Abstract:
An adjusting mechanism for a seat includes two mechanism parts that form parts of a staggered transmission. An eccentric cam consists of an eccentric segment and two wedge segments completing this eccentric segment. The wedge segments are arranged one above the other in a radial direction, and their thicknesses increase in an opposite direction to each other. They are so tensioned by a common spring that they form an extended eccentric area under pre-tension from the spring, and are pressed against each other during rotation in such a manner that the eccentric area becomes smaller and thus the tension of the intermeshing toothed areas is reduced.

Description:
FIELD OF THE INVENTION 
     The invention relates to an adjustment mechanism for an automobile seat back. 
     BACKGROUND OF THE INVENTION 
     In a known adjustment mechanism of the prior art as described in DE 30 13 304 C2, part of the wedge segments that form an eccentric cam and are tapered in opposite rotational directions are positioned on a bearing surface concentric to the axis of rotation. A pressure spring stretched between the broad frontal surfaces of the two wedge segments forces the wedge segments in opposing directions with the result that the eccentricity increases because of the spring&#39;s effect. 
     A disadvantage to this known solution is that the length of the wedge segments, i.e., the angle formed by the effective supporting surfaces, is restricted. This restriction is essential to the system. Too great an effective length has the result that the front wedge segment in the direction of rotation does not adequately release the teeth as desired during actuation, but rather presses them together. In practice, the inner contact surface of both wedge segments is therefore relatively short. A relatively short contact surface leads to faster wear because the wedge segment may tip along its supporting surface. 
     SUMMARY OF THE INVENTION 
     Based on this state of the art, the present invention features an adjustment mechanism of the type known so that it is formed to be as resistant to wear as possible and to operate silently. 
     These goals are achieved by the present invention wherein the positioning of the wedge segments in a radial direction with one above the other and with opposite orientation allows the option of selecting an effective length of the wedge segments to be longer than that used in the state of the art, thus forming an articulated mechanism that is more resistant to wear. Because of the comparatively large potential wedge length, it is even possible not to use the entire wedge length, but rather only to provide supporting surfaces at the two ends, leaving the central area free. This promotes silence during operation and reduces manufacturing costs. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the present invention will be better understood by reading the following detailed description, taken together with the drawings wherein: 
     FIG. 1 is a front view of the adjustment mechanism along the rotational axis as seen from one side; 
     FIG. 2 is a front view of the adjustment mechanism as in FIG. 1 along the rotational axis as seen from the opposite side; 
     FIG. 3 is a cross-sectional view along plane III—III of FIG. 2; and 
     FIG. 4 is a cross-sectional view along plane IV—IV of FIG.  3   
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The adjusting mechanism shown and described herein is a typical incline adjusting mechanism for an automobile seat back, although the present invention may be used in other applications. The adjusting mechanism includes a fixed mechanism part  1  that is arranged in the area of the seat (not shown), and a mechanism part  2  that is adjusted by rotation and is connected to the seat back (also not shown). 
     The fixed mechanism part  1  includes a toothed region  1   a , FIG.  4 . This toothed region  1   a  is shaped to surround and grip a toothed region  2   a  of the movable mechanism part  2 . The toothed regions  1   a  and  2   a  form the parts of a staggered transmission. 
     The mechanism part  2  includes stepped receptor aperture  2   b , FIG. 3, in which the rear portion of a bearing bushing  6  is fixed. The bearing bushing  6  forms an internal rotational bearing  6   a  with its inner cylindrical surface. An eccentric cam indicated overall with the numeral  4  is free to rotate around a rotational axis  3 . The eccentric cam  4  includes various integrated, inter-connected areas, namely a pivot area  8  that possesses a non-round central follower aperture  8   a , as well as a disc area  9  and an eccentric cam segment  4   a.    
     The pivot area  8  is attached by means of a securing element  10  that is formed as a disc securing part with spring arms arranged radially inwards across from the bearing bushing  6  penetrated by the pivot area  8  in the direction of the rotating axis  3 . 
     The eccentric cam segment  4   a , FIG. 4, moves within an outer rotational bearing  5   a  that is formed by a bearing ring  5  pressed into the mechanism part  1 . The eccentric cam segment  4   a  grips the exterior of the bearing bushing  6  as shown in FIG. 3 with its interior surface. It is advantageous if the surfaces of the eccentric cam segment  4   a  bent inward and outward maintain a certain separation from each opposing surface. 
