Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HARNESS PRETENSIONING
DEVICE FOR CHILD SAFETY SEAT
TECHNICAL FIELD AND BACKGROUND OF THE INVENTION
[0001] This invention relates to a harness pretensioning device and related
apparatus for a child safety seat. Child safety seats have a harness that
includes a
pair of shoulder straps that extend from the back rest of the seat across the
shoulders of the seat occupant, and a crotch strap that extends upwardly from
the
seat bottom to a point between the legs of the seat occupant. The shoulder
straps
extend downwardly and have respective latch members that interconnect with a
latch affixed to the crotch strap that extends upwardly through a slot from
below the
seating surface. In many seat designs the shoulder straps pass through slots
in the
latch and attach to the seat at the waist level to form a pair of straps that
extends
around the waist of the seat occupant to form a lap belt.
[0002] A tensioning strap extends through an opening in the front of the
seating surface. When the shoulder straps are latched into the latch, the
tensioning
strap is pulled to place the shoulder straps in tension so that they fit
securely against
the anterior aspect of the upper torso of the seat occupant. Any significant
slack in
the harness can increase the risk of injury by subjecting the seat occupant to
an
initial rapid, unrestrained acceleration before the shoulder straps are
tensioned by
the forward movement of the seat occupant and bring the seat occupant to an
almost instantaneous stop. It is the g-loading on the seat occupant that
results from
the sudden acceleration and then instantaneous stopping that has the potential
for
injury. This is due to the fact that in the event of an impact, such as from
an
automobile collision, the harness must be placed under tension before it can
act to
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restrain the seat occupant.
[0003] Users require instruction to properly position and restrain the seat
occupant. Lack of attention or training may result in the harness straps being
too
loose. This is particularly so when the seat occupant is wearing bulky or
several
layers of clothing, whereby the straps seem under proper tension but, in fact,
are too
loose to offer the necessary protection.
[0004] There is a need for a device that is adapted to pretension the harness
in the event of a crash so that the seat occupant has the proper level of
protection.
While it is preferable, of course, that the harness be correctly tensioned
from the
outset, a self-acting pretensioning device is desirable to place the harness
in proper
tension at an early stage of an incipient crash. In addition, the
pretensioning device
can be made to self-destruct in the event it is used, thus providing a load-
limiting
feature to the seat.
SUMMARY OF THE DISCLOSURE
[0005] Therefore, it is an object of the invention to provide a pretensioning
device and related apparatus for a child safety seat.
[0006] It is another object to provide a child safety seat that has a
pretensioning device that applies tension to the harness straps in the event
of a
crash.
[0007] It is another object to provide a child safety seat that has a
pretensioning device that self-destructs to provide an indication that the
seat has
been damaged as the result of a crash and should not be further used.
[0008] These and other objects of the present invention are achieved in the
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preferred embodiments disclosed below by providing a child safety device for a
vehicle including a seat and a harness including webbing for securing an
occupant in
the seat, a sensor for providing an indication of a vehicle crash, and a take
up
assembly linked to sensor and the webbing to take up the webbing in response
to
the indication from the sensor.
[0009] In another preferred embodiment of the invention, the take up
assembly is located under the seat.
[0010] In another preferred embodiment of the invention, the take up
assembly includes a spring loaded pivot bar.
[0011] In another preferred embodiment of the invention, the pivot bar rotates
to take up the webbing.
[0012] In another preferred embodiment of the invention, the device includes
a ratchet mechanism for preventing the pivot bar from returning to an original
position.
[0013] In another preferred embodiment of the invention, the webbing
includes an adjuster strap.
[0014] In another preferred embodiment of the invention, the take up device
takes up the adjuster strap.
[0015] In another preferred embodiment of the invention, the sensor includes
a spring.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Embodiments of the invention may be best understood by reference to
the following description in conjunction with the accompanying drawing figures
in
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which:
[0017] Figure 1 is a front perspective view of a child safety seat;
[0018] Figure 2 is a side view of the child safety seat;
[0019] Figure 2A is an enlarged side view of a take up assembly for the child
safety seat;
[0020] Figure 3 is a side view of the child safety seat showing operation of
the
take up assembly;
[0021] Figure 3A is an enlarged side view showing operation of the take up
assembiy;
[0022] Figure 4 is also a side view of the child safety seat showing operation
of the take up assembly;
[0023] Figure 4A is an enlarged side view of the operation of the take up
assembly;
[0024] Figure 5 is another side view of the child safety seat showing
operation
of the take up assembly;
[0025] Figure 5A is another enlarged view showing operation of the take up
assembly;
[0026] Figure 6 is another front perspective view of the child safety seat;
[0027] Figure 7 is a front perspective view of an alternative embodiment of
the
seat;
[0028] Figure 8 is a side view of the alternative embodiment of the child
safety
seat; and
[0029] Figure 8A is an enlarged side view of the take up assembly of the
alternative embodiment.
