GB2596321A - Methods for filling an aerosol dispenser - Google Patents

Abstract

A method for filling an aerosol can (figure 2a, 1) comprising the steps of introducing a metal valve cup 3a to the can and sealing the valve cup to the can by swaging a periphery of the valve cup inside a rim (figure 2a, 6a) of the can and crimping a periphery of the valve cup under a curl (figure 2a, 6b) of the can. Also a method for filling an aerosol container comprising the steps of introducing a metal valve cup to the container, using a collet to deform a portion of a periphery of the valve cup to attach the valve cup to the container, releasing and rotating the collet, and using the collet to deform a further portion of the periphery of the valve cup to attached the valve cup to the container. Also a method of refilling an aerosol can comprising the step of injecting liquid through a valve cup sealed to the can.

Description

METHODS FOR FILLING AN AEROSOL DISPENSER

BACKGROUND TO THE INVENTION

Conventional aerosol filling systems are capable of handling, filling, gassing, testing, and valve cup placement and sealing for a range of cans of different sizes and materials.

Swaging is a technique used to mechanically attach an aerosol valve to a metal can and is where the valve cup is affixed securely to the can to provide a leak proof seal io between the valve and the can. This is achieved by means of a collet device expanding to push the metal of the side walls of the valve's cup under the curl of the can.

Crimping is an alternative technique used on aerosol containers made from plastics, glass and other materials and is where the valve is affixed to the container by means of a collet device contracting around the valve cup to push the metal of the valve's skirt under the outside rim of the container.

Both techniques are known to have problems in that even though quality control tests may reveal no problems with the integrity of the seal at the point of manufacture it subsequently fails.

Failure may occur for several reasons. For example, the valve mounting cup may not have been swaged with sufficient force to expand the side wall resulting in a looser fitting mounting cup. This increases the chance of a leak as full compression of the gasket seal is not achieved. This may not manifest itself at the time of manufacture or testing but subsequently over the following weeks, months, and years of the product's life. This is known as latent crimp leak.

Additionally, even if the swage is sufficiently tight to stop the valve cup from leaking it so may still be that at higher temperatures the internal pressure rises to such a level as to cause the valve cup to fire out of the aerosol can.

Areas known as collet sections gaps also exist which manifest themselves as small bump areas on the inside of the valve cup's sidewall. These bumps are formed on the swage diameter because of the gap created between the collet sections as they expand to swage the valve into the aerosol container. The collet section gaps cause an uneven swage depth and valve cup height and provide an area of weakness increasing the chances of leakage over time.

The present invention relates to an improved method for sealing a valve cup in place to improve the integrity of the finished seal and to allow for an aerosol container to be re-used / re-filled multiple times.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a method for filling an aerosol can comprises the steps of: introducing a metal valve cup to the can; and, sealing the valve cup to the can by: swaging a periphery of the valve cup inside a rim of the can; and, crimping a periphery of the valve cup under a curl of the can.

Preferably, the swaging step is carried out before the crimping step.

Preferably the swaging step includes creating a first point of hard contact between the valve cup and an inner surface of the can, and the crimping step includes creating a second point of hard contact between the valve cup and an outer surface of the can (i.e. between the valve cup and the outer surface of the curl of the can).

Preferably the method further comprises providing a gasket between the periphery of the valve cup and the rim of the can.

The valve cup may include a dip tube which is preferably formed from a length of hollow fibre membrane having an open end which is coupled to a fluid port in the valve cup and a closed end which sits inside the aerosol can when the valve cup is sealed to the can. The hollow fibre membrane is adapted to pass liquid in preference to gas so that when the can is actuated, liquid travels from the can through the wall of the dip tube under a pressure differential established across the wall of the membrane. In this way, discharging the liquid from inside the can is effective irrespective of the orientation of the can.

