Advantageous further developments and improvements of the chucking device
specified in Claim 1 are possible by virtue of the measures presented in the further claims.
In one embodiment of the invention,, the coupling member is designed as a disc and the recesses are designed as slots, elongate holes, a groove or the like. The drivers can be designed as pins, balls,, webs or the like which rest in longitudinally displbLceable fashion in the recesses therein.
In a preferred embodiment of the invention, one axial driver is arranged on a rotary member which is kinematically connected to the tightening lever.
In an advantageous embodiment of the invention, the kinematic connection between the rotary member and the tightening lever is achieved by means of a clutch which limits the tightening torque of the tightening lever, Such a clutch with torque limitation has the advantage that the tool is fixed in the clamping sleeve with the same, constant force every time and hence that any damage to the chucking device during the clamping of the tool is avoided. Moreover, the presence of this clutch also means that, where there are differences in the thickness of the flat tool ends inserted into the clamping sleeve and, as a result,, in the tightening stroke of the clamping screw, it is always possible for one of the interengaging drivers /recesses to align itself in the stroke direction of the driving plate.
According to a preferred embodiment of the invention, the shank end of the clamping screw which clamps the tool end in the clamping sleeve is of threadless design. As a result, the clamping screw leaves the thread in the clamping sleeve in the open position of the chucking device but, due to the coupling member and the dust washer, remains positioned such that the external R.25556 thread of the screw shank can screw back into the threaded hoie In the clampIng MISM ftfiftg th@ tightening movement of the tightening lever. By virtue of this release of the screw joint between the clamping sleeve and the clamping screw in the open position of the chucking device, i.e. without the tool inserted, clamping of the driving plate is prevented, something which would lead to damage when the hand-held machine tool was switched on.
According to an advantageous embodiment of the invention, an annular shoulder which projects radially beyond the screw shank is furthermore formed between the screw head and the screw shank of the clamping screw. The outside diameter of the annular shoulder is, however, kept smaller than the width of the longitudinal slot in the dust washer, allowing the annular shoulder to pass through the dust washer. The axial height of the annular shoulder is dimensioned so as to be only slightly greater than the thickness of the dust washer. This constructional design prevents the clamping sleeve from being fixed against the dust washer, which is held nondisplaceably in the machine casing something which would likewise lead to damage in the gear mechanism when the hand-held machine tool was switched on.
Drawing The invention is explained in greater detail in the following description with reference to illustrative embodiments depicted in the drawing,, in which:
Fig. 1 shows a partial side view of an electric motordriven file, partially in section, Fig. 2 shows a perspective view of a chucking device in the motor-driven f ile in Fig. 1, in exploded representation, Fig. 3 shows an identical representation to that in Fig.
2, as a detail, of a slightly modified chucking device in accordance with a further illustrative embodiment.
R.25556 Description of the Illustrative Embodiments The electric motor-driven file depicted in partial side view and partially in section in Fig. 1 as an example of a hand-held machine tool for the machining of workpieces has a two-shell plastic casing 10 which, in its rear section is designed as a handle 101 and, in its front section, which adjoins the said rear section seamlessly, is designed as a casing head 102. Integrated into the casing head 102 there is essentially the driving unit 11 for a file blade 12 which projects from the casing head 102 and has a continuous reciprocating stroke motion in the direction of its longitudinal axis imparted to it by the driving unit 11. The electric motor forming part of the driving unit 11 is accommodated in the front part of the handle 101, the part directly adjoining the casing head 102, and is switched on and off by means of a switch strip 14 projecting from the underside of the handle 101. The only part of the electric motor which can be seen in Fig. 1 is the output shaft 16 with the f an impeller 17, seated f irmly on the latter in terms of rotation, which draws the cooling air over the electric motor,, the cooling air entering the interior of the plastic casing 10 via air slits.
