U.S. patent application number 09/921023 was filed with the patent office on 2002-05-02 for self-locking telescoping device.
Invention is credited to Jones, Gary Lee, Wang, Jenne-Tai.
Application Number | 20020050723 09/921023 |
Document ID | / |
Family ID | 24819997 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020050723 |
Kind Code |
A1 |
Wang, Jenne-Tai ; et
al. |
May 2, 2002 |
SELF-LOCKING TELESCOPING DEVICE
Abstract
A self-locking telescoping device including an outer tube, an
inner tube telescoped into the outer tube having a cone-shaped ramp
at an inboard end, and a plurality of metal spheres between the
ramp and the outer tube. The metal spheres wedge between the ramp
and the outer tube when the inner tube is thrust into the outer
tube in a collapse direction thereby locking the tubes together.
When the thrust is attributable to a severe impact, the spheres
plastically deform the outer tube by plowing tracks therein thereby
to absorb energy. The self-locking telescoping device further
includes an actuator rod, a driver which translates the actuator in
the collapse direction and in an expansion direction, a first
clutch which translates the inner tube with the actuator rod in the
expansion direction, a second clutch which translates the inner
tube with the actuator rod in the collapse direction, and a tubular
retainer on the actuator rod having a plurality of closed-ended
slots around the metal spheres. The closed ends of the slots
prevent the spheres from becoming wedged between the ramp and the
outer tube when the second clutch translates the inner tube with
the actuator rod in the collapse direction.
Inventors: |
Wang, Jenne-Tai; (Troy,
MI) ; Jones, Gary Lee; (Farmington Hills,
MI) |
Correspondence
Address: |
Jeffrey A. Sedlar
General Motors Corporation
Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
24819997 |
Appl. No.: |
09/921023 |
Filed: |
August 2, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09921023 |
Aug 2, 2001 |
|
|
|
09702138 |
Oct 31, 2000 |
|
|
|
Current U.S.
Class: |
293/132 |
Current CPC
Class: |
B60R 19/34 20130101;
Y10T 74/2045 20150115; Y10T 74/20462 20150115; B60R 2021/23123
20130101; B60R 19/40 20130101 |
Class at
Publication: |
293/132 |
International
Class: |
B60R 019/26 |
Claims
1. A self-locking telescoping device comprising: a stationary outer
tube, an inner tube telescoped into the outer tube through a first
end of the outer tube and supported on the outer for translation in
an expansion direction and in a collapse direction, a cone-shaped
ramp on the inner tube at the inboard end thereof facing an inside
cylindrical wall on the outer tube, an annular end wall on the
inner tube at a small diameter end of the cone-shaped ramp, a
plurality of spheres between the cone-shaped ramp and the inside
cylindrical wall on the outer tube cupped against the annular end
wall during translation of the inner tube in the expansion
direction without interfering with translation of the inner tube in
the expansion direction and rolling up the cone-shaped ramp into
wedging engagement between the cone-shaped ramp and the inside
cylindrical wall on the outer tube at the onset of translation of
the inner tube in the collapse direction thereby to render the
self-locking telescoping device structurally rigid in the collapse
direction, an actuator rod telescoped into the outer tube through a
second end of the outer tube and into the inner tube through an
inboard end of the inner tube, a drive means operable to
selectively translate the actuator rod in the expansion direction
and in the collapse direction, a first clutch means operable to
translate the inner tube as a unit with the actuator rod in the
expansion direction, a second clutch means operable to translate
the inner tube as a unit with the actuator rod in the collapse
direction, and a tubular retainer on the actuator rod having a
plurality of slots around respective ones of the plurality of
spheres each having a closed end adjacent to the corresponding one
of the spheres and engageable thereon when the drive means and the
second clutch means translate the actuator rod and the inner tube
in the collapse direction to prevent the corresponding sphere from
rolling up the cone-shaped ramp and becoming wedged between the
cone-shaped ramp and the inside cylindrical wall on the outer
tube.
2. The self-locking telescoping device recited in claim 1 wherein:
each of the plurality of spheres has a hardness sufficient to
plastically deform the outer tube by plowing tracks therein when an
impact on the inner tube in the collapse direction exceeds the
yield strength of the material from which the outer tube is
constructed thereby to convert into work a fraction of the kinetic
energy of the impact.
