Abstract:
A mounting lever ( 1 ) according to one embodiment of the invention for dismantling a vehicle tire from a rim comprises a rod-formed handle portion ( 101 ) and a work portion ( 102 ) provided at its front end. The work portion ( 102 ) has a convex mounting surface ( 11 ).

Description:
TECHNICAL FIELD 
   The invention relates to a mounting lever for vehicle tires. 
   BACKGROUND OF THE INVENTION 
   Modern tires with emergency running properties have a reinforced tire wall and are used with rims comprising so called “extended humps.” Such tires must, on the one hand, carry at least a fourth of the vehicle weight, and may, on the other hand, not hop from the rim when driving with tire pressure that is too low. 
   To dismantle such tire from a rim, the tire is often claimed onto a disk machine. By use of a mounting lever, the heel of the tire is moved from the rim over a mounting head positioned at the wheel flange, which subsequently removes the tire from the rim supported by the rotational movement of the disk. To dismantle such tire from the rim, the heel of the tire must be pushed outwards with a force of approximately 600 N. With the commercially available mounting levers e.g. with the mounting lever known from the German Utility Model G 92 11 934.4, the heel of the tire is often damaged at the same time. 
   There is therefore a need for a mounting lever by use of which damages can be reliably avoided when dismantling a tire from the rim. 
   SUMMARY OF THE INVENTION 
   Such a mounting lever according to the invention comprises a rod-formed handle portion and a working portion provided at its front end having a convex profiled mounting surface. 
   According to a basic idea of the invention a mounting lever is appropriately profiled such that it comprises a convex mounting surface, which is capable in its use to avoid excessive tensions between mounting lever and heel of the tire. Thus damages when dismantling the tires are prevented. Such a mounting lever is suitable for the damageless dismantling of tires, especially of tires having a reinforced side wall. Cuts and pressure marks in the heel of tire which result from the use of commercially available mounting levers at the upper edges of the mounting lever due to strong punctiform stress are thereby reliably avoided. With conventional mounting levers, the heel of the tire rests with very low pressure between the corner points of the mounting lever, and no real form closure is accomplished. This effect does not depend in the first instance from the material strength of the used mounting lever, but rather mainly from its form. 
   When the curvature of the convex mounting surface or the profile of the cross section of the mounting lever approximately corresponds to the course of the edge of the heel of the tire when dismantling, damages when dismantling tires can be avoided even more reliably, since the heel of the tire is stressed at a point of time of the highest force effect uniformly over the whole width of the mounting lever and accordingly it results in a more homogeneous distribution of forces. Thus the pressure of the heel of the tire decreases and structural damages due to punctiform tensions of the heel of the tire especially at the edges of the mounting lever are avoided. 
   When a rounded end part is provided at the front end of the working portion, the mounting lever can be inserted particularly protectively between the rim and the heel of the tire, and the mounting lever does not damage the inner side of the running tread. 
   Tires can be mounted or removed particularly protectively, when the profile of the working portion changes towards its middle into another form and especially, when the handle portion of the mounting lever comprises a substantially rectangular profile, which changes in the working portion into a convex profile. 
   It is particularly advantageous, when the convex profile of the mounting lever changes in the working portion towards the rounded end part of the working portion into a substantially rectangular profile again. 
   Particularly protective for the tire is a mounting lever which is developed further according to the invention, in which mounting lever the convexity of the working portion changes over its length and in which mounting lever the convexity of the working portion is developed strongest in its middle. There the course of the convex mounting surface approximates the course of the edge of the heel of the tire. 
   In a further advantageous embodiment of the invention the mounting lever is angled slightly upwards at its front end. Thus the mounting lever can be inserted between the rim and the heel of the tire particularly well. In the normal case the mounting lever is straight, however an angled end makes sense as an embodiment. 
   In a further advantageous embodiment of the invention the mounting lever comprises only on one part of its working surface a profile corresponding to the course of the heel of the tire, and has a rectangular profile in the remaining part. 
   In a further advantageous embodiment of the invention the mounting lever is configured hook-formed at its back end. Thus the mounting lever can particularly well be held and fixed e.g. at the tire flange. 
   In a further advantageous embodiment of the invention the mounting lever is made of chrome vanadium, a particularly high quality material which lends the mounting lever advantageous characteristics, like immunity to corrosion and a particular solidity. 
   Recapitulating, it can be said that due to the various tire hardnesses and tire diameters as well as forms of mounting heads the profiling of the mounting lever can only be a matter of compromise, if not a separate mounting lever is to be provided for each single application. In the test of the most critical rim-tire-combinations, especially tires of dimensions 16, 18 and 20 inches with problematic steel and aluminum rims and tires that are particularly difficult to dismantle, it has been shown that the mounting lever profiled according to the invention works entirely without damages. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will be explained by means of the following description, wherein the Figures depict the following: 
       FIG. 1  is an isometric view of a disk machine that is being used to dismantle a tire from a rim using a mounting lever. 
       FIG. 2  is a top plan view showing an enlarged section from  FIG. 1 . 
       FIG. 3  is an isometric view showing a mounting lever according to one embodiment of the invention. 
