FIELD OF THE INVENTION

The present invention relates to filling liquids into spray cans or other pressurized containers. More in particular, the invention preferably relates to the filling into canisters, spray cans or pressurized containers of liquids that are sensitive to contact with the ambient air, for example liquids that react with moisture from the ambient air, especially those containing ingredients that polymerize upon reacting with water. Even more preferably, the invention relates to filling into a spray can the ingredients of a composition for forming a polyurethane (PU) foam.

BACKGROUND OF THE INVENTION

Polyurethane foam has many uses, especially in the construction industry. It is often used as a mounting material and as an insulation material, and often also for filling and/or sealing holes and gaps. It is easily applied from a pressurized spray can, readily adheres to most surfaces, and may in many cases also be painted over. Shortly after application, a cuttable, solid and dry foam is formed, so that excess volume may easily be removed. Most spray cans containing PU foam contain a so- called “single component” PU foam (1 k PU-foam), but the family also comprises the so-called 2k and 1.5k versions.

In order to eventually obtain a foaming product, three components are required: the polyol mixture, the isocyanate, and the propellant gas. The polyol mixture and the isocyanate are the necessary ingredients for obtaining a polyurethane plastic. These two components are liquid at atmospheric conditions. The propellant gas ensures that the polyurethane foams and is driven out of the spray can. It does not take part in the reaction but does contribute to the physical properties of the liquid in the spray can, such as its viscosity, as well as the morphological and mechanical properties of het finally cured foam.

With 1 k PU, all of these components are already fully mixed in the same spray can. The 2k PU systems comprise 2 pressurized containers, one containing the polyol mixture and the other containing the isocyanate, and propellant gas pressure in each of the containers causes these components first to be combined and mixed, before the mixture is then immediately expelled. With 1 .5 k systems, inside the spray can is provided a smaller container containing a reagent, usually a fast-reacting polyol. Before the use of the spray can, this small container first needs to be opened or “activated” by the user, for example by turning a knob at the bottom of the spray can, causing the content of the smaller container to be released. By then agitating the whole, the content of the small container may be mixed with the content in the spray can around the small container, and the content of the small container may react with it. Such an activation system is for example described in WO 2016/120336 A1.

With 1 k PU foam spray cans, the polyol mixture and the isocyanate react in the spray can immediately after filling, so as to form the prepolymer. The ratio in which these components are mixed, usually with an excess of isocyanate component, and the nature of the components themselves, determine the final properties of the end product. After being expelled, the prepolymer will foam, and the foaming and/or foamed prepolymer will react with moisture from the ambient air, and possibly also from the substrate with which it comes into contact. This final reaction with moisture is what causes the fresh foam to cure and causes some additional foaming due to the formation of CO2. With 2k and 1.5k PU foam, the final curing is much less dependent, or even barely dependent, on a reaction with ambient moisture.

Today, 1 k PU foam in particular is used both by persons skilled in the art and by DIY enthusiasts, and has earned its standard spot in the toolbox, next to silicone sealant and contact adhesive. The packaging, and especially the development of the valve, have played an important role in this breakthrough and the acceptance of 1 k PU foam as a “practical and hassle-free” product.

For intensive applications, aimed mainly at professionals, a popular option is to use a dosing gun or spray gun or other device that fits conveniently in the hand and usually also allows precise dosing and application, so that even narrow joints can be filled easily and with little waste. For that reason, canisters or containers for such uses come with a specially adapted gun coupling piece or ring, which is placed around the valve on the spray can, and which is intended to allow coupling with the spray gun or other device, which is then usually intended for applying the canister content where it is needed. The gun coupling piece usually also comprises a small protective cover that, as a seal over the valve of the container, protects said valve, and which should be removed before use in order to allow access to the valve. The spray gun may then be twisted onto the ring or onto the gun coupling piece, which is fitted to the canister, using threading or a snap fit system, simultaneously pressing the valve into its open position and thereby making the spray gun immediately ready for use. A suitable and very convenient “Click & Fix” system of a ring and matching spray gun is described in WO 98/43894 and WO 2011/151296 A2. A system with screw threading is for example described in WO 2011/151295 A1 , US 5, 271 , 537 and in EP 2576080.

Containers with polyurethane foam aimed at DIY enthusiasts usually do not have a ring for screwing or snapping on a spray gun. The valve is usually free, and may itself be provided with inner or outer threading, onto which an applicator tube, sold separately or supplied with the product, may then be twisted or screwed, or mounted in any other suitable way, said applicator tube having a small lever thereon which, when pressed, causes the valve to tilt, and thus allows the valve to be opened manually, and closed again when released. For this application, the valve thus needs to be unobstructed, and it is common for the container for DIY enthusiasts to be provided with a protective cap that is removably secured to the container, and thus protects the valve until the moment of use. A suitable protective cap is for example described in EP 2371738 A1 . The pressurized containers or spray cans themselves are usually made of metal and are usually cylindrical in shape. The bottom is usually formed by a plate, which is mounted onto the cylinder by means of a flange, and is usually inwardly concave to better withstand the internal pressure while retaining the ability for the container to stand upright on a flat surface. The top is usually provided with a container head, which is also mounted to the cylinder by means of a flange, and which is usually convex for the same reason of a higher resistance to pressure. A filling opening is provided, usually at a central position in the cylinder head.

