Abstract:
A toothed plate for a toothed-plate plate-link chain, wherein the toothed plate includes two teeth, each having an inner flank, and an indentation between the teeth. The indentation includes a transition between a tooth flank and a curved innermost region. The transition has a convex curvature and is positioned at a junction of one of the inner flanks and the innermost region.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a toothed plate for a toothed plate-link chain, wherein the toothed plate includes two teeth with tooth flanks, and having an indentation between the teeth. 
     2. Description of the Related Art 
     Toothed plates for toothed plate-link chains generally have an indentation at the vertical plane of symmetry of the plate. The indentation is defined by tooth inner flanks and by a transition curve having only a single radius. In addition, the tooth flanks and the transition curve are connected to each other at tangents, so that the transition curve radius joins the tooth flanks in such a way that there is a common tangent present at the connection point. Such toothed plates are known from U.S. Pat. No. 5,372,554 and U.S. Pat. No. 5,588,926. 
     A disadvantage of the known toothed plates is that high stresses can occur in the region of the indentation when the chain is in operation. 
     An object of the present invention is therefore to provide a toothed plate for a toothed plate-link chain in which the stresses that occur in the region of the indentation are smaller. 
     SUMMARY OF THE INVENTION 
     The above-identified object is achieved by a toothed plate for a toothed plate-link chain in which the toothed plate includes two teeth, each tooth having an inner flank. At the indentation between the teeth a transition from at least one of the inner flanks to the innermost end curvature of the indentation has a convex curvature. 
     In connection with the present invention, convex curvature means each form of curvature wherein the midpoint of the curve of a tangential circle lies on the surface of the toothed plate at least partially inside the toothed plate. The convex curvature can be smooth, that is, there is no sudden change of the tangents at two points lying as close together as desired, but it can also include an edge. Preferably, there is a provision that both transitions of the inner flanks toward the inner region indentation have a convex curvature. 
     In another form of the invention the indentation has concave curvature with a varying radius of curvature. The midpoint of the curve can constantly be outside of the toothed plate. In connection with the present invention, variable radius of curvature means that over the contour of the indentation various tangential circles with corresponding centers of curvature can be laid on the contour of the indentation. 
     In a further refinement of the invention, the varying radius of curvature is made up of discrete radii, i.e., that it is a stringing together of circle segments. The transitions between the discrete radii can be rounded off or can include an edge. 
     Alternatively, it can be provided that the varying radius of curvature changes continuously. That can occur, for example, with a curve that is described as a so-called spline curve. 
     The object identified above is also achieved by a plate-link chain that includes a toothed plate in accordance with the invention, as well as by a transmission having a toothed plate-link chain in accordance with the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a side view of a toothed plate showing various contours at an indentation; 
         FIG. 2  is an enlargement of one half of the tooth flank of the tooth shown in  FIG. 1 ; 
         FIGS. 3 through 5  are enlargements of the indentation region shown in  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a side view of a toothed plate for a toothed plate-link chain. Toothed plate  1  includes a main body  2  on which two teeth  3  and  3 ′ are positioned. Also in the main body are two openings  4  and  4 ′ for receiving rocker members that combine the individual toothed plates into toothed plate sets. Normally, the openings do not have circular inner contours—their inner contours are matched to the outer contour of the rocker members that are received therein. The rocker members form a hinge joint between adjacent toothed plate sets. The hinge joint enables the bending of the chain around an axis through the respective links that is perpendicular to the running direction of the chain, which is indicated in  FIG. 1  by a double-headed arrow, hence an axis that projects out of the drawing plane and perpendicular to it relative to the representation of  FIG. 1 . 
     The teeth  3  have tooth flanks in the form of outer flanks  5  or  5 ′ and inner flanks  6  or  6 ′. The outer flanks  5  or  5 ′ and inner flanks  6  or  6 ′ have a convex profile and extend to a transition point  7  or  7 ′ in an indentation  8 . Indentation  8  can have different contours.  FIG. 1  shows both a contour  9  in accordance with the state of the art, as well as contours  10  and  11  in accordance with the invention. As can be seen, contour  9  of indentation  8  in accordance with the state of the art transitions smoothly into the profile of the inner flanks  6  and  6 ′ at transition points  7  and  7 ′, and a tangent lying on the profile of inner flank  6  or  6 ′ at transition point  7  or  7 ′, respectively, is identical to a tangent lying on the contour  9  of indentation  8  at transition point  7  or  7 ′. 
     Also shown in  FIG. 1  are two exemplary contour embodiments  10 ,  11  of indentation  8  in accordance with the invention. A first exemplary embodiment  10  of the contour in accordance with the invention is shown with a dashed line, a second exemplary embodiment  11  of a contour in accordance with the invention as a passing dashed line. The contours  10  and  11  in accordance with the invention no longer transition smoothly into the profile of the inner flanks  6 ,  6 ′ at the transition points  7  or  7 ′, but form an edge there, which can also be referred to as a contour break as also shown in the two-dimensional illustrations of  FIGS. 1 through 3 . The consequence of the contour break is that at least in some regions a convex curvature exists in the region of the transition point  7  or  7 ′. The transition point can be in the form of a sharp edge  16 , as shown in  FIG. 2 , but it can also be a smooth transition, for example in the form of a circular arc, a spline curve, or the like. 
