Abstract:
A power tool having a receptacle for securing a tool to a drive shaft thereof is disclosed. The receptacle comprises a receiving opening, preferably being arranged on the tool. The receiving opening engages a securing section preferably being provided in a raised fashion on the drive shaft of the power tool, thereby effecting a positive fit. The securing section comprises a plurality of rounded tips arranged at even radial distances from said longitudinal axis, at angular intervals between each other, each rounded tip having a pair of lateral flanks extending from a common apex toward an intermediate section connecting lateral flanks of a pair of adjacent rounded tips. Preferably the receiving opening comprises a number of rounded tips which is twice the number of rounded tips provided on the raised section.

Description:
RELATED APPLICATIONS 
   This application is a continuation-in-part application of U.S. patent application Ser. No. 10/003,645 filed Nov. 2, 2001, now U.S. Pat. No. 6,796,888 claiming priority of German patent application serial number 100 61 559.7 filed on Dec. 7, 2000 which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The invention relates to a receptacle for securing a tool to a drive shaft of a power tool, a receiving opening being arranged on the tool or on the drive shaft, and a center axis of the drive shaft extending there through, the opening co-acting with a suitably formed securing section arranged in a raised fashion at the other one of the two elements, in order to form a positive engagement for transmitting a torque between the drive shaft and the tool. 
   The invention further relates to a suitable adapter that can be used, if the receiving opening and the securing section of the tool or of the drive shaft are of different shapes. 
   A receptacle of the type mentioned at the outset is known from U.S. Pat. No. 4,980,976 which discloses a U-shaped angled cutting knife for severing adhesive beads in window panes of motor vehicles, the cutting knife having a star-shaped receiving opening in the shape of a regular polygon for securing an oscillatingly drivable drive shaft, the receiving opening being attachable to a suitably shaped securing section of the drive shaft. For securing the cutting knife after attaching to the securing section of the drive shaft with its receiving opening, a screw connection is provided, e.g. in form of a nut that can be screwed onto a screw neck of the drive shaft. 
   Such a receptacle for securing the tool to the drive shaft is provided in particular for oscillatingly drivable tools, in which a positive fit engagement between the drive shaft and the tool for the transmission of higher torques is required. 
   To this end, a plurality of tools are used, which cannot only be used as cutting knives, but also for other tasks, e.g. for sawing. By means of such oscillatingly driven saw blades, for example, precise cuts in car body working can be performed. For sawing in hard accessible locations, also finger-like tools are used, for instance in order to be able to perform special cuts in wood constructional work. Another field of application is grinding, as e.g. described in U.S. Pat. No. 4,920,702, or scraping. 
   It has turned out to be disadvantageous that the known receptacle for engagement between the tool and the drive shaft, in particular for such oscillatingly driven tools, tends to wear out after longer operation under high load. 
   SUMMARY OF THE INVENTION 
   It is a first object of the invention, to create an improved power tool having an improved receptacle for engagement between the drive shaft and the tool. 
   It is a second object of the invention, to create an improved receptacle in which the danger of wear out of the receiving opening is reduced and a transmission of high torques is guaranteed also in long-term operation. 
   It is a third object of the invention, to provide an improved power tool having a receptacle for a tool that is particularly suited for the transmission of high torque even when oscillatingly driven back and forth about a longitudinal axis. 
   It is a further object of the invention to provide a tool having an improved receptacle in which the danger of wear out of the receiving opening is reduced and a transmission of high torques is guaranteed also in long-term operation. 
   It is another object of the invention to provide a tool having an improved receptacle for securing to a power tool allowing the transmission of high torque even when oscillatingly driven back and forth about a longitudinal axis. 
   It is a further object of the invention to provide an adapter that can be used for the engagement between the tool and the drive shaft, if the shapes of the receiving opening and the securing section on the tool and on the drive shaft are different from each other. 
   It is a still further object of the invention to provide a power tool and a tool matched thereto allowing a positive engagement when attaching the tool in different angular positions on the power tool and allowing an easy adjustment of the angular position. 
   These and other objects are achieved according to the invention by a receptacle with a receiving opening the shape of which is mated to a securing section of the drive shaft of the power tool, the securing section and the receiving opening having a plurality of rounded tips arranged at a radial distance from the longitudinal axis of the drive shaft, the rounded tips comprising lateral flanks extending toward intermediate sections extending between adjacent rounded tips. The intermediate sections are preferably configured as sections of a circle extending around the longitudinal axis. 
