Apparatus for sealing bag bottom

An apparatus for sealing the bottom of a bag includes a frame through which a bag to be folded is longitudinally advanced. The apparatus includes a pair of cooperating grippers carried by a reciprocably movable gripper carrier. The grippers are operated to opposite edges of the bag, and laterally tension the bag. The apparatus includes a vertically reciprocable fold plate which then is moved downwardly to engage and downwardly fold a leading end portion of the bag. Adhesive is applied thereto, and the bag advanced, by movement of the gripper carrier, for advancement of the folded bag to at least one pair of intermittently-driven nip rollers. The grippers are released, and the nip rollers thereafter operated to compress and complete sealing of the bag bottom.

TECHNICAL FIELD

The present invention relates generally to an apparatus for forming a bag from web-like material, and more particularly to an apparatus for sealing the bottom of a bag by folding and adhesively sealing the bag bottom.

BACKGROUND OF THE INVENTION

Manufacture of bags from flexible materials such as paper or plastic ordinarily entails formation of a generally elongated tubular web, which is advanced through suitable bag-forming equipment to form individual ones of the bags. Such bags can be formed with inwardly extending side gussets, as well as additional specific features, depending upon the intended application.

Various techniques are known for closing and sealing the bottom of the bag as it is formed. The present invention is directed to an apparatus, and associated method, wherein a bottom end portion of a tubular bag is folded, and sealed, thus forming the desired sealed bag bottom.

SUMMARY OF THE INVENTION

An apparatus for sealing the bottom of a bag embodying the principles of the present invention includes a frame through which the bag is advanced in a longitudinal direction. The apparatus includes a pair of edge grippers mounted on a gripper carrier movably mounted on the apparatus frame. The grippers are engageable with respective opposite edges of the bag, and are movable away from each other for laterally pulling on the edges of the bag. In the illustrated embodiment, relative movement of the grippers is provided by movably mounting one of the grippers on the gripper carrier, preferably by pivotally mounting that one of the grippers on the carrier.

The apparatus further includes a folding member in the form of a vertically movable folding plate which is mounted for reciprocable vertical movement on the apparatus frame. After the edges of the bag are gripped, the folding plate engages the bag and folds an end portion of the bag, thereby defining a fold line. In the illustrated embodiment, downward movement of the folding plate of the apparatus effects bag-folding in this fashion.

The apparatus includes an adhesive applicator mounted on the frame for applying adhesive to the folded end portion of the bag. In the illustrated embodiment, the adhesive applicator is mounted for movement transversely of the frame, with the apparatus including an applicator drive for transversely moving the applicator, thus effecting application of adhesive across the width of the bag. As will be appreciated, it is within the purview of the present invention that one or more stationary adhesive applicators can alternatively be employed for adhesive application.

In order to further fold and seal the folded end portion of the bag, the present apparatus includes at least one pair of cooperating nip members, preferably provided in the form of nip rollers, for receiving the fold line of the bag. A carrier drive of the apparatus advances the gripper carrier and pair of edge grippers longitudinally of the frame to advance the fold line of the bag between the pair of cooperating nip rollers. The pair of grippers are released, and the intermittently operable nip rollers activated, thereby drawing and advancing the now completely folded bag end and bag through the nip rollers.

To further facilitate complete folding in this fashion, it is presently preferred that the folded end of the bag engage an upper edge of the folding plate, which remains in a lowered position as the bag is advanced across the top thereof, as the fold line of the bag is advanced into the cooperating nip rollers. This acts to further fold the folded end of the bag as the fold line, and folded bag end, are advanced into the nip rollers.

Thus, a method of folding a bag in accordance with the present invention comprises the steps of gripping opposite edge portions of the bag, and laterally pulling on the opposite edge portions. The method further comprises folding an end portion of the bag, and applying adhesive to the folded end portion of the bag. Finally, the folded end portion is further folded to seal the bottom of the bag, with the method preferably entailing releasing the grip on the opposite edges of the bag prior to the further folding step.

Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings, and the appended claims.

DETAILED DESCRIPTION

With reference to the drawings, therein is illustrated a bag sealing apparatus10embodying the principles of the present invention. Sealing apparatus10is intended for operative association with a suitable bag-making machine, which typically is configured to form a web of suitable bag-making material into a generally elongated tubular configuration. The tubular bag may be provided with inwardly extending side gussets, as are known in the art. The present sealing apparatus successively receives bags to be provided with a folded bottom seal one-at-a-time from the associated bag-making apparatus, with the bags cut to length, and ready for formation of a bottom seal by sealing apparatus10.