In the sectional representation in Fig. 1, details of the driving unit 11 can be seen, although only a short description of these will be given here. The output shaft 16 of the electric motor is in engagement via a driving-wheel mechanism 19 with an driving shaft 20 which is arranged at right angles to the output shaft 16 and is supported rotatably in the casing head 102 by means of an upper ball bearing 21 and a lower needle bearing 22. Seated firmly an the driving shaft 20 in terms of rotation is an eccentric 24 with an upper eccentric portion 241 for driving a reciprocating or driving plate 25 mounted in axially displaceable fashion and with a lower eccentric portion 242 for driving a counterweight plate 26. The latter serves to reduce vibrations in the machine during the filing process. The counterweight plate 26 rests via a thin thrust plate 27 R.25556 on a supporting plate 23 connected to the casing head 142, while the driving plate 25 rests via spacer washers 28, 29 on the counterweight plate 26. Both plates 25, 26 are guided in axially displaceable fashion in the longitudinal direction by means of two pin/slot guides 30 and 35. The driving plate 25 is of f set in the f ront region and the front portion thus lies approximately in the plane of the counterweight plate 26. In the f ront end region, the driving plate 25 carries a tool holder or chucking device 42 by means of which the file blade 12 is fixed rigidly on the driving plate 25.
The chucking device 42,, shown in sectional representation in Fig. 1 and in ex]loded perspective representation in Fig. 2, f6r the exchangeable chucking of the f ile blade 12 has a clamping sleeve 71 with a hollow-box profile, a clamping screw 73 which can be screwed in a threaded hole 72 in the clamping sleeve 71 and having a disc-shaped screw head 731 and a screw shank 732, a so-called Oldham coupling 74, which is formed by the screw head 7331, a coupling member 75 and a rotary member 76,, and a tightening lever 77 which is kinematically connected to the rotary member 76 and the axis of rotation of which is coaxial with the axis of rotation of the rotary member 76. The clamping sleeve 71 is shaped from a bent f lat strip, the two end limbs of the f lat strip lying one above the other and being penetrated by the threaded hole 72. The clamping sleeve 71 is pushed onto the driving plate 25 from the front, the threaded hole 72 being in alignment with an indentation 78 on the upperside of the driving plate 25. The clamping sleeve 71 is held in this position by a spring clip 79. The spring clip 79 is formed by a leaf spring 80 with multiple bends which engages with two spring tongues 801 and 802 in two lateral cut-outs 81, 82 in the driving plate 25 and thus fixes the spring clip 79 non-displaceably on the driving plate 25. The leaf spring 80 comes to rest with its front end against the underside of the clamping sleeve 71 and attempts to force the latter upwards in the direction of the driving plate 25.
R.25556 The clamping screw 73 is pushed with its screw shank 732 through a longitudinal slot 83 in a dust washer 84 and screwed into the threaded hole 72 in the clamping sleeve 71. The length of the longitudinal slot 83 corresponds at least to the maximum stroke movement of the driving plate 25. As can be seen from the sectional representation in Fig. 1, the dust washer 84 is held f irmly in the casing head 102 of the casing 10 - As can be seen in Fig. 2 and also in Fig. 3, an annular shoulder 733 projecting radially beyond the screw shank 732 is formed on the underside of the screw head 731 of the clamping screw 73. The outside diameter of the annular shoulder 733 is smaller than the width of the longitudinal slot 83 in the dust waher 84, with the result that the annular shoulder 733 likewise projects through the longitudinal slot 83. The axial height of the annular shoulder 733 is made somewhat larger than the axial thickness of the dust washer 84.
The Oldham coupling 74, which is known per se, here has two slot and key guides, each oriented at right angles to the other, between the coupling member 75 and, on the one hand, the rotary member 76 kinematically connected to the tightening lever 77 and, on the other hand, the clamping screw 73. For this purpose, the coupling member 75, which is designed as a disc, bears two diametral transverse slats 85,, 86, rotated by 90 relative to one another, which are formed on opposite sides of the disc. A key web engages in axially displaceable fashion in each of the transverse slots 85, 86. Key web 87 is here formed directly on the screw head 731 while the other key web 88 is formed an the underside of the rotary member 76.
