EP0324357A2 - Device for clamping a disc-like tool - Google Patents

Abstract

Around a device for clamping a disk-shaped tool (22) on a tool spindle (20) of a hand-held power tool with a clamping anchor (46) arranged in the tool spindle, with a clamping flange (82) that can be fastened to the free end of the clamping anchor, with one at the tool-side end of the tool spindle arranged abutment (24) and with a device for releasably pressing the clamping flange against the abutment with intermediate clamping of the tool, it is proposed that the device have a first pressure cylinder, a second pressure cylinder and a connecting channel (66) between the two cavities (56 , 70), that the second pressure cylinder comprises a piston (68) delimiting the second cavity and that the piston for releasable clamping of the tool can be adjusted and fixed from a tool-side end of the tool spindle by the manual actuation mechanism.

Description

The invention relates to a device for clamping a disc-shaped tool on a motor-driven tool spindle of a hand-held power tool, in particular a grinding wheel on an angle grinder, with a clamping spindle arranged in the tool spindle provided with an axial recess and axially displaceable and non-rotatably connected to it, with an am free end of the tension anchor releasably attachable tension flange, with an abutment arranged on the tool-side end of the tool spindle and with a device which can be actuated by means of a manual actuation mechanism for releasably pressing the tension flange against the abutment with intermediate clamping of the tool.

Such a device is known from DE-PS 34 05 885. In this, the clamping anchor arranged in the tool spindle designed as a hollow spindle is displaced by a compression spring also arranged in the tool spindle such that a clamping flange which can be fastened to the clamping anchor clamps the disk-shaped tool against an abutment on the tool spindle. At this The device thus generates the clamping force by a spring arranged in the hollow spindle. By means of the actuating mechanism, the tensioning anchor can now be moved against the force of the compression spring, so that the tensioning flange can be easily loosened or screwed on by hand and consequently the disk-shaped tool can be fastened without additional tools.

The tensioning of the tensioning anchor by means of the known spring requires a manual actuation mechanism which is fixed to the housing on the opposite side of the tool and which allows a force which counteracts the spring to be applied manually, so that this type of actuation prevents the most compact construction of the entire device.

The invention is therefore based on the object of making the known device for fastening a disk-shaped grinding tool, in which no auxiliary tool is required for loosening or tightening the tool fastening, as compact as possible, in particular hydraulically actuable.

This object is achieved according to the invention in a device of the type described in the introduction in that the device comprises a first pressure cylinder, comprising a first cavity between the tension anchor and the tool spindle, a second pressure cylinder, comprising a second cavity arranged in the tension anchor or in the tool spindle, and a connecting channel between the two cavities, that the second pressure cylinder comprises a piston arranged in the second cavity and that the piston for clamping one the tool-side end of the tool spindle can be adjusted by the manual actuation mechanism and can be fixed in its position that holds the tool.

From DE-GM 69 18 532 a clamping device for clamping a tool arranged on a machine part by interaction of a first and a second pressure cylinder and an actuating device is known. However, this clamping device is always arranged so that the tool between it itself and the machine part, that is, for example the tool spindle, is arranged so that the entire clamping device is arranged opposite the tool of the tool spindle and sits directly on the tool and consequently this against the Tool spindle can press.

Thus, the DE-GM 69 18 532 can not anticipate the special design of the tool spindle and the tension anchor guided therein, as well as the arrangement and the two pressure cylinders within the tool spindle provided with an axial recess, as is the subject of the present invention.

The essence of the invention is thus to be seen in the fact that both pressure cylinders are arranged in the tool spindle, which is in any case necessary, and can also be actuated from an end of the tool spindle on the tool side, the two pressure cylinders both in the position exciting the tool and in the position not exciting the tool correspond with each other and when the actuatable pistons of the second pressure cylinder are tensioned, a pressure medium arranged in both pressure cylinders and in the connecting channel is acted upon, which in turn causes the tension anchor in the second pressure cylinder to move from its non-tensioning position to its tensioning position. A reduction is preferably provided between the second and the first pressure cylinder, that is to say that a lower force acting on the piston during actuation in the second pressure cylinder leads to a greater force on the tension anchor in the first pressure cylinder.

An exemplary embodiment is particularly preferred in which the first cavity is defined by mutually facing and axially spaced boundary surfaces of the tool spindle and the tension anchor and corresponding lateral surfaces of the tension anchor and the tool spindle.

