Abstract:
A device for maintaining height of a headrest relative to a seatback frame includes: a suspension disposed in the seat back frame, configured to be pushed by a passenger during a crash; a linkage rotatably coupled to the seat back frame and rotatably supporting the suspension; and a fixing link inside the seat back frame for maintaining a rotational position of the linkage so as to maintain a height of the suspension.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority to and the benefit of Korean Patent Application No. 10-2006-0122436 filed in the Korean Intellectual Property Office on Dec. 5, 2006, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   (a) Field of the Invention 
   The present invention relates to a device for maintaining height of an active headrest, and more particularly to such a device in which the height at which the headrest is locked varies depending on the amount of force of a vehicle crash. 
   (b) Description of the Related Art 
   An active headrest is a general term that refers to a headrest that automatically rises and supports the head of a passenger to protect the passenger&#39;s head and neck in a vehicle crash. 
   A conventional active headrest includes a self locking device. However, the conventional self locking device locks only if the active headrest rises higher than a reference height, keeping the active headrest raised. That is, the height of the active headrest can be maintained only if force of the crash is greater than a reference value. 
   SUMMARY OF THE INVENTION 
   The present invention provides a device for maintaining height of an active headrest in which a height at which the headrest is locked varies depending on force of a crash. 
   An exemplary embodiment of the present invention provides a device for maintaining height of an active headrest which rotates and rises to support the head and neck of a passenger. A suspension is installed inside a seat back frame to support the passenger&#39;s upper body. The suspension includes a linkage rotatably coupled to an inside of the seat back frame and rotatably supporting the suspension; and a fixing link inside the seat back frame, securing a rotational position of the linkage to fix the height of the suspension. 
   The linkage may be L-shaped, with a first end extended toward the rear of the suspension, an elbow rotatably connected to the seat back frame by a first hinge, and a second end rotatably connected to a side of the suspension by a second hinge, so as to rotatably support the suspension. 
   The linkage may further include a slot between the first hinge and the second hinge, and a plurality of hooking strips with a sawtooth shape at an inside of the slot. 
   A first end of the fixing link may be attached to the seat back frame. A second end of the fixing link may extend toward the slot. The fixing link may be hooked to a hooking strip at a lower part of the slot if amount of rotation of the suspension is small, and to a hooking strip at an upper part of the slot if amount of rotation of the suspension is large, thereby preventing the suspension from returning to its original position. 
   The fixing link may further include a hooking protrusion hooked to the hooking strip at an end portion of the fixing link. 
   One end of the linkage may extend toward the rear of the suspension, the other end of the linkage may be fixed to the seat back frame, and the linkage may be returned to an original position thereof by a restoration spring, which is extended when the linkage is rotated by the suspension, and is returned if force acting on the suspension is removed. 
   One end of the restoration spring may be attached to the seat back frame by a bracket provided with a hook. 
   The hooking protrusion may be wider than the slot, and may be made of elastic material. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the inside of a seat to which a device for maintaining height of an active headrest according to an exemplary embodiment of the present invention is mounted. 
       FIG. 2  is a perspective view showing the outside of the device of  FIG. 1 . 
       FIG. 3  is a perspective view showing the inside of the device of  FIG. 1 . 
   

   DESCRIPTION OF REFERENCE NUMERALS INDICATING PRIMARY ELEMENTS IN THE DRAWINGS 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               100: seat 
               200: active headrest 
             
             
                 
               300: seat back frame 
               400: suspension 
             
             
                 
               500: linkage 
               510: slot 
             
             
                 
               512: hooking strip 
               520: first hinge 
             
             
                 
               530: second hinge 
               600: fixing link 
             
             
                 
               610: hooking protrusion 
               700: restoration spring 
             
             
                 
               800: fixing bracket 
               810: hook 
             
             
                 
                 
             
           
        
       
     
