Minimal wear dispensing valve

A minimal wear valve assembly which includes a fluid reservoir having an inlet port and an outlet port for passage of the fluid therethrough. The reservoir defines a valve seat about and downstream of the outlet port. The assembly includes a valve having a first substantially non-deformable valve surface. The valve is movable with respect to the valve seat from an open condition which permits flow of the fluid through the outlet port to a closed condition which prevents flow of the fluid through the outlet port. The valve supports a sealing member for movement with the valve. The sealing member has greater compressibility than the first valve surface and provides a seal between the first valve surface and the valve seat upon movement of the valve to the closed condition.

FIELD OF THE INVENTION 
The present invention relates generally to the field of valve assemblies. 
More specifically, the present invention relates to a valve assembly 
having improved sealing characteristics. 
BACKGROUND OF THE INVENTION 
Valve assemblies are well known for their ability to regulate fluid flow 
through inlet and/or exhaust openings. One such valve is a poppet valve. 
Poppet valves are typically made from heat-resistant steel and include a 
circular head or valve. The valve includes a conical face which registers 
with a corresponding valve seat bounding the opening. In some cases the 
head may be disk shaped and seat over a port opening. In other cases, such 
as with a ball-poppet valve, the head may be a spherical member which 
closes the valve when positioned against an opening having a conical or 
tapering surface. A guided stem, by which the valve is lifted from its 
seated position, is movable under the urging of an actuator. When the 
conical face of the valve rests on the valve seat the fluid is sealed from 
flowing through the valve. 
As the materials which form the poppet valve assembly are substantially 
incompressible, early failure of the valve assembly can result when the 
valve is employed to dispense fluids containing high concentrations of 
substantially incompressible and abrasive inorganic additives or fillers. 
Some fillers, such as Al.sub.2 O.sub.3, can cause frictional wear of the 
valve when flowing between the valve and the seat. Hertz-type stresses of 
the mating surfaces, which can cause flaking or shearing at the surfaces, 
are also known to occur when these solid fillers are pinched between a 
ball-poppet and the valve seat as the ball-poppet seals against the seat. 
As the ball-poppet reaches the final closed position there can be relative 
movement between a particle of the solid filler and the mating surfaces 
which can gouge the surface, creating a pathway between the mating 
surfaces through which the fluid may leak. 
Furthermore, these solid fillers can become trapped between the mating 
surfaces as the poppet closes against the seat. Because the mating 
surfaces and the abrasive filler are all made from substantially 
incompressible materials, a particle of the filler becoming trapped 
between the mating surfaces can cause localized stress concentrations on 
the mating surfaces. Such localized stress concentrations can result in 
surface imperfections, distortions, and other irregularities, such as 
pitting or abrasive wear, which prevent sealing engagement between the 
valve and the seat, and thereby cause valve failure as the fluid will then 
have a pathway between the mating surfaces. 
Some fillers may be crushed between the mating surfaces which can result in 
degradation of the material being dispensed. Some adhesives include 
fillers to provide a desired thermal or electrical characteristic to the 
adhesive. For example, glass spheres are within some dielectric adhesives 
to provide the desired insulative characteristics. These glass spheres can 
be about 1/5000 of an inch in diameter. These glass spheres could be 
crushed if trapped between two incompressible mating surfaces, which could 
then cause electrical shorts through the material and result in quality 
control problems for the user. 
Currently, valves employed to dispense abrasive fluids employ poppet valves 
which seat a metal valve against a metal seat. Valve failure has been 
witnessed in these valves after 50,000 to 60,000 cycles of opening and 
closing. It would therefore be desirable to provide a valve assembly which 
provides suitable sealing characteristics between the valve and the valve 
seat and which minimizes the risk of failure when dispensing abrasive 
products. 
SUMMARY OF THE INVENTION 
The present invention provides a valve assembly having improved resistance 
to failure in connection with the dispensing of fluids containing abrasive 
fillers. 
