GB2038763A - Method and apparatus for the filling and sealing of sacks - Google Patents

Abstract

The open end of a filled sack is drawn out to a rectangle by insertion of fingers (45 to 48) and movement of the fingers first to a position adjacent the short sides of the opening respectively and then to a position against the junction of the long and short sides of the opening, fold members (43) then being used to form lateral infolds in the short sides of the opening such that by simultaneous inward movement of the fingers, the top edges of the sack are brought together ready for sealing. <IMAGE>

Description

SPECIFICATION Method and apparatus for the filling and sealing of sacks The invention relates to a method of filling and sealing sacks, side folds being formed at the closure end and being gripped by the closure seam during the manufacture of the latter.

Bulk commodities which are packed in large portions are frequently packed in side-fold sacks.

Sacks of this type have an approximately square cross section, thus permitting the formation of stable stacks. Furthermore, a given storage space can be utilised to an optimum extent, since stacks of sacks do not have any appreciable spaces between the individual sacks.

Long tubularfilms, usually wound onto a supply roll, are processed to form individual sacks in the sack-packing machine and are filled with the commodity. Side folds are already formed over the entire length of the tubularfilm. Bottom seams of sacks are formed in the sack-packing machine. At the same time, or shortly thereafter, the tubular film is severed in the vicinity of the bottom seam and the sack, still open at one end, is applied to a filling nozzle through which a metered portion of commodity is introduced into the sack. To prevent the side folds from bulging outwardly in the region of the opening, the side fold is fastened in the region of the opening by welding.

This fastening operation can be effected at the same time as the bottom seam of an adjacent sack is produced, or alternatively, it can be effected in a separate welding station (German Offenlegungsschrift 25 19 253). By fixing the side folds, the cross section of the opening of the sack is reduced to so great an extent that the filling cross section is only approximately a quarter of that of a sack not having fastened side folds. This is particularly disadvantageous in the case of commodities which are not flowable or which are not satisfactorily flowable, since a narrow filling opening causes problems with respect to uniform distribution of the commodity in the sack. The filling time is also prolonged, so that the total station time of the machine is prolonged and thus the output of the machine is reduced.

The object of the invention is to provide a method of the kind described above which permits more rapid filling of the sack over a large cross section. An apparatus for performing the method is also to be provided.

The method in accordance with the invention entails that the side folds are pulled apart during filling of the sack, that the top unfilled end of the sack is spread to form an opening of rectangular cross section after the sack has been filled, and the side folds are formed by pressing in from the outside, the opening at the same time being closed by moving the long rectangular sides of the opening towards one another, and that the closure seam is then produced preferably by sealing or welding.

When using the method in accordance with the invention, a very large cross section of the opening is available for filling the sack, namely, a cross section equal to the overall cross section of the sack.

Filling of the sack is thereby substantially facilitated, particularly when processing material which is nonflowable or which is unsatisfactorilyflowable, since distribution of the material no longer has to be effected from a narrow filling cross section. The filling operation also takes place substantially more rapidly, since the cross section of the filling nozzle may be approximately four times that of the filling nozzle employed in the method which has been used hitherto. The station time of a sack-packing machine is thereby substantially shortened, this being tantamount to a substantial increase in the output of the machine.

An apparatus for performing the method in accordance with the invention is characterised by four finger-like spreaders, two finger-like foldformers, a first operating device for the raising and lowering of spreaders and fold-formers, and a second operating device for moving the spreaders and fold-formers in a horizontal plane.

The opening is spread by the spreaders to form a rectangle, whereupon the fold-formers press against the short rectangular sides of the opening and thereby form the side-folds. The spreaders are at the same time applied to one another in pairs. The movement of the spreaders and of the fold-formers must be exactly matched to one another. This can be attained without large expenditure on control means if the operating devices are mechanically coupled to one another. Spreaders and fold-formers of flat construction are particularly advantageous, since, when they are of this configuration, and despite the great rigidity of the finger-like elements, the walls of the sack can be moved close to one another when the fingers are engaged.