As can be seen from Fig. 1, the rotary member 76 is mounted rotatably in the casing head 102 of the casing 10. On its axial side facing away from the coupling member 75, it has a frustoconical cavity 98 in which axial projections and depressions form an internal bevel toothing 90 which can be brought into coupling engagement with a similarly designed external bevel toothing 91 on R.25556 a driving member 92. Together with a clutch spring designed as a helical compression spring 93, the driving member 92, connected to the tightening lever 77, with its external toothing 91 and the rotary member 76 with its internal toothing 90 form a safety clutch 89 which limits the tightening torque of the tightening lever 77 and permits the screwing of the clamping screw 73 by the tightening lever 77 only up to a maximum predetermined torque. The helical compression spring 93 is here supported on the rear side of the driving member 92, the side facing away from the external toothing 91, and in the tightening lever 77 and is accommodated by a hollow stub 94 formed on the underside of the tightening lever 77, coaxially to its axii of rotation. The helical compression spring 93 here fits over a shank 95 which is inserted with positive engagement in the driving member 92 or is formed integrally with the latter. After the assembly of the chucking device 42, the shank 95 and the hollow stub 94 engage positively in one another and the driving member 92 is thus connected firmly in terms of rotation but with the ability for axial displacement to the tightening lever 77.
As can be seen from the sectional representation in Fig. 1, the helical compression springs (sic] 93 presses the external toothing 91 on the driving member 92 into the internal toothing 90 on the rotary member 76 after the chucking device 42 has been assembled. The key web 88 of the rotary member rests in an axially displaceable manner in the transverse slot 86, while the key web 87 on the screw head 731 of the clamping screw 73 slides in the transverse slot 85 of the coupling member 75. The screw shank 732 of the clamping screw 73 projects together with -the annular shoulder 733 through the longitudinal slot 83 in the dust washer 84 and is screwed [lacuna] the threaded hole 72 in the clamping sleeve 71.
With the chucking device 42 open, the handle 77 points forwards beyond the casing head 102 of the casing 10 and extends in the longitudinal direction of the latter. The flat end of the file blade 12 (Fig. 1) is now R.25556 pushed into the clamping sleeve 71 along the underside of the driving plate 25. The tightening lever 77 is then turned through 180' in the clockwise direction, pivoting into a recess in the casing head 102. As the tightening lever 77 is pivoted, the clamping screw 73 is turned in the clockwise direction via the safety clutch 89 and the Oldham coupling 74, its front end being supported in the indentation 78 on the driving plate 75. The clamping sleeve 71 is thereby pulled upwards and presses the file blade end with nonpositive engagement against the underside of the driving plate 25. By appropriate design of the safety clutch 89 with the helical compression spring 93, the tightening lever 77 can be;made to exert a imum torque of 1 Nm on the clamping screw 73. If this torque is exceeded, the driving member 92 with its external toothing 91 is lifted out of the internal toothing 90 of the rotary member 76 counter to the spring force of the helical compression spring 93. In addition to the non-positive engagement, a positive engagement can furthermore be provided between the driving plate 25 and the file blade 12 by the provision, on the underside of the driving plate 25, preferably coaxially with the indentation 78 on the upperside of the driving plate 25, of an axial projection 96 which engages in a corresponding recess or hole 97 in the file blade 12 (Fig. 1).
To change the f ile blade 12, the handle 77 is pivoted forwards through 180 in the anticlockwise direction until it extends in the longitudinal direction of the file blade 12. As a result. the clamping screw 73 is to a large extent unscrewed from the threaded hole 72, the clamping sleeve 71 being pushed downwards by virtue of the fact that the screw-shank end is supported on the upper side of the driving plate 25 and the file blade 12 thereby being released to allow it to be changed.
