Abstract:
Disclosed is a grinding tool for a grinder comprising a rotary oscillating drive, the output shaft of which is driven so as to oscillate back and forth about its longitudinal axis and is configured for securing the grinding tool thereon. The grinding tool comprises a grinding pad which is made of a resilient material and encompasses at least one grinding surface that runs straight in one direction of extension and parallel to a tangent to the output shaft of the rotary oscillating drive.

Description:
RELATED APPLICATIONS 
   This application is a continuation application of co-pending International Patent Application PCT/EP2003/014278 filed on Dec. 16, 2003 which designates the United States and claims priority of German patent application 103 08 600.5 filed on Feb. 27, 2003 and being fully incorporated by reference herewith. 

   BACKGROUND OF THE INVENTION 
   The invention relates to a grinding tool for a grinder comprising a rotary oscillating drive, the output shaft of which is oscillatingly driven about its longitudinal axis and comprises a support for mounting the grinding tool thereon, wherein the grinding tool comprises a receptacle configured for connecting with the support of the grinder for grinding in an operating position. 
   Such a grinder is known from EP-B-0 244 465. 
   The known grinder comprisese a rotary oscillating drive the output shaft of which is oscillatingly driven about its longitudinal axis at high frequency and with a small pivot angle. To the output shaft of the oscillating drive a grinding tool usually having triangular or rectangular space surface is secured, whereon a grinding surface is provided which extends within a plane perpendicular to the longitudinal axis of the output shaft. A sanding paper or the like may be fixed on the grinding tool by means of a Velcro tape by means of a clamping fixture and may also surround the front face of the grinding tool. 
   The grinder may advantageously be worked into corner regions when using a triangular grinding surface. The curvature of the grinder tool allows the front face to effectively work along a straight edge. 
   However, in some cases a grinding of longitudinal profiles is desired, wherein the grinding motion shall be performed mainly in a longitudinal direction. 
   For such a grinding the known grinder is not suitable. 
   From EP-A-0 726 121 a grinder comprising a grinding tool extending straight is known. However this grinding tool is not driven rotatingly oscillating about a fixed output shaft, but is oscillated back and forth in a longitudinal direction. Thus, the different profiles can be moved back and forth like in a manual operation of a grinding pad. 
   SUMMARY OF THE INVENTION 
   Thus it is a first object of the invention to disclose a grinder having a rotating oscillatory drive which allows for a grinding along longitudinal edges with only little vibrations. 
   It is a second object of the invention to disclose a grinder having a rotating oscillatory drive which allows for a grinding of profiles and the like. 
   It is a third object of the invention to disclose a grinder having a rotating oscillatory drive which allows for a grinding along longitudinal edges with a high removal rate. 
   It is a fourth object of the invention to disclose a grinding tool for a grinder having a rotating oscillatory drive which allows for a grinding along longitudinal edges with only little vibrations. 
   These and other objects of the invention are achieved with a grinding tool as mentioned at the outset in that the grinding tool comprises an elastic grinding pad having at least one grinding surface which extends straight in one direction and parallel to a tangent to the mounting opening of the output shaft of the oscillating drive and further extends at an angle to a plane defined by the securing section of the grinding tool. 
   Thus the object of the invention is completely achieved. 
   Namely, according to the invention it is now made possible to grind using a grinding surface extending straight in one direction and parallel to a tangent of the output shaft of the oscillating drive. 
   By means of the elastic material of the grinding pad it is ensured herein that strong vibrations of the grinding tool are avoided, even in view of the fact that the grinding surface extends straight at least in one direction. 
   The elastic design of the grinding pad negates vibrations and pushes resulting from the straight design of the grinding surface. Thus with such a grinder numerous grinding operations along longitudinal profiles can be performed. Herein the cross-section of the grinding pad can be adapted to the particular shape of the surface profile to be ground. Thus, a higher removal rate up to 5-fold when compared with the prior art can be reached. 