In a preferred embodiment, the sack is moved continuously during the forming of the side folds, and the device for forming the folds participates in this movement. This has the advantage that the sacks are not subjected to forces due to mass.

However, the invention also includes constructions in which the sack is satationary during formation of the side folds.

The spreaders and the fold-formers may be withdrawn by, for example, arranging the entire foldforming device on a vertically movable frame.

Alternatively, however, other embodiments are possible such as embodiments in which the finger-like elements are raisable and lowerable by themselves.

When the entire arrangement is raisable and lowerable, the weight of the apparatus is preferably compensated for by springs. This weight compensation enables the forces for the vertical drive to be kept small.

In an advantageous practical embodiment, the finger-like elements are arranged on longitudnal beams and transverse beams, and the mechanical combination of the movements of these beams results in a low expenditure on control means and, nevertheless, results in accurate co-ordination of the movements of the spreaders and of the fold-formers.

Thus there may be provided two longitudinal beams which extend parallel to the long sides of the rectangle of the opening of the sack and which are displaceable transversely of their longitudinal direc tion, and two transverse beams which are arranged at right angles to the longitudinal beams and which are displaceable in the longitudinal direction of the longitudinal beams, the fold-formers being secured to the transverse beams and the spreaders being secured to the longitudinal beams. Rotary drives may be employed, such as rotary cylinders, arranged on the transverse beams or on the longitudinal beams, from which rotary drives project arms which engage pins on the longitudinal beams such that the longitudinal beams and the transverse beams simultaneously move away from one another and simultaneously move towards one another.

Additional movement of the spreaders can be effected, thus further facilitating the insertion and withdrawal of the spreaders, by having the spreaders made movable, independently of their mechanical coupling to the fold-formers, in a direction parallel to the long sides of the rectangular opening of the sack. Pneumatic cylinders may be provided for effecting the said independent movement. A particularly simple device which automatically releases the spreaders from the sack before they are withdrawn may be provided, in that each of the said pneumatic cylinders has an associated release spring which, when the pneumatic cylinder is pressure-free, moves the spreaders towards one another and thus disengages them from the material of the sack.

A side-fold holder which comprises guide plates which are movable transversely of the direction of movement of the sacks by means of, for example, pneumatic cylinders and which preferably are fixedly arranged otherwise than for being movable only transversely of the direction of movement of the sacks, ensures that, even after the spreaders have been withdrawn, the side fold remains fixed until the welding operation has been effected. The welding operation is effected immediately after the sack has been removed from the fold-forming device.

An embodiment of the invention is illustrated in the drawings, in which: Figure I is a plan view of an entire sack-packing machine, viewed in the direction of arrow I of Figure 2; Figure 2 is a side elevation of the machine, viewed in the direction of the arrow II of Figure 1; Figure 3 is a simplified perspective illustration of the components on which the devices for forming side folds are arranged; Figure 4 is a simplified side elevation of the device for the forming of side folds, shown in a position after the spreaders have been introduced into the opening of the sack; Figure 5 is a plan view, viewed in the direction of the arrow V of Figure 4; Figure 6 is a plan view, corresponding to Figure 5, in an operating phase in which the opening of the sack has been spread and the forming of the side folds commences;; Figure 7is a plan view, corresponding to Figures 5 and 6, in a working phase in which the formation of the side folds has been completed; Figure 8 is a fragmentary plan view of the device for forming side folds, the drive devices being shown, and Figures 9 to 12 are diagrammatic illustrations of various operating phases of the apparatus.

The sack-packing machine illustrated in Figures 1 and 2 comprises the following main parts:- a sack-forming and a sack filling machine 1, a conveyor belt 2, a device 3 for the formation of side folds, and a welding machine 4 for producing the top closure seam. A tubular film incorporating side folds is drawn from a supply roll 5 in the machine 1 in which is formed a bottom seam by means of which the side folds are fixed at the bottom end of the sack.