According to a second aspect of the present invention, a method for filling an aerosol container comprises the steps of: introducing a metal valve cup to the container; operating a collet to deform at least a portion of a periphery of the valve cup to attach the valve cup to the container; releasing the collet; rotating the collet and/or the container by a predetermined angle relative to each another; and, operating the collet to deform at least a further portion of the periphery of the valve cup to attach the valve cup to the container.

Preferably, the collet is part of a swaging tool, a crimping tool or a combined swaging and crimping tool.

In preferred embodiments, the method of the second aspect is combined with the method of the first aspect when filling metal and plastic cans i.e., there are both swaging and crimping operations with intermediate rotation of the forming tool to improve the resultant seal.

According to a third aspect of the present invention, a method for refilling an aerosol can comprises the step of injecting a liquid through a valve cup that is already sealed to the aerosol can.

In one embodiment, the method includes the additional step of injecting a charge of gas propellent through the valve cup. In such embodiments, the valve cup may include a dip tube having an opening at both ends, one of which is connected to the valve cup and the other which is inside the can. Alternatively, the dip tube may be made from a length of hollow membrane having an open end, which is coupled to the valve cup, and a closed end inside the can, and in such cases the propellent gas may be air.

Preferably, the propellent gas is injected before the liquid. In embodiments where the dip tube is made from a hollow membrane, the can may be injected with gas to top up the pressure to an intermediate value before the liquid is injected to increase the pressure to a final desired value. A volume of liquid may be injected to establish a predetermined gas propellant pressure within the aerosol can.

The gas propellant may be air or nitrogen, for example.

Optionally, the aerosol may retain at least a portion of an original charge of nitrogen propellent such that no further gas propellent is required to refill the aerosol can.

In another embodiment, the method includes filling the aerosol with liquid only. In such embodiments, the valve cup may include a dip tube made from a length of hollow membrane having an open end, which is coupled to the valve cup, and a closed end inside the can, and in such cases the propellent gas may be nitrogen. Alternatively, the valve cup may include a bag on valve arrangement.

In any such embodiments, the method may include injecting the liquid through the fluid port of the valve cup. Alternatively or additionally, the method may include blocking off the fluid port and injecting the liquid via the fluid port gaskets so as to bypass the fluid port. The method may include injecting the liquid through both the fluid port and the fluid port gasket.

The liquid may carry a propellant dissolved in solution.

Preferably, the aerosol can is one that has been manufactured in accordance with the methods of either the first or second aspects of the invention as described hereinabove.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described in detail with reference to the accompanying drawings, in which: Figure 1 outlines the method steps according to an embodiment of the invention; Figures 2a-I show step-by-step operation of the method outlined in Figure 1; Figures 3a-c show the swaging and crimping steps in more detail; Figures 4a and 4b show the swaging step before and after rotation of the collet feet; Figures 5 shows a multipurpose head which performs both the swaging and crimping operations in accordance with another embodiment of the invention; Figures 6a and 6b show examples of an actuator and protective cap that can be used with an aerosol can that has been filled according to the invention. Figure 7 outlines the method steps for refilling according to another embodiment of the invention; and Figure 8 shows a valve cup being refilled.

DETAILED DESCRIPTION

Figure 1 outlines the process steps of an embodiment of the invention. The process steps include presenting an empty bottle to the filling apparatus (step 100) and inserting a liquid into the bottle (step 102). Next, a valve cup is introduced to the bottle (step 104) and the bottle and cup are pre-crimped (step 106) to hold the cup in place.

The inner wall of the cup is swaged to provide a seal between the cup and the bottle (step 108). The teeth of the collet (which is part of the filling apparatus) are rotated and the swage operation is repeated (step 110).

Next, the outer wall of the cup is crimped to provide a further seal between the cup and the bottle (step 112). The teeth of the collet are rotated, and the crimping operation is repeated (step 114).

