Abstract:
The invention relates to a safety belt apparatus, in particular for motor vehicles, comprising a safety belt ( 11 ) which is connected on the one hand via a belt lock ( 12 ) to the vehicle body ( 13 ) and on the other hand to a belt winder ( 14 ) which is attached to the vehicle body ( 13 ), and which has a belt roller ( 15 ) which is rotatable about a transverse axis ( 16 ) and onto which the belt ( 11 ) is wound up to a greater or lesser extent, which is stressed by a spring mechanism ( 17 ) in the belt roll-up direction and is connected to a belt tautener ( 18 ) as well as to an unwind blocking apparatus ( 19 ) which blocks the further drawing out of the belt in the attempt of a rapid belt drawing out and/or in accident caused accelerations at the latest after a limited further rotation of the belt roller ( 15 ), with a coupling ( 20 ) consisting of an input part ( 22 ), an output part ( 24 ) and coupling members ( 25 ) which are active between them being placed between the belt tautener ( 18 ) and the belt roller ( 15 ), which coupling ( 20 ) is normally open and closes at the beginning of the rotation of the belt tautener ( 18 ) after a triggering in order that the belt roller ( 15 ) can be abruptly driven in the wind-up direction by the belt tautener ( 18 ). The invention consists in that the coupling ( 20 ) can be automatically disengaged when the torque which acts on the belt roller ( 15 ) in the wind-up direction exceeds the torque which is exerted by the belt tautener ( 18 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a safety belt apparatus in particular for motor vehicles comprising a safety belt and a belt tautener. The safety belt can be a two-point or three-point safety belt, with one belt part being led from the vehicle body via a lock to a belt winder and comprising a connection. element extending from the releaseable lock part to the body of the vehicle. 
     The purpose of the belt winder is to exert a force on the belt roller in the wind up direction by means of a spring mechanism in order that in the unbuckled state the safety belt is largely wound in and does not lie too loosely in contact on the passenger. The purpose of the unwind blocking apparatus is to stop the further drawing out of the belt when an attempt is made to draw it out rapidly or in accident caused accelerations after a slight further rotation of the belt roller at the latest. The belt tautener is provided at the belt winder in order to abruptly rotate the belt roller by so many rotations in the wind up direction in an accident caused acceleration that the safety belt, which at first lies loosely at the vehicle passenger, is tautened in such a manner that the passenger does not fall in into the loosely fastened belt and injure himself in doing so. 
     Belt tauteners which are particularly suitable for the purposes of the invention are known from EP 581 288 B1 and U.S. Pat. No. 5,553,803. 
     Whereas the belt tautener is normally separated from the belt roller by a coupling, it is abruptly coupled to the belt roller in the event of a triggering in order to be able to initiate the belt tautening. A problem exists in that after the completion of the belt tautening it should be possible for the belt to be drawn out unhindered from the used belt tautener so that the driver can more easily free himself from the belt after the accident. In addition, in the case where the belt roller can still rotate somewhat relative to the blocked unwind blocking apparatus when the belt is drawn out, it is important to maintain this limited rotational movement of the belt roller as it damps the forward movement of the passenger. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a safety belt apparatus with a belt tautener in which the triggered and operated belt tautener no longer exerts a disadvantageous influence on the desired movements of the belt roller after a triggering event and the subsequent tautening of the belt. 
     An idea of the invention is that the belt roller, which is rotationally fixedly coupled in the wind-up direction to the belt tautener shaft during the belt tautening, is decoupled from the belt tautener after completion of the belt tautening. The decoupling occurs when the draw out force on the belt exceeds the tautener force so that a definite draw-out rotational movement of the belt roller, which is desirable after an accident, is not hindered by the still working or already expended belt tautener. 
     It is advantageously provided that a reversal of the rotational direction of the belt roller and/or drive of the belt tautener disengages the coupling. 
     The coupling drive affects that the closing or the engaging respectively of the coupling takes place through the rotation of the belt tautener immediately after a triggering. 
     The conducting-in member ensures a particularly operationally reliable, unobjectionable actuation of the coupling. 
     Both the disc and also the coupling members and the coupling ring can be designed to be very flat and thus to require little space in the axial direction. 
