Air operated diaphragm pump system

An air-operated diaphragm pump assembly for withdrawing small volumes of liquid from a receptacle until the receptacle is almost completely emptied. The pump assembly includes a diaphragm pump that is submerged within the liquid in one receptacle, an extension sleeve extending upwardly from the pump to a position above the receptacle, fluid logic circuitry to operate the pump, inlet conduit(s) passing through the sleeve to transmit control pulses to the pump, and outlet conduit(s) passing through the sleeve to discharge the liquid forced out of the pump in response to the control pulses. The fluid logic circuitry includes a pneumatic Schmitt-Trigger that is operatively associated with a pneumatic inverter. The diaphragm pump includes a pumping diaphragm and a driving diaphragm, the diaphragms being coupled together to drive a displacer within a pumping chamber in response to a pressure differential to thereby expel the liquid contained therein.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a diaphragm pump system for 
delivering small volumes of liquids, and more particularly to an air 
operated diaphragm pump system that employs fluid logic circuitry to drive 
a diaphragm pump submerged within the liquid to be discharged. 
2. Prior Art 
The need to (1) effectively drain all of the fluid present in a storage 
drum, or other vessel, and to (2) discharge same at a constant rate, is a 
frequently occurring problem arising in diverse industrial situations. One 
conventional solution of this problem is to employ a reciprocating 
displacement pump. Such pump is secured to the storage vessel above the 
liquid level, and a conduit depends below the pump into the liquid. 
Electrical or hydraulic control signals are supplied to an operator for 
the pump, and the pump functions to draw fluid upwardly through the 
conduit and discharge same through an outlet port. One representative 
prior art pump is disclosed in U.S. Pat. No. 3,285,182, granted Nov. 15, 
1966, to Harry E. Pinkerton, and another representative prior art pump is 
disclosed in U.S. Pat. No. 3,814,548, granted June 4, 1974 to Warren E. 
Rupp. 
Known small reciprocating pumps, however, require a priming action before 
the liquid can be pumped from the storage vessel. Larger reciprocating 
positive displacement pumps may have such a capability designed therein. 
More specifically, the larger pumps realize high ratios of displaced 
volume per stroke to the total volume of the conduits between the inner 
and outlet valves of said pumps. Such high ratios are unobtainable in 
known small reciprocating pumps for the conduits must be greater in size 
than the theoretical minimums if the pumps are to function satisfactorily. 
An alternative response to the priming problem is to connect the inlet 
side of the pump to the storage vessel in a liquid-tight manner, and to 
then manually or mechanically manipulate the vessel so that the liquid 
level within the drum is elevated above the inlet connection and the pump. 
The alternative response obviously calls for repeated handling of the 
storage vessel with attendant increased operating costs. 
SUMMARY OF THE INVENTION 
With the deficiencies of the conventional positive displacement pumps 
clearly in mind, the present invention contemplates an air operated 
diaphragm pump system that will effectively drain substantially all of the 
fluid present in a storage drum or the like, and discharge same in a 
series of liquid pulses that approximates a continuous stream. The 
diaphragm pump of the present system is submerged within the liquid in the 
drum with its inlet port adjacent to the bottom thereof, thus obviating 
the usual requirement for an inlet conduit leading to a pump positioned 
above the liquid level and minimizing, if not eliminating, priming 
problems. Furthermore, the present diaphragm pump is sealed in a leakproof 
manner so that the pump is virtually immune from attack by the corrosive 
or contaminated liquids within which it may be submerged. 
The present system includes an extension sleeve which projects upwardly 
from the submerged pump and terminates at a location spaced above the 
drum. The extension sleeve encloses the conduits leading from a remotely 
situated pulse generator to the submerged pump, and also encloses a 
conduit leading from the pump to a delivery point, which may assume the 
form of a discharge nozzle, atomizer, or the like. The sleeve, which may 
be fabricated from a rigid or semi-rigid metal or plastic, passes through 
an aperture in the cover for the drum and protects the conduits from 
attack by the liquid contained in the drum. 