The present invention also provides a valve assembly that minimizes damage 
to the seating elements of the assembly when the valve closes to terminate 
fluid flow through the valve. 
The present invention further provides a valve assembly that eliminates 
relative sliding between the seating elements of the assembly and any 
particles of abrasive filler material trapped therebetween as the valve 
seals against the valve seat. 
The present invention still further provides a valve assembly that enhances 
quality control of the dispensed fluid by not adversely affecting the 
filler dispersed within the fluid. 
In this regard, the present invention provides a minimal wear valve 
assembly which includes a fluid reservoir having an inlet port and an 
outlet port for passage of the fluid therethrough. The reservoir defines a 
valve seat about and downstream of the outlet port. The assembly includes 
a valve having a first substantially non-deformable valve surface. The 
valve is movable with respect to the valve seat from an open condition 
which permits flow of the fluid through the outlet port to a closed 
condition which prevents flow of the fluid through the outlet port. The 
valve supports a sealing member for movement with the valve. The sealing 
member has greater compressibility than the first valve surface and 
provides a seal between the first valve surface and the valve seat upon 
movement of the valve to the closed condition. The compressibility of the 
sealing member allows it to form around any trapped filler particles, 
without embedding the particle in the sealing member, while still 
maintaining the seal between the mating surfaces to prevent leakage of the 
valve. 
And in a more specific aspect of the present invention, there is provided a 
minimal wear valve assembly for dispensing abrasive fluids. The valve 
assembly includes a fluid reservoir having an inlet port, an outlet port, 
an actuator port opposite the outlet port, and a valve seat positioned 
about and downstream from the outlet port. The fluid reservoir is formed 
from a substantially non-deformable material. The valve assembly also 
includes a valve having a having a substantially non-deformable first 
valve surface. The valve is movable with respect to the valve seat from an 
open condition permitting flow of the fluid through the outlet port to a 
closed condition preventing flow of the fluid through the outlet port. The 
valve is formed from a substantially non-deformable material. A sealing 
member, which has a greater compressibility than the first valve surface, 
is supported by the valve and provides a seal between the first valve 
surface and the valve seat upon movement of the valve to the closed 
condition. A valve stem extends from the valve into the fluid reservoir, 
adjacent the inlet port, and extends through the actuator port. The valve 
stem is formed of a substantially incompressible material. The valve 
assembly includes an elastomeric diaphragm sealing the actuator port. The 
diaphragm includes a diaphragm aperture. The valve stem extends through 
the diaphragm aperture and is in sealing engagement therewith. 
The present invention will be more readily appreciated in a reading of the 
"Detailed Description of the Invention" with reference to the drawings.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a valve assembly 10 of the present invention. Assembly 10 
includes a fluid reservoir 12 having an inlet port 14 and an outlet port 
16. A valve seat 18 is located downstream from outlet port 16. Outlet port 
16 may be perimetrically bounded by valve seat 18. Outlet port 16 opens to 
a downstream housing 13 which is secured in fluid communication with 
reservoir 12. As is well known in the dispensing art, downstream housing 
13 may be attached to or form part of a fluid dispenser for dispensing 
fluid contained in reservoir 12. Fluid reservoir 12 and downstream housing 
13 are typically formed of a rigid material such as metal or a structural 
polymeric material. 
Assembly 10 also includes a valve 20 interposed within port 16. Valve 20 
includes a disk-like member 21 and a depending stem 36. Disk member 21, 
which is designed to close port 16, is formed of a rigid incompressible 
material such as metal or a structural polymeric material. Disk member 21 
includes a first valve surface 22 in registry with outlet port 16. 
