EP0078936B1 - Pressured container for delivering assembly foam, especially one-component polyurethane foam - Google Patents

Description

The invention relates to a pressure can for dispensing assembly foams, in particular one-component polyurethane foam according to the preamble of claim 1, the frame of which has a cylinder, a preferably indented bottom and a dome-like upper part with a closure, into which a valve for dispensing a blowing agent and foaming agent existing can filling is used.

The pressure can according to the invention can be filled with differently composed substances. These include rubber-oil, butyl, silicone-acrylate-based sealants and other base materials. The preferred field of application of the invention is that of polyurethane foams, which are used for sealing, filling, isolating, gluing and fastening, in particular in the building industry. In general, u. a. Because of the considerable internal pressure, sheet steel pressure cans with special valves that facilitate the processing of the can contents.

Pressure cans of this type are known (US Pat. No. 3,362,589). According to the invention, a filling is accommodated in the interior of such pressure cans, which, in the preferred field of application of the invention, consists on the one hand of the polyurethane prepolymer comprising different formulation components to about 60% and about 40% of the propellant gas. Part of the propellant gas, which is about 10%. H. of the entire filling, is required as a so-called «yeast for foam formation. The remaining portions of the propellant serve as a means of transportation. Experience shows that if the can is stored for a longer period of time, the recipe components separate. For this reason, intensive mixing must be brought about again shortly before processing by vigorous and long shaking. As far as the gas acts as a blowing agent, it evaporates after the foam emerges. The foam yield is influenced by various factors. Depending on the type of foam, however, the foam yield is approx. 25 to a maximum of 30 liters with the 1 kg pressure cans. So far, it has also not been possible to significantly increase the foam yield. Rather, it is shown that about 5% of the polyurethane prepolymer remains unused in the can after it has been completely emptied of its propellant.

So far, the presumed known pressure can serves various purposes, e.g. B. the spraying of injecticides and fungicidal liquids and prevents on the one hand the contact of the propellant gas with the liquid to be dispensed and on the other hand the passage of the propellant gas into the atmosphere through a flexible piston seal that seals on the wall of the frame cylinder and a lip of the piston skirt, thereby causing the piston forms a partition between a container part containing only propellant gas and a further container part which holds the liquid to be dispensed. When the container closure is open, the piston moves upward under the pressure of the propellant gas and thereby displaces the liquid, which is consequently expelled from the container without the propellant gas. However, this technique requires a complex overall structure of the pressure vessel, which is not portable with the usual substances of the type described in the introduction. In addition, the diversion of the necessary propellant for yeast then makes it difficult.

The invention has for its object to set up the known known pressure can with little effort so that its application technology is simplified.

According to the invention, this object is achieved with the means specified in claim 1. Appropriate areas of application are the subject of the subclaims.

According to the invention, the foaming agent, i.e. H. e.g. B. displaced the polyurethane prepolymer from the initially larger space of the pressure cell due to the propellant pressure applied to the piston head as soon as the valve is opened, from which the foam emerges and as soon as the piston migrates upwards along the cylinder wall. Pressure medium can pass between the piston skirt and the cylinder wall into the foaming agent. In this, it forms part of the required "yeast". The other part was previously placed in the foaming agent when filling the pressure can. On the other hand, the piston prevents the foaming agent from mixing with the pressure medium. Shaking the can before use is therefore no longer necessary. Despite the lack of a piston seal, the escaping quantity is no longer affected by the pressure medium. Pressure fluid can only escape to a small extent and only when the piston has reached the upper end position. In this position of the piston, however, the foaming agent has already been completely emptied.

The invention therefore has the advantage that the passage of the portion of propellant gas used as a means of transport into the atmosphere is largely prevented, but on the other hand the foam yield can be increased considerably. In comparable cases, it is 50 to 60 l, the amount depending on the type of foam. The invention also has the advantage that the new can can be processed in any position. So it does not need to be held vertically with the valve pointing down during operation. This is particularly true in the ceiling area and in hard-to-reach places in construction, e.g. B. when foaming floors cheap.

In general, pressure cans become one at the manufacturer, the dealer and the user time not exactly definable beforehand. Certain foaming agents, especially isocyanate, tend to stick when exposed to atmospheric moisture. In contrast, the only dustproof cap does not protect. Experience has shown that the rubber seal of the valve allows air to diffuse through the valve body from the outside after a certain storage time, so that the contents of the can can no longer be applied when the valve is used. During storage and / or transport, it also happens that the cap loosens and the part of the valve body protruding outwards is pushed. The foam that emerges in turn sticks to the valve and renders the contents of the can unusable.

