GB2055742A - Closing bag mouths - Google Patents

Abstract

The invention relates to a method and apparatus for closing a bag mouth of a bag 18 formed from a heat weldable material after filling the bag through the open mouth thereof. In order to support and present the bag mouth for the closure operation the mouth is supported from within the mouth by flat elements 43 held apart by rams 44 across the mouth to draw the mouth into an elongate form and then the sides of the mouth are pressed together by rams 32 between an elongate heating element 31 and an elongate anvil 37 and the heating element is activated to heat weld the sides of the mouth together to close the mouth. The flat elements 43 may remain in the stretched bag mouth during heat sealing thus interrupting the bag mouth seal or may be retracted before full welding pressure is applied by the anvil and heating element. The bag may be filled through a chute (26) lowerable into the bag and then transferred from the bag-loading station together with the chute and bag-clamp (28), on a supportive trolley (21) to a bag closure station (Figure 1). The anvil 37 is pivotable about rod 35 to an inoperative position to allow feed of the filled bag to the closing station. <IMAGE>

Description

SPECIFICATION Methods of and apparatus for closing bag mouths This invention relates to methods and apparatus for closing of bag mouths and is particularly, although not exlusively, applicable to closure of bags for irregular size produce such as potatoes and the like.

The supply of produce and materials in plastic bags or sachets which are closed by heat sealing or separate tape or wire closures have become com monplace. One method known as "form filling" comprises forming a tube of plastic material containing the relevant produce and heat sealing the tube at spaced intervals along the tube and severing the tube within the width of each heat seal to produce individual sachets or bags. This system is primarily used for forming sachets to contain liquids and by severing the tube at equally spaced loacations along the tube, sachets containing substantially the same volumes of liquid are formed. The system is not however suitable for forming sachets or bags of material containing equal weights of discrete elements of particles such as arises in the case of supply fresh produce e.g. potatoes and the like.

Conventionally bags for fresh produce and the like are individually filled with the appropriate weight of produce and the open mouth of the bag is individally closed. Such closure is normally by means of adhesive tape or wire tether although attempts have been made to heat seal the open ends of such bags.

The attempts have met with little success because of the difficulty of supporting the mouth of the bag containing a considerable weight of produce whilst performing the heat seal.

The object of this invention is to provide a method and apparatus for closing the mouth of a heat sealable bag containing a weight of produce.

The invention provides a method of closing a bag mouth of a bag formed from a heat weldable material after filling the bag through the open mouth thereof comprising the steps of: supporting the bag mouth from within the mouth and applying tension across the mouth to draw the mouth into an elongate form, pressing the sides of the mouth together along a line extending lengthwise of the mouth and heating the bag material along said line to weld the material of the bag mouth on either side ofthe mouth along said line together to close the mouth.

The invention also provides a bag closure apparatus comprising means for releasably supporting a bag with its mouth open for filling, an elongate heating element, an elongate anvil, a pair of substantially flat tensioning elements insertable into the bag through the open mouth thereof, means for separating the elements such that the outer edges of the elements engage the bag under tension to hold the bag mouth closed flat after said support means have released the bag, and means for moving at least one of the heating element and anvil to compress and heat seal the sides of the mouth of the bag together.

The following is a description of some specific embodiments of the invention, reference being made to the accompanying drawings in which: Figure lisa side view of a weighing, bagging and sealing apparatus; Figure 2 is an end view on the arrow A in Figure 1 with the weighing apparatus and a part of the bagging apparatus remitted; Figure 3 is a view from above of the bag closing apparatus of Figure 1, in which some of the elements are shown in the positions that they take up later in the sequence of operation of the apparatus of Figure 1 as compared with the position shown in Figure 1; Figure 4 is a photograph of a part of Figure 1 showing the filling operation of the apparatus in Figure 1; and Figures Sand 7are photographs from different angles of the bag closing apparatus of Figure 1.

