EP3411185B1 - Clamping device - Google Patents

Description

The present invention relates to a clamping device for axially clamping a disk-shaped tool, preferably a cutting disk, on a flange of a driven spindle of an electric hand-held power tool. The hand-held power tool can be, for example, a cut-off machine.

In the conventional design of the disc-shaped tools, a drive torque applied to the spindle can only be transmitted to the disc-shaped tools in a frictional manner, since these only have a simple, central bore as an interface and therefore do not offer any contact surfaces for a positive connection.

Fastening is carried out by axially clamping one or more disc-shaped tools against a rear flange on the spindle. The task of the clamping element is therefore to apply a sufficient axial clamping force so that the force and torque can be transferred from the electric hand tool to the disc-shaped tool. Sufficient clamping is characterized by the disc-shaped tools not slipping on the drive spindle.

Various clamping devices of the type mentioned are known from the prior art. These are, for example, clamping devices that require the use of an additional tool. Disc-shaped tools on electric hand-held power tools (e.g. angle grinders, cut-off machines) are usually mounted with nuts on the drive spindle and tightened with a separate wrench (e.g. two-hole or open-end wrench). The big disadvantage of such clamping devices is the separate key that has to be carried in addition to the actual system and can be lost.

Also known from the prior art are automatically tightening clamping devices with release aids. These are from the German patent specifications DE 38 24 040 C1 and DE 10 311 491 B4 For example, clamping nuts are known, which are initially fixed hand-tight and rely on the self-tightening effect caused by the reversal thrust when the device starts up. This effect is based on the inertia of the disc-shaped tools and the clamping nuts and the reaction forces of the disc-shaped tools during cutting in the underground. There is a frictional power transmission between the disc-shaped tools, the clamping nut and the rear flange. The reaction forces cause the clamping nut to become increasingly clamped against the rear flange via the washers. For loosening, a technical loosening aid is integrated into these clamping nuts, which makes it possible to remove the pre-tension of the nut before it is unscrewed.

The disadvantage of such clamping devices is that the level of clamping force achieved is not limited by the automatic tightening and as a result the clamping nut can be pre-tensioned to such an extent that the release mechanism cannot be loosened by hand.

Another disadvantage is that the reaction moments that arise due to inertia in the run-out of the hand-held power tool are also transferred to the clamping nut, which can lead to the clamping nut and the disc-shaped tools running off automatically, particularly in hand-held power tools with an active run-out brake. The running parts pose a danger to the operator of the hand-held power tool.

Another possibility known from the prior art to make a separate key unnecessary is to design the clamping device in such a way that manual force is sufficient during assembly to achieve sufficient clamping of the disc-shaped tool on the hand-held power tool. To do this, either the hand force can be increased and/or the friction losses can be minimized in order to achieve a higher clamping force from the same, limited hand force.

A known solution for improved utilization of the tightening torque in a high axial clamping force during clamping consists of a secondary thread in which balls rotate, which becomes effective in the last phase of the clamping process. Such a solution is, for example, from the European publication EP 0 846 526 A2 known.

The disadvantage of this clamping device is that the dynamic reaction forces are not decoupled from the threaded section and the clamping device can therefore, on the one hand, tighten excessively automatically and, on the other hand, can expire if the spindle stops abruptly.

Another solution known from the prior art for improving the conversion of a tightening torque into a high axial clamping force when clamping is to select a thread with a smaller diameter and a small pitch and also to minimize the screw head friction via a rolling bearing. Furthermore, dynamic reaction forces of positive locking elements between the clamping disk facing the cutting disks and the Drive spindle intercepted, which prevents automatic tensioning and automatic unwinding. Such a clamping device from ITW Fixingssysteme GmbH Spit is known from the market.

Furthermore, the reveals EP 2 123 380 A1 , which forms the basis for the preamble of claim 1, a fastening device for a saw blade of a table saw, wherein the saw blade can rotate around a spindle.

It is therefore the object of the present invention to create a clamping device through which the disadvantages described above can be eliminated and in particular jamming between a securing element of the clamping device and a corresponding securing element provided on a spindle can be avoided.

The task is solved by the subject matter of independent claim 1. Advantageous embodiments of the subject matter are contained in the dependent claims.

