EP1305212A1

EP1305212A1 - An apparatus and a method for filling and sealing bags and sacks

Info

Publication number: EP1305212A1
Application number: EP01941330A
Authority: EP
Inventors: Tor Kokkersvold; Peter Hartas; Leif Brenden; Freddy Thorbjornsen
Original assignee: Norsk Hydro ASA
Current assignee: Norsk Hydro ASA
Priority date: 2000-06-21
Filing date: 2001-06-20
Publication date: 2003-05-02
Also published as: NO20003243D0; NO20003243L; AU2001274690A1; WO2001098146A1; NO313506B1

Abstract

The present invention concerns an apparatus and a method for filling and sealing bags and sacks, in particular big bags comprising a liner with a filling connection piece (10), which has a filling opening. The apparatus consists of a filling station (1), a sealing station (2) and possibly a tensioning station (3), mounted in this order along a conveyor belt (7). The filling station is provided with a filling pipe (4). The appartus also comprises a stretching device (5) with needles (51, 51', 51', 51'''). In connection with filling, the stretching device stretches the sack's filling opening in the filling connection piece open and accompanies the filling connection piece until it has reached the sealing device (8) at the sealing station. Before sealing, which is prefrably done by welding, air is extracted from the sack. The stretching device is then returned to its initial position where a new sack may be ready for filling or is being prepared for filling. The surplus part of the filling connection piece (10) is expediently cut off after sealing. The proposed solution also comprises an improved tensioning station. The present invention enables good automatic sealing to be achieved without the filling process being delayed, while the stretching device ensures good support to the sack/liner during the various operations.

Description

An apparatus and a method for filling and sealing bags and sacks

The present invention relates to an apparatus and a method for filling and sealing bags and sacks, in particular big bags. More specifically, the present invention relates to an apparatus and a method for the automated sealing of plastic bags and sacks such as sacks with an outer woven fabric having an inner sack or liner and a filling connection piece at the filling opening. The sack may also comprise a lifting strap or handling in its upper part. In accordance with the present invention, the filling opening is stretched open using an improved stretching device which may accompany the sack during transport on a conveyor belt to a sealing station, which may consist of a welding station with a welding device.

The applicant's previous patent application NO 942604 concerns an apparatus and a method for packing and sealing bags and sacks with a filling connection piece comprising a filling opening. The solution comprises a filling station, a welding station and a tensioning station mounted in this order along a conveyor belt. The solution also includes a filling pipe equipped with two slots for the introduction of stretching devices which stretch the sack's filling opening. One limitation in connection with this solution is that residual air must be extracted after filling at the filling station, which reduces the capacity of this installation.

The present invention allows the capacity of an apparatus such as that described above to be improved. The invention comprises a new, improved solution for securing the filling connection piece with its filling opening during transport from filling to sealing/closure. With the present solution, the filling opening is kept stretched open in such a way that the extraction pipe can easily be introduced into the filling opening after the sack has been transported away from the filling station. Expediently, the air is extracted from the sack immediately before sealing so that as little air as possible is in the sack when it is closed. Stretching open the filling opening in accordance with the present invention also reduces the risk of folds occurring during sealing, while ensuring that the sack is positioned precisely. Therefore, the possibility of achieving a tight seal in the form of a weld or similar applied to the desired part of the filling connection piece is increased. The purpose of the present invention is to provide an improved apparatus and automated sealing of plastic bags and sacks or sacks with an outer woven fabric and an inner liner, in particular big bags, without the packing process being delayed, while ensuring that repetition can be maintained.

The present invention concerns an apparatus and a method for automatic packing and sealing of bags and sacks of plastic film or woven plastic-coated fabric. The present invention is particularly suitable for big bags comprising a liner of, for example, polyethylene plastic. The present invention comprises an apparatus and a method with high packing capacity and with good evacuation of air from the sack before sealing. The latter is important because the filled sack is more stable if there is little residual air in the product.

