invention relates to bag sealing apparatus,

It is known to produce air bags, or air piHows, for use in packaging goods to protect them. Thus, a delicate article might be surrounded with air pillows in a cardboard box to protect it from damage during transport. It is known to make such air pillows from heat seaiabie plastics material and the bags are produced in a strip with each bag being heat sealed from the next. The known sealing method is unreliable however as the back pressure from air in the bag as it is being sealed tends to unseal the bag.

According to one aspect of the invention there is provided bag sealing apparatus comprising a fluid source to pump fluid towards an opening in a bag, means for sealing the opening in the bag and means for clamping the bag downstream of the sealing means to reduce fluid back pressure.

In this way, as the bag is clamped downstream of the sealing means, the back pressure does not operate on "he seal and a good seal can be reliably ensured.

Also the quantity of fluid introduced into the bag can be cioseiy controlled as fluid cannot escape past the

ciampmg means αuπng sealing.

The fluid source may be a source of compressed gas, preferably compressed air.

The sealing means may seal the bag in any suitable way, such as by adhesive or mechanical means, but preferably the sealing means comprises heat sealing means.

The clamping means may comprise a resilient member which is urged against the bag. The resiliency aids in providing a fluid tight seai. Preferably, the ciamping means comprises two resilient clamping members arranged on opposite sides to clamp a bag between them.

Preferably, the ciamping means is arranged to ciamp the bag before the sealing means starts to seai the bag.

The ciamping means and sealing means may be mounted separately, but in one embodiment, a ciamping member of the ciamping means and a sealing member of the sealing means are mounted together on a mounting member. Preferably, on the mounting member, the ciamping member is resiϋentiy mounted ahead of the

sealing member so as to engage the bag before the sealing member. This ensures that the bag is clamped before the sealing operation commences. Preferably, a second mounting member is provided which mounts a second clamping member and/or a second sealing member. Conveniently, only one of the first and second mounting members is movable, but in another embodiment both of the first and second mounting members may be movable towards and away from each other. The or each mounting member is preferably moved pneumatically.

The fluid source may be arranged to pump fluid through a fluid supply pipe.

The apparatus may be arranged to operate in a cycle. The material for the bag may be provided as a strip which is advanced by advancing means through the apparatus.

The means for advancing the bag material may take any suitable form and preferably comprises two rollers side by side between which the material passes. Preferably, at least one of the rollers includes a circumferential recess and the recess or both recesses together receive the supply pipe.

The bag material may be in the form of two layers open

at one side and the fluid supply pipe may extend between the l yers through the open side. Means is preferably provided for sealing the open side.

According to another aspect of the invention there is provided apparatus for making a bag comprising means for advancing material for making a bag from a store, the material being in the form of two layers open at one side, a supply pipe extending between the layers through the open side and means for sealing the open side.

This arrangement allows the bag to be filled directly and without complication.

The material may be open at both sides but preferably is open on only one side. The open side of the material is preferably sealed upstream of the end of the supply pipe. The side sealing means may take any suitable form and may comprise heat sealing means. The side sealing means preferably comprises a member which is movable towards and away from the side of the material. The apparatus preferably includes bag sealing means for sealing the bag after the bag has been filled from the supply pipe. The bag sealing means preferably lies downstream of the advancing means. The bag sealing means preferably includes a

member which is movable towards and away from the material. The bag sealing means and the side sealing means are preferably rigidly connected and moved together. The bag sealing means .-ember and/or the side sealing means member may be moveα by pneumatic means.

The means for advancing the bag material may take any suitable form and preferably comprises two rollers side by side between which the material passes.

Preferably, at least one of the roiiers includes a circumferential recess and the recess or both recesses together receive the supply pipe.

According to a further aspect of the invention there is provided apparatus for making a bag comprising a compressed fluid supply pipe and two roiiers arranged side by side and between which material for making a bag passes, one or both of the roiiers including a circumferential recess and the recess or both recesses together receiving the supply pipe.

In this way the amount of fluid entering the bag can be precisely controlled as backflow past the rollers is limited. Preferably the supply pipe substan ially fills the recess or both recesses. The bag material may be provided as a strip. Preferably bag sealing

means is provided immediately past the rollers. Thus, the bag sealing will leave only a minimal amount of fluid between the seal and the rollers. Preferably clamping means is provided for clamping a bag downstream of the sealing means to reduce fluid back pressure.