Many products are packaged in a spray can or pressurized container from which they may be released by pressure from a propellant gas, such as hairspray, insecticide, shaving foam, paint, deodorant, perfume, penetrating oil or lubricating oil.

Within this large domain, compositions for obtaining PU foam constitute a special category. This is because PU foam compositions are characterized by a very high viscosity, much higher than the viscosity of virtually any other consumer product packaged in spray can form, including lubrication oils.

Although spray cans containing PU foam are sometimes called “aerosol containers”, PU foaming compositions, due to their special characteristics, constitute a separate category within that large family. The development of a suitable valve was vital for the commercial success of PU foam. The valves on spray cans containing PU foam are unusual because they are having a very wide passage, to allow a sufficiently rapid flow of the viscous content out of the spray can.

Most other products packaged in spray cans are much more liquid, and those canisters are therefore fitted with valves having a much narrower passage. Those valves are usually also provided with a so- called dip tube, which conveys liquid from the bottom of the spray can to the valve, so that the spray can may be used in an upright position. This embodiment is only suitable for PU foam compositions if some very specialized adjustments are made. An additional property of spray cans containing 1 k or 1 5k PU foam is that usually, barring some exceptions such as “Multi Position” or MP Foam, they have to be used upside down. This is because the high viscosity of PU foaming compositions is ill-suited for a spray can having a traditional narrow dip tube, due to, among other things, the more difficult trajectory through which the composition needs to pass before being able to exit the spray can through the valve.

The filled spray can is pressurized, and its content is still very reactive due to the excess isocyanate groups, even after the reaction of polyol with isocyanate forming the prepolymer. This reactivity of the spray can content also distinguishes PU foam spray cans from many other spray cans. Such spray cans therefore have to be handled carefully, to prevent the user from coming into direct contact with the still reactive composition. Moreover, it is recommended not to let the still reactive composition end up in places where its rapid curing could cause problems.

During packaging, the empty container is usually filled through the central filling opening in the head, and this opening is then closed off by securing or “crimping” the valve onto the filling opening. Many of the components are liquid under atmospheric conditions, and may thus be filled into the container through the large filling opening, usually an opening of about 2.5 centimeters or 1 inch in diameter, before the canister is closed off. The propellant gasses for providing the higher pressure may then be introduced into the container after it has been closed off with the valve, through the valve, which is pushed open during the injection of the propellant gasses. This commonly used method is called “filling under pressure”. The pressure in the canister then further increases after the container is closed off and the propellant gasses are injected, because an exothermal chemical reaction typically takes place between the components, particularly after shaking the filled container. The propellant gasses could also be injected at the moment of filling the container, for example as a sufficiently cold liquid that may then evaporate after the container is closed. The latter method is however used less and less, because it usually causes higher emissions of propellant gasses, leading to adverse economic and ecological consequences and possible problems concerning industrial hygiene.

Valves for spray cans containing PU foam are characterized, as described above, by a much larger passage than those on spray cans with a less viscous content, to allow a sufficiently rapid outflow. This larger passage also offers advantages when injecting the propellant gas.

Indeed, spray cans containing PU foam are usually much larger than those containing the less viscous compositions listed above. A spray can containing PU foam often has a content of 1000 ml, while spray cans for other uses are often much smaller, at most 400 ml and often only 200 or as little as 150 ml. Usually, the pressure in a spray can containing PU foam is significantly higher than in other spray cans, mainly due to the higher viscosity of the composition in the canister. The amount of propellant gas that needs to be injected is therefore significantly higher in spray cans containing PU foam than in most other spray cans with less viscous contents. The larger passage through the stem of the valve for PU foam offers the advantage that it allows this larger amount of propellant gas to be injected quickly, even if only through the valve stem, so that the step of filling propellant gas does not limit, or only rarely limits the throughput rate of the filling machine.