In order to at least prevent the diffusion of moisture, it is known to provide a desiccant on the inside of the can base, which absorbs the humidity that has penetrated under the cap. In practice, however, it turns out that the type and amount of the desiccant is not sufficient to prevent losses due to diffusing air humidity during the average storage times. In addition, such caps cannot prevent foam from escaping due to the seal becoming leaky in the valve body, just as little as the unintentional or improper operation of the valve.

According to claim 2, the gas exchange of the cap space with the atmosphere is prevented until the can contents are used, and at the same time the valve body is made inaccessible when the cap is intact.

This creates a double seal against diffusing air humidity because the air enclosed with the cap and its brim is sealed off from the contents of the can by the valve seal, while the brim seal seals the enclosed air against the atmosphere. Therefore, the diffusible amount of humidity is reduced so much that the closure is secured against blocking and sticking. On the other hand, the cap can only be removed by destroying its brim. This cannot happen unintentionally. As a result, abuses can be seen when the brim is damaged.

The invention has the advantage that it uses the structural parts predetermined by the valve closure for the attachment and sealing of the cap. By crimping the cap brim, the plate rim can be used as a seat for the ring seal. This results in a great simplification and also a reduction in the cap size, since its diameter can practically be reduced to the diameter of the plate base. This simplification and material saving allows the implementation of the invention without any significant additional effort in spite of the considerable quantities with which such pressure cans have to be brought onto the market.

In the embodiment of the invention according to claim 3, the cap has a cylindrical connecting part between the inner plate edge and the axially blocking edge. Since the axially locking cap edge is flanged inward only when the cap is crimped and previously forms part of the cylindrical portion of the brim, the cap can be simplified as a result.

• Figur 1 schematisch und unter Fortlassung aller für das Verständnis der Erfindung nicht erforderlichen Einzelheiten eine Druckdose gemäß der Erfindung teilweise im Schnitt,
• Figur 2 in vergrößerter Darstellung das obere Ende der Druckdose im Schnitt und
• Figur 3 eine Draufsicht auf den Gegenstand der Fig. 2.

The details of the invention result from the following description of an embodiment with reference to the figures in the drawing; show it

• 1 schematically and omitting all details not necessary for understanding the invention, a pressure can according to the invention, partly in section,
• Figure 2 is an enlarged view of the upper end of the pressure cell in section and
• FIG. 3 is a top view of the subject of FIG. 2.

The pressure cell shown has a frame, generally designated 1, which, according to the exemplary embodiment shown, consists of sheet steel. The middle part consists of a cylinder 2, the lower end edge of which is flanged at 3 together with the edge 4 of a base 6 turned at 5. The upper edge 7 of the cylinder 2 goes into a dome-like, d. H. truncated cone-shaped upper part 8, whose edge 9 surrounding an opening shows a closure, generally designated 11. This closure has a plate 10, the edge 13 is crimped around the edge 9. The plate 10 has a central opening 40 in which a plug-shaped rubber seal 41 of a valve, generally designated 12, is accommodated. The valve body denoted by 42 is tubular and closed at its inner end 43 with a plate which lies on the rubber seal under the influence of the internal pressure. There are one or more openings 44 under the plate and within the tube part sealed to the outside, through which openings the contents of the can can exit as soon as the valve body 42 is tilted and the valve plate 43 is thereby lifted off.

In the cylinder 2, a piston, generally designated 14, is arranged overhung. The piston skirt 15 runs on the cylinder wall, but the piston in the can has enough play to be movable in the direction of the can axis 16 without jamming.

The piston crown 17 closes with its underside 18 a variable lower length 19 of the cylinder 2. The section 19 of the cylinder 2 surrounds a space 20 which is filled with the propellant and is closed off from the can bottom 6. The propellant is filled with a filling needle, not shown, via a radial opening 21 of a valve neck in the can bottom and a valve rubber ring 22 which is placed around the valve neck.

The piston floats on the filling of the propellant gas space 20 and on the liquid Foaming agent, which is located in the room 23 above the piston crown 17. This space is enclosed by the remaining length 24 of the cylinder 2, the dome 8 and the closure 11.

According to the illustrated embodiment, the piston crown is provided on its side facing the space 23 with an indented center 25 and has generally frustoconical edge surfaces 26, which, however, in the illustrated embodiment to the outside, i. H. are convex. Parts of the surfaces 25, 26 can strike the inside of the dome-like upper part or the closure as soon as the piston 14 has reached its upper end position.

