Plastic bag making apparatus

An apparatus is arranged to successively make plastic bags each of which has a shape of circumference. The apparatus comprises web feeding means by which a web material is intermittently fed for a length along a longitudinal feeding path. The web material comprises two or more layers of plastic film. Web cutting means is disposed along the feeding path. The web cutting means has a shape corresponding completely or incompletely to the shape of circumference of plastic bag so that the web material can be cut into the shape of circumference of plastic bag by the web cutting means whenever the web material is intermittently fed and temporarily stopped, to successively make the plastic bags with a waste kept continuous. The web cutting means comprises partially cutting means. The plastic bag has an upstream edge along which the web material is partially cut by the partially cutting means so that the plastic bag can be kept connected with the waste at the upstream edge of plastic bag. Drawing means is disposed downstream of the cutting means. The waste is diverged from the plastic bag, directed to and drawn by the drawing means after the web material is cut. Discharge means is disposed downstream of the cutting means. The plastic bag is directed to the discharge means without the waste. The plastic bag is then pulled by the discharge means to be torn from the waste at the upstream edge of plastic bag. The plastic bag is then discharged by the discharge means.

FIELD OF THE INVENTION

The invention relates to an apparatus for successively making plastic bags each of which has a shape of circumference.

PRIOR ART

There has been commercially available an apparatus for successively making plastic bags each of which has a shape of circumference, as disclosed in US-2001-0053737. The apparatus includes web feeding means by which a web material is intermittently fed for a length along a longitudinal feeding path. The web material comprises two or more layers of plastic film. The apparatus further includes web cutting means disposed along the feeding path. In the apparatus of the publication, the web material is cut partially or totally by the web cutting means whenever the web material is intermittently fed and temporarily stopped, to successively make plastic bags with wastes taken to pieces.

The apparatus is therefore problematic with respect to the wastes. In the apparatus of the publication, the wastes are pulled by waste removing means and torn from the web material to be removed. However, it is then required to suitably collect and treat the wastes. In addition, the wastes may be too small to be pulled and torn by the waste removing means. The wastes may be particular in shape which cannot be pulled and torn by the waste removing means.

It is therefore an object of the invention to provide a new and improved apparatus for successively making plastic bags each of which has a shape of circumference, to overcome the above problems.

Other object of the invention is to provide the apparatus which can successively make the plastic bags with a waste kept continuous to conveniently treat the waste.

SUMMARY OF THE INVENTION

According to the invention, the apparatus comprises web feeding means by which a web material is intermittently fed for a length along a longitudinal feeding path. The web material comprises two or more layers of plastic film.

The apparatus further comprises web cutting means disposed along the feeding path. The web cutting means has a shape corresponding completely or incompletely to the shape of circumference of plastic bag so that the web material can be cut into the shape of circumference of plastic bag by the web cutting means whenever the web material is intermittently fed and temporarily stopped, to successively make plastic bags with a waste kept continuous.

The web cutting means comprises partially cutting means. The plastic bag has an upstream edge along which the web material is cut partially by the partially cutting means so that the plastic bag can be kept connected with the waste at the upstream edge of plastic bag.

The apparatus further comprises drawing means disposed downstream of the cutting means. The waste is diverged from the plastic bag, directed to and drawn by the drawing means after the web material is cut.

The apparatus further comprises discharge means disposed downstream of the cutting means. The plastic bag is directed to the discharge means without the waste. The plastic bag is then pulled by the discharge means to be torn from the waste at the upstream of plastic bag. The plastic bag is then discharged by the discharge means.

In a preferred embodiment, the web cutting means further comprises totally cutting means. The plastic bag has other edges along which the web material is cut totally by the totally cutting means so that the plastic bag can be disconnected from the waste at other edges.

The apparatus further comprises heat seal means disposed upstream of the cutting means. The web material is heat sealed longitudinally and widthwise thereof by the heat seal means whenever the web material is intermittently fed and temporarily stopped so that heat sealed portions can be formed longitudinally and widthwise of the web material. The web material is then cut along the heat sealed portions by the web cutting means.

The web cutting means comprises THOMSON blade means opposed to the web material. The apparatus further comprises drive means by which the THOMSON blade means is moved toward and pressed against the web material whenever the web material is intermittently fed and temporarily stopped.

The partially cutting means has micro depressions formed and spaced from each other along the cutting edges thereof to leave micro joints formed and spaced from each other along the upstream edge of plastic bag. The micro joints make the web material cut partially. The plastic bag is kept connected with the waste by the micro joints.

The drawing means comprises take up means by which the waste is drawn and taken up.

The apparatus further comprises waste guide means disposed between the web cutting means and the discharge means. The waste is engaged with and guided by the waste guide means to be changed in direction, diverged from the plastic bag and directed to the drawing means so that the plastic bag can be directed to the discharge means without the waste.

