Dispensing – Plural sources – compartment – containers and/or spaced jacket – With discharge assistant for each source
Reexamination Certificate
1999-07-28
2001-04-24
Kaufman, Joseph A. (Department: 3754)
Dispensing
Plural sources, compartment, containers and/or spaced jacket
With discharge assistant for each source
C222S145500, C222S321200, C222S321400, C222S321700
Reexamination Certificate
active
06220483
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dispensing assembly for dispensing two liquid components, comprising an outer piston pump concentric with an inner piston pump for the components to be dispensed, with a common control part, which piston pumps are provided with resetting means and each comprise a piston chamber with a piston and an inlet and an outlet, which outlet can be placed in communication with an outflow opening, with the interposition of a non-return valve under pre-tension, and which inlet can be placed in communication with a source for component to be dispensed, with the interposition of a non-return valve, while the pistons of the piston pumps comprise a channel for conveying the liquid component in question to an outflow opening.
BACKGROUND OF THE INVENTION
Such dispensing assemblies with so-called double, concentric pumps are generally known in the prior art and are used for dispensing many kinds of liquid components from containers. Such liquid components are not particularly limited and vary from aqueous liquid components to paste-like materials.
Examples of components to be dispensed are, for example, adhesives with a hardener, paints with a hardener, cosmetic products with reactive components, detergents with reactive components etc.
The ratio between the quantities of the components to be dispensed can be set as desired by a suitable choice of the dimensions of the parts in question.
The outflow openings for the components in question can be in the form of individual outflow openings, but they can also be in the form of a common outflow opening, with the interposition of a mixing chamber section or otherwise.
All known dispensing assemblies have the major disadvantage that partial vacuum possibly occurring outside the outflow opening causes an inadequate seal to be obtained between the concentric inner and outer piston. This can occur, for example, in an aircraft. In that case, material may be sucked out of the outer piston chamber, through between the pistons, and consequently out of the container for the particular component which may be connected to the outlet of the outer piston chamber, and out of the outflow opening. This is, of course, undesirable. Constituents are in fact often dispensed with such dispensing assemblies in practice, which are sticky after drying or otherwise. When there is accidental outflow of such constituents, the subsequent functioning of the dispensing assembly may be seriously impeded, if not rendered impossible.
The control part used in the case of such dispensing assemblies is generally a push-button on the dispensing assembly, which push-button interacts with both pumps. It is undesirable for said button to be soiled with material for dispensing, since a user operates the dispensing assembly by pressing with a finger on the push-button.
Moreover, the entire assembly is often shut off by a sealing cap or sealing cover, which can also be undesirably soiled by the abovementioned escaping component.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a solution to the abovementioned problems, and to that end the invention is characterized in that the inner piston pump comprises an inner piston which has a small free stroke relative to the other parts of the assembly, in that a stationary stroke limiting part with a stop is present in the outer piston chamber of the outer piston pump, which stroke limiting part under friction can interact with a stop on the inner piston, in order to limit the movement distance thereof and permit the movement thereof only under friction, and in that the outer piston and the inner piston comprise carrier means which can interact in a sealing manner with each other and form an active non-return valve for the outlet of the outer piston chamber, all the above in such a way that when there is a resetting movement the outer piston can carry along the inner piston and seal the connection between the outer piston chamber and an outflow opening.
Owing to the small free stroke of the inner piston and the presence of the carrier means, an excellent seal is obtained between the outer piston and the inner piston, which ensures that no material can be sucked through between the pistons if a partial vacuum occurs. In other words, the non-return valve in the outlet of the outer piston chamber is formed by the carrier means mentioned earlier. Unlike many non-return valves used in the prior art, said non-return valve is an active non-return valve, and not a passive one. A partial vacuum outside the dispensing assembly, i.e. outside the outflow opening, also promotes the sealing action of said non-return valve. All the above will be explained in greater detail further on, in the description of the drawings.
In a special embodiment of the dispensing assembly according to the invention, the stationary stroke limiting part defines an annular intermediate piston chamber which by way of one or more narrow passages is in communication with the outer piston chamber, and the stop on the inner piston forms an intermediate piston in the intermediate piston chamber.
When the dispensing assembly is being used, the intermediate piston chamber will be filled through the narrow openings with component from the outer piston chamber, so that on movement of the inner piston a damping of the movement thereof will be obtained, which has a very advantageous influence on the operation of the entire dispensing assembly. This in fact means that when the assembly makes a dispensing stroke the active non-return valve formed by the carrier means is opened in a reliable manner.
In particular, the limiting part is formed by a bush fixed on the inner piston chamber and having on one end an inward directed collar which can interact with the intermediate piston, in which case by grooves and/or ribs on either the inside wall of the bush or the outside wall of the inner piston chamber, or both, one or more passages are formed, so that the intermediate piston chamber is in communication with the outer piston chamber. This advantageous embodiment will be explained in greater detail further on, in the description of the drawings.
In the case of many dispensing assemblies, in particular dispensing assemblies for components with relatively low viscosity, there is a so-called start-up problem, in other words, when the assembly is being used for the first time it takes some time before material can actually be dispensed, and the user has to press the dispensing assembly several times, sometimes even more than 25 times, before the components can be dispensed.
In order to solve this problem, according to the invention, at least the inner piston chamber is filled with a start-up agent prior to a first use of a dispensing assembly.
A start-up agent is also known as a primer and serves to ensure that the assembly can operate and dispense material already at the first service stroke. An example of a suitable primer is glycerol. The viscosity of the primer is preferably slightly higher than that of the material to be pumped. Of course, the primer ultimately to be used will depend on the material to be dispensed. The primer is preferably inert relative to the material to be dispensed.
The carrier means on the inner piston and the outer piston are advantageously designed in the form of sealing collars on said pistons, which collars are bevelled in the same direction and fit into each other. Using suitably bevelled sealing collars on the pistons ensures that when there is a resetting movement of the outer piston, a very good seal supported by external partial vacuum is obtained between the two pistons.
The friction action between the stroke limiting part and the inner piston can be carried out in many different ways. For instance, the mutual dimensions of the parts in question can be selected in such a way that friction is obtained. However, it is advantageous if the outside wall of the inner piston is provided locally with friction ribs which extend in the intended direction of movement of the inner piston, but are sit
Airspray International B.V.
Hoffman & Baron LLP
Kaufman Joseph A.
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