     The ratchet wheel ensures that the conducting-in and conducting-out abutments rotate with the coupling during a triggering, but are however held firmly at the beginning and end of a triggering so that in connection with the rotation of the disc in the one or the other direction they can reliably carry out the conducting-in and conducting-out, respectively, of the coupling members. 
     The invention provides a constructionally favorable and very operationally reliable measure to enable a rotation of the ratchet gear in the wind-up direction against a limited resistance and to completely suppress a backwards rotating of the ratchet gear. 
     Particularly important are the rotational spring elements which are effective in the framework of the rotational play. 
     The coupling ring which represents the output member of the coupling is expediently integrated into the belt roller. 
     The cut-out is expediently covered over by the coupling drive, which is preferably formed by the ratchet wheel and the components which are arranged at it. 
     It is particularly advantageous when a limited rotational play, which is in particular enabled by a torsional bar, is present between the unwind blocking apparatus and the belt roller and which enables the belt roller to make several rotations, in particular three to four rotations, in the event of an accident caused drawing force at the safety belt in order that the falling forwards of the passenger into an inflated airbag is preferably damped accordingly. The torsion bar is thus plastically, that is, lastingly deformed during the rotation under accident caused forces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in the following with reference to the drawings; shown in these are: 
     FIG. 1 a schematic vertical sectional view of the belt winder of a safety belt in accordance with the invention, with the safety belt, the lock and the draw member being merely schematically indicated in chain-dotted lines, 
     FIG. 2 a perspective exploded view of the essential components of a belt winder in accordance with the invention, 
     FIG. 3 an axial plan view of a preferred embodiment of the coupling in accordance with the invention and of the coupling drive which is arranged axially behind it, 
     FIG. 4 a scaled down side view of the object in FIG. 3 without the inner tooth crown and coupling ring, with the coupling members being stressed in disengagement position as in FIG. 3, 
     FIG. 5 a view as in FIG. 4, with however the outer teeth of the ratchet wheel being reproduced in the position which is radially inwardly pressed through the inner tooth crown of the housing and the coupling members being pressed into the engagement position of the coupling, 
     FIG. 6 a view of the objects of FIGS. 4,  5  from the opposite side, with the outer teeth being located in an intermediate position between the positions in accordance with FIGS. 4 and 5 and 
     FIG. 7 a plan view of the object in FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     In accordance with FIG. 1 a three-point safety belt  11  is on the one hand partly rolled up onto a belt roller  15  of a belt winder  14  which is secured at the vehicle body  13  and is led to the vehicle body  13  on the other hand via a belt lock  12  which is merely indicated in chain-dotted lines. The releasable belt lock part  12 ′ is likewise connected to the vehicle body via a draw member  11 ′. 
     The belt roller  15  is journalled at the vehicle-fixed housing  40  so as to be rotatable about a transverse axis  16 . It has a cavity  36  which is open at the left and is closed off at the right by a front wall  38  and into which a torsion bar  37  extends from a ratchet wheel  41  of an unwind blocking apparatus  19  (which is provided at the left end side of the belt roller  15  up to the front wall  38 ) to a position close to a right end side of the belt roller  15 ; the right end of the torsion bar  37  is rotationally fixedly connected to the front wall  38  (which forms an integral constituent part of the belt roller  15 ). The ratchet wheel  41  cooperates with one or more pawls  42  which is or are, either in an attempt at a rapid drawing out of the belt  11  or in accident caused accelerations of the vehicle, brought through suitable control means  43  into such an engagement with the ratchet wheel  41  that an otherwise possible rotation of the ratchet wheel  41  in the belt draw-out direction is prevented. 
     Adjacent to the ratchet wheel  41  there is a spring mechanism  17  which is arranged on the one hand at the housing  40  and on the other hand at the ratchet wheel  41  in such a manner that a torque in the wind-up direction of the safety belt  11  is exerted on the torsion bar  37  and thus on the belt roller  15 . 
     A belt tautener  18  is located at the housing  40  at the right end side of the belt roller  15 ; the belt tautener  18  facing away from the spring mechanism  17  and the unwind blocking apparatus  19 . The belt tautener  18  is preferably pyrotechnically triggered and operated in the event of accident caused accelerations and exerts a torque which acts in the wind-up direction of the safety belt  11  on its output shaft  21  (which may be designed as a polygonal sleeve). 