The invention illustrated comprises both swaging and crimping operations with intermediate rotation of the forming tool, i.e. the collet. However, it will be understood that in other embodiments of the invention the process may include the swaging and crimping operations without intermediate rotation of the collet, or it may include intermediate rotation of the collet while performing only swaging operations or only crimping operations.

Figures 2a-1 show the process steps outlined in Figure 1 in more detail.

In particular, Figure 2a shows an empty bottle 1 as it enters a filling machine via a conveyer belt and is rotated into position by an indexing arrangement (not shown) to a first position. The bottle 1 in this embodiment is a metal can but may instead be a plastic container.

As shown in Figure 2b, liquid is added via a filling head 2 to the bottle 1 to fill the bottle zo 1 to an appropriate level. The bottle 1 is indexed to the next position.

Moving onto Figure 2c, a valve 3 is introduced to the bottle 1. The valve 3 includes a metal valve cup 3a and a dip tube 3b extending from the valve cup 3a. The valve cup 3a includes a gasket 3c which fills a lip/skirt 3d of the valve cup 3a. The dip tube 3b is inserted into the bottle 1 so that the cup 3a rests on the opening of the bottle 1. The bottle 1 indexed to the next position.

As shown in Figure 2d, a pre-crimp head 4 is moved down into position over the bottle 1. The pre-crimp head 4 has two pins 5 that move horizontally to apply a force onto the valve cup 3a. The force of the pins 5 causes an indentation on the side and underside of the valve cup 3a such that it forces the valve cup 3a to protrude into the space on the underside of the rolltop (can curl) 6b of the bottle 1. The rolltop 6b can be seen more clearly in Figures 2a to 2c. This step provides a pre-crimping of the valve cup 3a which holds the valve 3 in place relative to the bottle 1. In particular, it prevents the valve cup 3a from rising up away from the bottle 1 under the force of the dip tube 3b pressing back up on the underside of the valve cup 3a.

The pre-crimp head 4 moves back up and away from the bottle 1. The bottle 1 indexed to the next position Next, a separate swage head 7 comes down and rests on top of the valve 3 (Figure 2e). Then, as shown in Figure 2f, Collet feet 8 inside the swage head 7 exert a force onto the inside of the valve cap 3a so as to indent the valve and grip it tightly onto the inner underside of the neck of the bottle 1 (i.e. inside the rim 6a of the bottle 1). This creates a first (inner) deformation 9a in the valve cup 3a. At the same time, the force of the collet feet 8 pulls the valve cap 3a down onto the valve gasket 3c.

With the swage head 7 still resting on the top of the valve 3, the feet 8 of the collet contract away from the valve 3 and bottle 1 to the start position, as shown in Figure 2g. The feet 8 then rotate by a set number of degrees dependent upon the collet section gap left by the first impression. For example, in a six feet 8 collet arrangement the rotation would be 300. This allows for the centre of each foot 8 to be aligned over the centre of the collet section gap. There may be fewer or more collet feet 8 in the swage head 7 and the amount of rotation would reflect the number of feet 8 present.

Then, as shown in Figure 2h, the feet 8 expand again, exerting a force to the inside of the valve cup 3a to indent the remaining protrusions / bumps (known as the collect section gaps, as referred to above), such that they are the same or close to the same dimensions as of the collet section. This repeated step also helps to even up the existing swage diameter created by the first swage, as it exerts additional force to areas that might not have been fully swaged the first time around. The collet section gap is shown in more detail in Figures 4a and 4b.

The feet 8 then contract again and the swage head 7 lifts away from the bottle 1. The bottle 1 indexed to the next position.

In addition to evening up the swage diameter, rotating the collet and performing a second swage in this manner also evens out the valve cup height/swage depth, which further improves the seal and reduces the chance of a leak. The swage depth is the distance from the top of the valve cup to the centre of the collet section impression.