     Also shown in  FIG. 1  are the distances between a plate top  15 , which in  FIG. 1  is the upper, straight boundary of the toothed plate, and the points of indentation  8  closest to the plate top  15 . The distances are designated here as Q 1  for a known contour  9  and for a contour  10  in accordance with a first embodiment in accordance with the invention, and as Q 2  for a contour  11  in accordance with a second exemplary embodiment in accordance with the invention. The distance Q can be changed through an appropriate choice of the contour  10  (for example like contour  11 ). At the plane of symmetry  12 , the tangents at contours  10 ,  11  are perpendicular to the plane of symmetry. 
     The design of the transition region between inner flanks  6 ,  6 ′ and indentation  8  is shown in greater detail in  FIGS. 2 and 3 .  FIG. 2  shows the left part of the toothed plate  1  shown in  FIG. 1  up to plane of symmetry  12 , shown in  FIG. 1  as a dashed line. In particular, the transition region between the inner flank  6  and the indentation  8  on both sides of transition point  7  will be explained on the basis of  FIG. 2 . The region identified in  FIG. 2  by a circle A is shown in enlarged form in  FIG. 3 . Transition point  7  is also designated in  FIG. 3  as point P 1  with the coordinates X 1  and Y 1 , in accordance with the X-Y coordinate system as shown in  FIG. 2 . The intersection of known contour  9  with the plane of symmetry  12  is designated in  FIG. 3  as P 2 , having the coordinates X 2  and Y 2 , and the intersection of contour  10  in accordance with the invention is designated as P 3 , having the coordinates X 3  and Y 3 . The X coordinate is the same for points P 2  and P 3 , because it is determined by the X coordinate of axis of symmetry  12 . 
     There is a difference in the values of the coordinate Y between the known contour  9  and the contour  10  in accordance with the invention, which difference can be varied as desired. As can be seen directly from  FIG. 3 , at point P 1  the tangent  14  to the known contour  9  of indentation  8  is identical to the tangent to the inner flank  6 . In contrast, at point P 1  the tangent  13  to the contour  10  in accordance with the invention of indentation  8  at transition point  7  forms an angle α with the tangent  14  to the inner flank  6  and to contour  9 . A positive angle α as shown in  FIG. 3  causes a convex curvature of the transition region around the transition point  7 . 
       FIG. 4  shows a different representation of the contour  10  shown in  FIG. 3 . Inner flank  6  and transition point  7  and contour  10  of the indentation  8  are shown. Tangential circles on contour  10  are shown as dashed lines. Singled out as examples are a first tangential circle with the radius R 1 ′ in the vicinity of the intersection of contour  10  with the axis of symmetry  12 , and a second tangential circle in the vicinity of transition point  7  with the radius R 2 ′. As can be seen, the center point M 1 ′ for the first tangential circle having the radius R 1 ′, and the center point M 2 ′ for the second tangential circle having the radius R 2 ′ do not coincide. Furthermore, the radii R 1 ′ and R 2 ′ and the radii of any other tangential circles lying between them are different. Such a curve can be shown for example as a so-called spline curve, in particular a B spline. 
     Alternatively, it is possible to produce the curve from individual discrete radii arranged in sequence, as shown in  FIG. 5 . The type of illustration shown in  FIG. 5  corresponds substantially to the type of illustration shown in  FIG. 4 . In contrast to contour  10  in the exemplary embodiment in accordance with  FIG. 4 , contour  10 ′ in accordance with the invention as shown in  FIG. 5  exhibits a stringing together of circle segments of various radii. Known contour  9  is shown again for comparison purposes. Contour  10 ′ includes the transitions  10 . 1 ,  10 . 2 , and  10 . 3  between circular arcs of various radii, which are designated as R 1  for the arc between the intersection of contour  10 ′ with the axis of symmetry  12  and transition point  10 . 1 , as R 2  for the arc between transition points  10 . 1  and  10 . 2 , as R 3  for the arc between transition points  10 . 2  and  10 . 3 , and as R 4  for the arc segment between transition point  10 . 3  and transition point  7 . Corresponding with the respective arc segments are center points M 1  through M 4 , with the same index numeral as the corresponding radius. As can be seen, the coordinates of the circular arc segment center points change. At the same time the radii, M 1  through M 4  in the present exemplary embodiment, can also remain constant. Preferably, there is provision for the radii to become progressively smaller, from radius R 1  to radius R 4 . Also in the exemplary embodiment in  FIG. 5 , a positive angle α exists, in accordance with the definition of angle α in  FIG. 3 . The constant radius R of contour  9  in the state of the art is also shown for comparison. 
     Although particular embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the present invention.