Abstract:
According to an aspect of the present invention, a headrest apparatus for a vehicle seat includes a support portion mounted on the vehicle seat, a movable portion supported at the support portion for moving forward, a first arm and a second arm being crossed and rotatably connected each other by a rotation axis and supporting the movable portion to the support portion, and a biasing member provided between the support portion and the movable portion for biasing the movable portion forward relative to the support portion.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application is based on and claims priority under 35 U.S.C. § 119 to Japanese Patent Application 2003-185602, filed on Jun. 27, 2003, the entire content of which is incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    This invention generally relates to a headrest apparatus adapted to a vehicle seat.  
         BACKGROUND OF THE INVENTION  
         [0003]    A known headrest apparatus is described in U.S. patent publication No. 2003/057758. The known headrest apparatus includes a fixed support portion and a pre-stressed movable portion. The support portion and the movable portion are connected via upper and lower levers arranged in parallel with each other. The known headrest further includes a spring for applying the pre-stress to the movable portion.  
           [0004]    According to the known headrest apparatus, when the vehicle crash or pre-crash notice is detected, pre-stress applied to the movable portion by the spring is released by a trigger apparatus to move the movable portion forward relative to the support portion. Thus, distance between a head of an occupant and the headrest becomes proper to reduce injuries given to the head or lower part of neck of the occupant.  
           [0005]    Notwithstanding, with the construction of the known U.S. patent publication No. 2003/057758, in order to transmit restoring force of the spring to the upper and lower levers when pre-stress applied to the movable portion is released, the known headrest apparatus further includes a spring lever for transmitting the restoring force of the spring to the lower lever and a connecting lever for transmitting the restoring force of the spring transmitted from the lower lever to the upper lever, which includes complex construction.  
           [0006]    A need thus exists for a headrest with more simple mechanism.  
         SUMMARY OF THE INVENTION  
         [0007]    According to an aspect of the present invention, a headrest apparatus for a vehicle seat includes a support portion provided at a seatback of a vehicle seat, a movable portion supported at the support portion for moving forward, a first arm and a second arm being crossed and rotatably connected each other by a rotation axis and supporting the movable portion to the support portion, and a biasing means provided between the support portion and the movable portion for biasing the movable portion forward relative to the support portion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 shows a front view of a headrest according to an embodiment of the present invention.  
         [0010]    [0010]FIG. 2 shows a cross-sectional view taken on line II-II of FIG. 1.  
         [0011]    [0011]FIG. 3 shows a perspective view of an internal mechanism of the headrest according to the embodiment of the present invention.  
         [0012]    [0012]FIG. 4 shows a cross-sectional view showing an arrangement of a coil spring at a non-extended position (original position) of the headrest according to the embodiment of the present invention.  
         [0013]    [0013]FIG. 5 shows a cross-sectional view showing an arrangement of the coil spring at an extended position of the headrest according to the embodiment of the present invention.  
         [0014]    [0014]FIG. 6 shows a cross-sectional view taken on line VI-VI of FIG. 1 at the non-extended position of the headrest according to the embodiment of the present invention.  
         [0015]    [0015]FIG. 7 shows a cross-sectional view taken on line VII-VII of FIG. 1 at the extended position of the headrest according to the embodiment of the present invention.  
         [0016]    [0016]FIG. 8 shows a cross-sectional view taken on line VIII-VIII of FIG. 1 in the non-extended position of the headrest according to the embodiment of the present invention.  
         [0017]    [0017]FIG. 9 shows a cross-sectional view showing an operation of a stopper member according to the embodiment of the present invention.  
         [0018]    [0018]FIG. 10 shows a cross-sectional view taken on line X-X of FIG. 1 in the extended position of the headrest according to the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]    One embodiment of the present invention will be explained with reference to the illustrations of the drawing figures as follows. As shown in FIG. 1, a headrest  1  includes a headrest body  2  and a pair of headrest stays  3 . The headrest stays  3  support the headrest body  2  relative to a seat back of the vehicle seat  17 . First ends of the headrest stays  3  are connected to the headrest body  2  so that the headrest stays  3  support the headrest body  2 . Second ends of the headrest stays  3  are accommodated in the seat back of the vehicle seat  17  to support the headrest body  2 . The height of the headrest body  2  is adjustable by a known constitution arranged between the seat back of the vehicle seat  17  and the headrest stays  3 .  
