Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUN~ OF TH~ INVENTION
The present invention relates generally to positive
displacement piston pumps and, more particularly, is
directed to a submersible positive displacement piston pump
having particular applicability to the delivery of small
quantities of liquid to an application device.
For metering small amounts of liquid from a transport
drum to an application device, it is well known to use
pumps. For example, U.S. Patent No. 4,583,290, and having a
common assignee herewith, describes an air driven diaphragm
pump which discharges liquid pulses at a constant rate and
which is used to transfer a few liters of chemicals per day
from a transport drum to an application point. The
application point, as an example, can be a coating hood for
coating glass bottles.
An advantage of this pump is that it uses air pressure
operated valves which prevent liquid leakage commonly found
in pumps using conventional ball check valves. However,
while this pump produces good results, differences in stroke
volume of, for example, 20%, due to workmanship and membrane
quality, may exist between different air driven diaphragm
pumps.
In order to overcome these deficiencies, positive
displacement piston pumps, such as disclosed in U.S. Patent
Nos. 3,168,872; 3,257,953; and 4,008,003, and particularly,
as modified in U.S. Patent No. 4,536,140 having a common
assignee herewith, have been used. The pump in the latter
U.S. patent has been found suitable for pumping liquid
organometallic compounds used in the coating of glass
bottles with tin oxide or other metal oxides.
With such pumps, the pumping chamber is kept out of the
transport drum and a hose from the fluid inlet extends into
the drum. Thus, the chemicals are pumped out of the drum,
through the hose, and into the pumping chamber. ~owever,
as discussed in U.S. Patent No~ 4,536,140, a problem with
X positive displacement piston pumps is that the
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chemical may migrate from the pumping chamber to a space
between the piston and cylinder walls, even with the
closest of tolerances between the reciprocating piston and
the interior cylinder wall. Where the chemical is a
corrosive material such as a monobutyltin trichloride
containing formulation, the minute migration of liquid
chemical may result in the build-up of metalhydroxy
compounds between the reciprocating piston and inner
cylinder wall. Such compounds are formed by reaction of
the chemical with water vapor in ambient air. Because of
such build-up, the piston may freeze in the cylinder,
causing failure of the apparatus.
The aforementioned ~.S. Patent No. 4,536,140 attempts
to overcome these deficiencies by providing a separate oil
barrier with constant oil pressure between the piston and
inner cylinder wall. However, the use of such a barrier
greatly complicates the apparatus. Further, the sealing
oil, dependent upon the application, may interfere with the
pump operation.
Another problem with such pumps is that minute amounts
of air entering the pump may interfere with proper
operation, resulting in a lower pumping rate.
Specifically, gases, such as air, hydrogen, carbon dioxide
and the like which are carried in the fluid, are often
released in the cylinder as a result of agitation of the
fluid durin~ the pumping operation or as a result of
pressure and temperature changes. For example, some fluids
respond to agitation and/or pressure and temperature
changes by chemically separating into liquid and gas
fractions, while other fluids simply vaporize, physically
changing from liquid to gaseous form. The problem that
results is that the gases form bubbles which become trapped
in the pumping head of the cylinder, thereby spoiling the
metering precision of the pump, and in some situations,
3S blocking flow completely. Generally, the gas bubbles
become trapped between the recessed section of the piston
and the inner wall of the cylinder.
Specifically, when the pump is not operating at full
capacity, that is, when the piston is pivoted to less than
its maximum extent, the piston is caused to eecipeocate
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over a lesser distance between its retracted position and
extended position. As a result, the top of the recessed
section remains above the outlet port at all times during
reciprocation of the piston. Gas bubbles formed between the
recessed section and the inner wall of the cylinder thereby
remain during the pumping operation, adversely affecting the
same. It will be appreciated that the smaller the piston
stroke, the more gas that will be trapped by the recessed
lo section, thereby increasing the ratio of volume of entrapped
gas to pump displacement. In other words, the pump becomes
gas sensitive.
because of this problem, a pump operating at less than
maximum capacity must have its flow rate changed several
times. Entrapped gas will then flow out of the pump,
restoring its set delivery rate. However, such capacity
changes are bothersome and time consuming. When used, for
example, for pumping fluid to coat bottles, such capacity
changes cause excess usage of expensive coating chemicals or
cause insufficient coating on the bottles.
