GB2375978A

GB2375978A - Adhesive spray nozzle

Info

Publication number: GB2375978A
Application number: GB0112926A
Authority: GB
Inventors: Darren Lee Ian Williams; Simon Mark Gamble
Original assignee: CB Kaymich and Co Ltd
Current assignee: CB Kaymich and Co Ltd
Priority date: 2001-05-29
Filing date: 2001-05-29
Publication date: 2002-12-04
Anticipated expiration: 2021-05-29
Also published as: GB2375978B; WO2002096570A1; GB0112926D0

Abstract

An adhesive spray nozzle comprises at least two valve assemblies wherein, each valve assembly includes a nozzle through which adhesive can be ejected; and<BR> ```a control means which is capable of actuating each valve assembly alternately so as to effect ejection of adhesive at an overall frequency greater than a maximum operating frequency of one of said valve assemblies.

Description

ADHESIVE APPLICATOR APPARATUS This invention relates to the field of apparatus for applying adhesive to packaging, a paper web or individual piece or the like. The apparatus of the present invention is particularly, but not exclusively, suitable for use in applying adhesive to packaging for cigarettes.

At least two types of apparatus are known for applying liquid adhesive to packaging and each of these is described in turn below.

Spraying Apparatus A spray valve contains adhesive under pressure and includes an orifice through which adhesive is ejected onto the packaging or the like. Normally, the orifice is plugged by a needle which is withdrawn from the orifice periodically in order to allow adhesive to be ejected.

On leaving the spray valve, the adhesive mixes with a controlled air supply which atomises the adhesive.

A problem with spraying adhesive is that too much atomisation may occur which means that airborne particles of adhesive may get spread too widely by the air and may contaminate neighbouring machinery. The spray valve preferably needs to be mounted vertically (downwards) so that the spray does not drop back into the nozzle orifice. Furthermore, since the adhesive is under pressure, the packaging or the like to which the adhesive is being applied has to be secured so that it does not get dislodged by the pressurised adhesive. The spray valve cannot operate particularly quickly, less than 50Hz is typical. Furthermore, the dots of adhesive which can be applied are not particularly accurate and are

typically 8-10 mm diameter with some overspill beyond this diameter.

Jetting Apparatus & I Jetting comprises ejecting pressurised adhesive from a valve in addition using a mechanical device (e. g. a plunger or a diaphragm) having a pumping action which assists in expelling the adhesive. The plunger is seated against a nozzle and, when it is desired to eject adhesive, the plunger moves back to abut an endstop, in order to allow adhesive to fill a cavity near the nozzle.

The plunger then moves forward into the cavity in order to eject the adhesive. The nozzle orifice is typically 0.2-0. 6 mm in diameter, the nozzle size influencing the dot size of the ejected adhesive.

A problem with jetting valves is the tendency for a plug of adhesive to solidify at the end of the nozzle, in the cavity, when the valve has not been used for some time.

Since the jetting valve is typically part of a much larger piece of apparatus, there are a number of reasons why the apparatus as a whole might need to be stopped for a time and the jetting valve needs only be off for 10 minutes or so before a plug of adhesive begins to form.

In order to alleviate this problem, one either needs to clean the nozzle regularly or dock it into a docking station (complex) so that the nozzle is covered and a plug of dried adhesive cannot form.

Jetting valves can operate at a faster speed than spray valves but problems arise above 700Hz, for example the intermittent feeding of adhesive. The jetting valve speed is limited by the available flow of adhesive into the cavity. In the same way the viscosity of the

adhesive affects its running speed; the adhesive needs to be relatively free flowing which limits the range of adhesives which can be used with a jetting valve.

Alternatively, one needs to add water to reduce the viscosity of the adhesive which detrimentally affects adhesion.

Unlike the atomised particles ejected from a spray valve, a jetting valve provides one single dot which may be too wet (given the volume of the dot) causing rippling of the paper or the like to which the adhesive is being applied.

One could alleviate this problem by making the dot size smaller but then one needs to operate the apparatus more quickly if it is desired to apply the same overall amount of adhesive. Eventually, one tends towards a continuous line (i. e. many dots close together).

It is an object of the present invention to provide adhesive applicator apparatus which alleviates the abovedescribed problems.

According to a first aspect of the present invention, there is provided adhesive applicator apparatus comprising a body having at least two valve assemblies mounted therein, each valve assembly including a nozzle through which adhesive can be ejected; and a control means which is capable of actuating each valve assembly alternately so as to effect ejection of adhesive at an overall frequency greater than a maximum operating frequency of one of said valve assemblies.

By operating each of the valve assemblies alternately, the overall frequency with which adhesive can be ejected from the apparatus is potentially double that which is

possible with prior art apparatus which uses only one valve assembly. Since a higher overall operating frequency is possible, a wider range of adhesives (perhaps having greater viscosity than was otherwise possible) can be used which means that the apparatus can be used in many different applications with different types of adhesive.