The present system includes a pulse generator that utilizes fluid logic 
circuitry to provide control pulses of air for operating the diaphragm 
pump in the desired manner. The diaphragm pump includes a driving 
membrane, a pumping membrane, and a displacer operatively associated with 
the membranes. The logic circuitry supplies pressure pulses to the driving 
membrane for the displacement strokes, whereas reversed pressure pulses 
are fed in between both membranes to effect the return strokes. The 
displacer comprises a cap, a spacer, and a clamping plate, which are 
joined together by a fastener that is threaded into an axially extending 
bore in the displacer. The cap expels the fluid retained in a chamber in 
the pump body in response to the application of a pressure pulse to the 
driving membrane. 
The present system is relatively simple, inexpensive to produce, install 
and maintain, and yet is capable of draining almost all of the fluid 
contained within a drum or other storage vessel and discharging same at a 
constant rate of but a few liters per day. Furthermore, the logic 
circuitry can be readily adjusted so that the rate of fluid discharge can 
be altered over a range of values. Additional advantages of the present 
system will become readily apparent to the skilled artisan from the 
appended drawings and the accompanying description.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turning now to the drawings, FIG. 1 depicts a large metallic drum 100 
having a capacity of 80 gallons. The liquid level line is indicated by 
dotted line 102, and a fragment of the drum has been removed to show the 
interior thereof. A lid 104 seals the open upper end of drum 100, and an 
aperture 106 is formed through the lid. 
An air-operated, diaphragm pump assembly, indicated generally by reference 
numeral 110, is operatively connected to the drum 100 for draining its 
contents in a unique and highly efficient manner. The assembly 110 
comprises a diaphragm pump 112 positioned on, or closely adjacent to, the 
bottom of drum 100, an extension sleeve 114 projecting upwardly from the 
pump 112 through the aperture 106, and a collar 116 secured to the upper 
end of the extension sleeve. The diaphragm pump assembly further includes 
a pulse generator 118, an air supply line 120 for delivering pressurized 
air to the pulse generator, and two conduits 122, 124 which extend from 
the pulse generator, through collar 116 and extension sleeve 114, and into 
communication with pump 112. A third conduit 126 leads upwardly from pump 
112, through extension sleeve 114, collar 116 and terminates at delivery 
point 128. The conduits are maintained substantially parallel to one 
another by banding straps (not shown) and by the collar 116 which guides 
the conduits into extension sleeve 114 and toward diaphragm pump 112. The 
sleeve protects the conduits from attack by the liquid contained in the 
drum. 
FIGS. 2 and 3 are vertical cross-sectional views of the air operated 
diaphragm pump 112 taken at right angles to one another. The pump 112 
includes a body, formed of a plastic, such as polypropylene. The body is 
comprised of distinct segments such as a cap 130, an upper body segment 
132, a first sealing gasket 134 retained between the cap 130 and segment 
132, intermediate body segments 136 and 138, lower body segment 142, and 
base 144. A second sealing gasket 146 is retained between body segments 
132 and 136, and a third sealing gasket 148 is retained between lower body 
segment 142 and base 144. 
A first flexible diaphragm 150 is retained between body segments 136 and 
138, and a second flexible diaphragm 152 is retained between body segment 
138 and body segment 142. Diaphragm 150 is deemed to be a pumping 
diaphragm, while diaphragm 152 is deemed to be a driving diaphragm. The 
reasons for such terminology will become evident at a later point in the 
specification. 
A displacer, indicated generally by reference numeral 154, is joined to 
diaphragms 150 and 152 by a threaded screw 156 which extends upwardly into 
a central bore. As seen in FIGS. 2 and 3, and particularly in FIG. 5, the 
displacer comprises a cap 155, a spacer 157, and a clamping plate 159. The 
head of screw 156 projects below the surface of clamping plate 159. The 
displacer 154 responds to differential pressures exerted upon the 
diaphragm 150 and 152. Displacer 154 is shown in its assembled condition 
in FIGS. 2 and 3, and is prior to assembly in FIG. 5. 
