the
benefit of this disclosure.
FIG. 1 illustrates schematically the arrangement of a conventional
electrically actuated cable brake mechanism. The mechanism comprises an
electric motor 1, a gear-box 2 and a lead screw 3. The motor 1, controlled
by an ECU 24, drives the lead screw 3 through the gear-box 2.
The housing 4 surrounds the lead screw 3. Threaded onto the lead screw 3 is
a cable tensioning drive nut 5 which also slides on a smooth guide shaft 6
parallel to the lead screw 3, for preventing rotation of the drive nut 5
around the axis of the lead screw and for ensuring even loading and smooth
sliding action of the nut.
An inner cable 7 of a sheathed actuating cable is connected to the
tensioning drive nut, and an outer conduit 8 of the brake cable is
connected to the housing 4. When the tensioning drive nut 5 is moved to
the right as viewed in FIG. 1, the inner cable 7 is pulled to the right
and the outer conduit 8, held by the housing 4, presents a reaction force
for brake actuation.
Although not illustrated in the drawings, it is possible for a single brake
actuating cable to operate both left and right hand wheel brakes of the
vehicle by joining the inner cable 7 and outer conduit 8 to a known
reaction system which uses action and reaction to generate equal braking
forces on the left and right wheel brakes
FIG. 2 shows the components necessary to build an electrically actuated
cable brake mechanism according to FIG. 1, but exploded in format. A power
cable 9 drives the electric motor 1 under the control of an ECU 24
(Figure), a drive shaft 10 links the motor to the elements 2a, 2b and 2c
of the gear-box 2. Also illustrated in FIG. 2 are a gasket 11, an end cap
12 for the gear-box incorporating a Hall effect sensor for detecting
rotation of an intermediate gear 2b of the gear-box, and a feedback wire
12a for relaying back to the ECU 24 information relating to the precise
position of the tensioning nut 5 on the lead screw shaft 3. FIG. 2 also
shows a gasket 13, a gear-box cover 14, a gasket 15, a thrust bearing
assembly 16 comprising two thrust bearing plates separated by a ball
thrust bearing, and a gear-box end cap housing 17. A gasket 18 is provided
between the gear-box assembly 2 and a mounting bracket 19. Bolts 20
connect together the gear-box 2 and the motor 1. Four shorter bolts 21 and
associated nuts 21a connect each screw housing 4 to the mounting bracket
19 with an intermediate gasket 19a.
Buffers 22 are provided one on each side of the tensioning drive nut 5, to
cause re-engagement of the drive nut 5 on the lead screw 3 if it over-runs
from either end of the lead screw under a no-load condition.
FIGS. 3 to 5 illustrate an override release mechanism according to the
invention for use in conjunction with the electrically actuated cable
brake mechanism of FIGS. 1 and 2. The mechanism of FIGS. 3 to 5 is
designed as an add-on for mounting at the distal end of the housing 4 of
the electrically actuated cable brake mechanism of FIGS. 1 and 2, but
clearly exactly the same constructional principles could be used to
manufacture a release mechanism according to the invention which is made
integrally with the electrically actuated cable brake mechanism itself.
The components of the override release mechanism are illustrated in FIG. 3,
and comprise a housing 30, a thrust-bearing assembly 31 comprising two
thrust bearing plates separated by a bearing, a sleeve 32 within the
housing having an abutment face 33, an end cap 34 for the housing, a
rubber boot 35 and a hollow abutment member 36.
The assembly of the above components is illustrated in FIG. 4, which also
shows the brake cable 7 and outer conduit 8 extending from the
electrically actuated cable brake mechanism of FIG. 1. The illustration of
FIG. 4 is in the reverse orientation to that of FIGS. 1 to 3, so that it
is the left-hand side of the housing 30 as illustrated in FIG. 4 which
abuts against the distal end of the housing 4 of FIGS. 1 and 2. The cable
7 runs freely through the hollow abutment member 36 of FIG. 4 and
continues on to the vehicle brakes via a known reaction system. The outer
cable 8 is joined securely to the abutment member 36 which comprises a
cylindrical portion 40 and a portion of hexagonal section 41. The abutment
member 36 is injection molded from a plastics material that is
compression-resistant, with a hard bearing face 42, also of the same
hexagonal section, between the cylindrical and hexagonal portions.