A structurally particularly simple solution can be achieved in that the boundary surface of the tension anchor faces the tool, while the boundary surface of the tool spindle is arranged facing away from the tool, so that a volume dilation in the first cavity leads to the boundary surface of the tension anchor facing away from the tool is moved and thus the clamping anchor can carry out an axial displacement directly clamping the tool.

To adjust the piston, it is advantageously provided that it is open via a tool and there is a bore extending up to the piston in the clamping anchor or in the tool spindle, which the manual actuation mechanism penetrates.

In the exemplary embodiments described so far, no details have been given of the mechanism by which the piston should be actuable. Thus, in a preferred embodiment it is provided that the manual actuation mechanism is arranged in an area of the clamping anchor or the tool spindle on the tool side.

Operation of the device according to the invention can be achieved particularly expediently if the manual actuation mechanism is accessible for operation from the side of the tool facing away from the tool spindle.

This manual actuation mechanism is in particular designed such that it can be operated via a holding device which can be releasably attached to the tension anchor for fastening the tensioning flange to the tension anchor, since such a releasably attachable holding device is necessary anyway. An optimal compact design is thus achieved, since both the entire device for pressing the clamping flange against the abutment with intermediate clamping of the tool and the manual actuation mechanism for this device are already integrated in parts, which are usually required anyway in such a handheld power tool, so that there is almost no increase in volume in the solution according to the invention.

The manual control device according to the invention can be integrated particularly well into a hand-held power tool if the manual control device comprises an adjustable clamping element which acts on the piston for clamping.

The tendon can be adjusted in a wide variety of ways. For example, it is conceivable that the tendon can be directly loaded with the hand and locked in its actuated position. Easier and, above all, less forceful operability of the tendon is possible if it has a surface that is oriented obliquely to an adjustment direction of the piston. This surface can be, for example, the lateral surface of an eccentric, via which the piston can be actuated, for example, by means of a piston rod. However, the inclined surface can also be a run-up surface which can be displaced transversely to the adjustment direction of the piston and which likewise acts, for example, on a piston rod and thereby adjusts the piston.

The simplest possibility of realizing the inclined surface is when the tendon has a thread, the threaded surfaces of which then form the inclined surfaces.

The tendon itself can be arranged at different points within the scope of the manual control device. This is the case with a possible embodiment according to the invention form provided that the tendon is arranged in the tension anchor or in the tool spindle, in particular in the bore extending to the piston.

An alternative solution according to the invention provides that the tendon is arranged on the holding device.

With regard to the arrangement of the clamping flange, no further details were given in the solutions according to the invention described so far. For example, it is favorable if the holding device comprises the clamping flange.

In order to be able to fasten this tensioning flange to the tensioning anchor, it is provided that the holding device has a holding member that can be positively attached to the tensioning anchor against axial displacement. The holding member can be designed in a wide variety of ways. It is possible, for example, if the holding member can be connected to the tension anchor in the form of a bayonet catch.

A constructive alternative to this provides that the holding member can be screwed into the tension anchor.

A particularly preferred embodiment of a manual actuation mechanism provides that the tensioning member and the holding member are the same screw, so that by screwing this screw into the tensioning anchor both the tensioning flange is fastened to the same and the piston is simultaneously actuated.

For this purpose, it is particularly advantageous if the screw is in a first and a second one adjoining it Threaded section of the tension anchor can be screwed in and when the piston can be actuated when screwing into the second threaded section. Such a constructive solution has the great advantage that first of all a rough securing of the clamping flange on the clamping anchor can take place and, when the screw is screwed in further, the piston is actuated, which then leads to the final clamping of the tool.

In this embodiment, it is advantageous if the clamping flange is rotatably held on the holding member and can be acted upon by it in the direction of the tool. This is necessary in order to avoid, when fastening the tool, that the rotation of the holding member is made difficult by frictional forces between the tool and the screw itself. However, if the clamping flange rotatable on the holding member lies on the tool, the holding member can still be designed so that it can be easily rotated with respect to the clamping flange, even if, for example, a shoulder is applied to the clamping flange.

A particularly easy turning of the holding member can be achieved if an axial pressure bearing is arranged between the screw and the clamping flange.

To prevent the clamping flange from rotating relative to the tool spindle, which is particularly necessary if the tool spindle of the hand-held power tool according to the invention can be rotated in opposite directions or if a braking device is provided for the tool spindle, it is advantageous if the clamping flange can be fixed in a rotationally fixed manner on the tool spindle by positive locking elements.