Preferably, each of said valve assemblies further comprises a plunger moveable within said valve assembly to facilitate ejection of said adhesive. Alternatively, other mechanical means can be included (for example a diaphragm) to facilitate ejection of the adhesive.

Preferably, said nozzle includes a reservoir for collection of a quantity of adhesive before said quantity of adhesive is ejected.

Preferably, said plunger is moveable into said reservoir in order to eject said quantity of adhesive. Ideally, said plunger is shaped so as to minimise dead space in said nozzle when the plunger is in the reservoir. This reduces the likelihood of a plug of dried adhesive forming in the dead space when the apparatus is not in use.

Preferably, said control means, in use, operates each of two of said valve assemblies 180 out of phase with one another.

Preferably, each of said valve assemblies is focused towards a single fixed point.

Preferably, each of said valve assemblies is supplied with adhesive from a common inlet in said body, thus

ensuring that each of the valve assemblies is equally freely supplied with adhesive, in use.

Preferably, each of said valve assemblies is provided with an end stop to limit travel of said plunger within said valve assembly.

Preferably, the apparatus includes two of said valve assemblies, each mounted at 20-25 from vertical and wherein said single fixed point is 10mm from each of said nozzles.

Preferably said plunger is hexagonal in cross-section.

If mounted in a bore of, say cylindrical cross-section, adhesive can advance towards the nozzle between the internal surface of the cylindrical bore and the outer surface of the hexagonal-section plunger. The plunger could equally have a differently-shaped cross-section which provides the same effect.

Preferably, said valve assemblies are solenoid-operated.

Ideally, the adhesive is used to cool a magnetic coil which operates said solenoids.

According to a second aspect of the invention, there is provided cigarette manufacturing apparatus including adhesive applicator apparatus as described in any of the preceding paragraphs.

Preferred embodiments of the present invention will now be more particularly described, by way of example only, with reference to the accompanying drawings in which: Figure 1A is a top view of the lower part of the apparatus body;

Figure 1B is a cross-sectional view of the lower part of the body on line X-X of Figure LA ; Figure 1C is a side cross-sectional view of the lower part of the body on line W-W in Figure 1B ; Figure 2A is a top view of the upper part of the apparatus body; Figure 2B is a cross-sectional view of the upper part of the apparatus body on line X-X in Figure 2A; Figure 2C is a side view of the upper part of the body shown in Figure 2A; Figure 2D is a bottom view of the upper part of the body shown in Figure 2A; Figure 2E is a cross-sectional view on line Z-Z of the upper part shown in Figure 2D ; Figure 3A is a top view of the assembled body; Figure 3B is a cross-sectional view on line X-X of the assembly shown in Figure 3A; Figure 3C is a cross-sectional view on line Y-Y of the assembly shown in Figure 3A; Figure 4A is a front view of adhesive applicator apparatus embodying the present invention; Figure 4B is a top view of the apparatus shown in Figure 4A;

Figure 4C is a side view of the apparatus shown in Figure 4A; Figure 5 is a cross-sectional view, drawn to a larger scale, on line X-X in Figure 4C; Figure 6A is a side view of a plunger; Figure 6B is a top view of the plunger shown in Figure 6A ; Figure 6C is an end view of the plunger shown in Figure 6A; Figure 7A is a perspective view of a nozzle; Figure 7B is an end view of the nozzle shown in Figure 7A; Figure 7C is a cross-sectional view on line A-A in Figure

7B ; Figure 8A is a perspective view of an alternative embodiment of the nozzle; Figure 8B is an end view of the nozzle shown in Figure 8A; Figure 8C is a cross-sectional view on line A-A in Figure

8B ; Figure 9 is a schematic cross-sectional view of the apparatus in use at the start of an application cycle;

Figure 10 shows the apparatus of Figure 9 part way through an application cycle; Figure 11 shows the apparatus of Figure 9 further part way through an application cycle; and Figure 12 shows the apparatus of Figure 9 at the end of an application cycle.

1 adhesive applicator apparatus of the present in en : ion includes a machined body 1 which is shown in more detail in Figures 1A-3C. The body is manufactured in two sections, an upper part 1A shown in Figures 2A-2E and a lower part 1B shown in Figures lA-1e.

Referring firstly to Figures 1A-le, the lower part IB of the body includes two substantially cylindrical bores 2A, 2B which are angled inwardly towards one another as illustrated in Figure IB.

As shown in Figures 2A-2E, there is provided a correspondingly machined upper part 1A of the body which also includes the upper part of the cylindrical bores 2A, 2B. The upper part lA, includes a single adhesive inlet 3 which, in use, provides a flow of adhesive to the bores 2A, 2B via adhesive inlet feeds 4A, 4B respectively.