     The shaft  21  is provided with a coaxial bore of approximately triangular cross-section which is open in the direction towards the belt roller  15  and in which an axle stump  44  (which has a complementary cross-section (FIGS. 1,  6 ,  7 ) and which extends from the right end of the belt roller  15 ) of a coupling  20  is rotationally fixedly engaged. In accordance with FIG. 1 the axle stump  44  is also designed to include a hollow cavity of circular cross-section and to open in the direction of the belt roller  15 . The shaft end  45  of the belt roller  15  engages rotationally and extends from an end pin  45 ′ of small diameter located in a bearing socket  53  which is provided in the cavity of circular cross-section. 
     In accordance with FIGS. 1,  6  and  7  a ratchet wheel  28  with a significantly greater outer diameter than the coupling  20  sits on the axle stump  44  on the side facing away from the coupling  20 . The ratchet wheel  28  and various components arranged thereon form a coupling drive  34 . 
     In accordance with FIGS. 1 and 3 to  7 , the coupling  20  consists of a circular disc  22  which is secured at the belt-roller-side end of the axle stump  44 . The circular disc  22  has three cut-outs  23  therein each of which has a partly circular radial inner end. The cut-outs  23  are distributed over the disc&#39;s periphery and engage coupling members  25 . The coupling members  25  are designed as claws (having a shape which is in particular visible in FIG. 3) and are arranged in such a manner that they can each pivot, to a limited extent, about respective axes  32 ; the axes  32  are parallel to the belt roller axis  16 . The coupling members  25  are designed radially inwardly analogously to the cut-outs  23 . 
     Radially outwardly the coupling members  25  are provided with clamping teeth  33  which cooperate with the inner wall of a surrounding coupling ring  24  which projects axially (as shown in FIG. 1) from the right side of the belt roller  15  (i.e. the side facing the belt tautener  18 ). It is preferable that the coupling ring  24  be integral with the right side of the belt roller  15 . The ratchet wheel  28  is also substantially designed (in accordance with FIGS. 1 and 7) as a flat circle-like disc which lies in contact at the side of the disc  22  of the coupling  20  which faces away from the belt roller  15 . 
     As shown in FIGS. 3 to  5 , three abutment carrying elements  46  project from the surface of the ratchet wheel  28  facing the belt roller  15  and toward the belt roller  15 . The abutment carrying elements  46  are designed to have substantially the shape of circular arcs. In addition, the abutment carrying elements  46  extend at an angle relative to the axis  16  such that between every two abutment carrying elements  46  there remains a gap  47 ; the coupling members  25  fit with the gaps  47  with peripheral clearance. The two ends of each abutment carrying element  46  form conducting-in and conducting-out abutments  26 ,  27  which can come selectively into engagement with the radially outer regions of the coupling members  25 . Whereas the abutment carrying elements  46  are designed outwardly to be in the shape of circular arcs which are substantially concentric to the transverse axis  16 , they have inwardly a retraction  54  which is located on the side of the conducting-out abutments  27 . Through the retractions  54 , a space saving accommodation of the coupling members  25  in the disc  22  is created. 
     On its outer periphery, the ratchet wheel  28  has outer teeth  29 ; the teeth  29  are pivotal about an axis parallel to the transverse axis  16 . The teeth  29  engage depressions  48  between inner teeth  31  of an inner tooth crown  30 ; the inner tooth crown  30  being formed at the housing  40 . The number of the inner teeth  31  is twice as great as that of the outer teeth  29  so that an outer tooth  29  of the ratchet wheel  28  engages only in every second tooth depression  48  of the inner tooth crown  30 . 
     The ratchet wheel  28  is formed radially inwardly from the outer teeth  29  and is journalled on the axle stump  44 . In accordance with FIG. 6, the ratchet wheel  28  consists of an outer part  28 ′ (which has substantially the shape of a circular disc), an inner part  28 ″ (which sits rotationally fixedly on the axle stump  44  and which forms part of an output drive of the belt tautener  18 ), and spring elements  28 ′″ (which extend between the outer and inner parts  28 ′,  28 ″). Three spring elements  28 ′″ are distributed over the periphery of the ratchet wheel  28 . 
