Abstract:
A vehicle seat headrest with a carrier structure including at least one bar and a supporting member in a normally utilization position. In the event of an accident, the supporting member leaves the utilization position and assumes a crash position, in which the supporting member is located in front of the utilization position at least in the x-direction. An expandable container is disposed between the bar and the supporting member in a normally non-expanded state. A source of pressurized gas is connected to the container. A trigger device releases the gas in the event of an accident so that the expandable container is filled with gas and is in an expanded state so that the supporting member is in the crash position.

Description:
FIELD OF THE INVENTION 
   The application relates to an optimized headrest for the seat of an automotive vehicle e.g., for a front seat thereof. In a known manner, the headrest comprises padding providing safe and comfortable head support for the occupant of said seat. A supporting member, which is located substantially behind the padding and is padded thereby, provides mechanical stability to the headrest. Finally, the headrest has a carrier structure that is connected to a seat back of the seat and comprises at least one bar. Typically, said bar is slidably disposed in the seat back. In most cases, two bars are provided for. An advantage is achieved when the incline of the supporting member can be adjusted relative to the bars. 
   DESCRIPTION OF THE RELATED ART 
   In the event the automotive vehicle is involved in an accident, it is important that the occupant&#39;s head be supported by the headrest. This is particularly important as far as rear impacts are concerned. Usually, the head of an occupant will not continuously rest on the padding; normally, the occupant will rather hold his head at a certain distance from the padding of the headrest. This is disadvantageous in accident situations because, in an accident situation, the occupant&#39;s head will have to move a certain distance before coming to rest against the headrest. It is well known that precisely the backward movement of the head relative to the upper body is disadvantageous as it may cause damage to the cervical spine. This injury is known as “whiplash”. The art teaches various approaches to restrain backward movement of the head relative to the trunk in accident situations. Proposals have been made for example, in which the overall headrest is actively moved forward or in which the occupant&#39;s upper body sinks deeper into the padding of the seat back. 
   SUMMARY OF THE INVENTION 
   The invention also aims at possibly preventing, at least restraining, an occupant&#39;s head from moving backward in an accident situation. It is the object of the invention to develop a headrest which, in the event of a crash, provides support in closer proximity to the occupant&#39;s head than in the normal operating condition of the automotive vehicle, using the simplest possible means. 
   The solution to this object is achieved by the headrest having the features of claim  1 . 
   In this headrest, there is provided a fast actuation drive in the form of an expandable container that is supplied with pressurized gas from a source in the event of an accident. Said container expands very fast from its normal state in which it is not expanded, to the expanded state, thereby taking the supporting member along, the expandable container being supported by the at least one bar or by a part connected therewith. This permits to move the support member from the utilization position into the crash position within the available time to do so. This length of time starts when the crash sensor responds and must have ended before the head of an occupant is snapped backwards, towards the supporting member. 
   Various configurations of the expandable container are possible. A piston and cylinder unit may for example be utilized, with the piston being for example connected to the bar and the cylinder with the supporting member (or vice versa). Said piston and cylinder unit may exert either a compressive force or a tensile force. A small airbag may also be used as the expandable container. It is preferred that the expandable container expands in the direction in which the supporting member is to be moved away from the bar, meaning in the x-direction and in the z-direction. A member that may be unfolded in accordion style, for example an undulated cylinder that is closed at its ends, is also suited for the expandable container. 
   An electrically ignitable pyrotechnic charge is preferably employed as the source of pressurized gas. The pyrotechnic charges utilized here are similar to those used for airbags. Accordingly, said pyrotechnic charges may also be triggered by a crash sensor in a manner similar to that used for enabling airbags. In an alternative configuration, a compressed gas bottle such as a CO 2  bottle is used. Normally, it is inactive, meaning locked. It is released by an electrical pulse. 
   The pressurized gas source communicates with the container. It may be located in said container or be connected to said container through a channel. It is thereby advantageous to provide a buffer reservoir that is disposed between the source and the container and buffers the initial pressure surge of the compressed gas source that may occur upon release of the latter, thus protecting the container from overpressure. Thus, the container is subjected to a pressure that is lower than a prescribed threshold pressure. 
   The trigger device is preferably operated electrically. As a result, it may be actuated in a suited manner by a crash sensor. 
