Abstract:
A safety belt arrangement comprising a holder which can be pivotally connected to a vehicle part about an axis which has a guide roller between two bearings. In the fastened state at least a band part of the belt band which partially wraps around the guide roller extends at an inclination to the axis of rotation of the guide roller. At increased brake forces the guide roller enters into engagement with a projection.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a safety belt arrangement with a holder which can be fastened to a vehicle part and which journals a guide roller between two bearings, with at least one band part of the belt band which partially wraps around the guide roller extending at an inclination to the axis of rotation of the guide roller in the fastened state. 
     Roller guides are basically known in various variants. Safety belt arrangements of this kind are used in motor vehicles in order to deflect the belt band which is unwound from a belt roller in the direction towards the passenger. FIG. 8 shows a roller guide for a safety belt which has a holder  10  of metal which is approximately oval in a plan view and in which a cut-out  11  which is basically rectangular and upwardly open is provided for a guide roller  22 . Above the cut-out  11  a circular opening  12  for the fastening of the holder  10  to a vehicle is provided centrally in the holder  10 . A shaft  20  is rotatably fastened between two bearings in order to be able to rotate the guide roller  22  in a friction-poor manner when the belt band  14 , which is guided around the guide roller  22 , is moved, for example in order to put on the safety belt. 
     In the fastened state of this safety belt arrangement, that is, when the safety belt  14  has been put on by a passenger, the safety belt  14  partially wraps around the guide roller  22 . In this the band part B of the belt band  14  extends at an inclination to the axis of rotation of the guide roller  22  in the situation illustrated in FIG.  8 . The band part A of the belt band  14  extends at right angles to the axis of rotation of the guide roller  22 . In addition to the situation illustrated in FIG. 8, however, in the fastened state both band parts A and B of the belt band  14  can also extend at an inclination to the axis of rotation of the guide roller  22 . 
     The inventors of the present application have recognised that in a safety belt arrangement such as is shown in FIG. 8, the belt band  14  is no longer correctly guided via the guide roller  22  at higher belt forces but rather is transported laterally (to the right in FIG. 8) as a result of the skewing present between the belt band parts A and B. This can have the result that the resulting force of the belt band  14  runs out of the axis of rotation of the holder  10 , so that the guide fitting executes an undesirable and abrupt movement. In this the belt band can be completely pulled into a corner of the deflection, which can impair the correct functioning of the safety belt arrangement, in particular when additional safety devices such as belt tighteners are provided. 
     SUMMARY OF THE INVENTION 
     The problem (object) underlying the invention is to provide a safety belt arrangement of the initially named kind in which a correct deflection of the belt band about the guide roller is ensured even at increased belt forces. 
     This object is satisfied by the features of claim  1  and in particular in that the journalling of the guide roller is designed elastically and in that a brake device is provided which enters into engagement with the guide roller at increased belt forces. A brake device of this kind can for example be formed in that the shaft on which the guide roller is journalled or the bearings on which the shaft is journalled are designed elastically. 
     Through the brake device provided in accordance with the invention the guide roller is braked or completely blocked at increased belt speeds, through which a lateral transport of the belt band on the guide roller is avoided. Since a skewed belt band which is guided around a guide roller is laterally transported during the application of a drawing force only when very large belt forces are present and when the guide roller can rotate, the brake device provided in accordance with the invention prevents an undesirable lateral transport of the belt band in an effective manner. The brake device is preferably released from engagement when the belt forces let up so that in this case the guide roller can again rotate freely. 
     Advantageous embodiments of the invention are described in the description, in the drawings and in the subordinate claims. 
     The safety belt arrangement in accordance with the invention has at least one, preferably two resiliently executed bearings, through which it is ensured that forces which are exerted on the safety belt—and thus also on the guide roller or the bearings respectively—are first taken up by the resiliently executed bearing. When large forces arise, the bearing deforms elastically to such an extent that the guide roller is pressed against an abutment or the like so that the rotational movement of the guide roller is braked or stopped respectively. Subsequently the belt band can slide over the braked guide roller without a transverse movement arising in the region of the guide roller. 
     In accordance with a further advantageous embodiment the bearing can have a sleeve-like shape and be open at one end and closed at an opposite end, through which a simple manufacture is possible. The bearing can be manufactured by an injection moulding or an extrusion process. 
     In a third preferred embodiment of the invention the bearing can be widened at the outer periphery of the open end, through which the bearing can be reliably held by the widened edge in an aperture of the holder and a sliding in of the bearing into the aperture is excluded. 
