Self-adjusting seat stiffness system and anti-submarining system

Abstract

Self-adjusting seat stiffness system (82), comprising: a tensioning element (30) in cooperation with a tensioning unit (32) which is connected to and spans a part of a vehicle seat (10), wherein the tensioning unit (32) automatically adjusts the tension of the tensioning element (30) in response to a perceived dynamic vehicle event and ensures seat stiffness.

Description

[0001] This disclosure relates to vehicle seats and, more particularly, to a vehicle seat having a self-adjusting seat stiffness system.

[0002] GB 2 357 030 A, EP 1 067 015 A1 and DE 100 65 464 A1 each disclose a vehicle seat with an anti-submarining system.

[0003] Vehicles typically include at least one seat on which an occupant can sit while the vehicle is in use. Vehicle seats may include a base adjustably mounted on a floor of the vehicle and a backrest adjustably attached to the base, but other seat constructions have been used, such as a continuous seat base and backrest construction, or constructions having multiple seat bases and multiple backrests, or the base or backrest of the seat may be provided by a vehicle body, or any combination of the above constructions. Whether as separate components or as a continuous unit, the base and backrest typically include a structural perimeter frame with a suspension system disposed therein.The suspension system is used to support an occupant and ensure seating comfort. Suspension systems typically consist of a combination of box springs, coil springs, or a suspension system made of a wire mesh and foam. Suspension systems typically span between at least one pair of opposing components of the perimeter frame to more easily meet the vehicle occupant's positioning and comfort requirements.

[0004] The base and backrest provide a reaction surface for the mass of the vehicle occupant and support them. The stiffness of the base and backrest suspension systems is a fixed value and depends on the combination of spring / foam stiffness of the suspension system. While some systems may offer the vehicle occupant the option to adjust the seat stiffness for comfort, once the stiffness level is selected, the stiffness remains a fixed value during use.

[0005] Seat belts are commonly used to keep a vehicle occupant in their seat. During vehicle acceleration, the mass and acceleration of the occupant in the seat can cause compression of the seat and / or backrest, increasing the space between the seat belt and the seat, which in turn can cause the vehicle occupant to slide under the seat belt. The term acceleration as used herein includes deceleration. Slipping under a seat belt due to seat compression can be referred to as "submarining." Five- and six-point harnesses help prevent slide-through by providing crotch straps, but most vehicles are not equipped with five- and six-point harnesses because they are perceived as uncomfortable and impractical for everyday use.

[0006] A seat can be equipped with a more pronounced geometry in certain areas or a stiffer base and backrest to better support the vehicle occupant and increase seatbelt retention during acceleration. However, more pronounced geometries and higher stiffness tend to reduce seating comfort, because softer seats actually increase comfort.

[0007] One aspect of this disclosure concerns a self-adjusting seat stiffness system having a tensioning member in cooperation with a tensioning unit connected to and spanning a portion of a seat. The tensioning unit is configured to automatically adjust the tension of the tensioning member, thereby providing seat stiffness in response to a sensed dynamic vehicle event. The tensioning unit may be an inertial locking retractor, an electric retractor, a pyrotechnic retractor, or any number of other devices capable of providing stiffness to the tensioning member.

[0008] A control device may be used to control the tensioning unit. The control device may send a signal to the tensioning unit to maintain the tension in the tensioning element or to increase the tension in the tensioning element. The control device may be connected to a pre-crash system of the vehicle, and the control device may adjust the tension of the tensioning element in response to a potential collision of the vehicle with another object as indicated by the pre-crash system. The control device may be connected to a seat pressure sensor or weight sensor, and the control device may adjust the tension of the tensioning element in response to an increase in seat pressure or weight, particularly in the event of a rapid increase in weight pressure or weight. The control device may also be capable of monitoring vehicle acceleration.The controller may monitor vehicle acceleration by communicating with a vehicle communication system. The sensed dynamic vehicle event may be a triggering acceleration value, and the controller may adjust the tension of the tensioning element in response to the triggering acceleration value.

[0009] The seat may include opposing first and second frame members, and the tension member may span the seat between the first and second frame members. The tension member may be connected to the first frame member, and the tension unit may be connected to the second frame member. The tension member may be oriented transversely with respect to the vehicle, it may extend longitudinally with respect to the vehicle, or it may extend in any suitable direction therebetween. The seat may include a seat suspension system comprised of springs and pads, and the tension member may be disposed within the suspension system or extend over the top of the suspension system.

