Abstract:
A belt retractor for a vehicular seat belt system comprises a belt reel taking up a seat belt, a belt tensioning mechanism capable of biasing the belt reel in a winding direction of the seat-belt, and a sensor capable of triggering the belt tensioning mechanism and provided with a safety device translatable by installation of the belt retractor in a vehicle from a secured condition in which the sensor is blocked, into a released condition in which the sensor is ready to trigger. The safety device includes a sensor blocking element which is movable between a blocking position in which the sensor is blocked, and a release position in which the sensor is ready to trigger, and includes a transport locking element and a sensing element. The sensing element senses a diameter of a coil of the seat belt on the belt reel and allows a movement of the sensor blocking element into the release position only when the diameter is below a predetermined value. The transport locking element is movable between a locked position and a release position. A spring is provided which biases the transport locking element into the release position, and a spring is provided which biases the sensor blocking element into the release position. The transport locking element comprises a retaining section which in the locked position engages an arresting section of the sensor blocking element and maintains it in the blocking position.

Description:
TECHNICAL FIELD 
     The invention relates to a belt retractor for a vehicular seat belt system. 
     BACKGROUND OF THE INVENTION 
     A belt retractor as is known for example from European patent application 0 456 853 comprises a belt reel taking up the seat belt, a belt tensioning mechanism capable of biasing the belt reel in the winding direction of the seat belt, and a sensor capable of triggering the belt tensioning mechanism and is provided with a safety device translatable by installation of the belt retractor in a vehicle from a secured condition, in which the sensor is blocked, into a released condition in which the sensor is ready to trigger, the safety device including a sensor blocking element which is movable between a blocking position in which the sensor is blocked and a release position in which the sensor is ready to trigger. 
     A belt tensioning mechanism being triggered by a sensor when required serves to eliminate belt slack from the seat belt system by rotating the belt reel in the winding direction of the seat belt so that a vehicle occupant is involved in the deceleration of the vehicle as early as possible. To prevent triggering of the belt tensioning mechanism during transport of the belt retractor prior to it being mounted in the vehicle, a sensor blocking element is provided which in its blocking position blocks an inertial mass of the sensor. The sensor blocking element is shifted into its release position when the belt retractor is installed in the vehicle. This may be done, for example, by means of a sensing pin which on installation of the belt retractor comes into contact with a part of the vehicle and is urged into the housing of the belt retractor. 
     The disadvantage in this known belt retractor is that no possibility is provided to prevent an activation of the belt tensioning mechanism when the seat belt is not in use at all. So if the vehicle is involved in an accident, the belt tensioning mechanism is actuated even when, for example, the belt retractor concerned is provided for the front-passenger seat and the front-passenger seat is unoccupied. 
     The object of the invention is to provide a belt retractor of the aforementioned kind in which a transport safeguarding device, preventing activation of the belt tensioning mechanism when the belt retractor is not incorporated in a vehicle, is combined in a simple way with an occupancy sensor, preventing a triggering of the belt tensioning mechanism when the seat belt of the belt retractor is not in use. 
     SUMMARY OF THE INVENTION 
     The invention provides belt retractor for a vehicular seat belt system, comprising a belt reel taking up a seat belt, a belt tensioning mechanism capable of biasing the belt reel in a winding direction of the seat-belt, and a sensor capable of triggering the belt tensioning mechanism and provided with a safety device translatable by installation of the belt retractor in a vehicle from a secured condition in which the sensor is blocked, into a released condition in which the sensor is ready to trigger. The safety device includes a sensor blocking element which is movable between a blocking position in which the sensor is blocked, and a release position in which the sensor is ready to trigger, and includes a transport locking element and a sensing element. The sensing element senses a diameter of a coil of the seat belt on the belt reel and allows a movement of the sensor blocking element into the release position only when the diameter is below a predetermined value. The transport locking element is movable between a locked position and a release position. A spring is provided which biases the transport locking element into the release position, and a further spring is provided which biases the sensor blocking element into the release position. The transport locking element comprises a retaining section which in the locked position engages an arresting section of the sensor blocking element and maintains it in the blocking position. 