Figure 1 shows an apparatus for weighing discrete weights of produce such as potatoes, for filling a bag with a discrete weight and for sealing the bag. This apparatus, 10, comprises a weighing machine, sche matically shown at 11, a streaming conveyor 12, a bag filling station, generally indicated at 13, and a bag closing station, generally indicated at 14.

The weighing machine 11 is disposed on the far right of the apparatus and the conveyor 12 extends right to left to the bag filling station 13. The bag closing station 14 is on the left hand side of the bag filling station 13 and is aligned therewith.

The bag filling station 13 and bag closing station 14 will now be described in detail. As will be seen from the description below some parts of the bag filling station 13 are also utilised in the bag closing station 14. Both stations are mounted in an upright rectangular frame 15.

The bag filling station 13 includes a wicketed bag holder 16 which is mounted immediately beneath the left hand or output end 17 of the conveyor 12.

The bags 18 are formed from a heat weldable plastics and each have an upstanding flap on one side of the bag mouth by which they are attached to the wicket with their mouths uppermost. The wicketed bag holder is arranged to hold a supply of bags 18, so that they extend vertically downwards from the holder.

Mounted immediately above the wicketed bag holder 16 but below the output end 17 of the conveyor 12 is an elongate nozzle 19 extended parallel to the output end of the conveyor pump 19a, the nozzle 19 being disposed and shaped to blow down into and thereby open the left hand most bag 18a on the wicket of bags 18 as shown in Figure 1.

A guideway 20 is mounted in the top of the frame 15 and extends centrally along the top of frame 15 as best seen in Figure 2. Mounted on the guideway is a freely running wheel trolley 21. The trolley 21 supports a vertically downwardly extending rigid guide post 22 and also a vertically acting pneumatic ram 23. A channel 24 is mounted on the downwardly extending piston 25 of the pneumatic ram 23. An elongate open sided chute 26, of generally semihexagonal cross-section, is mounted on the back of the channel 24 to extend downwardly parallel to the axis of the piston 25. The open side of the chute faces towards the conveyer 12. A bearing 27 mounted on the channel 24 is slidably engaged on guide post 22 to guide the channel up and down the post.The chute 26 is tapered at its lower end such that its lower most point is formed by the side which is furthest away from the output end 17 of conveyor 12.

A pneumatically operable pivotable clamp 28 is mounted in the channel 24to clamp against three adjacent faces of the outer side of the chute 26. The clamp 28 is operated by a ram 28a which is energised to close the clamp 28 against the chute by a striker 22a on the lower end of guide post 22 engaging a vaive moving with the ram 28a to clamp the side of a bag extending around the chute to the chute.

A horizontally extending pneumatic ram 29 is mounted atthe upperend offrame 15,and hasa piston rod 30 attached to the trolley 21 to traverse the troiley and with it the chute 26 along the top of the frame 15 from the bag filling station to the bag closing station.

The bag closing station will now be described, principally with reference to Figures 2 and 3. The bag closing station 14 is essentially a heat sealing station and has a horizontally orientated heating element 31 extending widthwise of the frame and is mounted on a pair of spaced horizontally acting pneumatic rams 32 for movement lengthwise in the frame 15. The heat sealing element 31 is connected to a power source (not shown) by lead 31a. The operative surface of heating element 31 faces the output end 17 of conveyor 12. The rams 32 are supported on the frame 15 on a bar 33 mounted at one end on a longitudinal frame member 34 and having a similar mounting (not shown) at the other end of the bar.In an alternative construction the rams 32 may be rigidly mounted directly on the frame 15 and the heating element may be carried by a pair of vertical swinging links privotally mounted in the frame.