Sealing apparatus10includes a frame12upon which the various gripper, folding, adhesive-applying, and web drawing mechanisms of the present invention are positioned. Generally speaking, the present apparatus is operated by advancing the unsealed tube-like bag longitudinally through the apparatus (generally in a right-to-left direction, referring to the orientation ofFIG. 1), with the apparatus operating to grip opposite edges of the bag, and laterally pull on the opposite edges. Thereafter, the apparatus effects folding of an end portion of the bag, and application of adhesive to the folded end portion. The folded end portion of the bag is advanced into at least one pair of cooperating nip rollers, and the edge portions of the bag released. The nip rollers are then cycled to seal the folded end portion of the bag, and advance the now-sealed bag through the apparatus.

The mechanism for gripping and laterally pulling or stretching the edge portions of the bag will now be described. Apparatus10includes a pair of grippers14,16which are positioned for engaging and gripping respective opposite edge portions of a bag, designated B inFIG. 5. Grippers14,16are mounted on a transversely extending gripper carrier18, with the gripper carrier18mounted for movement longitudinally of apparatus10by a pair of slide supports20. It will be observed that for clarity, gripper carrier18has not been illustrated inFIG. 1or2.

Reciprocable, longitudinal movement of the gripper carrier18, and thus grippers14,16, is effected by a pneumatic cylinder22, which is operatively connected with a drive belt24. Drive belt24is trained about a pair of pulleys, with the pneumatic cylinder22operatively connected with the drive belt via a drive block26.

A drive shaft28extends transversely of apparatus10, and thus connects one of the pulleys upon which drive belt24is mounted with a similar pulley on the opposite side of apparatus10, which in turn acts to concurrently drive a drive belt30.

Opposite ends of longitudinally reciprocable gripper carrier18are operatively connected with upper runs of the drive belts24,30. Thus, the action of gripper cylinder22acts to reciprocably, longitudinally move the gripper carrier18, and the grippers14and16mounted thereon.

As noted, each of grippers14,16is mounted on gripper carrier18for movement therewith longitudinally of apparatus10. In particular, each of the grippers14,16is mounted on gripper carrier18by a respective gripper mount32, with the gripper mounts permitting adjustable lateral positioning of the grippers14,16for accommodating bags of different widths.

Each of the grippers14,16includes a gripper frame34which carries a respective gripper cylinder36, and a vertically movable gripper foot38, which cooperates with a cooperating gripping surface which projects inwardly from beneath the respective gripper frame.

In order to effect the desired movement of the grippers away from each other during sealing of the bottom of bag B, one of the grippers is mounted for movement, preferably pivotal movement, on the gripper carrier18. In particular, the frame34of gripper14is pivotal about a pivot42by operation of a pivot cylinder44having one end connected to the frame34, and the other end connected to a plate46which supports pivot42. Plate46, in turn, is rigidly mounted to gripper mount32on gripper carrier18. Thus, operation of pivot cylinder44to retract the cylinder acts to move the gripper foot38of the gripper14outwardly and away from the gripper foot38of gripper16, thus acting to laterally pull on the edges of the bag B.

The mechanism for downwardly folding the leading edge portion of bag B will now be described. Folding of the end portion of the bag is effected by a vertically movable fold plate50mounted for reciprocable vertical movement by suitable plate guides52at opposite ends thereof. The fold plate50defines a lower edge for engaging the bag and folding the end portion thereof, and further defines an upper edge which engages the folded end portion of the bag, when the fold plate is in its lowered position, and as the gripper carrier18is longitudinally advanced to advance the folded bag through the sealing apparatus10. This engagement of the folded end with the upper edge of the fold plate desirably acts to further fold the end of the bag generally through a further 98° of movement.

The folding plate50further defines an expansive surface, between the upper and lower edges thereof, which desirably cooperates with the adhesive applicator, as will be described, during adhesive application. After the fold plate has moved downwardly from its upper position to its lower position, downwardly folding the leading edge portion of the bag generally 90°, the fold plate remains in its lowered position, thus acting as a backing member to support the downwardly folded edge portion as adhesive is applied thereto. Thus, the folded end portion of the bag is positioned between the expansive surface of the fold plate, and the associated adhesive applicator, during application of adhesive to the folded end portion.

Reciprocable vertical movement of the fold plate50is effected by a plate cylinder54which acts through a cross member56, which in turn is connected to, in vertically spaced relationship, to fold plate50by a pair of vertical connectors58. Thus, by operation of plate cylinder54, fold plate50reciprocates vertically with respect to the frame of the sealing apparatus. By virtue of the spacing provided between cross-member56and fold plate50, a bag to be folded can be moved through the opening defined between the fold plate and the cross-member, and the cylinder54thereafter operated to move fold plate downwardly for folding the end portion of the bag which has been advanced into the sealing apparatus.

As noted, fold plate50remains in its lowered position, after the end portion of bag B has been folded, and adhesive applied thereto, so that further advancement of the bag B causes its folded end portion to engage an upper edge of fold plate52, thus further folding the end portion as the fold line of the bag is advanced to cooperating nip rollers of the apparatus, as will be further described.

