Abstract:
In an emergency locking seat belt retractor including a housing, a belt take-up shaft rotatably disposed in the housing for winding thereon a seat belt, a return spring for biasing the belt take-up shaft to rotate in a direction to retract the belt, a locking device for locking, when actuated, the belt take-up shaft against rotation in a direction to withdraw the seat belt, a shock sensing device for sensing a predetermined degree of shock applied thereto, and a transmitting device for actuating the locking device when the shock sensing device senses the predetermined degree of shock, the shock sensing device being pivotally connected to the housing by means of a pivot bolt.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to an emergency locking seat belt retractor of a motor vehicle which instantly locks the seat belt when sensing a predetermined degree of shock applied thereto, and more particularly to an emergency locking seat belt retractor of a so-called deceleration sensing type which instantly inhibits the withdrawal of the seat belt upon sensing a predetermined degree of deceleration of the vehicle as in a case of vehicle collision. 
     2. Description of the Prior Art 
     Hitherto, as emergency locking seat belt retractors, there have been proposed a deceleration sensing type and a belt movement sensing type. The former is one which locks the belt upon sensing a deceleration of the vehicle, while the latter is one which locks the belt upon sensing a rapid withdrawing movement of the belt. It is generally known that the former, that is the deceleration sensing type retractor, has a quicker locking operation than the latter. 
     In the deceleration sensing type retractor, a so-called &#34;G-sensor&#34; is employed which is arranged to be vertically positioned. However, in the conventional deceleration sensing type retractor, it is usual that the G-sensor is fixedly set in the retractor proper. Thus, when mounting the retractor to the vehicle, the retractor must be mounted so that the G-sensor is vertically positioned. However, as is known, the size and/or dimensions of the mounting space provided in the vehicle for mounting thereon the retractor varies depending on the type of the vehicle, so that it is necessary to produce a specially designed seat belt retractor for each vehicle. Of course, this increases the cost of production of the retractor. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an emergency locking seat belt retractor which is adopted to be used in various kinds of motor vehicles. 
     According to the present invention, there is provided an emergency locking seat belt retractor which comprises a housing, a belt take-up shaft rotatably disposed in the housing for winding thereon a seat belt; biasing means for biasing the belt take-up shaft to rotate about its axis in a direction to retract the seat belt, a locking device for locking, when actuated, the belt take-up shaft against rotation in a direction to withdraw the seat belt from the shaft, a shock sensing device for sensing a predetermined degree of shock applied thereto, and a transmitting device for actuating the locking device when the shock sensing device senses the predetermined degree of shock, wherein the shock sensing device is pivotally connected to the housing so that the shock sensing device functions properly regardless of the mounting orientation of the retractor housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become clear from the following description when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is front view of an emergency locking seat belt retractor according to the present invention; 
     FIG. 2 is a partially sectioned side view of the energency locking seat belt retractor of the invention; and 
     FIG. 3 is an exploded view of the emergency locking seat belt retractor of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 to 3, especially FIG. 3, there is shown an emergency locking seat belt retractor 10 according to the present invention. The retractor 10 comprises a housing 12 including an elongate base portion 12a and two side walls 12b and 12c. A belt take-up shaft 14 is spanned and supported by the side walls 12b and 12c in a manner to be rotatable about the axis thereof. As is clearly shown by FIG. 3, the right hand end of the shaft 14 is reduced in diameter to form a crescent portion 14a which is engaged with a locking device 22 which will be described hereinafter. A seat belt 16 is wound on the shaft 14 with its one end secured to the shaft 14, and a return spring 18 is mounted on the side wall 12c of the housing 12 to bias the belt take-up shaft 14 to rotate in a direction to retract the belt 16. As is shown by FIG. 1, the return spring 18 is housed in a cover 20 secured to the side wall 12c of the housing 12. 