A shaft 35 extends horizontally lengthwise of the frame to one side of the frame and is rotatably mounted in bearings (not shown) in the frame. A pneumatic ram 36 is supported on frame 15, by means not shown and is mechanically coupled to a rod 35 for rotating the rod 35. An anvil 37, for co-operating with heating element 31 is rigidly mounted at one end on rod 35. In one rotational position of the rod 35, the anvil 37 extends generally vertically, as shown in Figures 1 and 2, whilst in another rotational position of rod 35, see Figure 3, the anvil extends across the width of frame 15, so that its free end rests on the frame member 34. In this position the anvil extends parallel to the heating element 31 and is held against movement away from the heating element 31 by a stop 38, which is mounted on the frame member 34.A rod 39 is pivotably mounted at one end of the frame 15 and extends across the frame above and behind the level of heating element 31. A platform 40 is fixedly mounted on the rod 39 and extends along the central portion thereof. The platform 40 carries a pair of outwardly extending spaced arms 41, which have pivotal mountings 42 on the platform for rotation of the arms about axes extending generally transverse to the rod 39.

Each arm 41 has a flat finger element 43 at its free end extending at right angles to the respective arm.

The remote edges of the two finger elements 43 are cut away adjacent their free ends as indicated at 43a.

Also mounted on the plaform 40, between the arms 41, are a pair of oppositely facing pneumatic rams 44, the piston rods 45 of which are attached to the respective arm 41, such that rams 44 can be used to swing the arms 41 apart. A spring 41a is connected between the arms 41, adjacent the connections of the pistons 45 and acts in a sense to draw the arms 41 together, so that when the pneumatic rams 44 are not activated the arms 41 incline towards each other and lie at approximately 45" to the rod 39 when the rams 44 are fully retracted. In a further construction the arms may be crossconnected to ensure that the arms move synchronously and that the movement of one arm is "mirrored" by the movement of the other arm.

A pneumatic ram 46 is mounted on the frame 15 and has its piston connected to plaform 40 such that operation of the ram 46 rotates the rod 39 in a sense to drive the finger elements 43 down between the heating element 31 and the horizontal position of angle 37.

Each of the pneumatic rams mentioned above is connected by means of an air line, each of which is indicated-47, to a pneumatic control system, diagramatically shown at 48. The pneumatic control system 48 is connected to a source of compressed air by line 48a. The connection of lines 47 to the system 48 are shown in Figure 3 for most of the pneumatic rams, but for those rams which are only shown in Figure 1 the connections are not shown. It will be appreciated that the connections are of a standard type. It will further be appreciated that the system 48 can either be a unitary control as illustrated in figure 3 or may be constituted by a number of valves distributed about the apparatus. A table 49 extends across the cross-section of frame 15 beneath element 34 and rod 35 to support the lower edges of bags 18.The table is slightly upwardly inclined from right to left in Figure 1, because as the bags become filled their vertical dimension decreases.

Referring to the weighing machine 11, this machine is shown diagrammatically and can be any weighing machine certified by the Weights and measures Authorities for providing discrete weight batches of potatoes, or whatever particulate material is to be bagged. Each batch when weighed is dispensed by means of hopper 50 onto conveyor 12.

In use the apparatus 10 is initially switched on. The initial switching on of the apparatus 10 causes potatoes to be supplied to the weighing apparatus of the weighing machine 11 and for pneumatic rams 23 to be pressurised along its respective air line 47 by system 48 to drive the chute 26 into the open bag 18, which has been blown open by nozzle 19. The chute 26 is guided into the bag by means of guide rod 22.

As the chute 26 reaches its lowermost position, defined by the movement available to ram 23, in which its tip is fully inserted into bag 18 a valve (not shown) is operated by means (not shown) which causes airto be supplied along line 47 to the clamp 28 rotating the clamp 28 so that it traps the bag betwen itself and the chute 26. This clamping is clearly shown in Figure 4.

When the weighing apparatus of the weighing machine 11 contains the required weight of potatoes it releases them down hopper 50 onto conveyor 12, which streams out the potatoes and delivers them via output 17 into chute 26 through its open side. The chute 26 guides the potatoes into the bag 18, into which it is inserted. This is the stage which has been reached in Figure 4.