With valves having narrow valve openings, on spray cans with a much more liquid content, other solutions sometimes have had to be employed to allow more propellant gas to be injected into the spray can quickly. Thus, documents GB 1269801 , US 6283171 B1 , WO 2005/007516 and US H2205 H disclose methods wherein propellant gas is not only injected under pressure through the hollow valve stem, but wherein most of the propellant gas makes its way into the spray can through an opening around the valve stem, which is closed by a seal at rest but, when the valve stem is pressed, opens as well. However, with this method of injecting the propellant gas, propellant gas under pressure needs to be provided above the entire valve. The propellant gas in that space above the entire valve is then lost to the atmosphere when the spray can is removed from under the filling station. In the case of PU foam, the passage in the hollow valve stem alone is already sufficiently large to allow a rapid inflow of propellant gas. It therefore suffices to send the propellant gas through the valve stem. The valve for a spray can containing PU foam, as well as the filling station for injecting the propellant gasses, may thus be kept simpler, without such special provisions.

The valve on a spray can containing PU foam is thus characterized by a usually round valve cup, of which the flat bottom (i.e. the “valve plate”) rises at its periphery and ends in an outwardly curling collar by means of which the valve cup is crimped onto the edge of the filling opening, which is usually centered in the head flanged onto the cylindrical spray can. In the valve collar, a plastic seal is usually provided for sealing between the valve collar and the edge of the filling opening. The valve stem is then resiliently mounted in the bottom of the valve cup, extending centrally above the valve plate that forms the bottom of the valve cup. This resilient mounting may for example be carried out by means of a central rubber seal known as a “grommet” or “valve rubber”, or by means of a steel spring known as a “valve spring”.

By depressing the valve stem relative to the valve collar, towards the valve plate, the valve may then be opened. Many types of valves may also be opened at least partly by pushing the tip of the valve stem to the side, away from its central location, relative to the valve cup.

The applicants have found that injecting propellant gasses into spray cans or pressurized containers, in particular those for PU foaming compositions, is a matter of precision. It is important for the valve, and more in particular the valve stem, to remain in its expected position and for no distortions to occur when injecting propellant gas. The most common possible distortions and the problems these may cause are discussed in detail in WO 2020/128026 A1. Also discussed in that document are the special precautions the applicants are prepared to take to minimize the risk of distortions when injecting propellant gas.

For one, the applicants wish to limit the distance over which the valve stem is pressed in to open the valve and allow the injection of the propellant gas, while still offering sufficient aperture to be able to quickly inject the desired amount of propellant gas into the spray can. Thereby it is very important that the stem of the valve, on the canister in its location in the carousel under the filling head for propellant gas, is in the correct expected position. Both the height and the position relative to the canister itself should correspond to the height and position expected by the filling head in the filling station for propellant gas. It is also important that the canister and the valve crimped onto it do match the type of canister and het type of valve expected by the filling head, especially with regard to the length of the valve stem and the shape of the surfaces of the valve stem with which the filling head should engage in order to press the valve open and also provide an adequate sealing.

Deviations in the position of the valve stem give rise to the risk of distortion and/or damage of the valve during injection of the propellant gas, leading to problems later on when using the spray can.

A filling station for injecting propellant gas is principally a mechanical apparatus, and its proper operation relies on the expectation that at every step of the filling station, a new and correctly filled canister, sealed with a proper valve crimped thereon, is inserted into the carousel, having the expected dimensions and having its valve at the expected height and location. If that expected canister is missing, or if it is not in the expected position, for example slanted or upside down with its bottom pointing upwards, or if it is too small, or if it lacks the expected valve, or if the valve is not at the expected height and/or at the correct position, or if the valve is not secured to the spray can, then the filling station cannot inject any propellant gas, or the propellant gas is lost to the atmosphere, or the valve risks becoming distorted or damaged, or the risk arises for reaction liquids to be released, resulting in contamination of the production environment.

The risk for such an incident is not too high. Such errors in the supply of canisters mostly occur with new or inexperienced operators, or with temporary substitutions. The consequences, however, may certainly be significant, as explained elsewhere in this document.

Other things may also go wrong in the filling station where propellant gas is injected. One important condition is that a canister be present when the filling head descends to inject the propellant gas. Another important requirement is that a valve is actually present on the canister, that the valve is of the expected type, and that the valve is properly secured, or “crimped”, into the filling opening in the canister, and thus not simply lying loosely on top of it, because the canister in that case is not closed off, and the propellant gas does not stay in the spray can but is able to escape to the atmosphere, which could also allow reactive liquids, such as the polyol mixture and/or the isocyanate containing liquid, to be released.

With each of these incorrect supply situations under the filling head in the filling station for propellant gas, the filling station cannot perform correctly as expected, and the production of pressurized spray cans is disturbed. This means that spray cans are produced that are not suitable for commercialization and/or for trouble-free operation. What is produced, instead, usually constitutes an amount of undesired production waste. Moreover, larger amounts of propellant gas and/or other ingredients of the composition in the spray can in such a case be released, with the associated economic and ecological disadvantages, including problems of industrial hygiene.

There is therefore still a need for a method and/or a filling station for injecting propellant gas into a spray can or pressurized container that eliminates these drawbacks and problems, or at least minimizes their consequences.