In addition, for safety reasons, it is often advisable to prevent the tendon from rotating relative to the tendon flange during operation. For this reason it is provided that the tendon on the clamping flange can be secured against rotation.

The simplest form of such a fuse provides that the tendon can be positively secured to the clamping flange.

Such positive locks are conceivable in any way. For example, it would be possible to provide a detent that can be displaced in the radial direction relative to the tool spindle.

However, it is particularly expedient if the tendon can be secured by a locking element which can be displaced in the axial direction, which can be, for example, a bolt which engages in bores in both the tendon and the tensioning flange.

However, such a variant would have the consequence that securing is only possible in certain relative positions between the tendon and the tensioning flange. For this reason, it is expediently provided in the context of the above exemplary embodiment that the securing element is held in a rotationally fixed and axially displaceable manner on the tensioning member or on the tensioning flange and can be brought into engagement with a toothed ring of the tensioning flange or the tensioning member which is coaxial with its axis of rotation. It is thus possible to secure the tendon at an angular position corresponding to an angular distance between successive teeth of the ring gear.

Finally, it is also advantageous if the securing element can be locked in its position securing the screw.

As an alternative to the embodiment in which the tendon and the holding member form one and the same screw, a further preferred exemplary embodiment provides that the tendon is adjustable relative to the holding member, variants in particular being conceivable in which the tendon can be screwed into the holding member .

In this embodiment, a rotation of the holding member after the tool has been placed on the abutment is not necessary for the final clamping of the tool, so that in a simple embodiment it is sufficient if the clamping flange is formed on the holding member.

Alternatively, however, as in the exemplary embodiment described above, it can be provided that the clamping flange can be rotated relative to the holding member, so that the clamping flange can be rotatably fixable to the tool spindle by positive locking, in particular in the case of tool spindles which can be rotated in opposite directions or also braked tool spindles.

A structurally particularly simple and expedient embodiment of the present invention provides that the tensioning member is a threaded spindle with an actuating element protruding beyond the holding member, so that the threaded spindle is turned into a by rotating the actuating element the position acting on the piston can be screwed in for clamping the tool and unscrewed for loosening. It is therefore sufficient if the holding member is positively fixed to the tension anchor in the axial direction and, by screwing in the threaded spindle, the final clamping of the tool takes place by reducing the second cavity and enlarging the first cavity, the latter causing the entire tension anchor to be displaced from the tool away and thus to a clamping of the tool by the holding member fixed to the clamping anchor and the clamping flange connected to the holding member.

For safety reasons, it is also advantageous if the clamping element can be fixed in a rotationally fixed manner on the holding member by means of a securing element, wherein the clamping element can also be fixed in a rotationally fixed manner by positive locking.

Such a securing element can also be configured differently, as already described above, a securing element which can be displaced in the axial direction being preferred within the scope of the present invention.

This securing element is most simply and expediently designed in such a way that it is a cap that engages over the actuating element of the tendon.

Furthermore, in an improved embodiment it is additionally provided that the securing element can be locked in its position fixing the tendon.

In all of the exemplary embodiments described, no details were given as to which pressure medium is provided in the first cavity, in the second cavity and in the connecting channel.

It is provided in a preferred embodiment that the first and second cavities and the connecting channel are filled with a plastic mass for hydraulic pressure transmission. This is particularly expedient because handheld power tools are to be used when there are large temperature differences and these are then to function reliably. When using a conventional hydraulic oil, this leads to sealing problems in the pressure cylinders that are difficult or almost impossible to control. In contrast, the plastic mass has the advantage that such leakage problems can be avoided with it.

A particularly preferred plastic mass is a polyvinyl chloride with a relatively low degree of polymerization.

Alternatively, however, it is also conceivable for the first cavity, the second cavity and the connecting channel to be filled with a viscous mass, since the above-mentioned tightness problems can also be avoided with this. The viscous mass is preferably a silicone mass, in particular a silicone lubricant.

In addition, it is also advantageous if the plastic or viscous masses are compressible, since these then become elastic and stick to under lead to different expansions of the individual parts, adapting the tension of the tool.

However, in order to be able to work with essentially incompressible pressure transmission media in the solution according to the invention, it is provided in a variant of the solution according to the invention that an elastic element allowing an axial displacement of the clamping flange is provided relative to the tool spindle. This element can be arranged in a wide variety of locations. For example, it is conceivable to arrange this element between the clamping flange and the holding member acting on it.