Four vertically extending rods 158 pass through openings in each body 
segment, gasket, and diaphragm; each rod is threaded at its opposite ends 
and nuts 160 are placed thereon. By tightening the nuts 160, the pump 112 
is retained in assembled, operative condition and the sealing gaskets keep 
the interior of the pump leak-free. FIG. 4 is a top plan view of the 
air-operated, diaphragm pump 112, such view being taken along lines 4--4 
in FIG. 2 and in the direction indicated. 
The vertically oriented extension sleeve 114 is integrally formed with the 
cap 130 of the pump, and conduits 122, 124 and 126 pass through extension 
sleeve 114 into the cavity defined in the cap 130. Conduit 122 is secured 
to coupling 162, and the coupling is seated within the upper end of a 
passage 164 that leads downwardly through apertures in gasket 146, 
diaphragms 150 and 152, and terminates in a chamber 166 that communicates 
with the lower face of diaphragm 152. Conduit 124 is secured to coupling 
168, and the coupling is seated with the upper end of a passage 170 that 
leads downwardly through apertures in gasket 146 and diaphragm 150 and 
terminates in a chamber 172 defined between the upper face of diaphragm 
152 and the lower face of diaphragm 150. 
Conduit 126 is secured to a coupling 174, and the coupling is seated within 
the upper end of a central passage 176 that leads downwardly through 
gasket 146 to a pumping chamber 178 defined above diaphragm 150 in 
intermediate section 138. A first ball valve 180 is normally seated upon 
valve seat 182 to block communication between chamber 178 and passage 176. 
An inlet passage 184 leads upwardly through the base 144, through an 
aperture in gasket 148, through segment 142, diaphragm 152, segment 138, 
diaphragm 150 and thence beyond valve seat 182 for communication with 
passage 176 and pumping chamber 178. A second ball valve 186 is normally 
seated upon valve seat 188 to prevent fluid drawn beyond the valve seat 
from flowing back into the drum from whence it was withdrawn. 
An adjustment screw 190 is located in the pump body within a threaded 
passageway that opens into chamber 166. The screw can be advanced within 
the passageway so that its inner end projects into the chamber 166 toward 
the head of fastener 156, thereby limiting the diaphragm stroke. A sealing 
ring 192 fits about the shank of the screw, so that the chamber 166 is 
maintained leak-free. Plugs 194 are employed to seal the internal passages 
in the body of the pump. 
FIG. 6 schematically shows the pneumatic logic circuitry for pulse 
generator 118 that operates the diaphragm pump 112 in a manner that will 
withdraw almost all of the fluid retained in drum 100 at very low flow 
rates. The logic circuitry is secured within the housing for pulse 
generator 118, and the pulse generator is retained in a fixed position at 
a location remote from the drum 100. 
The pulse generator receives compressed air at above atmospheric pressures 
over supply line 120. A valve 195 is adjusted to admit the compressed air 
to the pulse generator, and a combined filter and pressure reducer 197 
prevents particles in the flow line from clogging the logic circuitry as 
well as stepping down the pressure level in the supply line to a level 
compatible with the operating parameters of the logic circuitry. The 
compressed air leaving filter and pressure reducer 197 over line 120 flows 
into a T coupling 193 and divides into first supply line 199 and second 
supply line 201. Supply lines 199 and 201 introduce the compressed air 
into pneumatic logic elements 202 and 204, respectively. 
Logic elements 202 and 204 may assume diverse forms, including pure fluid 
components with no moving parts or hybrid elements combining fluid flow 
techniques with toggles, switches, deflectors, and other mechanical 
control elements. Logic elements 202 and 204 are commercially available 
components that may be purchased from Samson A G of Frankfurt, W. Germany 
or from Samsomatic Ltd., Fairfield, N.J., U.S.A. Logic element 202 is the 
pneumatic analogue to a Schmitt-Trigger or bistable flip flop, while logic 
element 204 is a pneumatic inverter. The structural details of logic 
element 202 are shown in FIG. 7, and the inverter 204 is similar in 
design. 