3. The self-locking telescoping device recited in claim 2 wherein
the first clutch means comprises: a ring rigidly attached to the
actuator rod, and a compression spring between the ring and the
inboard end of the inner tube.
4. The self-locking telescoping device recited in claim 3 wherein
the second clutch means comprises: an annular shoulder on the inner
tube, and an annular flange on the actuator rod facing the annular
shoulder and engageable thereon in response to translation of the
actuator rod in the collapse direction.
5. The self-locking telescoping device recited in claim 4 wherein
the drive means comprises: a rack gear on the actuator rod, a
pinion gear meshing with the rack gear, and a prime mover operable
to rotate the pinion gear in a first direction corresponding to
translation of the actuator rod in the expansion direction and in a
second direction corresponding to translation of the actuator rod
in the collapse direction.
6. The self-locking telescoping device recited in claim 2 further
comprising: a preload means operable to positively thrust each of
the spheres up the cone-shaped ramp into wedging engagement between
the cone-shaped ramp and the inside cylindrical wall on the outer
tube at the onset of translation of the inner tube in the collapse
direction relative to the actuator rod.
7. The self-locking telescoping device recited in claim 6 wherein
the preload means comprises: a retaining ring on the inner tube
constituting the annular end wall on the inner tube at the small
diameter end of the cone-shaped ramp, a thrust washer around the
cone-shaped ramp between the plurality spheres and the retaining
ring, and a spring flexed in compression between the retaining ring
and the thrust washer urging the plurality of spheres up the
cone-shaped ramp into wedging engagement between the cone-shaped
ramp and the inside cylindrical wall on the outer tube at the onset
of translation of the inner tube in the collapse direction relative
to the actuator rod.
8. An energy absorber between a motor vehicle body and a bumper bar
comprising: a stationary outer tube on the motor vehicle body, an
inner tube rigidly attached to the bumper bar and telescoped into
the outer tube through a first end of the outer tube and supported
on the outer for translation in an expansion direction and in a
collapse direction, a cone-shaped ramp on the inner tube at the
inboard end thereof facing an inside cylindrical wall on the outer
tube, an annular end wall on the inner tube at a small diameter end
of the cone-shaped ramp, a plurality of spheres between the
cone-shaped ramp and the inside cylindrical wall on the outer tube
cupped against the annular end wall during translation of the inner
tube in the expansion direction without interfering with
translation of the inner tube in the expansion direction and
rolling up the cone-shaped ramp into wedging engagement between the
cone-shaped ramp and the inside cylindrical wall on the outer tube
at the onset of translation of the inner tube in the collapse
direction induced by an impact on the bumper bar, each of the
plurality of spheres having a hardness sufficient to plastically
deform the outer tube by plowing tracks therein when the impact on
the bumper bar exceeds the yield strength of the material from
which the outer tube is constructed thereby to convert into work a
fraction of the kinetic energy of the impact on the bumper bar, an
actuator rod telescoped into the outer tube through a second end of
the outer tube and into the inner tube through an inboard end of
the inner tube, a drive means on the motor vehicle operable to
selectively translate the actuator rod in the expansion direction
and in the collapse direction, a first clutch means operable to
translate the inner tube as a unit with the actuator rod in the
expansion direction, a second clutch means operable to translate
the inner tube as a unit with the actuator rod in the collapse
direction, and a tubular retainer on the actuator rod having a
plurality of slots around respective ones of the plurality of
spheres each having a closed end adjacent to the corresponding one
of the spheres and engageable thereon when the drive means and the
second clutch means translate the actuator rod and the inner tube
in the collapse direction to prevent the corresponding sphere from
rolling up the cone-shaped ramp and becoming wedged between the
cone-shaped ramp and the inside cylindrical wall on the outer
tube.