The upper and lower parts of the body 1 are assembled together as shown in Figures 3A-3C. The upper part 1A mates with the lower part 1B so that the upper and lower parts of the cylindrical bores 2A, 2B are aligned to form two complete bores. At the lowermost end of each of the bores, are apertures SA, 58, through which adhesive, will, in use, be ejected. The upper and lower parts of the body can be machined from stainless steel for example

or could be injection moulded from plastics material.

The upper and lower parts are fastened together using screws with the aid of dowels to ensure alignment of the cylindrical bores 2A, 2B.

The adhesive applicator apparatus further comprises two jetting valve assemblies 6A, 6B which are mounted in the cylindrical bores 2A, 2B respectively as shown in Figures 4A-4C. The valve assemblies 6A, 6B project from the upper part 1A of the body so that they may be connected to control means which controls their operation. The valve assemblies 6A, 6B also project from the lower part 1B of the body, through apertures 5A, 58, presenting nozzles 7A, 7B which are aimed at a fixed focal point where the paper, packaging or the like to which adhesive is to be applied will be situated.

The adhesive applicator apparatus is shown in more detail in the cross-sectional view shown in Figure 5. In this embodiment, the valve assemblies 6A, 6B are identical and therefore description of valve assembly 6A is equally applicable to valve assembly 6B. Valve assembly 6A includes, at its lowermost end, a nozzle 7A through which adhesive can be ejected from orifice 8A.

The valve assembly 6A is also provided with a plunger 9A which is moveable between two positions ; firstly a position in which the plunger blocks the orifice 8A in the nozzle 7A so that adhesive cannot escape and secondly a position where the plunger is retracted away from the nozzle, so that adhesive can flow towards the nozzle, ready to be ejected. In the second position, the plunger 9A abuts an endstop which limits its travel away from the nozzle. The plunger is moved between these two positions

using a solenoid arrangement whereby the plunger forms the core which moves according to the magnetisation of a magnetic coil 10A.

In use, adhesive is supplied to the valve assembly 6A via inlet feed 4A. Since the plunger has a hexagonal crosssection and is located within a substantially cylindrical bore, adhesive 11 can pass down the outside of the plunger and travel towards the nozzle. The plunger itself may also have a bore therein for passage of adhesive from the inlet feed to the nozzle. In the vicinity of the nozzle 7A, there is a reservoir 12A in which adhesive can collect before ejection. The adhesive is ejected when the orifice 8A is open, partly because the adhesive is supplied under pressure and partly because the plunger 9A is forced towards the nozzle, into the reservoir 12A, thus ejecting the adhesive.

The flow of adhesive through the body 1 has the advantage of cooling the magnetic coils 10A, 10B.

Figures 6A-6C show the plunger in more detail. It can be seen that in this preferred embodiment the plunger has a hexagonal cross-section and, at its lowermost end a section of substantially circular cross-section which is the part which enters the adhesive reservoir in the nozzle. The end of the plunger 15 is preferably shaped to coincide with the interior surface of the nozzle so as to minimise dead space in which adhesive could collect and not be fully ejected by the plunger. Reduction of dead space is particularly important since, if the apparatus is not operational for even a few minutes, a plug of adhesive can dry in any dead space meaning that the apparatus needs to be cleaned before it can be restarted.

Figures 7A-7C show the nozzle in more detail. The reservoir 12A where adhesive collects before ejection is preferably of a shape which corresponds with the plunger, as mentioned above to reduce dead space. An alternative embodiment of the nozzle is shown in Figures 8A-8C in which the region around the orifice 8A is flattened, partly to reduce the likelihood of damage to the nozzle by omitting the tip 16 (shown in Figure 7A) and partly to facilitate cleaning of the nozzle and reduction of dead space.

Figures 9-12 show the sequence of operations involved in ejecting adhesive from the adhesive applicator apparatus of the present invention. Initially, as shown in Figure 9, both nozzles 7A, 7B are closed because the plungers 9A, 9B are seated against them. The desired travel of the plunger within the cylindrical bores 2A, 2B can be set by adjusting distance T.

Adhesive is supplied via adhesive inlet 3 and inlet feeds 4A, 4B to the upper part of the valve assemblies 6A, 6B and can travel down towards the reservoirs 12A, 12B. The first stage of the operating cycle is shown in Figure 10.

The control means causes the solenoid of valve assembly 6A to fire, causing the plunger 9A to retreat from the nozzle 7A until it abuts the endstop 17A which limits its travel. As the plunger 9A retreats, a desired quantity of adhesive flows into the reservoir 12A in the vicinity of the orifice 8A and, as shown in Figure 11, when the plunger 9A is moved back into the reservoir 12A, the desired quantity of adhesive will be ejected. At the same time, as shown in Figure 11 the second valve assembly 6B is fired so that the plunger 9B retreats from the nozzle 7B.

