Bag making machine control
A bag making machine for producing thermosplastic resin film bags including rollers for intermittently advancing a flat tubular web of thermoplastic resin film, a sealing assembly positioned downstream from the roller, a heated cutting bar having a sharp edge for providing efficient cutting and concomitantly preventing build-up of carbon by-product, roller elements for reversing the direction of advancement of the resin film, first drive elements for controllably driving the rollers in first and second directions and second drive elements for transversely driving the sealing and heated cutting bar toward and away from the flat web of thermoplastic resin film.
Advancement of the cutting edge and rapid retraction of the thermoplastic web during cycle interrupt has been difficult to achieve due to constraints associated with the air cylinder and other mechanisms employed in present bag making machines. These limitations inhibit the benefits associated with a self-cleansing heated cutting edge and a rapid bag making cycle.The difficulties suggested in the preceeding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness and product quality associated with present bag making machines. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that thermoplastic bag making machines appearing in the past will admit to worthwhile improvement.
It is therefore a general object of the invention to provide a novel thermoplastic bag making machine which will obviate or minimize difficulties of the type previously described.After reading and understanding the foregoing inventive bag making machine and control thereof, in conjunction with the drawings, it will be appreciated that several distinct advantages of the subject invention are obtained.Without ttempting to set forth all of the desirable features of the instant bag making machine and control, at least some of the major advantages of the invention include the unique control mechanism which obviates the mechanical restraints of previous drive methods of bag making machines. More specifically, use of a servo motor 14 regulated by the control method described herein eliminates unsatisfactory use of pulleys and brake and clutch mechanisms, which do not insure precise timing of operation.
Use of a servo motor 14 and control method allow fast retraction of a thermoplastic web 1 from the bag making station 3 during interruption of a bag making procedure. Rapid retraction of the thermoplastic web 1 insures maintenance of the integrity of the thermoplastic web 1 by isolating the thermoplastic web 1 from the adverse effects of heat emanating from the lower 21 and upper 23 seals bars of the bagging device 3 as well as radiant heat from the cutting edge 22.The subject control provides for essentially instantaneous advancement and retraction of the thermoplastic web 1 upon issuance of start and stop signals, respectively. The disclosed configuration allows for minimal timing errors of various components of the bag making machine, thereby increasing machine efficiency and reliability.
It is another object of the invention to provide a bag making machine which will allow for fast retraction of a thermoplastic resin web during interruption of the bag making procedure, in order to maintain the integrity of the end of the web.It is still another object of the invention to provide a bag making machine which will minimize timing errors associated with different operations of a bag making machine, thus increasing machine efficiency and reliability even at increased rates of bag production.FIG. 2(C) illustrates the direction of rotation of the drive roller 11 and nip roller 12 in the forward direction after resumption of a new bag making machine cycle.
It is a specific object of the invention to provide a bag making machine which will minimize undesirable effects caused by discontinuation of a bag making operation.
The moment a start signal is given to resume the operation of the bag making machine, the sequencer 19 drives the servo motor 14 of the intermittent feeder 2 to return the thermoplastic web 1 to its pre-interrupt position. Thus, as seen in FIG. 1, the drive roller 11 and nip roller 12 rotate in the arrow "c" direction to return the thermoplastic web 1 into the bag making station 3. When the thermoplastic web 1 is fed by a length set by the digital switch 16 of the digital pack 17 via a feedback pulse from the encoder 13, the servo motor 14 stops, returning to the state shown in FIG. 2 (A).
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