The present invention aims to obviate or at least mitigate the above described problems and/or to provide improvements generally.

SUMMARY OF THE INVENTION

According to the invention, a filling station and a method as defined in any of the accompanying claims are provided.

In an embodiment, the present invention provides a filling station for injecting at least one propellant gas into a canister that is closed off with a valve in the filling opening of the container head, wherein the filling station comprises a carousel having a plurality of locations occupied by the container in a stepwise fashion during its trajectory through the filling station, and wherein, during a step of the filling station in at least one location in the carousel, a filling head injects propellant gas into the canister through the temporarily opened valve, characterized in that at least one location in the carousel, before the first location with the filling head for the injection of propellant gas, is provided with at least one sensor that is suitable for carrying out at least one of the following observations during the step of the filling station: a) whether a canister is present in that location, b) whether the canister has the expected height, c) whether a valve is present on the canister, and d) whether the valve is secured to the canister.

In an embodiment, the filling station according to the present invention is provided with at least two sensors that are suitable for carrying out at least two different ones of the observations a) to d).

In an embodiment, the filling station according to the present invention is provided for carrying out at least observations a) and b), or a) and c), preferably at least the observations a), b) and c), or a), c) and d), more preferably the observations a), b), c) and d).

In an embodiment, the present invention provides the use of the filling station according to the present invention for filling at least one propellant gas in a spray can or pressurized container.

In an embodiment, the present invention also provides a method for producing a filled pressurized container using the filling station according to the present invention, wherein the method comprises the step, by means of the at least one sensor and during at least one operating step of the filling station, of carrying out at least one observation from the list of the following observations, at the location in the carousel with the sensor, a) whether a canister is present in that location, b) whether the canister has the expected height, c) whether a valve is present on the canister, and d) whether the valve is secured to the canister.

We have found that this invention may greatly reduce the risk for the valve being damaged or the position of the valve relative to the canister being changed during the injection of propellant gas into a spray can or pressurized container using the filling station, for example due to the valve or the valve cup being distorted. The present invention also brings the advantage that when injecting the intended amount of propellant gas, the valve can only be pressed in for a limited distance while still offering sufficient aperture for quickly and efficiently getting the intended amount of propellant gas into the spray can. The present invention also brings the advantage that the filling station may correctly perform as expected, and that the risk for more propellant gas than necessary being lost to the atmosphere is very small. The present invention brings the advantage that it reduces the risk that the production of pressurized spray cans would be disrupted and/or of spray cans would be produced that are not suitable for commercialization and/or for trouble-free operation, at least a portion of which risks needing to be disposed of as production waste. Furthermore, the present invention reduces the risk for more than necessary propellant gas and/or for other ingredients of the composition in the spray can being released, with the associated economic and ecological disadvantages, including problems of industrial hygiene.

Moreover, the present invention improves the safety and industrial hygiene with regard to the staff that is operating, supervising and/or maintaining the filling station .

The production problems described above cause unusable spray cans to be produced, because the valve is no longer usable, because the content of the canister does not have the correct composition or because the canisters are contaminated. This means that the canisters need to be destroyed, leading to loss of production capacity and extra costs. In case of contaminated canisters, action may still be taken by cleaning the canisters, but this, too, creates undesired contaminated solvent waste. The conveyor belts and the filling station also need to be cleaned after having been contaminated, again leading to contaminated solvent waste and requiring labor- intensive intervention and disrupting and reducing production.

The present invention allows timely intervention in the production process, so that the frequency of the interventions as described above may be significantly reduced. This not only allows the productivity of a filling station, and of the associated production line, to be increased, the present invention also offers advantages by reducing the amount of production and/or maintenance waste that needs to be disposed of, and by increasing the safety and/or industrial hygiene of the staff involved in the operation and/or maintenance of the filling station and the associated production line.

The inventors have also found that one and the same sensor may be suitable for carrying out several of the observations a), b), c) and d).

The inventors have found that an embodiment of the sensor that is able to observe whether d) the valve is secured to the canister, may simultaneously observe whether a) a canister is present in the intended location and whether b) the canister has the expected height.

The inventors have found that another embodiment of the sensor that is able to observe whether d) the valve is secured to the canister, may simultaneously observe whether a) a canister is present in the intended location, or b) the canister has the expected height, and whether c) a valve is present on the canister.

The advantage of being able to carry out more than one observation from the list from a) to d) is that the risk of encountering a problem during the injection of the propellant gas is even further decreased, and also that, with adequate processing of the signals from the sensor, the signal may immediately indicate which incident caused the filling station to be shut down, so that the maintenance crew, upon reading out the signal, may already know which problem needs to be solved and what they will likely need for that purpose.

