Film free end control apparatus and method for a stretch wrapping machine
OwnerStephen L. Hestoninventor
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Abstract
An apparatus and method for stretch wrapping of a palletized load uses film tension feedback derived from a film tension control load cell to control film dispensation. The load cell measures film tension and the film payout rates is determined by the film tension. Film tension values are used to determine when an out of bounds condition occurs, namely, when a film break has occurred, or when a possible film break is about to occur or when the film has been cut at the end of a wrapping cycle. To prevent film free end entanglement caused by a break, clamps engage the film so the film tail is controlled, eliminating the risk of recoil. The broken film tail may then be quickly and reliably reattached to the rotating load in a desired position.
Claims19
Apparatus for preventing film entanglement in a stretch wrapping machine for wrapping a load, comprising:
- a vertically movable dispensing head having at least one pair of driven pre-stretch rollers adapted to dispense film;
- a controller operatively coupled to the driven pre-stretch rollers;
- a film exit downstream of the pre-stretch rollers;
- a source of pressurized air delivering air through air jets trained on film exiting at the film exit to blow the film toward the load;
- a clamp assembly mounted in a fixed position on the dispensing head between the film exit and the load, the clamp assembly movable between a closed position gripping the film and an open position releasing the film;
- a film tension measuring device mounted to the dispensing head and configured to continuously measure film tension and transmit tension values to the controller;
- and
- a rotation drive adapted to provide relative rotation between the load and the dispensing head;
- wherein the controller commands film payout as a reaction to measured film tension values and, upon detection of a film break event based on tension values outside an acceptable tension range, concurrently stops film payout and closes the clamp assembly to grip the film while allowing the relative rotation to continue.
A method for preventing film entanglement in a stretch wrapping machine for wrapping a load, comprising:
- providing relative rotation between a film dispensing head and a load;
- dispensing film from the dispensing head through driven pre-stretch rollers to a film exit;
- blowing pressurized air through air jets trained on film at the film exit to attach the film to the load;
- continuously measuring tension in the film and transmitting tension values to a controller;
- dispensing film at a rate determined as a reaction to the measured tension values;
- and
- if the measured tension values are above an upper limit value or below a lower limit value of an acceptable tension range stored in the controller, concurrently stopping film dispensation and closing a clamp assembly fixed to the dispensing head to grip the film while allowing relative rotation to continue.
Dependencies are inferred from the claim text.