The special features of the present invention are as defined in the attached claims.

The present invention will be described in further detail in the following with reference to the attached figures.

Fig. 1 shows a filling station, a sealing station and a tensioning station mounted along a conveyor belt,

Fig. 2 shows a section of a filling pipe and a stretching device, seen from above,

Fig. 3a shows a diagram of a sack in the stretched position with an extraction device, seen from the side,

Fig. 3b shows a diagram of a section through A-A in Fig. 3a,

Figs. 4a-c show diagrams of the various process stages in connection with filling a sack/liner in a filling station,

Figs. 5a-d show diagrams of the stages for evacuation and sealing of a sack/liner in a sealing station, Figure 6 shows a diagram of the upper part of a tensioning station, seen in the direction of the arrow "X" in Fig. 1.

As shown in Figure 1 , the apparatus comprises a filling station 1 , a sealing station 2 and a tensioning station 3. A (telescopic) filling pipe 4, which can be raised and lowered, is mounted at the filling station. The filling pipe 4 is designed to be entered into a filling connection piece on a sack. A stretching device is also mounted to secure the sack's filling connection piece (not shown). The figure also shows schematically of a sack 9 with a filling connection piece 10. The sack shown in the figure is a big bag with an inner liner, of which only the filling connection piece is visible, and outer reinforced fabric 11 with a lifting handle/strap 12.

Based on prior art, the filling pipe can be linked to an inflation mechanism, a store for metering a product or a spot extraction device which consists of a sheath surrounding the filling pipe and can be connected to a control panel (not shown). The filling pipe can be telescopic and is designed so that it can be moved up and down. A stretching device is, in its initial position, placed by the filling pipe and can be brought into a position around it. The stretching device comprises needles which can be moved in relation to each other in a principally horizontal direction and are shown in detail in Figure 2. The stretching device 5 is designed to move between the filling station and the sealing station. The movements of the stretching device are controlled automatically. The sealing station as shown in the figure comprises a welding device 8 which consists of welding trays for discontinuous welding (only shown schematically). The tensioning station can comprise a device which grasps the sack's lifting handle/strap. The tensioning station can also comprise a device which pushes the sealed filling connection piece into the outer sack while the lifting strap is tensioned. Alternatively, this can be done in the sealing station after the sealing has taken place. A more detailed description of a tensioning station is given under the description of Figure 6. The filling station, welding station and tensioning station are mounted in the stated order along a conveyor belt 7.

As Figure 2 shows, the stretching device 5 comprises pointed, long grippers in the form of needles 51 , 51 ', 51 ", 51 '", which are designed to penetrate the wall of the liner at its filling connection piece 10. This is preferably done as the sack is attached to the filling pipe 4. It may be done after the sack has been filled but before the filling pipe is pulled up and out of the sack's filling connection piece. The needles are arranged so that they lie with their longitudinal axis in the horizontal plane and are also designed for reciprocating movement in their longitudinal direction. The needles' longitudinal direction can be such that it mainly coincides with tangents to the outer surface of the filling pipe 4, possibly displaced somewhat in towards the centre of the filling pipe. For design considerations, the needles which cross each other can be mounted at different vertical levels. The filling pipe's outer surface can expediently be cylindrical and have oblong beads 65, 65' in order to support/guide the needles' movements in relation to the pipe. It should be understood that the beads may run in the longitudinal direction of the filling pipe.

As shown in the figure, the needles can be arranged in pairs in two diametrically opposed groups or needle holders 50, 50' with needles 51 , 51' and 51", 51'" in each pair being perpendicular to each other, seen from above. Each needle is mounted as an extension of a linear actuator 52, 52', 52", 52'", which is designed to generate forward and backward (reciprocating) movement. As shown in the example, the actuators are mounted in two movable frame halves 53, 54, each of which can be moved about a swivelling axis 55 and 56 respectively. This movement is generated by the actuator 57, which is articulated with the frame halves via swivels at its ends 58, 59. When the actuator 57 is activated, the frame halves 53, 54 are moved into a position so that they surround the filling pipe. In this position, the linear actuators which drive the needles are activated.