Logic element 202 includes supply channel 208, outlet channel 206, vent 
channel 210, and toggle element 212. The toggle may assume many forms and 
yet function with equal facility; in the exemplary embodiment, the toggle 
is driven by a membrane 213 reinforced by a metal insert 215; in all 
instances, however, the element must be capable of flexing quickly between 
two stable states. A spring 214 normally biases the toggle to one of its 
two stable states, and control ports 216, 218 are located on opposite 
sides of the membrane 213. Control pulses are introduced at port 216. The 
position of the toggle element determines whether outlet channel 206 
receives compressed air pressure or vents to atmosphere through channel 
210. In the circuit shown in FIG. 6, the spring 214 normally biases the 
toggle to its extreme left hand position. When pressure is present at 
outlet channel 206, air will pass via conduit 250 and restrictions 251 and 
252 to bleedline 253. Depending upon the relative values of the 
restrictions, air pressure will act on membrane 213 to assist in retaining 
the toggle element 212 in its present position. 
If control pressure is built up at control port 216, the toggle element 
will only shift to its other stable position, if this control pressure is 
high enough (0.85 Bar) to overcome both the spring 214 and the pressure at 
control port 218. 
Once the toggle element begins to move, outlet channel 206 will vent to 
atmosphere via outlet channel 210. The pressure at port 218 will drop to 
zero and the toggle element will move rapidly to its new position. Such 
Schmitt-Trigger action causes switching of logic element 202 at exactly 
predetermined pressures at control port 216. 
As shown in FIG. 7, restrictions 251 and 252 form an integral part of the 
pneumatic Schmitt-Trigger 202, as available from Samsomatic. 
FIG. 6 schematically represents the normal flow paths for the pressurized 
air passing through the logic circuitry. Spring 214 biases toggle element 
212 to its "home" position, and the fluid flow in supply line 199 enters 
supply channel 208 and exits through outlet channel 206. Toggle element 
212, in its home position, prevents communication between supply channel 
208 and vent channel 210. 
The flow emanating from outlet channel 206 enters coupling 220, and then 
divides into distinct paths. One path, as indicated by the elongated 
directional arrow, leads over conduit 122, through coupling 162, and 
through passage 164 to deliver a pulse of pressurized air to the chamber 
166. The pulse of pressurized air, acting upon the enlarged head of the 
clamping plate 159 of displacer 154, is of sufficient magnitude to drive 
the displacer 154 and diaphragms momentarily upwardly. The movement of the 
membrane 150 within pumping chamber 178 forces liquid contained therein 
past ball valve 180 and discharges same through conduit 126 to delivery 
point 128. Chamber 178 will receive an initial charge of liquid when the 
pump is submerged. 
A portion of the outlet flow from coupling 250 will enter a second path, or 
feedback loop, for logic element (Schmitt-Trigger) 202 and return over the 
loop to control port 216, as indicated by the smaller directional arrows 
in FIG. 6. The feedback loop includes a variable pneumatic resistor 222 
and a pneumatic accumulator (or volume) 224; these elements are also 
conventional in design and are available commercially from several 
sources, including Samson A G. The setting for resistor 222 is adjusted to 
control the rate at which pressure increases within accumulator 224. The 
pressure in the accumulator increases until reaching the level of 0.85 Bar 
in one hardware implementation of the circuit of FIG. 6. At such level the 
corresponding pressure signal present at control port 216 is sufficient to 
overcome the bias of spring 214 and force the toggle element 212 to switch 
to its alternate stable position. In this alternate position, toggle 
element 212 prevents flow in supply channel 208 from reaching outlet 
channel 206. Channel 206 is vented to atmosphere via channel 210. 