This latter problem of minute amounts of air entering
the pump has been solved by the invention of U.S. Patent No.
4,575,317.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention
to provide a positive displacement piston pump that inhibits
freezin~ of the piston in the cylinder.
It is another object of the present invention to
provide a positive displacement piston pump that prevents
build-up of metalhydroxy compounds between the reciprocating
piston and inner cylinder wall.
It is still another object of the present invention to
provide a positive displacement piston pump that eliminates
the need to use a barrier fluid.
It is yet another object of the present invention to
provide a positive displacement piston pump that prevents
undesirable bubble formation in the cylinder chamber.
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In accordance with an aspect of the present invention, a pump
includes cylinder means for insertion within a body of liquid, the
cylinder means including an inlet port and an outlet port; piston
means rotationally and reciprocally movable in the cylinder means
for pumping liquid from the inlet port to the outlet port, the
piston means including a recessed section alternately in fluid
communicatioff with the inlet port and the outlet port; a pivoting
assembly pivotally connected to drive means for rotationally and
reciprocally driving the piston means in the cylinder means; and
extension means for connecting said pivoting assembly to said
piston means and for positioning said cylinder means in a body of
liquid while said pivoting assembly and said drive means are in
position out of said body of liquid.
In accordance with another aspect of the present invention, a
pump includes cylinder means for insertion within a body of
liquid, the cylinder means including a working end, an inlet port,
an outlet port and a working chamber bounded by the outlet port
and the working end; piston means rotationally and reciprocally
movable in the cylinder means between a retracted position and an
extended position for pumping liquid from the inlet port to the
outlet port, the piston means including a free end having a
recessed section alternately in fluid communication with the inlet
port and the outlet port; a pivoting assembly pivotally connected
to drive means for rotationally and reciprocally driving the
piston means in the cylinder means: means for ensuring that the
recessed section is positioned entirely in the working chamber
when the piston means is in the extended position, regardless of
the angle between the piston means and the drive means: and
extension means for connecting said pivoting assembly to said
piston means and for positioning said cylinder means in a body of
liquid while said pivoting assembly and said drive means are in
position out of said body of liquid.
The above and other objects, features and advantages of the
present invention will become readily apparent from the following
detailed description which is to be read in connection with the
accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a partial longitudinal cross-sectional view
of a submersible positive displacement piston pump
according to one embodiment of the present invention;
Fig. 2 is a plan view, partly in phantom, of a portion
of the pump of Fig. l; and
Fig. 3 is a partial cross-sectional view of the
piston-cylinder end of the pump of Fig. 1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to the drawings in detail, and initially to
Fig. 1 thereof, a submersible positive displacement piston
pump 10 according to one embodiment of the present
invention is shown which is suitable, for example, for
pumping liquid organometallic compounds used in the coating
of glass bottles with tin oxide or other metal oxides.
As shown in Figs. 1 and 3, pump 10 includes a hollow
cylinder 12 having a closed working end 14 and an opposite
end 15 haviny a bore 16 therein. Diametrically opposite
inlet and outlet ports 18 and 20, respectively, are formed
in cylinder 12, adjacent working end 14. An outlet
connection 22 is secured externally of cylinder 12 in
surrounding relation to outlet port 20 and includes a
coupling 23 for attaching one end of a delivery hose 24.
The fluid to be pumped is therefore pumped from outlet port
20 to delivery hose 24. A working chamber 26 is also
formed in cylinder 12, being bounded by working end 14 and
ports 18 and 20, and is in fluid communication with ports
18 and 20.
A piston 28 is rotatably and reciprocably positioned
in cylinder 12 through bore 16, and includes a free end 30
and a driven end 32. Free end 30 is formed with a flat,
recessed section 34 which is alternately in fluid
communication with ports 18 and 20 as piston 28 rotates
within cylinder 12. Thus, recessed section 34 functions as
a duct between ports 18 and 20, alternately opening and
closing each port 18 and 20 in sequence. Recessed section
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~34, together with that portion of working chamber 26 at the
hea~ of piston 28, cooperates in forming the cylindee
pumping chamber, whereby fluid is pumped between ports 18
and 20.
