Valves With Reduced Grommet Height

Abstract

The invention concerns an improvement to the design of a tilting/gun valve, more particularly regarding the problem of sticking/blocking. The valve comprises a cup (5), a stem (10) with an enlarged circular base (21) end extending perpendicularly and, therebetween, a grommet (22) made of an elastomer polymer. The grommet (22) is provided with a flat lower surface extending essentially on all the flat upper surface of the enlarged base of the stem to secure the sealing effect. The grommet (22) height H below the cup is less than 4 mm.

Description

The present invention concerns a design improvement to a tilting/gun valve, more particularly regarding the problem of sticking/blocking.

Generally the tilting valve will be used for dispensing moisture sensitive products such as one or two component polyurethane (PU) foam system, adhesives, sealants, etc or non moisture sensitive products such as tooth paste contained in a pressurized can or vessel. The product may have a high viscosity or a low viscosity.

The type of tilting/gun valves relevant for the present invention is used for more than 25 years in order to dispense the content of an aerosol can.

A typical tilting valve is made of a cup, a stem with a base and a gasket/seal called the grommet and made of an elastomer polymer.

This elastomer polymer is a hydrophobic or hydrophylic, thermoplastic or non thermoplastic elastomer polymer.

By tilting the hollow stem, the grommet will no more be in a sealing configuration and the valve therefore opens and delivers the vessel's content in an easily controllable way.

Examples of elastomer polymers suitable for a grommet are styrene-butadiene, butylene-styrene, silicone rubbers, isopropyl ether (Kraton, Shell), chlorinated polyethylene (Tyrin, Dupont De Nemours), epichlorhydrin homopolymers or copolymer, ethylene propylene (Nordel, Dupont de Nemours), fluoroelastomers (Viton, Kalrez, Du pont de Nemours), alcryn MPR (chlorinated olefin interpolymer alloy), Santoprene and Trefsin (Advanced Elastomer Services, Exxon)

However it is known that water diffusion through the grommets made out of various type of rubber is responsible for the sticking/blocking of the tilting valve, when moisture reactive products such as OCF, 1 KPU (one component polyurethane) glues or sealants are stored in these type of container.

In order to solve the problem of moisture penetration into the prepolymer, it has now been found that a new design of the valve is particularly effective.

Despite the fact that the used grommet elastomers have or could have a hydrophylic character the sticking/stucking phenomena is not occurring with this new design.

According to the invention there is provided a tilting valve comprising a cup, a stem with an enlarged circular base end extending perpendicularly and, therebetween, a grommet made of an elastomer polymer wherein the grommet is provided with a flat inner surface extending essentially on all the flat upper surface of the enlarged base of the stem to secure the sealing effect.

It has further been found that choosing certain appropriate dimensions of the cup's hole, the stem bottom and grommet's base and height, particularly effective sealing can be achieved.

Without being bound by any interpretation, it has been postulated that in a grommet of the prior art an internal annular zone of reaction between the reactive component, for example MDI having diffused into the grommet from the inside, and the humidity coming from the outside, that is to say through the hole(s) in the central hollow stem. This will form a “hard jacket” which hinders the tilting of the stem.

A flat configuration according to the invention allows this hard jacket to be formed away from the stem shaft. Jacket formation at the outer part of the grommet is no longer a problem.

Also the grommet and stem sealing surface is increased and the contact surface between the reactive component and the grommet is reduced. By reducing the thickness of the grommet part beneath the cup, the creep of the valve is drastically reduced.

The invention will be better and further understood with reference to the attached drawings wherein

FIG. 1 illustrates a standard tilting/gun valve

FIG. 2 is a sectional view of an embodiment of a new design according to the invention.

FIG. 3 shows various other embodiments of a valve according to the invention

FIG. 4 shows sectional view of variants of the grommet.

FIG. 5 shows three possible shapes of the bottom of the stem for a valve according to the invention.

FIG. 1 illustrates in a sectional view an example of a traditional tilting/gun valve showing basically a cup 5, a stem 10 with a base 11 and a gasket/seal 12.

The inner gasket/seal 12, called the grommet is made of an elastomer polymer. This elastomer polymer is a hydrophobic or hydrophylic, thermoplastic or non thermoplastic elastomer polymer.

By tilting the hollow stem 10, the grommet will no more be in a sealing configuration and the content will have access to the hole 13 located at the bottom of the stem, above the base 12. The valve therefore opens and delivers the vessel's content in an easily controllable way.

This new design is illustrated in FIG. 2 wherein there is shown in elevation a sectional view of a valve according to the invention in closed and open position. The opening of the valve is by pushing the stem (gun type action, FIG. 2b) or by tilting the stem (FIG. 2c).