     According to a preferred embodiment of the invention the transport locking element and the sensor blocking element are configured as sliders. In this way the necessary reliable mounting of these two parts can be configured in a relative simple way. A translatory mounting arrangement ensures that all components will still function as desired, even after a working life of up to 15 years, so that the sensor is automatically secured when the belt retractor is removed from the vehicle. 
     According to this preferred embodiment it is further provided that the springs are compression springs, this offering more safety than the leaf springs employed usually in prior art. During the long time in which the belt retractor may be installed in the vehicle, leaf springs in fact tend to setting more than compression springs so that employing compression springs ensures added assurance that the sensor will be secured again when the belt retractor is removed. 
     Advantageous aspects of the invention read from the sub-claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described with reference to a preferred embodiment as evident from the attached drawings in which: 
     FIG. 1 is a schematic view of a belt retractor according to the invention, the belt tensioning mechanism being omitted for better clarity; 
     FIG. 2 is a side view of the belt retractor as shown in FIG. 1 with the belt tensioning mechanism; 
     FIG. 3 is another side view of the belt retractor as shown in FIG. 2; 
     FIG. 4 is the same view as shown in FIG. 1, but with a few housing parts omitted; 
     FIGS. 5 to  8  are views corresponding to those of FIGS. 1 to  4 , whereby the belt retractor is shown in a second condition; 
     FIGS. 9 to  12  are views corresponding to those of FIGS. 1 to  4 , whereby the belt retractor is shown in a third condition; 
     FIGS. 13 to  16  are views corresponding to those of FIGS. 1 to  4 , whereby the belt retractor is shown in a fourth condition; 
     FIG. 17 is a section view of a sensor which may be used in a belt retractor according to the invention and is shown in a neutral position; 
     FIG. 18 is a view of the sensor as shown in FIG. 17 in which it is shown in an actuated position; 
     FIG. 19 is a schematic view of a belt retractor according to a second embodiment of the invention; 
     FIG. 20 is a view of the sensor as shown in FIG. 19, whereby the belt retractor is shown in a second condition; 
     FIG. 21 is a view of the sensor as shown in FIG. 19, hereby the belt retractor is shown in a third condition; 
     FIG. 22 is a schematic view of a belt retractor according to a third embodiment of the invention; 
     FIG. 23 is a view of the sensor as shown in FIG. 22, whereby the belt retractor is shown in a second condition; 
     FIG. 24 is a view of the sensor as shown in FIG. 22, whereby the belt retractor is shown in a third condition. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1 to  4  there is illustrated schematically a belt retractor according to a first embodiment of the invention, whereby the parts of the belt retractor not needed in appreciating the invention are omitted for better clarity. The belt retractor contains a belt reel indicated schematically by the coil of the seat belt  10  held therein. Starting from this coil, the seat belt  12  extends which is made available to a vehicle occupant. The belt reel is rotatably mounted in a frame  14  which can be fastened to a vehicle by means of a threaded projection  16  into which a fastener bolt can engage. 
     Provided in a housing is a belt tensioning mechanism  18  (not shown in detail) which upon activation is able to rotate the belt retractor and hence the coil of the seat belt  10  in the wind-up direction of the belt so that any slack in the seat belt system is eliminated. The belt tensioning mechanism may be of any design; it being, for instance, a pyrotechnic linear drive acting on the belt reel via a cable or gear rack or it may be a rotary piston drive. Details as to its configuration are irrelevant to appreciating the present invention. 
     In case of need, the belt tensioning mechanism is triggered by means of a mechanical sensor  20  (see also FIGS.  17  and  18 ). The sensor  20  comprises a translationally shiftable inertial mass  22  which by means of a deceleration acting in the direction of the arrow P can be moved from its neutral position as evident from FIG. 17 into its actuated position as evident from FIG.  18 . 