9. An energy absorber between a motor vehicle body and a bumper bar
comprising: a stationary outer tube on the motor vehicle body, an
inner tube rigidly attached to the bumper bar and telescoped into
the outer tube through a first end of the outer tube and supported
on the outer for translation in an expansion direction and in a
collapse direction, a cone-shaped ramp on the inner tube at the
inboard end thereof facing an inside cylindrical wall on the outer
tube, an annular end wall on the inner tube at a small diameter end
of the cone-shaped ramp, a plurality of spheres between the
cone-shaped ramp and the inside cylindrical wall on the outer tube
cupped against the annular end wall during translation of the inner
tube in the expansion direction without interfering with
translation of the inner tube in the expansion direction and
rolling up the cone-shaped ramp into wedging engagement between the
cone-shaped ramp and the inside cylindrical wall on the outer tube
at the onset of translation of the inner tube in the collapse
direction induced by an impact on the bumper bar thereby to render
the inner tube and the outer tube rigid relative to each other in
the collapse direction, a plurality of perforations in at least one
of the inner tube and the outer tube defining therebetween a
plurality crush initiators where plastic deformation of the
corresponding one of the inner and outer tubes is initiated after
the steel spheres render the inner and the outer tubes rigid
relative to each other in the collapse direction thereby to convert
into work a fraction of the kinetic energy of the impact on the
bumper bar, an actuator rod telescoped into the outer tube through
a second end of the outer tube and into the inner tube through an
inboard end of the inner tube, a drive means on the motor vehicle
operable to selectively translate the actuator rod in the expansion
direction and in the collapse direction, a first clutch means
operable to translate the inner tube as a unit with the actuator
rod in the expansion direction, a second clutch means operable to
translate the inner tube as a unit with the actuator rod in the
collapse direction, and a tubular retainer on the actuator rod
having a plurality of slots around respective ones of the plurality
of spheres each having a closed end adjacent to the corresponding
one of the spheres and engageable thereon when the drive means and
the second clutch means translate the actuator rod and the inner
tube in the collapse direction to prevent the corresponding sphere
from rolling up the cone-shaped ramp and becoming wedged between
the cone-shaped ramp and the inside cylindrical wall on the outer
tube.
10. The energy absorber recited in claim 8 or claim 9 wherein the
first clutch means comprises: a ring rigidly attached to the
actuator rod, and a compression spring between the ring and the
inboard end of the innertube.
11. The energy absorber recited in claim 10 wherein the second
clutch means comprises: an annular shoulder on the inner tube, and
an annular flange on the actuator rod facing the annular shoulder
and engageable thereon in response to translation of the actuator
rod in the collapse direction.
12. The energy absorber recited in claim 11 wherein the drive means
comprises: a rack gear on the actuator rod, a pinion gear meshing
with the rack gear, and a prime mover on the motor vehicle operable
to rotate the pinion gear in a first direction corresponding to
translation of the actuator rod in the expansion direction and in a
second direction corresponding to translation of the actuator rod
in the collapse direction.
13. The energy absorber recited in claim 12 further comprising: a
preload means operable to positively thrust each of the spheres up
the cone-shaped ramp into wedging engagement between the
cone-shaped ramp and the inside cylindrical wall on the outer tube
at the onset of translation of the inner tube in the collapse
direction relative to the actuator rod.
14. The energy absorber recited in claim 13 wherein the preload
means comprises: a retaining ring on the inner tube constituting
the annular end wall on the inner tube at the small diameter end of
the cone-shaped ramp, a thrust washer around the cone-shaped ramp
between the plurality spheres and the retaining ring, and a spring
flexed in compression between the retaining ring and the thrust
washer urging the plurality of spheres up the cone-shaped ramp into
wedging engagement between the cone-shaped ramp and the inside
cylindrical wall on the outer tube at the onset of translation of
the inner tube in the collapse direction relative to the actuator
rod.
Description
TECHNICAL FIELD
[0001] This invention relates to a self-locking telescoping device
capable of functioning under impact as an energy absorber.
BACKGROUND OF THE INVENTION
[0002] A motor vehicle typically includes a bumper bar and an
energy absorber which supports the bumper bar on a body of the
motor vehicle for translation though a relatively short
energy-absorbing stroke in response to a low speed impact on the
bumper bar. During the energy-absorbing stroke, a fraction of the
kinetic energy of the impact is converted by the energy absorber
into work. In a high speed impact on the bumper bar, however, its
short energy-absorbing stroke is quickly traversed and most of the
kinetic energy of the impact is converted into work by plastic
deformation of body structure of the motor vehicle behind the
bumper bar. As motor vehicles have become more compact, the
energy-absorbing capability of their body structures has decreased
due to the smaller span between the vehicle's passenger compartment
and bumper bar. A telescoping device described in U.S. Pat. No.
