Patent Publication Number: US-7214010-B2

Title: Tool bit holder and hand power tool

Description:
CROSS-REFERENCE 
   The Invention described and claimed hereinbelow is also described in DE 10 2005 010 265.4, filed Mar. 7, 2005. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119 (a)–(d). 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a tool bit holder and to a hand power tool. 
   For heavy drill hammer and/or chisel hammers, until now, for the sake of stability automatic locks of the kind known for lightweight drill hammers have not been used. In heavy drill hammer and/or chisel hammers, whichever tool bit insert is inserted into the tool bit holders has been locked and unlocked by hand, using a blocking device actuatable from outside the tool bit holder. 
   In German Patent Disclosure DE 101 05 406 A1, a tool bit holder with automatic locking has been proposed that is especially suitable for drill hammer and/or chisel hammers. The tool bit holder has a blocking bolt, located transversely to the longitudinal axis of a basic body of the tool bit holder, as its locking body, which is movably supported in a guide path, and in which the blocking bolt, for locking a tool bit shaft, can move toward the tool bit shaft and for releasing and removing the tool bit shaft can move away from the tool bit shaft. The guide path extends in the basic body and continues in a slide sleeve that surrounds the basic body. The blocking bolt locks the tool bit shaft by engaging a recess on the tool bit shaft. For the release, the slide sleeve and the basic body are aligned with one another such that the blocking bolt can escape out of the recess outward along the guide path. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide a tool bit holder and also a hand power tool, which eliminate the disadvantages of the prior art. 
   The invention is based on a tool bit holder for a hand power tool, in particular a drill hammer and/or chisel hammer, which is drivable in hammering and/or rotating fashion, having a tool bit holder body with a receiving bore for a tool bit shaft of a tool bit insert with at least one recess, in which at least one locking body capable of being snapped into place for the recess of the tool bit shaft is supported radially displaceably in the tool bit holder body and is operatively connected in such a way to a slide sleeve, supported resiliently in the axial direction, that upon a motion of the slide sleeve counter to a spring force, the locking body escapes out of the receiving bore. 
   It is proposed that the locking body is caught in a first opening of the tool bit holder body and in a second opening, at least partially covering the first opening, of a guide ring supported displaceably on the tool bit holder body. 
   As a result, an automatic tool bit holder for hammers with a splined shaft or hexagonal tool bit inserts of more than 15 mm in diameter, in particular, is created. The tool bit holder is economical, simple, and lightweight. The invention combines the simplicity of an automatic tool bit holder having a locking ball with the wear resistance of a blocking bolt tool bit holder. By setting the locking body in the guide ring, tilting of the locking body is reliably avoided. Sliding of the locking body in an oblique guide conduit in the tool bit holder body and in the slide sleeve can be avoided. The locking body can have a larger size than is the case with a locking bolt. The risk of canting is reduced. 
   Stable, automatic locking of the tool bit insert is successful if the locking body, in the locking position of the tool bit shaft, is compartmented by a locking ring in the first and second openings. Preferably, the locking ring is located in a groove in the slide sleeve. Favorably, the locking ring, on its outer faces oriented toward the locking body, has flanks that are adapted at least in their inclination to the locking body in its respective installed position, that is, upon insertion of the tool bit shaft of the tool bit insert into the receiving bore or upon removal of the tool bit insert. 
   If the locking body for locking the tool bit shaft is displaceable with the guide ring in the insertion direction of the tool bit shaft, then the tool bit insert can be inserted in a simple way, as in an automatic tool bit holder with a locking ball. Expediently, the guide ring is displaceable counter to a spring force of a locking spring. A suitable protrusion on the tool bit shaft can push the locking body with the guide ring in the insertion direction without the slide sleeve having to be actuated, until the locking body can escape outward into a hollow chamber that is provided. 
   For removal of the tool bit, the slide sleeve is preferably displaceable in the insertion direction of the tool bit shaft such that the locking body escapes into a hollow chamber uncovered by the locking ring as it is entrained with the slide sleeve. The tool bit can easily be removed without major effort. 
   Preferably, the locking body is a locking cylinder, extending transversely to the longitudinal axis of the tool bit holder body. This locking cylinder essentially has the form of an ellipsoid, so that its contours are very well rounded. As a result, as the guide ring and/or locking ring and/or slide sleeve moves, the locking body can easily slide into its intended position. This makes the power tool easier for the user to manipulate while he is changing tool bits. Advantageously, the locking body corresponds in its length perpendicular to the longitudinal axis approximately to the diameter of the receiving bore. 
   The invention is further based on a hand power tool, in particular a drill hammer and/or chisel hammer, having a tool bit holder, which is drivable in hammering and/or rotating fashion, having a tool bit holder body with a receiving bore for a tool bit shaft of a tool bit insert with at least one recess, in which at least one locking body capable of being snapped into place for the recess of the tool bit shaft is supported radially displaceably in the tool bit holder body and is operatively connected in such a way to a slide sleeve, supported resiliently in the axial direction, that upon a motion of the slide sleeve counter to a spring force, the locking body escapes out of the receiving bore. 
   It is proposed that the locking body is caught in a first opening of the tool bit holder body and in a second opening, at least partially covering the first opening, of a guide ring supported displaceably on the tool bit holder body. 
   Further embodiments, aspects, and advantages of the invention will become apparent, even independently of how they are summarized in claims and without limiting the generality, from an ensuing exemplary embodiment of the invention described in conjunction with drawings. 