     The sensor contains furthermore an intermediate element  24  which is mounted sliding and, after the inertial mass  22  has executed a predetermined idle stroke from its neutral position toward its actuated position, is entrained by the latter. 
     The intermediate element  24  is provided with a nose  25 , the function of which will be explained further on, and a projection  26  which in the neutral position supports the free end  28  of a supporting lever  30 . Supported by a projection  32  of the supporting lever  30  is an actuating finger  34  which is in contact by one conical end with a locking cone  36  of a striker pin  38 . In the neutral position as shown in FIG. 17 the actuating finger  34  maintains the striker pin  38  in a pretensioned position. When the inertial mass  22  is shifted from its neutral position into the actuated position, it is the intermediate element  24  that is first entrained as soon as the idle stroke of the inertial mass has been covered. Once the intermediate element  24  has executed a predetermined travel, the free end  28  of the supporting lever  30  is released. Thereafter, the actuating finger  34  can be moved out of its position as shown in FIG. 17 due to it receiving a pushing action resulting from the contact of the conical end of the actuating finger with the locking cone  36  of the striker pin  38 . Once the actuating finger has been shifted far enough the striker pin is able to act on an igniter (not shown) of the belt tensioning mechanism, causing it to be triggered. 
     What is provided is a safety device which ensures that the belt tensioning mechanism can only be triggered when the belt retractor is properly installed in the vehicle and, in addition, the seat belt held by the belt retractor is buckled up by a vehicle occupant. This safety device contains a sensor blocking element  40  configured as a sensor blocking slider which is mounted translationally shiftable in the sensor  20 . The sensor blocking slider  40  can be moved between a blocking position—in which it engages the nose  25  of the intermediate element  24 , holding it in the position as shown in FIG. 17 and a release position in which the intermediate element  24  can be translated from its position as shown in FIG. 17 into the position as evident from FIG.  18 . The sensor blocking slider  40  is biased by a compression spring  42  into its release position in which it, with respect to the FIGS. 2 and 3, protrudes further from the sensor  20  than in its blocking position. At its end facing away from the intermediate element  24  the sensor blocking slider  40  is provided with a sensing element  44  configured as a nose integral with the sensor blocking slider  40 . The sensing element  44  serves to sense the diameter of the coil of the seat belt  10 . 
     Furthermore configured on the sensor blocking slider  40  is an arresting section  46  comprising a surface area oriented at an angle of 45° to the shifting direction of the sensor blocking slider. Provided surrounding the sensing element  44  is a guide  48  applied to a cover  50  of the sensor  20 . 
     Also provided on the sensor  20  is a transport locking element configured as a transport locking slider  52  which serves to block the sensor  20  when the belt retractor is not properly installed in the vehicle. The transport locking slider  52  is mounted so as to be translationally shiftable between a locked position and a release position in a guide  54  likewise configured on the cover  50  of the sensor  20 . The transport locking slider  52  is biased by a spring  56  into its locked position toward the threaded projection  16 . The pretension of the spring  56  of the transport locking slider  52  is greater than the pretension of the compression spring  42  of the sensor blocking slider  40 . The transport locking slider  52  can be shifted from this locked position into the release position, in a direction perpendicular to the direction of movement of the sensor blocking slider  40  (to the right as shown in FIG.  3 ). 
     Configured on the transport locking slider  52  is a retaining section  58  comprising a surface area oriented at an angle of 45° relative to the direction of movement of the transport locking slider  52 . This surface area is oriented parallel to the surface area of the arresting section  46  configured on the sensor blocking slider  40 . 