5,370,429 supports a bumper bar close to a body of a motor vehicle
except when sensors on the vehicle detect an impending impact.
Then, the telescoping device extends the bumper bar out from the
body to maximize the energy-absorbing stroke of the bumper bar.
During the energy-absorbing stroke, hydraulic fluid is throttled
through an orifice of the telescoping device to absorb a fraction
of the kinetic energy of the impact. The telescoping device
described in the aforesaid U.S. Pat. No. 5,370,429 is not
"self-locking", i.e., does not become structurally rigid in
compression under any circumstances, and requires a fluid reservoir
and fluid seals which may leak during the service life of the
device. Accordingly, manufacturers continue to seek improved
telescoping devices which are self-locking and which are also
suitable for use as bumper energy absorbers.
SUMMARY OF THE INVENTION
[0003] This invention is a new and improved self-locking
telescoping device including a stationary outer tube, an inner tube
telescoped into the outer tube having a cone-shaped ramp at an
inboard end thereof, and a plurality of metal spheres between the
cone-shaped ramp and the outer tube. The metal spheres become
wedged between the cone-shaped ramp and the outer tube when the
inner tube is thrust into the outer tube in a collapse direction
corresponding to a decrease in the length of the telescoping device
thereby locking the inner and outer tubes together and rendering
the telescoping device structurally rigid in the collapse
direction. When the thrust is attributable to a severe impact on
the inner tube, the spheres plastically deform the outer tube by
plowing tracks therein thereby to convert into work a fraction of
the kinetic energy of the impact. The self-locking telescoping
device further includes an actuator rod, a driver which translates
the actuator in the collapse direction and in an opposite expansion
direction corresponding to an increase in the length of the
telescoping device, a first clutch which translates the inner tube
as a unit with the actuator rod in the expansion direction, a
second clutch which translates the inner tube as a unit with the
actuator rod in the collapse direction, and a tubular retainer on
the actuator rod having a plurality of closed-ended slots around
respective ones of the metal spheres. The ends of the slots prevent
the spheres from becoming wedged between the cone-shaped ramp and
the outer tube when the second clutch translates the inner tube as
a unit with the actuator rod in the collapse direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a partially broken-away perspective view of a
self-locking telescoping device according to this invention;
[0005] FIG. 2 is a longitudinal sectional view of the self-locking
telescoping device according to this invention;
[0006] FIG. 3 is similar to FIG. 2 showing structural elements of
the self-locking telescoping device according to this invention in
different relative positions;
[0007] FIG. 4 is a perspective view of the self-locking telescoping
device according to this invention in a motor vehicle bumper energy
absorber application;
[0008] FIG. 5 is a graphic representation of an algorithm
controlling the self-locking telescoping device according to this
invention in the motor vehicle bumper energy absorber
application;
[0009] FIG. 6 is a longitudinal sectional view of a modified
embodiment of the self-locking telescoping device according to this
invention;
[0010] FIG. 7 is similar to FIG. 6 showing structural elements of
the modified self-locking telescoping device according to this
invention in different relative positions;
[0011] FIG. 8 is an enlarged view of the portion of FIG. 6
identified by the reference circle 8 in FIG. 6; and
[0012] FIG. 9 is a fragmentary perspective view of another modified
embodiment of the self-locking telescoping device according to this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] Referring to FIGS. 1-3, a self-locking telescoping device 10
according to this invention includes a stationary outer tube 12
having an inside cylindrical wall 14 and an inner tube 16
telescoped into the outer tube through an end 18 of the latter. An
end fitting 20 rigidly attached to the inner tube constitutes an
inboard end thereof in the outer tube and includes an outside
cylindrical wall 22 bearing against and cooperating with the inside
cylindrical wall 14 of the outer tube in supporting the inner tube
on the outer tube for translation in an expansion direction "E"
corresponding to an increase in the length of the device 10 and in
a opposite collapse direction "C" corresponding to a decrease in
the length of the device each parallel to a longitudinal centerline
24 of the outer tube.