   In a particularly advantageous design feature of the invention, the supporting member is caused to move relative to the at least one bar in the event of an accident. No visible difference can be observed between this headrest and a normal headrest that is not equipped in accordance with the invention. All the drives means and the like may be concealed within the headrest, more specifically within the padding or the casing of the padding. The additional crash position will only become apparent in the event of an accident. The electrical leads may be disposed within the bars and the bars themselves may also be used as electrical leads. 
   From the utilization position into the crash position the supporting member moves both in the z-direction and, as a result thereof, upward by for example 2 to 10 cm, preferably by 4 to 8 cm, and toward the front, in the positive x-direction, by for example 2 to 8 cm, preferably by 3 to 6 cm. The crash position it now assumes is advantageous for rear collisions. The trigger device is preferably released when the crash sensor senses a rear collision. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will become more apparent upon reviewing the appended claims and the following non restrictive description of embodiments of the invention, given by way of example only with reference to the drawing. In said drawing: 
       FIG. 1 : is a schematic diagram of a headrest that is connected to a seat back, a top region of which only is shown, with the headrest being in the utilization position, 
       FIG. 2 : is a side view like  FIG. 1  of a second embodiment of the headrest, but now in the crash position, 
       FIG. 3 : is a side view like  FIG. 1  of a third embodiment of the headrest in the utilization position, 
       FIG. 4 : is a side view like  FIG. 1  of a fourth embodiment of the headrest in the utilization position, and 
       FIG. 5 : is a side view like  FIG. 1  of a fifth embodiment of the headrest in the utilization position. 
   

   DETAILED DESCRIPTION 
   The following description makes use of the coordinate system currently utilized in automotive engineering, with the x-axis in the direction of travel, with the y-axis transverse to said direction of travel and pointing toward the left and with the z-direction oriented perpendicular and upward, see  FIG. 1 . The headrest has two bars  20  that are retained in a seat back  22 , the bars  20  can be displaced in their longitudinal direction relative to said seat back  22  for permitting height adjustment of the headrest. 
   The bars  20  are bent several times. The bends are located within the contours of the supporting member  26 . As shown in  FIG. 1 , the bar  20  has at least one (lower) oblique portion  24  that extends approximately in the direction in which the movement is intended to be executed toward the front and toward the top. According to the embodiment as shown in  FIG. 2 , there is also provided an upper oblique portion  25  that is oriented parallel to the lower oblique portion  24 . 
   The bars  20  carry a supporting member  26 . In the exemplary embodiments as shown in  FIG. 1  and  FIG. 2 , it is substantially made from one piece of plastic material, e.g., by injection moulding. It carries a padding  28 . On its outer side, said padding is covered and enclosed by a cover  30  or the like. 
   The supporting member  26  has two guiding parts  32  that are located in the lower oblique portion  24  around which they form a more or less surrounding grip. In the utilization position, said guiding parts  32  are in the lowermost part of the lower oblique portion  24  where said oblique portion  24  merges into a bend interrupting the normal course of the bars. The oblique portion  24  is so long and is configured in such a manner that, when the supporting member  26  is in the crash position, the guiding parts  32  are located at the upper end of the lower oblique portion  24 , meaning in the region where it merges into a bow region  34 , see  FIG. 2 . The guiding parts  32  may be displaced along the oblique portions  24 . 
   In the implementation as shown in  FIG. 2 , in which there is also provided an upper oblique portion  25 , additional upper guiding means are provided for guiding the supporting member  26  along the upper oblique portion  25 . Like the path of the guiding parts  32  in the lower oblique portion  24 , the path of the supporting member  26  in the upper oblique portion  25  is bounded. A loop  36  is for example used as the upper guiding part. It cooperates with a cross-tie member  36  that joins the two bars  20  together at the uppermost end of the bow region  34 . 
   At the cross-tie member  36 , there is linked a cylinder  40  of the expandable container; for this purpose, the cylinder  40  has a connecting piece  42  located at its upper end. A piston  44  is slidably guided within cylinder  40 . Cylinder  40  and piston  44  define an expansion space  58 . The piston  44  has a piston rod  46  that is supported by an abutment  48 . Said abutment is part of the supporting member  26  and is located between the two bars  20 . The abutment  48  is substantially located between the two guiding parts  32  and is disposed within the contour of the actual headrest body. 