     In a further embodiment the bearing can have at the open end a plurality of slit-like or conical cut-outs extending in the axial direction that is parallel to the axis of rotation of the guide roller, which are preferably arranged to lie opposite one another. Through this the bearing can be compressed slightly at the open end and can be pressed into an aperture in the holder in the axial direction, through which its installation is facilitated. 
     A good spring action for a shaft results in accordance with a further advantageous embodiment of the invention if the bearing is inserted into an aperture in the holder which is executed as a passage bore. In this case the bearing has a free space in order to be resilient in the axial direction. 
     In accordance with a further embodiment of the invention the bearing can have a convex bearing surface at the closed end and in the interior which is preferably arranged concentrically at an inner end face. The contact surface of the guide roller or its shaft respectively in the bearing is thereby minimised, and through the point contact between the shaft end and the bearing the frictional forces can be considerably reduced. Through the low wear arising which is connected therewith, a long lifetime of the bearing is furthermore ensured. 
     In accordance with a preferred embodiment the bearing can be made cylindrical and have at least two regions with different diameters. Furthermore, the bearing can have the larger diameter at the side of the open end and preferably form a contraction after about one half its length. The bearing can also have a section of varying diameter-shaped cross-section between the two regions of different diameter, with a good spring action being achieved through this special shaping of the bearing. The section of varying diameter can at least partially extend inside the region with the greater diameter. 
     It is advantageous if the bearing lies with the outer surface of the region with the greater diameter in contact with a wall of the aperture of the holder. Through this a good area contact with the holder is possible, through which a high and uniform force transmission can take place. 
     The bearing can preferably consist of a plastic, e.g. of polyoxymethylene, which preferably has a Teflon reinforcement. Through the high cristallinity, the construction material polyoxymethylene (POM) can be machined to a very hard, stiff, percussion-tough and abrasion-proof bearing. The strength and stiffness of the material can be further increased with a glass fibre reinforcement, and the abrasion resistance can be further increased by an alloying in of elastomers. 
     In accordance with a further embodiment of the invention the guide roller can have concave or stepped cut-outs at its two end sides. Sufficient space is thereby provided opposite the widened edge of the bearing, which projects somewhat in the direction of the end sides of the guide roller, so that a contact or a rubbing between the widened edge of the bearing and the end side of the guide roller is excluded. 
     Preferably the guide roller can have a shaft which tapers at its two ends and which forms an extension which is made smaller by about a third of the original diameter. The ease of movement of the roller guide is thereby ensured since the shaft contacts the bearing only slightly (in a point-like manner) at the sides, and thus the lowest friction and nearly no abrasion arise. 
     In order to enable an inter-engagement of the brake device, the bearing shaft of the guide roller can be designed flexibly. Through this the bearing shaft bends through somewhat at high drawing forces or belt forces respectively so that the guide roller enters into engagement with a projection or an abutment which is provided. 
     The brake device can have at least one projection, which is preferably provided at the holder, by means of which the guide roller enters into engagement after the latter has been moved by the arising belt forces in the direction of the projection. 
     It is particularly advantageous if the brake device has at least one depression which is provided at the guide roller. In this case the projection provided at the holder can enter into engagement with the depression or depressions when the brake device is activated so that the guide roller is completely blocked. A particularly reliable engagement is achieved when the depression and the projection are formed substantially complementarily. A particularly rapid activation of the brake device is ensured when a plurality of depressions are uniformly distributedly arranged over the periphery of the guide roller. 
     Since the basic problem arises in particular in safety belt arrangements in which the skewing between the two belt bands amounts to at least 30°, the present invention produces particularly good results in a belt band configuration of this kind. The invention can in particular also be particularly advantageously used when the wrapping angle of the belt band about the guide roller amounts to at least 90°. 
     In a method in accordance with the invention the guide roller, which rotates when the belt band moves, is moved in the direction of a brake device at a predetermined belt force in order to brake or stop the rotation of the guide roller. In this the movement of the guide roller in the direction of an abutment or the like can be stopped by the corresponding choice of the elastic bearings or of an elastic shaft. 
     The guide roller is preferably moved reversibly away from the brake device when the belt force lets up. 
     In addition to the illustrated exemplary embodiments it is also possible to provide an active braking, for example through a setting member or the like. 