The sack is severed from the tubular film below the bottom seam and is guided to a position below a sack-filling nozzle 6 where it is filled with the product which is to be introduced and which is metered from the storage container 7. The filled sack which is still open at the top is placed onto the continuously running conveyor belt 2 which conveys the sack into the apparatus 3 where side folds are formed in the sack. After the side folds have been formed, the sack enters the welding machine 4 in which the top closure seam is produced, the formed side folds being fixed. The invention particularly relates to the apparatus 3 whose construction and function will be described hereinafter with reference to Figures 3 to 12..

The apparatus 3 (see particularly Figure 3) has a stand 8 from which a frame, generally designated 9, is supported so as to be raisable and lowerable. The frame 9 is supported by four gas springs 10 which support at least a portion of the weight of the frame 9 together with the elements located thereon. An operating device generally designated 11 is provided for raising and lowering the frame 9. The operating device has an electric motor 12 which drives a shaft 14 byway of a transmission unit 13, and the shaft 14 in turn drives shafts 17 and 18 by way of transmission units 15 and 16. A brake 19 is arranged between the motor 12 and the transmission unit 13. Sprocket wheels 20 are mounted on the shafts 17 and 18, and chains 21 are fitted round the sprocket wheels 20.

The chains 21 are connected to the frame 9 at clamping locations 22. Two further shafts 23 provided with sprocket wheels 24 are located on the stand 8, and the endless chains 21 are also fitted to the sprocket wheels 24.

The driving connection of all four clamping locations 22, and the drive effected by means of a single drive motor 12, ensure that there is no risk of tilting of the frame 9.

A carriage generally designated 25 is movable on the frame 9 (see Figures 4 and 5). The carriage 25 (see also Figure 8) is slidable on two parallel guide bars 26 and 27. For this purpose, ball boxes 28 are arranged on the carriage 25 and embrace the guide bars 26 and 27. The carriage 25 is moved along the frame 9 by means of an electric motor 29 which drives a spindle 31 by way of an intermediate gear unit 30. The spindle engages a spindle nut 32 located on the carriage 25.

The ends of the carriage 25 are provided with guide rails 33,34 (see Figure 4) in which two longitudinal beams 35 and 36 are displaceable.

Transverse beams 37 and 38 are disposed above the longitudinal beams 35,36 and their ends are likewise guided in guide rails. The longitudinal beams 35,36 and the transverse beams 37,38 are interconnected with respect to their drives. They are diven by a total of four rotary cylinders 39 which are rigidly mounted on the transverse beams 37,38. An arm 40 projects from each rotary cylinder 39 and its end is attached to a bolt 41 which is rigidly connected to the adjacent longitudinal beam. Slotted holes 42 for engagement of the bolts 41 are located in the arms 40 (see Figure 8), so that a certain amount of displacement is possible for purposes of adjustment.The fact that the longitudinal beams 35,36 and the transverse beams 37,38 are interconnected with respect to their drive results in accurately co-ordinated movements of these two pairs of beams, which will be described further below.

Fold- formers 43,44 are secured to the transverse beams 37 and 38. The fold formers can be adjusted in order to adapt them to different sack formats.

Spreaders 45 to 48 are arranged on the longitudinal beams 35,36. These spreaders are displaceable along the longitudinal beams 35,36. For this purpose, pneumatic cylinders 49 are arranged at the ends of the longitudinal beams 35,36 (see Figure 8).

The pneumatic cylinders are double-acting cylinders whose cylinders 49a are secured to a longitudinal beam and whose piston rods 49b act upon a support member 50 for the associated spreader. The support member 50 is mounted on the associated longitudinal beam so as to be longitudinally displaceable.

Each cylinder 49 has an associated compression spring 51 which seeks to urge the piston rod 59b out of the cylinder. Thus, when the cylinder is pressurefree the spring causes the spreaders to move such that the latter move a short distance in the longitudinal direction of the longitudinal beam 35,36, such that the spreaders move towards one another in this direction.

The spreaders are arranged laterally on the longitudinal beams 35,36 such that they can be moved very close to one another. This is necessary in order to be able fully to form side folds, as will be explained further below.

