GB2269560A - A paper bag production process. - Google Patents

Abstract

A feeding station (2) feeds a paper web (3) from a roll (4) on a spindle (31) having a fixed end stop (32) and a movable clamp (36). Rotation of the paper roll is controlled by action of an adjustable brake assembly (38). A longitudinal strip of adhesive is applied by action of an adhesive wheel partly immersed in an adhesive reservoir. Folding over of the web is carried out by guide wheels (11 and 12) Fig 2 (not shown) mounted around an elongate former (10) to deliver the web in the form of a lower leaf (20) Fig 3 (not shown) and an upper leaf (21) Fig 3 (not shown) which are cut off-set to each other by action of an impact arm (24) against lower and upper cutting blades (22 and 23). The process lends itself to easy and simple batch changes and to a very low discard rate for small batches. <IMAGE>

Description

"A paper bag production process" The invention relates to a paper bag production process.

British Patent Specification No. GB 1,401,977 and GB 1,442,308 (BEASLEY FRENCH) describes web cutting apparatus which apparently could be applied to the manufacture of paper bags.

In these apparatus, a rotatable shaft carrying a perforating cutting element is used for periodic perforating of cutting contact with the moving web. Such apparatus is apparently quite suitable for perforating a web in any circumstances such as in high volume batch production. However, for relatively small volumes where there are frequent changeovers between different batches and many different thicknesses and widths of web for paper bag production, these perforating methods have been found not to be particularly suitable.

The invention is directed towards providing a process for paper bag production which is efficient, even in circumstances where there are frequent batch changes.

According to the invention there is provided a paper bag manufacturing process comprising the steps of: loading a paper roll onto a spindle having a fixed end stop, the position of which may be pre-set to a discreet number of fixed positions; urging a conical-shaped clamp against the roll to press it against the fixed end stop; applying a longitudinal strip of adhesive to the web by action of an adhesive application wheel partly immersed in an adhesive reservoir and pinching against the web; passing a web underneath an elongate former which is no more than half the width of the web and folding over the sides of the web by action of rollers so that the sides of the web overlap above the elongate former and adhere together because of the longitudinal adhesive strip; passing the lower web leaf below a lower cutting blade, and passing the upper web leaf below an upper cutting blade, the blades being mounted one above the other and mutually off-set in longitudinal position, and subsequently cutting the lower leaf against the lower cutting blade and cutting the upper leaf against the upper cutting blade by action of an impact arm rotating about an axis in the direction of travel of the web; and applying glue and sealing an end of an off-cut portion of the web to form a paper bag.

In one embodiment, the movable clamp for holding a paper roll on the spindle is conically shaped having an axis coincident with the axis of the spindle and having longitudinal serrations for gripping the core of the paper roll.

Preferably, rotation of the roll on the spindle is controlled by action of brake pads pinching against a brake wheel fixed on the spindle, pressure of the brake pads being adjustable by use of a spring-biased bolt.

The invention will be more clearly understood from the following description of some preferred embodiments thereof given by way of example only with reference to the accompanying drawings in which: Fig. 1 is a schematic diagram showing a paper bag production process of the invention; Fig. 2 is a perspective view of a web folding operation of the process; Fig. 3 is a diagrammatic cross-sectional view showing a web cutting operation of the process; Fig. 4 is a perspective view showing a web feed station of the process; Fig. 5 is a diagrammatical cross-sectional view showing the web feeding operation; Fig. 6 is a perspective view showing the web feeding operation and the web gluing operation; Fig. 7 is a side view showing the web feeding station; and Fig. 8 is a perspective view showing the web cutting station in more detail.

Referring to the drawings, and initially to Fig. 1, there is illustrated a paper bag production process of the invention, indicated generally by the reference numeral 1. In general outline, the process is carried out by an apparatus having a web feeding station 2 which supplies paper web 3 from a roll 4. An adhesive station 5 applies adhesive to the web, which is then folded at a folding station 6. A cutting station 7 then operates on the folded web before it is passed to a final sealing station 8 to produce a finished paper bag 9, a set of which is shown.

The various operations of the process are now described in more detail with reference to Figs. 2 to 8 inclusive. In Fig.

2, the folding station 6 is shown. This comprises an elongate former 10 around which the web 3 is folded. This operation is carried out by a preliminary guide wheels 11, final guide wheels 12 and a former 13 mounted above the elongate former 10. It will be appreciated that in a batch change for bag production using a wider web, the station 6 may be readily easily adjusted by insertion of a replacement elongate former 11 and by separating the guide wheels 11 and 12 further apart in grooves, (not shown) in the bed of the machine.

