Abstract:
The headrest of an automotive vehicle seat has at least one bar ( 20 ) and one supporting member ( 26 ). Normally, the supporting member ( 26 ) is in a utilization position. When the automotive vehicle is involved in an accident, the supporting member ( 26 ) leaves the utilization position and adopts an accident position in which it is located in front of the utilization position. The at least one bar ( 20 ) comprises an oblique portion ( 30 ) that is located above an upper edge ( 32 ) of a backrest of the automotive vehicle seat. Said oblique portion has one component in the x direction and one component in the z direction. The supporting member ( 26 ) comprises a guide region ( 34 ) that conforms to the oblique portion ( 30 ) of bar ( 20 ) and that is movable relative to the oblique portion ( 30 ). An elastic means (spring  48 ) biases the supporting member ( 26 ) in the accident position. A releasable locking device ( 52 ) is associated with the elastic means, which it normally blocks. When the automotive vehicle is involved in an accident, the elastic means is released and causes the supporting member ( 26 ) to move from the utilization position to the accident position.

Description:
BACKGROUND 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 to comfortably support an occupant&#39;s head. A supporting member, which is located substantially behind the padding and is padded thereby, provides mechanical stability to the headrest. Finally, the headrest has at least one bar that is in most cases slidably disposed in an associated backrest. In most cases, two bars are provided for. Headrests are known in which the inclination of the supporting member relative to the bars can be adjusted. 
   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; in most cases, 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. Approaches have become known for example, in which the overall headrest is actively moved forward or in which the occupant&#39;s upper body is allowed to sink deeper into the padding of the backrest. 
   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 . 
   BRIEF DESCRIPTION OF THE INVENTION 
   In this headrest, an oblique portion is inserted into the normal orientation of the bars. The oblique portion is bounded by a lower bend where the oblique portion is bent forward toward the positive x-axis, at an approximately 30° bend angle. The oblique portion ends at a top bend from which the upper end portion of the bar takes departure, said upper end portion being oriented substantially in much the same direction as the portion of the bar located underneath the oblique portion. Put another way, the bar is bent, with the bent portion forming the oblique portion thereof. 
   Upon release of the locking device, the supporting member is moved forward (in the x direction), and upward (in the x direction) as well, along the oblique portion. As it passes from the utilization position to the accident position, the supporting member rises in the z direction i.e., upward, by 4 to 8 cm for example, while concurrently moving forward in the positive x direction by approximately 3 to 6 cm for example. This accident position is advantageous in the event of a rear impact. The releasable locking device is preferably enabled upon detection of a rear impact by an associated crash sensor. 
   In a particularly advantageous design feature of the invention, the bars, in addition to performing their normal function, will now also be used to guide the movement of the supporting member of the headrest and said supporting member will be caused to move relative to the bars as a result of the accident. In the normal utilization position, the oblique portions are not visible, they are hidden within the covering of the padding. They will only become apparent in the accident position when they are located somewhat underneath the supporting member. In normal operation, the oblique portions are concealed. 
   In an advantageous development, the supporting member is made from one piece. It is preferably made from a plastic material such as POM e.g., by injection molding. 
   In an advantageous development, the supporting member has an opening that extends above a plate in the x direction and that is openable to an extent allowing passage of a transverse part therethrough. During assembly, the bars may thus be threaded into the guide regions and the supporting member is then pressed against the transverse part until the transverse part is behind the opening. This makes assembly easy. 
   In a development, the supporting member has a retaining system that cooperates with the bar and/or a transverse part and that keeps the supporting body in the accident position once it has been reached. This retaining device prevents the supporting member from yielding too much under the load of a head. The retaining device may be a lug behind which the transverse part extends when the accident position has been reached. Further, it is considered to push the guide regions so far upward in the accident position that they now are at least partially above the oblique portion so that, during an accident, they will not be pushed back under the load of a head. 
   Various release means may be used for the locking device, said release means being preferably designed as replaceable release means. This means that, once released, the headrest can be repaired. The release device must be quite quickly responsive. When the crash sensor enables the release device, the locking device must be released as quickly as possible. A fusible wire link, which is destroyed by an appropriate electrical current, has proved an efficient release device. Very fast release, occurring within milliseconds, is achieved in this manner. Alternatively, the release device could also comprise an electrically actuatable priming cartridge that pushes a retaining means into the release position or that destroys a retaining wire link. Eventually, an electromagnet may be utilized, said electromagnet attracting a retaining means, a catch for example, into the release position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and features of the invention will become apparent in the remaining claims and in the following description of exemplary embodiments of the invention that will be explained in more detail herein after with reference to the drawing in which: 
       FIG. 1 : is a side view of a headrest that is connected to a backrest the upper portion of which only is shown, with the headrest being in the utilization position, 
       FIG. 2 : is a perspective view of the headrest of  FIG. 1 , viewed obliquely from behind, 
       FIG. 3 : shows the headrest of  FIG. 1 , which is now in the accident position, 
       FIG. 4 : is an illustration similar to  FIG. 2  with the headrest now being in the accident position and 
       FIG. 5 : is a side view similar to  FIG. 1  of a second embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The following description uses the coordinate system commonly used in the automotive technique, the x axis being oriented in the direction of travel, the y axis across the direction of travel in the horizontal plane and the z axis in the vertical plane. 