Throughout operation of the adhesive applicator apparatus, the control means causes the jetting valve assemblies 6A, GB to fire alternately (i. e. to alternate between the positions shown in Figure 10 and Figure 11) so that a desired quantity of adhesive is ejected from each of the nozzles 7A, 7B alternately. The frequency of firing the valve assemblies is adjustable using the control means and preferably the valve assemblies fire 180 out of phase.

In this way, a dot of adhesive can be ejected from the adhesive applicator apparatus at a rate double that which is possible with a single valve assembly.

When it is desired to cease operation of the apparatus, the plungers are returned to the position shown in Figure 12 wherein they abut the nozzles 7A, 7B and seal off the orifices 8A, 8B. With the reduction in dead space afforded by the correspondingly shaped nozzles and plungers, the tendency for a plug of adhesive to dry at the nozzle is reduced and therefore the apparatus may not need cleaning before being restarted.

The valve assemblies 6A, 6B are mounted preferably at 20- 250 from vertical, the angle being chosen to optimise mounting space within the body 1. The valve assemblies 6A, 6B are"focused"to coincide at a point 10mm away from the nozzles 7A, 7B, this being the distance at which a paper web, or packaging passes by the apparatus. The spacing between the dots of adhesive which are applied to the paper, packaging or the like can be varied by the control system. One can either speed up the paper passing by the apparatus or one can change the frequency of the dots being printed. At high speeds, the dots of

adhesive tend to elongate which improves the wetness problem described above in relation to the prior art wherein the paper or packaging is undesirably rippled by the volume of wet adhesive.

The apparatus of the present invention is capable of operating at an overall frequency of approximately 1Khz, this being significantly higher than is capable by the maximum operating frequency of one single valve assembly.

Use of two valve assemblies solves many of the problems associated with high speed operation of a single valve assembly. There is a reduced likelihood of intermittent feeding of adhesive into the cavity which not only means that the application of adhesive is regular and consistent but also means that a wider range of adhesives (having differing viscosities) can be used with this apparatus. It is envisaged that three or more valve assemblies could be employed in a suitably machined body, which would further increase the speed capability of the apparatus.

Claims

CLAIMS 1. Adhesive applicator apparatus comprising a body having ac least two valve assemblies mounted therein, each valve assembly including a nozzle through which adhesive can be ejected; and a control means which is capable of actuating each valve assembly alternately so as to effect ejection of adhesive at an overall frequency greater than a maximum operating frequency of one of said valve assemblies.

2. Adhesive applicator apparatus as claimed in claim 1 in which each of said valve assemblies further comprises a plunger moveable within said valve assembly to facilitate ejection of said adhesive.

3. Adhesive applicator apparatus as claimed in claim 1 or claim 2 wherein said nozzle includes a reservoir for collection of a quantity of adhesive before said quantity of adhesive is ejected.

4. Adhesive applicator apparatus as claimed in claim 3 when dependent on claim 2 wherein said plunger is moveable into said reservoir in order to eject said quantity of adhesive.

S. Adhesive applicator apparatus as claimed in claim 3 when dependent on claim 2 or claim 4 wherein said plunger is shaped so as to minimise dead space in said nozzle when the plunger is in the reservoir.

1 6. Adhesive applicator apparatus as claimed in any of the preceding claims wherein said control means, in use, operates each of two of said valve assemblies

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1800 out of phase with one another.

7. Adhesive applicator apparatus as claimed in any of the preceding claims wherein each of said valve assemblies is focused towards a single fixed point.

8. Adhesive applicator apparatus as claimed in any of the preceding claims wherein each of said valve assemblies is supplied with adhesive from a common inlet in said body.

9. Adhesive applicator apparatus as claimed in claim 2 or any of claims 3-8 when dependent on claim 2 wherein each of said valve assemblies is provided with an end stop to limit travel of said plunger within said valve assembly.

10. Adhesive applicator apparatus as claimed in claim 7 including two of said valve assemblies, each mounted at 20-250 from vertical and wherein said single fixed point is 10mm from each of said nozzles.

11. Adhesive applicator apparatus as claimed in claim 2 or any of claims 3-10 when dependent on claim 2 wherein said plunger is hexagonal in cross-section.

12. Adhesive applicator apparatus as claimed in any of the preceding claims wherein said valve assemblies are solenoid-operated.

13. Adhesive applicator apparatus as claimed in claim 12 wherein the adhesive is used to cool a magnetic coil which operates said solenoids.

14. Adhesive applicator apparatus substantially as

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described herein with reference to and as illustrated in the accompanying drawings.

15. Cigarette manufacturing apparatus including adhesive applicator apparatus as claimed in any of the preceding claims.