Webbing retractor
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a webbing retractor retracting an occupant restraining webbing therein, adapted for use in a seatbelt system for a vehicle. 
     2. Description of the Prior Art 
     In the seatbelt system, the webbing is retracted from one end portion thereof in the webbing retractor and stored therein. 
     The webbing retractor is provided with a locking mechanism in order to put the occupant in a securely restrained situation by the webbing. 
     In such locking mechanism it is common that the webbing is automatically locked to prevent it from being unwound after the occupant dons the webbing. 
     For example, the automatic locking mechanism proposed in U.S. Pat. No. 3,635,420 (Inventor: Romanzi, Jr.) is such constructed that a restraint of the occupant by the webbing and a release thereof from the webbing are detected in accordance with a rotation of a webbing takeup shaft and a pawl engaged with a ratchet wheel fixed to the takeup shaft is controlled by a control plate to be engaged with the ratchet wheel so that the webbing is automatically prevented from being unwound after the occupant wears the webbing. 
     In such conventional webbing retractors, however, means for detecting rotation of the takeup shaft to control a motion of the pawl is made complicated or such means requires many parts therefor, which results in increase of manufacturing costs. 
     SUMMARY OF THE INVENTION 
     In view of the above facts, the present invention has as its object the provision of a webbing retractor having a simple structure and capable of being produced with a reduced manufacturing cost, in which an occupant can be put in a securely restrained situation by an occupant restraining webbing after the occupant dons or wears the webbing. 
     In the webbing retractor according to the present invention, a rotation of the takeup shaft is transmitted to a spring member forced to contact with the takeup shaft by a self spring force of the spring member, and the spring member is made rotatable together with the takeup shaft within a predetermined range by rotation restricting means, the spring member being subjected to a rotation in a direction of a webbing unwinding during an operation of an occupant wearing the webbing so that locking means is put in a released situation where the takeup shaft is rotatable and, thereafter, the spring member being subjected to a rotation in a direction of a webbing winding by resilient means so that the locking means is put in a locked situation where the takeup shaft is prevented from a rotation in the direction of the webbing unwinding. 
     Accordingly, the occupant can surely be put in the restrained situation when the webbing is worn about the occupant. 
     Description will hereinunder be given of embodiments according to the present invention with reference to the drawings attached hereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially and vertically sectional view of a webbing retractor of a first embodiment according to the present invention; 
     FIG. 2 is a left side view of FIG. 1 in which a part of a leg plate and a cover are removed; 
     FIG. 2A is a perspective view of the cover member which was removed for purposes of showing the FIG. 2 depiction. 
     FIG. 3 is an operational view of FIG. 2; 
     FIG. 4 is a second embodiment according to the present invention; and 
     FIG. 5 is a third embodiment according to the present invention: 
    
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     In FIGS. 1 and 2 there is shown a webbing retractor 10 to which the present invention is applied. 
     The webbing retractor 10 is fixed at its base 12 to a vehicle body 16 through mounting bolts 14. Elongated from both side portions of the base 12 are a pair of leg plates 18 and 20 parallel to each other, which rotatably supports portions of an webbing takeup shaft 22 adjacent to both its ends. 
     The takeup shaft 22 is secured at its intermediate portion with one end portion of an occupant restraining webbing 24. One end portion of the takeup shaft 22 is elongated through the leg plate 20 and the takeup shaft 22 is rotationally biased in a direction of a webbing winding, or a webbing retraction, by a spiral spring retracting unit 26, as is biasing means, disposed between the one end portion and the leg plate 20. 
     The takeup shaft 22 is fixed with a pair of ratchet wheels 28 on both sides of the webbing 24, so that the ratchet wheels 28 are rotated together with the takeup shaft 22. Opposed to the ratchet wheels 28 is a pawl 30 supported rotatably by the leg plates 18 and 20. The pawl 30 is received at both its end portions in supporting holes 32 formed on the leg plates 18 and 20, and it stops a webbing unwinding rotation of the takeup shaft 22 when the pawl 30 is engaged with the ratchet wheels 28. 
