Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a pump, more
particularly to a pump intended ~or metering and mixing
a relatively thick fluid, or a suspension of solid
particles in a ]i~uid with, for example, another liquid.
The pump according to the present invention
comprises a cylinder having a first and a second
inlet and an outlet, means for closing
communication between the cylinder and the first inlet
and between the cylinder and the outlet, and, inside the
cylinder, two movable pistons each having at least one
port provided with one or more valves.
In one embodiment of the present invention,
communication between the cylinder and either the
first inlet or the outlet is closed by a distri~utor
valve, and at lea~t one of the pistons is provided
with a non-return valve.
Preferably, one piston has a port which is closable
by a spring-loaded valve.
Preferred embodiments of the present invention are
illustrated with reference to the accompanying drawings, in
which :
Figure 1 is a diagrammatic section of an e~bodiment
showing the components in the starting position of the
pump cycle ;
Figure 2 is the same section as in Figure 1 but
showing operation of the components during the cyc1e ;
Figure 3 is a diagrammatic section of a second
embodiment showing the components at the beginning of a
metering stro~e;
Figure 4 i5 the same section as in Figure 3 but with
the components nearing the end of the mixing or dilution
stro~e.
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In the drawings, the pump comprises a cylinder
1 in which t~o pistons 2 and 3 may reciprocate. Piston
2 is mounted on a piston-rod ~, and piston 3 is
mountcd on a tube 5 coaxial ~ith the piston rod 4.
Piston-rod ~ and tube 5 are actuated independently
by means not represented (for example by air cylinders?.
In another embodiment, they are actuated and
syncllronised by cams. Adjustable stops limit the
piston strolce.
' Piston ~ is provided with a central port wllic}
is nolmally llcl(l c~oscd ~y a valvc 6 by mcans of tlle
tension on a sprin~ coaxial witll piston-rod ll. In
anOt}ler em~Odilllent~ piStOIl 2 iS mounted on piston~rod
4 and the valve 6 is actuatcd by indepcndcnt means.
Piston 3 comprises several ports havin~
non-return valves which enable a liquid to flow only from
right to left in the dra~ing.
Cylinder 1 comprises t~o in]e-ts preferably under
adequatc pressure~ a first one 8 for a thick fluid or a
suspellsion and a second one 9 for a liquid. The cylinder
also comprises an outlet 10 through ~hich the resulting
mixture or diluate flows. In a prcferre(l cm~odimcnt, a
rotata~le distributor valve 11 opens a port at the end of
the cylinder (left on the drawing), thus enabling the
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,
- cylinder to commllnicate either with the first inlet 9
(as shown in Figure 1) or with the outlet 10 ~s sho1~m
in Figure 2). This distributor val~e is actuated in
synchronism with the movement of the pistons 2 and 3 by
means not representecl.
In another embodiment, the first inlet 8 is
proviaed Wit}l a non-return valve which enables fluid to
flow into the cylinder, but prevents it from flot~ing out
tllrougll thc inlet. Outlet 10, is provided ~ith a
non~return valve ~hich enables the resulting mixture or
diluate to flow out of the cylinder but stops-suction in.
The operation o~ the pump is as follows:
Starting from the position shown in Figure 1,
the two pistons 2 and 3 move from the left to the right,
piston 3 having a greater speed and a longer stro~e than
~iston 2. During this movement, piston 2 dra~s in the
fluid through the first inlet 8(valve 6 being closed)
wllcrcas ~ilc liquid ~rawn in by thc sçcon~ inlct 9 passes
Irom the rigllt to the left o~ piston 3 through the non-
return ~alves 7. At the end Or the stroke a portion of
the liquid brought in through the second inlet 9 is
contained between the pistons 2 and 3 and a portion of
fluid brought in through the first inlet 8 is contained
between distributor valve 11 and piston 2.
Distributor valve 11 then leaves a communication
bctwccn cylin~cr 1 and outlet 10 (Figure 2) and the
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pistons move the other way (i.e. from ri.ght to left in
the drawing). The non-return valves 7 clo3e and
piston-rod 4 opens valve 6. In this way, the portion
of liquid which was contained between the two pistons
passes through piston 2 and mixes with the fluid. At
the end of the stroke, the mixture is forced through
the outlet 10 in its entirety and the cs-lce starts again.
In the embodiment shown in figures 3 and 4, 12a and 12b
may be regarded as two parts of one cylinder 12 at right
angle to each other. As in the embodiment of Figures 1 and 2, the
pump comprises two inlets preferably under adequate pressure,
the first, 13,for a thic]~ fluid or a suspension and the
second, 14, for a liquid. It also comprises an outlet
16 through which the resulting mixture or diluate flows,
a rotatable distributor valve 17 opening a port at the end
of the part 12b (left on the drawing), thus providing
communication between the cylinder and either the inlet
13tas ~hown in Figure 3) or the outlet 16 (as sho~n ir.
Figure 4). This distributor valve is actuated in synchronism
with the movements of piston 18 reciprocating in the part 12a
of the cylinder and of piston 19 reciprocating in the part 120
of the cylinder.
The piston 18 is mounted on a piston rod 20 and is
actuated by means (not represented)such as for ex~mple
an air cylinder connected to the piston rod 20. The piston 19
is mounted on a piston rod 21 and is normally held at the
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right end of the part 12b of the cyl7nder b~ means of the tension
of a coil spring coaxial with the piston rod 21. Stops limit
the travel of the pistons.
The piston 18 has several ports provided with non-return
valves which only enable a liquid to flow through the piston
when the latter is moving upwards. The piston 19 has a
central port provided with a valve 22 which is normally
heid closed by a coil spring. This valve 22 is connected to
a plate 23 located in a chamber inside the piston; the chamber
communicates with the part 12b of the cylinder by ports in
the right hand wall of the piston.
The operation is as follows ;
Be~inning with the position shown in Figure 3, the
piston 18 moves upwards, its non-return valves cpen
and the liquid which entered through the inlet 14 passes fro~
the upper to the lower face of the piston. Due to the
pressure release between the pistons 18 and 19 while the
former goes up, the valve 22 closes;assisted by the coil
spring, the piston 19 moves from left to right, drawing
the thick fluid or suspension through the inlet 13 into the
cylinder. When the piston 18 has reached its upper position and
the piston 19 its right hand stop, part 12a of ~he cylinder is
full of liquid and part 12b of the cylinder is full of the thick
fluid or suspension. This is the end of the me~ering stroke.
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The distributor valve 17 is then turned in the position
sho~n in Figure 4, providing a communication between
cylinder 12 and outlet 16. The piston 18 moves
downwards, its non-return valves close, liquid is drawn
into the cylinder through inlet 14 and piston 19 is moved to
the left b'y the liquid between pistons 18 and 19 until it
reaches its left stop. Pressure of the liquid on the plate
23 then opens the valve 22 (Figure 4) and the liquid passes through
the central port of the piston 19 towards the outlet 16.
When the piston 18 has reached its lower stop, ending
the mi~ture or dilution stroke, the cycle starts again.
