Abstract:
An energy absorption device comprises an elongated base member ( 22 ) and an elongated mechanically fused spring arm ( 30 ) extending longitudinally from a first end ( 32 ) secured to the base member to a free distal end ( 34 ). The spring arm has resilience for storing mechanical energy when flexed from a normally unflexed position&#39; to a flexed position. During such movement, the resistance offered by the mechanical fusing must be overcome. Thus the device serves both to store and to dissipate mechanical energy. Suitable fusing mechanisms include shear pins and mechanical fuse strips ( 40 ). A system comprising a passenger safety crossbar ( 10 ) supported by a pair of such energy absorption devices is also disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to energy absorption devices and to a system using same to protect vehicle passengers by absorbing crash energy.  
       BACKGROUND TO THE INVENTION  
       [0002]     In some vehicles, school buses being a particular example, safety devices such as ordinary seat belts or shoulder harnesses may be considered unsuitable not only because they may become a source of injury if not used properly but also because some of the young occupants may be disinclined to use the devices in the intended manner or at all.  
         [0003]     In view of such considerations, various restraint systems which include a safety bar adapted to extend across the lap of seated passengers have been proposed for buses. These include the safety bar system described in U.S. Pat. No. 4,681,344 (Majerus) granted on Jul. 21, 1987, the restraint system described in U.S. Pat. No. 4,930,808 (Mikoll et al.) granted on Jun. 5, 1990, and the restraint apparatus described in U.S. Pat. No. 5,853,193 (Marshall) granted on Dec. 29, 1998. At least in the latter two cases, the systems described have a degree of flexibility or give beyond mere padding that serves to absorb the kinetic energy of a passenger who impacts the bar during a crash. But, if the amount of flexibility is designed with teenagers or adults in mind, the system may be excessively rigid for a six year old sitting alone or even with another six year old. Likewise, if the amount of flexibility is designed with a six year old in mind, the system may be too flexible for a teenager or adult or two teenagers or adults sitting together.  
         [0004]     Accordingly, there is a need for a passenger safety crossbar system which can afford effective protection over a significant range of passenger weights. As well, there is a need for an energy absorption device that can be adapted to support a passenger safety crossbar and serve to protectively absorb energy transmitted to the device from a crash impact on the crossbar either from a relatively light passenger or from relatively heavy passengers.  
       SUMMARY OF THE INVENTION  
       [0005]     In a broad aspect of the present invention, there is provided an energy absorption device comprising an elongated base member, an elongated spring arm extending longitudinally from a first end secured to the base member to a distal end, the arm having resilience for storing mechanical energy when flexed from a normally unflexed position to a flexed position, and mechanical fuse means for providing fuse resistance to the flexing of the arm from the unflexed position to the flexed position. When the spring arm is in the unflexed position its distal end is relatively near the base member. When the spring arm is in the flexed position its distal end is relatively far from the base member.  
         [0006]     Herein, the term “mechanical fuse” means an element which offers a predetermined amount of resistance (“fuse resistance”) to a mechanical force. When the resistance is overcome by a suitably high force, the fuse actuates by breaking or deforming in a destructive manner thereby dissipating mechanical energy. Thus, when the spring arm is flexed from the unflexed position to the flexed position, energy is absorbed and managed in two different ways. Firstly, by virtue of the arm&#39;s spring characteristic, mechanical energy is absorbed and stored in the arm. Secondly, since fuse resistance must be overcome in order to flex the arm from the unflexed position to the flexed position, mechanical energy is absorbed and dissipated by the mechanical fuse means. In any given case, the amount of energy absorbed and stored by the spring arm relative to the amount of energy absorbed and dissipated by the mechanical fuse means will depend upon the amount of fuse resistance.  
         [0007]     In one embodiment, the spring arm is mechanically fused by an elongated mechanical fuse strip comprising a central portion extending lengthwise over the arm and a plurality of fuse tabs extending transversely outward from the central portion to the base member. Each of the tabs is secured to the base member for providing fuse resistance to the flexing of the arm from the unflexed position to the flexed position.  