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DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0030] In an embodiment of the invention shown in Figures 1-6, a child safety
seat 10 is provided with a sensor 14 positioned on the seat 10 and adapted to
be
loaded first in the event of a crash. For example, a spring, plunger,
crushable
member or other initiator is positioned, for example, in the columns of the
seat 10 in
a position to be initially loaded in the event of a crash. An incipient crash
compresses the spring, depresses the plunger or crushes the crushable member
to
provide actuation to the pretensioning device. This action initiates a link 24
to a
take-up assembly 26 interconnected with the harness 36 of webbing. The take-up
assembly 26 releases, taking up slack in the harness 36 with sufficient speed
that
the seat occupant is restrained before significant, possibly injurious,
unrestrained
acceleration commences. It is believed that approximately 12 milliseconds is
available during which to take up slack in the harness 36 before acceleration
of the
seat occupant commences.
[00311 Preferred embodiments of the pretensioning device include either a
mechanical, electrical or pyrotechnic interface between the sensor 14 and the
take-
up assembly 26. For example, the sensor 14 can trigger an actuator spring or
shear
pin designed to operate at a predetermined load, such as 100 lbs.
Alternatively, an
electrical circuit can be used to initiate the take-up assembly 26, the
circuit closing
and sending a signal to the take-up assembly 26 in response to a load of a
predetermined amount on the sensor 14.
[0032] Figures 7, 8 and 8A show an alternative embodiment of the seat
including, schematically, the sensor 14 in the form of a spring linked to the
pivot bar
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40. Further alternatives include the use of a piezoresistive element such as a
strain
gauge and a resistive element, or a piezocapacitive element using a
piezoquartz and
a capacitor. Using these principles will a result in an electrical signal
generation
proportional to the load applied. The circuit is thus designed to operate only
upon
the generation of a predetermined minimum strength current based on an applied
load indicative of a crash of sufficient severity to warrant activation of the
take-up
assembly 26.
[0033] As noted above, the current generated may be used to close an
electrical or electronic circuit. Alternatively, the current may be used to
fire a
pyrotechnic device, i.e., a"squib" or other pyrotechnic that can either
release the
take-up assembly 26 or provide the energy to rotate or displace the take-up
assembly 26. As used herein, the term "squib" refers to a small explosive
device
which can be used for shattering, triggering, propelling and cutting a wide
range of
pyrotechnic and non-pyrotechnic materials. The squib may be used to generate a
pressurized gas to operate a small mechanical actuator such as a release cable
between the sensor 14 and the take-up assembly 26, to shear a shear pin, or
similar
functions.
[0034] The take-up device 26 may be a spring-loaded pivot bar 40 positioned
under the seat 10 that, when activated, releases and rapidly rotates, carrying
with it
a length of the adjuster strap 38 of the harness 36. Figures 2-6, including 2A
-6A,
show, sequentially, operation of pretensioning device, particularly, rotation
of the
pivot bar 40, which increases the effective length of an adjuster strap 38 and
instantly applies additional tension to the harness 36 to which it is
attached. A linear
motion-type device such as a piston and cylinder assembly, spring or gas-
loaded
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plunger or similar device may also be used. As noted above, a pyrotechnic
device
may be used to supply energy to activate the take-up mechanism 26.
[0035] A ratchet mechanism 42 prevents the pivot bar 40 from returning to its
original position. Tension is thus maintained on the harness 36 until the
harness
latch 48 is released. In one preferred embodiment of the invention, the
pretensioning device is a "one time" use device, meaning that the child safety
seat
should be discarded and replaced if a crash of sufficient severity has
occurred to
cause activation of the pretensioning device.
[0036] The pretensioning device may be designed to activate at a given load
only when there is insufficient tension on the harness 36, or at a given load
without
regard to whether the harness 36 is too loose or at a proper tension. In the
latter
event, the take-up device 26 will add only the tension, if any, necessary to
bring the
tension on the harness 36 to the proper level, but will also act as a "one
time" use
device to provide an indication that the child safety seat 10 should not be
further
used, but should be replaced.
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