The foaming agent is introduced into the can, which is initially open at the top, with a certain amount of propellant gas being added to the foaming agent, which later forms at least part of the yeast. After flanging the rim of the plate around the edge 9, the can is closed. The valve insert 12 forms the inner seal that the user has to overcome when using the contents of the can. However, such a seal can also leak against diffusing moisture for various reasons, in particular during a longer storage period. This would lead to reactions with the foaming agent in the area of the valve insert 12 and thus to sticking and ultimately clogging of the valve. For this reason, a double seal is provided, which is formed from the inner seal by the valve 12 and an outer seal by means of the cap 31 shown generally in FIGS. 2 and 3. The cap 31 is made of sheet metal according to the illustrated embodiment and is generally tubular. Its bottom 30 is arranged so that the valve 12 of the inner seal is underneath. The cap has a brim 32, which is around the closure 11, i. H. around the crimped edge of the plate 10 and therefore also around the edge 9 of the dome 8. Under the inner edge 35 of the brim 32 is an annular rubber seal 36, which brings about the gas-tight closure of the interior of the cap 31 to the outside.

The brim 32 has an end edge 33 which lies under the plate rim and in this way axially blocks the cap 31. This edge 33 also delimits a tab 37 with a recess 38. The tab 37 forms a handle, which is generally designated 34 and by means of which the cap 31 can be separated. For this purpose, the brim 32 is torn and separated with the help of the handle 34.

After the foaming agent has been filled in, the blowing agent can be introduced via the opening 21 and the valve rubber ring 22 with the aid of the filling needle described and which is hollow on the inside. The liquid propellant flows through the filling needle and in this way gets under the piston crown. After the required pressure in the propellant gas space 20 has been reached, the filling needle is withdrawn, as a result of which the one-way valve closes by itself under the influence of the propellant gas. Then the can is ready for use.

Between the piston skirt 15 and the cylinder wall 2, propellant passes into the filling 23 in order to form at least part of the so-called “yeast” for the foam there. On the other hand, the liquid filling 23 cannot pass into the propellant gas space 20 without prejudice to the respective position of the can.

The handle 34 is actuated on the spot by the user in the manner described. This frees the valve 12. If the valve is opened by tilting the plate 43, the piston 14 moves upward. In Fig. 1 the position of the piston is indicated, which it assumes when the can is about half empty. As soon as the valve 12 is closed, the piston 14 remains in the respective position in order to start moving again when the valve is opened again.

Finally, the piston reaches its upper end position, in which it strikes the dome 8 or the closure flap 11. Propellant then presses between the piston skirt 15 and the cylinder wall 2 as a result of the piston play and presses the liquid medium still contained in the greatly reduced or completely closed space 23 through the valve 12 so that the can is completely emptied. The amount of propellant gas exiting through the valve 12 after the can has been emptied is very small. Practically all of the propellant gas required for transport is therefore retained in the can.

Claims (3)

1. A pressurised container for delivering assembly foams, especially one-component foams, which are constituted by a foaming agent and a propellant gas for producing foam, in which the body of the container (1) is in the form of a cylinder (2), preferably having a crimped-over base (6), and a dome-shaped upper section (8) with a closure (11) for delivery of the foaming agent through a valve (12), and in which a travelling piston (14) is movable along the cylinder, with the head of the piston, an upper length (24) of the cylinder, the dome (8) and the closure (11) enclosing the filling which is to..be delivered, whilst the propellant gas is accommodated in a propellant gas chamber formed by the.piston (14), a lower length (19) of the cylinder and the base (6) of the container, the chamber being sealed by a one-way valve fitted in the base of the container or by a plug forced into the base, characterised in that the piston (14) is movable along the cylinder (2) with its shell (15) floating on the propellant gas filling, and that the quantity of propellant gas required for production of foam consists of a _.quantity of propellant gas mixed with the foam- producing filling introduced into the open-topped container (1) in the first instance, and a quantity of propellant gas which passes into the foam- producing filling between the piston shell and the cylinder wall.

2. A pressurised container according to claim 1, characterised in that the valve (12) is fitted under the base of a cap (31) which has a crimped-over rim (32) fitting with its edge around the closure which closes the cap axially, and capable of being prised off with the aid of a handle (34) fitted on the cap, whereby the cap exhibits a crimped-over rim (32) fitting in a gas- tight manner around the edge of the closure with its inner border (35) holding an annular seal (36) on the edge of the plate and exhibiting a rim (33) axially closing the cap (31) which can be prised off with the aid of the handle (34) fitted on the cap (31).

3. A pressurised container according to claim 2, characterised in that the crimped-over rim (32) has a cylindrical connecting piece (39) fitted on the inner border (35) and on the axially closing rim (33).

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