         [0008]     Advantageously, the central portion of the fuse strip and the tabs are integrally formed. Further, the central portion comprises opposed longitudinally extending first and second sides connected by crosspieces at spaced intervals. A first sub-plurality of the tabs extends transversely outward from the first side of the central portion, and a second sub-plurality of the tabs extends transversely outward from the second side of the central portion.  
         [0009]     By directing the force of mechanical energy from an external source to the distal end of the spring arm such that the arm is flexed from its unflexed position to its flexed position, a part of the energy may be stored and another part dissipated.  
         [0010]     The spring arm may be mechanically fused by other means, for example, by a plurality of shear pins secured at spaced intervals along the base member, each fuse extending over the arm for providing fuse resistance to the flexing of the arm from the unflexed position to the flexed position.  
         [0011]     In some applications, it may be considered desirable to provide a stage of resistance beyond that offered by fuse resistance. Advantageously, a further stage of resistance is provided a flexible strap formed from seat belt or similar material. One end of the strap is connected to the base member and an opposed end is connected to the spring arm. The strap has a length sized to limit the arm from flexing beyond a predetermined maximum flexed position.  
         [0012]     Energy storage devices as described above may be used in a variety of applications. In one such application, the distal end of the spring arm is adapted to carry an end of a passenger safety crossbar.  
         [0013]     Accordingly, and in another aspect of the present invention, there is provided a system for protecting a passenger seated in a vehicle on a vehicle seat, the system comprising a passenger safety crossbar extending between opposed ends with each end being carried by the distal end of the spring arm of an energy absorption device as described above. In the present context, each energy absorption device may be referred to as a crossbar support. In practice, the spring arm and the crossbar include suitable padding.  
         [0014]     The base member of each such crossbar support extends upwardly and rearwardly from a lower end mounted in the vehicle forward of the seat. Preferably, the mounting of at least one of the supports is a pivotal mounting which permits movement of the crossbar from a closed position protecting a passenger while seated in the seat to an open position permitting passenger access to and egress from the seat.  
         [0015]     In a preferred embodiment where one of the base members is pivotally mounted, the system includes means for releasably latching the base members to a frame member of the seat. Further, the crossbar is formed from a resilient material for springing the crossbar to its open position when the base members is unlatched from the frame member.  
         [0016]     The spring arm and fuse resistance provided by each crossbar support in the foregoing system may be designed to absorb a predetermined amount of energy. If the supports include flexible straps (as is preferably the case) to provide a further stage of resistance as described above then, in cases where the predetermined amount of energy is surpassed, further energy will be dissipated when the straps reach their maximum extensions.  
         [0017]     It will be noted that the spring arms and the crossbar effectively serve to compartmentalize a passenger in his or her seat both in the unflexed and flexed positions of the spring arms. The compartmentalization is enhanced by the resilience of the spring arms which will serve to urge the arms toward their unflexed positions after deflection resulting from the impact of a passenger on the crossbar. Thus while a passenger will bear against the crossbar during a crash and may lift away from his or her seat as the crossbar moves with deflection of the spring arms, there will be a return force which will assist to return the passenger to his or her seat. The compartmentalization is enhanced by the flexible straps because they not only provide a second stage of resistance, but can act as a flexible barrier in the case of side impacts and angled impacts.  
         [0018]     The foregoing and other features and advantages of the present invention will now be described with reference to the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is an isometric view of the framework of a conventional bench seat on a bus and a passenger safety crossbar system, the system including a crossbar and a pair of energy absorbing crossbar supports in accordance with the present invention.  
         [0020]      FIG. 2  is a side elevation view of the crossbar system illustrated in  FIG. 1 .  
         [0021]      FIG. 3  is an isometric view as in  FIG. 1 , but showing the crossbar in an open position.  
         [0022]      FIG. 4  is a side elevation view of the crossbar system illustrated in  FIG. 3 .  
         [0023]      FIG. 5  is a section view showing the crossbar support in  FIG. 2  in more detail.  
         [0024]      FIG. 6  is an isometric view of one of the crossbar supports.  
         [0025]      FIG. 7  is an end elevation view of the crossbar support shown in  FIG. 6 .  