With additional reference to FIGS. 2a-c, valve 20 includes an annular 
channel 24 formed therein which opens onto first valve surface 22. The 
geometry of channel 24 may vary provided it serves to hold a sealing 
member for proper sealing of outlet port 16. Channel 24 may be formed 
having a trapezoidal cross section so as to include radially-opposed walls 
26, 28 tapering towards each other from a channel base 30 towards a 
channel opening 32. Channel 24 supports therein a compressible sealing 
member, such as O-ring 34 as shown, for sealing engagement with valve seat 
18 when valve 20 is positioned in the closed condition. O-ring 34 may be 
formed of Buna N rubber although other compressible elastomeric or 
resilient materials are contemplated as being within the scope of the 
present invention. The material selected to form the compressible sealing 
member should be elastic to deform about, without embedding, any filler 
particles that the member may trap against the valve seat, and strong to 
sealingly engage the valve seat under pressure. O-ring 34 has a 
cross-sectional diameter that is greater than the radially-transverse 
dimension of channel opening 32 and therefore is compressed when inserted 
into channel 24. Once inserted into channel 24, however, O-ring 34 may be 
maintained therein by an interference fit, although other means such as 
adhesion or mechanical attachment are also contemplated. 
Valve stem 36 extends from first valve surface 22. Valve stem 36 is 
ordinarily an elongate generally cylindrical member. As seen in FIG. 1, 
valve stem 36 extends from disk member 21, through reservoir 12 adjacent 
inlet port 14, and through an actuator port 38 opposite outlet port 16. 
Valve stem 36 includes a first stem portion 40 which is formed to be 
contiguous with valve 20 and an interconnectable second stem portion 42. 
Second stem portion 42 extends through diaphragm 44 to present an 
actuation interface surface 46 which may be acted upon by an actuator (not 
shown). While valve stem 36 is shown in FIGS. 1 and 2 to be a two-piece 
construction, it is contemplated by the present invention that valve stem 
36 may be a one-piece design as well. 
First stem portion 40 and second stem portion 42 matingly engage each other 
to form a unitary incompressible valve stem 36 to simplify manufacture of 
valve assembly 10. First stem portion 40 includes a threaded male portion 
52 distal from first valve surface 22. Threaded male portion 52 threads 
into the elongate threaded female portion 54 defined by second stem 
portion 42, as shown in FIG. 1. A tool such as a screwdriver may engage an 
elongate slot 48 to assist in the threading of first stem portion 40 into 
second stem portion 42. 
Actuator port 38 supports a diaphragm 44 thereacross which provides for 
actuated movement of valve 20. Diaphragm 44 and second stem portion 42 
seal actuator port 38 so as to prevent fluid flow therethrough. Diaphragm 
44 includes a tapered circumferential edge 56 adhered to tapered annular 
rim 58 and an interior annular rim 60 which also defines an interior 
aperture 62 through which second stem portion 42 extends. Diaphragm 44 is 
typically formed of an elastomeric material which enables interior annular 
rim 60 to deflect with stem 36 when urged to open or close valve 20. 
The valve of the present invention may be operated in the following manner. 
Fluid reservoir 12, being attached at inlet port 14 in fluid communication 
with a fluid source, retains the fluid at a higher internal pressure than 
exists in downstream housing 13. While the internal pressure in reservoir 
12 may range up to about 250 pounds per square inch (psi), the internal 
pressure ranges useful herein may be varied to accommodate different 
materials and their particular viscosity, rheology, and thixotropy. An 
actuator assembly, pushing on actuator interface surface 46, forces stem 
36 and valve 20 into the open condition away from valve seat 18. The 
higher internal pressure of reservoir 12 thereby dispenses the fluid 
through the open outlet port into housing 13. The fluid is dispensed until 
the actuator assembly retracts from engagement with surface 46, whereby 
the internal pressure of reservoir 12, acting against diaphragm 44, 
assists in moving diaphragm 44 in a direction away from outlet port 16. 