     Referring now to FIGS. 1 to  4  there is illustrated the belt retractor in a condition in which it is not installed in a vehicle and in which no belt webbing has been pulled off from the belt retractor. The coil of the seat belt  10  thus has its maximum diameter. In this condition the transport locking slider  52  being in contact with the threaded projection  16  is in its locked position in which the retaining section  58  is supported by the arresting section  46  of the sensor blocking slider  40 . Since the two surface areas of the retaining section and arresting section  46  in contact with each other are inclined at an angle of 45° to the direction of movement of the transport locking slider  52  and the sensor blocking slider  40 , respectively, the sensor blocking slider  40  is urged against the actuation of its compression spring  42  into the blocking position in which the intermediate element  24  is locked in the position as shown in FIG.  17 . At the same time the sensing element  44  is in contact with the coil of the seat belt  10 . The sensing element  44  is dimensioned such that in this condition the sensor blocking slider  40  is urged from the coil of the seat belt  10  via the sensing element  44  into the blocking position. The sensor blocking slider  40  is thus doubly biased into its blocking position, i.e. for one thing, by the transport locking slider  52  via the retaining section  58  and the arresting section  46  and, for another, by the sensing element  44 . In this way it is safely and reliably inhibited that the sensor triggers the belt tensioning mechanism due to jolting as may occur during transport or in handling the belt retractor. 
     Referring now to FIGS. 5 to  8  there is illustrated the belt retractor in a second condition, whereby like reference numerals are used to identify the components already known from FIGS. 1 to  4  so that reference can be made to the description thereof. 
     In this second condition a specific length of belt webbing has been pulled off from the belt retractor, i.e. the coil of the seat belt  10  now has a smaller diameter, so the sensing element  44  is no longer in contact with the coil of the seat belt. Despite this, the spring  42  of the sensor blocking slider  40  is incapable of translating the latter into the release position, since the sensor blocking slider  40  is biased by the transport locking slider  52  via the retaining section  58  and the arresting section  46  into the blocking position, due to the pretension of the spring  56  of the transport locking slider  52  being greater than the pretension of the compression spring  42  of the sensor blocking slider  40 . This ensures that—even when belt webbing is pulled off during transport or in handling the belt retractor—the sensor is safely and reliably secured against triggering of the belt tensioning mechanism as long as the belt retractor is not installed in a vehicle. 
     Referring now to FIGS. 9 to  12  there is illustrated the belt retractor in a third condition. Here too, like reference numerals are used to identify the components already known from FIGS. 1 to  4  so that reference can be made to the description thereof. 
     In this third condition the sensor  20  is not secured so the belt tensioning mechanism could be triggered by a corresponding deceleration in the direction of the arrow P. By means of a fastener bolt  60  screwed into the threaded projection  16 , the transport locking slider  52  has been moved from its locked position into the release position in which the retaining section  58  no longer engages the arresting section  46  of the sensor blocking slider. Furthermore, a specific length of belt webbing has been pulled off from the belt retractor so that the coil of the seat belt  10  has a diameter which is less than a predetermined diameter. As of this predetermined diameter, the sensor blocking slider  40  is shifted—by the action of the spring  42  biasing it—so far toward the coil of the seat belt into its release position that it no longer engages the nose  25  of the intermediate element  24 . 
     Accordingly, the intermediate element can be entrained by the inertial mass when the latter is moved from its neutral position into the actuated position. Thus, in this condition in which the belt retractor is installed in the vehicle and in addition the seat belt has been buckled up by the vehicle occupant, the belt tensioning mechanism can be triggered. 
     Referring now to FIGS. 13 to  16  there is illustrated the belt retractor in a fourth condition. Here again, like reference numerals are used to identify the already known components so that reference can be made to the description thereof. 
     In the fourth condition the belt retractor is installed in the vehicle by means of the fastener bolt  60 , however, no belt webbing having been pulled off from the belt retractor here. This is the case, for instance, when the belt retractor makes the seat belt available for the front-passenger seat but the front-passenger seat is either unoccupied or the vehicle occupant seated therein has not buckled up. Although in this condition the transport locking slider  52  is maintained in its release position by the fastener bolt  60 , in which the retaining section  58  is not in contact with the arresting section  46 , the sensing element  44  in contact with the coil of the seat belt  10  prevents the sensor blocking slider  40  from being urged by its compression spring  42  from the blocking position into the release position. Thus, the sensor blocking slider  40  prevents the intermediate element  24  from being entrained by the inertial mass  22 . This ensures that the belt tensioning mechanism is not triggered in an accident situation since tensioning the seat belt makes no sense when not buckled up. 