The object is achieved in particular in that a clamping device is provided for axially clamping a disk-shaped tool, preferably a cutting disk, on a flange of a drivable spindle of a hand-held power tool, with a clamping disk which rests frictionally on the tool in the clamped state, a central screw which is in a receiving opening equipped with a thread, which is formed in an end face of the spindle, can be screwed in, with an operating element which can be connected to the screw in a rotationally fixed manner, so that a manual force introduced into the operating element is transmitted to the screw as a tightening torque, and a first Securing element which is designed to cooperate with a corresponding second securing element provided on the flange in such a way that when the screw is at least partially inserted into the receiving opening, the clamping disk is secured against rotation in a form-fitting manner relative to the flange, the tensioning disk being rotatable relative to the screw and the operating element . In addition, the operating element, the clamping disk and the first securing element are arranged coaxially to one another and one behind the other in a direction N on the screw, the screw and the operating element being able to be connected to one another as two independent components of the clamping device with a positive connection.

According to the invention, the first securing element of the clamping device is rotatable relative to the screw and is mounted in a rotationally fixed manner to the clamping disk. This can ensure that a torque applied by the user and acting on the screw or unit consisting of screw and operating element is converted into an axially acting one in a particularly efficient manner Clamping force is converted to secure the disc-shaped tool on the drivable spindle of the hand-held power tool.

The invention includes the knowledge that because the tension disk is freely rotatable relative to the screw or the driven unit consisting of screw and operating element, a relative position in the circumferential direction between tension disk and screw or between tension disk and operating element is not clearly defined. Thus, a position between the first securing element and the corresponding second securing element is not defined in position when the central screw is screwed into the threaded receiving opening formed on the end face of the spindle.

According to an advantageous embodiment of the present invention, it can be provided that the first securing element is designed in the form of a sleeve with a polygonal inner profile and the second securing element contains an outer profile corresponding to the polygonal inner profile of the first securing element, so that the first securing element can be pushed onto the second securing element is. By pushing the first securing element onto the second securing element, a precise arrangement and thus a secure interaction of the two securing elements with one another can be achieved.

There is also the advantage that the spindle of the hand-held power tool can be designed to be particularly simple in that it remains free of moving parts that promote synchronization.

In order to ensure a secure and, in particular, precisely fitting arrangement of the tension disk to the first and second securing element, it can be provided according to a further advantageous embodiment of the present invention that the tension disk contains a central recess and the first security element contains an outer profile corresponding to the central recess, so that the first securing element can be inserted into the tension disk.

According to a further advantageous embodiment of the present invention, it can be provided that the tension disk and the first securing element are designed in one piece. This can ensure an even better transmission of force or torque from the tension disk to the first securing element.

In addition, in a further advantageous embodiment of the present invention it can be provided that the screw is designed in such a way that a thread of the screw can only be engaged in the thread of the receiving opening when in a assembled state of the tensioning device, the first securing element at least partially interacts positively with the second securing element. This can ensure that the user can only turn the screw correctly into the thread of the receiving opening if the first and second securing elements are properly arranged relative to one another or the clamping device is correctly assembled. In other words: when the first and second securing elements are connected to one another in a form-fitting manner.

It has proven to be advantageous if the operating element is designed as a cover, which preferably encloses the clamping disk at least in sections.

In a particularly advantageous embodiment of the present invention, the clamping device has a bearing. Preferably the bearing is an axial needle bearing. The bearing is arranged for the rotational decoupling of the screw and the clamping disk, in particular but preferably not exclusively if the clamping disk is secured against rotation in a form-fitting manner to the flange.

It has proven to be particularly advantageous if the operating element, the tension washer and the first securing element are arranged coaxially with one another on the screw. Preferably, the operating element, the clamping disk and the first securing element are held in or at least in sections in the operating element by at least one securing ring.

Further advantages result from the following description of the figures. Various exemplary embodiments of the present invention are shown in the figures. The figures, the description and the claims contain numerous features in combination. The person skilled in the art will also expediently consider the features individually and combine them into further sensible combinations.

In the figures, identical and similar components are numbered with the same reference numerals.

Show it:

Fig. 1

a side view of a clamping device according to the invention with a disk-shaped tool in an assembled state of the clamping device;

Fig. 2

a perspective view of the clamping device in a disassembled state of the clamping device without the disc-shaped tool;

Fig. 3

a perspective view of the tensioning device in a disassembled state of the tensioning device;

Fig. 4

a side sectional view of the clamping device along the section line A - A in Fig. 1 ;

Fig. 4a

a sectional view of the clamping device along the section line B - B in Fig. 4 ;

Fig. 5

another side sectional view of the clamping device along the section line A - A in Fig. 1 ;

Fig. 5a

a sectional view of the clamping device along the section line B - B in Fig. 5 ;

Fig. 6

a perspective view of the spindle;

Fig. 7

a side sectional view of the spindle;

Fig. 8

a perspective view of the first security element; and

Fig. 9

another perspective view of the first security element.