[0010] The system may also include an inflatable element connected to the tensioning element. The inflatable element may be used in response to a perceived dynamic vehicle event in combination with the maintenance or increase of tension by the tensioning element.

[0011] According to another aspect of this disclosure, an anti-submarining system for a vehicle seat is disclosed. The anti-submarining system includes a tensioning member spanning a portion of a vehicle seat between opposing frame members and a control device for tensioning the tensioning member for increased stiffness of the seat portion in response to a sensed dynamic vehicle event.

[0012] With this system, the perceived dynamic vehicle event can be a vehicle acceleration beyond a target acceleration or a potential collision of the vehicle with another object. A tensioning unit can be an inertial locking retractor, an electric retractor, or a pyrotechnic retractor. An inflatable element can be connected to the tensioning element, and the inflatable element can also be deployable in response to the tension of the tensioning element.

[0013] The above aspects of this disclosure and other aspects are explained in more detail below with reference to the accompanying drawings. Fig. 1 is a perspective view of a seat frame having tensioning elements extending substantially in a vehicle transverse direction when the seat is installed in the vehicle. Fig. 2 is a perspective view of a seat frame with tensioning elements extending in a vehicle transverse direction and returning thereto at an acute angle. Fig. 3 is a perspective view of a seat frame with tensioning elements extending substantially in a vehicle longitudinal direction. Fig. 4 is a partial view of a seat with a tensioning unit arranged on the inside of opposite frame members and with a tensioning element guided through a frame member. Fig. 5 is a partial view of a seat with a tensioning unit arranged on the inside of opposing frame members and with a tensioning element guided by a retaining bracket attached to a frame member. Fig. 6 is a partial view of a seat with a tensioning unit arranged on the outside of opposing frame members. Fig. 7 is a partial view of a seat with an inflating element connected to a tensioning element. Fig. 8 is a perspective view of a vehicle seat with a tensioning element arranged outside a seat base. Fig. Figure 9 is a diagrammatic view of a self-adjusting seat stiffness system.

[0014] The illustrated embodiments are disclosed with reference to the drawings. It should be understood, however, that the disclosed embodiments are merely exemplary and may be embodied in various and alternative forms. The illustrations are not necessarily to scale; some features may be exaggerated or reduced to show details of particular components. The specific structural and functional details disclosed are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the disclosed concepts.

[0015] Fig. 1 shows a vehicle seat 10 without any filling material or padding. When filled and padded, the seat 10 includes a base 12 and a backrest 14 that can support a vehicle occupant (not shown) while riding in a vehicle. The seat 10 also includes a frame 16 that provides structural support for the components of the seat 10. The frame 16 may include side frame members 18, 20, a front frame member 22, and a rear frame member 24 that cooperate to frame the base 12. The side frame members 18, 20 may provide opposing first and second frame members 18, 20. The front and rear frame members 22, 24 may also provide opposing first and second frame members 22, 24.

[0016] The seat 10 is shown with a spring-type seat suspension system 26, but other suspension mechanisms may be used. A cushion or foam pad may be placed on or integrated with the seat suspension system 26 before the seat 10 is upholstered. The seat suspension system 26 is designed to provide a comfortable feeling to a vehicle occupant in the seat.

[0017] A tension member 30 is shown spanning the seat 10 between first and second frame members 18, 20. The tension member 30 may be connected to the first frame member 18. The tension member 30 may be oriented to extend substantially transversely with respect to a vehicle when the seat 10 is installed in the vehicle. The term "substantially transverse" as used herein means that the tension members 30 need not extend at perfect 90-degree angles to the longitudinal axis of the vehicle, but rather that the tension members 30 have more of a transverse vehicle dimension than a longitudinal vehicle dimension.

[0018] The center tensioner 30 shown is interwoven with the seat suspension system 26, but the tensioners 30 may be positioned above, as shown with the front tensioner 30, or below the seat suspension system 26, as shown with the rear tensioner 30, or even used as a replacement for the seat suspension system 26 altogether. The tensioner 30 may be made of a material similar to the seat belt webbing, but it is not limited to that material or shape.