     Two wedge segments  4   b  and  4   c  complete the eccentric cam formed by eccentric cam segment  4   a.    
     The bent wedge segments  4   b  and  4   c  are arranged in an opposing direction. Their narrower contact surfaces  4   g  or  4   h  are positioned in the direction of the surrounding parts next to the adjacent wider contact surfaces of the wedge segments  4   b  or  4   c . direction opposite of the wider contact surfaces of the other wedge segments 
     A bent spring  7  includes an area  7   a , FIG. 3, bent into a circle that grips around the rotational axis  3 . The area  7   a  bent into a circle extends in a direction parallel to the rotational plane of the eccentric cam  4 . The areas  7   b  bent inwards to which the end areas  7   c  bent at a right angle are connected to this area. The one end area  7   c  fits into the receptor hole  4   i  of the wedge segment  4   b , and the other end area bent at a right angle fits into the receptor hole  4   k  of the other wedge segment  4   c.    
     The spring  7  is so pre-stressed that it is forced to reduce the separation between the two receptor holes  4   i  and  4   k . Because of this and of the wedge shape of the wedge segments  4   b  and  4   c , these wedge segments are spread apart between the support area of the outer rotational bearing  5   a  and the circular cylindrical exterior area  6   b  of the right area of the bearing bushing  6  in FIG.  3 . 
     The eccentric cam segment  4   a  possesses two contact surfaces  4   e  and  4   f . When the eccentric cam  4 , and thereby the eccentric cam segment  4   a  according to FIG. 4, rotate clockwise, the striking surface  4   e  comes in contact with the projected contact surface  4   g  of the wedge segment  4   c  that is carried along against the force of the spring  7  in a clockwise direction. This causes the grip of the sides of the toothed areas  1   a  and  2   a  on the side of the highest point of the eccentric cam to loosen. The tension that prevents rattling of the mechanism while it is not engaged is thereby released during rotation. 
     A counter-clockwise rotational direction of the eccentric cam  4  and thereby the eccentric segment  4   a  according to FIG. 4, likewise leads to contact by the striking surface  4   f  onto the contact surface  4   h  and to a dislocation of the wedge segment  4   b  in the same rotational direction. Also, the pre-tension of the toothed areas  1   a  and  2   a  at the highest point of the eccentric cam is reduced, allowing a non-tensioned clockwise rotation of the adjustment mechanism. 
     As soon as the rotation is ended and the parts have come to rest, the right-angled ends of the spring  7  pull the wedge segments  4   b  and  4   c  apart again, thereby increasing the eccentricity, with the result that the toothed areas  1   a  and  2   a  lying radially and engaging each other through the highest point of the eccentric cam in a plane are again pressed together. 
     In the embodiment of the invention shown, the inner diameter of the wedge segment  4   b  rests with its entire length on the outer diameter of the bearing bushing  6 . It is now possible to reduce the application area of the wedge segment  4   b  on the exterior surrounding surface  6   b  in this manner so that one may provide a recess (not shown) between the two application surfaces neighboring the contact sides. The support of the wedge segment  4   b  at its end area prevents damage through tilting of this wedge segment in any case. 
     Adjustment mechanisms that operate according to the principle of a staggered transmission are known. For this type of transmission to which the adjusting mechanism based on the invention belongs, an eccentric cam or an eccentric surrounding area rotates across from the rotational axis  3 . The eccentric  4  capable of being rotated and driven is supported by the exterior rotational bearing  5   a  in one mechanism part  1  and by the eccentric interior rotational bearing  6   a  in the other mechanism part  2  opposite the exterior rotational bearing  5   a.    
     The toothed areas  1   a  or  2   a  are formed integrally with mechanism parts  1  and  2 , usually made of a metal sheet using a fine-cutting procedure. The two-toothed areas  1   a  and  2   a  have different quantities of teeth and different diameters. The toothed area  1   a  has a smaller diameter and a smaller quantity of teeth than the toothed area  2   a . Rotation of the eccentric cam causes a horizontal swiveling of the mechanism part  2  about the rotational axis  3  with respect to the mechanism part  1 . The eccentric cam  4  ensures that both toothed areas  1   a  and  2   a  match each other in the area that is radial to the position of the highest point of the eccentric cam. In the other areas, the teeth of both intermeshing toothed areas are more or less positioned far apart. 
     Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the claims that follow.