The web 3 which is delivered from the folding station 6 comprises a lower leaf 20 and an upper leaf 21. The upper leaf 21 is formed by the sides of the web being folded over on each other with an overlap of 10 - 12 mm at which they are sealed using glue applied at the adhesive station 5 (which is described in more detail below). The cutting station 7 comprises a lower cutting blade 22 below which the lower leaf 20 runs and an upper cutting blade 23 below which the upper leaf 21 runs. Both of the blades 22 and 23 have saw-tooth edges which are more clearly shown in Fig. 8. For clarity, in Fig. 8 the web 3 is not shown so that the blades may be more clearly shown. An impact arm 24 is driven to rotate about a longitudinal axis so that the arm 24 moves in the direction indicated by the arrow A of Fig. 3. This arm is not shown in Fig. 8.The impact arm 24 impacts against the lower leaf 20 just beyond the end of the lower cutting blade 23 to cause the leaf to be cut and subsequently in the same action it impacts against the upper leaf 21 just beyond the end of the upper leaf blade 23. The blades 22 and 23 are off-set in longitudinal direction so that cutting of the upper and lower leaves is off-set. For the top of a paper bag, this allows the bag to be more easily opened by the user, whereas at the bottom end of the bag it allows the bag to be sealed by overlap of the lower leaf. It has been found that there is a very low reject rate of about 0.001% at the cutting station if the distance between the impact arm 24 and the lower cutting blade 22 is 3 - 4 mm. Further, it has been found that for a web density of 45 gm/in2 an impact arm rotation speed of 150 rpm is particularly suitable. A lower roller 25 and an upper segmented roller 26 feed the off-cut web to the final sealing station 8 where the bottom of the bag is sealed by folding over of the lower leaf 20 and application of glue in the transverse direction.

Referring now to Figs. 4,5,6 and 7, the web feeding station 2 is shown in more detail. The feed station 2 comprises a spindle 31 on which is mounted an adjustable fixed end stop 32 which may be fixed in position on the spindle 31 using an adjustable screw 33 and notches 34 on the spindle 31. The stop 32 has conical shape for engagement with the central core of a paper roll 42. The feeding station 2 also comprises a movable clamp 35 which is also of conical shape and has longitudinal serration 36. The clamp 35 is rotatable on threads 37 on the spindle 31. Finally, the feeding station 2 comprises a brake assembly 38 having a pair of opposed brake pads 39 for engagement with a brake wheel 40 using an adjustable fastening mechanism 41. The fastening mechanism 41 comprises a bolt 42 surrounded by a coil spring 43 which engages the ends of supports for the brake pads 39.

It has been found that for frequent batch changes where production runs are relatively small, the feeding station 2 is particularly suitable for quick batch changes. The batch changing operation involves simply lifting the spindle 31 out of its seat at the end adjacent to the fixed stop 32, removing the fixed stop 32 and subsequently removing the roll 4 and inserting the new roll and achieving the desired tension by fine adjustment of the clamps 35 after the fixed stop 32 has been fixed in position. The brake pressure applied by the brake assembly 38 may be easily controlled by rotation of the bolt 42 to adjust the pressure on the brake pads 39. This pressure may be readily easily monitored using, for example, a torque wrench. It has been found that the feeding station 2 is relatively simple, robust and lends itself to easy change overs for frequent batch changes.

Referring in particular to Fig. 6, the adhesive station 5 is shown in more detail. This comprises a wheel 50 partly immersed in a glue reservoir 51 and abutting against the web 3 on a roller 52. Thus, application of adhesive to the web 3 involves simply passing the web 3 over an additional roller which engages the wheel 50 and applies the glue. This is found to be a simple and reliable method of adhesive application.

It has been found that the combination of web feeding operation, the adhesive operation, the folding operation and the cutting operation as described above is particularly suitable for production of paper bags where there are frequent batch changes and where batch runs may involve in the range of 10,000 to 40,000 bags. It has been found that the discard rate of bags is 0.8 - 13.6%.

The invention is not limited to the embodiments hereinbefore described, but may be varied in construction and detail.

Claims (4)

1. A paper bag manufacturing process comprising the steps of: loading a paper roll onto a spindle having a fixed end stop, the position of which may be pre-set to a discreet number of fixed positions; urging a conical-shaped clamp against the roll to press it against the fixed end stop; applying a longitudinal strip of adhesive to the web by action of an adhesive application wheel partly immersed in an adhesive reservoir and pinching against the web; passing a web underneath an elongate former which is no more than half the width of the web and folding over the sides of the web by action of rollers so that the sides of the web overlap above the elongate former and adhere together because of the longitudinal adhesive strip;; passing the lower web leaf below a lower cutting blade, and passing the upper web leaf below an upper cutting blade, the blades being mounted one above the other and mutually off-set in longitudinal position, and subsequently cutting the lower leaf against the lower cutting blade and cutting the upper leaf against the upper cutting blade by action of an impact arm rotating about an axis in the direction of travel of the web; and applying glue and sealing an end of an off-cut portion of the web to form a paper bag.

2. A process as claimed in claim 1, wherein the movable clamp for holding a paper roll on the spindle is conically shaped having an axis coincident with the axis of the spindle and having longitudinal serrations for gripping the core of the paper roll.

3. A process as claimed in claim 1 or claim 2, wherein rotation of the roll on the spindle is controlled by action of brake pads pinching against a brake wheel fixed on the spindle, pressure of the brake pads being adjustable by use of a spring-biased bolt.

4. Paper bags whenever produced by a process as claimed in any preceding claim.