The table in Appendix A shows the swage depth/valve cup height for the same bottle measured after both the first swage and the second (i.e. rotated) swage using a six-footed swaging collet. The measurements labelled "section" are taken from the centre of each of the six first swage collet impressions, and the measurements labelled "section gap" are taken from the gaps between the each of first swage collet impressions.

After the first swage, the difference between the largest and smallest values is 0.25 mm for the section values and 0.23 mm for the section gap values. After the second swage, these differences have decreased to 0.06 mm and 0.07 mm respectively (reductions of 76% and 70% respectively).

Moving onto Figure 2i, a separate outer crimp head 10 comes down and rests on top of the valve 3.

As shown in Figure 2j, the crimp head 10 is positioned to surround the outside of the valve cup 3a. Crimping feet 11 of the crimp head 10 contract into the valve cup 3a which causes the skirt 3d of the valve cup 3a to bend under the curl 6b of the bottle 1 to create a second (outer) deformation (shown more clearly in Figure 3c) in the valve cup 3a. This step further constricts the gasket 3c because it presses it around the outside of the rim/bead 6b, thus providing for an improved seal.

The crimping feet 11 then expand to release from the valve cup 3a (Figure 2k). With the crimp head 10 still in place over the valve 3, the crimping feet 11 rotate a set number of degrees dependent upon the gap left by the first impression of the crimping feet 11 (also Figure 2k). For example, in a twenty-four feet 11 collet arrangement the rotation would be 7.5°. This allows for the centre of each foot 11 to be aligned over the centre of the external collet section gap.

As shown in Figure 21, the crimping feet 11 contract again into the valve cup 3a, bending the associated areas of the valve skirt 3d, i.e. the areas relating to the external collet section gaps which are not fully curved/crimped under the bottle rim 6. This repeating step also helps to even up the existing crimp diameter created by the first crimp as it exerts additional force to areas that might not have been fully crimped the first time around.

The crimping feet 11 then expand and the crimp head 10 lifts away from the bottle 1.

The bottle is indexed to the next position in the filling line.

The repeated steps of swaging and crimping (i.e. Figures 2g and 2h, and Figures 2k and 21) can be achieved by rotating the bottle 1, rather than rotating the collet 8, 11.

While this can achieve the same result the process unduly increases the time it takes to complete the process as the collet head 7, 10 must be raised before each swage / crimp operation which significantly impacts on the efficiency of the filling line.

It will be appreciated that any number of rotations and repeated swaging and/or crimping steps may be carried out as necessary.

The dip tube 3b shown in the Figures 2a-1 is a flexible tube with an opening at both ends, wherein one open end is secured to a fluid port (or stem) in the valve 3 and the other open end sits inside the bottle 1.

In other embodiments of the invention, the dip tube 3b may instead be made from a hollow fibre membrane (not shown) having an open end which is coupled to the fluid port in the valve 3 and a closed end that sits within the bottle 1.

In such embodiments with a closed ended membrane dip tube, the bottle is self-pressurised, and contains a suitable propellant in addition to a fluid that is to be dispensed. The propellant creates a pressure differential so that when a push-button is manually actuated any liquid within the bottle in contact with any portion of the surface of the dip tube travels through the wall of the dip tube and thereafter along its internal bore to an outlet. This spray bottle operates in substantially any orientation and is effective to dispense substantially the entire contents of the canister.

Hollow fibre membranes suitable for use as dip tubes in this embodiment are available commercially, for example X-flow (TM) capillary membranes from Norit (www.norit.com) may be used.

The hollow fibre membrane for the dip tube preferably comprises materials selected from the group consisting of polytetrafluoroethylene, polyamide, polyimide, polysulfone, polyethersulfone, polyvinylidene fluoride, polypropylene, polyvinyl chloride, polyvinyl pyrrolidone, polycarbonate, polyacrylonitrile, cellulose, cellulose acetate, mixtures, blends and co-polymers thereof.

