Claims
- 1. In an apparatus for making plastic bags from a continuous film of material comprising a sealing drum having at least one seal bar for imparting transverse seals to the film at regularly spaced intervals and a perforator having a rotatable perforator blade for imparting transverse perforations to the film at regularly spaced intervals, the improvement comprising:
- means for applying registration marks to the film at regularly spaced intervals;
- means for generating a signal representative of the position of each registration mark;
- means for generating a signal representative of the position of each perforation;
- means for generating a positional reference signal against which each registration mark signal can be compared with each perforation signal;
- means responsive to the positional reference signal generating means, the registration mark signal means and the perforation signal means for determining a positional difference between each registration mark and each perforation;
- means for rotating the perforator blade, the rotating means having a predetermined cycle length;
- means for computing a perforation offset value as a function of a desired bag length, the cycle length and a distance between the registration mark signal means and the perforation signal means;
- means for comparing the positional difference with the perforation offset value and applying a difference therebetween to the cycle length of the rotating means to thereby maintain a desired spacing between each perforation and each registration mark.
- 2. The apparatus of claim 1, wherein the means for adjusting the position of the perforator blade is a servo motor.
- 3. The apparatus of claim 2, wherein the positional reference signal generating means comprises an encoder.
Parent Case Info
This application is a continuation-in-part application Ser. No. 08/023,992 filed on Feb. 26, 1993; now U.S. Pat. No. 5,292,299 which is a continuation-in-part of application Ser. No. 07/981,967 filed on Nov. 25, 1992now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (6)
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0545057 |
Jun 1993 |
EPX |
A2030599 |
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DEX |
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Continuation in Parts (2)
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Number |
Date |
Country |
Parent |
23992 |
Feb 1993 |
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Parent |
981967 |
Nov 1992 |
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