       FIG. 4  shows a section of the mounting level of  FIG. 3  taken along the middle line in  FIG. 3  viewed towards the back end of the mounting lever. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   As shown in  FIG. 1 , a disk machine is being used to dismantle a tire  3  from a rim  2  using a mounting lever  1 . Such disk machines are known to the person skilled in the art. The tire  3  is clamped onto a rotatable disk (not shown in  FIG. 1 ) on which the tire  3  is placed. The disk machine includes a mounting head  14  having a gibbet. 
   To remove the tire  3  from the rim  2 , the front end of the mounting lever  1  is inserted between the rim  2  and the tire  3 . In doing so it is necessary for the tire  3  to rest in the base rim at the opposite side of the mounting head  14 . The tire  3  is subsequently lifted over the mounting head  14  by lowering the back end of the mounting lever  1  in the direction of the arrow B, such that it sits between the heel of the tire and a flange  7  of the wheel. After pulling out the mounting lever  1  down, the disk is rotated with the rim  2  in the direction of the arrow A to remove the tire  3  from the rim  2 . 
   The manner in which the mounting lever  1  engages the rim  2  and tire  3  to lift the tire  3  over the mounting head  14  is shown in greater detail in  FIG. 2 . The upper portion of  FIG. 2  also shows the tire  3  having a running tread  4 , a side wall,  5  and a heel  6 , which forms the lower edge of the side wall  5 . The lower portion of  FIG. 2  also shows the rim  2  and a wheel flange  7 , which limits the upward movement of the rim  2 . To dismantle the tire  3  from the rim  2 , the mounting lever  1  is inserted between the wheel flange  7  of the rim  2  and the heel  6  of the side wall  5  as shown in  FIG. 2 . The mounting head  14  engages the mounting level  1  and moves it to the right as shown in  FIG. 2  to lift the heel  6  of the tire  3  away from the rim  2  to create a space  8  between the rim  2  and the heel  6 . The heel  5  of the tire  3  rests on the mounting lever  1  along a curved line  12  between two corner points of support  9   a  and  9   b  at edges  1   a  and  1   b  of the mounting lever  1 . The heel  6  of the tire  3  applies substantial force to the lever  1  between the corner points  9   a  and  9   b . However, because the surface of the mounting lever  1  is curved, the pressure distribution between the heel  6  of the tire  3  and mounting lever  1  is more uniform across the face of the mounting lever  1  and thus preferable. In contrast, conventional mounting levers having flat surface tend to exert very high pressures at the corner points and very little pressure between the corner points. 
   The mounting lever  1  can be made of any suitable material, but is preferably made of chrome-vanadium. 
   The mounting lever  1  is shown in greater detail in  FIG. 3 . In the following description the designations “front/back” are related to the orientation along the x-axis, the designations “left/right” are related to the orientation along the y-axis and the designations “up/down” are related to the orientation along the z-axis of a Cartesian coordinate system  24 . The mounting lever  1  has a hook  13  at its back end, which can engage a wheel flange when mounting a tire on a wheel without the use of a disk machine. The mounting lever  1  has a handle portion  101  adjacent thereto, which extends into the front third of the mounting lever  1 . In the embodiment shown in  FIG. 1 , the handle portion  101  has a rectangular profile. 
   A working portion  102  is located adjacent to the handle portion  101  in the front part of the mounting lever  1 . The front end of the working portion  102  is formed by a rounded end part  10 , which, in the embodiment shown, is configured trapezoidally. The trapezoidal shape of the end part  10  allows the mounting lever  1  to more easily be inserted between the wheel flange  7  and the heel  6  of the tire  3 . 
   Behind the end part  10 , the working portion  102  has a mounting surface  11  that is convex at the middle of the working portion  102  along line  12  so that the height of the mounting lever  1  at the middle of the working portion  102  is lowest at its sides  1   a  and  1   b  and greatest in its middle. However, the mounting surfaces changes from convex at the middle of the working portion  102  to a substantially rectangular profile towards the rounded end part  10  of the working portion  102 . Thus, the convexity of the profile of the mounting surface  11  of the working portion  102  changes over its length, and it is greatest in the middle of the working surface  102  along line  12 . Shaping the mounting lever  1  in this manner prevents the heel  6  of the tire  3  from slipping off the mounting lever  1  during use of the mounting lever  1 . Furthermore, the convex profile of the mounting surface  11  allows the heel  6  of the tire  3  to rests with a more uniform force on the entire width of the mounting lever  1 . 
   The convex curvature of the mounting surface  11  is shown more clearly in  FIG. 4 , which shows a section along the line  12  in  FIG. 3  looking away from the end portion  10  of the mounting lever  1 . A second coordinate system  15  serves for a better orientation, the x-axis of which running vertically to the drawing plane. The edges  1   a ,  1   b ,  1   c  and  1   d  form the rectangular profile of the mounting lever  1  away from the line  12 . The transition between adjacent edges is rounded at the same time. The lines  13   a  and  13   b  depict the upper and the lower edges of the hook  13 , respectively, which is masked in this illustration. The convex curvature of the mounting surface  11  along line  12  is readily apparent in  FIG. 4 . 
   From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.