Diaphragm pump

A diaphragm pump for use with corrosive fluids. The pump comprises a pair of opposed fluid chambers each defined in part by a flexible diaphragm. The pump also includes means for reciprocally driving the diaphragms and inlet and outlet check valves. The unique structure of the pump allows all wetted components thereof to be economically formed from a substantially chemically inert material such as polytetrafluoroethylene and the like.

BACKGROUND 
This invention relates to diaphragm pumps and more particularly to such 
pumps for use with corrosive fluids. 
A major drawback of many popular industrial pumps, i.e., piston, impeller 
or the like is that such pumps employ relatively movable seals and 
bearings in a compressive means in an attempt to protect and/or separate 
the pump drive means from the fluid handled by the pump. Not only must 
such seals and bearings be routinely repaired or replaced due to normal 
wear and tear thereof, these components often exhibit accelerated wear and 
failure where the pump is required to handle corrosive fluids. 
Diaphragm pumps have been employed in industrial applications for use with 
chemically aggressive and/or corrosive fluids with limited success. While 
such pumps employ as pumping members diaphragms fixedly sealed about the 
perimeter thereof, therefor requiring no movable seals or bearings, 
various other of the pump components being formed from conventional 
materials subject to premature failure from attack by corrosive fluids 
render such prior art diaphragm pumps not entirely suitable for use with 
corrosive fluids. 
Although certain relatively inert materials such as polypropylene and 
polytetrafluoroethylene are known to be able to withstand exposure to many 
corrosive industrial fluids, the strength of such materials has heretofore 
limited their use in industrial pumps to linings for the various wetted 
pump components. Thus, diaphragm pumps such as that disclosed in U.S. Pat. 
No. 3,000,320 to Ring for handling corrosive fluids are required to have 
all the wetted components thereof formed from structural material such as 
steel and the like lined with a suitable chemically inert material as by 
coating, molding or laminating techniques. 
Accordingly, it is a principal object of the present invention to provide a 
diaphragm pump which overcomes the deficiencies of the prior art. 
It is another object of the present invention to provide a diaphragm pump 
capable of handling corrosive fluids without risk of corrosive attack of 
the pump by the fluid. 
It is another object of the present invention to provide a diaphragm pump 
for handling corrosive fluids wherein the pump is formed entirely from 
chemically inert materials. 
It is yet another object of the present invention to provide a diaphragm 
pump for handling corrosive fluids, the pump being economic to manufacture 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, the diaphragm pump of the present invention 
illustrated generally at 10, comprises a pair of end caps 15 each housing 
a fluid chamber 20 defined in part by a flexible diaphragm 25 (FIG. 6). 
The fluid chambers communicate with inlet check valve means 30 and outlet 
check valve means 35 disposed between the end caps. The diaphragms are 
reciprocally driven by any suitable drive means 40 powered by air or any 
equivalent medium and also disposed between the end caps. In the preferred 
embodiment, the pump structure is such that all wetted or fluid contacting 
components thereof are formed entirely of a non-metallic and chemically 
inert material such as but not limited to PVC, CPVC, polycarbonate, 
polypropylene or polytetrafluoroethylene sold by E. I. DuPont de Nemours 
and Co. under the trademark TEFLON without a sacrifice in strength. For 
ease in portability the pump may be provided with a handle 45 fixed 
thereto at any convenient location. 
Each end cap 15 comprises a unitary member or block of the hereinabove 
described chemically inert material having a concave depression or fluid 
chamber 20 formed therein as by any appropriate machining or molding 
techniques. Each of the fluid chambers has extending from the side surface 
thereof a pair of extension passages 50 and 55. Each pair of extension 
passages provides communication between the corresponding fluid chamber 
and a pair of adjacent inlet and outlet check valves. In the preferred 
embodiment, the extension passages are formed by drilling or boring from 
an edge of the cap and sealing as with threaded plug 60. Each of the 
extension passages opens to the inner surface of the cap for connection to 
the check valves at elongate openings 65 which ensure proper connection 
with the check valves despite some misalignment between the check valves 
and the end caps. The end caps are bored axially therethrough about the 
periphery of the fluid chambers at locations of connection with the check 
valves, the bores receiving through bolts 70 or similar fastening means 
for maintaining the check valves, diaphragms and drive means in fixed, 
clamped, engagement between the caps. 
Diaphragm 25, as best illustrated in FIG. 6, is of a two-ply construction 
comprising an outer ply 75 which contacts the fluid handled by the pump 
and is thus formed from a sheet of the chemically inert material discussed 
above. To provide added flexibility to the diaphragm, the outer ply is 
backed by an inner elastomeric ply 80 of neoprene or similar material 
which is isolated from contact with any corrosive fluids by the outer ply. 
The diaphragms are sealed from leakage about the peripheries thereof, by a 
fixed clamped engagement between the end cap and the housing for drive 
means 40. Such a fixed corrosion resistant seal, unlike relatively movable 
seals or packing, requires little or no maintenance and prevents leakage 
of fluid into the drive means. 
The diaphragms are fixed to the drive means by any suitable means. In the 
preferred embodiment, drive means 40 is provided with an interiorly 
threaded reciprocating shaft 85 which receives a threaded stud 90. The 
threaded stud fixes a hub 95 and back plate 100 with the diaphragm clamped 
therebetween to the shaft such that reciprocal drive motion of the shaft 
causes a corresponding reciprocal diaphragm motion. The hub is, of course, 
contacted by the pumped fluid within chamber 20 and is, therefore, formed 
of the corrosion resistant material described above. In that it may be 
desirable to form stud 90 from steel or other corrosible material, the 
head thereof is sealed from the pumped liquid by disposition within a 
threaded cavity in the hub, the cavity being sealed closed by threaded cap 
105 and interior O-ring 110. 