   By means of the new shape, namely, the occurrence of high torques and/or high surface pressures on any sharp edges like a regular polygon, used in prior art devices, is avoided. Instead, the torque is now mainly transmitted to the tool by lateral flanks forming recesses between the bulges. 
   By means of such a shape, lumped loads and, thus, high surface pressures are avoided, which occurred up to now in receiving openings in the form of regular polygons. 
   In that way, a reliable engagement between the tool and the drive shaft is created, by means of which extraordinarily high torques can be transmitted even with oscillating drives or with impact loads, without any danger that the receiving opening or of the securing section may wear out. 
   In a preferred embodiment of the invention, the receiving opening has eight rounded tips while the raised section provided on the drive shaft has only four rounded tips. The receiving opening and the raised section are preferably matched to each other so as to allow a form-fit connection between said tool and said drive shaft in different angular positions and an adjustment of the angular position in intervals of 45°. 
   Preferably, the receiving opening is arranged on the tool and the securing section is arranged on the drive shaft. 
   In that way, a simple manufacture can be reached particularly by punching the receiving opening out of the tool. 
   According to another embodiment of the invention, the receptacle comprises a securing screw, which can be screwed into a threaded blind hole of the drive shaft. 
   In this way, the securing screw has preferably a head, which is dimensioned for being positioned onto the tool. 
   The object of the invention is further achieved by an adapter for clamping a tool, comprising a receiving opening being arranged on a drive shaft of a power tool, which has a securing section, wherein the shape of the receiving opening is not mated with the form of the securing section, wherein an adapter disk is provided on the first side of which a recess is provided, which is mated to the form of the securing section at the drive shaft in order to form a positive fit engagement with same, and on the second side of which a raised second securing section is provided which corresponds to the shape described before. 
   By using such an adapter, it is possible to use tools, that have already been provided with the receptacle according to the invention on power tools, with drive shafts that have a known securing section. In that way, it is ensured that not all power tools already acquired by users need to be exchanged, if the new tools with the securing section according to the invention are to be used to this end. 
   It is to be understood that the features mentioned above and those yet to be explained below can be used not only in the respective combinations indicated, but also in other combinations or in isolation, without leaving the scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the invention can be taken from the following description of preferred embodiments with reference to the drawings. In the drawings: 
       FIG. 1  shows a very simplified, schematic view of a power tool, the drive shaft of which is provided with a receptacle according to the invention for securing a tool; 
       FIG. 2  shows a view onto the drive shaft according to  FIG. 1  from the outside; 
       FIG. 3  shows a top view of a tool attached with a receiving opening onto a raised section of a drive shaft of a power tool according to  FIG. 1 , with an alternative angular position of the tool shown in dotted lines; 
       FIG. 4  shows a top view of an adapter for attaching a tool having a receiving opening according to the invention to a known power tool having a drive shaft merely comprising a raised cylindrical section for attachment of a tool with a circular receiving opening; 
       FIG. 5  shows a cross-sectional view of the adapter of  FIG. 4  along the line V—V; 
       FIG. 6  shows a bottom view of the adapter shown in  FIG. 4 ; 
       FIG. 7  shows a top view of an alternative embodiment of the adapter shown in  FIG. 4 ; 
       FIG. 8  shows a cross-sectional view of the adapter of  FIG. 7  along the line VIII—VIII; 
       FIG. 8   a  shows a cross-sectional view of a securing screw that can be screwed into a central threaded bole of the drive shaft for securing a tool attached thereto; 
       FIG. 9  shows a bottom view of the adapter shown in  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In  FIG. 1 , a power tool, which is altogether designated with the numeral  10 , is shown in a very schematic fashion. Power tool  10  comprises a drive that is indicated with the numeral  12 , which drives a drive shaft  16  via a gear that is indicated with  14 . Drive shaft  16  comprises tool support  20  having retaining flange  22  that serves to axially support a tool that can be secured onto a securing section  24  protruding outwardly there from. The retaining flange  22  has an outer diameter that is larger than the diameter of securing section  24 . On securing section  24  of drive shaft  16 , a tool  34  (shown in  FIG. 3 ) can be mounted and can be fixed to the drive shaft  16  by a screw-connection. 
   In the present case, power tool  10  is configured such that drive shaft  16  is driven by gear  14  in an oscillating movement back and forth about its longitudinal axis or center axis  18  with a high frequency of e.g. approximately 5000 to 30,000 oscillations per minute and with a small pivot angle of e.g. approximately 0.5° to 5°. 