Preferred hollow fibre membrane materials for the dip tube are selected from the group consisting of polysulfone, polyethersulfone, polyvinylidene fluoride, polyvinyl pyrrolidone, polyacrylonitrile, cellulose, cellulose acetate, mixtures, blends and copolymers thereof.

A particularly preferred hollow fibre membrane material comprises a blend of polyethersulfone and polyvinylpyrrolidone. Polyethersulfone (PES) polyvinylpyrrolidone (PVP) blends are highly oxidant tolerant (>250,000 ppm hours for chlorine, tolerant to permanganate and ozone), are tolerant to wide pH range, and are highly hydrophilic.

Preferred dip tubes have a pore size in the range of 0.05 microns to 0.80 microns. The precise pore size, wall thickness, length, shape and configuration of the dip tube, internal bore, colour, and transparency can be selected according to the fluid to be dispensed and/or the propellant to be used, the resultant nature of the fluid once it is expelled i.e., the fineness of the mist to be created, the degree of atomisation, the mix of propellant to product, and the nature of the container body in terms of size and shape.

Pore size selection should also be chosen based upon the bubble point of the liquid, the start and finishing pressure required, the surface area of membrane of the dip tube in contact with the liquid across the life of the pack.

Flow rate can be controlled by altering the internal bore of the dip tube and by changing the length of the dip tube exposed to the liquid.

The external diameter of the dip tube may be selected according to the internal or external diameter of the fluid port within the dispenser head or any other connecting body.

The hollow fibre membrane used to form the dip tube can be closed at one end by heat sealing/welding, crimping, gluing, chemical sealing, and ultrasonic or high frequency welding.

Suitable containers/bottle include those made of plastics, glass, metals, ceramics, paper or composites.

Although in the above examples only one dip tube is provided, in some preferred embodiments more than one dip tube may be provided. The dip tubes may have the same material properties and performance. Alternatively, the dip tubes may be manufactured to perform differently, for example by varying the pore size, wall thickness, rigidity, shape, materials, coupling position and length. The dip tube may be directly coupled to the valve or may instead be coupled indirectly to the valve via another length of tubing. The dip tubes may be independently coupled to the fluid port and of varying materials properties and performance.

Moving onto Figures 3a-c which show the swaging and crimping operations in more detail. Figure 3a shows the outer skirt 3d of the valve cup 3a extending over the rim 6a and over the curl 6b of the bottle 1. The gasket 3c can be seen between the rim 6 of the bottle 1 and the valve cup 3a.

Figure 3b shows the swage feet 8 exerting a force onto the inside of the valve cup 3a inside the rim 6a of the bottle 1 so as to create the first (inner) deformation 9a. This deformation means that the cup 3a grips tightly onto the inner underside of the neck of the bottle 1 and also forces the valve cup 3a down onto the valve gasket 3c.

Figure 3c shows the crimping feet 11 force onto the outer of the valve cup 3a which causes the skirt 3d of the valve cup 3a to bend under the curl 6b of the bottle 1. This creates a second (outer) deformation 9b in the valve cup 3a. This deformation further constricts the gasket 3c by pressing it around the outside of the rim 6 of the bottle.

The gasket 3c as can be seen from Figures 3b and 3c is compressed further around the bead/rim 6a of the bottle 1, which significantly improves the sealing as it increases the surface area of the gasket 3c which is in contact with the surfaces of the bottle 1 and valve cup 3a. Furthermore, the Point of Hard Contact (PHC -the point at which the wall of the valve cup 3a is pressed against the outside diameter of the bottle 1, i.e. at the inner and outer deformations 9a, 9b) is created across the entire circumference rather than just the areas where the collet feet 8, 11 have swaged and crimped.

Figures 4a and 4b show sectional views of the valve cap 3a. Figure 4a shows the valve cup 3a with the first deformations 9a formed by the swaging collet foot 8 before the swaging foot 8 is rotated. As can be seen, the valve cup 3a has a series of deformations 9a and a series of collet section gaps 13 formed between the deformations 9a.