     When the fastener bolt  60  is removed and the belt retractor detached, the spring  56  ensures that the transport locking slider  52  is returned into its locked position. In this position, the sensor blocking slider  40  is urged into the blocking position by means of the retaining section  58  and the arresting section  46 , in which an activation of the belt tensioning mechanism is prevented. Since the transport locking slider  52  and the sensor blocking slider  40  are both mounted translationally shiftable and the two springs  56  and  42  are compression springs which tend to settle only very slightly in time it is ensured that the sensor  20  will be reliably locked on detaching of the belt retractor even after it had been installed for a long time, for example, 15 years. 
     Referring now to FIGS. 19 to  21  there is illustrated the belt retractor according to a second embodiment of the invention. Like reference numerals are used to identify the components already known from the first embodiment so reference can be made to the description thereof. 
     In this embodiment, the transport locking element is configured as a transport locking lever  152  mounted pivotably on a trunnion  151  and comprising an end  153  cranked upwards with respect to FIG.  19 . The transport locking lever  152  is biased by a compression spring  156  downwards with respect to FIG. 19 into its locked position. Configured on the transport locking lever  152  is a retaining section  158  supported by the arresting section  46  of the sensor blocking slider  40  urging it against the biasing force of its compression spring  42  into the blocking position. 
     The transport locking lever  152  is moved from its blocked position shown in FIG. 19 into its release position shown in FIG. 20 by screwing in the fastener bolt  60 , whilst the fastener bolt  60  is sliding on the cranked end  153  of the transport locking lever  152  pushing it upwards with respect to FIG.  20 . Thus the retaining section  158  releases the sensor blocking slider  40  which is shifted by the biasing force of the spring  42  toward the coil of the seat belt  10 . With its sensing element  44 , the sensor blocking slider  40  is now in contact with the coil of the seat belt so that when the coil has a predetermined diameter, the sensor blocking slider  40  reaches its release position, as is shown in FIG.  20 . The further function is similar to that of the belt retractor according to the first embodiment. 
     Referring now to FIGS. 22 to  24  there is illustrated the belt retractor according to a third embodiment of the invention. Again like reference numerals are used to identify the components already known from the precedent embodiments so reference can be made to the description thereof. 
     In this embodiment, the sensor blocking element is configured as a sensor blocking lever  140  mounted pivotably on a trunnion  141  and biased by the spring  42  from a blocking position shown in FIG. 22 into a release position shown in FIG.  24 . An arresting section  146  configured as a cone is provided on the sensor blocking lever  140 , the cone supporting the retaining section  58  of the transport locking slider  52 . At its end facing away from the intermediate element  24  the sensor blocking lever  140  is provided with a sensing element  44  configured as a nose integral with the sensor blocking lever  140 . The sensing element  44  serves to sense the diameter of the coil of the seat belt  10 . 
     In FIG. 22 the transport locking slider  52  is located in its locked position in which the retaining section  58  of the transport locking slider  52  is in contact with the arresting section  146 , thus maintaining the sensor blocking lever  140  in its blocking position against the force of the compression spring  42 . As soon as the transport locking slider  52  is moved into its release position shown in FIG. 23 by screwing in the fastener bolt  60 , the retaining section  58  releases the arresting section  146  so that by means of its sensing element  44 , the sensor blocking lever  140  is in contact with the coil of the seat belt. 
     If the diameter of the coil of the seat belt  10  is reduced by pulling off the belt webbing, the compression spring  42 , as soon as the diameter of the coil has reached as predetermined value, pivots the sensor blocking lever  140  in the direction of the coil of the seat belt  10  until the sensor blocking lever  140  has reached its release position shown in FIG.  24 . 
     The further function is again similar to that of the belt retractor according to the first embodiment.