   
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
   As shown in  FIG. 1 , an active headrest  200  according to an exemplary embodiment of the present invention is connected to a suspension  400  which is installed inside a seat back frame  300  by a supporting frame  210  and is supported by the same. 
   The suspension  400  is plate shaped and extends across a substantial portion of the width inside the seat back frame  300 . If a passenger is pushed rearward by a rear collision, the suspension  400  is raised while being pushed rearward. Then, the suspension  400  rotates, raising the supporting frame  210 , and the active headrest  200  along with it, supporting the head and neck of the passenger. 
   If the suspension  400  does not return to its original position, the height of the active headrest  200  is maintained in a state of supporting the passenger&#39;s head and neck. The height of the suspension  400  is maintained by a linkage  500  and a fixing link  600 . 
   As shown in  FIG. 2  and  FIG. 3 , the linkage  500  is connected to both sides of the suspension  400 . The linkage  500  may be L-shaped. A first hinge  520  may be connected to the linkage  500  so that the linkage  500  is rotatably connected to the seat back frame  300 . 
   A first end of the linkage  500  extends toward the rear of the suspension  400 , and a second end extends along and is coupled to the side of the suspension  400  by a second hinge  530 . Accordingly, the linkage  500  rotatably supports the suspension  400  to the seat back frame  300 . Hereinafter, the portion extending toward the rear of the suspension is referred to as portion A, and the portion between the first hinge and the second hinge is referred to as portion B. 
   A slot  510  is formed along portion B of the linkage  500 . 
   A hooking protrusion  610  on the fixing link  600  is housed in the slot  510  so as to move along the slot  510 . A plurality of hooking strips  512 , with a sawtooth shape, are provided inside the slot  510  and serve to catch the hooking protrusion  610 . 
   As shown in  FIG. 2 , the fixing link  600  is attached at a first end to the seat back frame  300 . A second end thereof extends toward the slot  510 . The hooking protrusion  610  is provided on the second end of the fixing link  600 . 
   The hooking protrusion  610  slides upwards within the slot  510  by rotation of the linkage  500 , and is then hooked by the hooking strip  512 , thereby preventing reverse rotation of the linkage  500 . Since the linkage  500  should be returned to its original position by a restoration spring  700  which will be described later, the width of the hooking protrusion  610  may be slightly greater than the width of the slot  510 . 
   In addition, since the hooking protrusion  610  is hooked by the hooking strip  512  and then should slide downward along the slot  510  during the return of the linkage  500 , the hooking protrusion  610  may be able to be elastically deformed so as to pass through the narrow width of the slot  510 . The hooking protrusion  610  may therefore be made of material that can return to its original shape after some deformation, such as, without limitation, plastic or rubber. 
   As shown in  FIG. 2  and  FIG. 3 , a first end of a restoration spring  700  is attached to portion A of the linkage  500 , and a second end is attached to a hook  810  of a fixing bracket  800 , provided inside the seat back frame  300 . The restoration spring  700  returns the active headrest  200  to its original position after the operation thereof. 
   That is, since the restoration spring  700  extends when portion B of the linkage  500  rotates in a direction C ( FIG. 3 ), it urges portion B of the linkage  500  to rotate in a direction D by the restoring force. While portion B rotates in the direction D, the suspension  400 , which has been raised, is lowered. While the suspension  400  is lowered, the supporting frame  210  is also lowered, and thereby the active headrest  200  is also lowered so as to return to its original position. 
   Operation of a device for maintaining height of an active headrest according to an exemplary embodiment of the present invention will be explained hereinafter. 
   If force acts on a passenger during a rear crash, the passenger&#39;s upper body moves rearward. The suspension  400  rotates by force acting on the suspension  400 , and is pushed rearward, rising simultaneously. 
   Portion B of the linkage  500  rotates in a direction C by the rotation of the suspension  400  (referring to  FIG. 3 ). Accordingly, the second hinge  530  rises in the direction C, and the hooking protrusion  610  of the fixing link  600  rises along the slot  510  and is hooked therein. 
   If the force acting on the suspension  400  is removed, the linkage  500  will tend to return to its original position by weight of the suspension  400 . However, since the hooking protrusion  610  is hooked by the hooking strip  512 , the linkage  500  is kept in the raised position, preventing rotation of the suspension  400 , and maintaining the position of the active headrest  200 . 
   Force caused by the body of the passenger varies depending on force by the vehicle crash, and thereby force pressing the suspension  400  also varies. As force increases, amount of rotation of the suspension  400  increases, and thereby amount of rotation of the linkage  500  also increases, increasing the height at which the hooking protrusion  610  of the fixing link  600  is raised. If the force acting on the suspension  400  is removed, the hooking protrusion  610  is hooked to a hooking strip  512  that is relatively higher on the slot  510 . 
   Since a fixing height of the active headrest  200  varies depending on force of the crash, the active headrest operates even when the force is small, thereby continuously supporting the head and neck of the passenger. Accordingly, injuries on a passenger can be minimized. 
   The suspension  400  returns toward the front of the seat  100  if the linkage  500  rotates in the direction D by the restoring force of the restoration spring  700 . Accordingly, the supporting frame  210  lowers, and the active headrest  200  returns to its original position. 
   While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.