After a built-in (but adjustable) time delay which is set to allow time for the potatoes previously weighed and delivered to chute 26 has elapsed, pneumatic ram 29 is activated by means of system 48 and its air line 47 to drive the trolley 21 from right to left along its guideway (as viewed in Figure 1) and hence drive the chute and the filled bag 18 attached thereto towards the bag closure station 14. The pneumatic ram 29 is arranged such that the bag 18 and chute 26 are stopped by the anvil 37. The movement of the trolley 21, frame 24 and chute 26 to this position activates a microswitch, (not shown) which causes system 48 to supply air along the air line 47 of pneumatic rams 46, which rotates rod 39 in a clockwise direction, sweeping fingers 43 down the sides of chute 26 into the bag 18 supported by the chute 26.Preferably the chute 26 is provided with guide elements to help direct the free ends of fingers 43 into the bag 18.

The rotational movement of frame 42 activates a further microswitch (not shown) which causes system 48 to supply air on lines 47 of pneumatic rams 44, which push the arms 41 outwardly, away from each other, causing the outer edges of fingers 43 to engage the bag and to draw the top of the bag 18 into the configuration shown in Figure 13. The activation of rams 44 causes a further microswitch (not shown) to be switched releasing the air pressure on line 47 of pneumatic ram 23, and thus raising the chute 26. The clamp 28 is simultaneously released, so that as the finger elements 43 move outwardly and take support ofthe upper part bag 18 the support of the chute 26 is removed.

Once the chute 26 has reached its fully raised position the trolley 21 is drawn back into the postion shown in Figure 1 and the chute 26 is lowered into the next awaiting open bag 18. Each of these movements is controlled by microswitches, not shown, which detects the end of one movement before the succeeding movement is initiated.

The detection of the return movement of the chute 26 past the anvil to the filling position by a microswitch (not shown) also causes system 48 to supply air on the line 47 connected to pneumatic ram 36, which rotates rod 35 and hence lowers anvil 37 into its lowered position shown in Figure 3.

The lowering of anvil 37 into this position activates a further microswitch which causes pneumatic rams 32 to be activated by system 48 and hence the heating element is driven into engagement with the anvil 37 to heat seal or weld the sides of the mouth of the bag 18 together between the fingers 23. A first time delay device is operated to hold the heating element 31 under pressure against the anvil with the bag mouth trapped therebetween and a second time delay device energises the heating element for a lesser time so that the pressure is maintained at the seal after the heating element is switched off. Both time delay devices are adjustable.At the end of pressure delay, the system 48 causes rams 32 to withdraw heating element 31, ram 36 to raise anvil 37, ram 46 to rotate rod 39 and hence withdraw fingers 43 from the sealed bag 18 and rams 44 to allow spring 41a to return arms 41 into the position shown in Figure 2. Return of the chute to the filling position causes a microswitch operating ram 23 to operate to lower the chute into the next awaiting bag as described earlier.

As described above wicketed bags 18 normally have one side that is the side attached to the wicket, longer than the other. In normal heat sealing operations the seal leaves a flap comprising the extra length of one side. This has to be trimmed off and the trimmed portions are extremely difficult to remove away from the apparatus. In the above described apparatus the downward movement of the anvil 37 catches the extra portion of the wicketed bag and folds it back on itself, so that when the bag is heat sealed the extra portion is sealed in its turned over position. If desired a fan or blower 9 can be positioned to blow between the fingers 43 to turn this extra portion to ensure that the anvil 37 wipes the extra portion completely over into its turned over position. Alternatively the blower alone may be used.

The fingers 43 are dimensioned so that they extend into the bag 18 beneath the level of the anvil 37 and heating element 31 so that the sealed portion of the bag is held fully in tension. This provides a greatly superior seal to that provided by conventional heat sealing mechanisms where the bag is tensioned at a point away from the sealed area, during sealing.

