1. Field of the Invention
The invention relates to a device for the region of cans held under propellant pressure where liquid to pasty substances containing solvent pass out, including an operating device for delivering the substances.
It is known to store substances initially in cans, in which they are held under pressure. This pressure can be produced in various ways, for example by means of a propellant gas, bladders under internal pressure, pistons under spring pressure, or the like. When an operating device is operated, the substance passes out into the atmosphere. For this purpose, a spring-loaded button is pressed. A part of this actuating device can also be tilted by pulling a lever 36, so that the substance passes out of the tube 37, as described in European Patent Application 91 114 634.8. The substances may, for example, be lacquers, lubricants and, in particular, substances which in the air harden to a foam.
2. Discussion of Prior Art
It has become possible, in accordance with Swiss Patent Document CH-PS 676 354, to produce the valve part of the operating device without rubber or other comparable substances. Such devices can consequently be stored and transported even in a horizontal position. However, the weakest link in the chain is still the region downstream of the valve. The substance, particularly the one which subsequently forms the polyurethane foam, can there form a clot. Although the problems in the valve region have been overcome, it is therefore possible to use the can only once if the substance contained in the so-called stem loses solvents through evaporation. In addition, moisture can pass from the interior to the exterior of the device, and also in particular from the exterior to the interior.
Particularly in the field of hobbies it is known that small amounts of substances are needed. If larger amounts are bought, this is detrimental in various respects: more than is needed is bought. The unused residues must be disposed of as special refuse. To some extent this is also the case when smaller cans are produced. It would, however, be more advantageous also to make larger cans available for hobby purposes, provided they can be used until they are quite empty. It would be ideal if, over a long period of time, it were possible to use the can at the end of its life in exactly the same way as when it is fresh from the factory.
If the substance has already solidified in the stem, it is also possible that when the valve is subsequently operated a number of times, solidified material will also pass into the valve, so that the latter itself will leak. Even if the removable part of the operating device were to be cleaned, the leaking valve could in the meantime have entirely or to a substantial extent destroyed the pressure in the can.