Patent Publication Number: US-2012038119-A1

Title: Tool holder

Description:
FIELD OF THE INVENTION 
     The present invention relates to a tool holder for a chipping hammer. 
     DESCRIPTION OF THE PRIOR ART 
     Tool holders with a lock for chipping hammers are known from EP 1 872 913 A2, among other places. The tool holder may accommodate two of the conventional designs for tools and secure the tools by setting a bar. Provision is also made for the bar to be locked in a position in which the tool may be inserted in the tool holder or may be removed from it. 
     The bar is fastened on a rotatable shaft by means of pins. Strong forces act on the pins during the percussive operation of the chipping hammer. As a result, the pins are manufactured of highly resistant materials. 
     DISCLOSURE OF THE INVENTION 
     One object is making another tool holder available. 
     The tool holder according to the invention for a chipping hammer has a tool receptacle for receiving a tool and a tool securing device for securing the tool in the tool receptacle. The tool securing device has a shaft having an eccentrically arranged mandrel and at least one end piece and a bar having at least one eye, into which the end piece engages in a form-fitting manner. The eye has a non-circular cross-section. The tool securing device can be pivoted into at least one first position for inserting and removing the tool and into at least one second position for securing the tool. 
     The non-circular cross-section of the eye and of the end pieces, which preferably conform to one another, ensures that the bar and shaft cannot twist relative to each other. 
     The forces that occur during impact are introduced to the shaft essentially over the entire circumference of the eye. This may result in low levels of stress to the materials. 
     The end piece preferably has a larger cross-section than the shaft between the end pieces. The tool holder may have a bearing for mounting the shaft, with a cross-section of the bearing being the same as a cross-section of the end pieces. This facilitates a simple assembly. The shaft is inserted into the bearing and the bar is placed on the shaft. Additional fastening with pins may be omitted. 
     According to one embodiment, the bar has a contour line perpendicular to the shaft, the contour line having four rectilinear sections, and a flat stop face is provided; in each of the first and second positions, one of the four rectilinear sections rest on the flat stop face. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The following description explains the invention on the basis of exemplary embodiments and figures. 
         FIG. 1  illustrates an embodiment of a tool holder; 
         FIG. 2  illustrates another embodiment of a tool holder; and 
         FIGS. 4 to 10  are longitudinal sections through the tool holder in  FIG. 1  or  FIG. 2 . 
     
    
    