[0019] A tensioning unit 32 may be connected to the second frame member 20 and, in cooperation with the tensioning element 30, may span a portion of the seat 10. The tensioning unit 32 may cooperate with the tensioning element 30 to automatically adjust the tension of the tensioning element 30 and provide seat stiffness in response to a sensed dynamic vehicle event. The tensioning unit 32 may be a thinly packed, inertially locked take-up spool assembly tuned to specific vehicle pulse targets to trigger the tensioning element 30 upon the correct vehicle inputs. The tensioning unit 32 may also be an inertial lock with a solenoid, a motorized coil, a pyrotechnic system, or any number of devices that may be used to maintain the tensioning element 30 at an initial stiffness or even to increase stiffness at the time of deployment.

[0020] The take-up spool assembly can allow the tension of the tensioning element 30 to ebb and flow during vehicle use outside of the sensed dynamic vehicle event, and maintain the initial tension or increase the tension of the tensioning element 30 during the sensed dynamic vehicle event. The take-up spool can include a spring (not shown) that can allow a lower set tension level of the tensioning element 30 during normal vehicle use, and the tensioning unit 32 can then stop further extension of the tensioning element 30 or retract the tensioning element 30 into the spool to maintain or increase the tension level during a sensed dynamic vehicle event. The take-up spool can include an inertial lock that can lock the spool when the acceleration and / or velocity of the spool is greater than a set amount.In other words, if the tensioning element 30 is pulled too quickly from the tensioning unit 32, the inertia lock will lock and prevent movement of the tensioning element 30 with the seat suspension system 26.

[0021] During normal vehicle use, the vehicle occupant experiences a series of accelerations in the longitudinal, lateral, and vertical vehicle directions while seated in the vehicle seat 10, and the seat suspension system 26 provides cushioning for the accelerations of the vehicle occupant's body. The seat suspension system 26 supports and cushions the vehicle occupant. The tensioning member 30 and the tensioning unit 32 cooperate to allow the seat suspension system 26 to support the vehicle occupant and to compress and rebound beneath the vehicle occupant to provide a cushioned ride without noticeable disturbance. The tensioning member 30 and the tensioning unit 32 may even be configured to provide the seat suspension system 26, or a portion of the seat suspension system 26, during normal vehicle use.

[0022] Compression of the seat suspension system 26 by the mass of the vehicle occupant against the seat 10 during vehicle acceleration may cause an increased gap between the seat 10 and a seat belt (not shown). As mentioned above, the term acceleration also encompasses deceleration. An increased gap between the seat 10 and the seat belt may alter the seat belt's ability to retain the vehicle occupant in the seat 10. Rapid acceleration may further increase the gap between the seat 10 and the seat belt.

[0023] When the tensioning element 30 and the tensioning unit 32 experience a sensed dynamic vehicle event, such as rapid acceleration of the vehicle, the tensioning element 30 and the tensioning unit 32 cooperate to maintain a set tension so that the seat suspension system 26 does not experience further compression by the vehicle occupant against the seat 10. The tensioning element 30 and the tensioning unit 32 cooperate to maintain or increase the tension of the seat 10 and to keep the gap between the seat 10 and the safety belt substantially constant or even close the gap so that the vehicle occupant is better held in the seat 10 by the safety belt. Maintaining the gap between the seat 10 and the safety belt helps prevent a vehicle occupant from slipping under the safety belt.

[0024] The tensioning elements 30 can also be arranged in the seat 10 to provide a ramp or upward step in a longitudinally forward direction. The more forward tensioning units 32 can be attached to the side frame members 18, 20 at vertical locations that are higher than the more rearward tensioning units 32. This configuration allows the tensioning elements 30 to cross the seat and provide a ramp effect, which can further prevent a submarining event.

[0025] Fig. 2 shows a tensioning element 30 extending between a first and a second frame member 18, 20 in an angular cross direction. The tensioning element 30 shown extends at acute angles to the vehicle transverse direction. The tensioning element 30 is connected to the second frame member 20, extends angularly across the seat 10 to the first frame member 18, then loops back over itself and returns to a tensioning unit 32 connected to the second frame member 20. The tensioning element 30 may extend through a pin disposed in an opening defined by the first frame member 18 as shown, or the tensioning element 30 may extend through a retaining bracket extending from the first frame member 18, or through the first frame member 18 itself.The tensioning element 30 can extend under the seat suspension system 26 in one direction and over the seat suspension system 26 in the other direction, in both directions over the seat suspension system 26, in both directions under the seat suspension system 26, or intertwined with the seat suspension system 26 in one of the directions or in both directions, or in any combination of the above.