This elastic element is preferably dimensioned such that it can be compressed to inelasticity when the tool is clamped. This enables an even greater distance to be reached when clamping and that this elastic element also ensures that if the tool according to the invention has not been completely clamped, it ensures that the tool nevertheless rotates with the tool spindle and thus not to all possible accidents caused by insufficient tension.

In a particularly simple embodiment, the elastic element is a volume-elastic element arranged in one of the cavities, so that it is first compressed and then the tool is finally clamped by the volume compression.

• Fig. 1 einen Schnitt durch ein erstes Ausführungs­beispiel;
• Fig. 2 einen Schnitt ähnlich Fig. 1 durch ein zwei­tes Ausführungsbeispiel.
• Fig. 3 einen Schnitt ähnlich Fig. 1 durch Werkzeug­spindel, Spannanker und Halteeinrichtung eines dritten Ausführungsbeispiels.

Further features and advantages of the invention are the subject of the following description and the drawing of some exemplary embodiments. The drawing shows:

• 1 shows a section through a first embodiment.
• Fig. 2 shows a section similar to FIG. 1 through a second embodiment.
• Fig. 3 shows a section similar to FIG. 1 through the tool spindle, tension anchor and holding device of a third embodiment.

A first exemplary embodiment of an angle grinding machine according to the invention, shown in FIG. 1, comprises a drive motor 10, partially shown in the drawing, the drive shaft 12 of which drives a bevel gear 16 of a tool spindle 20 rotatably mounted in a gear housing 18 via a drive pinion 14. This tool spindle 20 has at one end a flange 24 serving as an abutment for a tool, in particular a grinding wheel 22. The tool spindle 20 is mounted in the gear housing 18 on a side facing the flange 24 by means of a lower bearing 26 and on a side facing away from the flange 24 by means of an upper bearing 28 arranged at a distance from the lower bearing 26. Thus, the tool spindle 20 is one Axis 30 rotatable.

The tool spindle 20, which is designed as a hollow spindle, comprises a coaxial central recess 32 which, with a widened section 36, extends into the tool spindle 20 from an end 34 opposite the flange 24 and thus the tool 22, via a step surface 38 into a central section 40 passes into a smaller diameter with respect to the widened section 36 and, following the central section 40, widens in the region of the flange 24 to form a toothed section 44 which is provided with internal teeth 42 and which is open towards the tool 22.

In this tool spindle 20, a tension anchor 46 is displaceable in the axial direction, but is mounted in a rotationally fixed manner, which has a center piece 48 guided in the central section 40 of the coaxial recess 32, which carries on its end facing away from the tool 22 a tension anchor head 50 which has a larger diameter than the middle piece 48 and is guided in the expanded section 36.

On its side facing the step surface 38, this tension anchor head 50 has an annular surface 54 which extends up to a lateral surface 52 of the central piece 48, which together with the lateral surface 52 of the central piece 48, the step surface 38 and the widened section 36 of the coaxial recess 32 has a first Cavity 56 of a first pressure cylinder, formed by the tool spindle 20 and the clamping anchor 46 displaceable therein, is limited.

To enable this first pressure cylinder to work properly, the middle piece 48 is provided with an annular seal 58 which is effective with respect to the central section 40 of the coaxial recess, and the tension anchor head 50 is provided with an annular seal 60 which is effective with respect to the expanded section 36.

The tension anchor 46 is in turn also provided with a central bore 62 penetrating it from the side of the tension anchor head 50, into which a screw plug 64 is screwed in the area of the tension anchor head 50. Starting from this central bore 62, connecting channels 66 extending in the radial direction and arranged in a region of the central piece 48 facing the tension anchor head 50 extend to the first cavity 56.

On the tool side of these connecting channels 66, a piston 68 is sealingly arranged in the central bore 62 and defines a second cavity 70 which is delimited on the one hand by the piston 68, on the other hand by the screw plug 64 and by a bore section 72 of the central bore 62 lying between the two .

The piston 68 itself is acted upon from its side facing the tool 22 by a piston rod 74 which extends away from the piston 68 through the central bore 62 in the direction of the tool 22.

Toward the tool 22, the tension anchor 46 is provided with a threaded bore 76 into which the central bore 62 coming from the tension anchor head 50 merges, the Ge wind bore 76 has a larger diameter than the central bore 62.

The piston rod 74 is dimensioned such that it projects out of the central bore 62 into a second threaded section 78 of the threaded bore 76, which adjoins the central bore 62. This second threaded section 78 is followed in the axial direction towards the tool 22 by a first threaded section 80 of the threaded bore 76.