This motion of diaphragm 44 also carries stem 36 and valve 20 so as to 
re-engage valve 20 on valve seat 18 to define a closed condition, whereby 
fluid dispensement ceases. The O-ring 34 carried by disk member 21 forms a 
resilient liquid-tight seal against valve seat 18. 
The compressibility of O-ring 34 allows for it to deform about any 
substantially incompressible solid materials embodied by the fluid being 
dispensed. Should a particle, for example, of an abrasive filler, become 
entrapped between O-ring 34 and valve seat 18 when valve 20 is in the 
closed condition, O-ring 34 is able to deform about the filler particle 
and maintain a sealing engagement. The sealing member should prevent both 
excessive Hertz-type stress formation in the components of the valve 
assembly and degradation of the material properties of the fluid being 
dispensed resulting from particles of filler material being trapped 
between the mating surfaces. 
Moreover, as the sealing force exerted by O-ring 34 is normal to valve seat 
18, there is no sliding engagement between the mating surfaces which could 
cause a trapped filler particle to damage the sealing surfaces of either 
valve 20 or valve seat 18. The present invention therefore provides a 
valve well suited to dispensing fluids having high concentrations of 
inorganic fillers, such as Al.sub.2 O.sub.3. An example of such a fluid is 
a polymerized silicone available commercially from Loctite Corporation, 
Rocky Hill, Conn. under the name "LOCTITE PRODUCT 5404". The present 
invention also provides improved quality control of dispensed products 
such as thermal adhesives having thermally-conductive filler particles or 
dielectric adhesives having spacer materials formed of glass spheres of 
about 1/5000 of an inch in diameter. Furthermore, the present invention 
also provides a valve capable of dispensing fluids having a wide range of 
viscosities, under suitable pressures for the chosen material, and 
typically under pressures ranging up to 250 psi or even greater. Whereas 
conventional poppet valves dispensing abrasive fluids have typically 
failed after about 50,000 to 60,000 cycles, preliminary tests of the 
present invention were terminated after about 998,000 cycles without any 
observed failure. 
FIG. 3 shows an alternate embodiment of the present invention wherein valve 
20' supports a compressible, i.e. deformable, and/or resilient gasket 70 
as the sealing member on a first valve surface 22' for sealing engagement 
with valve seat 18 of reservoir 12. Gasket 70 is an annular member having 
an interior annular aperture 74 through which first stem portion 40' 
extends. First stem portion 40' includes threaded male portion 52' which 
is designed to matingly engage a threaded female portion of a second stem 
portion (not shown) for securement to a diaphragm (also not shown) in a 
similar manner as shown for the embodiment of FIG. 1. 
With reference to FIG. 4a-c, first valve surface 22' desirably supports a 
projecting annular rib 76 positioned opposite valve seat 18. Gasket 70 
compresses about projecting annular rib 76 when valve 20' is moved to the 
closed condition with respect to valve seat 18 to provide increased seal 
integrity about outlet port 16. While gasket 70 is shown in FIG. 3 having 
an inner diameter smaller than the diameter of outlet port 16, the present 
invention also contemplates that gasket 70 may have an inner diameter 
equal to or larger than the diameter of outlet port 16. 
The gasket 70 functions in a manner similar to O-ring 34 of FIG. 1. The 
compressibility of gasket 70 allows deformation about any filler particles 
entrapped between gasket 70 and valve seat 18. Further, compressibility of 
gasket 70 forms a resilient liquid-tight seal against valve seat 18 which 
is resistant to abrasion or wear from the filler contained within certain 
fluids to be dispensed. Gasket 70 is formed of a sufficiently resilient 
material that can deform about any trapped filler particles without 
embedding the particles in the gasket. 
While the present invention has been shown and described herein, it will be 
evident to those persons of ordinary skill that changes and modifications 
may be made without departing from the teachings of the invention. 
Accordingly, that which is set forth in the foregoing description and 
accompanying drawings is offered by way of illustration only and not as a 
limitation. The scope of the invention is defined by the claims.