TO prevent a situation where, during the opening of the chucking device 42 for the purpose of changing the file blade 12, the clamping sleeve 71 is screwed so far downwards by pivoting the tightening lever 77 too far that the driving plate 25 is clamped in its linear-motion R.25556 mounting, which would M199 dafflg(j@ ifi QG "lyp5 unit 11 when the motor- driven file was switched ont the end 734 of the screw shank 732 of the clamping screw 73 is, according to a modification (shown in Fig. 3) of the chucking device 42, of threadless design. This has the consequence that,, at the end of the pivoting of the tightening lever in the opening direction, the external thread on the screw shank 732 comes out of engagement with the internal thread of the threaded hole 72. i.e. the clamping screw 73 unscrews completely from the threaded hole 72 in the clamping sleeve 71. It is therefore impossible for the clamping sleeve 71 to be clamped on the driving plate 25. However,, the..clamping screw 73 is as before positioned unalterably by the coupling member 75 and the dust washer 84, allowing it to be screwed back into the threaded hole 72 without problems during the tightening movement of the tightening lever 77.
The annular shoulder 733 between the screw head 731 and the screw shank 732 ensures that,, with the chucking device 42 closed, i.e. with the file blade 12 gripped, the clamping sleeve 71 cannot be tightened against the underside of the dust washer 84 and thus clamped fast against the latter, which would likewise lead to damage in the driving unit 11 when the motordriven file was switched on. On the contrary,, the clamping sleeve 71 comes to rest against the annular shoulder 733 and, because of the greater axial height of the latter in comparison with the thickness of the dust washer 84, a gap for movement remains between the clamping sleeve 71 and the dust washer 84.
As a modification of the chucking device 42 described, a through hole can be provided in the driving plate 25 instead of the indentation 78. The screw shank 732 of the clamping screw 73 then passes through the hole and is supported by its shank end directly an the end of the file blade.
The invention is not restricted to the illustrative embodiment described above. The so-called Oldham R.25556 coupling 74 can, for example, be designed in various ways. instead of the transverse slots 85, 86, it is, for example, possible for radial slots or radial elongate holes to be provided in the coupling member 75 and for pins or balls to be provided on the screw head 731 or on the rotary member 76 instead of the key webs 87, 88. In this arrangement, for example, two pins on the screw head 731 engage in mutually aligned radial slots in the coupling member 75 and two pins on the rotary member 76 engage in two more mutually aligned radial slots in the coupling member 75 which are rotated by 90 relative to the first two radial slots.
The safety clutch 89 designed-as a frictionally and positively engaging slipping clutch can furthermore be embodied with spur toothing instead of bevel toothing 90, 91. In a less convenient chucking device, the safety clutch 89 can be dispensed with completely. In this case, the rotary member 76 is then connected directly and firmly in terms of rotation to the tightening lever 77.
- 12 Claims 1. Chucking device for a metal-removing hand-held machine tool, in particular a motor-driven file, for the exchangeable chucking of the metal-removing tool, in particular the file blade, characterized by a clamping sleeve (71) with a hollow-box profile arranged on a reciprocating driving plate (25) and serving to receive the flat tool end, a clamping screw (13) which tightens the clamping sleeve (71) in order to clamp the tool end received therein against the driving plate (25) and can be screwed up and down in the clamping sleeve (71), a tightening lever (77) which can be pivoted about a pivot fixed to the machine casing and is intended for turning the clamping screw (73), and a radially movable coupling member (75) arranged between the tightening lever (77) and the clamping screw (73) and having at least two recesses (85, 86) oriented radially and at right angles to one another,, an axial driver (87) of the clamping screw (73) engaging in one recess (85) and an axial driver (88) kinematically connected to the tightening lever (17) engaging in the other recess (86).