AU2007234396B2

AU2007234396B2 - Harness pretensioning device for child safety seat

Info

Publication number: AU2007234396B2
Application number: AU2007234396A
Authority: AU
Inventors: Said Nakhla
Original assignee: Britax Child Safety Inc
Current assignee: Britax Child Safety Inc
Priority date: 2006-04-04
Filing date: 2007-04-04
Publication date: 2010-12-16
Anticipated expiration: 2027-04-04
Also published as: AU2007234396A1; US20070228787A1; CA2647218A1; WO2007115303A3; WO2007115303A2

Description

WO 2007/115303 PCT/US2007/065961 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 I of 10 restrain the seat occupant. 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 5 proper tension but, in fact, are too loose to offer the necessary protection. 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, 10 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 Therefore, it is an object of the invention to provide a pretensioning device and related 15 apparatus for a child safety seat. Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. It is another object to provide a child safety seat that has a pretensioning device that 20 applies tension to the harness straps in the event of a crash. 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. According to a first aspect of the present invention, there is provided a child safety device 25 for a vehicle, comprising: (a) a seat and at least one strap for securing an occupant in the seat; (b) a sensor for providing an indication of a predetermined load; and (c) a take up assembly adjacent to the strap and biased to take up a portion of the strap, wherein the take up assembly is releasably linked to the sensor against the 30 bias, and wherein the take up assembly releases from the link to the sensor in response to the indication from the sensor. In one form, the take up assembly is located under the seat. In one form, the take up assembly includes a spring loaded pivot bar. 2 In one form, the pivot bar is configured with a spring bias to rotate to take up a portion of the strap. In one form, the device includes a ratchet mechanism for preventing the take up assembly from linking to the sensor once released from the link to the sensor. 5 In one form, the at least one strap includes an adjuster strap. In one form, the take up assembly takes up the adjuster strap. In one form, the sensor includes a spring. In one form, the at least one strap comprises a harness. In one form, the predetermined load corresponds to a vehicle crash. 10 In one form, the take up assembly removes slack in the strap when taking up a portion of the strap. In one form, the pivot bar carries a portion of the strap with it when it rotates. In one form, the pivot bar folds a portion of the strap when it rotates to increase tension in the strap. 15 In one form, the device further comprises a linking member having an engaged position when attached to the take up assembly and a disengaged position when unattached to the take up assembly, wherein the linking member is connected to the sensor and configured to move from the engaged position to the disengaged position when the sensor provides indication of the predetermined load. 20 In one form, the device further comprises an electrical means for releasing the take up assembly from the link to the sensor in response to indication from the sensor. In one form, the device further comprises a pyrotechnic means for releasing the take up assembly from the link to the sensor in response to indication from the sensor. 25 BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention may be best understood by reference to the following description in conjunction with the accompanying drawing figures in 3 WO 2007/115303 PCT/US2007/065961 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 assembly; [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 BA is an enlarged side view of the take up assembly of the alternative embodiment. 4 of 10 WO 2007/115303 PCT/US2007/065961 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. [0031] 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 5 of 10 WO 2007/115303 PCT/US2007/065961 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 6 of 10 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. 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 5 preferred embodiment of the invention, the pretensioning device is a "one time" use device, meaning that the child safety seat 10 should be discarded and replaced if a crash of sufficient severity has occurred to cause activation of the pretensioning device. 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 10 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. It will be understood that the term "comprise" and any of its derivatives (eg comprises, 15 comprising) as used in this specification is to be taken to be inclusive of features to which it refers, and is not meant to exclude the presence of any additional features unless otherwise stated or implied. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general 20 knowledge. It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that various modifications can be made without departing from the 25 principles of the invention. Therefore, the invention should be understood to include all such modifications in its scope. 7

Claims

1. A child safety device for a vehicle, comprising: (a) a seat and at least one strap for securing an occupant in the seat; 5 (b) a sensor for providing an indication of a predetermined load; and (c) a take up assembly adjacent to the strap and biased to take up a portion of the strap, wherein the take up assembly is releasably linked to the sensor against the bias, and wherein the take up assembly releases from the link to the sensor in response to the indication from the sensor. 10

2. The child safety device according to claim 1, wherein the take up assembly is located under the seat.

3. The child safety device according to either of the preceding claims, wherein the take up 15 assembly comprises a pivot bar.

4. The child safety device according to claim 3, wherein the pivot bar is configured with a spring bias to rotate to take up a portion of the strap. 20 5. The child safety device according to any one of the preceding claims, further comprising a ratchet mechanism for preventing the take up assembly from linking to the sensor once released from the link to the sensor.

6. The child safety device according to any one of the preceding claims, wherein the at least 25 one strap comprises an adjuster strap.

7. The child safety device according to claim 6, wherein the take up assembly takes up the adjuster strap. 30 8. The child safety device according to any one of the preceding claims, wherein the sensor comprises a spring.

9. The child safety device according to any one of the preceding claims, wherein the at least one strap comprises a harness. 8

10. The child safety device according to any one of the preceding claims, wherein the predetermined load corresponds to a vehicle crash. 1H. The child safety device according to any one of the preceding claims, wherein the take up 5 assembly removes slack in the strap when taking up a portion of the strap.

12. The child safety device according to claim 4, wherein the pivot bar carries a portion of the strap with it when it rotates. 10 13. The child safety device according to claim 4, wherein the pivot bar folds a portion of the strap when it rotates to increase tension in the strap.

14. The child safety device according to any one of the preceding claims further comprising a linking member having an engaged position when attached to the take up assembly and a 15 disengaged position when unattached to the take up assembly, wherein the linking member is connected to the sensor and configured to move from the engaged position to the disengaged position when the sensor provides indication of the predetermined load.

15. The child safety device according to any one of the preceding claims further comprising 20 an electrical means for releasing the take up assembly from the link to the sensor in response to indication from the sensor.

16. The child safety device according to any one of the preceding claims further comprising a pyrotechnic means for releasing the take up assembly from the link to the sensor in response to 25 indication from the sensor.

17. A child safety device substantially as herein described with reference to the accompanying drawings. 30 9