     Starting from the inner part  28 ″, each of the spring elements  28 ′″ (which are integrally connected to the outer and inner parts  28 ′,  28 ″): (a) first extends substantially radially outwardly into a corresponding cut-out  49  of the outer part  28 ′, then (b) bends around inwardly by somewhat less than 180° in the tautening direction, and (c) finally merges via an inclined web  39  and a further curvature region  55  into a web  50  which projects radially inwardly from the outer part  28 ′ into the cut-out  49 . 
     The spring constant of the spring elements  28 ′″ is chosen in comparison with the spring constant of the outer teeth  29  such that, when the axle stump  44  is rotated in the direction of the arrow  51  in FIG. 6, at first only the inner part  28 ″ of the ratchet wheel  28  rotates, while partly pressing together the spring elements  28 ′″ in the manner of an accordion, whereas the outer part  28 ′ is held firmly against a rotation through mass inertia and the outer teeth  29  which engage into the tooth depressions  48  (FIG.  3 ). After the spring elements  28 ″ are deformed to such an extent that a predetermined torque is exerted on the outer part  28 ′, the outer teeth  29  unlatch from the latching depressions  48  and rotate into the next tooth depression. 
     It should be emphasized that the abutment carrying elements  46  are located adjacent the outer part  28 ′ of the ratchet gear. Accordingly, during the first phase of the rotational movement of the axle stump  44  (up to the partial pressing together of the spring elements  28 ′″), the disc  22  of the coupling  20  rotates in the direction of the arrow  51  in FIG. 3 whereas the outer part  28 ′ of the ratchet wheel  28  and the carrying abutments  46  at first remain stationary. During this phase of the movement the outer regions of the coupling members  25  approach the conducting-in abutments  26  and finally strike against the latter (FIG.  5 ). In a further relative rotation between the disc  22  and the outer part  28 ′, the coupling members  25  pivot about their axes  32  (in the direction towards the inner wall of the coupling ring  24 ) until the clamping teeth  33  stand in firm engagement with the coupling ring  24 . In a further rotation of the axle stump  44 , the coupling members  25  force the coupling ring  24  and thus the belt roller  15  in a rotational movement in the direction of the arrow  51 . 
     Since the outer part  28 ′ participates in the rotational movement of the axle stump  44  when the spring elements  28 ′″ are partially pressed together, the coupling disc  22  and the ratchet wheel  28  rotate together (as the coupling members  25  are in engagement with the coupling ring  24 ) until a predetermined belt force has been reached or the pyrotechnic charge of the belt tautener  18  has been consumed. 
     The coupling  20  thus remains engaged until the torque which is exerted on the belt roller  15  by the belt draw force (which may be produced, for example, by a passenger falling into the belt) exceeds the contrary torque of the belt tautener  18 . When the torque exerted on the belt roller  15  exceeds the contrary torque, the coupling ring  24 , while overcoming the torsion bar  37 , forces the disc  22  in the belt draw-out direction via the coupling members  25 . At the same time, the coupling members  25  are released from the conducting-in abutments  26  (while the ratchet wheel  28  remains stationary) and enter into engagement with the conducting-out abutments  27 , thereby causing a disengagement of the coupling  20 . At this time, the belt can still be drawn out, to a limited extent, under the braking influence of the unwind blocking apparatus  19  and the torsion bar  37 . 
     As long as no force is exerted on the belt during the operation of the belt tautener  18 , the torque on the axle stump  44  decreases and finally vanishes completely. Thereupon, the spring elements  28 ′″, which are at first pressed together, can relax. In addition, with the outer part  28 ′ being held firmly against rotation counter to the direction of the arrow  51  (through latching in of the outer teeth  29  into the tooth depressions  48  (FIG.  3 )), the inner part  28 ″ in FIG. 6 can rotate counter to the direction of the arrow  51  by an amount such that the coupling members  25  are released from the conducting-in abutments  26  and then come into contact with the peripherally oppositely lying conducting-out abutments  27  (FIGS. 3,  4 ). Moreover, the coupling members  25  are pivoted about their axes  32  (clockwise in FIG. 3) in such a manner that the clamping teeth  33 . come out of engagement with the inner wall of the coupling ring  24 . At this time, the belt roller  15  can be rotated by the run out belt tautener  18  without hindrance as permitted by the spring mechanism  17  (FIG.  1 ), the unwind blocking apparatus  19 , the torsion bar  37  and the draw forces which are exerted on the safety belt  11 . 