The sleeve 32 within the housing is also injection molded from a
compression-resistant plastics material, and comprises a hollow
cylindrical body portion 43 with a hard bearing face 44 which provides the
abutment face 33. The face 44 is formed with a female hexagonal opening of
precisely the size and shape of the hexagonal hard bearing face 42 of the
hollow abutment member 36. When the two hexagons are out of alignment as
shown in FIG. 4, then the six triangular shoulders of the bearing face 42
bear on the six flats of the hexagon of the bearing face 44, and prevent
the hollow abutment member 36 from sliding in the sleeve 32 of the housing
30. If the sleeve 32 is moved through 30 degrees, then the two hexagons
are brought into alignment and the hollow abutment member can pass down
the sleeve to the position shown in FIG. 5.
To effect the angular rotation of the sleeve 32, there is provided a cable
linkage 45 connected to an outer lug 46 of the sleeve 32 and passing out
through a guide 47 in the wall of the housing 30. When the cable 45 is
pulled, the sleeve 32 rotates. The hollow abutment member 36 is held
against rotation be cooperation between its hexagonal portion 41 and a
cooperating hexagonal opening in the housing (shown at the right hand end
of the housing in FIGS. 4 and 5). In FIG. 5, the outer lug is shown,
having come into view due to the pulling of the cable 45.
A return spring 51 (FIG. 6) is provided for biasing the sleeve 32 back to
the position shown in FIG. 4. In that position, stop members 48 and 49 on
the sleeve 32 and housing end plate 34 respectively define the limit of
rotation with a 30 degree offset between the hexagonal form of the hollow
abutment member 36 and the hexagonal hole in the abutment face 33.
The actuator or means 52 for moving the sleeve 32 out of engagement with
the shoulder of the abutment member 36 may be the lever or cable actuating
mechanism (shown in FIGS. 4 to 6) or a two-way electric motor actuating
mechanism (shown in FIG. 7). If the cable actuating mechanism is used,
then it should act against the bias of the return spring 51 so that after
the jammed or faulty cable tensioning mechanism has been repaired, the
override release mechanism automatically resets as soon as the abutment
member 36 is moved past the sleeve 32 into a fully-brake-released
condition.
If the mechanism of FIGS. 1 and 2 seizes with the vehicle brakes locked in
their fully braked condition, then the override mechanism of FIGS. 3 to 5
may be deployed. The cable 45 is pulled, preferably using a lever 50 which
adds a considerable mechanical advantage to the tension applied to the
cable 45. The lever 50 should be within reach of the driver of the vehicle
so that if the vehicle is on a slope it can be controlled using the
driving brake pedal. Tensioning of the cable 45 causes the rotation of the
sleeve 32 through 30 degrees until the hexagonal portion of the hollow
abutment member 36 slides through the hexagonal hole in the reaction face
33. The abutment member 36 then moves in the direction of the tensioning
drive nut 5 of the cable brake mechanism, and with the reaction force in
the outer conduit relieved, the tension in the brake cable 7 is reduced,
releasing the vehicle brakes. Preferably actuation of the override brake
release mechanism causes a visual and/or aural warning to be generated in
the driver's cabin, advising that at that stage the vehicle is without a
parking brake facility and should be driven or towed immediately to a
repairer.
After the repair, when the seized brake actuation mechanism has been freed,
it is necessary simply to cause the 24 to run the tensioning drive nut
completely down the lead screw in the direction of brake release.
Preferably the nut 5 contacts the end of the hollow abutment member 36 and
pushes it back to the axial position shown in FIG. 4, when the spring bias
member 51 rotates the sleeve 32 back to the position shown in FIG. 4 when
the stop members 48 and 49 again contact one another.
From the foregoing disclosure and detailed description of certain preferred
embodiments, it is also apparent that various modifications, additions and
other alternative embodiments are possible without departing from the true
scope and spirit of the present invention. The embodiments discussed were
chosen and described to provide the best illustration of the principles of
the present invention and its practical application to thereby enable one
of ordinary skill in the art to utilize the invention in various
embodiments and with various modifications as are suited to the particular
use contemplated. All such modifications and variations are within the
scope of the present invention as determined by the appended claims when
interpreted in accordance with the benefit to which they are fairly,
legally, and equitably entitled.
*