         [0020]    As shown in FIG. 2, the headrest body  2  includes a support portion  4  and a movable portion  5 . The support portion  4  includes a first bracket  6 . The first bracket  6  is made from a metal plate, or the like. The bracket  6  is fixed, for example, via welding at the headrest stays  3  whose a first end of each support stay  3  is projected from the support portion  4 , and a second end of each support stay  3  is positioned in the support portion  4 . The first bracket  6  may be fixed at the headrest stays  3  via a bolt, a screw cramp, a rivet caulking or the like. As shown in FIG. 3, the first bracket  6  is configured to have two lateral surfaces  6 W formed, for example, by bending two opposite sides of the metal plate, or the like. The first bracket  6  includes approximate U-shape in cross-section. The lateral surfaces have attachment holes  6   a  and  6   b  respectively. The attachment holes  6   b  are vertically elongated along the vertical orientation of the first bracket  6 , that is, the vertical orientation of the headrest body  2 . In the meantime, as shown in FIG. 2, the movable portion  5  includes a second bracket  7 . The second bracket  7  is configured to have lateral surfaces  7 W, for example, by bending a metal plate, or the like, likewise the first bracket  6 . The second bracket  7  is provided at the movable portion  5  and opposing to the first bracket  6 . Each lateral surface  7 W includes attachment holes  7   a ,  7   b . The attachment holes  7   b  are vertically elongated along with vertical orientation of the headrest body  2 , likewise the attachment hole  6   b.    
         [0021]    As shown in FIGS. 2 and 3, the first bracket  6  and the second bracket  7  are connected each other via X links  8  including arms  8   a ,  8   b  and a corresponding pin  9  (a rotation axis). The arm  8   a  and the arm  8   b  are crossed each other to be rotatably connected via the pin  9  serving as a connecting portion.  
         [0022]    As shown in FIG. 3, the X links  8  are connected to the first bracket  6  via rods  10   a ,  10   b . The X links  8  are provided at both ends of the rods  10   a  and  10   b , in other words, at the both lateral surfaces of the first bracket  6 . Each X link  8  is connected each other via the rods  10   a  and  10   b . The rod  10   a  is positioned through an attachment holes &amp; provided at the end portion of the arms  8   a  and its corresponding attachment holes  6   a  provided at the first bracket  6 . The rod  10   b  is positioned through an attachment holes  8   d  provided at the end portion of the arms  8   b  and their corresponding vertically elongated attachment holes  6   b  provided at the first bracket  6 . Thus, the X links  8  and the first bracket  6  are connected. Further, as shown in FIG. 2, likewise the first bracket  6 , a rod  11   a  is positioned through the attachment holes  8   c  provided at the end portion of the arms  8   b  and the corresponding attachment holes  7   a , and a rod  11   b  is positioned through the attachment holes  8   d  provided at the end portion of the arms  8   a  and the corresponding vertically elongated attachment holes  7   b  provided at the second bracket  7 , thus to connect the X links  8  and the second bracket  7 . In other words, the X links  8  are slidably connected to the first bracket  6  and the second bracket  7  via the rod  11   b  in the vertically elongated attachment holes  6   b ,  7   b.    
         [0023]    As shown in FIGS. 3-5, a coil spring  12  serving as biasing means for opening the X-links  8  is provided at the headrest  1 . A leaf spring, a spiral spring, a cylinder apparatus using hydraulic pressure or air pressure may serve as the biasing means for opening the X links  8 . The coil spring  12  includes a coil portion  12   c  and hook portions  12   f  extended from the both end of the coil. At least one end of one of the pins  9  is elongated to be positioned through the coil portion  12   c  and thus to support the coil portion  12   c . Further, each hook portion  12   f  is provided to hook the rods  10   a  and  11   a  respectively against the biasing force of the coil portion  12   c . Accordingly, the coil spring  12  biases the X links  8  for expanding orientation.  
         [0024]    When the headrest  1  is at a non-extended position (original position) without any notice of the pre-crash tendency or shock from the crash, as shown in FIGS. 4 and 6, the X links  8  and the rods  10   a ,  10   b ,  11   a ,  11   b  connected to the X links  8  are closed while provided with the biasing force from the coil spring  12 , and the state of the X links  8  at the non-extended position is maintained by lock members  13   a ,  13   b  between the rods  10   a ,  11   a  so that the movable portion  5  does not extend forward. The lock member  13   a  is rotatably positioned about the rod  11   a  and includes a hook portion  13   f  at a first end of the lock member  13   a . The lock member  13   b  is positioned about the rod  10   a  and selectively engaged with the hook portion  13   f . In case that the hook portion  13   f  engages with the lock member  13   b , the headrest  1  is maintained at the non-extended position. A spring SP (shown in FIG. 6) is provided between the lock member  13   a  and the movable portion  5 . The spring SP biases the lock member  13   a  to engage with the lock member  13   b.    
         [0025]    As shown in FIG. 6, in order to extend the movable portion  5  forward from the non-extended position, a holding by the lock members  13   a ,  13   b  at the non-extended position of the headrest  1  is released. The lock is released by a releasing apparatus  14  attached at the first bracket  6 . As the releasing apparatus  14 , for example, a solenoid apparatus is used. The solenoid apparatus is connected to the sensor for detecting the shock, and operates with the input of electric signal from the sensor. A mechanical sensor including the function of the sensor for detecting the shock may be included for the releasing apparatus  14 .  
         [0026]    The operation of the headrest  1  from the non-extended position to the extended position will be explained as follows.  
