Clamping device for a shaft and method for clamping same

A device and a method for holding a shaft, preferably a winding shaft, hold the shaft in a clamping jaw. A lever, which is rotationally supported about a first axis, is moved in reference to the shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national stage of PCT/EP2010/067238 filed Nov. 10, 2010 and published in German, which claims the priority of German number 10 2009 052 411.8 filed Nov. 10, 2009, hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to a clamping device for a shaft and a method for clamping thereof.

The device and method can firstly be used in any fields of technology. However, they are particularly suitable for storing and holding winding shafts. Here, the winding shaft train is a particular place of application.

2. Description of the Prior Art

In order to hold winding shafts at one side in the winding shaft train, clamping sockets with high clamping force are required.

For this purpose, prior art uses e.g., wedge-hook sockets, which are operated hydraulically and/or with very large pneumatic cylinders.

Alternatively, clamping device are used which are closed by motor-force using spindles.

A disadvantage of the prior art clamping devices described above is that while wedge-hook sockets may apply strong clamping forces, they only show a short stroke. Furthermore, such devices are very expensive.

Another disadvantage of the above-described prior art devices is that when they are operated hydraulically, a hydraulic aggregate is required as well. Additionally, hydraulic aggregates are not very welcome in the production of, e.g., food films, which are wound onto the respective winding device.

Yet another disadvantage of the prior art clamping devices is that the large pneumatic cylinders used alternatively are very expensive.

And, still another disadvantage of the prior art clamping devices is that when using clamping devices with spindle drives, although large displacement paths are given, at standard construction size their clamping force is relatively low. Another problem is the wear and tear of the spindle drives caused by the use and opening of the clamping device due to friction.

The objective of the present invention is therefore to suggest a device which corrects the described disadvantages of the device of prior art or at least reduces them.

SUMMARY OF THE INVENTION

According to the invention, this objective is attained in accordance with the features described herein. Accordingly the device comprises a lever, which is supported rotational about an axis. By this measure, the forces can be increased and it is possible to yield a wide range of adjustment.

A locally fixed positioning and/or a first axis is advantageous, extending parallel in reference to the holding position of the shaft to be held in its socket.

It is particularly advantageous to provide a device for defining a second rotary axis, by which the second rotary axis can be defined for the lever, as needed. This device also comprises components necessary to quasi switch on a second rotary axis to the lever (“switchable additional rotary axis”). This may occur by a body, showing a round and/or curved surface, is made to contact the lever with said surface.

Alternatively or additionally a bore or recess may be provided in the lever, engaging a body which then defines the second axis.

In particular with regards to the second axis it may occur that no considerable rotary motion occurs with regards to its extent about the second axis, rather that it only serves to create leverage, by which adequate clamping forces can be applied.

Stops may be provided, which in turn may be mobile. When they can be fixed in the effective range of the lever, they may influence the pivotal motion that can be performed by said lever. It is advantageous for the lever to be pressed against a clamping jaw, which in turn fixates the shaft.

In the embodiment of the method according to the invention it is advantageous for the lever, which is supported pivotal about a first axis, to be moved in reference to the shaft. Generally, when fixating the shaft the lever is moved towards it and when the shaft is released again the lever is moved away. Prior to performing the rotary motion about the lever, said lever can perform a linear motion in reference to the shaft.

Additional exemplary embodiments of the invention are discernible from the description of the figures and the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows an illustration of the device according to the invention in a first operating position, in which the shaft8such as a winding shaft), is located in the clamping jaw3, without being held, here. Rails1are provided in the clamping device19, on which the sled2can glide back and forth in the vertical direction. Using this sled, the stops4, the clamping jaw3, and the first axis9of the lever5are mobile. Long opening paths can be yielded in the device shown when appropriately long rails1of this type are used. The lever5can be subjected to an operating power by the cylinder7, which preferably represents a pneumatic cylinder, via the piston14and the link13of the piston.

It is already discernible inFIG. 2how the piston14of the cylinder7is inserted into the cylinder (arrow15). Here, the motion of the sled2develops, indicated by the arrow16, by which the clamping jaw3is made to contact the shaft8.FIG. 3shows how the situation in the cylinder7changes by the continuous motion of the piston14indicated by the arrow15: After the translation of the sled has come to an end, because the clamping jaw3has reached the shaft, a minor additional rotation occurs, indicated by the arrow17, about the first axis9until the lever5reaches the left stop4′. The clamping forces upon the shaft8that can be created in this situation are limited, though, due to the lever ratio.

In this situation, the clamping disk6(i.e., a cam) is pivoted about the axis12into an operating position, as indicated by the arrow18. Here, a second rotary axis10is defined, shown by the circle10and the [circle]10would move along the contact surface between the two bodies5,6by the rolling motion of the lever5at the clamping disk6. In the present exemplary embodiment, here the lever5, the clamping disk6, and its link12form the device to define a rotary axis11. The link12is generally mounted in a fixed manner at the machine frame of the winding device and withstands large forces.

However, in the present exemplary embodiment no extensive motions are intended, rather the introduction of the second rotary axis10leads to a significant change of the lever ratios in reference to the situation inFIG. 3. Due to this circumstance the shaft8is clamped with a strong force when the piston14moves back out of the cylinder7, as indicated by the arrow20inFIG. 5. The forces are based on the distance21between the second rotary axis10and the linking point14as well as the distance22of the second rotary axis10and the first axis9orthogonally in reference to the effective direction of the force F.

In order to release the shaft8the processes occur in the inverse sequence. For reasons of illustration, the lever5located in front of the sled2is shown clear, thus without any colored areas, while components, such as the sled, are shown with colored areas.

Summarizing the following can be stated with regards to the embodiment of the clamping device19described:

Large displacement paths with strong clamping forces are yielded with a relatively small pneumatic drive (cylinder7) in the clamping device19shown.

Here, this clamping device19uses the following circumstances:1. Firstly, large displacement paths are yielded to close and/or open the clamping device via a simple displacement of the pneumatic cylinder (FIGS. 1 through 3).2. Then strong clamping forces are yielded by “adding or guiding thereto” an additional rotary point10and the lever ratios resulting therefrom.

The advantages of the device19therefore include:strong clamping forces can be yielded;large displacement paths can be yielded;small pneumatic drives can be used (e.g., small adjustment paths);by the additional rotary point10a mechanic safety against opening the clamping device19is given in case of a loss of energy supply;the device19can be produced in a relatively cost-effective manner.

Additional advantages can be achieved when the incline of the clamping disk6is varied at its circumferential area23. When this incline is minor, e.g., immediately in the proximity of the point at which the shaft8is fixed (frequently at the point where the distance of the circumferential area23from the point of rotation12of the clamping disk6is greatest, preferably smallest in reference to the other circumferential areas), a strong closing force can be achieved with the clamping disk6as well.

LIST OF REFERENCE CHARACTERS

1Guiding Rails2Guiding Sled3Clamping Jaw/Accept for the Shaft84,4′ Stops5Clamping Lever6Cam (spiral)7Cylinder8Winding Shaft9First Axis10Second Axis11Device to Define a Rotary Axis12Point/axis of Rotation of the Clamping Disk13Link of the Piston to the Lever14Piston15Arrow16Arrow17Arrow18Arrow19Clamping Device20Arrow21Distance Between13and1022Distance Horizontal Between10and923Circumference of the Cam624Distance Between the Circumference23of the Cam6and the Point/Axis of Rotation12of the Cam6F Direction of Influence of the Clamping Force Upon the Shaft8