[0014] An annular groove 26 in the outside cylindrical wall 22 of
the end fitting 20 includes a bottom 28, a small diameter end 30,
and a big diameter end 32. The bottom 28 of the groove annular
flares outward, i.e., toward the inside cylindrical wall 14, from
the small diameter end 30 to the big diameter end 32 and
constitutes a cone-shaped ramp 34 on the inner tube at the inboard
end thereof. A plurality of hard steel spheres 36 are disposed in
the annular groove 26.
[0015] During translation of the inner tube 16 in the expansion
direction "E", the spheres 36 are cupped in the annular groove 26
against the small diameter end 30 thereof, FIG. 2, where they slide
along the inside cylindrical wall 14 of the outer tube without
obstructing translation of the inner tube. Conversely, at the onset
of translation of the inner tube in the collapse direction "C", the
spheres roll up the cone-shaped ramp 34 and quickly become wedged
between the cone-shaped ramp and the inside cylindrical wall 14 of
the outer tube thereby effectively locking the inner and the outer
tubes together and rendering the self-locking telescoping device
structurally rigid in the collapse direction "C".
[0016] When the thrust on the inner tube in the collapse direction
"C" is attributable to an extreme impact on the inner tube, the
telescoping device 10 functions as an energy absorber. That is,
with the steel spheres 36 wedged between the cone-shaped ramp and
the inside cylindrical wall of the outer tube, and the self-locking
telescoping device therefore structurally rigid in the collapse
direction "C", the steel spheres plastically deform the outer tube
12 by rolling tracks therein when the thrust attributable to the
extreme impact exceeds the yield strength of the material from
which the outer tube 12 is constructed. Such plastic deformation
absorbs energy by converting into work a fraction of the kinetic
energy of the impact.
[0017] In a modified self-locking telescoping device 37 according
to this invention, FIG. 9, the inner and outer tubes 16,12 are
interrupted by a plurality of perforations 39. The interstices
between the perforations 39 constitute crush initiators. With the
steel spheres 36 wedged between the cone-shaped ramp and the inside
cylindrical wall of the outer tube, and the self-locking
telescoping device therefore structurally rigid in the collapse
direction "C", the outer tube plastically deforms at the crush
initiators when the thrust attributable to the extreme impact
exceeds the yield strength of the material from which the outer
tube 12 is constructed. Such plastic deformation absorbs energy by
converting into work a fraction of the kinetic energy of the
impact.
[0018] The self-locking telescoping device 10 further includes an
actuator rod 38 telescoped into a second end 40 of the outer tube
12 and into a bore 42 in the end fitting 20 on the inner tube. The
actuator rod has a rack gear 44 thereon which meshes with a pinion
gear 46. The pinion gear 46 is connected by a pinion shaft 48 to a
prime mover in the form of an electric motor 50 so that the motor,
the pinion gear, and the rack gear constitute a drive means
operable to translate the actuator rod back and forth in the
expansion and collapse directions "E", "C" of the inner tube.
[0019] A tubular hub 52 is rigidly attached to the actuator rod 38
and supports the actuator rod in the bore 42 in the end fitting 20
for translation relative to the inner tube in the direction of the
longitudinal centerline 24 of the outer tube. A ring 54 is rigidly
attached to the hub 52 at the end thereof facing the rack gear 44
on the actuator rod and cooperates with the inside cylindrical wall
14 of the outer tube in supporting the actuator rod on the outer
tube for back and forth translation in the expansion and collapse
directions "E", "C" of the inner tube. An annular flange 56 on the
end of the hub 52 opposite the ring 54 faces an annular shoulder
58, FIG. 3, on the end fitting 20 around the bore 42. A compression
spring 60 seats against the ring 54 and against the end fitting 20
and biases the end fitting and the actuator rod in opposite
directions until the annular flange 56 seats against the annular
shoulder 58.