   According to an advantageous development of the invention the grinding tool comprises securing means for securing a grinding means, in particular a sanding paper, to the grinding pad. 
   The respective grinding means may be replaced but the grinding pad itself does not need to be chanced in the short term. 
   According to another advantageous design of the invention the grinding pad is made of a rubber-elastic material. 
   In this way the necessary elasticity or yielding characteristic of the grinding pad can be reached in a particular advantageous way. 
   According to another design of the invention the grinding surface is bent in a second direction perpendicular to the first extending direction. 
   In this way the surface of the grinding pad can be matched to numerous profiles to be ground. 
   According to another advantageous design of the invention the grinding pad has a hollow cross-section. 
   In this way a particular advantageous elasticity or yielding characteristic of the grinding pad can be reached. 
   According to another design of the invention the grinding tool comprises a securing section having a receptacle for connecting with the support of the output shaft and being followed by a holding section within which the grinding pad is held. 
   Herein the receptacle is preferably configured as a mounting opening. 
   In this way the grinding tool can be directly attached to the output shaft of the oscillating drive with the receptacle or mounting opening, respectively, e.g. by using a screw. 
   According to an advantageous development of the invention the holding section tapers from the securing section toward the mounting section. 
   In this way a grinding pad having a greater length can be mounted on the output shaft. 
   According to another design of the invention the holding section comprises a recess within which the grinding pad is held with a holding section and from which the holding pad protrudes to the outside with a working section whereon the grinding surface is formed. 
   In this way a safe mounting and simple assembly on the grinding section is ensured. 
   According to another design of the invention on both sides of the holding section clamping means are provided for securing a sanding paper guided around the grinding pad by clamping. 
   According to an additional development of this design on each side of the holding section a pivot lever is mounted which is biased against the holding section. 
   Thus a sanding paper can be fixed to the grinding pad in a particularly simple and fast way. 
   According to another design of the invention two slots are provided within the holding section for receiving the ends of a sanding paper guided around the grinding pad. 
   According to an additional development of this design at least one clamp is insertable into the holding section for securing a sanding paper guided around the grinding pad. 
   Also when using such a design, a simple and fast attachment of a sanding paper to the grinding pad can be reached. Since herein no pivot levers are necessary, by contrast only a clamp serving for securing the sanding paper, a particularly cost-effective design is reached. 
   According to an additional development of this design the at least one clamp is insertable with springable sections into insert openings on both sides of the holding section for bracing the sanding paper against the walls of the slots. 
   In this way a safe fixation of the sanding paper to the grinding pad is ensured. 
   According to a further design of the invention on both sides of the holding section a respective clamping lever is mounted pivotably and can be braced against the holding section in a clamping position for securing a sanding paper guided around the grinding pad. 
   In this way the clamping levers themselves may be used for bracing against the holding section so that the utilization of additional springs for generating the bracing force becomes superfluous. Simultaneously also the grinding pad is clamped in a simple way when biasing the clamping lever against the holding section. 
   As already mentioned above, the grinding tool can be used advantageously for grinding longitudinal profiles by means of a rotary oscillating drive the output shaft of which is oscillatingly driven about its longitudinal axis, wherein the grinding tool is mounted on the rotary oscillating drive, so that the at least one grinding surface extends tangentially to the output shaft. 
