Dispensing – Plural sources – compartment – containers and/or spaced jacket – With common discharge
Reexamination Certificate
1999-02-10
2001-09-04
Scherbel, David A. (Department: 3752)
Dispensing
Plural sources, compartment, containers and/or spaced jacket
With common discharge
C222S145500, C222S146500, C222S149000, C222S504000, C239S134000, C239S117000, C239S423000, C239S433000
Reexamination Certificate
active
06283329
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus for dispensing and applying a multi-component foamable fluid plastic material, including polyurethane foams.
DESCRIPTION OF THE PRIOR ART
Foam application apparatus are commercially available that apply multi-component foamable fluid plastic materials, preferably polyurethanes. The standard reactant fluids comprise a plastic material fluid component and an isocyanate fluid component bearing comparable viscosities and used in comparable ratios.
Typically, foam application apparatus include a cylindrical mixing chamber having separate orifi or fluid inlet openings for each reactant component and an axial passage transverse to the direction of the inlet passages for allowing the mixed or reacted fluid to exit the mixing chamber. The mixing chamber is typically mounted in a support body structure. The dimensional tolerance between the mixing chamber and valve body is made sufficiently close so that the reactant fluids cannot flow therebetween. Standard reactant fluids are sufficiently viscous to not normally flow between the mixing chamber and valve body.
A cylindrical rod or valve needle having an external diameter nearly the same as the internal diameter of the cylindrical mixing chamber moves forwardly and rearwardly in the mixing chamber. In the forward position, the valve needles close off the fluid inlet openings to prevent any fluid from entering the mixing chamber. In the rearward position, the valve needle is retracted under hydraulic pressure to expose the inlet openings to permit their respective fluids to flow in the mixing chamber and impingement mix therein. When enough reacted fluid has been dispensed, the valve needle moves to its forward position to once again close the inlet passages and prevent reactant fluid flow into and mixing in the mixing chamber.
Many apparatus of this type are well known in the art, including U.S. Pat. No. 4,377,256 to Commette, et al., and U.S. Pat. No. 5,339,991 to Synder. One common problem that is disclosed in U.S Pat. No. 5,339,991 is that conventional foam applications commonly seize up after a few thousand shots requiring cleaning of the valve components and mixing chamber before reuse.
Another problem associated with the prior art apparatus is that the foam application gun is not heated. This requires that the combination of heat energy dissipated from the heated reactant fluids and the heat given off by the reaction of the reactant fluids in the mixing chamber are used to heat the gun. One drawback with this is that the first several shots exiting the dispensing apparatus are wasted because the apparatus is not at a suitable temperature for carrying out the foaming reaction. Thus, heat is removed from the reactant fluids and the initial reacted fluids exiting the mixing chamber are not at a sufficiently high temperature for proper reaction.
Another problem has recently developed with respect to foam application guns. Recently developed chemistry using non-standard reactant fluids may also be used to make the plastic foam. These new reactant fluids use no or low isocyanates as one reactant fluid and a resin component as another reactant fluid. Some of these non-standard reactant fluids are not as viscous as the standard reactant fluids and may tend to seep between the mixing chamber and valve body. Furthermore, the ratios of reactant fluids in this type of system are not necessarily comparable.
SUMMARY OF THE INVENTION AND ADVANTAGES
According to the invention, an apparatus is provided for applying a multi-component foamable fluid plastic material, the material including at least two reactant fluids configured to form a foam when heated and mixed. The apparatus includes a heater disposed on and configured to heat a support body structure of an applicator gun. The apparatus also includes a mixing chamber supported in the support body structure and configured to receive pre-heated reactant fluids for mixing through two mixing chamber fluid inlet openings. The mixing chamber comprises an axial passage disposed generally transverse to the fluid inlet openings and configured to allow reactant fluids to exit the mixing chamber through an axial outer end of the axial passage. Two mixing chamber fluid inlets are disposed in the support body structure in fluid communication with the mixing chamber and are configured to direct the respective reactant fluids into the mixing chamber through the respective mixing chamber fluid inlet openings. An elongated valve needle is supported in the mixing chamber for reciprocal longitudinal movement between forward closed and a rearward open positions in the mixing chamber. The valve needle is configured to expose the fluid inlet openings when retracted to the rearward open position to permit the reactant fluids to flow into the mixing chamber from the respective inlet openings and impingement mix therein. The needle is configured to close off the fluid inlet openings and dispense the mixed fluids from the mixing chamber through the axial passage while being advanced to the forward closed position. The heater prevents the support body structure from drawing heat energy from initial quantities of the pre-heated reactant fluids, which would cool the initial quantities of the fluids, preventing them from reacting properly in the mixing chamber.
According to another aspect of the invention, the heater includes two heating elements; each element being disposed adjacent one of the mixing chamber fluid inlets. This allows the temperature of portions of the support body structure adjacent the mixing chamber fluid inlets to be controlled separately.
According to another aspect of the invention, the apparatus includes a gun temperature feedback control system including a temperature sensor configured to monitor support body structure temperature and a controller configured to control heater temperature based on temperature sensor inputs. The control system may be configured to control the temperatures of the two heating elements separately.
According to another aspect of the invention, the valve needle includes a helical groove configured to purge the mixing chamber of unreacted and reacted fluids by scraping the interior surface of the mixing chamber.
According to another aspect of the invention, the valve needle includes a pair of annular grooves disposed such that one of the annular grooves is positioned forward of the mixing chamber fluid inlet openings when the valve needle is in the closed position and the second of the annular grooves is positioned rearward of the mixing chamber fluid inlet openings when the valve needle is in the closed position. The annular grooves are configured to prevent reactant fluids from passing the annular grooves by allowing any residual reactant fluid to collect in the annular grooves and react thus creating a seal between the valve needle and an interior wall of the mixing chamber.
According to another aspect of the invention, the mixing chamber is defined by a sleeve supported in a sleeve receptacle in the support body structure. The fluid inlet openings are disposed in a wall of the sleeve. The mixing chamber fluid inlets open through respective flat portions of an interior surface of the sleeve receptacle. The fluid inlet openings are disposed in a flat portions of an exterior surface of the sleeve wall. The flat portions are disposed parallel to the respective flat portions of the interior surface of the sleeve receptacle. A seal is disposed around each mixing chamber fluid inlet and between the respective flat portions of the interior surface of the sleeve receptacle and the exterior surface of the sleeve wall to seal the interior surface of the sleeve receptacle to the exterior surface of the sleeve wall so that reactant fluids cannot escape the mixing chamber fluid inlet between those two surfaces.
According to another aspect of the invention, the apparatus comprises a mix head supported at an axial outer end of the support body structure. The sleeve receptacle is disposed in the mix head.
According to
Bezaire Leon J.
Leonard, II Jerry LaVern
Jesco Products Company, Inc.
Kim Christopher S.
Reising Ethington, Barnes, Kisselle, Learman & McCulloch, P.C.
Scherbel David A.
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