This improvement is resulting from a combination of the different shapes of stem 21, grommet 22 and cup, more particularly the relative diameters of the hole of the cup, the base of the grommet and the bottom of the stem.

Ocup's hole (=O1), Ogrommet base (=O2), and Ostem bottom (=O3) combined with a thin base section of the grommet (H) reducing the contact surface between the can's content and the grommet to a minimum as shown in the other embodiments of FIG. 3.

According to one embodiment of the invention, the design may be characterized by the following measurements or ratios:
Ratio Ocup's hole/Ostem bottom=Ratio no 1
Ratio Ogrommet base/Ostem bottom=Ratio no 2
Height in mm of the grommet part below the cup=H
The measurements on the valves are done on valves in pressureless condition.

A set of conditions as follows has indeed been defined in order to provide a particularly effective valve of the present invention.
Condition 1: 0 mm<H<4 mm and
either Condition 2: 0<Ratio 1×H<2.8
or Condition 3: 0 mm<Ratio 2×H<5

It is therefore highly desired that at least one of the above conditions 2 and 3 is also fulfilled.

The tilting valve of the invention has typical values for Ratio 1 of 0.60 and 1.20 for Ratio 2, where the typical values for the traditional valves ranges for Ratio 1 from 0.7 to 0.9 and 1.4 to 1.6 for Ratio 2.

Furthermore the calculated area of the grommet in contact with the product, for the usual size valves is advantageously between 150 and 250 mm2, but may be less than 150, even less than 100 mm², where for traditional tilting valves the contact area lies between 200 and 300 mm².

According to the invention the grommet and stem have therefore a flat design that is to say flat surfaces are provided at the lower end of the grommet and stem and such surface will substantially cooperate for sealing the content of the valve. Further examples are shown in FIG. 3.

Other designs are shown in FIG. 4a-c for the grommet and FIG. 5a-c. for the stem.

FIG. 5a shows a stem with a bottom circular disc having a slight curvature on the upper surface. Similarly, the outer circular parts of the discs of FIGS. 5b and 5c show an extension The grommets can have the same shape in the outer circular disc as shown in FIG. 4a, FIG. 4b and FIG. 4c. Any combination stem/grommet described above is possible.

According to another embodiment, there can be an insert of any kind of shape with a higher or lower hardness than the basic grommet material integrated in the bottom section of the grommet. When this kind of insert is placed in the bottom section of the grommet, the above mentioned conditions are not necessarily applicable and even the current grommet design can be used. This is illustrated in FIG. 6.

The grommet of the invention may further be treated with a chemical coating or may be coupled to a spring arrangement to compensate for possible inferior “snappy properties” of the grommet and thus the valve.

According to the invention, the coating treatment may be conducted either by spraying or immersion in the coating fluid or by plasma treatment. The coating may be reactive or non-reactive.

A significant improvement in overall properties of the valve according to this invention is noticed.

The aerosols or vessels according to the invention can be stored vertically, horizontally and may be shaken every day. It has been found that the valves designed and treated according to the invention are still working and no leakage, sticking or blocking of the valve is encountered even after 12 months at 45° C. and 90% RH (Relative Humidity).

Claims

1. A tilting/gun valve comprising a cup, a stem with an enlarged circular base end extending perpendicularly and, therebetween, a grommet made of an elastomer polymer wherein the grommet is provided with a flat inner surface extending essentially on all the flat upper surface of the enlarged base of the stem to secure the sealing effect wherein the grommet's height H of the inner surface is less than 4 mm.

2. A valve according to claim 1 wherein the height H is less than 3 mm.

3. A valve according to claim 1 wherein the height H is less than 2 mm.

4. A tilting/gun valve according to claim 1 wherein the mathematical product of the grommet's height H and the ratio of diameter of the cup hole/diameter of the stem bottom, is smaller than 2.8.

5. A valve according to claim 1 wherein the ratio is smaller than 2.

6. A tilting/gun valve according to claim 1 wherein the mathematical product of the grommet's height H and the ratio of diameter of the grommet base/diameter of the stem bottom, is smaller than 5.

7. A valve according to claim 6 wherein the ratio is smaller than 4.

8. A tilting/gun valve according to claim 1 wherein the elastomer polymer is a hydrophobic or hydrophylic, thermoplastic or non thermoplastic elastomer polymer.

9. A grommet made of an elastomer polymer for a tilting/gun valve provided, the grommet being provided with a flat lower surface able to extend essentially on all the flat upper surface of the enlarged base of a corresponding stem, the lower surface having a thickness of less than 4 mm, preferably less than 3 mm.