   It will be understood that the features of the invention mentioned above and to be explained hereinafter cannot be used only in the respective given combination, but also independently or in other combinations, without going beyond the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the invention can be taken from the following description with reference to the drawings. In the drawings show: 
       FIG. 1  a cross-section of a first embodiment of a grinder according to the invention, wherein an associated oscillatory drive, to which the grinding tool is affixed, is depicted schematically; 
       FIG. 2  a perspective view of the grinding tool according to  FIG. 1 , seen obliquely from one side; 
       FIG. 3  an enlarged partial representation of the grinding tool according to  FIG. 1 , shown in the region of a clamp which serves for mounting the sanding paper; 
       FIG. 4  a perspective representation of a different embodiment of a grinding tool according to the invention, seen obliquely from above; 
       FIG. 5  a cross-sectional view of a slightly modified embodiment of the grinding tool according to  FIG. 4 , shown in reduced representation; and 
       FIG. 6  a perspective view of a further embodiment of the grinding tool according to the invention, according to which two clamping levers are provided for clamping attachment of a sanding paper under the action of a spring force generated by the clamping levers themselves. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A first embodiment of the grinder according to the invention is shown in  FIG. 1  and depicted in total with numeral  10 . The grinder  10  comprises a rotary oscillating drive  12 , merely depicted schematically with numeral  12 , which oscillatingly drives an output shaft  14  about its longitudinal axis  16  with a small pivot angle between about 0.5 and 7° and at a high frequency between about 5000 and 25000 oscillations per minute (cf. double arrow  18 ). 
   On the output shaft  14  a support for mounting a grinding tool  20  is provided which, e.g., may be configured simply as a threaded blind hole by means of which the grinding tool  20  is affixed using a screw  25  extending through a mounting opening  24  of the grinding tool  20 . 
   It will be understood that any kind of support may be provided for connecting the grinding tool  20  with the output shaft  14 . For instance, also positively shaped supports may be used, such as by means of a hexagon or the like. 
   In  FIG. 1  the grinding tool  20  is shown in a longitudinal section through the mounting opening  24 . 
   The grinding tool  20  which can be seen in  FIG. 2  in a perspective view obliquely from the front comprises a securing section  22  which is formed unitary with a holding section  26  which is shaped substantially cuboid. The securing section  22  is formed by a plate which tapers from the holding section  26  into the direction of the mounting opening  24 , the plate extending around the mounting opening  24  substantially triangular with an angle of about 60° and being rounded thereabout in the region of the mounting opening  24 . The holding section  26  extends in the extension of the securing section  22 , however is enlarged with respect to the securing section  22  by a multitude, e.g. 5-fold. In the center of the holding section  26  a recess  36  shaped as a longitudinal slot is provided within which a grinding pad  28  is received with a holding section  38 . The grinding pad  28  protrudes from the recess  36  to the outside with a working section  40 . 
   The grinding pad  28  is made of a rubber-elastic material, such as of nitrile butadien rubber and is formed hollow-shaped with its working section  40  which protrudes from the holding section  26  to the outside, namely, is penetrated in the longitudinal direction by an opening  41 . The grinding pad  28  which enlarges from its substantially cuboid shaped holding section  38  to the outside at both edges with an acute angle finally extends on both lateral edges, starting from a rim shaped in this way, toward a common tip  43  which encloses a corner angle of about 80 to 90°. In a direction perpendicular to the drawing plane of  FIG. 1  the grinding pad  28  extends straight and is arranged tangentially to the longitudinal axis  16  of the drive shaft  14  of the oscillatory drive  12 , when being in the shown working position. 
   Thus the grinding pad  28  moves tangentially to the drive shaft  14  when working with the oscillatory motion of the drive shaft  14 . 
   Thus by means of the triangular shaped or roof-shaped outer surface of the grinding pad  28 , which extends toward the tip  43 , a grinding surface  29  is formed which is moved oscillatingly back and forth in the tangential direction of the drive shaft  14 . 
   While it would be basically possible to design the grinding surface  29  itself as a grinding means, e.g. by incorporating grinding particles or the like, it is preferred to guide a sanding paper or the like around the grinding surface  29  and to secure the sanding paper at its both ends to the holding section  26  of the grinding tool  20  removably. To this end in the holding section  26  two slots  32 ,  34  are provided which extend in parallel to the recess  36  shortly before the outer surface of the holding section  26  and which allow to guide both ends of the sanding paper  30  therethrough. A clamp  42  is provided for securing the sanding paper  30  at its both ends. The clamp  42  is basically U-shaped and can be inserted with its two legs into insert openings extending in parallel to the slots  32 ,  34 . It can be seen from the enlarged representation of  FIG. 3  that the respective leg  44  is designed corrugated and is held in the respective insert opening  45  for clamping the sanding paper  30  with its corrugated edges toward the outside against the wall of the respective slot  34 . 