At the opposite end of pump 10, there is provided a
drive motor 36 having an output drive shaft 38, and which
is mounted on a base plate 40. An electric cable 42
extends through a cable protection hose 44 which is
connected to the housing of motor 36, for supplying power
to the motor. A collar or yoke 46 having a reduced boss 48
is keyed to drive shaft 38 by any suitable means, such as a
2in 50 extendiny through reduced boss 48 and drive shaft
38. Yoke 46 is provided with a socket 52. One end of a
laterally projecting or transverse arm 54 is secured to one
end of a shaft 56, and the opposite end of arm 54 has a
ball or spherical bearing 58 secured thereto. Ball 58 is
received in socket 52 to form a universal ball and socket
joint. Thus, as drive shaft 38 rotates, shaft 56 is caused
to rotate and reciprocate in a manner well known and
described in the above-mentioned ~.S. Patents relating to
positive displacenlent piston pumps.
It will be appreciated that such ball and socket joint
arrangement permits pivoting of drive shaft 38 with respect
to shaft 56. It is well known that the amount of
reciprocation (and therefore the position of piston 28 in
cylinder 12) will vary depending on the angle at which
drive shaft 38 is pivoted with respect to shaft 56. Thus,
the pump stroke will vary depending on such angle. For
example, when drive shaft 38 is pivoted with respect to
shaft 56 to its maximum extent, that is, when the pump is
operating at maximum pump stroke, the piston reciprocates
over a maximum distance between its retracted position and
extended position in cylinder 12.
In accordance with the present invention, piston 28 is
connected to shaft 56 by a shaft extension 60, whereby
motor 36 controls the rotation and reciprocation of piston
28 in cylinder 12. A piston connector 61 is connected to
the lower end of shaft extension 60 for connecting piston
28 thereto. With this arrangement, cylinder 12 and piston
28 are submerged at the bottom of a body of liquid 62
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~contained in a drum 64, while motor 36 and related parts at
the drive end of the assembly are maintained out of the
drum and liquid.
This provides distinct advantages not achieved with
the prior art. specifically, since the compounds in the
cylinder are not exposed to ambient air, the problem of
metalhydroxy compounds being formed in a space between the
piston and cylinder walls, is overcome. As a result, there
is no freezing of the piston in the cylinder. Further,
because such disadvantage of the prior art devices is
overcome, there is no need to use an oil barrier, as
described in U.S. Patent No. 4,536,140.
As shown in Fig. 1, shaft extension 60 is surrounded
by a hollow extension pipe 66 which is sealingly secured at
its lower end to the upper end 15 of cylinder 12, and which
extends out of drum 64 and is secured at its upper end to a
bracket 68. Base plate 40 is also secured to bracket 68.
Extension pipe 66 includes an aperture 70 at the lower end
thereof and an aperture 72 at the end extending out of drum
64. In this manner, delivery hose 24 extends through lower
aperture 70, through extension pipe 66 and out of upper
aperture 72, where it is connected to a coupling 74 secured
the outside of extension pipe 66 by means of a lock ring
76.
In addition, extension pipe 66 is provided with a
further set of apertures 78 at the lower end thereof, which
are positioned a small distance above the connection
thereof to cylinder 12. Accordingly, since extension pipe
66 is sealed to the upper end of cylinder 12, that even if
the drum is emptied of liquid (or the liquid level falls
below the upper level of cylinder 12), liquid is still
present where piston 28 extends out of cylinder 12. This
provides a liquid seal at the upper end of cylinder 12,
thereby avoiding the formation of metalhydroxy compounds
between the piston and inner cylinder wall,since no air or
water vapor enters into the pump (except when changing
drums). As a result, there is no need to use any seaiing
oil, which may interfere with the pump operation. This also
avoids the need to provide apparatus for maintaining
sufficient oil pressures.