The frame halves are also connected to a movable runner 60, which is designed to interact with a linear mounting or rail 61 , which allows the stretching device 5 to be moved in the horizontal plane. The movement of the runner can be implemented using means of propulsion known to the man skilled in the art and devices for control such as PLC (not shown). An arrangement with more than four needles may also be used in accordance with the present invention, where this is required. For example, it is possible to use two stretching devices which are vertically offset and at 90 degrees to each other. Such an arrangement will then comprise a total of eight needles. Figure 3a shows an extraction device 20, which can be moved into the opening of the filling connection piece 10, preferably when the sack is in the sealing station 2, in order to extract air from the sack before sealing takes place. The filling connection piece is secured by the stretching device 5 (only shown schematically). Alternatively, the air can be extracted while the sack is on its way from the filling station to the sealing station. In this case, the extraction device can be designed for lateral movement together with the sack (not shown). The figure also shows two stretching pins 21 , 22, the function of which will be described later. The stretching pins can each have a swivel 41 , 42 and can also each be permanently connected to an arm 43, 44, which can be moved up and down by means of actuators (not shown).

Figure 3b shows schematically a section through A-A in Figure 3a in which the filling connection piece 10 is held stretched open by means of needles 51 , 51 ', 51", 51'". The extraction device 20 can have an oblong cross-section, adapted to the shape of the opening of the filling connection piece caused by the stretching device.

The method in accordance with the present invention concerns the sealing of bags and sacks, in particular inner sacks or liners for big bags. The present invention is very well suited for packing and sealing big bags in which the inner sack or liner ends in a bottleneck or filling connection piece, or for big bags with a sewn-on filling connection piece. The sack's filling connection piece 10 is threaded onto the filling pipe 4 manually or automatically. The sack is inflated on a signal from the operator or automatically on a signal from a photocell. The stretching device 5 is placed around the sack, preferably before filling with the product starts. Alternatively, this can be done during or after filling but before the sack is moved. The operator signals the filling of the sack. At the same time as the inflation begins, the needles 51 are moved out into their outer position in relation to the actuators 52. This may be done during or after the filling operation but before the filling pipe is withdrawn from the sack's filling connection piece. After a signal from a weighing device (not shown), which records the weight of the filled sack, where the signal indicates that the sack is full, the filling pipe is automatically pulled up and the needles, which are in their outer position, keep the filling opening stretched completely open. The signal which indicates that the sack is full may also be given in another way, for example after a certain filling time has passed, etc. With the stretching device fixed to the filling connection piece/filling opening, the sack can be moved, on the conveyor belt, to the sealing station 2. The stretching device accompanies the sack and thus secures/supports the filling opening during this movement.

Figure 4a shows a diagram, seen from above, of the filling pipe 4 with a filling connection piece 10 attached to it. The needle holders 50, 50' are in their initial positions.

In the position shown in Figure 4b, the needle holders 50, 50' have been moved forward so that they are on either side of the filling pipe. The needles are in their outer positions and have penetrated the filling connection piece 10.

Figure 4c shows the filling connection piece with the stretching devices after filling and during transport to the sealing station. The filling pipe is out of the sack's filling connection piece here and is consequently not shown in the figure.