Two embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of the apparatus of the first embodiment;

Fig. 2 is a detail side elevation of the heat sealing part of the apparatus of Fig. 1; and,

Fig. 3 is the view of Fig. 2 of the second embodiment.

Fig. 1 shows the apparatus 10 of the first embodiment. A roll of bag material 12 is stored on a spindle and material 14 from the roll passes over an upper roller 16 and downwardly between two advancing rollers 18 which grip the material and are driven by a motor (not shown) to advance the material in steps. The material is in two layers with a fold on one side and being open at the other side.

A pneumatic source powers two pistons 20 provided beneath the advancing rollers IS. At the inner end ci each piston 20 is connected a bag sealing member 22 parallel to and beneath one of the advancing rollers 13. The outer end of each piston 20 is connected to an arm 24 which extends upwardly past the advancing rollers ".5 and inwardly to mount an upright s _^ d member 26. One side member 26 includes a heating element 28 and the other side member 26 mounts a sprung mounted part 30. A compressed air supply pipe 32 extends inwardly parallel to the advancing rollers IS so as to lie between two layers of the material 14 centrally thereof and turns to extend downwardly past the upright members 26 to the advancing rollers '.S . Each advancing roller 18 includes a central circumferential recess 34 such that the material and the end of the supply pipe 32 can be received in the recesses 34. The end of the supply pipe 32 does not extend downwardly past the plane containing the axes of the advancing rollers ;o.

The bag members 22 are shown in detail in Fig. 2. On; of the bag members 22 mounts two vertically spaced heating elements 36. The other bag member 22 carries two spring mounted parts 35 opposite the heating elements 36. Between the spring mounted parts 33 is provided a serrated blade 40. Below the heating

s elements 36, the bag member 22 mounts a projection 42 with a resilient end and a similar projection 42 with a resilient end is spring mounted in an oppositely disposed position on the other bag member 22. These parts are arranged such that when the piston 2C operates to bring the bag members 22 together, the clamping projections 42 will engage first followed by the heating elements 36 and the spring mounted parts 3δ followed by the serrated knife 40 engaging the bag.

In use then, the motor which drives the advancing rollers advances in steps. Once the rollers 18 have been advanced and stopped the pistons 20 are operated and the upright elements 26 are brought together at the open side of the material 14. Current is applied to the heating element 28 to heat seal the edges of the material which is urged against the heating element 28 by the spring mounted part 30. At the same time, the members 22 are brought together. As the members 22 are brought together, the ciamping projections engage the bag material to close it off and the spring mounted parts 38 then urge the material against the heating elements 35 to heat seai the material in two vertically spaced positions. The serrated knife 40 then engages the bag to perforate between the two seals. The pistons 20 are the operated to retract the members 22 and arms 24 and the

advancing rollers 18 are advanced again wh le compressed air is supplied through the pipe 32. When the cycle has been repeated, the first bag nas beer. created. The bags are created in a strip ana can be 5 torn off at the perforated line created by the knife 40.

It is seen that the ciamping projections act to ciose off the area being sealed by the heating element 36 0 from back pressure from the bag which has just been formed so that the seals which are created are not subjected to that pressure until the seals have been formed and cooled to some degree. In th s way a seal is reliably formed. S

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The supply pipe 32 and the recesses 34 in the rollers 18 are sized and spaced in relation to the thickness of the bag material 14 sucn that little or no air can escape backwards between the supply pipe 32 and the 0 roiiers 18 and thus the amount of air supplied to each bag can be controlled precisely and a uniform series of bags produced.

The supply pipe may supply compressed air at 3psi. 25 The bag material may be any suitable heat seaiabie material which provides an air arrier and may be low density polyethylene ;LDFΞ', , for example. The sealing

contact time may be i.o seconds.

The second embodiment is shown in Fig. 3 and is similar to the embodiment of Figs. 1 and 2. Oniy the differences from the first embodiment will be described and the same reference numerals will be used for equivalent features.

The oniy difference in the second embodiment is that the projections 42 are not provided on the bag members 22 but instead are provided on separately operated rams not shown). This enables greater and independent control over the delay between bag ciamping and bag sealing and cutting. It also makes the heating elements 36 easier to change.