After the end portion of bag B has been folded downwardly as fold plate50is lowered, adhesive is applied for sealing the end portion, preferably by application of adhesive to the folded end portion. To this end, the apparatus10includes an adhesive applicator60. Applicator60is mounted on frame12for movement transversely thereof, with transverse movement of the applicator effected by driven movement of adhesive drive belt62by adhesive drive motor64. By this arrangement, adhesive can be applied to the downwardly folded end portion of the bag B across the width of the bag as the adhesive applicator60is moved transversely across the frame by operation of drive motor64and drive belt62. As noted, during adhesive application, it is preferred that fold plate50remains in its lower position, the expansive surface of the fold plate thus acting as a backing member for the folded end portion of the bag as adhesive is applied thereto. Thus, the folded end portion of the bag is positioned between the expansive surface of the fold plate50and the adhesive applicator60during adhesive application.

During adhesive application, it is preferred that edges of the bag be retained by grippers14,16, with the grippers pulling laterally on the bag to maintain it in a taut condition during folding and adhesive application. After adhesive application, gripper cylinder22is operated for advancing gripper carrier18, and grippers14and16, longitudinally of the frame12for advancing the bag B over the lowered fold plate50, and into the cooperating nip rollers of the apparatus, as will now be described.

In order to complete sealing of the bottom of the bag by compression of the folded end portion, movement of gripper carrier18acts to advance the bag, in particular, a fold line defined by the folded end portion, into at least one pair of cooperating nip members, which in the illustrated embodiment, comprise upstream and downstream pairs of nip rollers. The nip rollers are intermittently driven, in unison, with the upstream pair of nip rollers being openable to facilitate advancement of the folded bag end therebetween. Thereafter, the upstream nip rollers are closed, and the grippers14,16released. Operation of the nip rollers thereafter acts to advance the bag through the sealing apparatus10, with the compression applied to the bag by the nip rollers acting to complete formation of the sealed bottom for the bag.

The upstream nip rollers include an upper nip roll66and a lower nip roll68, with the lower nip roll68being vertically movable toward and away from the upper nip roll, thereby permitting the nip defined by the rolls to be selectively opened. A pair of nip cylinders70operate through respective swing arms72which support the lower nip roll68. By operation of nip cylinders70, the nip between the upper and lower rolls64,66can be opened to facilitate advancement of the folded end of bag B therebetween, with the nip cylinders70thereafter operated to close the nip.

A downstream pair of upper and lower nip rolls74,76receive the folded bag from the upstream pair of nip rolls, acting to further compress and seal the bag bottom. Pressure between the nip rolls is provided by a pair of nip cylinders78, which respectively act through a pair of swing arms80to urge lower nip rolls76against upper nip roll74.

The upstream and downstream pairs of nip rolls are intermittently driven in unison via a nip drive belt82, which is operated by a nip drive motor84. In the illustrated embodiment, the upper nip rolls66,74are driven by the drive belt82, with the bag web advancing through the nip rolls acting to effect concurrent, counter-rotation of the respective lower nip rolls.

From the foregoing description, operation of the present apparatus will be readily appreciated. A bag to be folded and sealed is advanced into the apparatus so that it extends between grippers14,16, and generally beneath fold plate50, which is initially positioned in its raised position. Grippers14and16are operated to engage and grip the opposite edges of the bag, and pivot cylinder44operated to pivot gripper14so that it moves away from gripper16, thus laterally pulling on the edges of the bag.

Fold plate50is lowered, thereby downwardly folding the edge portion of the bag as it is held by the grippers14,16. Adhesive applicator60is operated so as to apply adhesive to the downwardly-folded end portion of the bag, the expansive surface of fold plate50acting as a backing member during adhesive application.

With the fold plate50maintained in its lowered position, gripper carrier18is advanced by operation of gripper cylinder22, which acts through drive belts24and30, and drive shaft28, to advance the gripper carrier, with grippers14,16mounted thereon. During advancement, the folded end portion of the bag engages the upper edge of fold plate50, thus further folding the end portion.

Continued advancement of gripper carrier18moves the fold line of the bag into the open nip defined by the upstream pair of nip rollers66,68, with lower nip roller68in a lowered or open position to facilitate advancement in this fashion. Nip cylinders70are thereafter operated to move lower nip roll68upwardly and close the nip, capturing the folded end of bag B between the upper and lower nip rollers66,68.

Grippers14,16are now operated to release the edge portions of the bag, which permits gripper carrier18to be retracted, by operation of gripper cylinder22, back to its initial position. The bag is now held by the closed nip of upstream rollers66,68, with operation of nip drive84, acting through belt82to drive the upstream and downstream pair of nip rollers to effect compression and sealing of the folded end portion of the bag. The nip drive84is operated so as to advance the folded and sealed bag out of the apparatus.

From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It is to be understood that no limitation with respect to the specific embodiment illustrated herein is intended or should be inferred. The disclosure is intended to cover, by the appended claims, all such modifications as fall within the scope of the claims.