[0020] A tubular retainer 62 of the telescoping device 10 surrounds
the compression spring 60 and overlaps the gap between the end
fitting 20 and the ring 54. The retainer includes a hooked end 64,
FIG. 2, seated in a corresponding annular groove in the ring 54
whereby the retainer is rigidly attached to the ring and,
therefore, to the actuator rod 38. The tubular retainer has a
plurality of slots 66, FIG. 1, parallel to the longitudinal
centerline 24 of the outer tube each of which terminates at a
closed end 68. Each slot receives a corresponding one of the
spheres 36 and has a length calculated to locate its closed end 68
close to the corresponding sphere when the spring 60 thrusts the
annular flange 56 on the hub 52 against the annular shoulder 58 on
the end fitting 20, FIG. 2.
[0021] The ring 54 and the spring 60 constitute a first clutch
which effects unitary translation of the actuator rod and the inner
tube in the expansion direction "E" in response to corresponding
rotation of the pinion gear 46. That is, when the pinion gear
rotates clockwise, FIGS. 2-3, the thrust applied to the actuator
rod is transferred to the end fitting 20 through the ring 54 and
the spring 60 and urges the inner tube in the expansion direction
"E". At the same time, the spheres 36 remain cupped against the
small diameter end 30 of the annular groove 26 where they slide
along the inside cylindrical wall 14 of the outer tube without
interfering with translation of the outer tube. If the actuator rod
translates in the expansion direction "E" relative to the inner
tube because of friction between the inner and outer tubes, the
closed ends 68 of the slots 66 in the retainer 62 separate
harmlessly from the spheres 36 until the thrust on the inner tube
exceeds the friction.
[0022] Conversely, the annular flange 56 on the hub and the annular
shoulder 58 on the end fitting 20 constitute a second clutch which
effects unitary translation of the actuator rod and the inner tube
16 in the collapse direction "C" in response to corresponding
rotation of the pinion gear 46. That is, when the pinion gear
rotates counterclockwise, FIGS. 2-3, the thrust applied to the
actuator rod 38 is transferred directly to the end fitting through
the flange 56 and the annular shoulder 58 and urges the inner tube
in the collapse direction "C". At the same time, the ring 54
translates with the actuator rod in the collapse direction "C" so
that the retainer 62 and the end fitting 20 translate as a unit in
the same direction. In that circumstance, the closed ends 68 of the
slots 66 prevent the spheres 36 from rolling up the cone-shaped
ramp 34 and thus prevent the spheres from becoming wedged between
the end fitting 20 and the outer tube 14 and interfering with
translation of the inner tube in the collapse direction "C".
[0023] Referring to FIGS. 4-5, a pair of the self-locking
telescoping devices 10 are illustrated in a bumper energy absorber
application on a schematically represented motor vehicle 70 having
a frame 72 and a bumper bar 74. The outer tubes 12 are rigidly
attached to the frame 72 on opposite sides of thereof and the inner
tubes 16 are rigidly attached to the bumper bar. An electronic
control module (ECM) 76 on the motor vehicle is connected to each
of the electric motors 50 and to a transducer 78 which provides
electronic signals to the ECM corresponding to the velocity of the
motor vehicle. When the ECM 76 turns on the electric motors to
rotate the pinion gears 46 in the expansion direction "E" of the
inner tubes, the bumper bar 74 is translated by the actuator rods
and the inner tubes from a retracted position to an extended
position, illustrated respectively in solid and broken lines in
FIG. 4, in which the bumper bar protrudes further in front of the
frame 72. When the ECM turns on the electric motors to rotate the
pinion gears in the collapse direction "C" of the inner tubes, the
bumper bar is translated by the actuator rods and the inner tubes
from its extended position back to its retracted position.
[0024] With the electric motors 50 turned off and the bumper bar in
its extended position, a severe impact on the bumper bar 74
initiates translation of the inner tubes 16 of the devices 10 in
the collapse direction "C" relative to the outer tubes and the
actuator rods. The end fittings 20 plunge toward the rings 54
against the resistance of the springs 60 while the closed ends 68
of the slots 66 in the tubular retainers separate from the spheres
36, FIG. 3. The spheres then roll up the cone-shaped ramps 34,
become wedged against the inside cylindrical walls 14 of the outer
tubes, and commence plowing tracks in the outer tubes to convert
into work a fraction of the kinetic energy of the impact on the
bumper bar.