As set forth hereinabove, drive means 40 may be of any suitable variety 
capable of simultaneously moving the diaphragm in a reciprocal rectilinear 
fashion. In the preferred embodiment, driven means 40 includes a 
compressed air powered reciprocating slide valve but alternate drive means 
will suggest themselves to those skilled in the art. Therefore, it will be 
understood that as one diaphragm is moved in a compressive stroke (toward 
the interior of the corresponding fluid chamber), the other is moved in a 
suction stroke (away from the interior of the corresponding fluid 
chamber). 
Fluid is drawn into each fluid chamber through the corresponding inlet 
extension passage 55 from the inlet check valve means 30. The inlet check 
valve means includes a pair of inlet check valves 112 each disposed 
adjacent the inlet extension passage 55 in the corresponding end cap and 
comprising in part a single valve cage 115 having a longitudinally 
extending passage 120 formed in the interior thereof, passage 120 
providing communication between a main pump fluid inlet 125 and the check 
valves, the inlet being formed approximately in the center of cage 115 and 
extending generally transverse to the longitudinal axis thereof. Passage 
120 is most conveniently formed by drilling or boring through the cage and 
plugging the passage opening as with threaded plug 130. The end portions 
of the side of cage 115 have inlet valve chambers 135 formed therein, the 
chambers receiving spherical inlet valve elements 140 and being open at 
the bottom for communication with passage 120. As best seen in FIG. 4, 
each valve chember is of generally clover-leaf cross section being formed 
from the intersection of four generally cylindrical corner bores 142 which 
allow flow around the valve element and a central bore 143 which provides 
a vertical track in which the valve element moves. Each chamber has a 
valve seat 145 formed about the bottom opening, the seats being generally 
of a spherical contour. Inlet valve chambers 135 communicate at the tops 
thereof with elongate openings 65 and extension passages 55 in caps 15 
over sloped, recessed portions 150 of the cage ends. Inlet valve chambers 
135 are enclosed by inlet valve housings 155 comprising open ended sleeves 
which receive the end portions of the inlet valve cage, defining the upper 
portion of the inlet valve chamber. The inlet valve housings may be sealed 
to the inlet valve cage and end caps by means of O-rings 160 seated in 
recesses in the ends of the housings. 
The inlet check valve housings, cages and valve elements are formed 
entirely of the chemically inert, corrosion resistant material discussed 
above. The inlet cage and housings may be drilled or bored longitudinally 
in alignment with the holes in the end caps whereby the inlet check valves 
are maintained in fixed clamped engagement between the end caps by means 
of through-bolts 70. As best seen in FIG. 1, inlet valve cage 115 may be 
provided with an enlarged central portion 162 for enhanced strength and to 
define, with housings 155, a smooth cylindrical outer surface. 
Outlet valve means 35 comprises a pair of outlet check valves 164 each of 
which includes a valve cage 165 having a shank portion 170 and an end 
plate 175. The shank portion includes an outlet valve chamber 180 formed 
in the side thereof, the chamber being open at the bottom thereof for 
communication with longitudinal passage 185. Passage 185 provides 
communication with an adjacent one of the fluid chambers 20 through 
opening 65 and outlet extension passsage 50 in end cap 20. Outlet valve 
chamber 180 receives a spherical valve element 190 which is normally 
seated on conforming seats 195 surrounding the opening in the valve 
chamber bottom and while not specifically shown is of generally the same 
clover-leaf shape as the inlet valve chambers. 
The outlet valve cages are received within the ends of outlet check valve 
housing 200 comprising a sleeve which through the interior thereof, 
provides communication between the outlet check valves and the main pump 
outlet 205. The outlet valve housing is of a diameter substantially equal 
to that of the end plates whereby the outer surface of the outlet check 
valve means is smoothly cylindrical for ease in cleaning dirt and 
contaminants therefrom. The outlet cases are sealed to the housing and end 
caps by means of O-rings 210. The outlet valve cages housing and valve 
elements are formed from the above described chemically inert material and 
the outlet valve means is fixed between the end caps by means of through 
bolts 70 extending through longitudinal holes in the cases and housing. 
It will thus be appreciated that the diaphragm pump of the present 
invention exhibits an economy of manufacture in that excluding the 
stationary O-rings, bolts, and the drive means, the pump comprises only 
twelve component parts. This structure is characterized by a strength 
which allows the pump to be formed entirely from chemically inert 
materials heretofore thought to be inherently too weak for such structural 
purposes. Being so constructed, the pump is entirely free from risk of 
attack by most industrial corrosive fluids, is self-priming and can handle 
fluids with excessive particulate matter therein with little risk of 
fouling. 
Operation of the pump is as follows: When one of the diaphragms is driven 
in a compressive stroke, fluid in the corresponding chamber 20 is forced 
through extension passage 50, forcing an adjacent outlet check valve off 
its seat allowing the fluid to flow through this valve to the main pump 
outlet 205. The pressurized fluid forces the adjacent inlet valve closed, 
thereby preventing any fluid discharge through the main inlet passage. 
During this compression stroke, the opposite diaphragm is driven in a 
suction stroke described next. 
On the opposite stroke of the drive means, this diaphragm will be driven in 
a suction stroke whereby the adjacent inlet valve element is lifted off 
its seat allowing fluid to fill fluid chamber 20 from the main pump inlet 
through the inlet valve and extension passage 55 while the adjacent outlet 
valve element remains seated blocking communication between the chamber 20 
and the pump outlet. During this suction stroke, the opposite diaphragm is 
now moved in a compression stroke described hereinabove.