The tool, that is to say the grinding wheel 22 in this case, is held by means of a clamping flange 82, which is part of a holding device designated as a whole by 84. This holding device 84 comprises a holding screw 86 which can be screwed into the threaded bore 76 from the side of the tool 22 using a threaded bolt 88. Connected to this threaded bolt 88 of the holding device 84 is a cylindrical piece 90, which carries on its end opposite the threaded bolt 88 a circular disk-shaped screw head 92 which extends essentially parallel to the flange 24 and has a diameter approximately comparable to this. This screw head 92 acts on the clamping flange 82 via an axial pressure bearing 94 arranged on its side facing the flange 24, which clamps the grinding wheel 22 between it and the flange 24 designed as an abutment in order to hold the grinding wheel 22.

A sleeve 96, which surrounds the cylindrical piece 90 and is rotatably mounted on the cylindrical piece 90, is formed on the clamping flange 82. This sleeve 96 carries one External teeth 98, which can be brought into engagement with the internal teeth 42 of the toothed section 44 of the coaxial recess 32. The sleeve 96 can thus be displaced in the axial direction into the toothed section 44, but is held non-rotatably in the latter relative to the tool spindle 20.

In the exemplary embodiment shown in FIG. 1, both the screw head 92 and the clamping flange 82 have the same diameter and both are provided with teeth 100 and 102 on their surfaces lying radially outside with respect to the axis 30, both teeth 100 and 102 with one another are identical. The two toothings 100, 102 preferably have teeth arranged at an angular distance of approximately 5 °. With these, an internal ring gear 104 of a cover cap 106 can be brought into engagement, which overlaps the screw head 92 on its end face 112 facing away from the tool 22 and the screw head 92 as well as the clamping flange 82 in the region of their radially outer toothings 100 and 102.

This cover cap 106 is mounted on the retaining screw 86 by means of a pin 108 in that this pin 108 engages in an inner bore 110 which extends from the end face 112 into the retaining screw 86. As a result, the entire cover cap can be displaced in the direction of the axis 30 by the pin 108 guided in the inner bore 110, so that the inner toothed ring 104 either engages only with the toothing 100 of the screw head 92 or both with the toothing 100 of the screw head 92 as as well as with the toothing 102 of the clamping flange 82.

In order to be able to lock the cover cap 106 in its position engaging in both toothings 100 and 102, the pin 108 is provided with a first annular groove 114 into which a retaining ring 118 mounted in a circumferential groove 116 of the inner bore 110 engages when both toothings 100 and 102 are engaged with the internal ring gear 104. In addition, the pin 108 is additionally provided with a second annular groove 120, into which the retaining ring 118 engages when the internal ring gear 104 is only engaged with the toothing 100.

The exemplary embodiment according to the invention shown in FIG. 1 now functions as follows:

To mount the grinding wheel 22, the entire holding device 84 is removed by unscrewing the threaded bolt 88 from the threaded bore 76. A new grinding wheel 22 can now be placed on the flange 24.

Thereafter, the holding device 84 is inserted, the sleeve 96 integrally formed on the clamping flange 82 being rotated such that its external toothing 98 comes into engagement with the internal toothing 42 of the toothed section 44 of the coaxial recess 32. This sleeve 96 thus ensures that the clamping flange 82 is non-rotatably connected to the tool spindle 20. The retaining screw 86 is then screwed with its threaded bolt 88 into the threaded bore 76 of the tensioning anchor 46 with the cover cap only engaged with the toothing 100, whereby the threaded bolt 88 first turns into the first threaded section 80 and then reaches the adjoining second threaded section 78. As soon as the threaded bolt 88 reaches this second threaded section 78, its front surface 122 acts on the end of the piston rod 74 facing it and thus also on the piston 68 via the piston rod 74. This is the case with the solution according to the invention when the retaining screw 86 with the Threaded bolt 88 is already screwed in so far that the clamping flange 82 rests on the grinding wheel 22 and also abuts it against the flange 24, the clamping flange 82 being acted upon by the screw head 92 via the thrust bearing 94. If the clamping flange 82 is already on the grinding wheel 22 when the front surface 122 has no contact with the piston rod 74, the clamping anchor 46 is pulled in the direction of the tool 22 until the movement of the clamping anchor 46 itself and the displacement of Pressure transmission medium from the first cavity 56 into the second cavity 70 via the piston 68, which have brought the piston rod 74 into contact with the front surface 122. The reverse process takes place when the front surface 122 abuts the piston rod 74 before the clamping flange 82 contacts the grinding wheel 22 on the flange 24.