An advantage of having the observation carried out by more than one sensor is that the signal at the same time also shows what caused the filling station to be shut down. In this way, the maintenance crew, upon reading out the signal, may already know which problem needs to be solved and what they will likely need for that purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows in detail a cross-section of a conventional valve for gun foam, before it is “crimped” into the filling opening of a spray can, with the valve in a condition of rest. DETAILED DESCRIPTION

The present invention will hereinafter be described in particular embodiments, and with possible reference to particular drawings, but the invention is not limited thereto, but only by the claims. Any drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions in the drawings do not necessarily correspond to actual reductions to practice of the invention.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than those described and/or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein may operate in other orientations than described or illustrated herein.

The term "comprising", as used in the claims, should not be considered as being limited to the elements that are listed in context with it. It does not exclude that there are other elements or steps. It should be considered as the presence provided of these features, integers, steps or components as required, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the volume of "an article comprising means A and B" may not be limited to an object which is composed solely of agents A and B. It means that A and B are the only elements of interest to the subject matter in connection with the present invention. In accordance with this, the terms "comprise" or "embed" enclose also the more restrictive terms "consisting essentially of" and "consist of". Unless specified otherwise, all ranges provided herein include up to and including the endpoints given, and the values of the constituents or components of the compositions are expressed in weight percent or % by weight of each ingredient in the composition.

The expressions “weight percent”, “%wt”, “percent weight”, and variations thereof, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100, unless specified differently. The same goes, mutatis mutandis, for “ppm” or “ppm weight” or “weight ppm”, in that case by a factor of 1 million (1000000). In this document, “percent”, “%”, “%wt” are intended as synonymous to “weight percent”.

It should also be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes a composition having two or more compounds. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

Additionally, each compound used herein may be discussed interchangeably with respect to its chemical formula, chemical name, abbreviation, etc....

In this document, the terms “pressurized container” and “spray can” are considered as mutually synonymous and meaning the same. The term “canister” in this context is not necessarily always intended to mean a spray can or pressurized container, although that term may also refer to spray cans and pressurized containers.

A propellant gas may be a pure compound, such as dimethyl ether (DME), may also be a mixture of different compounds, such as “liquefied petrol gas” (LPG), which is a mixture that mainly contains propane and butane, but which may also contain other hydrocarbons, saturated and/or un saturated.

In an embodiment of the filling station according to the present invention, the sensor is provided for carrying out its observation at every step of the filling station. This offers the advantage that at every step of the filling station, the risk is avoided for a wrong canister and/or a canister with a wrong or incorrectly placed valve ending up under the filling head for injecting propellant gas in the next step.

In an embodiment of the filling station according to the present invention, an error message of the sensor is provided to shut down the operation of the filling station before the next step of the filling station. This prevents the consequence that in that next step, no canister, or a wrong canister and/or a canister with a wrong or incorrectly placed valve would end up under the filling head for injecting propellant gas.

In an embodiment of the filling station according to the present invention, the sensor is selected from the list consisting of a mechanical sensor, a magnetic sensor, an ultrasonic sensor, a laser sensor, and combinations thereof. The applicants have found that a wide range of sensors may be suitable for carrying out at least one of the observations that are prescribed according to the present invention. The applicants themselves prefer a digital magnetic sensor as described in detail below in the present document. Also suitable, however, is the installation of one or more camera’s at the filling station and analyzing the images with suitable software to determine whether a valve is present at the expected location, and whether that valve is the expected valve. With proper placement, it is even possible to observe through images whether or not the valve is already crimped onto the canister. In another embodiment, the sensor is a laser beam that has to be interrupted by the valve on the canister for a predetermined time.

In an embodiment of the filling station according to the present invention, the sensor is a mechanical sensor, preferably a sensor consisting of a suitable female element that is lowered during the step of the filling station to fit over the valve that is expected to be present on the new canister into which propellant gas would be injected during the next step, and wherein an error message is given if the female element is not stopped within the expected height range by contact with the valve. If the female element is stopped too high, this may for example be caused by the valve not being in the expected location, by the valve having a longer stem than expected, or by the canister itself being higher than expected. If the female element is stopped too low, this is for example caused by the valve having a smaller stem than anticipated, by the canister being too small or being altogether absent, or by no valve being present on the canister.

In this step, also a stamp having elastic protrusions and/or having a ring-shaped elastic outer edge may be provided to be lowered around the valve and to be pressed beyond the valve collar into the valve cup, wherein the elastic protrusions or outer edge have to be able to yield somewhat and open again and settle with the stamp inside the valve cup. When the stamp is then raised again and the canister is simultaneously withheld from raising together with it, it is possible to determine whether the valve has been crimped with the valve collar onto the canister. If the valve has not been crimped, it is raised along with the stamp and the stamp encounters no resistance when being raised again. Furthermore, in this way, it is also possible to determine whether a valve is present on the canister, or if there is no canister present at all, or a canister is present but it is too small. If this occurs, the stamp encounters no resistance while being lowered.