As shown in Figure 4b, when the collet foot 8 is rotated and swaged again this collet section gaps 13 are essentially removed due to the joined up series of deformations 9a formed around the full circumference of the valve cup 3a.

Figure 5 shows an alternative multipurpose head 14 which performs both the swaging and crimping operations. As outlined above, the previous example uses two separate heads 7, 10, i.e. one for swaging and one for crimping. In the embodiment shown in Figure 5, these two heads are combined such that the single head 14 can both swage and crimp. The multipurpose head 14 includes both types of feet 8, 11 to perform the necessary swaging and crimping. Operation of the head 14 is the same as outlined above except that the head 14 does not need to be moved away from the valve 3 in between operations (other than to permit rotation of the feet, 8, 11, if required).

Figures 7a and 7b show examples of an actuator 14b and a protective cap 14a. The actuator 14b can fit over the bottle 1 and to the valve 3 to permit spray of the medium inside the bottle. The protective cap 14a can be used in transport and removed by the user prior to attaching the actuator 14b.

A known valve insertion machine that could be used to carry out the operations outlined above is a Pamasol Swiss Aerosol Solutions 2018 Centomat Station machine which includes a monobloc consisting of: - 1 Product Filler 2018/112 -Valve Inserter 2047/100 - Vacuum Crimper 2018/212 - Protection Guard - Capacity: 200 containers per minute.

The 2047/100 Valve Inserter machine which operates in conjunction with the Centomat

Station has the following specifications:

- For 1" valves, aluminium and tinplate, dip tube length 50-260 mm - Inserting drum 12-pitch - Valve centering device -Manual height adjustment - Capacity: 250 valves per minute.

A significant advantage of double swaging and single or double crimping the same valve is that, not only does it provide a significant improvement of sealing but it makes it particularly resilient when it comes to refilling and therefore reusing an aerosol.

Current aerosols as designed to be single use (non-reusable). Indeed, the legal definition of an aerosol as described in the Aerosol Dispensers Directive (ADD), Council Directive 75/324/EEC, is a non-reusable container.

Whilst the packaging concept of an aerosol is extremally practical and offers many benefits to the user they are by their very nature an exceptionally wasteful use of resources. Throwing them away every time puts a significant burden on the recycling chain, is costly and inevitably leads to increased carbon footprint and global warming. By refilling the aerosol can either at the point of use, or somewhere along the supply chain such as a supermarket, hospital, business or back at the manufacturer it is possible to significantly reduce the environmental impact of this type of product. Reusing the product just 10x's reduces the carbon footprint by 900%.

In current aerosols, actuators are purposely designed to be thrown away or put into the recycling stream. By applying a simple external crimp, the side wall of the valve curves nicely around the neck rim of the bottle forming an easy surface for the actuator to slide over and to snap fit over and remain in place. When fitting the actuators 14b, as shown in Figure 6b, the actuator remains firmly attached to the bottle but is also easily detachable by the user. This allows for the sale of replacement aerosol canisters fitted with inexpensive reusable protective caps 6a without the need to supply them with a new single use, expensive actuator. The user simply swaps the actuator from the exhausted aerosol canister to the new canister.

Manufacturers of aerosols are constantly pushing for cans to be lighter, primarily to reduce their costs. This offers marginal improvements on carbon footprint but is nothing compared to reusing the can. To further improve the robustness of the can, increased diameters of materials can be used. Instead of using an aluminium can (or valve cup) with a wall thickness of 0.3mm, a can could be used with a wall thickness of 0.8mm or lmm. While this would increase cost of initial production it would significantly improve the robustness of the can throughout its lifetime, allowing it to be reused an increased number of times over the thinner wall sectioned cans.