If the retaining screw 86 is rotated further from this point, the threaded bolt 88 pulls the entire tension anchor 46 in the direction of the flange 24 by engaging in the threaded bore 76, so that the first cavity 56 of the first pressure cylinder is reduced, since the annular surface 54 and the step surface 38 towards each other be moved. At the same time, however, the front surface 122 presses the piston 68 in the direction of the tension anchor head 50 via the piston rod 74, so that the second cavity 70 is also reduced.

In an advantageous embodiment, the first cavity 56, the second cavity 70 and also the connecting channels 66 are filled with a plastic mass, preferably a polyvinyl chloride with a relatively low degree of polymerization. This plastic mass is pressurized by the reduction in the first cavity 56 and the simultaneous reduction in the second cavity 70 when the retaining screw 86 is screwed in further, so that this plastic mass tends to move the tension anchor 46 as a whole away from the flange 44, and thereby exerts an additional axial tensile force on the retaining screw 86 so that it presses the grinding wheel 22 firmly against the flange 24 via the thrust bearing 94 and the clamping flange 82 and thus clamps the grinding wheel with the necessary force between the clamping flange 82 and the flange 24.

The advantageous effect of the two pressure cylinders working together can be seen in the fact that when the threaded bolt 88 begins to act on the piston rod 74 with its front surface 122, a slight rotation of the retaining screw 86 reduces both the first cavity 56 and the second cavity 70 and thus prestresses the plastic mass with high forces, the transmission ratio between the action of the piston 68 with a small piston area and the circular ring surfaces 54 and 38 acting as large piston areas also being effective. In addition, the plastic mass has a certain elasticity and thus serves as a volume-compressible elastic element, which allows the grinding wheel 22 to be held tensioned when the retaining screw 86 is turned on.

In addition, when the machine is running, the tool spindle 20 and thus also the plastic mass heats up, which then expands and thus increases the force on the clamping anchor 46. To the tightened state of the retaining screw 86 while working with the Invention To be able to fix the right angle grinder, the cover cap 106 is moved so far in the axial direction after turning that its internal ring gear 104 also comes into engagement with the toothing 102, so that the screw head 92 can no longer rotate relative to the clamping flange 82, whereby the latter, in turn, is held on the latter by the external toothing 98, which is in engagement with the internal toothing 42 of the tool spindle 20, so that overall the screw head 92 can no longer be rotated relative to the tool spindle 20.

In a second exemplary embodiment of the solution according to the invention shown in FIG. 2, insofar as the same parts are used as in the first exemplary embodiment, they are provided with the same reference numerals, so that reference can be made to the first exemplary embodiment with regard to their description.

In contrast to the first embodiment of the angle grinder according to the invention, a piston ring 130 is provided at a distance from the step surface 38 and extends between the widened section 36 of the coaxial recess 32 and the lateral surface 52 of the center piece 48, which seals between these two surfaces and is sealed by means of disc springs 132 is supported on the step surface 38. The first cavity 56 'of the second embodiment is therefore not limited by the step surface 38, but by a piston ring surface 134 facing the annular surface 54.

The plate springs 132 have the task of acting as an additional elastic element when tightening the retaining screw 86, so that when the threaded bolt 88 acts on the piston surface 74 with its front surface 122, further rotation is possible by a considerable angle, since the tightening of the Retaining screw 86 is not limited by the elasticity of the plastic mass, but first the disk springs 132 are compressed when the screw is turned further until the piston ring 130 is supported by the stepped surface 38 via the compressed disk springs 132. Only then is there a slight compression of the plastic mass arranged in the first cavity 56 ', the second cavity 70 and the connecting channels 66 in order to achieve a final tensioning of the grinding wheel 22.

Furthermore, the thrust bearing 94 is sealed against contamination by a felt ring 95 surrounding it.

In a third exemplary embodiment of the device according to the invention, shown in FIG. 3, insofar as the same parts are used, they are also provided with the same reference numerals, so that reference can be made to the first exemplary embodiment with regard to their description.

