Abstract:
A chisel holder is connected exchangeably in a fixed manner to at least one base mount disposed on a surface of a cylindrical cutting device, such as a cutting machine or a line milling machine, in a manner obviating use of a threaded setscrew. A borehole extends through the base mount, and a securing bolt received therein grips at least regionally through or behind an aligned recess formed in the chisel holder. The securing bolt is then clamped or locked to the base mount without use of threads.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a cylindrical cutting device, and more particularly to a cutting machine or a line milling machine in which a chisel holder or like tool is removably secured to a base carried on the machine. 
     As a rule, such cutting devices have a plurality of bases disposed on their surface at a uniform spacing, and form, for example, a broach-loading screw or a broach spiral. In this connection, a chisel holder with an exchangeable chisel is connected to each base or, in some bases, an appropriately fitting chisel is inserted directly without having a chisel holder as an intermediate element. 
     A known cutting device of this type is disclosed for example in DE 43 22 402 C2. In the disclosed device, a chisel holder includes a shaft which is introduced into a plug-in receptacle of a base, and is referred to as a plug-in attachment. To prevent the chisel holder from being pulled out, the chisel holder is secured in the base with a setscrew, which can be actuated by means of a recessed hexagonally shaped tool receptacle and which setscrew engages an assigned recess of the shaft of the chisel holder. 
     The above method of securing the chisel holder has a disadvantage in that an internal thread of a borehole which extends through the base, and the hexagonal recess of the setscrew which serves to accommodate a tool, are susceptible to contamination especially when a cutting operation of the cutting device creates an abundant amount of dust. As a consequence, it becomes increasingly difficult to loosen the setscrew in order to exchange the chisel holder. 
     The present invention is therefore concerned with the problem of providing a cutting device of the above type, for which the chisel holder or holders, or like tools, are secured in a simple manner not susceptible to contamination and, accordingly, can be loosened easily when required. 
     SUMMARY OF THE INVENTION 
     In accordance with these and other objects of the invention, there is provided a cylindrical cutting device which includes at least one base mount disposed on a surface thereof. A borehole is formed extending through the base mount, in which a securing bolt is receivable. A chisel holder is provided for exchangeable securement to the basc mount. A recess is formed in the chisel holder such that, when the securing bolt is inserted in the borehole, a portion of the securing bolt at least regionally engages the recess, preventing separation of the chisel holder from the base mount. The securing bolt is detachably secured to the base mount by a press-fitting or other locking structure in a manner advantageously avoiding the use of threads. 
     By virtue of the fact that the securing bolt is not constructed as a setscrew, pursuant to the present invention, it is held without threads by being jammed or locked in the borehole formed in the base mount. As a result, there are no threads which are subject to contamination in the base mount and, with that, there is also no danger that such threads will be clogged with foreign objects and make it difficult to loosen and exchange the chisel holder. 
     The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view in partial cross-section of a base mount with a chisel holder and a chisel; 
     FIG. 2 is a top view from the direction II in FIG. 1, depicted without the chisel; and 
     FIG. 3 is an exploded front view from the direction III in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures, and in particular FIG. 1, a base mount  1  is depicted having an underside which is curved concavely and thus adapted to cutting device cylindrical surface  2  of the cutting device indicated by broken lines as is its access  2   a  and to which the base mount  1  is fastened, for example, by a welded connection. The body of the base mount  1  has a plug-in receptacle  3 . A chisel holder  4  has a shaft  5  which is integrally molded with the chisel holder  4  and which is received in the plug-in receptacle  3 . The chisel holder  4  comprises a chisel receptacle  6 , which accommodates a shaft part  7  of a chisel  8 . At a side of the chisel receptacle  6  facing a chisel head  9 , a contact surface  10  is formed, at which the chisel  8  is supported by a shoulder  11 . A toggle-type fastener  13  prevents the chisel  8  from being pulled out in the direction of its axis  12 . 