With discontinuous sealing, the sack is stationary, for example by the conveyor belt being stopped during the sealing process. In this situation, the extraction pipe will be inserted into the sack's opening, after which the needles are withdrawn and the stretching device is returned to its initial position. At the same time, two stretching pins 21 , 22 (Fig. 5a) are activated. Alternatively, the extraction pipe may be designed to be moved together with the sack from the filling station to the sealing station. If the sealing consists of welding, the welding device 8 will consist of welding trays. The welding trays consist of at least one opposite, heated surfaces which are moved towards each other and surround the filling connection piece/liner. The welding trays can in addition be fitted with interacting cold surfaces which exert a clamping effect on the filling connection piece/liner during the welding operation. Such cold surfaces can, for example, consist of horizontal, longitudinal ductile bands on at least one of the welding trays (not shown). The welding trays are moved automatically towards the stretched filling connection piece immediately after evacuation. When the conveyor belt is restarted, the sealed sack is moved to the tensioning station 3 and a new filled sack with a stretched filling opening is moved to the welding station. When the welding has been completed, the stretching pins are withdrawn from the filling opening. Alternatively, the stretching pins can be withdrawn from the filling opening before sealing. In the embodiment shown in Figure 5a, the sack has arrived at the sealing station and an extraction device 20 has been inserted into the filling connection piece 10. The extraction device can expediently consist of a (telescopic) evacuation pipe which can be raised/lowered. The figure also shows, in section, the two vertical stretching pins 21 , 22, the function of which will be described in the following.

In Figure 5b, the needle holders 50, 50' have been removed from the filling connection piece, while the pins 21 , 22, which can be displaced in relation to each other in the horizontal plane, stretch the filling connection piece so that parts of its internal surface are in contact with the extraction device 20. When the extraction operation has been completed, the extraction device 20 is pulled up and out of the filling connection piece, see Figure 5c.

Figures 5c and 5d show the filling connection piece between two welding trays 23, 24. The welding trays are located, in terms of height, below the level at which the stretching pins 21 , 22 stretch the filling connection piece open. The welding trays are moved against the filling connection piece in this stretched state, as shown in Figure 5d.

The surplus length of the filling opening/filling connection piece can expediently be cut using a movable knife or a cutting device while it is secured in the sealing station (not shown). Such a knife can be mounted in reciprocating fashion in the horizontal plane in connection with one of the welding trays at a vertical level higher than the welding tray.

Alternatively, stretching pins can be mounted in connection with the extraction pipe which can be raised/lowered. The welding trays can then be moved against the filling connection piece as the pipe is withdrawn from the filling connection piece or immediately after this has been done. Welding can also take place while the extraction pipe is in the filling connection piece. The extraction pipe is then located at a vertical level higher than the welding trays.

After sealing, the sack may be subjected to a tensioning operation in a tensioning station 3, see Figure 6. In the tensioning station, the upper part of the sack is stretched via its lifting handle by means of a rotating bow or beak 101 , and is then more easily accessible for further transport. (The sack shown in Figure 1 is actually located with its lifting handle at the rear in connection with use in the apparatus, but is shown with its rear side in the figure for the sake of clarity.) At the same time, the filling connection piece will be stuffed into the sack somewhat during this operation. The rotating bow 101 is mounted so that it can rotate around a pivot 104 and is driven by an actuator which is shown in the in position 102 and out position 102'. The actuator is fixed in the frame 105 at a swivel 109 and to the rotating bow at a joint 103, 103'. The frame 105 can be raised/lowered by means of actuators 106, 107 in relation to an upper frame structure 108, which is stationary.

If the filling connection piece is long, it may also be necessary to have a device at the tensioning station which pushes the filling connection piece into the outer sack while the lifting strap is being stretched, possibly before the lifting strap is stretched. The figure shows an insertion device 122 with an inserter 120 in its outer position. In the figure, reference 120' indicates a withdrawn position of the inserter. The inserter may have a linear actuator 121 of the piston/cylinder type.

From the tensioning station, the sack may be moved on the conveyor belt through a labelling station for the application of information and further on out on to a ramp, where it is collected for transport. Alternatively, the traceability (labelling) of the product can be applied to the filling connection piece, preferably in the filling station.

With continuous sealing, such as continuous welding, the welding process takes place while the conveyor belt is moving. The welding device can then consist of at least one heating element and a clamp fitting which grasps one end of the stretched filling opening. The stretching device is then raised (after the needles have returned to their withdrawn positions) and returned to its initial position. The filling opening passes through the welding device at the speed of the conveyor belt for sealing. In this situation, evacuation can expediently take place while the sack is moving to the sealing station.