In contrast to the first and second exemplary embodiments, the holding presses in the third exemplary embodiment screw 86 does not have its front surface 122 on the piston rod 74. The retaining screw is rather provided with an axial bore 140 penetrating it, which has an internal thread 142. A threaded spindle 144 can be screwed into this internal thread 142, which extends through the entire axial bore 140 and acts on the piston rod with its end 146 facing the piston rod 74. The threaded spindle 144 is connected to an actuating wheel 148 which is arranged on a side of the screw head 92 opposite the clamping flange 82. By turning the actuating wheel 148, the threaded spindle 144 can now be screwed into the internal thread 142 until the actuating wheel 148 abuts the screw head 92. On the other hand, by unscrewing the threaded spindle 144 in the internal thread 142, the actuating wheel can have an increasing distance from the screw head 92.

In addition, the actuating wheel is in turn overlapped by a cover cap 106 ', which has an internal ring gear 104', which can be brought into engagement with both a radially outer toothing 150 of the actuating wheel 148 and a radially outer toothing 152 of the screw head 92, however axial displacement of the cover cap 106 'away from the actuating wheel 148 is only engaged with the toothing 150, so that the actuating wheel 148 is freely rotatable relative to the screw head 92.

A grinding wheel 22 is fastened with the third exemplary embodiment in such a way that the threaded spindle 144 is first unscrewed, so that the actuating wheel 148 is at a distance from the screw head 92. The screw 86 with the threaded bolt 88 is then screwed into the threaded bore 76 until the clamping flange 82 bears the grinding wheel 22 against the flange 24 and the end 146 of the threaded spindle 144 bears against the piston rod 74 and begins to act on it.

In this state, the screw 86 itself is no longer rotated, but only the actuating wheel 148 is rotated, so that the threaded spindle 144 screws into the internal thread and the end 146 of which presses the piston rod 74 and the piston 68 in the direction of the tension anchor head 50. As a result, the second cavity 70 is reduced and the displaced plastic mass attempts to expand in the first cavity 56, which results in a slight displacement of the entire tension anchor 46 away from the flange 24 and thus in a movement of the entire screw 86 with the tension flange 82 in the direction leads to the flange 24, so that thereby the grinding wheel 22 is clamped firmly. The actuating wheel 148 is preferably turned in until it comes into contact with the screw head 92.

In the case of the clamping described above in the context of the third exemplary embodiment, in particular the transmission ratio between the piston surface of the piston 68 and the annular surface 54 and the step surface 38 comes into play, which is preferably selected in the order of 1:10, so that the actuating wheel 148 is screwed in with the threaded spindle 144 tenfold Clamping force on the screw head 92 and thus on the clamping flange 82 leads.

In this screwed-in state, the actuating wheel 148 can also be fixed in turn by moving the cover cap 106 'in the direction of the screw head 92 on the screw head 92 itself, so that loosening of the actuating wheel is avoided while working with such an angle grinder.

In this third exemplary embodiment, the recess 32 of the tool spindle 20 is advantageously closed at the end 34.

Claims (35)