     The coupling  20  is accommodated in a front cut-out  35  of the belt roller  15  and is covered over according to FIG. 3 in accordance with FIGS. 1,  2  and  7  by a cover plate  52  on the side facing the belt roller  15 . 
     The functioning of the safety belt apparatus described is as follows: 
     As long as the belt tautener  18  has not been triggered, the coupling members  25  are in the disengaged position in accordance with FIGS. 3 and 4. The belt roller  15  can be rotated without hindrance or held fast depending on the influence of the spring mechanism  17 , the unwind blocking apparatus  19 , and the draw forces exerted on the safety belt  11 . 
     If, however, the bet tautener  18  is triggered in an accident, then at first only the inner part  28 ″ (FIG. 6) of the ratchet wheel  28  and the disc  22  of the coupling  20  (FIG. 3) are rotated in the direction of the arrow  51 , whereas the outer part  28 ′ remains stationary. At this time, the (coupling members  25  abut the coupling-in abutments  26  and leave the disengaged position (in accordance with FIGS. 3 and 4) and enter into the engaged position (in accordance with FIG. 5) in which the coupling members  25  grip the inner wall of the coupling ring  24  with their clamping teeth  33  in a force transmitting manner. The coupling  20  is then moved by the coupling drive  34 . 
     On further rotation of the belt tautener  18 , the coupling members  25  force the coupling ring  24  and thus the belt roller  15  in the wind-up direction. As soon as the spring elements  28 ′″ (FIG. 6) have been pressed together to such an extent that they can transmit a sufficient torque to the outer part  28 ′, the outer part  28 ′ of the ratchet wheel  28  is forced in a rotational movement in which the outer teeth  29  successively snap into the consecutive tooth depressions  48  of the inner tooth crown  30 . 
     During the accident-caused tautening of the belt, the passenger (who is held by the belt) falls into the belt and exerts a correspondingly increasing draw force on the latter. This draw force creates a torque in the unwinding direction at the belt roller  15 . As soon as this torque exceeds the counter-torque which is produced by the belt tautener  18 , the coupling ring  24  rotates synchronously by an amount in the unwinding direction along with the coupling members  25 , the disc  20  and the inner part  28 ″. At the same time, the spring elements  28 ′″ increasingly relax and the conducting-in member  28 ′ remain stationary until the coupling members  25  abut the conducting-out abutments  27  and are released from the coupling ring  24 . 
     Since in an accident the unwind blocking apparatus  19  enters into the blocking position, the reversal of the direction of rotation of the belt roller  15  is possible only because the torsion bar  37  (which allows a definite relative rotational play) is located between it and the unwind blocking apparatus  19 . 
     The coupling  20  is then disengaged, and the passenger who has fallen into the belt is caught gently while the torsion bar  37  continues to twist. At the same time, the passenger normally falls into an inflated airbag. 
     Should for some reason no noticeable draw force have arisen at the belt when the pyrotechnic charge of the belt tautener  18  is exhausted, the spring elements  28 ′″ relax in the position seen in FIG. 6 as soon as the torque which is exerted by the belt tautener  18  is less than the restoring torque which resulted from the spring element  28 ′″. When this occurs, the inner part  28 ″ (and with it the axle stump  44 ) rotates counter to the direction of the arrow  51 . In addition, the coupling members  25  leave the engagement position (in accordance with FIG. 5) and enter the disengaged position in accordance with (FIGS. 3,  4 ). As a result, the belt roller  15  is no longer subject to the influences of the run out belt tautener  18 , which under appropriate circumstances hinder the rotational movement. 
     A substantial advantage of the present invention is that through the release of the coupling  20  during the tautening by the belt tautener  18 , the belt force plot is approximately constant, after a relatively uniform increase at the start. In addition, the belt force plot has no excessive peak value. 
     A further advantage consists in that the coupling also opens under a load without problem. In this the ratchet wheel fulfills a multiple function. 
     To the disengaging of the coupling  20  a rotational play of approximately 15° is to be provided between the unwind blocking apparatus  19  and the belt roller  15 , i.e. the belt roller  15  can rotate by this angle in the drawing-out direction relative to the blocking unwind blocking apparatus  19  under the influence of a specific belt draw force.