Note: Descriptions are shown in the official language in which they were submitted.
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2149~B
PUMP VALVE
BACKGROUND OF THE INVENTION
The invention relates to pumps and specifically to a pumping valve, which is
particularly useful in positive displacement pumps.
For various reasons, which are well known to those of ordinary skill in the
pumping art, positive displacement pumps are particularly suited for use under specific
5 conditions. Among other characteristics which are particular to positive displacement
pumps, such pumps may be used to precisely measure quantities of fluids being pumped
and may develop relatively high pumping forces.
One drawback to the use of positive displacement pumps, including piston-type
pumps, is that the pump operating cycle will commonly be two cycles, namely, an intake
10 or loading stroke and an exhaust or pumping stroke. Thus, a piston pump typically
provides a pulsed fluid flow, not a continuous fluid flow.
Attempts have been made to adapt piston pumps for a double action stroke cycle to
minimi~ the pulsed fluid flow. A double action stroke cycle is designed with a pumping
action on each direction of the piston stroke and provided with some method of fluid
15 supply to both sides of the piston. Common examples of prior double acting piston
pumps include the use of spill through valves, typically a spring-loaded ball valve located
in the piston, to allow axial passage through the piston of a portion of the pumped fluid.
Other designs have included valved fluid passages around the piston.
These known double action pumps are typically complicated, however, and
20 commonly require intricate machining and a multiplicity of components. Maintenance of
these known double acting pumps is also rather involved, directly correlating to the
complexity of the design and multiplicity of components. Repeated maintenance is also a
common requirement, because the valves typically used, especially the ball valves, are
prone to clogging and "blow-by" or leakage of the pumped fluid. Particular to the piston
25 embedded spill through valve designs, is the problem that once the piston head is clear of
the pump cylinder, the head will still need to be disassembled to access the embedded
valve.
SUMMARY OF THE INVENTION
Accordingly, the invention addresses the problems of obtaining a continuous fluid
30 flow with a positive displacement or piston pump. A pump according to the invention
includes a piston cylinder with a cylinder wall defining an interior chamber; a piston
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having an exterior surface defining a conic frustrom and spaced from the cylinder wall; a
piston rod extending from the piston and through an end of the chamber to a terminal
end; a drive member connected with the piston rod terminal end to alternatively stroke the
piston in opposing back and forth directions; a cooperating, annular valve ring having an
exterior surface abutting the cylinder wall in fluid tight sealing and sliding engagement;
and a valve stop positioned on a side of the annular ring that is opposite the piston. The
piston slides relative to the annular ring, between a first position in which the exterior
piston surface abuts in fluid tight sealing engagement an interior ring surface of the valve
ring and a second position in which the exterior piston surface and the interior ring
surface are spaced apart and define a fluid passage between the piston and the valve ring.
The valve stop is located to define the spacing between the piston and the valve ring in
the second position, the valve ring abutting the valve stop when in the second position.
These and other features, objects, and benefits of the invention will be recognized
by those who practice the invention and by those skilled- in the art, from the specification,
the claims, and the drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a centerline cross-sectional view of a pump according to the invention,
showing the piston moving away from one end of the piston stroke;
Figure 2 is the view of Figure 1 showing the piston moving away from the
opposing end of the piston stroke;
Figure 3 is an enlarged, exploded, cross-sectional view of the piston and valve
ring of the pump of Figures 1 and 2;
Figure 4 is an elevational view of the face of the piston of Figure 3;
Figure 5 is the view of Figure 1 showing an alternative piston configuration;
Figure 6 is the view of Figure 2 showing the piston of Figure 5;
Figure 7 is an enlarged cross-sectional view of the valve stop shown in Figures 5
and 6;
Figure 8 is an enlarged cross-sectional view of the alternative piston configuration
of Figures 5 and 6.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
Rer~lling to the drawing figures and Figures 1-4 in greater detail, a piston pump
according to the invention is generally identified by reference numeral 10. Pump 10
includes a pump head 12, a piston cylinder 14, a piston rod 16, a valve stop 18, a valve
5 ring 20, and a piston 22.
