In numerous fields of installation manufacturing, an undesired static friction leads to negative effects which can often be compensated only with large technical expenses.
E.g., during winding up of a cold strip, the reel mandrel is hydraulically restrained with inwardly located wedge surfaces. After the winding-up, the locking segments should be returned in their initial position by the circumferential pressure of the wound-up strip to thereby release the reel awe. However, though the inclination of the wedge surfaces lies in the vicinity of the static friction angle, it often occurs that because of an insufficient lubrication, the segments do not collapse and the coil is not released.
The state of the art shows examples of releasing the self-locking effect of expansion elements by inducing vibrations.
A document DE 21 63 971 A1 from another field discloses a method of reducing friction between a thread and thread guiding parts of textile machines. To this end, a thread is tangentially wound on a drum and is drawn off axially from the drum by a brake ring which is formed by a base ring that surrounds the drum at a distance therefrom, and elastic separate fingers distributed over the circumference of the base ring at a distance from each other and extending therefrom toward a surface of a storage drum, with the fingers extending inwardly from the base ring along a virtual conical surface and inclined in the circumferential direction in the direction of the relative circulation of the thread about the drum, with the thread overlapping the fingers, the free ends of which are supported against a drum shoulder, so that the thread, upon sliding over the fingers, generates vibrations.
Document JP 60244764 discloses a device for placing and retaining empty bobbins between a support and a handle. The support handle is pressed back by a drive in order to bring the empty bobbins in contact with a functional roller. A vibration produced thereby is detected by a vibration detector that is arranged on the support arm. The vibration detector is connected with a vibration mode comparator for comparing amplitude at a time A and B with a predetermined reference amplitude. In this way, it can be determined whether the empty bobbin is fixedly mounted on the support arm or not.
Document DE 22 23 195 A1 describes a method of and an apparatus for a non-thermal release of mechanical connections. To this end, one of the connected parts is subjected to mechanical vibrations in the frequency range of the ultrasound for releasing the connection. There is provided a clamping device for clamping at least one of the plates of the to-be-loosened element. The clamping device is fixedly mounted on a cone-shaped mandrel the other end of which is fixedly connected for transmission of vibrations, with a mechanical transmitter that is amplitude-controlled and operates in the frequency range of the ultrasound.
Proceeding from the above-discussed state of the art, the object of the invention is to provide a method and a device suitable to release, during winding of a cold strip, the reel mandrel, which is hydraulically restrained by inwardly located wedge surfaces to such an extent that the locking segments would slide back in the initial position, so that the self-locking effect is released or lifted off, which enables removal of a coil from the mandrel practically without any problem with the use of non-complicated and low-cost means.
To achieve this object, the method according to the present invention contemplates that the self-locking effect of the expansion elements is lifted off at least partially or completely by application of longitudinal vibrations acting in the axial direction.
In the device according to the invention, a vibrator is provided at the end side of the reel mandrel. Suitably, compressed air is fed to the vibrator through a rotary feeding conduit or a quick-acting coupling for its excitation. As vibrators, pneumatic turbo-vibrators or pneumatic impact vibrators can be used.
These vibrations convert static friction between the wedge surfaces of the expansion elements into a sliding friction with a noticeably reduced friction coefficient, so that the reel mandrel is released form the circumferential pressure of the wound-up coil, and the expansion elements collapse independent on their lubrication condition, and the coil is released.
Below, the inventive method will be described with reference to an embodiment of a device suitable for carrying out the method.
The drawings show:
According to
According to
The curve B (sliding friction) ascents, in the range of the gravity force between 115 N and 250 N, by about 60 N, whereas in the following range of the gravity forces between 250 and 425 N, the tensile forces are simply increased by a small amount of 10 N. However, it is here that the friction coefficient clearly exceeds μ=0.2.
The corresponding values of the curve C (vibration) show, in contrast, an almost linear curve course, with a nearly constant friction coefficient μ=0.12.
As a vibrator, advantageously, a pneumatic impact vibrator is used. Its vibration reduces friction between the wedge surfaces S of the expansion elements to such an extent that the reel mandrel 1 is freed from the circumferential pressure of the wound strip, and the expansion elements collapse and release the coil, without any regard to their lubrication condition.
The vibrator V, which is shown in
In the present case, a pneumatic impact vibrator for generating longitudinal impact pulses is used. Its function resembles that of a so-called compression air hammer (percussion hammer-translator's remark) in which a working tool, such as a hammer, which is loosely displaced in a housing, reciprocates under action of air.
The vibrator includes a flying piston 2 with cross-over edges for reciprocal action.
The inner chamber of the vibrator 1 is closed with a cover 3. On the cover, there is arranged a ventilator unit 5, 6, 7 that can be open or closed for a preliminary setting of the percussion action of the impact body 2.
The compressed air flows from a feeding channel 8 through the body of the vibrator 1 and escapes, after exciting the impact body 2, as shown in the drawing, in the atmosphere upon opening of a valve 6.
The inventive method and the corresponding device ideally solve the set-forth object.
Number | Date | Country | Kind |
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10 2004 034 091 | Jul 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2005/006674 | 6/21/2005 | WO | 00 | 6/10/2008 |
Publishing Document | Publishing Date | Country | Kind |
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WO2006/007920 | 1/26/2006 | WO | A |
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4429838 | Lenk et al. | Feb 1984 | A |
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4715553 | Hatakeyama et al. | Dec 1987 | A |
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6216977 | Setzer et al. | Apr 2001 | B1 |
6405970 | Ueyama | Jun 2002 | B1 |
Number | Date | Country |
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1357066 | Jun 1974 | GB |
1375589 | Nov 1974 | GB |
Number | Date | Country | |
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20080258000 A1 | Oct 2008 | US |