Winding – tensioning – or guiding – Unwinding – With detector – indicator – or control
Patent
1997-10-08
2000-03-21
Jillions, John M.
Winding, tensioning, or guiding
Unwinding
With detector, indicator, or control
2425632, 2425645, B65H 1610, B65H 23185
Patent
active
060392851
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The invention relates to a device for unwinding a reel of web material in order to feed said material to a processing section, comprising a support for the reel, an unwinding member for unwinding said reel, and pressure means which causes said unwinding member to press on said reel, wherein the pressure applied on said reel varies with the diameter of said reel being unwound,
2. Background Art
An unwinding device of the above mentioned kind is disclosed in EP-A-0 321 887. This known device includes an arm on which an unwinding belt is supported. The position of the arm changes during unwinding, according to the diameter of the reel. The position of the arm with respect to the reel is such that the pressure exerted by the unwinding belt on the reel decreases when the diameter of the reel decreases.
Unwinding devices of this type are commonly used in paper processing lines, in which a reel of large diameter is formed into reels of smaller diameter, equal to the diameter of the finished product, which are then cut perpendicularly to their axis to produce rolls of toilet paper, kitchen towels and similar products.
Usually, the unwinding member in these unwinding devices is an endless flexible member that travels around a plurality of pulleys, at least one of which is motorized. The pulleys are carried by a movable arm. In some cases to the arm an actuator is attached which causes one part of the flexible member to press against the outer surface of the reel. Typically, the flexible member is a belt or a plurality of belts. However, it is quite possible for the unwinding member to take a different form, for example a rotating cylinder. In such a case, said rotating cylinder can still be carried by a movable arm which is operated by the actuator.
The diameter of the reels varies greatly during operation, from the starting diameter (2000-3000 mm) down to the diameter of the inner tubular core (about 80-450 mm). The pressure exerted by the unwinding member must be carefully gaged in order to prevent it exceeding the strength limits of the reel as the latter's diameter decreases, especially when the force exerted by the unwinding device is added to the weight of the reel, that is to say when the unwinding device presses on the reel from above. If the reel were to break during the operating phase, this would cause a considerable loss in production and loss of raw materials, and would pose a great danger to personnel. On the other hand, too low a pressure would give rise to difficulties in controlling the unwinding action during the initial phase and during changes in speed.
SUMMARY OF THE INVENTION
The subject of the present invention is an unwinding device of the type indicated at the outset that makes it possible to avoid the risk of incorrectly gaging the unwinding pressure applied to the reel and makes it easier to set the device, ensuring correct operation with reels of any diameter and at any stage of the unwinding cycle.
Basically, these and other objects and advantages--which will be quite evident to those skilled in the art on reading the following description--are achieved by providing, in combination with the unwinding device, an actuator which controls the pressure of the unwinding means on the reel and diameter detection means for adjusting the pressure applied to the reel as a function of the diameter of the reel being unwound, the pressure being reduced as the diameter decreases.
A transducer for detecting the diameter of the core is preferably provided. However, this is not strictly necessary, as will be explained below, since the diameter might be detected indirectly. If this transducer means is present, it could take the form of a position transducer which detects the position of the movable arm carrying said pulleys for deflecting the flexible member. It could also take the form of a cam profile solid to the arm carrying the unwinding means and directly controlling a proportional valve which causes a variation in the pressure applied.
Within the context of the pr
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Fabio Perini S.p.A.
Jillions John M.
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