         [0026]      FIG. 8  is a top view of the crossbar support shown in  FIG. 6 .  
         [0027]      FIG. 9  is a side elevation view of the crossbar support shown in  FIG. 6 .  
         [0028]      FIG. 10  is a bottom view of the crossbar support shown in  FIG. 6 .  
         [0029]      FIG. 11  is a top view of a mechanical fuse strip forming part of the crossbar support shown in  FIG. 6 .  
         [0030]      FIG. 12  is a side elevation view that representationally shows the crossbar system in use during normal travel.  
         [0031]      FIG. 13  is a side elevation view that representationally shows the crossbar system in use at a moment shortly after a crash has occurred.  
         [0032]      FIG. 14  is a side elevation view that representationally shown the crossbar system in use at a subsequent moment after a crash has occurred.  
         [0033]      FIG. 15  is an end view illustrating the natural, unstressed shape the crossbar shown in  FIGS. 1-5 . 
     
    
     DETAILED DESCRIPTION  
       [0034]     In  FIG. 1 , the framework of a bench seat generally designated  200  is shown together with a pair of energy absorbing crossbar supports generally designated  20 ,  20   a.  As well,  FIG. 1  shows a portion of the framework of a similar bench seat generally designated  200   a  positioned immediately in front of seat  200 . Conventional padding for seats  200 ,  200   a  is not shown in  FIGS. 1-5 . But, such padding is depicted in  FIGS. 12-14 .  
         [0035]     Typically, a bus (not shown) will include a number of seats such as seats  200 ,  200   a  on one side of a passenger aisle, and a number of additional seats which are mirror images of seats  200 ,  200   a  on the other side of the passenger aisle. All views in  FIGS. 1-4  are from the aisle.  
         [0036]     The framework for each seat  200 ,  200   a  includes an outer side  205  supported by a rail  300  which forms part of and extends along an inner wall of the bus. An inner side  210  of the framework is supported by a pair of legs  215 ,  216  which include floor plates  217 ,  218  used to secure the legs to the floor of the bus. Further, the framework includes a side arm structure  220 , and an angular strut  230  positioned generally below the side arm structure.  
         [0037]     As best seen in  FIG. 5 , crossbar support  20  includes an elongated base member  22  extending upwardly and rearwardly from a lower end  23  mounted forward of seat  200  by means of a rod  80  which extends into a pivot connection  82 . Pivot connection  82  includes a pivot pin  83  which extends transversely through rod  80 , and a rod  85  which is threaded into a bracket  231  at the upper end of strut  230  of seat  200   a.  The threaded connection between rod  85  and bracket  231  allows length adjustments to be made so that support  20  can be precisely fitted between seats  200 ,  200   a.    
         [0038]     Crossbar support  20  also includes an elongated spring arm  30  extending longitudinally upwardly and rearwardly from a lower end  32  secured to the base member to a distal end  34  which is adapted to carry an end of a passenger safety crossbar  10 .  
         [0039]     Arm  30  has resilience for storing mechanical energy. Thus, when arm  30  is flexed from the normally unflexed position shown in  FIG. 5  (viz. where arm  30  extends along base member  22 ) to a flexed position as indicated by broken line  100  (viz. where arm  30  bends in an arc away from base member  22 ), there is a resilient force tending to return the arm to its unflexed position.  
         [0040]     As described below in more detail, crossbar support  20  further includes a plurality of mechanical fuses  40  to provide mechanical fuse resistance to flexing of arm  30 . When the arm  30  flexed to the position indicated by line  100 , the fuses will break or shear thereby absorbing and dissipating mechanical energy while arm  30  absorbs and stores mechanical energy.  
         [0041]     Crossbar support  20  also includes a flexible strap  50  which is connected at one end to base member  22  and at the other to spring arm  30 . In  FIG. 5 , strap  50  is compactly folded back and forth upon itself within base member  22 . However, as indicated by arrow  101 , it will be drawn outwardly with spring arm  30  when the arm flexes. When fully extended, the strap will limit further flexing of the arm.  