In a further modification of the above system the ram 46 for raising the fingers 43 out of the bag may be triggered to operate when the heating element 31 is first pressed against the anvil 35 but before pressure is fully applied leaving the mouth of the bag supported only by the heating element and anvil. The heat seal subsequently formed is not then interrupted by the fingers 43 and therefore extends across the entire mouth of the bag fully sealing the bag mouth.

Further, a ram operated pusher may be provided for discharging filled sealed bags from the apparatus laterally of the sealing station after the sealing operation has been completed and the heating element been retracted and the anvil raised.

The outer edges of the fingers 43 which engage in the mouths of the bags may also be modified by the provision of one or V-shaped projections on the edges of the fingers to assist in gripping the mouth ofthe bag.

Claims (25)

1. A method of closing a bag mouth of a bag formed from a heat weldable material after filling the bag through the open mouth thereof comprising the steps of: supporting the bag, pressing the sides of the mouth together and heating the bag material to weld the material of the bag mouth on either side of the mouth together to close the mouth, characterised in that the mouth of the bag is supported from within the mouth and tension is applied across the mouth to draw the mouth into elongate form for the welding ofthe bag mouth.

2. A method as claimed in Claim 1 characterised in that the bag mouth is supported and tension is applied across the mouth of the bag to draw it into elongate form by gripping on the side of the bag at opposite locations across and within the mouth and by forcing said loactions apart to hold the bag mouth in tension in elongate form.

3. A method as claimed in claim 1 or claim 2 characterised in that the bag mouth is supported and held in tension throughout the heating operation so that the weld line where the sides of the bag mouth are secured together stops short of the extremeties of the bag mouth where the support and tension force is applied to the mouth.

4. A method as claimed in Claim 1 or Claim 2 characterised in that after the sides of the mouth have been pressed together along said line the support and tension applying force is withdrawn and the sides of the mouth are heated to weld them together along the entire mouth of the bag.

5. A method as claimed in any of the preceding claims characterised in that the sides of the mouth are pressed together by supporting the bag mouth on one side along a line extending lengthwise of the elongate mouth and by applying pressure along a corresponding line along the opposite side of the mouth and applying heat to weld the sides of the bag mouth together along said line on one of the sides of the mouth.

6. A method as claimed in any of the preceding claims charcterised in that the bag mouth on one side of the mouth has an upstanding flap to provide an attachment for a stock of bags and the flap is folded downwardly over the outer side of the bag and is welded to the side of the bag simultaneously with the heat welding of the sides of the bag together.

7. A method as claimed in Claim 6 characterised in that the flap is blown downwardly over the outer side of the bag.

8. A method as claimed in Claim 6 characterised in that the flap is knocked downwardly over the outer side of the bag.

9. A method as claimed in any of the preceding claims characterised in that a bag to be filled and closed is supported along one side, air is blown into the bag to open the mouth of the bag, the other side of the mouth of the bag is supported away from said one side to hole the mouth open, material to fill the bag is fed to the bag, the mouth supporting and tension applying force is applied to the bag and the support for the opposing sides of the mouth of the bag holding the mouth open is withdrawn to allow the mouth of the bag to close under the action of the tension applying force prior to said welding of the sides of the bag mouth.

10. A method as claimed in claim 9 characterised in that the bag is supported with its mouth open at a filling location and is then moved to a mouth closure location where said tension is applied across the mouth to support and elongate the mouth and the sides of the mouth are heat welded together.

11. A bag closure apparatus comprising means for releasably supporting a bag with its mouth open for filling, and elongate heating element, an elongate anvil, a pair of substantially flattensioning elements insertable into the bag through the open mouth thereof, means for separating the elements such that the outer edges of the elements engage the bag under tension to hold the bag mouth closed flat after said support means have released the bag, and means for moving at least one of the heating element and anvil to compress and heat seal the sides of the mouth of the bag together.