   The headrest has two bars  20  that are retained in a backrest  22 , the bars  20  can be displaced in their longitudinal direction relative to the backrest  22  for permitting height adjustment of the headrest. 
   At their top region, the bars  20  are integrally joined together by a transverse part  24  to form a U-shaped piece. The bars  20  and the transverse part  24  carry a supporting member  26  which, in the exemplary embodiment shown, is substantially made from a single piece of plastic e.g., by injection molding. Said supporting member  26  will be discussed in greater detail herein after. Finally, the headrest comprises a padding  28  in the known manner, said padding being shown in dash-dot line in  FIG. 1 . 
   From all the Figures it can be seen that the bars  20  comprise an oblique portion  30 . Within the oblique portion they are substantially straight, they are oriented so as to bend forward from the normal direction, with one component in the positive z direction and one component in the positive x direction, said oblique portion  30  being preferably inclined at an angle of about 15.degree. to the z direction, as measured in the direction toward the positive x direction, with a possible angular range of from 0.degree. to 50.degree., more preferably from 10.degree. to 30.degree. The backrest is thereby in the mounting position in which it is inclined backward in the direction of the negative x axis at an angle of about 19 to 20.degree. relative to the z axis. The oblique portion is from 5 to 15 cm in length. As shown in  FIG. 1 , the bar  20  is bent at an angle of about 15.degree. at the point which forms a lower bend and from which the oblique portion  30  takes departure. The oblique portion  30  is always located above the backrest  22 , more specifically above an upper edge  32  of the backrest  22 . Above the oblique portion, the bar  20  is approximately returned to the initial orientation it had underneath the oblique portion. There, there is an upper bend. Accordingly, the oblique portion is defined by two bends. 
   The supporting member  26  comprises a guide region  34  for each bar, said guide region surrounding, at least partially, the oblique portion  30 . In the normal utilization position as it is shown in  FIG. 1 , the guide regions  34  are located in the lowermost section of the oblique portion  30  and are partially located in the bend there. The guide regions  34  are configured so that, from the utilization position shown in  FIG. 1 , they are allowed to easily glide, via the oblique portion  30 , into the accident position of the headrest shown in  FIG. 3 . 
   The oblique portion  30  is located within the volume devoted to the supporting member  26 , as best shown in  FIG. 1 . More specifically, the lower end of the oblique portion is located slightly above a lower end of the supporting member. The supporting member extends as far as the transverse part  24 . In the region of the transverse part  24 , there are provided two elongated, substantially oval loops  38  encompassing the transverse part  24 . In the utilization position, the transverse part is located within the one end region of the loop  38  whereas, in the accident position, the transverse part  24  fits against the other end of the loop  38  (see  FIG. 3 ). The loops  38  guide the supporting member  26  as it moves from the normal utilization position to the accident position. 
   The supporting member  26  has a plate  40  the back side of which fits on the bars  20  and on the transverse part  24  on the front side thereof in the normal utilization position. The supporting member  26  further has a housing  44  which, in the utilization position, is located between the bars  20  and underneath the transverse part  24 . It rigidifies the supporting member and its upper edge, which is inclined at an oblique angle, forms part of the loops  38 . On its back side, the housing  44  opens to a slot  46  in which there is disposed a spring  48  configured to be a tension spring. Said spring in turn is supported by an abutment  50  that is configured to be approximately hook-shaped and is located in the rearmost, deepest end region of the housing. On the other side, it is supported by the transverse part  24 , in fact in the center of the transverse part. The spring has a relatively high tensile force of 200 N for example and a spring travel of 5 to 10 cm. It is designed to be capable of causing the supporting member  26  together with the padding  28  and the associated parts to move relatively quickly from the normal utilization position ( FIGS. 1 and 2 ) to the accident position ( FIGS. 3 and 4 ). In the accident position, the supporting member is not only located before the utilization position in the x direction, it is also displaced upward in the y direction. This is an advantage because, as a result thereof, on the one side, the supporting member  26  moves closer to the occupant&#39;s head in the x direction, thus providing better support and because, on the other side, in the event of a rear impact, the occupant will move slightly upward so that his head will move higher, this movement being compensated by the headrest as it rises so that on the whole the head is advantageously supported. 