     A locking device 22 is arranged to inhibit the withdrawal of the belt 16 when operated. As is clearly shown in FIG. 3, the locking device 22 comprises a main ratchet wheel 24 and an auxiliary ratchet wheel 26 which are coaxially and fixedly disposed on the crescent portion 14a of the belt take-up shaft 14 to be rotated therewith. A clutch wheel 28 is coaxially and rotatably disposed on the crescent portion 14a of the shaft 14 so that the clutch wheel 28 can rotate about its axis relative to the shaft 14. As is seen in FIG. 2, a C-shaped fastener 30 is fixed to the crescent portion 14a for preventing dislocation of the wheels 24, 26 and 28 on the shaft 14. A locking pawl 32 is pivotally disposed on a stud 34a mounted on the side wall 12b of the housing 12. In the embodiment disclosed, the stud 34a is shown to be a part of a strut 34 of the housing 12. The locking pawl 32 has a detent 32a which is engageable with the teeth of the main ratchet wheel 24 so that when the detent 32a is meshingly engaged with one of the teeth of the main ratchet wheel 24, the withdrawing movement of the seat belt 16 is inhibited. It should be noted however that by the nature of the ratchet wheel 24 having the inclined teeth, the retracting movement of the belt take up shaft 14 is permitted even when the detent 32a of the pawl member 32 is in engagement with the teeth of the ratchet wheel 24. The locking pawl 32 further has a small projection 32b which is loosely received in a recess 28a formed in the clutch wheel 28 so that the pivotal movement of the clutch wheel 28 induces the simultaneous pivotal but reversed movement of the locking pawl 32 about the stud 34a. A spring 36 is arranged between the locking pawl 32 and the clutch wheel 28 for biasing the locking pawl 32 in a direction to disengage from the teeth of the main ratchet wheel 24. A rod-shaped slider 38 is axially slidably received in a tube 40 which is formed on the clutch wheel 28. A spring 42 is disposed in the tube 40 for biasing the slider 38 radially outwardly. The slider 38 is provided with a pawl portion 38a which is meshingly engaged with one of the teeth of the auxiliary ratchet wheel 26 when the slider 38 takes a predetermined position. With the construction mentioned above, it will be noted that when the pawl portion 38a of the slider 38 is kept engaged with one tooth of the auxiliary ratchet wheel 26, a slight rotation of the belt take-up shaft 14 in the belt withdrawing direction brings about a slight rotation of the clutch wheel 28 in the corresponding direction by the assist of the auxiliary ratchet wheel 26, thereby causing the locking pawl 32 to swing in a direction to engage with the main ratchet wheel 24. Thus, the belt take-up shaft 14 becomes locked against rotation in the belt withdrawing direction. 
     A link 44 is supported between the side walls 12b and 12c of the housing 12 by a pin 46 so that the link 44 is rotatable about the pin 46. A spacer 48 adjoins the link 44. As is best shown in FIG. 3, the link 44 is provided at its one end with a straight arm 44a and at the other end with a crank arm 44b. As will be seen from FIG. 1 or 2, the crank arm 44b is so arranged as to support the head portion of the slider 38 so that when the link 44 swings in a given direction about the axis thereof, the crank arm 44b pushes up the slider 38 against the biasing force of the spring 42 into the predetermined position where the pawl portion 38a of the slider 38 is in engagement with the auxiliary ratchet wheel 26. 
     A deceleration sensing device is generally designated by numeral 50. The device 50 comprises a pendulum plate 52 having at its upper portion a threaded opening 52a. The pendulum plate 52 is swingably connected to the elongate base portion 12a of the housing 12 by means of a bolt 54 which passes through an opening 12d of the housing base portion 12a and is screwed to the threaded opening 52a of the pendulum plate 52. For achieving smooth swinging movement of the pendulum plate 52, a bush 56 is fitted to the opening 12d. A generally U-shaped weight 58 is bolted to the outer side of the pendulum plate 52, and a sensor base 60 is also secured to the pendulum plate 52 in a manner to be embraced by the U-shaped weight 58. As is clearly shown in FIG. 2, the sensor base 60 is formed with a blind hole 60a in which a spinning top-shaped sensor weight 62 is set. As will become clear as the description proceeds, the sensor weight 62 is so arranged that in a normal condition, it is vertical as illustrated in FIG. 2, but upo receiving a predetermined inertia force, it is inclined. The sensor weight 62 is formed at its upper surface with a conical recess 62a. A wing element 64 having two angularly spaced wing portions 64a and 64b is pivotally supported by a pin 66 between two spaced projections (no numerals) formed on the sensor base 60. As is best shown in FIG. 2, the wing portion 64a is formed with a semispherical boss 64c. The arrangement of the wing element 64 is so made that the semispherical boss 64c and the wing portion 64b are in contact with the center of the conical recess 62a of the sensor weight 62 and the afore-mentioned straight arm 44a of the link 44, respectively. As will be understood from a phantom line &#34;A&#34; in FIG. 2, the wing portion 64b contacts the straight arm 44a at a point in alignment with the rotating axis of the pendulum plate 52, that is, at a point in alignment with the axis of the bolt 54. With this measure, the contact engagement between the wing portion 64b and the straight arm 44a is constantly kept irrespective of any angular positions which the pendulum plate 52 takes relative to the elongate base portion 12a of the housing 12. 