12. A bag closure apparatus as claimed in Claim 11 and further comprising means for moving the releasable supporting means for holding the mouth of the bag open from a filling station to a position adjacent one of the heating element or anvil and means for moving the other of the heating element or anvil into a position adjacent to and on the opposite side of the mouth of the bag to said one of the heating element or anvil.

13. Apparatus as claimed in Claim 12 characterised in that the elongate anvil is mounted at one end on a rotary shaft and means are provided for rotating the shaft into and out of alignment with a heating.

element to form a heat sealing operation and to allow a mouth of a bag to be moved into position for the heat sealing operation respectively.

14. An apparatus as claimed in Claim 13 characterised in that the heating element has ram means for forcing the heating element into engagement with the anvil to apply pressure to apply pressure to the mouth of the bag being heat sealed and brace means are provided for supporting the anvil in alignment with the heating element to withstand the pressure applied thereto by the heating element.

15. An apparatus as claimed in any of Claims 11 to 14 characterised in that the flat tensioning elements are mounted on a pair of arms pivotally mounted on a base and ram means are provided for forcing the arms apart to tension a bag mouth in which the elements on the arms are engaged and spring means are provided for drawing the arms together to release the tension when the rams are deactivated and means are provided for lowering and raising the arm to insert and withdraw the tensioning elements in the mouth of a bag respectively.

16. An apparatus as claimed in Claim 15 characterised in that the means for raising and lowering the arms comprise means for mounting the carrier on which the arms are mounted for rotation about a horizontal axis and rams means for swinging the carrier about such horizontal axis.

17. An apparatus as claimed in any of Claims 11 to 16 characterised in that means are provided for holding the supply of bags attached by one side of the mouth of each bag only and means are provided for blowing down into the mouth of the end bag of the supply of bags to open the mouth of the bag.

18. Apparatus as claimed in Claim 17 characterised in that the means for supporting the mouth of the bag open for the filling operation comprise a downwardly extending open sided chute, means to insert and withdraw the chute from an open bag blown open by the air supply and clamping means are provided on the chute for clamping the other side of the bag to that attached to the supply of bags to the outer side of the chute to support the mouth of the bag on the chute during the filling operation.

19. An apparatus as claimed in Claim 18 characterised in that means are provided for moving the chute inserted in and supporting the mouth of the bag from the filling station to a sealing station and means are provided for inserting said flat tensioning elements in the mouth of the bag to support the mouth of the bag and simultaneously release the clamping of the bag to the chute and extract the chute prior to sealing of the bag by said heating element and anvil.

20. An apparatus as claimed in any of Claims 11 to 19 characterised in that the mouth of the bag has, on one side, an upstanding flap and means are provided for guiding the anvil downwardly to engage and turn the flap downwardly as it moves into alignment with the heating element to trap and heat seal the flap to the side of the bag simultaneously with the heat sealing of the mouth of the bag.

21. An apparatus as claimed in any of Claims 11 to 20 characterised in that the mouth of the bag has an upstanding flap on one side thereof and means are provided for directing an air jet on to the flap to turn the flap downwardly to be trapped between the heating element and anvil during the heat sealing operation of the mouth of the bag.

22. An apparatus as claimed in any of Claims 11 to 21 characterised in that means are provided for maintaining the flat tensioning elements in the mouth of the bag during the heat sealing operation by the heating element and anvil so that the heat seal is formed between the opposing sides of the mouth of the bag between the tensioning elements.

23. An apparatus as claimed in any of Claims 11 to 21 characterised in that means are provided for extracting the tensioning elements after the mouth of the bag has been trapped between the heating element and anvil and prior to operation of the heating element so that the heat seals formed between the opposing sides of the mouth of the bag extends across the entire mouth.

24. A method of closing a bag mouth substantially as herein below described.

25. An apparatus for closing a bag mouth substantially as described with reference to and as illustrated in the accompanying drawings.