         [0042]     In  FIGS. 1, 2  and  5 , crossbar support  20  is latched in a closed position. To facilitate latching, one portion  60  of a conventional latching mechanism is carried by segment  221  of side arm structure  220  while a cooperating portion  61  is carried by crossbar support  20 . When unlatched as shown in  FIGS. 3 and 4 , crossbar support  20  is held upwardly and away from side arm structure  220  by crossbar  10 . This allows passengers easy access to and egress from the seating area provided by seat  200 . More particularly, and as best seen in  FIG. 15 , crossbar  10  is formed from a resilient material with a longitudinal twist about its longitudinal axis  11 . This is its normal, unstressed shape, and thus naturally holds crossbar support arm  20  in the open position shown in  FIGS. 2 and 4 . To then move crossbar support  20  to its closed position, a passenger normally will pull rearwardly on crossbar  10 . As can be seen in  FIGS. 1, 2  and  5 , the longitudinal twist which is visible in  FIG. 15  is then absent. When crossbar support  20  is subsequently unlatched, the resilience of crossbar  10  lifts the support back to its open position.  
         [0043]     Referring to  FIGS. 1 and 3 , the structure of crossbar support  20   a  is substantially the same as that of crossbar support  20 , its distal end  34   a  normally holding the end of crossbar  10  opposite to that normally held by distal end  34  of support  20 . The lower end of support  20   a  is pivotally carried by a pivot connection  82   a  substantially the same as pivot connection  82 . Pivot connection  82   a  includes a rod  85   a  which is threaded into bracket  88  mounted on rail  300 , the latter of which is a normal part of a conventional school bus (not shown). The upper end of support  20   a  is held by a brace  89  such that support  20   a  extends substantially parallel to support  20 .  
         [0044]     FIGS.  6  to  11  illustrate aspects of crossbar support  20  in more detail. The support  20  includes an elongated mechanical fuse strip  40  which extends over spring arm  30 , and which is integrally formed from thin sheet steel. Strip  40  comprises a central portion having opposed longitudinally extending sides  41 ,  42  connected at spaced intervals by crosspieces  43 , a first plurality of fuse tabs  44  extending transversely outward from side  41 , and a second plurality of fuse tabs  45  extending transversely outward from side  42 . All of the tabs are secured in slots  25  on opposed sides of base member  22 . When spring arm  30  is flexed, it bears against the tabs and when flexed to a sufficient degree will break or shear the tabs thereby absorbing and dissipating mechanical energy.  
         [0045]     As indicated above, a crossbar support may be mechanically fused by means other than the mechanical fuse strip that has been described. For example, with incidental structural modifications that will be readily apparent to those skilled in the art, individual shear pins could be generally positioned where each crosspiece  43  is positioned as shown in  FIG. 3 , and would serve to resist flexing of a spring arm such as spring arm  30 . However, a potential disadvantage of shear pins is that when they do break shear they may leave ragged edges which in themselves may provide a heightened risk of injury in the circumstances of a crash.  
         [0046]     With a crash test dummy serving as a passenger  400 , FIGS.  12  to  14  illustrate the use of the present invention in a representative manner. In  FIG. 12 , the situation is one of normal travel. Passenger  400  is seated rearwardly away from crossbar  10  which is carried by crossbar support  20 .  FIG. 13  depicts the situation at an early moment after a collision has occurred. Passenger  400  has been propelled forward and has impacted on crossbar  20 . In response, the spring arm in support  20  has begun to flex. Crossbar  10  has moved slightly forwardly and upwardly in relation to seat  200 . Subsequently, in  FIG. 14 , the momentum of passenger  400  has forced the spring arm of support  20  to a fully flexed position where further flexing is restrained by strap  50 . With further reference to  FIG. 14 , it will be understood that when the forward momentum of the passenger  400  has ended then the stored energy in spring arm  30  will urge the passenger back towards seat  200 . At all times crossbar support  20  has remained latched in its closed position.  
         [0047]     Various modifications and changes to the embodiment that has been described can be made without departing from the scope of the present invention, and will undoubtedly occur to those skilled in the art. The invention is not to be construed as limited to the particular embodiment that has been described and should be understood as encompassing all those embodiments which are within the spirit and scope of the claims that follow.