[0026] Fig. 3 shows a tensioning element 30 extending between a first and a second frame element 22, 24. In this embodiment, the first and second frame elements 22, 24 are the front and rear frame elements 22, 24. The tensioning unit 32 can be attached to either the first or the second frame element 22, 24, with the tensioning element 30 extending therefrom to another frame element. Although the above figures show tensioning elements 30 extending only between the first and second frame elements 18, 20 or 22, 24, tensioning elements 30 can extend simultaneously between first and second elements and third and fourth elements, resulting in an overlap of the tensioning elements 30. The tensioning elements 30 can also extend between two adjacent frame elements, and the tensioning element 30 can also be a mesh of straps or fabrics extending between two or more frame elements.

[0027] Although not specifically shown in this figure, the tensioning units 32 may be attached to the front frame member 22 at a vertical location that is higher than the vertical location of the corresponding tensioning unit 32 for the same tensioning element 30, which is attached to the rear frame member 24. This configuration enables a ramping effect by the tensioning elements 30 when the tensioning units 32 become active to maintain or increase the stiffness of the tensioning elements 30, which may further prevent a submarining event.

[0028] Fig. 4 shows an embodiment in which the clamping unit 32 is arranged on an inner side 36 of a frame element 38. The frame element 38 can be a side frame element 18, 20, a front frame element 22, a rear frame element 24 of a base frame 12, as in Fig. 1, or it may be any other frame member in the frame 12 of the seat 10, including a frame member in the backrest 14. In this embodiment, the frame member 38 defines a through hole 40 and a notch 44 for orienting the tensioning member 30 as it extends from the tensioning unit 32. A frame member 44 opposite the frame member 38 also defines a through hole 46 and a notch 48. The tensioning member 30 extends from the tensioning unit 32 through the through hole 40 and up to and around the notch 42 over to the notch 48 on the opposite frame member 44 and down through the through hole 46 and is anchored to the inside surface 50 of the opposite frame member 44.

[0029] Fig. 5 shows two tensioning elements 30; a first tensioning element 54 and a second tensioning element 56, but any number of tensioning elements 30 may be used. The first tensioning element 54 is shown in an activated state, in which the tensioning unit 32 maintains or increases the tension on the first tensioning element 54, and the second tensioning element 56 is shown in a relaxed state, in which a tensioning unit 32 does not maintain or increase the tension on the second tensioning element 56.

[0030] Fig. 5 shows another embodiment in which a tensioning unit 32 is disposed on an inner side 36 of a frame member 38. In this embodiment, a tensioning element 30 extends upwardly from the tensioning unit 32 through a first guide bracket 58, across the seat, to an opposite frame member 44 through a second guide bracket 60, and is anchored to the opposite frame member 44. Again, a first tensioning element 54 is shown in an activated state in which the tensioning unit 32 maintains or increases tension on the first tensioning element 54, and a second tensioning element 56 is shown in a relaxed state in which a tensioning unit 32 does not maintain or increase tension on the second tensioning element 56.

[0031] Fig. 6 shows another embodiment in which a tensioning unit 32 is disposed on an outer side 62 of a frame member 38. In this embodiment, the frame member 38 and an opposing frame member 44 both define a notch 42, 48, and the tensioning member 30 extends from the tensioning unit 32 to the notches, spans the opposing frame members 38, 44 between the two notches 42, 48, and is anchored to the opposing frame member 44. Again, a first tensioning member 54 is shown in an activated state in which the tensioning unit 32 maintains or increases tension on the first tensioning member 54, and a second tensioning member 56 is shown in a relaxed state in which a tensioning unit 32 does not maintain or increase tension on the second tensioning member 56.