     The invention will be explained in the following in a purely exemplary manner with reference to advantageous embodiments and with reference to the accompanying drawings. Shown are: 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 a partially sectioned illustration of an embodiment of a safety belt arrangement in a frontal view; 
     FIG. 2 a partially sectioned illustration of a further embodiment of a safety belt arrangement in a frontal view; 
     FIG. 3 a longitudinal section through a guide roller; 
     FIG. 4 a side view of a shaft; 
     FIG. 5 a view of the open end side of a bearing; 
     FIG.  5   a  a side view of the bearing of FIG. 5; 
     FIG.  5   b  a section along the section line A—A of FIG. 5; 
     FIG. 6 a sectioned side view of a further embodiment of a bearing; 
     FIG. 7 a sectioned side view of a further embodiment of a bearing; and 
     FIG. 8 a perspective view of a safety belt arrangement with a skewed belt band. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows a safety belt arrangement having a holder  10  of metal which is approximately oval in a plan view and in which a basically rectangular and upwardly open cut-out  11  is provided for a cylindrical guide roller  22 . Above the cut-out  11  a circular opening  12  is provided centrally in the holder  10  for the fastening of the holder  10  to a vehicle. A part formed of plastic can in each case be inserted into the front and rear side of the opening  12  in order to achieve a noise reduction in a pivoting of the holder  10 . 
     The holder  10  is formed convexly above the cut-out  12 , with limb-like outwardly arched formations  16  which run together into a web  17  below the cut-out extending in each case downwardly at the sides of the opening  12 . Within the cut-out  11  and in the central region of the holder  10  two circular cylindrical apertures in the form of bores  18  are provided which in each case pass through a formation  16  and extend coaxially to one another and parallel to the web  17 . Above the bores or apertures  18 , which each serve for the reception of a bearing  24 ′ (in FIG. 1 only the right bearing is illustrated), and extending at right angles to them, two circular guide openings  19 , of which the edges extend in a convexly curved manner from the centre plane of the holder  10  to their front and rear sides and which open towards the upper side of the cut-out  11 , are provided in the holder  10 . These guide openings serve for the friction-poor guidance of the belt band in the event that the latter is rolled out or wound up at an inclination. The two bearings  24 ′ journal a shaft  20  between themselves which is connected to the guide roller  22 . 
     For the assembly of the roller guide the shaft  20  is introduced from one side of the holder  10  into a bore  18  from there and up to the oppositely disposed bore  18  of the other limb  16 , with the guide roller  22 , which after insertion of the shaft  20  is passed through by the latter, having previously been inserted in the cut-out  11  between the two limbs  16 . Then a bearing  24 ′ is inserted from each side of the holder  10  into the passage bore  18  and is latched there. The shaft  20  now engages with each of its two ends into a bearing  24 ′ and carries the guide roller  22 , which is firmly latched on the shaft  20 . The mounting of the holder  10  at a vehicle part, in particular at a B-pillar of a motor vehicle, is done through the circular opening  12  and the latched-in form parts. 
     As is further shown in FIG. 1, a projection  21  which points in the direction of the guide roller  22  and extends in the axial direction of the guide roller  22  is formed on approximately in the middle of the web  17 . In a normal, that is, stress-free winding off of the belt band about the guide roller  22  no contact between the projection  21  and the outer periphery of the cylindrical guide roller  22  takes place. If, however, the belt force, that is, the drawing force exerted on the belt, increases beyond a certain, preset value, then the bearings  24 ′ bend through correspondingly so that a frictional contact is effected between the projection  21  and the outer periphery of the guide roller  22 . Through this the rotational movement of the guide roller is slowed down and finally stopped completely. When the belt force lets up, the bearings  24 ′ again move elastically back to their initial position so that the guide roller  22  can rotate freely about its axis of rotation X. When the guide roller  22  is blocked the belt band  14  (cf. FIG. 8) does not move in the direction of the axis of rotation X of the guide roller  22 . Rather, the belt band slides over the blocked guide roller without a transverse movement arising. 
     FIG. 2 shows a partially sectioned view of a further embodiment of a safety belt arrangement, with the same reference symbols being used for the same parts. The embodiment illustrated in FIG. 2 differs from that in FIG. 1 essentially in that cut-outs  23  which are distributed over the periphery and which are formed substantially complementarily to the projection  21  formed on the web  17  are provided at the outer periphery of the guide roller  22 ′ and approximately in its centre. Here as well no contact takes place between the projection  21  and the guide roller  22 ′ during normal operation. Only at a preset belt force do the bearings  24 ′ (in FIG. 2 as well, only the right bearing  24 ′ is illustrated) bend through to such an extent that the projection  21  engages into one of the cut-outs  23  and thereby blocks the guide roller  22 ′ completely. Since the cut-outs  23  are uniformly distributed over the entire periphery of the guide roller  22 ′, a rapid engagement into one of the cutouts  23  is ensured when a predetermined belt force is reached. 