The apparatus further comprises detector means for detecting the plastic bag to determine whether the plastic bag is inclined or not when the waste is diverged from the plastic bag and the plastic bag is directed to the discharge means.

The apparatus further comprises rejected bag removing means incorporated into the discharge means. The plastic bag is removed by the removing means in response to a detecting signal fed from the detector means when the plastic bag is inclined.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings,FIG. 1illustrates an apparatus for successively making plastic bags2each of which has a shape of circumference, according to the invention. The apparatus includes web feeding means4by which a web material6is intermittently fed for a length along a longitudinal feeding path. In the embodiment, the web feeding means4comprises a pair of feeding rollers between which the web material6is sandwiched. The feeding rollers4are driven for rotation by drive means such as a motor so that the web material6can be intermittently fed for the length along the feeding path which extends horizontally. The web material6comprises two or more layers of plastic film.

The apparatus further includes web cutting means8aand8bdisposed along the feeding path. The web cutting means8aand8bcomprises THOMSON blade means opposed to the web material6. The apparatus further includes drive means10by which the THOMSON blade means8aand8bis moved toward and pressed against the web material6whenever the web material6is intermittently fed and temporarily stopped. The THOMSON blade means8aand8bhas a shape corresponding completely to the shape of circumference of plastic bag2. Accordingly, the web material6can be cut into the shape of circumference of plastic bag2by the THOMSON blade means8aand8bwhenever the web material6is intermittently fed and temporarily stopped, to successively make the plastic bags2with a waste12kept continuous. In the embodiment, the THOMSON blade means8aand8bcomprises a pair of THOMSON blades to successively make plastic bags two by two, as shown inFIG. 2. The waste12is kept continuous around each of the plastic bags2.

The apparatus further includes heat seal means14disposed upstream of the THOMSON blades8aand8b. The heat seal means14comprises heat seal bars which are moved toward and pressed against the web material6by the drive means10to be synchronized with the THOMSON blades8aand8b. The web material6is therefore heat sealed longitudinally and widthwise thereof by the heat seal bars14whenever the web material6is intermittently fed and temporarily stopped so that heat sealed portions16can be formed longitudinally and widthwise of the web material6. The web material6is then cut along the heat sealed portions16by the THOMSON blades8aand8b, to successively make the plastic bags2.

In addition, the THOMSON blades8aand8bcomprise partially and totally cutting means. The plastic bag2has an upstream edge18along which the web material6is cut partially by the partially cutting means8a. The plastic bag2has other edges20and21along which the web material6is cut totally by the totally cutting means8bso that the plastic bag2can be kept connected with the waste12at the upstream edge18of plastic bag2and disconnected from the waste12at other edges20and21. In the embodiment, the partially cutting means8ahas micro depression formed and spaced from each other along the cutting edge thereof to leave micro joints22formed and spaced from each other along the upstream edge18of plastic bag2. The micro joints22make the web material6cut partially. The plastic bag2is kept connected with the waste12by the micro joints22. It should be recognized that the micro joints22are shown in exaggeration for convenience. In reality, each of the micro joints22has a very small size of about 0.2 mm.

The apparatus further includes drawing means24disposed downstream of the THOMSON blades8aand8b. The waste12is diverged from the plastic bag2, directed to and drawn by the drawing means24after the web material6is cut. The drawing means24comprises take up means by which the waste12is drawn and taken up. For example, the drawing means24comprises a take up roller intermittently rotated whenever the web material6is intermittently fed so that the waste12can be drawn and taken up by the take up roller24without slacking. The plastic bag2is kept connected with the waste12at the upstream edge18of plastic bag2, as described above, and therefore intermittently fed integrally with the waste12. The waste12may be directed to and drawn by drawing means other than the take up roller24. For example, the drawing means may comprise pinch rollers between which the waste12is pinched. The pinch rollers are intermittently rotated whenever the web material6is intermittently fed so that the waste12can be drawn by the pinch rollers without slacking.

The apparatus further includes discharge means26,28,30and32disposed downstream of the THOMSON blades8aand8b. The discharge means26,28,30and32comprises upper and lower rollers and upper and lower belts. The plastic bag2is directed to the upper and lower rollers26and28without the waste12. The plastic bag2is then pulled by the upper and lower rollers26and28to be torn from the waste12at the upstream edge18of plastic bag2. The plastic bag2is then discharged by the upper and lower belts30and32, as described below.