Pump head 12 (Figs. 1 and 2) may be of any construction suitable to the pumping
task at hand and may be fabricated from any appl~,pliate structural or engineering
material, including, but not limited to, plastics and metals. In simplest form, pump head
12 may be a block of material which is cross bored or drilled to form an inlet 24 to a
fluid passage 26. Pump 10 is connected at inlet 24 with a source of fluid to be pumped
by piping, hoses, or other conduits (not shown). At some point along the fluid
connection between inlet 24 and the source of fluid, a one-way valve or foot valve should
be installed to insure one-way flow of the fluid from the source to pump 10 and avoid
backflow of the fluid. One may find installation of the foot valve in inlet 24 or passage
26 to be convenient. A cylinder seat 27 is formed at one end of passage 26, opposite
inlet 24. Piston cylinder 14 is seated in cylinder seat 27 and fastened to pump head 12 by
any of various conventional means commonly available to and known by those of
ordinary skill in the ~umpillg art.
As with pump head 12, piston cylinder 14, and substantially all components of
20 pump 10, may be fabricated of any suitable structural or engineering material, which is
compatible from a corrosion perspective with the material of pump head 12 and with the
fluid to be pumped. Preferably, the material of piston cylinder 14 has a good wear
resistant characteristic. While piston cylinder 14 may be configured with any number of
cross-sectional shapes, a circular cross-sectional shape will typically be employed with an
25 interior wall 28 defining a right circular cylindrical interior chamber 30.
A fluid outlet 34 is provided near a second end 36 of piston cylinder 14. Pump 10
is connected at outlet 34 with a fluid destination by piping, hoses, or other conduits (not
shown). Similar to inlet 24, a one-way valve should be installed at some point along the
fluid conduit from outlet 34 to assure one-way flow of fluid out from outlet 34 and pump
30 10. One may find installation of a one-way valve at outlet 34 to be convenient.
Valve stop 18 is preferably configured as an annular ring having a piston rod seat
40. A stop surface 42 is provided on a face of valve stop 18 which faces away from
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piston rod 16, toward first end 32 of piston cylinder 14. Similar to the series of fluid
passages 58 provided in piston 22 and discussed below, a series of fluid passages 44 are
provided through valve stop 18 to allow fluid to pass through the valve stop as is
discussed further below. A threaded rod stud 50 extends through valve stop 18 and
5 engages cooperating threads 52 in piston 22.
As is shown more clearly in Figures 3 and 4, piston 22 is a generally right
circular cylindrical member having internal threads 52 for engagement with and secure
fastening of piston 22 to piston rod 16. A square cut recess 54 is provided in a face 56
of piston 22 to facilitate screw fastening of piston 22 to piston rod 16 with a socket
10 wrench or the like. A series of fluid passages 58 extend longitudinally through piston 22
and provide passage of fluid through piston 22, from piston face 56 to a back portion of
piston 22. The combined cross-sectional area of passages 58 is preferably at least as
large as the cross-sectional area of inlet 24 to avoid fluid flow throttling or choking
through passages 58.
Piston 22 has an exterior piston surface 60 that abuts piston cylinder interior wall
28 in fluid tight sealing and sliding engagement. Exterior piston surface 60 circumscribes
piston 22 and is provided with circumscribing seal seats 62 and a circumscribing bearing
seat 64. As shown in Figures 1 and 2, "O" rings 66 or the like sit in seal seat 62 and
seal between piston 22 and piston cylinder 14 while an annular bearing 68 sits in bearing
seat 64 as is well understood in the pump art.