   In proximity to the cylinder  40  there is disposed a pyrotechnic charge  50  connected thereto. It is constructed like a primer that more specifically has a discharge end pointing downwards. Toward the top, electric leads  52  protrude from the primer, they are connected to a crash sensor  53  that performs control functions and forms the trigger device. The discharge opening is located in a chamber  54  that is connected to the actual expansion space  58  through a passage  56 . In the chamber  54 , a first high pressure surge is allowed to drop, it is configured accordingly. As a result, the expansion space  58  is only loaded with a pressure for which the piston and cylinder unit has been designed. The expandable container  40 ,  44  is not subjected to a pressure in excess of a threshold pressure of e.g., 200 bar. 
   If the pyrotechnic charge  50 ;  68  is ignited, the chamber  54  fills with propellant gas that flows through passage  56  and reaches the expansion space  58 . The expansion space is the work space of the expandable container. Preferably the source of pressurized gas is a solid propellant charge. The gas pressure causes the expansion space  58  to increase in volume, the cylinder  40  is pulled downward, the piston remains stationary. Put another way, the cylinder and piston arrangement contracts. Once the piston  44  has travelled the major portion of the allowable distance within the cylinder  40 , it arrives behind a return stop  60 . Said return stop prevents the piston from travelling back, even if the supporting member  26  is loaded. As a result, it retains and secures the supporting member  26  in the crash position. In the concrete exemplary embodiments, it is realized by tongues that have been cut out from the jacket of cylinder  40  and project inward at an incline. 
   In contrast to the exemplary embodiments as shown in the  FIGS. 1 and 2 , the variant as shown in  FIG. 3  is operated with tensile force and not with compressive force. Now, the connecting piece  42  that is connected to the cylinder  40  is hinge-linked thereto in the upper region of the supporting member  26 . Now, the piston rod  46  is supported by the bars  20  via the abutment  48 . The expansion space  58  is now located in immediate proximity to the connecting piece  42 . 
   In the embodiment as shown in  FIG. 4 , the expandable container is realized by a pleated bellows  62 . It may for example be made from an elastomeric or a plastic material. Said pleated bellows  62  is disposed between a connecting piece  42  and a plate  64 , thus defining a sealed expansion space  58 . The plate  64  is connected to the abutment  48  via a tube portion  66 . Said abutment is in turn fastened to a crosspiece (not shown) that joins the two bars  20  together. The connecting piece  42  is hinged to the supporting member  26  in proximity to an upper end region of said supporting member  26 . 
   In the configuration as shown in  FIG. 4 , a pyrotechnic charge  50  is located within the expansion space  58 . Its structure is the same as in the afore mentioned exemplary embodiments, meaning it is also implemented as a powder charge. The leads  52  run through the plate  64  and in the interior of the tube portion  66  before exiting outside thereof through an opening. 
   In the configuration as shown in  FIG. 5 , the expandable container is in turn formed by a cylinder  40  and a piston  44  that is now configured to be a hollow piston. The cylinder  40  is connected to the connecting piece  42  that is hinged to the supporting member  26  in the upper region thereof. The piston is connected to a tube portion  66  that in turn provides passage for the electrical lead  52  therethrough. 
   Like in  FIG. 4 , the source of pressurized gas is again disposed within the expansion space  58 . It is now configured to be a pressurized gas container  68  that is filled with a highly pressurized non-toxic gas such as CO 2 . The pressurized gas container  68  is tightly closed in its lowermost region by an ignition plate  70 . Said ignition plate is connected to the lead  52 . When the ignition plate is electrically ignited, the pressurized gas container  68  is open at the neck of the bottle and the pressurized gas it contains is allowed to fill the expansion space  58 . 
   Like in the exemplary embodiments as shown in the  FIGS. 3 and 4 , the abutment  48 , which is respectively connected to the piston rod  46  or to the tube portion  66 , is fixed to the bars  20  whilst the connecting piece  42  is connected to the supporting member  26 . If the expansion space  48  is under pressure, the piston  44  moves upward and brings the supporting member  26  into the crash position. Reduced-size airbags may also be used as the expandable container.