Fluid sprinkling – spraying – and diffusing – Combining of separately supplied fluids – And valving means controlling flow for combining
Reexamination Certificate
2001-10-17
2003-03-04
Yuen, Henry C. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Combining of separately supplied fluids
And valving means controlling flow for combining
C239S414000, C239S432000, C239S527000, C239S600000, C222S137000, C222S145600
Reexamination Certificate
active
06527203
ABSTRACT:
This invention relates generally to a dispensing apparatus for fluid products and more particularly, to a hand held gun which mixes and dispenses two fluid components.
The invention is particularly applicable and will be described with specific reference to a hand held dispensing gun for dispensing a two-component polyurethane foam. However, the invention in its broader application is not limited to polyurethane foams but has application to mixing and dispensing multi-component chemicals such as polyvinyls, paints, etc.
BACKGROUND
This invention is particularly suited for in situ applications of liquid chemicals mixed and dispensed as a spray or a foam and more specifically, to in situ application of polyurethane foam or froth. In situ applications for polyurethane foam have continued to increase in recent years extending the application of polyurethane foam beyond its traditional uses in the packaging, insulation and molding fields. For example, polyurethane foam is being used with increasing frequency as a sealant in the building trades for sealing spaces between windows and door frames and the like and as an adhesive for gluing flooring, roof tiles, and the like.
Polyurethane foam for in situ applications is typically supplied as a “one-component”froth foam or a “two-component” froth foam in portable containers hand carried and dispensed by the operator through either a valve or a gun. However, the chemical reactions producing the polyurethane froth foam in a “one-component” polyurethane foam is significantly different than the chemical reactions producing a polyurethane froth foam in a “two-component” polyurethane foam. Because the reactions are different, the dispensing of the chemicals for a two-component polyurethane foam involves different and additional concepts and concerns than that present in the dispensing apparatus for a “one-component”polyurethane froth foam.
A “one-component” foam generally means that both the resin and the isocyanate used in the foam formulation are supplied in a single pressurized container and dispensed from the container through a valve or a gun attached to the container. When the chemicals leave the valve, a reaction with moisture in the air produces a polyurethane froth or foam. Thus, the design concerns related to an apparatus for dispensing one-component polyurethane foam essentially concerns the operating characteristics of how the one-component polyurethane foam is throttled or metered from the pressurized container. Reference, for example, can be had to U.S. Pat. No. 5,887,756 to Brown, issued Mar. 30, 1999 and U.S. Pat. No. 5,645,199 to Schnitzler, issued Jul. 8, 1997. While one-component guns can variably meter the polyurethane froth, they are typically used in caulk/glue applications where an adhesive or caulk bead is determined by the nozzle configuration. Post drip is a major concern in such applications as well as the dispensing gun not clogging because of reaction of the one component formulation with air (moisture) within the gun. To address or at least partially address such problems, a needle valve seat is typically applied as close to the dispensing point by a metering rod arrangement which can be pulled back for cleaning. While metering can occur at the needle valve seat, the seat is primarily for shut-off to prevent post drip, and depending on gun dimensioning, metering may principally occur at the gun opening.
In contrast, a “two-component” froth foam means that one principal foam component is supplied in one pressurized container, typically the “A” container (i.e., polymeric isocyanate, fluorocarbons, etc.) while the other principal foam component is supplied in a second pressurized container, typically the “B” container (i.e., polyols, catalysts, flame retardants, fluorocarbons, etc.) Examples of two-component dispensing guns in commercial use today may be found in assignee's U.S. Pat. No. 5,429,308, to Brown, issued Jul. 4, 1995 and U.S. Pat. No. 5,242,115 to Brown, issued Sep.7, 1993. Additional commercial applications include U.S. Pat. No. 5,462,204 to Finn, issued Oct. 31, 1995; U.S. Pat. No.5,129,581 to Braun et al., issued Jul. 14, 1992; and, U.S. Pat. No. 4,925,107 to Brown, issued May 15, 1990. These guns are improvements over early two-component dispensing gun designs such as shown in U.S. Pat. No. 2,890,836 to Gusmer et al., issued Jun. 16, 1959; United States Pat. No. 3,559,890 to Brooks, issued Feb. 2, 1971; and, U.S. Pat. No. 3,784,110 to Brooks, issued Jan. 8, 1974.
In a two-component polyurethane foam, the “A” and “B” components form the foam or froth when they are mixed in the gun. Of course, chemical reactions with moisture in the air will also occur with a two-component polyurethane foam after dispensing, but the principal reaction forming the polyurethane foam occurs when the “A” and “B” components are mixed or contact one another in the dispensing gun. The dispensing apparatus for a two-component polyurethane foam application has to thus address not only the metering design concerns present in a one-component dispensing apparatus, but also the mixing requirements of a two-component polyurethane foam.
Further, a “frothing” characteristic of the foam (foam assumes consistency resembling shaving cream) is enhanced by the fluorocarbon (or similar) component, which is present in the “A” and “B” components. This fluorocarbon component is a compressed gas which exits in its liquid state under pressure and changes to it gaseous state when the liquid is dispensed into a lower pressure ambient environment, such as when the liquid components exit the gun and enter the nozzle.
While polyurethane foam is well known, the formulation varies considerably depending on application. In particular, while the polyols and isocyanates are typically kept separate in the “B” and “A” containers, other chemicals in the formulation may be placed in either container with the result that the weight or viscosity of the liquids in each container varies as well as the ratios at which the “A” and “B” components are to be mixed. In the dispensing gun applications which relate to this invention, the “A” and “B” formulations are such that the mixing ratios are generally kept equal so that the “A” and “B” containers are the same size. However, the weight, more importantly the viscosity, of the liquids in the containers invariably vary from one another. To adjust for viscosity variation between “A”and “B” chemical formulations, the “A” and “B” containers are charged (typically with an inert gas) at different pressures to achieve equal flow rates. The metering valves in a two-component gun, therefore, have to meter different liquids at different pressures at a precise ratio under varying flow rates. For this reason (among others), some dispensing guns have a design where each metering rod/valve is separately adjustable against a separate spring to compensate not only for ratio variations in different formulations but also viscosity variations between the components. The typical two-component dispensing gun in use today can be viewed as two separate one-component dispensing guns in a common housing discharging their components into a mixing chamber or nozzle. In practice, assignee has determined that invariably the gun operator adjusts the ratio settings to improve gun “performance” with the expected poor result. To counteract this adverse result, the ratio adjustment then has to be “hidden” within the gun, or the design has to be such that the ratio setting is “fixed” in the gun for specific formulations. The gun cost is increased in either event and “fixing” the ratio setting to a specific formulation prevents interchangeability of the dispensing gun.
Besides the ratio control which distinguishes two-component dispensing guns from one-component dispensing guns, a concern which affects all two-component gun designs (not present in one-component dispensing guns) is known in the trade as “cross-over”. Generally, “cross-over” means that one of the components of the foam (“A” or “B”) has crossed over into the dispensing mechanism in th
Hurray Paul Gregory
Starr Cris Damon
Nguyen Dinh Q.
Yuen Henry C.
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