1.Device for clamping a disk-shaped tool on a motor-driven tool spindle of a hand-held power tool, in particular a grinding wheel on an angle grinder, with an axially displaceable and rotatably connected clamping anchor in the tool spindle provided with an axial recess, with one at the free end of the clamping anchor releasably attachable clamping flange, with an abutment arranged on the tool-side end of the tool spindle and with a device which can be actuated by means of a manual actuation mechanism for releasably pressing the clamping flange against the abutment with intermediate clamping of the tool, characterized in that the device comprises a first pressure cylinder, comprising a first cavity (56) between the tension anchor (46) and the tool spindle (20), a second pressure cylinder, comprising a second cavity arranged in the tension anchor (46) or the tool spindle (20) m (70), and a connecting channel (66) between the two cavities (56, 70), that the second pressure cylinder comprises a piston (68) delimiting the second cavity (70) and that the piston (68) for releasably tensioning the Tool (22) from one end of the tool spindle (20) on the tool side can be adjusted by means of the manual actuation mechanism and can be fixed in its position exciting the tool (22). 2. Device according to claim 1, characterized in that the first cavity (56) is defined by mutually facing and axially spaced boundary surfaces (38, 54) of the tool spindle (20) and the clamping anchor (46). 3. Device according to claim 2, characterized in that the boundary surface (54) of the tension anchor (46) faces the tool (22), while the boundary surface (38) of the tool spindle (20) is arranged facing away from the tool (22). 4. Device according to one of the preceding claims, characterized in that an adjustment of the piston (68) via a tool-side open and extending to the piston bore (62) in the clamping anchor (46) or in the tool spindle (20), which is the Hand-operated mechanism reaches through. 5. Device according to claim 1, characterized in that the manual actuation mechanism is arranged in a tool-side area of the tension anchor (46) or the tool spindle (20). 6. Device according to claim 4, characterized in that the manual actuation mechanism of the factory Tool spindle (20) facing away from the tool (22) forth is accessible for operation. 7. Device according to claim 2, characterized in that the manual actuating mechanism can be operated via a holding device (84) which can be detachably fastened to the tension anchor (46) for fastening the tension flange (82) on the tension anchor (46). 8. Device according to one of the preceding claims, characterized in that the manual actuating device comprises an adjustable, the piston (68) for tensioning the tension member (86, 144). 9. Device according to claim 5, characterized in that the tensioning member (86, 144) has a surface which is oriented obliquely to an adjustment direction of the piston (68). 10. The device according to claim 5, characterized in that the tendon (86, 144) has a thread. 11. Device according to one of claims 8 to 10, characterized in that the clamping member (86, 144) is arranged on the holding device (84). 12. Device according to one of claims 7 to 11, characterized in that the holding device (84) comprises the clamping flange (82). 13. Device according to one of claims 7 to 12, characterized in that the holding device (84) comprises a holding member (86) which can be fastened in a form-fitting manner against axial displacement on the tension anchor (46). 14. Device according to claim 13, characterized in that the holding member (86) can be screwed into the tension anchor (46). 15. The device according to claim 14, characterized in that the tendon and the holding member are the same screw (86). 16. The device according to claim 15, characterized in that the screw (86) in a first (80) and an adjoining second threaded section (78) of the tension anchor (46) can be screwed in and that when screwing into the second threaded section (78) the piston (68) can be actuated. 17. Device according to one of claims 13 to 16, characterized in that on the holding member (86) of the clamping flange (82) is rotatably held in the direction of the tool (22) so that it can be acted upon. 18. Device according to claim 17, characterized in that an axial pressure bearing (94) is arranged between the holding member (86) and the clamping flange (82). 19. Device according to one of claims 17 or 18, characterized in that the clamping flange (82) through Form-locking elements (42, 98) on the tool spindle (20) can be fixed in a rotationally fixed manner. 20. Device according to one of claims 13 to 19, characterized in that the clamping member (86) on the clamping flange (82) can be secured against rotation. 21. The device according to claim 20, characterized in that the clamping member (86) can be positively secured to the clamping flange (82). 22. The device according to claim 21, characterized in that the clamping member (86) can be secured by a locking element (106) which can be displaced in the axial direction. 23. The device according to claim 22, characterized in that the securing element (106) is held in a rotationally fixed and axially displaceable manner on the tensioning member (86) or on the tensioning flange (82) and with a gear ring of the tensioning flange (102) which is coaxial with its axis of rotation (30) or of the tendon (100) can be brought into engagement. 24. Device according to one of claims 20 to 23, characterized in that the securing element (106) can be locked in its position securing the tensioning member (86). 25. Device according to one of claims 8 to 14, characterized in that the clamping member (144) relative to the holding member (86) is adjustable. 26. The device according to claim 25, characterized in that the clamping member (144) can be screwed into the holding member (86). 27. Device according to one of claims 25 or 26, characterized in that the clamping member is a threaded spindle (144) with an actuating element (148) projecting over the holding member (86). 28. Device according to one of claims 25 to 27, characterized in that the clamping member (144) by a securing element (106 ') is rotatably fixed to the holding member (86). 29. Device according to one of the preceding claims. characterized in that the first and second cavities (56, 70) and the connecting channel (66) are filled with a plastic mass for hydraulic pressure transmission. 30. The device according to claim 29, characterized in that the plastic mass comprises polyvinyl chloride with a relatively low degree of polymerization. 31. Device according to one of claims 1 to 28, characterized in that the first cavity (56), the second cavity (70) and the connecting channel (66) are filled with a viscous mass. 32. Device according to claim 31, characterized in that the viscous mass is a silicone mass, in particular a silicone lubricant. 33. Device according to one of the preceding claims, characterized in that an axial displacement of the clamping flange (82) relative to the tool spindle (20) allowing elastic element (130, 132) is provided. 34. Device according to claim 33, characterized in that the elastic element (130,132) when compressing the tool (22) is compressible to inelasticity. 35. Device according to claim 33 or 34, characterized in that the elastic element is a volume-elastic element (130, 132) arranged in one of the cavities (56).

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