Examples:

A clamping device 1 according to the invention is in Fig. 1 shown in an assembled state.

The tensioning device 1 essentially contains a screw 2, an operating element 3, a first running disk 4, an axial needle ring 5, a second running disk 6, a tension disk 7, a first securing element 8 and a counter tension disk 9 (cf. Fig. 1 , 2 , 3 ). The clamping device 1 interacts with a spindle 10 of a hand-held power tool, not shown in the figures. The spindle 10 further contains a second securing element 12, which is located on a flange 13 of the spindle 10 (cf. Fig. 2 , 3).

The clamping device 1 is used to axially clamp a disc-shaped tool 14 on the flange 13 on the right side Fig. 1 driven spindle 10 shown. The driven spindle 10 is associated with a hand-held power tool, not shown in the figures, which can be, for example, a cut-off grinder. The disc-shaped tool 14 can be, for example, a plate-shaped grinding wheel.

However, it is also possible for the disc-shaped tool 14 to be a flat cutting disc. The hand tool not shown can be an angle grinder or something similar. Alternatively, the clamping device according to the invention can also be implemented in a non-hand-held machine tool.

The clamping device 1 contains a clamping disk 7, which, when the clamping device 1 is assembled or clamped, rests frictionally on the tool 14, for example a plate-shaped grinding wheel, in order to clamp it on the spindle 10 of the hand-held power tool, not shown.

The screw 2 is a central screw that holds the entire clamping device 1 together when assembled. The screw 2 contains a screw head 2a and a thread 2b, which can be screwed into a thread 15 which is formed in a receiving opening 16 on a free end face 17 of the spindle 10.

The control element 3 is essentially in the form of a cover with a central recess 18. The recess 18 serves to accommodate and positively connect the control element 3 to the screw 2. Due to the positive connection of the control element 3 and screw 2, the control element 3 is connected to the screw 2 in a rotationally fixed manner, so that one can be inserted into the control element 3 by rotating the control element 3 Manual force introduced in the radial direction R is transferred to the screw 2 as a tightening torque. The positive connection between the screw 2 and the control element 3 is achieved via a corresponding profile device on the central recess 18 of the control element 3 and the screw head 2a of the screw 2.

The first securing element 8 of the tensioning device 1 is in Fig. 1 illustrated embodiment is designed as a sleeve with a hexagonal inner profile 19 (see also Fig. 8 and 9 ). It is essentially like a nut with a hexagon socket. In addition, the first securing element 8 contains a polygonal outer profile 20 at one end 8a. As in particular in Fig. 8 shown, the polygonal outer profile 20 is essentially a square profile with beveled corners.

The tension disk 7 contains a substantially square recess 21 in the middle. The shape of the recess 21 corresponds to the square outer profile 20 of the first securing element 8, so that the square outer profile 20 of the first security element 8 can be inserted into the square recess 21 of the tension disk 7 . As a result, the first securing element 8 and the tension disk 7 can be connected to one another in a form-fitting manner.

Alternatively, the first securing element 8 and the tension disk 7 can also have other mutually corresponding outer profiles and recesses. Furthermore, the first securing element 8 and the tension disk 7 can also be designed in one piece or connected to one another in a materially bonded manner.

A second securing element 12 corresponding to the first securing element 8 is arranged on the flange 13 of the spindle 10. Like especially in the Fig. 2 , 3 , 6 shown, the second security element 12 contains a hexagonal outer profile 22 corresponding to the hexagonal inner profile 19 of the first security element 8. If the hexagonal inner profile 19 of the first security element 8 is in engagement with the hexagonal outer profile 22 of the second security element 12, it is not just the first security element 8 to the second securing element 12 but also the tension disk 7 to the flange 13 secured against each other in a form-fitting manner.

As already mentioned above, in the exemplary embodiment shown here, this is implemented in such a way that the outer profile 20 of the first securing element 8 protrudes into the corresponding recess 21 of the tension disk 7, the inner profile 19 of the first securing element 8 is pushed onto the outer profile 22 of the second securing element 12 and the Screw 2 in the N direction through the clamping disk 7, the first securing element 8, the disk-shaped tool 14 and into the receiving opening 16 of the spindle 10 equipped with the thread 15 (cf. Fig. 3 ). The tension disk 7, the first securing element 8 and the second securing element 12 are thus connected to one another in a form-fitting manner.