     The bearing  24 ′ illustrated in FIG. 2 corresponds to the embodiment illustrated in FIG. 6, which will be described in the following in more detail. 
     As can be well recognised in FIG. 2, the circular guide openings which are provided above and at both sides of the guide roller and which open in the direction of the upper edge of the guide roller serve for the guidance of the belt band when the latter is drawn out at an inclination with a low belt force (for example when the belt is being put on). As can furthermore be well recognised, the guide roller  22 ′ has in each case cut-outs  30  at both of its end sides which prevent a contact between the guide roller  22 ′ and the bearings  24 ′. The bearing  24 ′ is located (as in the embodiment of FIG. 1 also) up to a broadened or widened edge  25  in the bore  18  and lies there with the outer surface of its region with the larger diameter in contact with the inner wall of the bore  18 . 
     FIG. 3 shows a longitudinal section through the guide roller  22  illustrated in FIG. 1 which is provided with an axial passage bore  26 . 
     Stepped cut-outs  30  are provided at the two end sides  28  of the guide roller  22 . In the interior of the guide roller  22  illustrated in FIG. 3 a circumferential ring projection  32  is provided which serves for the latching on of the guide roller  22  on the shaft  20 . 
     FIG. 4 shows in detail the shaft  20  illustrated in FIGS. 1 and 2, the ends of which have pin-like extensions with convex ends  34 . Furthermore, the shaft  20  has two circumferential ring grooves  36 , which serve for the latching in of the ring projection  32  of the guide roller  22 . The pin-like extensions of the shaft  20  or also the entire shaft  20  can be designed flexibly in order to effect an elastic and flexible bending through of the shaft or of the shaft ends respectively when a certain belt force is reached so that the guide roller, which is fastened to the shaft, enters into engagement with the projection  21 . 
     FIG. 5 shows an enlarged front view and FIG.  5   a  an enlarged side view of a further embodiment of a bearing  24 . A longitudinal section through this bearing is illustrated in FIG.  5   b.    
     As these figures show, the bearing  24  has a sleeve-like form and is formed to be open at its (in FIGS.  5   a  and  5   b ) left end  42  and closed at the opposite end  46 . At the outer periphery of the open end  42  the bearing  24  has a widened edge  25  which has a run-up inclination in order that the bearing can be inserted into the bore  18  of the holder  10 . 
     Four slit-like cut-outs  38  extending in the axial direction are provided at the open end  42  of the bearing  24 , with two cut-outs being arranged oppositely in each case. The cut-outs  38  are conically formed and extend over approximately one third of the bearing. 
     The bearing  24  is basically cylindrically formed and has two regions with different diameters, with the region of the larger diameter extending over nearly the entire length of the bearing  24 . The region with the smaller diameter is located to the greatest extent inside the region with the larger diameter and is connected to the region with the larger diameter by a formation  50  which is meander-like in cross-section or is a section of varying diameter. 
     FIG. 6 shows in detail the bearing  24 ′ shown in FIGS. 1 and 2 in which likewise a region with a larger diameter and a region with a smaller diameter are provided, with the transition region tapering conically and the region with the smaller diameter being located completely outside the region with the larger diameter, so that in cross-section a bottleneck-like arrangement is given. A convex bearing surface  48 ′ which is concentrically positioned is arranged at the inner side of the closed end  46 ′. In this embodiment as well a widened edge  25 ′ is provided at the open end  42 ′ of the bearing  24 ′. Two cut-outs  38 ′ which are substantially rectangularly formed extend from the open end  42 ′ in the axial direction of the bearing. In this embodiment as well the smaller diameter amounts to about 40% of the larger diameter. 
     FIG. 7 shows the cross-sectional view of a further embodiment, which is similar to that illustrated in FIGS. 5 to  5   b . In this embodiment the bearing  24 ″ is formed in such a manner that the region with the smaller diameter lies completely inside the region with the larger diameter. At the inner end side of the closed end  46 ″ a convex bearing surface  48 ″ is provided centrally. The region with the smaller diameter extends over about 50% of the axial length of the bearing  24 ″. 
     Finally it is pointed out that the guide roller  22 ,  22 ′ itself can also be manufactured of an elastically deformable material so that it bends through flexibly when a predetermined belt force is exceeded in order to enter into engagement with a braking surface.