   The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal section through one region of a preferred hand power tool with a preferred tool bit holder, 
       FIG. 2  is a section through the preferred tool bit holder taken along the line II—II in  FIG. 1 , and 
       FIG. 3  is a top view on the preferred tool bit holder of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  in longitudinal section shows a preferred tool bit holder for a hand power tool, in particular a heavy drill hammer and/or chisel hammer, which can be driven in hammering and/or rotating fashion. The tool bit holder  10  has a tool bit holder body  11  with a receiving bore  12  for a tool bit shaft  13  of a tool bit insert. At least one recess  14  is provided on the tool bit shaft  13  and can be engaged or snapped into by a locking body  15 , which is radially displaceably supported in the tool bit holder body  11 . 
   The locking body  15  is operatively connected in such a way that a slide sleeve  16 , supporting resiliently in the axial direction by a spring  18 , that upon a motion of the slide sleeve  16  counter to the spring force of the spring  18 , the locking body  15  escapes out of the receiving bore  12  into a hollow chamber  33 . The spring  18 , embodied as a helical spring, is located between an indentation  22  in the slide sleeve  18  and an abutment  21  on an element that surrounds the tool bit holder body  11 . 
   The locking body  15  is caught in a first opening  19  in the tool bit holder body  11  and in a second opening  29  of a guide ring  20 , supported displaceably on the tool bit holder body  11 , which second opening at least partly covers the first opening  19 . The second opening  29  is embodied as smaller than the first opening  19  in the axial direction, relative to the longitudinal axis  28  of the tool bit holder body  11 . 
   The locking body  15  is embodied as a locking cylinder, which extends transversely to the longitudinal axis  28  of the tool bit holder body  11  and is approximately in the form of an ellipsoid. In its length perpendicular to the longitudinal axis  28 , the locking body  15  is approximately as long as the diameter of the receiving bore  12 . The slide sleeve  16  can therefore be embodied as rotationally symmetrical on both the inside and the outside, since the locking body  15  does not engage the inside of the slide sleeve  16 . The curvature of the locking body  15 , embodied as a locking cylinder, conforms to the inner circumference of the locking ring  25  ( FIG. 2 ). 
   Toward the end of the tool bit, the hand power tool is closed off with a closure element  24 , which is axially fixed by a locking ring  23  on the tool bit holder body  11 . 
   In the locking position of the tool bit shaft  13 , the locking body  15  is compartmented by a locking ring  25  and the boundaries of the first and second openings  19 ,  29 . The locking ring  25  is located in a groove  30  in the slide sleeve  16 , so that upon an axial motion of the slide sleeve  16 , the locking ring is entrained with it. 
   The locking ring  25 , on its outer faces toward the locking body  15 , has flanks  34 ,  35  that at least in their inclination are adapted to the locking body  15  in its applicable installed position, so that upon the corresponding actuation of the locking body  15 , escaping out of the recess  19  or sliding back into the recess  14  is facilitated. 
   The locking body  15  can be used like a simple locking ball in a simple SDS tool bit holder. SDS originally stood for Steck-Dreh-Sitzt [“Insert-Turn-Sits”] or “Special Direct System”, and is used particularly in hammers with a 10 mm shaft diameter for drilling and/or hammering tool bit inserts for lightweight hand power tools of up to 4 kg in weight. Upon automatic locking of the tool bit insert or its tool bit shaft  13 , the locking body  15  is thrust with the guide ring  20  by a protrusion of the tool bit shaft  13  in the insertion direction, that is, to the rear, counter to the spring force of a locking spring  17 . 
   The locking spring  17  is located between a collar  26  of the guide ring  20 , which collar acts as an abutment and is folded over to the outside, and an indentation  27  in the same element that also forms the abutment  21  of the spring  18 . The locking body  15  slides away beneath the locking ring  25  and is released because it can escape into a hollow chamber  32  in the insertion direction downstream of the locking ring  25 . As a result, the tool bit shaft  13  can be introduced unhindered into the receiving bore  12 . Once the tool bit shaft  13  has been fully inserted, the locking body  15  is thrust back forward by the locking spring  17 , counter to the insertion direction, between the locking ring  25  and the recess  14  in the tool bit shaft  13  and in the process locks the tool bit insert. 
   For removal of the tool bit insert, the slide sleeve  16  is thrust by the user to the rear, in the insertion direction. The locking ring  25  is entrained in the process. As a result, the locking body  15  is released and can escape outward into the hollow chamber  33 , which is located upstream of the locking ring in terms of the insertion direction, and the tool bit shaft  13  can easily move past with its protrusion, and the tool bit insert can be removed. 
     FIG. 2 , for illustrating the disposition of the preferred tool bit holder  10 , shows a cross section taken along the line II—II in  FIG. 1 , while  FIG. 3  shows a plan view from above. The advantageously small dimensions of the locking body  15 , embodied as a locking cylinder, and its rounded, ellipsoid-like form are clearly visible. It is also clearly visible that the locking body  15  does not engage the inside of the slide sleeve  16 , which can therefore be manufactured with less production effort than if a guide path had to be machined into it. Furthermore, the slide sleeve  16  can be relatively thin-walled, since it need not furnish a minimum wall thickness for a stable guide path. 
   It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
   While the invention has been illustrated and described as embodied in, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of reveal present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of the invention.