     Upon mounting the retractor 10 thus constructed to a vehicle, for example, to a side portion of a passenger seat, one bolt (not shown) is used for achieving pivotal movement of the retractor 10 relative to the vehicle body. For this purpose, the elongate base portion 12a of the housing 12 is formed with a circular opening 12e through which the bolt passes. In the invention, however, it is important to arrange the retractor 10 in such a manner that the major surface of the elongate base portion 12a of the housing 12 is parallel with a vertical plane, so that the swingable movement of the retractor 10 about the pivot bolt is made by permitting the major surface of the base portion 12a to move parallel to the vertical plane. Now, it is to be noted that the pendulum unit which includes the plate 52, the weight 58 and the sensor base 60 is compelled to hang down vertically irrespective of the setting angle of the housing 12 relative to the vehicle body. 
     Operation will be described in the following with reference to FIG. 2. For easy understanding of the operation, the explanation will commence with respect to a condition wherein the vehicle is cruising and a passenger on a seat uses the seat belt 16. In this condition, the seat belt retractor 10 of the invention takes the position illustrated by FIG. 2 in which the sensor weight 62 is substantially vertical causing the wing element 64, the link 44 and the slider 38 to take their rest or inoperative positions. With the slider 38 taking its rest position, the pawl portion 38a of the slider 38 is kept disengaged from the auxiliary ratchet wheel 26, so that the rotation of the auxiliary ratchet wheel 26 induced by withdrawal of the seat belt 16 from the housing 12 does not induce the rotation of the clutch wheel 28. Thus, the locking pawl 32 does not engage the main ratchet wheel 24 because of the reason mentioned hereinbefore. Thus, in this normal condition, the seat belt 16 is freely withdrawable from the retractor 10. 
     When the vehicle is subjected to a vehicle collision, the sensor weight 62 is instantly inclined making the lower center portion thereof act as a pivot before the pendulum unit starts to swing forward or rearward. With the sensor weight 62 now inclined, the wing portion 64a of the wing element 64 is moved up thereby turning the wing element 64 counterclockwise in FIG. 2 and thus turning the link 44 clockwise. With the link 44 thus turned, the crank arm 44b of the link 44 pushes up the slider 38 to the position where the pawl portion 38a is in engagement with the teeth of the auxiliary ratchet wheel 26. Thus, the slight withdrawal of the seat belt 16 which inevitably occurs due to forward inclination of the seat belt wearer brings about a slight rotation of the clutch wheel 28 in a counterclockwise direction in FIG. 2, so that locking pawl 32 turns clockwise bringing the detent 32a into engagement with one of the teeth of the main clutch wheel 24. Thus, the belt take-up shaft 14 is locked against rotation in the belt withdrawing direction. Thus, the passanger is safely restrained by the belt. 
     According to the present invention, the following advantages are obtained: 
     (a) Since the deceleration sensing device 50 is arranged to pivotally hang down from the retractor housing 12 by its own weight, the mounting of the retractor 10 to the vehicle body can be arbitrarily made without considering the setting angle of the retractor 10 relative to the vehicle body. This means that the retractor according to the present invention is widely applicable to various kinds of motor vehicles. Further, since the setting angle of the retractor 10 is not limited in the invention, one kind of a retractor can be commonly applicable to both a leftside seat and a rightside seat which have different retractor mounting spaces. These features produce a remarkably low production cost of the retractor. 
     (b) Since the retractor 10 is pivotally connected to the vehicle body by means of the pivot bolt (not shown) passing through the opening 12e of the housing 12, the retractor 10 can swing in accordance with the movement of the seat belt wearer. This enhances the comfort of the wearer.