Piston 22 is also provided with a tapered, circumscribing seal surface 72 (Fig. 3),
defining a conic frustrom portion of piston 22. The taper of seal surface may be of any
slope that is appropriate to the specific pump installation and is most preferably about
fifteen degrees (15) as shown in the drawing figures or greater. Seal surface 72 is
positioned on a side of exterior piston surface 60 that is opposite piston face 56 and is
oriented with a decreasing taper extending away from piston face 56. Further, seal
surface 72 abuts a cooperating valve ring interior surface 78 in fluid tight sealing
engagement when piston 22 slides relative to valve ring 20, into a first position in which
seal surface 72 abuts interior ring surface 78 (Fig. 1).
Valve ring 20 is most preferably an annular ring having interior ring surface 78 as
just discussed and an exterior ring surface 80. Exterior ring surface 80 engages the
piston cylinder interior wall 28 in fluid tight sealing and sliding engagement. Similar to
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exterior piston surface 60, exterior ring surface 80 is provided with seal seats 82 in which
"O" ring seals 84 or the like sit (Figs. 1 and 2). Valve ring 20 also has a stop surface 86
on a side of valve ring 20 which faces away from interior ring surface 78 and piston 22
(Fig. 3), to face stop surface 42 of valve stop 18 (Fig. 1).
In use, pump 10 will draw fluid into chamber 30, through inlet 24 and fluid
passage 26, when piston rod 16 and piston 22 are near or adjacent pump head 12 (piston
cylinder first end 32) and drawn toward piston cylinder second end 36 during an intake
stroke. Also during the intake stroke, friction forces between "O" rings 84 and piston
cylinder interior wall 28 initially hold valve ring 20 stationary until piston seal surface 72
and interior ring surface 78 abut in sealing engagement, in a first relative position
between the piston and valve ring, and piston 22 pushes valve ring 20 through chamber
30. As piston 22 pushes valve ring 20, hydraulic forces combine with the friction forces
of seals 84 to press piston seal surface 72 and interior ring surface 78 into tighter contact.
If pump 10 is already primed so that fluid fills chamber 30 on both sides of piston 22 and
valve stop 18, then fluid is forced out of outlet 34, while piston 22 draws closer to piston
cylinder second end 36 as shown by the arrows of Figure 1.
After reaching the end of the intake stroke, piston 22 is near or adjacent piston
cylinder second end 36 and begins to stroke back toward pump head 12 and piston
cylinder first end 32 in a pumping or discharge stroke. At the beginning of this return
stroke, seals 84 again hold valve ring 20 stationary relative to piston cylinder 14. But,
valve stop surface 42 soon abuts valve ring stop surface 86 as piston 22 moves away from
valve ring 20 to a second relative position between the piston and valve ring, in which
piston seal surface 72 is spaced from interior ring surface 78 and an annular fluid passage
90 is defined between piston 22 and valve ring 20. Thus, while piston rod 16 strokes
piston 22 toward pump head 12, fluid in chamber 30 between piston face 56 and pump
head 12 is forced through piston fluid passages 58, around piston seal surface 72, through
fluid passage 90, and through valve stop 18 by way of valve stop fluid passages 44.
Further, because piston rod 16 displaces a volume of chamber 30 between valve
stop 18 and piston cylinder second end 36, a portion of the fluid which is pumped from
between piston face 56 and pump head 12, as just described, is also pumped through
outlet 34. As those who are skilled in the art and those who practice the invention will
appreciate, the flow of fluid through outlet 34 during a stroke in one direction or the
21t$9356
other may be constant or differentiated. For the flow of fluid through outlet 34 to be
constant during stroking and either direction, the cross-sectional area of piston rod 16
must be exactly one-half the cross-sectional area of chamber 30. If the cross-sectional
area of piston rod 16 is less than one-half the cross-sectional area of chamber 30, then the
fluid flow through outlet 34 during a ~ulllping or discharge stroke will be less than the
fluid flow through outlet 34 during an intake stroke. The inverse relationship also holds.
That is, if the cross-sectional area of piston rod 16 is more than one-half the cross-
sectional area of chamber 30, then a greater flow of fluid through outlet 34 will occur on
a discharge stroke than will occur on an intake stroke.