The same also applies to the valve wall thickness and its materials of construction as well as the gasket seal thickness. Increasing both significantly adds to the length of their lifetime of use. In addition, increasing the wall thickness of the valve significantly increased its strength further preventing it from bending and causing a leak.

Increasing the wall thickness of the valve and body of the can further increase its pressure rating. This is important particularly with compressed gasses. Based upon the principle of Boyles law, the pressure inside the can decreases as the product is expelled. Increasing the overall percentage of product in the can means a disproportionate amount of compressed gas is needed at the beginning to provide an adequate pressure towards the end of the life of the can.

By increasing the wall thickness of the can and the valve you increase the pressure rating of the can so allowing for a greater percentage of product to be added to a can. This means that for the same given size can, the consumer will be able to dispense an increased quantity of product per can. This is beneficial to the consumer as they get more product from the same can. It is beneficial for the environment as it means fewer cans must be transported along the supply chain.

Stainless steel exhibits both increased strength characteristics and significantly improved resistance to chemical characteristics. In the production of metal aerosol cans internal lacquers are used to provide a physical barrier, preventing the chemical meeting the metal. This is done to prevent corrosion as many chemicals used inside (including water) are highly corrosive to metals. Whilst these lacquers help prevent corrosion they add to the cost of manufacture and are also highly environmentally damaging due to the nature of both their manufacture and the processes of applying them to the cans. By using stainless steel, the use of these lacquers can be done away with, further reducing costs, whilst not damaging the environment.

Point of Hard Contact (PHC): The location where the mounting cup contacts the can under the can curl. When determining the proper crimp dimensions for your system, both the diameter and the depth must be considered. A functional crimp may not be obtained if only one dimension is within specification. It takes both the crimp depth and diameter to create the Point of Hard Contact. Furthermore, the PHC is required to obtain a functional seal when using laminate and sleeve gaskets. Using this new method ensures the PHC is achieved all the way round, eliminating the risk of leaks occurring as can happen in the current state of the art.

zo A method according to another embodiment of the invention is shown in Figure 7. The method involves injecting 701 fluid through a valve cup that is already sealed to an aerosol can. The method is for refilling an aerosol can which is already sealed to a valve cup. The refilling method may include refilling the can with both liquid and a propellent gas, or refilling with just a liquid. The circumstances behind these two methods are outlined below.

In circumstances where the valve cup includes a dip tube that has an opening at both ends (one of which is connected to the stem of the valve cup and the other which is inside the can), the propellent gas will be lost as the liquid is dispensed from the aerosol can. As such, the can will need to be refilled with both liquid and gas.

In circumstances where the valve cup includes a dip tube that is a hollow membrane (which passes liquid in preference to gas) having an open end (connected to the stem of the valve cup) and a closed end (inside the can) and air is used as the propellent gas, then some of the air gasses will also be lost through use. This is because the air gasses readily dissolve into solution. For example, if the can is filled with 80% liquid product and compressed air is added at 11 bar, approximately 1 bar of that would go into solution. Thus, it is required in this type of aerosol can to reintroduce some additional compressed air at the refilling stage. It should be noted that this air solution is very helpful in particle break up once the product has left the can.

As an example, an additional 1 bar could be added to the can bringing it up to say 3 bar (i.e. an intermediate value). The liquid is then injected into the can which would compress it back up to 11 bar pressure (i.e. a final desired value). It is preferable to introduce the 1 bar of pressure before the liquid product is filled because this is safer and much faster for production.

In circumstances where a bag on valve arrangement is used, the propellent gas resides outside the bag and so is not lost through use. As such, this type of aerosol can will not need to be recharged with gas. A bag on valve arrangement is known in the field of aerosol cans and includes a bag which is sealed to the valve cup. The bag is then filled with liquid while the gas is filled into the space inside the can surrounding the bag.

Also, in circumstances where a hollow member dip tube (as described above) and nitrogen is used as the propellent gas, the aerosol can does not need to be recharged with gas. This is because nitrogen does not readily go into solution (with water-based products) and the membrane dip tube passes liquid in preference to gas.