However, the applicants prefer the sensor not to be merely of mechanical nature, but to also comprise electronic elements. The fine mechanical elements that have to be employed for a fully mechanical sensor are more difficult to finetune, more sensitive and more prone to wear. According to the inventors, these secondary problems may be mitigated or even avoided by incorporating electronic elements into the solution of the problem of the present invention where appropriate.

In an embodiment of the filling station according to the present invention, the sensor is provided for detecting the valve if the valve could be picked up from the filling opening of the canister during the step of the filling station. The inventors have found that this is a very elegant and easily executable embodiment for allowing a majority of the desired observations to be carried out.

In an embodiment of the filling station according to the present invention, the valve has a metal valve cup, and when picking up the valve from the filling opening of the canister, the picked-up valve is provided to be detected by means of an inductive sensor that may magnetically detect the metal of the valve cup. The inventors consider this embodiment a highly elegant embodiment for achieving the desired goal and carrying out the required observations.

In an embodiment of the filling station according to the present invention, the valve is provided to be picked up using at least one rubber ring, for example a rubber O-ring, at least one plastic suction cup, for example a rubber suction cup, at least one magnet, preferably an electromagnet, or a combination thereof, preferably using at least one magnet. The inventors have found that in the embodiment using a rubber ring, the ring is subject to wear and has to be replaced regularly to maintain a correct functioning. For that reason, the inventors prefer to use an alternative exhibiting a lower risk of wear.

In an embodiment of the filling station according to the present invention, the filling station is provided for injecting two or more propellant gasses, preferably at least three propellant gasses. The applicants have found that the spray can functions better, and is able to continue functioning for a longer time, if more than one propellant gas is present in the canister. In this way, the pressure profile in the canister may be controlled better during the use of the spray can, and more of the content of the canister may be sprayed out at a suitable pressure.

In an embodiment of the filling station according to the present invention, the filling station is suitable for sequentially injecting the propellant gasses into the same spray can, wherein at least one propellant gas to be injected earlier differs from at least one propellant gas to be injected later. The applicants have found that a better operation of the spray can may be obtained by using different propellant gasses.

In an embodiment of the filling station according to the present invention, the filling station is provided with a plurality of filling heads for injecting the propellant gasses into the canister, preferably at least one filling head for each of the propellant gasses to be injected. The applicants have found that the filling of the spray can may take place more quickly if two or more injections of propellant gas are carried out in the filling station for propellant gas. The desired effect is strongest if those 2 or more injections, even if they are injections of one and the same propellant gas, are carried out by different filling heads.

In an embodiment of the filling station according to the present invention in which a plurality of propellant gasses are injected sequentially into the canister, the propellant gas to be injected earlier has a higher boiling point than the propellant gas to be injected later. A higher boiling point usually entails a lower vapor pressure at the same temperature, especially at the temperature in the spray can. This brings the advantage that the counterpressure in the spray can is lower when injecting the propellant gas injected later, which as a result may be carried out more quickly and easily.

In an embodiment of the filling station according to the present invention in which a plurality of propellant gasses are injected sequentially into the canister, the propellant gas to be injected earlier has a higher solubility in the spray can contents than the propellant gas to be injected later. This, too, brings the advantage that the counterpressure in the spray can is lower when injecting the propellant gas injected later, which as a result may be carried out more quickly and easily.

In an embodiment of the filling station according to the present invention, the valve stem is provided on its side with a shoulder, and the filling head of the filling station contacts the shoulder before the valve stem is pressed in, and the force exerted by the filling head onto the valve stem for opening the valve is preferably at least partly exerted onto the shoulder of the valve stem. This brings the advantage that more contact surface is available for transferring the force required for opening the valve from the filling head to the valve stem. This results in a lower point load on the valve stem, and further lowers the risk of distortion of the valve stem itself.

In an embodiment of the filling station according to the present invention, a gasket is provided between the valve stem and the filling head of the filling station, preferably a plastic gasket, more preferably a gasket made from rubber or polytetrafluorethylene (PTFE), and this gasket is preferably located in the filling head of the filling station. The applicants prefer a gasket made from a resilient plastic. This may be a rubber or a polyolefin, but is preferably polytetrafluorethylene (PTFE). The gasket is preferably located in the filling head of the filling station, so that it does not need to be provided in each valve. If possible, the applicants prefer to have the gasket sealing against the sidewall of the valve stem, so that the force that needs to be transferred from the filling head onto the valve stem for opening the valve does not have to be transferred by the gasket. The applicants have found that this embodiment is suitable for a valve stem having a shoulder. For other valves, especially those having a larger top surface of the valve stem, such as several embodiments of the valves having a valve spring, the applicants prefer to have the filling head sealing against the top of the valve stem, which is preferably made from a resilient material, such as rubber.