The sack may also be sealed by a method other than welding. This will depend on, among other things, the type of material of the sack. For example, gluing can be used. The apparatus may also comprise devices for adapting the distances between the filling station, sealing station and tensioning station, as well as their vertical location in relation to the conveyor belt.

Claims

1. An apparatus for filling and sealing bags and sacks, in particular big bags with a liner, comprising a filling station (1), a sealing station (2) and possibly a tensioning station (3) mounted in this order along a conveyor belt (7), where the filling station is provided with a telescopic filling pipe (4) for insertion in a filling connection piece (10) with an opening in the bag or sack, where the sealing station is provided with a sealing device (8) and where stretching devices stretch the filling opening open during one or more of the operations and can be designed to move in the horizontal plane between the filling station and sealing station, characterised in that the stretching devices comprise pointed, long grippers in the form of needles (51, 51', 51", 51'") designed to penetrate the sack in its filling connection piece (10) while the sack is attached to the filling pipe (4).

2. An apparatus in accordance with claim 1 , characterised in that the needles mainly lie with their longitudinal axis in the horizontal plane and are also designed for reciprocating movement in their longitudinal direction.

3. An apparatus in accordance with claim 2, characterised in that the needles' longitudinal direction mainly coincides with tangents to the outer surface of the filling pipe (4).

4. An apparatus in accordance with claim 1 , characterised in that the needles are arranged in pairs, preferably in two diametrically opposed groups (50, 50'), with the needles in each pair having an angular position with respect to each other.

5. An apparatus in accordance with claim 4, characterised in that the stretching devices comprise two sets of two diametrically opposed groups (50, 50') of needles vertically offset in relation to each other.

6. An apparatus in accordance with claim 1 , characterised in that . it also comprises an extraction device (10) to evacuate residual air from the sack before sealing.

7. An apparatus in accordance with claim 6, characterised in that the extraction device (20) is mounted in the sealing station (2).

8. An apparatus in accordance with claim 1 , characterised in that it comprises two stretching pins (21 , 22) for insertion in the filling connection piece before sealing to stretch the latter.

9. An apparatus in accordance with claim 1 , characterised in that the sealing station comprises a knife for cutting surplus length off the filling connection piece; the knife is also designed for reciprocating movement in the horizontal plane.

10. An apparatus in accordance with claim 1 , characterised in that the tensioning station comprises a rotating bow (101) for tensioning the sack's lifting handle.

11. An apparatus in accordance with claim 1 , characterised in that it comprises an insertion device (122) for pushing the filling connection piece into the sack, in particular in connection with filling and sealing big bags which also comprise a liner.

12. A method for filling and sealing bags and sacks, in particular big bags comprising an airtight liner with a filling connection piece (10), in which a telescopic filling pipe (4) is inserted in the filling connection piece and the bag or liner is inflated and filled with goods on a signal, after which the filling pipe (4) is automatically pulled up when the filling process is over; the sack's filling connection piece (10) is kept stretched open by stretching devices (5) while the sack is moved to a sealing station (8) on a conveyor belt (7) for sealing and possibly on to a tensioning station (3) for tensioning of a lifting strap on the sack, characterised in that the stretching devices (5) penetrate the sack or liner at its filling connection piece (10) in an area located at a higher level than where the sealing is to be applied.

13. A method in accordance with claim 12, characterised in that the stretching devices (5) penetrate the sack or liner while the sack is attached to the filling pipe (4).

14. A method in accordance with claim 12, characterised in that residual air in the sack is evacuated (as far as possible) before sealing.

15. A method in accordance with claim 12, characterised in that the sack's filling connection piece is stretched before sealing.

6. A method in accordance with claim 12, characterised in that the sack's filling connection piece (10) is cut off after sealing in an area between where the sealing is applied and where the stretching devices (5) have penetrated the filling connection piece.