   In order to allow a positive engagement between tool and drive shaft  16 , securing section  24  of drive shaft  16  has a special shape, by which, together with a suitably formed receiving opening  38  of the tool  34 , a positive fit between tool and drive shaft  16  is reached (see  FIG. 3 ). 
   The shape of the securing section  24 , which is matched to the shape of the receiving opening  38  of the tool  34 , can be seen in more detail in  FIG. 2 . 
   The securing section  24  comprises a cylindrical section  30  axially extending from the retaining flange  22  with a smaller diameter than the retaining flange  22 . From the cylindrical section  30  four rounded tips  26  protrude radially outwardly which are arranged around a center axis  18  of drive shaft  16  in regular angular intervals of 90°, respectively. Each rounded tip  26  has an apex from which lateral flanks  28  extend to each side. 
   The lateral flanks  28  ending in the rounded tips  26  protrude to the outside, leaving cylindrical surface sections  32  between each pair of adjacent tips  26 . The rounded tips  26  have a smaller axial length than has the cylindrical section  30 . Thus the cylindrical section  30  axially protrudes to a certain amount beyond the rounded tips (see  FIG. 1 ). 
   The securing section  24  comprises a threaded central bore  33  into which a securing screw  36   a  (see  FIG. 8   a ) can be screwed for fixing a tool  34  attached with is receiving opening  38  onto the securing section  24 . The screw  36   a  comprises a head  38   a  which is widened in a flange-like fashion. Head  38   a  comprises an annular shaped groove  63  at its side facing drive shaft  16 , so that at the outer edge an annular protrusion  62   a  remains, by means of which head  38   a  can be directly pressed onto the surface of the tool  34  attached to the securing section  24  of the drive shaft  16 . Head  38   a  is equipped with a hexagon socket  40   a  for receiving a hexagon socket tool. 
   However, it will be obvious for those skilled in the art, that any kind of screw could be used for securing the tool on the drive shaft. 
   Although the tool that can be attached to the securing section  24  could generally have any kind of receiving opening allowing attachment to the securing section  24 , it is preferred to match the shape of the receiving opening  38  of the tool  34  to the shape of the receiving section  24  in a particular way, as shown in  FIG. 3 . 
   In  FIG. 3  a tool  34  configured as a cutting tool is shown attached to the securing section  24  of the drive shaft  16  of the power tool  10 . 
   While the securing section  24  of the power tool  10  comprises four rounded tips  26 , the receiving opening  38  of the tool  34  comprises eight rounded tips  40  the shape and size of which are matched to the rounded tips  26  provided on the securing section  24  of the drive shaft  16 . Each pair of adjacent rounded tips  40  of the receiving opening  38  of the tool  34  is connected by arch-shaped lateral flanks forming recesses  42  between the tips  40 , the lateral flanks extending from the pair of adjacent tips  40  toward the longitudinal axis  18  and converging in a common apex of the respective recess  42 . 
   Since the securing section  24  of the drive shaft is configured cylindrical leaving cylindrical surface sections  32  between each pair of adjacent tips  26  extending outwardly, there is space for receiving each recess  42  formed between adjacent tips  40  of the receiving opening. Thus it is possible to mount the tool  34  in eight different angular positions on the drive shaft  16  of the power tool  10 . The tool  34  can be angularly adjusted in increments of 45 degrees. This is indicated in  FIG. 3  by the dashed outline indicating a position of the tool  34  which is rotated by 45 degrees about the longitudinal axis  18  with respect to the position shown in full lines. 
   Angular adjustment of the tool  34  is facilitated by the fact that the cylindrical section  30  axially protrudes beyond the rounded tips  26  to a certain extent. Thus the tool  34  can initially be placed with its receiving opening  38  on the cylindrical section  30  of the drive shaft  16  and can then be rotated into the desired angular position on the cylindrical section  30  until the tips  40  of the tool  34  match with the tips  26  of the securing section  24  thus allowing the tool to axially slide over the tips  26  of the securing section  24  until it rests against the retaining flange  22 . Thereafter the tool can fixed by attaching a securing screw  36   a  such as shown in  FIG. 8   a.    
   The cost of manufacture of the drive shaft  16  is reduced when compared to a drive shaft having more than four tips, such as six or eight tips, since the relatively expensive milling operation for producing the securing section  24  is simplified. On the other hand the cost of producing the receiving opening  38  on the tool  34  is not increased, since usually such receiving openings are produced by a stamping operation. 