As shown in Figure 8, the liquid can be injected through the fluid port of the valve cap (300) or through the fluid port gaskets (302) so as to bypass the fluid port. In the latter option, the valve stem would be blocked off.

Appendix A: swage depth/valve cup height Valve Cup Height (mm) Section Section Gap Section Section Gap Section Section Gap Section Section Gap Section Section Gap Section Section Gap Section Difference Section difference % Section Gap Difference Section Gap Difference a/0 2 2 3 3 4 4 5 5 6 6 Swage 4.9 4.99 4.94 5.06 5.05 5.22 5.12 5.13 5 5.07 4.87 5.03 0.25 N/A 0.23 Swage 2 Rotate CC 4.92 4.94 4.92 4.93 4.95 4.96 4.99 5 4.98 5 4.95 4.99 0.06 76% 0.07 70%

Claims (17)

1. CLAIMS1. A method for filling an aerosol can comprising the steps of: introducing a metal valve cup to the can; and, sealing the valve cup to the can by: swaging a periphery of the valve cup inside a rim of the can; and, crimping a periphery of the valve cup under a curl of the can.
2. 2. A method according claim 1, wherein the swaging step is carried out before the crimping step.
3. 3. A method according to claim 1 or claim 2, wherein the swaging step includes creating a first point of hard contact between the valve cup and an inner surface of the can, and wherein the crimping step includes creating a second point of hard contact between the valve cup and an outer surface of the can.
4. 4. A method according to any preceding claim, further comprising providing a gasket between the periphery of the valve cup and the rim of the can.zo
5. 5. A method according to any preceding claim, wherein the valve cup includes a dip tube formed from a length of hollow fibre membrane having an open end coupled to a fluid port in the valve cup and a closed end which sits inside the aerosol can when the valve cup is sealed to the can.
6. 6. A method according to any preceding claim, wherein the swaging and/or crimping step further include: operating a collet to deform at least a portion of the periphery of the valve cup to attach the valve cup to the can; releasing the collet; rotating the collet by a predetermined angle; and, operating the collet to deform at least a further portion of the periphery of the valve cup to attach the valve cup to the can.
7. 7. A method for filling an aerosol container comprising the steps of: introducing a metal valve cup to the container; operating a collet to deform at least a portion of a periphery of the valve cup to attach the valve cup to the container; releasing the collet; rotating the collet by a predetermined angle; and, operating the collet to deform at least a further portion of the periphery of the valve cup to attach the valve cup to the container.
8. 8. A method according to claim 7, wherein the collet is part of one of a swaging tool, a crimping tool, or a combined swaging and crimping tool.
9. 9. A method of refilling an aerosol can comprising the step of injecting a liquid through a valve cup that is already sealed to the aerosol can.
10. 10. A method according to claim 9, further comprising the additional step of injecting a charge of gas propellent through the valve cup.
11. 11. A method according to claim 10, in which the gas propellent is injected before the liquid propellent.
12. 12. A method according to claim 11, in which a volume of liquid is injected to establish a predetermined gas propellent pressure within the aerosol can.
13. 13. A method according to any of claims 10 to 12, wherein the gas propellent is air or nitrogen.
14. 14. A method according to claim 9, in which the aerosol retains at least a portion of an original charge of nitrogen propellent such that no further gas propellent is required to refill the aerosol can.
15. 15. A method according to any of claims 9 to 14, wherein the step of injecting the liquid includes injecting the liquid through a fluid port of the valve cup and/or blocking off a fluid port of the valve cup and injecting the liquid via fluid port gaskets.
16. 16. A method according to claim 9, in which the liquid carries a propellent dissolved in solution.
17. 17. A method according to any one of claims 9 to 16, wherein the aerosol can is one that has been manufactured in accordance with the method of any of claims 1 to 8.