     Also, the pawl 30 is fixed at its intermediate portion with a diameter sensing arm 34 which is a diameter sensing means, a curved forward end portion of which is caused to abut on an outer peripheral face of a roll of the webbing 24 which has been retracted on the takeup shaft 22. An outer diameter of the roll of webbing 24 is increased in accordance with a winding of the webbing 24 on the takeup shaft 22, and when the webbing 24 is wound on the takeup shaft 22 in a predetermined amount or more, the diameter sensing arm 34 puts the pawl 30 in a released situation from the ratchet wheels 28. 
     On the other hand, the outer diameter of the roll of the webbing 24 is decreased in accordance with an unwinding of the webbing 24, and, when the webbing 24 is unwound from the webbing retractor 10 and the occupant wears the webbing 24, the diameter sensing arm 34 puts the pawl 30 in an engageable situation with the ratchet wheels 28. 
     An end portion 22A of the takeup shaft 22 elongated through the leg plate 18 is clipped by a spring member 36, as shown in FIG. 2. The spring member 36 is formed in forked shape with a pair of legs 38 and 40, end portions of which are curved along an outer periphery of the end portion 22A of the takeup shaft 22. The end portion 22A is clipped by the end portions of the legs 38 and 40 owing to a self spring force of the spring member 36. A projected end portion of the spring member 36, i.e., a connecting portion of the legs 38 and 40, abuts on the pawl 30. 
     The spring member 36 has a spring property in such directions that the leg 38 and 40 approach to each other and, therefore, when the takeup shaft 22 is rotated the spring member 36 is also rotated together with the takeup shaft 22 due to a frictional force occurring therebetween. However, disposed adjacent to both sides of the spring member 36 are a pair of pins 42 and 44, as shown in FIG. 2, whereby the rotation of the spring member 36 is restricted within a range between the pins 42 and 44, and even if the takeup shaft 22 is further rotated the spring member 36 slips relative to the takeup shaft 22. Thus, the pins 42 and 44 constitute rotation restricting means for restricting a rotation of the spring member 36. 
     In this embodiment, the respective pins 42 and 44 are provided on the leg plate 18, but they can be provided on an inside surface of a cover 46 fixed to the leg plate 18 for concealing the spring member 36 as shown in FIG. 2A. 
     On the other hand, the pawl 30 is connected to a coil spring 48, as shown in FIG. 2, whereby the pawl 30 and the diameter sensing arm 34 are biased in a counterclockwise direction in FIG. 2, namely, in such a direction that the pawl 30 is engaged with the ratchet wheels 28. Thus, the pawl 30, the ratchet wheels 28 and the coil spring 48 constitute locking means. In FIG. 2, the pawl 30 is prevented from a rotation in the counterclockwise direction by the diameter sensing arm 34 and the spring member 36. 
     In addition, the spring member 36 is rotated until it is caused to abut on the pin 42, when the takeup shaft 22 is rotated in a direction of a webbing unwinding, as shown in FIG. 2. The situation that the spring member 36 abuts on the pin 42 is defined as a first position of the spring member 36, in which the pawl 30 is released from the ratchet wheels 28. From this situation the spring member 36 is rotated in a direction of a webbing winding and, then, the spring member 36 is caused to abut on the pin 44, as shown in FIG. 3. The situation that the spring member 36 abuts on the pin 44 is defined as a second position of the spring member 36, in which the pawl 30 is put in an engageable situation with the ratchet wheels 28. 
     Description will now be given of operation of the first embodiment thus constructed. 
     The webbing retractor 10 is locked automatically as follows: 
     FIGS. 1 and 2 show a full retracted state of the webbing 24 on the takeup shaft 22. The webbing 24 is unwound from an one end portion (not shown) thereof by the occupant in order to wear the webbing 24 and a tongue plate secured to the one end portion is latched to a buckle device. Thus, the occupant can be restrained with an intermediate portion of the webbing 24. 
     In the full retracted state of the webbing 24 the pawl 30 is pushed down by the diameter sensing arm 34 and it is prevented from rotation in the counterclockwise direction by the projected portion of the spring member 36. Accordingly, even if the webbing 24 is unwound by the occupant so that the diameter of the roll of the webbing which has wound on the takeup shaft 22 is reduced, the pawl 30 is maintained in a released situation from the ratchet wheels 28. 