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It will be appreciated that apertures 78 are formed at
a height sufficient to provide the aforementioned seal,
while also permitting liquid contents to be drained when
changing drums.
As shown in Fig. 1, drum 64 is provided with an
aperture 80 at its upper end through which extension pipe
66 extends and at which point extension pipe 66 is secured
to drum 64. Specifically, drum aperture 80 is provided
with a bondle thread 82, and a bondle cap 84 having
external screw threads is provided in surrounding relation
to extension pipe 66 for matinyly engaging with bondle
thread 82 and providing a seal for drum aperture 80. A
lock ring 85 is secured to extension pipe 66 just above
bondle cap 84 by means of a bolt 86, and a lock ring 88 is
secured to extension piFe 66 just below bondle cap 84 by
means of a bolt 90. In this manner, bondle cap 84 is
secured to extension pipe 66, and extension pipe 66 is
secured to drum 64.
A pipe closure 92 is provided inside the upper end of
extension pipe 66 and is secured thereto by means of bolt
86 which, as aforesaid, also secures lock ring 85 to
extension pipe 66. Pipe closure 92 is provided with an
axially extending central aperture 94 to permit passage
therethrough of shaft extension 60, and is further provided
with another axially extending aperture 96 to permit
passage of delivery hose 24 therethrough.
As also shown in Fig. 1, a bracket plate 98 is secured
coaxially within the upper end of extension pipe 66 by
means of a bolt 100 which also secures coupling 74 to the
outside of extension pipe 66. Bracket plate 98, in turn,
has a drive bearing 102 secured therewithin, and drive
bearing 102 surrounds shaft 56 to permit shaft 56 to rotate
and reciprocate therein.
As previously discussed, however, gases, such as air,
hydrogen, carbon dioxide and the like which are carried in
the fluid, are often released in the pumping chamber of
cylinder 12 as a result of agitation of the fluid during
the pumping operation or as a result of pressure and
temperature changes. As a result, the released gases form
bubbles which become trapped in the pumping chamber of
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cylinder 12, thereby spoiling the metering precision of pump
1o/ and in some situations, blocking flow completely,
particularly where the pump is operating at less than
maximum capacity, that is, when drive shaft 38 is pivoted
with respect to shaft 56 at an angle less than its maximum
extent. Generally, the gas bubbles become trapped between
recessed section 34 of piston 28 and the inner wall of
cylinder 12, as discussed more fully in aforementioned
commonly assigned U.S. Patent No. 4,575,317.
In order to overcome this problem, the above U.~.
patent application provides an arrangement which shifts the
retracted and extended positions of piston 28 within
cylinder 12, without changing the piston stroke, for any
angular displacement of drive shaft 38 with respect to shaft
56. As a result, the flow rate remains the same, while
eliminating the problem of trapped gas.
Specifically, as shown in Fig.2, base plate 40 is
provided with two elongated, slightly arcuate slots 104 and
106 which are elongated in the general direction of a centre
line 108 which extends along the axis of shaft extension 60
and piston 28, the slots being positioned on opposite sides
of centre line 108.
A friction plate 110 to which yoke 46 and motor 36 are
secured includes two pivot pins 113 and 115 (shown in
phantom in Fig.2), which fit within respective slots 104 and
106. Thus, pivoting of motor 36, which can be accomplished
by a holding a grip 112 (secured to base plate 40) and
moving motor 36, results in yoke 46 pivoting with respect to
shaft 56 due to the aforementioned ball and socket
connection. This, in turn, changes the pump stroke, which
can be measured by means of a scale 114 and pointer 116
adjacent grip 112.
Generally, the distance between pivot pins 113 and 115
i8 approximately equal to the diameter of the circle
travelled by the centre of ball 58 during each revolution of
yoke 46.
Because of this arrangement, the aforementioned
problems with respect to air entering the working chamber
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~in the cylinder of a conventional pump are avoided.
Having describec a specific preferred embodiment of
the invention w.ith reference to the accompanying drawings,
it will be appreciated that the present invention is not
limited to that precise embodiment, and that various
changes and modifications can be effected therein by one of
ordinary skill in the art without departing from the scope
or spirit of the invention, as defined by the appended
claims.