     Unless otherwise indicated, the same or functionally equivalent elements are identified by the same reference characters in the figures. 
     EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows an exploded view of an embodiment of a tool holder. The tool holder is constructed for holding tools  2 , e.g., a chisel for a chipping hammer. 
       FIG. 2  shows an exploded view of another embodiment of a tool holder. 
     The longitudinal sections in  FIGS. 3 to 6  depict a position for locking a tool of the first design in one of the tool holders and a position for inserting and removing the tool from the tool holder. 
     The longitudinal sections in  FIGS. 7 to 10  show a position for locking a tool of the second design in one of the tool holders and a position for inserting and removing the tool from the tool holder. 
     The tool holders  1  are constructed for accommodating tools, in particular chisels. The known chisels  2  have two different designs with respect to how they are secured in a tool receptacle  4 . The first design of the tool  2  is depicted schematically in  FIGS. 1 to 6 . The essentially cylindrical tool  2  has an annular collar  5 . The tool holder  1  has a bar  6 , which partially grips around the tool  2  behind the collar  5  in the impact direction  7  in such a way that the bar  6  forms a limit stop for the collar  5  in the impact direction  7 . A front section  8  of the bar has instead a semi-circular contour, which can grip around the tool  2  next to the collar  5 , but has a smaller diameter than the collar  5 . 
     The second design of the tool  12  is depicted in the longitudinal sections in  FIGS. 7 to 10 . The tool  12  has a longitudinal groove  13  along a shaft of the tool  12 , in which a mandrel  15  of the tool holder  1  may engage. 
     The bar  6  and the mandrel  15  are arranged pivotably around an axis in order to be able to remove/insert the tool  2 ,  12  from/into the tool holder  1  and lock it. 
     The mandrel  15  is arranged on a shaft  16 . The shaft  16  is inserted into a bearing  17 , in which the shaft  16  is freely rotatable. The shaft  16  has a circular cross-section within the bearing  17 . On its two ends, the shaft  16  has two end pieces  18  having a non-circular cross-section. The cross-section of the end pieces  18  may have a greater surface area than the cross-section within the bearing  17 . 
     The bar  6  is connected to the shaft  16  in a form-fitting manner. Two eyes  19  are positioned laterally in the bar  6  into which the end pieces  18  of the shaft  16  are inserted. The cross-section of the end pieces  18  corresponds to the cross-section of the two eyes  19 . The non-circular cross-sections ensure that the bar  6  cannot be twisted relative to the shaft  16  without requiring fastening or securing pins. Thus, pivoting the bar  6  causes the shaft  16  to rotate. 
     The bar  6  has a contour line  20  having four sections  21 ,  22 ,  23 ,  24 . The contour line  20  runs perpendicular to the shaft  16 , with the center of each of the sections  21 ,  22 ,  23 ,  24  being at approximately the same distance from the shaft  16 . Arranged on the bearing  17  is a block  25 , which has a flat surface  26 . The contour line  20  and the block  25  are constructed in such a way that four positions of the bar  6  result in which the bar  6  engages on the block  25 . The four engagement positions will be depicted on the basis of  FIGS. 3 to 10 . 
       FIGS. 3 and 4  show a first engagement position for releasing the first tool  2 . The contour line  20  has a rectilinear section  21 , which is adjacent to the flat surface  26  of the block  25 . A pure rotation around the shaft  16  is prevented by the rectilinear arrangement. 
       FIGS. 5 and 6  show a second engagement position for securing the first tool  2 . A path of the tool  2  in impact direction is limited by the collar  5  through the front surface  8  of the bar  6 . The contour line  20  has a second rectilinear section  22 , which is adjacent to the flat surface  26  of the block  25 . A pure rotation around the shaft  16  is prevented by the rectilinear arrangement. 
       FIGS. 7 and 8  show a third engagement position for releasing the second tool  12  with a longitudinal groove  13 . The eccentrically arranged mandrel  15  does not engage in the longitudinal groove  13 . The contour line of the bar  6  is adjacent to the block  25  engaged with the third section  23 . 
       FIGS. 9 and 10  show a fourth engagement position for securing the second tool  12 . The eccentrically arranged mandrel  15  engages in the longitudinal groove  13  and limits the motion of the tool  12  in the impact direction  7 . The fourth section  24  is rectilinear and abuts the flat block  25 , whereby the bar  6  engages. 
     Pivoting the bar  6  out of an engaged position is accomplished by an elastic mounting of the shaft  16  in the bearing  17 . The bearing  17  is designed to be oblong in a direction perpendicular to the axis of shaft  16  in such a way that the shaft  16  is displaceable in this direction. A ring  30  made of an elastic material holds the shaft  16  in a central position of the bearing  17 . The ring  30  may support itself on the tool holder  1  or on the bearing  17  in a circular receptacle  31 . 
     When the bar  6  is pivoted, the elastic ring  30  is squeezed until a subsequent engagement position is reached by a planar contact of one of the rectilinear sections  21 ,  22 ,  23 ,  24  on the flat surface  26 . 
       FIG. 2  depicts an embodiment in which, instead of or in additional to the contour line  20 , projections  40  or crosspieces are provided on the bar  6 , which can engage in corresponding depressions  41  or pockets on the tool receptacle  1 . The profile of the projections and depressions is aligned along the shaft  16 . The depressions or associated projections may be arranged at different angles around the shaft  16  such that the bar correspondingly has four engagement positions. The depressions  41  may be placed in an elastic element  42 , which is supported perpendicularly against the tool receptacle  4 .