Fold holders 52, 52a and 53, 53a are also arranged on the stand 8. Each fold holder has an associated double-acting pneumatic cylinder whose cylinder 55a is arranged on the stand 8 and whose piston rod 55b is arranged on a side fold holder. The travel of the side fold holders is dimensioned such that they can be moved towards one another up to a short distance apart.

Before explaining the mode of operation of the apparatus, the diagrams of Figures 9 to 12 will be considered, which show various phases in the formation of the side folds.

Figure 9 shows the approximate state of the top end of the sack after the sack has been filled. The opening 56 of the sack is indicated by a dash-dot line. The top of the sack is also referred to as "sack bloom". The side folds 57 and 58 are largely bulged out. The walls of the sack are not stretched in the non-filled region. The sack is conveyed in this state by the conveyor belt 2 to a position below the side fold forming device 3. The spreaders 45 to 48 and the fold formers 43 and 44 are located in positions such that the sack is not engaged when these elements are lowered.

The pairs 45/46 and 47/48 of spreaders are then moved apart, namely into the extreme end position corresponding to the format of the sack. The spreaders are then brought into the position shown in Figure 11, that is to say, the spreaders of each pair are moved apart, the opening of the sack being stretched to form a rectangle. The fold-formers 43,44 are at the same time moved towards the short sides 59,60 of the rectangle. When the side-fold formers engage the walls 59,60, the spreaders 45,46 and 47,48 move towards one another simultaneously with the forward movement of the fold-formers until the state shown in Figure 12 is finally attained. The side fold is thus formed.

The manner in which the different working phases described above is performed by means of the apparatus will be described hereinafter.

When the filled sack arrives in the region of the apparatus 3, the carriage 25 is in its end position located nearest to the unit 1. This extreme position is illustrated in Figure 2. When the sack has arrived below the spreaders, the drive for the carriage 25 is put into operation, so that the carriage is moved in synchronism with the belt 2. The entire frame 9 is lowered at the same time, and the spreaders 45 to 48 enter the opening of the sack, and the fold-formers 43,44 are brought into a position laterally of the side folds 57,58 which have not yet been formed. The elements of the carriage thereby assume a position corresponding approximately to the position shown in Figures 4 and 5, with the exception that the spreaders have been moved apart slightly.

The pneumatic cylinders 49 are then actuated and pull the spreaders outwardly until they have reached the position corresponding to Figure 10. The springs 51 are thereby tensioned. All four rotary cylinders 39 are then simultaneously put into motion by simultaneously feeding them with pressure medium. The rotary cylinders then move simultaneously, so that the position shown in Figure 6 is reached. The spreaders 45 and 46 and the spreaders 47 and 48 are thereby moved apart simultaneously and the foldformers 43 and 44 are moved towards one another.

This results from the fact that the spreaders are secured to the longitudinal beams 35,36, and the fold-formers are secured to the transverse beams 37,38 and the longitudinal beams have been moved outwardly and the transverse beams have been moved inwardly.

The movement is continued until the position shown in Figure 7 is finally reached. It may be mentioned that the entire movement of the rotary cylinders is effected in a single operation and not in a stepwise manner. The position shown in Figure 7 corresponds to the position shown in Figure 12.

When in this position, the spreaders 45,46 and 47,48 have been moved towards one another to the greatest possible extent The springs 51 can come into action when the cylinders 49 are relieved of pressure medium. The springs 51 move the pairs 45/46 and 47/48 of spreaders towards one another to a slight extent, whereby the pairs of spreaders are disengaged from the edges of the sack and can be readily withdrawn. However, before the withdrawal, the side-fold holders 52, 52a and 53, 53a are moved to the top end of the sack by admitting pressure medium into the cylinders 55. The shape of the folds is thereby maintained.

The carriage 25 has in the meantime reached that end of the frame 9 which is adjacent to the welding machine 4. Thus, the sack is introduced into the welding machine 5 immediately after the side folds have been formed.