In an embodiment of the method according to the present invention, at least observations a) and b), or a) and c) are carried out, preferably at least the observations a), b) and c), or a), c) and d), more preferably the observations a), b), c) and d).

In an embodiment of the method according to the present invention, the at least one observation is carried out at every step of the filling station. This offers the advantage that at every step of the filling station, the risk of a wrong canister and/or a canister with a wrong or incorrectly placed valve ending up under the filling head for injecting propellant gas during the next step is avoided.

In an embodiment of the method according to the present invention, an error message of a sensor shuts down the operation of the filling station before the next step of the filling station. This prevents the outcome that in that next step, a wrong canister and/or a canister with a wrong or incorrectly placed valve would end up under the filling head for injecting propellant gas. Preferably, the filling station is shut down in a position in which the location in the carousel where the problem was observed, is accessible for a human intervention, so that any local problem may quickly be solved.

In an embodiment of the method according to the present invention, two or more propellant gasses are injected into the canister, preferably at least three propellant gasses. The applicants have found that the filling of the spray can may take place more quickly if two or more injections of propellant gas are carried out in the filling station for propellant gas. The desired effect is strongest if those 2 or more injections, even if they are injections of one and the same propellant gas, are carried out by different filling heads.

In an embodiment of the method according to the present invention in which a plurality of propellant gasses are injected into the canister, the propellant gasses are injected sequentially into the same pressurized container, and at least one propellant gas injected earlier differs from a propellant gas injected later. The applicants have found that a better operation of the spray can may be obtained by using different propellant gasses.

In an embodiment of the method according to the present invention in which a plurality of propellant gasses are injected sequentially into the canister, the propellant gas to be injected earlier has a higher boiling point than the propellant gas to be injected later. A higher boiling point usually entails a lower vapor pressure at the same temperature, especially at the temperature in the spray can. This brings the advantage that the counterpressure in the spray can is lower when injecting the propellant gas injected later, which as a result may be carried out more quickly and easily.

In an embodiment of the method according to the present invention in which a plurality of propellant gasses are injected sequentially into the canister, the propellant gas to be injected earlier has a higher solubility in the spray can contents than the propellant gas to be injected later. This, too, brings the advantage that the counterpressure in the spray can is lower when injecting the propellant gas injected later, which as a result may be carried out more quickly and easily.

In an embodiment of the method according to the present invention, the method further comprises the step of shaking the filled spray can. When using multiple propellant gasses, the applicants prefer to inject all of the propellant gasses before shaking the spray can. The purpose of shaking is to better mix the content of the canister, so that the chemical reaction between the isocyanate molecules and the other reagent reacting with it occurs readily, and also to ensure that the propellant gasses partly pass into solution in the liquid in the spray can and form a homogenous entity with it. In an embodiment of the method according to the present invention, the valve is a valve for gun foam. This offers the advantage that, with an appropriate accessory, the spray can may be suitable for use with a dosing gun, but with an appropriately chosen accessory it may also be suitable for manual use, i.e. using an applicator for manual operation, as described below.

In an embodiment of the method according to the present invention in which the valve is a valve for gun foam, the method further comprises the step of affixing an applicator for manual operation that is suitable for a spray can containing gun foam. An applicator for manual operation that is suitable for a spray can with a valve for gun foam is for example described in WO 2012/052449 A2 and US 10106309 B2. This offers the advantage for the producer of the spray cans that in the production line of PU spray cans, only a single line or only a single type of filling station for propellant gas needs to be provided, wherein a valve for gun foam may be fitted to each spray can, but a part of this production may be equipped for use in manual operation, i.e. aimed more at DIY enthusiasts or more casual users. If all spray cans are produced on the same line, this offers the advantage that the production line needs to be converted and adjusted less often, or less extensively, or not at all, when switching over from one embodiment to the other.

In an embodiment of the method according to the present invention in which the valve is a valve for gun foam, the method further comprises the step of affixing a gun coupling piece onto the valve collar, preferably a gun coupling piece with a protective cover. This prepares the spray can for operation as gun foam, i.e. using a dosing gun. The protective cover offers the advantage that the valve of the spray can is protected during handling between the production line and the site where it is to be used, until right before it is coupled with a dosing gun. A suitable gun coupling piece having a breakaway protective cover is for example described in WO 2009/004097 A1 . A suitable gun coupling piece wherein the protective cover is not only removable, but may also be returned in place after a first use, is described in WO 2011/151295 A1. The latter offers the advantage that the valve may also be protected between an earlier use and a later reuse of the same spray can. In an embodiment of the method according to the present invention in which a gun coupling piece is mounted onto the valve collar, the gun coupling piece is suitable for affixing an applicator for manual operation. A gun coupling piece with a protective cover which is suitable for affixing an applicator for manual operation is for example described in WO 2011/151295 A1. The gun coupling piece from WO 2011/151295 A1 thus offers the additional advantage that the logistics supply chain only needs to handle one type of spray can to be able to supply both to professional users, who like working with dosing guns, and to DIY enthusiasts, who prefer working with manual operation.

