Fluent material handling – with receiver or receiver coacting mea – With conveying means to supply successive receivers
Reexamination Certificate
1999-11-18
2001-11-06
Douglas, Steven O. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
With conveying means to supply successive receivers
C141S009000, C141S100000, C141S313000, C222S146600
Reexamination Certificate
active
06311740
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dispensing system, components of a dispensing system, and methods of manufacturing, operating and servicing a dispensing system and components thereof. A preferred dispensing system embodiment of the present invention, and related components thereof, pertain to a dispensing system which brings into contact two different fluid products within a chamber, and particularly two different liquids which, when mixed, react to produce a foam product or the like.
BACKGROUND OF THE INVENTION
To help appreciate the significant advances made by the present invention in the field of dispensing and, in particular, the field of foam dispensing, provided below is a discussion of the prior art efforts to provide a dispensing system for use in dispensing a foam such as a polyurethane foam.
FIG. 1
of the present invention schematically illustrates the general set up of a dispensing system for mixing and dispensing two liquids (liquids A and B) such as organic resins and polyisocyanates which react to form a polyurethane foam. As shown in
FIG. 1
, a chemical “A” supply means
1100
is provided for feeding to the dispensing apparatus
1102
a first chemical such as a liquid organic resin, and a chemical “B” supply means
1104
is provided for feeding to dispensing apparatus
1102
a second chemical such as a polyisocyanate. The organic resin and polyisocyanate are mixed within a mixing chamber of dispensing apparatus
1102
to form polyurethane foam which is discharged from dispensing apparatus
1102
.
One particular problem with the dispensing of polyurethane foam of this type is that the organic resin and polyisocyanate react rapidly, and can accumulate over the external and internal surfaces of the dispensing apparatus. Under some mixes, an expansion of about 200 times in volume takes place and the mixed chemicals become very adhesive in nature. Thus, preventing the foam mix from reaching undesirable areas such as the chemical introduction ports and the discharge outlet is difficult. Also, once the foam material reaches a location and cures, it is difficult to remove the residue left as the residue strongly adheres to the underlying surface. A build up of foam residue can result in, for example, the binding, sticking or locking up of components, as well as degradation of the contacting surfaces, particularly when, a plastic, cold flow material such as TEFLON® material is used in the mixing chamber region. The sticking of components due to the build up of foam precursor material also requires an increase in the driving motor output used to reciprocate purge or valve rods associated with many prior art designs. Accordingly, in anticipation of this inevitable build up and increase in motive requirements such dispensers is sized to accommodate this build up in motive force requirement.
The inevitable build up of cured foam in the dispenser over time also results in partial or complete blockage of the chemical inlet ports and passageways which can lead to a change in flow characteristics with respect to chemicals A and B and therefore a change in the chemical A and B input ratio. Even a minor obstruction in an inlet port passageway prevents the output of a precise and consistent amount of foam over time, which, among other problems, presents a significant quality control problem with respect to the resultant foam product. That is, the poor ratio associated with prior art dispensers having chemical inlet or inlets at least partially blocked with cured foam build-up leads to an off-ratio mix and a resultant product not having high quality characteristics. Also, as the amount of build up, and thus the degree of obstruction, varies over time, there is a corresponding variation in the amount of chemical precursor introduced into the mixing chamber and outputted from the dispenser. This, coupled with the change in foam development brought about by the off-ratio foam introduction, leads to significant changes in the amount of foam produced from output to output over time and the aforementioned quality control problems.
The partial or complete blockage of the chemical inlet ports and binding or sticking of components in the dispenser are just some examples of the dispenser's performance being degraded by the build up of foam residue on a surface thereof. Actually, starting from the time of first use, the dispensing operation tends to deteriorate such that frequent dispensing apparatus servicing (e.g., disassembly and cleaning or replacement) is required. For high use operators of the prior art foam dispensers, servicing often takes place on a daily basis, while for even less high volume producers, weekly servicing is not uncommon. Of course, the down time associated with such servicing requirements, as well as the costs associated with such servicing is particularly problematic in the industry. Prior to servicing, however, the inevitable deterioration in operation typically results in a substantial decrease in foam output of the gun for reasons such as those outlined above. A not atypical scenario involves a dispenser dropping from a first cycle output flow rate of 8 to 10 lb./min. mixed foam precursor down to 4 or 5 lb./min. often within a relatively short time frame (e.g., less than 20,000 cycles of use). After running at this reduced capacity, the tenacious nature of the mixed foam precursor material inevitably leads to a complete locking up of the gun or a dispensing ratio that is totally unacceptable.
The prior art, in an effort to prolong the time between servicing, has relied upon complicated systems in an effort to maintain the optimum chemical A and chemical B input ratio despite the inevitable partial and often unequal obstruction of the inlet ports for the chemicals leading into the mixing chamber. For example, complicated pumping and sensing systems have been developed to vary the pumping characteristics of one or the other chemical supply pumps to account for a greater degree of blockage in one port versus the other. In addition to the high costs associated with these complicated prior art pumping and associated control systems, the added complexity can lead to increased chances of a breakdown as well as more difficult operation and higher skilled personnel to monitor the dispensing system. Moreover, this additional equipment can do nothing to help in the internal build up of foam in the dispenser which causes the increased sticking in reciprocating components and the eventual lock up of the dispenser.
FIGS. 2 and 4
illustrate two different prior art dispensing apparatuses which are representative of those being used in this field. The structure and operation of these systems are described below and in further detail in the detailed disclosure portion of the present application to help illustrate the significant advances made by the present invention over the prior art. These dispensing apparatuses are disclosed in U.S. Pat. Nos. 5,211,311 and 3,945,569, respectively, and both of these patents are incorporated herein by reference. Also, reference is made to U.S. Pat. Nos. 4,568,003; 4,469,251; 4,898,327; and 5,090,814 as further illustrating the state of the art and these patents are also incorporated herein by reference. The embodiment shown in
FIGS. 2 and 3
is representative of a dispensing apparatus which does not involve the use of a solvent, features a purge rod (as opposed to a valving rod discussed below for the
FIG. 4
embodiment) and features valves positioned to allow or disallow the flow of fluid to the mixing chamber through the mixing chamber inlet ports. Accordingly, the
FIG. 1
schematic shows the optional inclusion of solvent supply means
1106
by a dashed line representation.
The
FIG. 4
system is representative of a dispensing apparatus which uses a reciprocating valving rod to allow for and to disallow the introduction of the chemical precursors into the mixing chamber of the dispensing apparatus. In addition, a pool of solvent is provided through which an intermediate portion of the valving rod reciproca
Hanna Todd A.
Piucci Vincent A.
Sperry Charles A.
Carpenter Co.
Douglas Steven O.
Smith , Gambrell & Russell, LLP
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