The apparatus further includes waste guide means33which comprises a waste guide roller disposed between the THOMSON blades8aand8band the upper and lower rollers26and28. The waste12is engaged with and guided by the waste guide roller33to be changed in direction, diverged from the plastic bag2and directed to the take up roller24so that the plastic bag2can be directed to the upper and lower rollers26and28and the upper and lower belts30and32without the waste12. In the embodiment, the waste12is changed in direction to extend upwardly from the waste guide roller33. The plastic bag2is directed along the feeding path of web material6which extends horizontally. The waste12is therefore diverged from the plastic bag2and directed to the take up roller24so that the plastic bag2can be directed to the upper and lower rollers26and28and upper and lower belts30and32without the waste12.

The plastic bag2is directed to and disposed between the upper and lower rollers26and28. The upper roller26is then moved toward the lower roller28by the drive means10to be synchronous with the THOMSON blades8aand8bso that the plastic bag2can be sandwiched between the upper and lower rollers26and28whenever the web material6is intermittently fed and temporarily stopped. In addition, the lower roller28is driven for rotation by drive means such as a motor when the plastic bag2is sandwiched. The upper roller26is therefore driven for rotation by lower roller28. The lower roller28is rotated counterclockwise inFIG. 1while the upper roller26is rotated clockwise so that the plastic bag2can be pulled by the upper and lower rollers26and28to be torn from the waste12at the upstream edge18of plastic bag2.

The plastic bag2then passes through the upper and lower rollers26and28to be disposed between the upper and lower belts30and32. The upper belt30is engaged with a pulley34which is moved toward the lower belt32by the drive means10when or after the plastic bag2is disposed between the upper and lower belts30and32. The plastic bag2is therefore sandwiched between and discharged by the upper and lower belts30and32.

Accordingly, the apparatus can successively make the plastic bags2with the waste12kept continuous. The waste12can therefore be taken up by the take up roller24, to conveniently treat the waste12.

In addition, the plastic bag2may be bend or curved considerably to be engaged with the lower roller28at the downstream edge21of plastic bag2when the plastic bag2is directed to the upper and lower rollers26and28. The micro joints22may therefore be wrenched and torn by a friction between the plastic bag2and the lower roller28so that the plastic bag2can be inclined considerably. The plastic bag2may be inclined into a position shown by chained line ofFIG. 2to be overlapped with the next bag2. In this case, the inclined bag2must be damaged by the THOMSON blades8bwhen the next bag2is cut.

Under the circumstances, the apparatus further includes detector means36disposed downstream of the waste guide roller33for detecting the plastic bag2to determine whether the plastic bag2is inclined or not when the waste12is diverged from the plastic bag2and the plastic bag2is directed to the upper and lower rollers26and28. In this embodiment, the apparatus is arranged to successively make plastic bags2two by two, as described above. In this connection, the detector means comprises a plurality of detectors36to allot several detectors36to each of the plastic bags2. The detectors36comprise optical sensors which are spaced from each other in a direction perpendicular to the feeding path of web material6to be disposed at positions corresponding to the downstream edge21of plastic bag2. The optical sensors36can therefore detect the plastic bag2to determine whether the plastic bag2is inclined or not when the waste12is diverged from the plastic bag2and the plastic bag2is directed to the upper and lower rollers26and28.

The apparatus further includes rejected bag removing means38incorporated into the upper and lower belts30and32. The plastic bag2is removed by the removing means38in response to a detecting signal fed from the optical sensor36when the plastic bag2is inclined. In the embodiment, a plurality of belts30are used as upper belts while a plurality of belts32are used as lower belts. In addition, the lower belts32are divided into upstream and downstream belts. The removing means38comprises a stop disposed between the upper belts30at a position between the upstream and downstream belts32. The stop38is moved downward by drive means40which is actuated by a control42in response to the detecting signal fed from the optical sensor36when the plastic bag2is inclined. The inclined bag2then strike against the stop38when being discharged by the upper and lower belts30and32, to be dropped and removed between the upstream and downstream belts32.

The waste12may be cut along cut lines44by cutter means after the plastic web6is cut by the THOMSON blades8aand8bso that the waste12can be divided widthwise of the web material6and taken up by the take up roller24.

The web material6may be slit along slit lines46by slit blades before being cut by the THOMSON blades, as shown inFIG. 3. In this case, the web material6needs merely to be cut along the upstream and downstream edges18and21of plastic bag2by the THOMSON blades whenever the web material6is intermittently fed and temporarily stopped. The web material6needs not to be cut along other edges20by reason that the web material6has been slit along the slit lines46or other edges20. The THOMSON blades may therefore have a shape corresponding not completely but incompletely to the shape of circumference of plastic bag2.

In this connection. It should be recognized that the plastic bag2comprises two or more layers of plastic film which are liable to adhere to each other when being cut by the THOMSON blades. On the other hand, the layers of plastic film do not adhere to each other when being slit by the slit blades. The plastic bag2may include open top and closed bottom edges comprising other edges20along which the web material6is slit. It is therefore advantageous in that the open top edge is easy to be open when filling content into the plastic bag after making the plastic bag.