[0032] Fig. 7 shows an inflatable element 66 connected to a tensioning element 30. The inflatable element 66 may be a separate component attached to the tensioning element 30, or it may be integrated into the tensioning element 30. The inflatable element 66 may be deployed in response to a sensed dynamic vehicle event. The inflatable element 66 may be inflated using a pyrotechnic device and an expandable material, similar to an airbag, or it may be pneumatic. The inflatable element 66 may be designed to inflate and deflate during use, making it reusable, or it may be designed for single use only. The inflatable element 66 may also be deployed upon a second sensed dynamic vehicle event that is more intense than a first sensed dynamic vehicle event.For example, the tensioning unit 32 may lock the tensioning element 30 during a vehicle acceleration comparable to a hard braking event, while the inflatable element 66 may only be deployed during a vehicle acceleration that exceeds a hard braking event, such as when the vehicle impacts another object.

[0033] Fig. Figure 8 shows a seat 70 complete with a frame 16 and a seat suspension system 26 (best in Fig. 1), with foam filling and padding 72. In this embodiment, the padding 72 covering the base 12 defines a series of through-holes 74, and the tensioning member passes through the through-holes 74 and extends across the base 12 on the outside of the padding 72. The tensioning member 30 is still anchored to a frame member 38 in the base 12 at one end and extends to a tensioning unit 32 connected to an opposite frame member 44. The tensioning unit 32 may be disposed on the seat 70 so that it is disposed within the padding 72 and not visible to a vehicle occupant, as shown, or it may be connected to the seat 70 within sight of the vehicle occupant. Aftermarket kit for attaching a self-adjusting seat stiffness system to an existing seat may provide such a configuration.

[0034] Fig. 9 shows a vehicle 80 with a self-adjusting seat stiffness system / vehicle seat anti-submarining system 82. The system 82 may include a controller 84 for controlling the tensioning unit 32. The controller 84 may send a signal 86 to the tensioning unit 32 to maintain at least an initial tension in the tensioning element 30 (see Fig. 1). The control device 84 can also send a signal 86 to the tensioning unit 32 to increase the tension in the tensioning element 30.

[0035] The system 82 may also include or be in communication with a vehicle pre-crash system 88, as indicated by the connecting arrow 90. The controller 84 may be in communication with the vehicle pre-crash system 88 to detect a sensed dynamic vehicle event, and in response to the sensed dynamic vehicle event, the controller 84 may send a signal 86 to the tensioning unit 32 to maintain or increase the tension on the tensioning element 30. The sensed dynamic vehicle event may be a potential collision of the vehicle 80 with another object determined by the vehicle pre-crash system 88. The controller 84 may also adjust the tension of the tensioning element 30 to different levels in response to the nature of the potential collision of the vehicle 80 with another object.

[0036] The system 82 may further include or be in communication with a seat pressure sensor 92 disposed in the seat 94, as indicated by the connecting arrow 96. The controller 84 may communicate with the seat pressure sensor 92 to determine the amount of pressure a vehicle occupant (not shown) applies to the seat when in the vehicle 80. During a dynamic vehicle event, the pressure of a vehicle occupant on the seat 94 may change and the compression of the seat suspension system 26 (see Fig. 1) and the cushion may increase the gap between the seat 94 and a seat belt (not shown). The controller 84 may be preprogrammed with a seat pressure / seat compression comparison table and control the tensioning unit 32 to maintain a minimum seat compression. The minimum seat compression may also be scaled depending on vehicle dynamics. In other words, a lower tension of the tensioning element 30 may be set at lower speeds and lower vehicle accelerations, while a higher tension of the tensioning element 30 may be set at higher vehicle speeds and for higher vehicle accelerations. In this embodiment, the perceived dynamic vehicle event is an increase in seat pressure, and the controller 84 may adjust the tension of the tensioning element 30 in response to an increase in seat pressure.

[0037] The system 82 may further include or be in communication with a vehicle communication system 98, as indicated by the connecting arrow 99. An internal vehicle communication system 98 may interconnect electronic systems within the vehicle 80. The vehicle communication system 98 may have specific protocols followed, such as a Controller Area Network (CAN) or a Local Interconnect Network (LIN). Specific vehicle control requirements may be incorporated into the vehicle communication system 98, such as assured message delivery, assured non-conflicting messages, assured delivery time, EMF noise attenuation, and lighting redundant routing.

[0038] In this embodiment, which may be combined with the other embodiments, the controller 84 may access the vehicle communication system 98 and monitor vehicle dynamics, such as acceleration or yaw, available from the vehicle communication system 98. The sensed dynamic vehicle event may be a trigger value of any of a number of monitorable dynamic vehicle parameters, including, but not limited to, an acceleration or yaw value. The controller 84 may adjust the tension of the tensioning element 30 in response to the triggering acceleration value.