     A through-hole  14  accommodates a securing bolt  15  and extends through the base mount  1 . As can be seen most clearly in FIG. 3, in which the chisel holder  4  with the chisel  8  is shown separated from the base mount  1  and above the base mount  1 , the shaft  5  of the chisel holder  4  has a recess  16  which is alignable with the borehole  14  in the base mount  1  when the shaft  5  is inserted in the plug-in receptacle  3 . The recess  16  is constructed, in the example of the embodiment shown, as a peripheral annular groove open at the side. In the position in which it is introduced into the base mount  1 , the securing bolt  15  grips regionally behind the shaft  5  of the chisel holder  4 , engaging the recess  16 , and thus prevents the chisel holder  4  from becoming detached from the base mount  1 . In this connection, the construction of the recess  16 , which is open at the side, is more advantageous than that of a recess which passes completely through the shaft  5 , since shear forces which act on the securing bolt  15  are less in the case of the embodiment shown in the event that play develops between the chisel holder  4  and the base mount  1 . When the recess  16  is constructed as an annular groove disposed at least partially around the shaft  5 , shear forces acting on the securing bolt  15  are avoided even if the chisel holder  4  were to twist. For manufacturing reasons, the construction of the recess  16  as an annular groove disposed completely around the shaft  5  is particularly advantageous. In the case of the embodiment shown, the chisel holder  4  is then prevented from twisting, in that it is held by a nose-like region  17  engaging a locating surface  18  of the base mount  1 . 
     Referring to FIG. 2, which represents a radial view of the cutting device depicted without a chisel, the borehole  14  extends at an acute angle α to a longitudinal plane  19  of the chisel holder  4  and also extends at an acute β relative to a plane  1   a  which is perpendicular to the cylindrical axis  2   a.  By means of this arrangement, the load acting during the operation of the cutting device on the securing bolt  15  disposed in the borehole  14  is distributed uniformly over the securing bolt  15 . Also as can be seen in FIG. 2, the longitudinal axis  19  of the chisel holder  4  extends at an acute angle δ angle relative to the aforementioned plane  1   a.    
     In the case of the embodiment shown, the securing mechanism is constructed as a clamping device, the securing bolt  15  being held in the borehole  14  by a press fit. This has the advantage that the borehole can be configured completely smooth on the inside, so that contaminating particles do not adhere to its walls. The securing mechanism can, however, also be constructed as a locking device, for example, in the form of a bayonet catch. 
     The securing bolt  15 , as shown in FIG. 3, has a conical front part  20  which facilitates the introduction into the borehole  14 , and a rear part  21  with a cylindrical surface. In the rear part  21 , regions of the surface are deformed elastically, the elastically deformable region in the undeformed state being over dimensioned with respect to the borehole  14 , thus bringing about the clamping action of the press fit. Advantageously, the elastically deformable region is formed by a sleeve  22 , as shown. In particular, the sleeve  22  may advantageously consist of a suitable plastic. The sleeve  22  can also be developed exchangeably, in that it is pushed, for example, with slight expansion, over the securing bolt  15 . For this purpose, the core of the securing bolt  15  in the region of the sleeve  22  can have a smaller diameter so that upper and lower contacting surfaces are formed, which prevent the sleeve  22 , which is pushed onto the securing bolt  15 , from slipping to one side. Use of such an exchangeable sleeve  22  allows replacement thereof when worn, without having to replace the whole of the securing bolt  15 . It is also possible to replace the sleeve  22  by a sleeve of larger external diameter, should play have developed between the borehole  14  or the recess  16  of the chisel holder  4  and the securing bolt  15  during the operation of the cutting device. 
     The securing bolt  15  shown includes a bolt head  24  at a rear end thereof which, in an installed state, covers a rear outlet opening  23  of the borehole  14 . Such construction further decreases the danger that contamination will penetrate into the borehole  14 . In addition, during assembly, the securing bolt  15  can be pressed into the borehole  14  as far as the bolt head  24  without the risk of driving the securing bolt  15  through the borehole  14 . In order to undo the securing mechanism, the securing bolt  15  is driven out of the borehole  14  with a suitable tool from an opposite outlet opening  26 . Alternatively, the bolt head  24  can serve for undoing the securing mechanism. For this purpose, it may have, for example, recesses which can be engaged by a suitable tool in order to pull out the securing bolt  15 . 
     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.