When outlet channel 206 drops toward a zero pressure level, the pressure in 
the accumulator 224 in the feedback loop diminishes as air escapes 
therefrom through resistor 222. When the pressure in accumulator 224 drops 
below 0.25 Bar, the toggle element 212 is snapped back to its "home" 
position by spring 214. Pressure is then re-established in outlet channel 
206 at a level of 2 Bar. The cycle of alternately discharging fluid at a 
pressure of 2 Bar at outlet channel 210, and then venting the pressure to 
atmosphere via outlet channel 208 will repeat itself as long as switch 226 
is closed. FIG. 6 shows the switch 226 in its normal, closed position, 
indicated as the "a" position. The switch is moved to its "b" position, 
when empty barrels are being removed and new barrels 100 of liquid are 
being connected to the instant system. With switch 226 in its "b" 
position, the pressure in accumulator 224 will not be reflected at control 
port 216; consequently, the Schmitt-Trigger will not alternate between its 
stable stages, but will continuously discharge fluid through outlet 
channel 210 at a pressure level of 2 Bar. 
The remaining portion of the outlet flow from channel 206 travels over a 
third path and influences the operation of logic element 204. Logic 
element 204 performs an inversion function, and is identified as an 
inverter. The inverter is a conventional logic element available from 
Samsomatic AG. The inverter includes a supply channel 232, a control port 
230, an aperture 231, outlet channel 228 and vent 234, a toggle element 
236, and a spring 238 for biasing the toggle toward a home, or normal, 
position. The third flow path from channel 206 leads to the control port 
230 of inverter 204. When a pressure signal is present in channel 206, 
such signal is manifested at control port 230 at a pressure level high 
enough to overcome the bias of spring 238 and force toggle element 236 to 
snap over center and assume its other stable state. When a pressure signal 
is absent from channel 206, no control signal is manifested at port 230, 
and spring 238 forces the toggle element to return to its home position, 
which is shown in FIG. 6. 
The interconnection of the Schmitt-Trigger 202 and the inverter 204 
produces pulse trains that approximate a square wave, as shown in FIG. 6. 
As indicated, when the pressure in outlet channel 206 of element 202 
reaches its maximum, the pressure in outlet channel 228 of inverter 204 
drops to its minimum. The pressure levels are reversed when flow through 
outlet channel 206 by movement of toggle element 212 and logic element 202 
is vented to atmosphere over outlet channel 210. 
These relationships of pressure pulses are shown by the traces of the pulse 
trains delivered from logic element 202 to conduit 122 and from logic 
element 204 to conduit 124. As noted previously, when the pulse from logic 
element 202 reaches its maximum pressure level, the pulse from 
interconnected logic element 204 is cut off and the pressure in chamber 
172 drops to its lowest level. The pressure differential across the 
diaphragm 152 is thus maximized and the membrane 150 is driven forcefully 
through chamber 178 to expel liquid therefrom. 
Furthermore, by altering the setting of variable resistor 222, the rate at 
which accumulator 224 is filled is varied, and the rate at which pulses 
appear at control port 216 is changed, and the rapidity at which toggle 
element 212 is switched between its stable states is similarly changed. 
The setting for resistor 222 therefor determines the rate at which fluid 
will be discharged at a constant rate by the air operated diaphragm pump 
system; such setting may be adjusted over a wide range of values with 
attendant changes in the discharge rate for the system. 
The foregoing description of the air operated diaphragm pump system is but 
a preferred embodiment, and numerous modifications and revisions may occur 
to the skilled artisan. For example, the logic circuitry may assume 
diverse forms, including pure fluid components with necessary amplifiers. 
Also, if the delivery pressure of pump 112 is kept relatively low, 
inverter 204 might be omitted and the pressure in conduit 124 might be 
maintained at a constant pressure approximately one half of the maximum 
pressure in conduit 122. 
The extension sleeve 114 may be formed as an integral part of the cap 130 
of the pump body, or may be formed as a separate component which is 
subsequently secured thereto. The pulse generator 118 may be bolted or 
otherwise secured to a fixture secured to the lid 104 of the drum. The lid 
for the drum may be omitted, and the extension sleeve can be secured to 
the receptacle in another fashion to project vertically upwardly. The 
diaphragms 150, 152 may be formed from a wide variety of long lived, 
flexible materials, such as natural rubber or fluoroelastomers. 
Consequently, the appended claims should not be limited to their literal 
terms, but should be construed in a manner consistent with the material 
advance in the useful arts and sciences represented by the present 
invention.