   The spring  48  is blocked by a locking device  52 . For this purpose, an approximately shell-shaped arm  54  is hinged to the transverse part  24  in proximity to the spring  48 . In the normal utilization position it is supported at its lower end by about two approximately triangular brackets  56 , thus preventing the supporting member  26  from moving upward. If the arm  54  is moved in the negative x direction by its lower end, meaning if it is pivoted, it is disengaged from the brackets  56  and the spring  48  is then enabled to pull the entire supporting member  26  upward into the position shown in  FIG. 3 . 
   A release device  58 , which, in the concrete implementation, is configured to be a squib, is connected to the arm  54 . Said squib is electrically ignitable. From  FIG. 1  it can be seen that the release device  58  is connected to a crash sensor  62  through a connection  60  shown in a dashed line. Said crash sensor enables the device in the presence of decelerations as they are typical for a rear impact or a similar accident. Upon ignition of the squib  58  forming the release device  58 , the arm  54  is disengaged and the spring  48  pulls the supporting member  26  in the position shown in  FIG. 3 . The movement of the supporting member  26  in the positive x direction and in the positive z direction is decelerated and stopped by the transverse part  24  abutting against the end of the loops  38  on the one side and by limit stops  61  that are provided above the guide regions  34  and come into contact with the upper end portion  42  of the bars  20  above the oblique portion  30  on the other side. 
   The supporting member  26  is mechanically held in the accident position not by the force of the spring  48  alone, but also by making the following two provisions: firstly, lugs  64  are formed in the rear part of the housing  48 , said lugs being located in the region of the loops  38 . As the supporting member  26  rises, the transverse part  24  rides along the slant upper edge of the housing  44 , moves towards the rear end of the loops  38  and rides over the lugs  64 . Secondly, as the headrest is moving to the accident position, the guide regions  34  ride at least partially beyond the upper bend and are located in the upper end portion  42 . Said upper end portion is about the same length as the length of the oblique portion  30  but is oriented in the same direction as the non bent portion of the bars beneath the lower bend. Upon experiencing a crash load, the guide regions can be supported at their upper end portion  42 . They will remain in their position and not be pushed into the oblique portion. As a result, the position of the supporting member  26  is mechanically stabilized both in its upper and in its lower portion and is thus capable of taking the impact of the head. A certain resilience and, as a result thereof, dissipation of the kinetic energy are achieved by deformations, with the spring  48  being compressed again. What matters is that the supporting member  26  is mechanically held and supported in its accident position in such a manner that it is capable of taking the acceleration forces (impact of a head) acting thereon. 
   Other means that can be quickly enabled can be utilized in lieu of the release device  58  discussed herein above. It is for example possible to hold the supporting member  26  by means of a wire that is configured to quickly melt if the current pulse is sufficiently high. The arm  54  may for example be elastically biased by an additional spring  48  in the swung-out position as shown in  FIG. 3 . Said additional spring  48  is blocked by the fusible wire. It is released upon destruction of the fusible wire. The process is the same as described herein above. 
   Finally, the release device  58  can also be enabled by an electromagnet. Said electromagnet can actuate a catch that retains the arm  54 , which is biased by a separate spring (not shown), in the locked position. As soon as the electromagnetic device is responsive, the arm is disengaged and the above described process takes place. 
   The supporting member  26  may also be formed from several pieces. It may be made from another suited material such as aluminum for example. In the implementation described herein, the supporting member is configured so as to be threadable onto the lower free ends of the bars, which have not been illustrated herein. For this purpose it is provided with an opening  61  that extends in the x direction above a plate  40  and that can be opened far enough to allow a transverse part  24  to be passed therethrough. As a result, the transverse part is within the two loops  38 . As illustrated in all of the Figures, this condition is maintained. 
   Whereas in the exemplary embodiment discussed herein above and illustrated in the  FIGS. 1 through 4  the two oblique portions  30  of the bars  20  are built according to the same principle, this is not the case in the exemplary embodiment of  FIG. 5 . There, as viewed with respect to the vehicle&#39;s interior, the inner bar is inclined to the z axis at a smaller angle than the outer bar. As a result thereof, the supporting member  26  moves slantways towards a side air bag as it rises into the accident position. The occupant&#39;s head is prevented from slipping toward the center of the vehicle and is instead moved towards the side airbag where, now located between said side airbag and the somewhat inclined headrest, it is better held in place than it would be by a headrest that remains parallel to the y axis in the accident position as well.