In an embodiment of the method according to the present invention, the valve is a valve for manual operation. This offers the advantage that, with an appropriate accessory, the spray can is suitable for use with manual operation, such as after mounting an applicator tube or an applicator for manual operation with a lever onto the valve, as described above.

In an embodiment, the method according to the present invention further comprises the step of, after the injection of propellant gas, mounting a protective cap onto the spray can head, preferably a protective cap containing an accessory item, preferably at least one plastic glove, more preferably at least one pair of plastic gloves. A suitable protective cap is for example described in EP 2371738 A1. This protective cap is intended for protecting the valve on the spray can during handling between the production line and the site where it is to be used by the user.

DISCUSSION OF THE FIGURES

The present invention will now be illustrated in further detail through a discussion of Figure 1 .

Figure 1 shows a conventional valve 10 for gun foam, which has not yet been crimped onto a canister, in a condition of rest. The valve comprises a valve cup 1 that consists of a flat valve plate 3 which first extends upwards and then again further sideways into a valve collar 2. By securing this valve collar onto the edge of the opening in the spray can head (not shown), an operation also known as “crimping”, it is possible for the valve to be fixed in that opening and the spray can to be closed, a connection that is sealed using the gasket 6 that is provided inside the valve collar. The valve rubber or “grommet” 5 is centrally affixed to the valve plate 3, and retains the “valve stem” 4 in its location, which is central relative to the valve collar. The valve is closed because the blind flange 7 at the bottom of the valve stem is being pushed up by the valve rubber against the bottom of the valve rubber. The valve stem is further provided with a laterally extending shoulder 8 that offers at its bottom an engagement surface for the upward force of the valve rubber onto the valve stem. The shoulder also offers at its top a possible additional engagement surface for the filling head (not shown), which, by pushing the valve stem downward, is able to open the valve.

The valve 10 is secured or “crimped” onto the canister, wherein the valve is introduced with its valve cup in the filling opening of the canister until the valve collar 2 fits with its gasket 6 onto the rounded and raised edge of the filling opening of the canister (not shown). Then, the valve cup is pressed open from the inside (i.e. “crimped”) right under the valve collar, so that the valve collar clasps tightly around the edge of the filling opening, and the valve is firmly secured. The gasket 6 ensures proper sealing between the valve collar 2 and the edge of the filling opening. A valve that is already crimped to a canister is for example shown in Fig. 4 of WO 2012/052449 A1 , and clearly demonstrates the widening of the valve cup under the valve collar after crimping.

In order to observe whether the valve has effectively been crimped onto the canister, a ring-shaped plastic stamp is introduced into the valve cup. In an embodiment, a rubber O-ring is present on the outside of this stamp, slightly larger in diameter than the opening of the valve collar 2. This O-ring is introduced into the pressed open valve cup, and needs to overcome a resistance in order to arrive past the valve collar. While the canister is held in place in an appropriate manner, and thus cannot be raised, the plastic stamp with its rubber O-ring is pulled back up. If the valve is firmly secured on the canister, the O-ring will again have to overcome the same resistance, then disengage from the valve collar and rise further without entraining the valve. If, on the contrary, the valve has not been crimped, and thus rests loosely on the canister, then the valve in its entirety is raised along with the stamp, and an inductive magnetic sensor may detect the metal of the valve cup, and thus determine that the valve has been taken up with the stamp, and emit a signal based on which the filling station may be shut down. This method of observation also makes it possible to observe whether the canister is effectively present. To this end, the appropriate sensor may be provided on the part of the filling station that is to hold the canister while the sensor is raised back up.

This method of observation simultaneously observes whether a valve is present, because in that case the rubber O-ring meets little or no resistance to arrive past the valve collar, and this absence, or a weaker presence, of the resistance may be detected. If no canister is present, or if the canister is smaller than expected, the O-ring again will not have to overcome any resistance during its up and down movement. However, the inventors have found that in the embodiment described above, the O-ring is quite prone to wear, and therefore needs to be replaced regularly. For that reason, the inventors prefer an alternative in which the stamp is not equipped with an O-ring but with at least one magnet, which is moved past the valve collar and which may entrain the metal valve cup on its way back up if the valve is not firmly secured to the canister. Properly locating the magnet or magnets on the stamp relative to the sensor prevents the observation of the inductive magnetic sensor from being influenced by the presence of the magnet or magnets.

With the invention now having been fully described, it will be appreciated by those skilled in the art that the invention can be performed within a wide range of parameters within what is claimed, without departing from the scope of the invention, as defined by the claims.