[0039] The controller 84 may provide increased stiffness to a portion of the seat 94 in response to a perceived dynamic vehicle event. The increased stiffness may reduce the gap between the seat 94 and a seatbelt, which may increase due to compression of the seat 94 by the vehicle occupant's weight acting on the seat 94 during an event. The perceived dynamic vehicle event may be an actual rapid acceleration of the vehicle or a potential rapid acceleration of the vehicle.

[0040] The control device 84 can also be equipped with an inflatable element 66 (see Fig.7) connected to the tensioning element 30. The control device 84 can also control the deployment of the inflatable element 66. As mentioned above, the inflatable element 66 can be deployed in conjunction with the tensioning of the tensioning element 30, or it can be set to only be deployed at a higher level of perceived vehicle dynamics.

[0041] The tensioning element 30, in cooperation with the tensioning unit 32 and possibly in additional cooperation with a controller 84 of the system 82, can be designed to achieve combinations of the following objectives: Providing enhanced restraint of a vehicle occupant during a dynamic vehicle event. Providing enhanced restraint of a vehicle occupant's pelvis. Providing dynamically adjustable stiffness of the seat base fill and backrest for use during vehicle performance dynamics. Testing a self-adaptive, conforming seat cushion and backrest cushion for comfort at all times. Providing an adjustable seat base and backrest comfort level for the vehicle occupant, whether manually or electronically, that can be tuned to a specific design or by the vehicle occupant. Providing a pre-crash active restraint.Providing a deployable inflatable member 66 that can be inflated to increase its size to create a reaction or obstruction surface to further enhance the restraint of a vehicle occupant during a dynamic vehicle event. Providing a vehicle occupant classification sensor that allows the controller 84 to further adjust the tensions depending on the vehicle occupant's weight. Vehicle occupant classification can also be used when deploying the inflatable member 66. For example, a lighter vehicle occupant may be smaller and more prone to slipping under the seatbelt, so the target for a lighter vehicle occupant can be reduced and the inflatable member can be deployed earlier for such a scenario.Providing a replacement for traditional cushion bolsters and / or seat suspension systems 26 through the use of dynamic support geometries and tensioning systems. Providing a reactive and energy-absorbing restraint surface for a rear impact (i.e., a "backrest protective glove").

[0042] Although exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms of the disclosed apparatus and method. Instead, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the claimed disclosure. The features of various implementing embodiments may be combined to form further embodiments of the disclosed concepts.

Claims

[1] Self-adjusting seat stiffness system (82) comprising: a tensioning element (30) in cooperation with a tensioning unit (32) which is connected to and spans a part of a vehicle seat (10), wherein the tensioning unit (32) automatically adjusts the tension of the tensioning element (30) in response to a perceived dynamic vehicle event and provides seat stiffness. [2] The seat stiffness system (82) of claim 1, wherein the tensioning unit (32) is an inertial locking retractor. [3] The seat stiffness system (82) of claim 1, wherein the tensioning unit (32) is an electric retractor. [4] The seat stiffness system (82) of claim 1, wherein the tensioning unit (32) is a pyrotechnic retractor. [5] Seat stiffness system (82) according to claim 1, further comprising a control device (84) for controlling the comprising a clamping unit (32). [6] Anti-submarining system (82) for a vehicle seat (10), comprising: a tensioning element (30) spanning a portion of a vehicle seat (10) between opposing frame elements; and a control device (84) for tensioning the tensioning element (30) to impart increased stiffness to the part of the vehicle seat (10) in response to a perceived dynamic vehicle event. [7] The anti-submarining system (82) of claim 6, wherein the perceived dynamic vehicle event is an acceleration of the vehicle (80) beyond a target acceleration. [8] The anti-submarining system (82) of claim 6, wherein the perceived dynamic vehicle event is a potential collision of the vehicle (80) with another object. [9] The anti-submarining system (82) of claim 6, further comprising a tensioning unit (32) selected from a group consisting of an inertial locking retractor, an electric retractor, and a pyrotechnic retractor. [10] The anti-submarining system (82) of claim 6, further comprising an inflatable member (66) connected to the tensioning member (30), wherein the inflatable member (66) is deployable in response to tensioning of the tensioning member (30).

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