According to the invention, the first securing element 8 of the tensioning device 1 is rotatable relative to the screw 2 and is mounted in a rotationally fixed manner relative to the tension disk 7.

In the present case, the clamping device 1 has a bearing 23 in the form of an axial needle bearing, which is supported between two running disks 24, 25. The bearing 23, which is designed as an axial needle bearing, serves to decouple the rotation of the screw 2 and the clamping disk 7 when the clamping disk 7 is positively secured against rotation to the flange 13.

Like that too Fig. 1 can be removed, the screw 2, the control element 3, the two running disks 24, 25, the first securing element 8 and the tension disk 7 are arranged coaxially to one another.

When assembled (cf. Fig. 2 ) the control element 3, the clamping disk 7, the first securing element 8, the two running disks 24, 25 and the axial needle bearing 23 are arranged on the screw 2 and secured thereon by a locking ring 26 in the form of a snap ring. An additional ring 27 serves to deflect the axially acting force in the assembled state of the clamping device 1 in such a way that a radial force component is created on the locking ring 26.

Claims (8)

1. Clamping apparatus (1) for axially fixedly clamping a disc-shaped tool (14), preferably a circular saw, on a flange (13) of a drivable spindle (10) of a hand-held power tool, with

   a clamping disc (7) which bears against the tool (14) in a frictionally locking manner in the fixedly clamped state,

   a central screw (2) which can be screwed into a receiving opening (16) which is equipped with a thread (15) and is configured in an end side of the spindle (10), with an operating element (3) which can be connected to the screw (2) fixedly for conjoint rotation, with the result that a manual force introduced into the operating element (3) is transmitted as tightening torque to the screw (2), and

   a first securing element (8) which is configured to interact with a corresponding second securing element (12) provided on the flange (13), in such a way that, when the screw (2) is introduced at least partially into the receiving opening (16), the clamping disc (7) is secured against rotation in a positively locking manner with respect to the flange (13), the clamping disc (7) being rotatable relative to the screw (2) and to the operating element (3), the first securing element (8) of the clamping apparatus (1) being mounted rotatably relative to the screw (2) and fixedly for conjoint rotation relative to the clamping disc (7),

   characterized in that

   the operating element (3), the clamping disc (7) and the first securing element (8) are arranged on the screw (2) coaxially with respect to one another and behind one another in a direction (N), it being possible for the screw (2) and the operating element (3) to be connected to one another as two independent constituent parts of the clamping apparatus (1) by way of a positively locking connection.
2. Clamping apparatus (1) according to Claim 1,
   characterized in that
   the first securing element (8) is configured in the form of a sleeve with a polygonal inner profile (19), and the second securing element (12) comprises an outer profile (22) which corresponds to the polygonal inner profile (19) of the first securing element (8), with the result that the first securing element (8) can be pushed onto the second securing element (12).
3. Clamping apparatus (1) according to Claim 1 or 2,
   characterized in that
   the clamping disc (7) comprises a central recess (21), and the first securing element (8) comprises an outer profile (20) which corresponds to the central recess (21), with the result that the first securing element (8) can be introduced into the clamping disc (7).
4. Clamping apparatus (1) according to Claim 1 or 2,
   characterized in that
   the clamping disc (7) and the first securing element (8) are configured in one piece.
5. Clamping apparatus (1) according to one of the preceding claims,
   characterized in that
   the screw (2) is configured in such a way that a thread (2a) of the screw (2) can engage into the thread (15) of the receiving opening (16) only when, in an assembled state of the clamping apparatus (1), the first securing element (8) interacts at least partially with the second securing element (12) in a positively locking manner.
6. Clamping apparatus (1) according to one of the preceding claims,
   characterized in that
   the operating element (1) is configured as a cover which encloses at least portions of the clamping disc (7).
7. Clamping apparatus (1) according to one of the preceding claims,
   characterized in that
   the clamping apparatus (1) has a bearing (23), preferably an axial needle bearing for rotary decoupling of the screw (2) and the clamping disc (7) when the clamping disc (2) is secured against rotation with respect to the flange (13) in a positively locking manner.
8. Clamping apparatus (1) according to one of the preceding claims,
   characterized in that
   the operating element (3), the clamping disc (7) and the first securing element (8) are held by way of at least one securing ring (26) in or at least in portions in the operating element (3).

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