   In case the sanding paper  30  shall be exchanged, then merely the clamp  42  must be retracted to the outside. Then the sanding paper  30  can be removed and be replaced with a new piece of sanding paper. The two ends of which again are inserted through the slots  32 ,  34 , and now the clamp  42  is again inserted with its two legs  44  into the respective insert openings to clamp the sanding paper  30  within the slots  32 ,  34  thereby. 
   It will be understood that the shape of the grinding pad  28  shown in  FIGS. 1 and 2  is of merely exemplary nature and that the grinding pad may resemble any kind of profile shape, so that a grinding of longitudinal profiles is made possible with any desired shape. 
   Due to the yielding design of the grinding pad  28  herein a grinding with relatively small vibrations is made possible in an effective way, even in view of the grinding surface  29  which is planar in the longitudinal direction (tangential direction). 
   In  FIGS. 4 ,  5  and  6 , respectively, further embodiments of the grinding tool  20  are shown and depicted in total with numerals  20   a ,  20   b  and  20   c . These differ from each other generally by using different receiving or mounting means, respectively, for mounting a sanding paper  30  on the grinding pad  28 . 
   Herein corresponding reference numerals are used for corresponding parts. 
   In the grinding tool  20   a  according to  FIG. 4 , two pivot levers  46 ,  48  are used for securing the two ends of the sanding paper  30 , the pivot levers being arranged pivotably about pivot axes  62 ,  64 , and which are biased by springs  50 ,  52 , respectively, arranged between the two pivot levers  46 ,  48 . Thus the two ends of the sanding paper  30  are pressed into respective recesses  58 ,  60  or longitudinal grooves of the holding section  26  by means of protrusions  54 ,  56  of the pivot levers  46 ,  48  and are clamped by means of the spring tension. 
   The outer surface of the working section  40  of the grinding pad  28  differs in its shape from the form described above with reference to  FIG. 1  in that it does not taper in an acute angle toward the outer end, but is formed with a sector of a circle. This grinding pad  28  is thus configured for grinding rounded longitudinal profiles. 
   In  FIG. 5  an embodiment of the grinding tool, which is slightly modified with respect to the design according to  FIG. 4 , is shown in longitudinal section and depicted in total with numeral  20   b.    
   Herein the design largely corresponds to the design according to  FIG. 4 . The only difference rests in the shape of the working section  40  of the grinding pad  28 , the working section again fully corresponding to the shape previously described with reference to  FIG. 1 . 
   A further embodiment of a grinding tool according to the invention is shown in  FIG. 6  and depicted in total with numeral  20   c.    
   The shape of the grinding pad  28  again corresponds to the shape of the grinding pad  28  according to  FIG. 4 . 
   For securing the sanding paper which again is guided around the grinding pad  28 , again two pivotable levers are provided which, however, are not under the action of springs, but can be clamped directly against steps  74 ,  76  of the holding section  26 , due to its design as wire clamps, thus generating a clamping action without the use of additional springs. To this end in the holding section  26  recesses  70 ,  72  shaped as longitudinal grooves are provided on both sides allowing to insert the ends of a sanding paper. If the two clamping levers  66 ,  68  are closed thereafter, then they will be clamped at the end of the holding section  26  opposite the securing section  22  by means of its S-shaped holding sections  82 ,  84  against steps  74 ,  76 . In this position in the direction of the recesses  70 ,  72  or of the longitudinal grooves, respectively, clamping sections  78 ,  80  of the clamping levers  66 ,  68  are biased by means of the tension of the clamping levers  66 ,  68  against the inner surface of the respective recesses  70 ,  72  or longitudinal grooves, respectively, thus clamping and securing the ends of a sanding paper thereto.