   By means of a positive engagement between receiving opening and securing section, a positive force transmission between tool and drive shaft is made possible, wherein, at the same time, the danger that the receiving opening or the rounded tips of the securing section wear out is prevented even when high torques are transmitted under oscillating load or even under impact load. This is mainly achieved by the fact that the lateral flanks of curved sections  28  extend almost radially in partial sections. 
   By reference to  FIGS. 4 through 6 , an adapter will be explained in the following. The adapter allows to clamp a tool, that is configured with a receiving opening formed according to the invention, onto the drive shaft of a power tool, the power tool being configured with a securing section of known design, e.g. having merely a cylindrical securing section without any means for effecting a positive engagement between the tool and the drive shaft. In that way, tools provided with the new receptacle can also be used for already existing power tools, whereby it can be prevented that different tools have to be manufactured beside one another, as, for existing power tools, of course, suitable tools still have to be provided. 
   The adapter designated altogether with the numeral  70  comprises an adapter disk  72 . Adapter disk  72  has a cylindrical recess  84  on its side facing the drive shaft, this recess being mated in its shape and size with the shape of a securing section of a drive shaft of a power tool of known design. In the case shown, the securing section of the drive shaft known in the art is configured merely cylindrical having a central threaded bore for attaching a securing screw. 
   On the opposite side facing away from drive shaft, adapter disk  72  is configured with a raised securing section  86 , which corresponds to the shape of the securing section  24  shown in  FIGS. 1 and 2 . 
   The adapter  70  is penetrated by an axial bore  76  allowing to insert a securing screw there through into the threaded bore of the drive shaft. 
   On its side facing the drive shaft the adapter  70  may comprise a hard metal granulate coating such as indicated by reference numeral  74  in  FIG. 5 . This helps to increase frictional engagement with the drive shaft of the power tool thus allowing a better torque transmission from the drive shaft to the tool even with existing machines without positive engagement. 
   It will be understood that the adapter disk on its side facing the drive shaft could also have any other shape matched to the shape the securing section of a power tool known in the art. Thus the recess  84  might have e.g. a hexagonal shape, if the drive shaft of the prior art power tool is of hexagonal design for positive engagement with a hexagonal receiving opening of a tool. 
   Again, the securing screw  36   a  of  FIG. 8   a  may be used for securing the tool together with the adapter  70  onto the drive shaft of the power tool. 
   With reference to  FIGS. 7 through 9 , an alternative design of an adapter  90  will be described, which can be used for clamping tools of the inventive design onto power tools, the drive shaft of which comprises a securing section of known cylindrical design without any means for positive engagement. 
   Adapter  90  comprises an adapter disk  92 , which is penetrated by an axial bore  96  for inserting a securing screw there through. On its side facing the drive shaft the adapter  90  also comprises a cylindrical recess  94  allowing a fitting onto a cylindrical receiving section of a conventional power tool. 
   Also on this side a hard metal granulate coating  100  may be provided to improve torque transmission as explained before with respect to the embodiment described with reference to  FIGS. 4 through 6 . 
   The single difference between the adapter  70  according to  FIGS. 4 through 6  and the adapter  90  according to  FIGS. 7 through 9  rests in a different kind of securing section  98  for securing a tool  34  having a receiving opening  38  as shown in  FIG. 3  on a drive shaft of a known configuration. 
   The securing section  98  also comprises four rounded tips  102  the shape of which is identical to the shape of the rounded tips  26  of the drive shaft of  FIG. 2 . However, by contrast to the embodiment shown in  FIGS. 1 and 2 , the securing section  98  does not comprise any cylindrical section. Instead the rounded tips  102  comprise arch-shaped lateral flanks  104  that form recesses  106  between adjacent tips  102 . From each pair of adjacent tips  102  the respective lateral flanks  104  converge in a common apex closer to the longitudinal axis  18  than are the tips  102 . 
   Also such a design is possible to receive the receiving opening  38  of a tool shown in  FIG. 3  having eight rounded tips  40 . If desired, also the securing section  24  of the drive shaft  16  shown in  FIGS. 1 and 2  could be designed accordingly. 
   While the design of  FIGS. 7 through 9  leads to a very even torque transmission between the drive shaft and the tool, the design according to  FIGS. 1 and 2  is somewhat easier to produce by milling and offers the additional advantage that the tool can initially be placed on the cylindrical section and is centered thereby during angular adjustment until its final position is reached for securing by attaching a securing screw.