An alternative configuration 110 of a pump according to the invention is shown in
drawing Figures 5-8. Pump 110 differs from pump 10 primarily in the configuration of
its piston 122 and valve stop 118. The majority of the rem~ining pump components are
interchangeable between the alternative pump embodiments 10 and 110 and will,
therefore, be referenced by the same reference numbers and not redescribed.
As compared with piston 22, piston 122 is a llullcal~d version in which the
exterior piston surface 60 portion of the piston is cut away and the sealing surface 72
portion remains. Thus, piston 122 has a tapered, circumscribing seal surface 172 (Fig.
8), generally defining a conic frustrom configuration of piston 122. As with piston 22,
piston 122 is also provided with internal threads 52 for engagement with and secure
fastening of piston 122 to piston rod 16. A square cut recess 154 is also provided in a
face 156 of piston 122 to facilitate screw fastening of piston 122 to piston rod 16 with a
socket wrench or the like. As with piston 22, seal surface 172 of piston 122 abuts valve
ring interior surface 78 in fluid tight sealing engagement when piston 122 slides relative
to valve ring 20, into a first position in which seal surface 172 abuts interior ring surface
78 (Fig. 5).
One element of piston 22 which is conspicuously absent from piston 122 is bearing
68. As those who are familiar with the pump art and those who practice the invention
will appreciate, it is desirable to have a bearing between the piston cylinder interior wall
28 and the assembly of piston rod 16, valve stop 18, and piston 122. Valve stop 18 is,
therefore, modified to provide for bearing 68 and become valve stop 118 as shown in
Figures 5, 6, and 7.
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Valve stop 118 is preferably configured as an annular ring having a piston rod seat
140 and a stop surface 142 provided on a face of the valve stop 118. Stop surface 142
faces away from piston rod 16 and toward first end 32 of piston cylinder 14. Similar to
valve stop 18, valve stop 118 has a series of fluid passages 144 to allow fluid to pass
through the valve stop. The fluid passages 144 are, however, somewhat di~l~nlly
arranged than fluid passages 44 in order to accommodate the placement f bearing 68 in
valve stop 118. More particularly, a bearing seat 164 is provided in a circumscribing
exterior surface 180 of valve stop 18. Thus, fluid passages 144 are inset, inside bearing
seat 164.
In use, pump 110 will draw fluid into chamber 30, through inlet 24 and fluid
passage 26, during an intake stroke of piston rod 16 and piston 22 (Fig. 5). During the
intake stroke, friction forces between "O" rings 84 and piston cylinder interior wall 28
initially hold valve ring 20 stationary until piston seal surface 172 and interior ring
surface 78 abut in sealing engagement, in a first relative position between the piston and
valve ring, and piston 122 pushes valve ring 20 through chamber 30. Again, hydraulic
forces combine with the friction forces to press piston seal surface 172 and interior ring
surface 78 into tighter contact. If pump 110 is primed, then fluid is forced out of outlet
34 during the intake stroke as shown by the arrows of Figure 5.
During the discharge stroke (Fig. 6) seals 84 again hold valve ring 20 stationary
relative to piston cylinder 14, until valve stop surface 142 abuts valve ring stop surface
86, while piston 122 moves away from valve ring 20 to a second relative positionbetween the piston and valve ring, in which piston seal surface 172 is spaced from
interior ring surface 78 and an annular fluid passage 190 is defined between the piston
and valve ring. Thus, while piston rod 16 strokes piston 122 toward pump head 12during a discharge stroke, fluid in chamber 30 between piston face 156 and pump head 12
is forced around piston 122 and piston seal surface 172, through fluid passage 190, and
through valve stop 118 by way of valve stop fluid passages 144.
It will be understood by those who practice the invention and by those skilled in
the art, that various modifications and improvements may be made to the invention
without departing from the spirit of the disclosed concept. The scope of protection
afforded is to be determined by the claims and by the breadth of h~lel~ tion allowed by
law.