         [0027]    The pre-crash tendency or shock from the crash are detected by the sensor, or the like, and transmitted to the releasing apparatus  14  shown in FIG. 6 as an electric signal. Receiving an electric input by the releasing apparatus  14 , a plunger  14   a  of the solenoid apparatus serving as the releasing apparatus  14  moves upward relative to the releasing apparatus  14 . As shown in FIG. 6 and FIG. 7, a second end of the lock member  13   a  always contacts the plunger  14   a  at the non-extended position of the headrest  1 . The lock member  13   a  rotates counterclockwise about the rod  11   a  serving as the attachment portion, when the plunger  14   a  moves upward by the operation of the releasing apparatus  14 . Thus, as shown in FIG. 7, the lock between the lock member  13   a  and  13   b  is released.  
         [0028]    With the release of the lock, as shown in FIG. 4 and FIG. 5, the biasing force from the coil spring  12  is applied to the rods  10   a ,  11   a . Simultaneously, the arms  8   a ,  8   b  of the X links  8  connected to the rods  10   a ,  11   a  rotates about the corresponding pin  9  to extend in the fore-aft direction. Accordingly, the rods  10   b ,  11   b  slide upward along the attachment holes  6   b ,  7   b  respectively provided at the first bracket  6  and the second bracket  7 . When the rods  10   b ,  11   b  reach the upper end of the attachment holes  6   b  and  7   b , the extension of the X links  8 , in other words, the forward extension of the movable portion  5  is completed.  
         [0029]    The movable portion  5  extends forward to support the head of the occupants at the sudden backward swing by an inertial force due to the crash. A stopper member  15  is included at the headrest  1 , as shown in FIGS. 8, 9 and  10  to maintain the forward extended state of the headrest  1  even in the case that the force for returning to the non-extended position is applied to the movable portion  5 . The stopper member  15  is vertically elongated and rotatably positioned about the rod  10   a . The stopper member  15  includes a claw-like hook portion  15   a . The lower end of the stopper member  15  and the first bracket  6  are connected via a spring  16 . By biasing force of the spring  16 , the stopper member  15  is always biased in the direction counterclockwise to rotate about the rod  10   a  serving as the attachment portion. The operation of the stopper member  15  will be explained as follows.  
         [0030]    In case the holding between the lock members  13   a  and  13   b  as shown in FIG. 6 is released at the non-extended position of the headrest  1  shown in FIG. 8, the rod  10   b  positioned through the attachment hole  6   b  provided at the first bracket  6  slides upward along the attachment hole  6   b  along with the extension of the movable portion  5  as shown in FIG. 8 and FIG. 9. In this action, the rod  10   b  slides upward while pushing the hook portion  15   a  formed at the stopper member  15  relatively (in this case the stopper member  15  rotates clockwise) against the restoring force of the spring  16 . When the rod  10   b  exceeds the formed zone of the hook portion  15   a , the stopper member  15  is pulled by the counterclockwise restoring force of the spring  16  about the rod  10   a  serving as the attachment portion. Then as shown in FIG. 10, the movement of the rod  10   b  is restrained by the operation of the hook portion  15   a  formed at the stopper member  15 . Under this condition, the rod  10   b  is structurally locked even if the force likely to return the movable portion  5  to the non-extended position is applied. Thus, because the X links  8  do not close under this state, the movable portion  5  does not return to the non-extended position. Accordingly, extended forward state of the movable portion  5  is maintained, to securely support the head of the occupants. By providing plural claw-like hook portions or a stepped claw-like hook portion, plural extended positions of the movable portion may be available.  
         [0031]    A procedure for the recovery of the movable portion  5  from the extended position as shown in FIG. 10 to non-extended position is explained as follows.  
         [0032]    As shown in FIG. 10, under the condition that the movable portion  5  is positioned at the extended forward position, as the foregoing explanation, the movement of the rod  10   b  is restrained in the attachment hole  6   b  by the stopper member  15 . The stopper member  15  is connected to the first bracket  6  via the spring  16 . In such condition, by pulling, for example, the lower end of the stopper member  15  in the clockwise direction against the biasing force of the spring  16 , the restraint of the movement of the rod  10   b  is released. In this case, the restraint of a rotation of the arms  8   a ,  8   b  about the corresponding pin  9  is released simultaneous with the release of the restraint of the movement of the rod  10   b . Thus, the biasing force of the coil spring  12  affects to extend the X links  8  as shown in FIG. 5. Accordingly, by applying the force exceeding the biasing force, the movable portion  5  extended forward recovers to the non-extended position.  
         [0033]    Further, because the plunger  14   a  cooperating the operation of the releasing apparatus  14  at the non-extended position of the headrest  1  contacts to the releasing apparatus  14  as shown in FIG. 6, the sensitivity for actuating the headrest  1  to the extended position cooperating with the operation of the releasing apparatus  14  is increased effectively.  
         [0034]    The principles, a preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiment disclosed. Further, the embodiment described herein is to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.