     Next, after the occupant wears the webbing 24, the webbing 24 is wound on the takeup shaft 22 in a slight amount by the spiral spring retracting unit 26 due to a change of attitude or a breathing of the occupant before the occupant takes a driving situation or just thereafter. In accordance with the rotation of the takeup shaft 22 in the direction of the webbing winding the spring member 36 is also rotated in the counterclockwise direction on FIG. 2 to be moved to a situation shown in FIG. 3, whereby the pawl 30 is released from the abutting situation on the spring member 36. As a result, the pawl 30 is engaged with the ratchet wheels 28 by a biasing force of the coil spring 48, as shown in FIG. 3, so that the takeup shaft 22 is prevented from the rotation in the direction of the webbing unwinding. 
     In this connection, the teeth of each of the ratchet wheels 28 are formed in serration and, therefore, the webbing 24 can be wound on the takeup shaft 22, namely, the takeup shaft 22 can be rotated in the direction of the webbing winding. In consequence, when the occupant or a baggage is fastened by the webbing 24, he or it is automatically put in a securely restrained situation by the webbing 24. 
     A release of the webbing retractor 10 from the stop of the webbing unwinding, i.e., a release of the pawl 30 from the engaged situation with the ratchet wheels 28, is carried out by releasing the tongue plate from the latched situation to the buckle device to cause the spiral spring retracting unit 26 to wind the webbing 24 on the takeup shaft 22 up to the full wound state. That is to say, when the tongue plate is released from the latched situation, the webbing 24 is automatically wound on the takeup shaft 22 by the spiral spring retracting unit 26. Therefore, the diameter sensing arm 34 is rotated in a clockwise direction on FIG. 3 in accordance with an increase of the diameter of a roll of the webbing 24 retracted on the takeup shaft 22 and the pawl 30 is also released from the engaged situation with the ratchet wheels 28. Thereafter, when the webbing 24 is unwound in a slight amount for next use of the seatbelt system, the spring member 36 is returned back to the initial situation shown in FIG. 2. 
     In FIG. 4, there is shown a second embodiment in which a pin 45 opposed to the spring member 36 is disposed between the legs 38 and 40. The pin 45 can be provided on either the leg plate 18 or the cover 46 as well as the above first embodiment. Also, the respective legs 38 and 40 of the spring member 36 are further formed with small curved portions fitting the pin 45. In the situation that one of the legs 38 and 40 of the spring member 36 is abutting on the pin 45, when the takeup shaft 22 is further rotated in such a direction that the one of the legs 38 and 40 abuts on the pin 45, the spring member 36 clipping the end portion 22A of the takeup shaft 22 is subjected to a force in such a direction that a distance between the legs 38 and 40 is increased, so that the frictional force occurring between the end portion 22A of the takeup shaft 22 and the spring member 36 is reduced. As a result, a winding or unwinding of the webbing 24 can smoothly be conducted even in such a situation that one of the legs 38 and 40 is abutting on the pin 45. In the other functions and effects the second embodiment is the substantially same as the first embodiment. 
     In FIG. 5, there is shown a third embodiment in which the respective legs 38 and 40 of the spring member 36 are elongated over the end portion 22A of the takeup shaft 22 and the pin 45 which is one of the rotation restricting means is disposed between the elongated portions of the leg 38 and 40. In this embodiment, when the takeup shaft is further rotated from such a situation that one of the legs 38 and 40 is abutting on the pin 45, the spring member 36 is forced in a direction that a distance between the legs 38 and 40 is increased, so that a frictional force between the end portion 22A and the spring member 36 is reduced, as well as the second embodiment. 
     In all the above embodiments, the pawl 30 is disposed under the ratchet wheels 28, but it can be disposed above the ratchet wheels 28 so as to be engaged with the ratchet wheel 28 by the self-weight of the pawl 30. 
     Various changes can be made to the forms of the invention herein shown and described without departing from the spirit of the invention or the scope of the following claims.