[0025] A flow chart 80, FIG. 5, depicts an algorithm according to
which the ECM 76 turns the electric motors 50 on and off including
a start block 82 initiated when the electrical system of the motor
vehicle is turned on with the bumper bar in its retracted position.
From the start block 82, the algorithm monitors the velocity of the
motor vehicle through an electrical signal from the transducer 78
and asks at a decision block 84 whether the velocity of the motor
vehicle is in a high range, e.g., above 15 miles per hour (MPH), in
which a high speed impact is possible. If the answer is no, the ECM
does not turn on the electric motors and the bumper bar remains in
its retracted position. If the answer is yes, the algorithm turns
on the electric motors through the ECM to translate the bumper bar
74 to its extended position more remote from the frame 72 where it
affords increased protection against a high speed impact.
[0026] With the bumper bar in its extended position, the algorithm
monitors the velocity of the motor vehicle through the electrical
signal from the transducer 78 and asks at a decision block 86
whether the velocity of the motor vehicle is in a low range, e.g.,
less than 10 MPH, in which a high speed impact is improbable. If
the answer is no, then the algorithm repeats the interrogation of
vehicle velocity between the decision blocks 84,86. If the answer
is yes, the algorithm interrogates vehicle velocity a second time
after a delay of about three seconds and asks at a decision block
88 whether vehicle velocity is still in the low range. If the
answer is no, then the algorithm repeats the interrogation of
vehicle velocity between the decision blocks 84,86. If the answer
is still yes, the algorithm turns on the electric motors 50 through
the ECM to translate the bumper bar back to its retracted
position.
[0027] Referring to FIGS. 6-8, another modified self-locking
telescoping device 90 according to this invention is identical to
the self-locking telescoping device 10 described above except as
now recited. Structural elements common to the device 10 and the
modified device 90 are identified in FIGS. 6-8 with primed
reference characters. In place of the compression spring 60 in
device 10, the modified device 90 includes a retaining ring 92, an
annular wave spring 94, and a thrust washer 96, FIG. 8, which
constitute a preload means of the modified device. The retaining
ring 92 is supported on the end fitting 20' on the inner tube 16'
and constitutes the small diameter end of the annular groove in the
outside cylindrical surface 22' of the end fitting. The thrust
washer 96 loosely encircles the cone-shaped ramp 34' between the
retaining ring 92 and the spheres 36'. The wave spring encircles
the cone-shaped ramp between the retaining ring 92 and the thrust
washer 96.
[0028] The pinion gear 46' translates the inner tube 16' of the
modified self-locking telescoping device 90 in the collapse
direction "C" through the actuator rod 38', the annular flange 56'
on the hub 52', and the annular shoulder 58' on the end fitting
20'. At the same time, the closed ends 68', FIG. 8, of the slots
66' in the tubular retainer 62' prevent the spheres 36' from
rolling up the cone-shaped ramp 34' and becoming wedged between the
end fitting and the outer tube, FIG. 6, while maintaining the wave
spring flexed in compression between the thrust washer and the
retaining ring. When the pinion gear 46' rotates in the opposite
direction to translate the actuator rod in the expansion direction
"E", the inner tube 16' and the end fitting 20' remain stationary
due to friction until the ring 54' on the actuator rod seats
against the end fitting, FIG. 7. The ring and the end fitting thus
constitute the aforesaid first clutch of the modified device 90
which translates the inner tube as a unit with the actuator rod in
the expansion direction "E".
[0029] When the pinion gear 46' is stationary, thrust on the inner
tube in the collapse direction "C" initiates translation of the end
fitting in the same direction relative to the actuator rod while
the closed ends of the slots in the retainer 62' separate from the
spheres 36'. At the same time, the annular wave spring 94 separates
the retaining ring 92 and the thrust washer 96 to positively and
substantially instantly thrust the spheres 36' up the cone-shaped
ramp 34' into wedging engagement between the end fitting and the
inside cylindrical wall of the outer tube. The spheres 36' thus
render the modified self-locking telescoping device 90 structurally
rigid in the collapse direction "C" unless the thrust is
attributable to a severe impact on the inner tube. Then, the
spheres plastically deform the outer tube by plowing tracks therein
to convert into work a fraction of the kinetic energy of the
impact.
* * * * *