The welding machine 4 has continuously running belts 4a and 4b which grip the top end of the sack and form a closure seam on the sack.

Claims (20)

1. Method of filling and sealing sacks, side folds being formed at the closure end, which are gripped by the closure seam during manufacture of the latter, wherein the side folds are pulled apart during the filling of the sack, the top unfilled end of the sack is stretched to form an opening having a rectangular cross section after the sack has been filled, and the side folds are formed by pressing-in from the outside; the opening at the same time being closed by moving the long sides of the rectangle towards one another, and the closure seam is subsequently formed.

2. Method as claimed in claim 1, wherein the closure seam is formed by sealing or welding.

3. Apparatus for performing the method as claimed in claim 1 or 2, comprising four finger-like spreaders, two finger-like fold formers, a first operating device for raising and lowering the spreaders and fold-formers, and a second operating device for moving the spreaders and fold formers in a horizontal plane.

4. Apparatus as claimed in claim 3, wherein the operating devices for horizontal movement of the spreaders and of the fold-formers are mechanically coupled to one another.

5. Apparatus as claimed in claim 3 or 4, wherein the spreaders and the fold-formers are in the form of flat swords whose flat sides are aligned parallel to the large side walls of the sack.

6. Apparatus as claimed in any of the claims 3 to 5, wherein there is provided a continuously movable conveyor and a carriage which is arranged above the conveyor and which is movable horizontally and parallel to the conveyor in synchronism therewith, and in which are located spreaders and fold-formers together with their operating devices.

7. Apparatus as claimed in claim 6, wherein the carriage is guided in a support frame arranged above the conveyor so as to be raisable and lowerable.

8. Apparatus as claimed in claim 7, wherein the support frame is supported by means of springs which entirely or partially carry the weight of the support frame and of the parts mounted on the support frames.

9. Apparatus as claimed in any of the claims 3 to 8, wherein there are provided two longitudinal beams which extend parallel to the long sides of the rectangle of the opening of the sack and which are displaceable transversely of their longitudinal direction, and two transverse beams which are arranged at right angles to the longitudinal beams and which are displaceable in the longitudinal direction of the longitudinal beams, the fold-formers being secured to the transverse beams and the spreaders being secured to the longitudinal beams.

10. Apparatus as claimed in claim 9, wherein rotary drives are arranged on the transverse beams or on the longitudinal beams, from which rotary drives project arms which engage pins on the longitudinal beams such that the longitudinal beams and the transverse beams simultaneously move away from one another and simultaneously move towards one another.

11. Apparatus as claimed in claim 4 and any of the claims 5 to 10, wherein the spreaders are movable, independently of their mechanical coupling to the fold-formers, parallel to the long sides of the rectangular opening of the sack.

12. Apparatus as claimed in claim 11,wherein pneumatic cylinders are provided for the said independent movement.

13. Apparatus as claimed in claim 12, wherein each of the said pneumatic cylinders has an associated release spring which, when the pneumatic cylinder is pressure-free, moves the spreaders towards one another and thus disengages them from the material of the sack.

14. Apparatus as claimed in any of the claims 3 to 13, wherein at least one side fold holder comprising guide plates which are movable transversely of the direction of movement of the sacks by means of, for example, cylinders.

15. Apparatus as claimed in claim 14, wherein the fold holders are fixedly arranged and are movable only transversely of the direction of movement of the sacks.

16. Apparatus as claimed in claim 6 or any of preceding claims 7 to 15, as dependent on claim 6, wherein said conveyor is a belt conveyor.

17. Apparatus as claimed in claim 8, or any of preceding claims 9 to 16, as dependent thereon, wherein said springs are gas springs.

18. Apparatus as claimed in claim 10 or any preceding claim 11 to 17 as dependent thereon, wherein said rotary drives are rotary cylinders.

19. A method of filling and sealing sacks, substantially as hereinbefore described with reference to the accompanying drawings.

20. Apparatus for filling and sealing a sack, substantially as hereinbefore described with reference to the accompanying drawings.