Note: Descriptions are shown in the official language in which they were submitted.
WO 94/21918 ~ 1 ~i 6 X 2 7 PCT/NZ94/00022
FLEXIBL~ TUBE PUMP
This invention relates to a pump.
Peristaltic pumps as delivery pumps are known whereby fluid
can be driven along a fluid flow passage. This is achieved
by roller or like means coming in contact with a flexible
tube (which forms, or is part of, the fluid flow passage)
so as to compress the tube and move longitl-~; n~ 1 ly
therealong.
There are a number of draw backs with peristaltic pumps.
While they can in some circumstances be arranged to provide
measured "doses" or outputs it is usually not possible (or
at least very difficult) to readily adjust the pump so that
the measured dose or output can be altered. Also such
pumps have been found to require a high level of
maintenance and adjustment. For example they are not
generally readily dismantled for replacement of the tube.
The present invention aims to provide a pump which is not
of peristaltic action but nevertheless relies on
compression and release of a flexible conduit to achieve
the pumping action. It is envisaged that the pump of the
present invention will provide an accurate means of
regulating dosage or volume/rate of output yet be of
straight forward construction.
WO94/21918 PCT~Z94/00022
8~ 2
Broadly in one aspect the present invention provides a pump
comprising a flexible conduit one end being coupleable to a
fluid source and the other end forming or being coupleable
to an outlet, there being pinching means spaced apart
S longitll~i n~l ly of the conduit, said pinching means being
arranged to successively pinch and release the conduit to
result in a pulsed movement of fluid from said one end to
said other end.
In the following more detailed descript:ion of the invention
reference will be made to the accompanying drawings in
which:-
Figure l is a schematic illustration of the main
components of the pump,
Figures 2a - 2e provide a graphic representation of
the opening and closing action of the pinch means,
Figure 3 is a side, partially sectioned, elevation of
one embodiment of the pump according to the invention,
Figure 4 is a plan view of the pump shown in Figure 3,
Figure 5 is an exploded perspective view of the pump
of Figures 3 and 4, and
Figure 6 is a perspective view of a bank of pumps of
the type shown in Figures 3 to 5.
The pump according to the present inven~ion is based on the
concept of controlled compression and release of a flexible
conduit. Accordingly in Figures l and 2 there is
WO94/21918 215 6 ~ 2 7 PCT~Z94/00022
illustrated a flexible tube 10 which at one end 11 is
coupled to or is adapted to be coupled to a fluid source
(not shown). The fluid will generally not be under
pressure but may be pressurised if the source is to be
located so remote from the pump that assistance is required
to move the fluid from the source to the pump, ie. to
assist the action of the pump.
The other end 12 of flexible tube 10 is coupled to, is
adapted to be coupled to or forms an outlet (not shown).
Three pinch means or elements are associated with the
flexible tube 10. These are operative such that they can
move between one state where the tube 10 is compressed
(squeezed) and another state where the tube is
substantially unrestricted. In this respect it should be
noted that the pump elements do not need to totally release
the flexible tube. Thus in the following description a
reference to flexible tube 10 being not compressed covers
situations where partial compression or deformation occurs.
Likewise a reference to the tube being compressed includes
a situation where the tube is substantially compressed but
not necessarily fully pinched closed. The term "pinch"
thus refers to any action applied to the tube whereby the
tube can be compressed so that the flow passage therein is
closed or substantially constricted.
WO94/21918 PCT~Z94/00022
2~ Z ~
Each of the pinch elements 14, 15 and 16 can be formed by a
known solenoid operated pneumatic pinch valve. The pinch
element 14 can be arranged such that the flexible tube 10
can be inserted through a slotted end of the pinch valve to
locate in a recess and be clamped therein by a manual clamp
means. Thus with the solenoid in the inoperative position
the flexible tube lO is compressed. This type of
arrangement is shown in Figure 3 in respect of inlet pinch
element 14. For the purposes of description of Figures 1
and 2, however, all of the pinch elements 14, 15 and 16 are
simply shown as compressing tube 10 when they are
operative. Thus when pinch elements 15 and 16 are in the
"rest" position the flexible tube 10 is unrestricted, ie.
not compressed.
In the preferred form of the invention pinch elements 14
and 16 are located as close as possible together or at
least the "nip" formed in flexible tube 10 by pinch element
16 is as close as possible to the nip of the flexible tube
created by pinch element 14.
Pinch element 14 effectively forms an inlet valve, pinch
element 15 an outlet valve and pinch element 16 a
displacement section as will hereinafter become apparent.
In the schematic illustration of Figure 1 the pinch element
16 is preferably formed by two air cyl; n~ers or l; n~r
WO94/21918 ~15 6 5 2~ PCT~Z94/000~
actuators while pinch elements 14 and 15 are formed by
single air cylinders or linear actuators. The pistons 17
of all the pump elementæ 14, 15 and 16 slide in bores
formed in the pump body 18. The two pistons 17 of pinch
element 16 bear on a compression plate 19 engaged with tube
10 while pistons 17 of pinch elements 14 and 15 are shown
as bearing directly on tube 10. Seals 20 are provided with
pistons 17. The pistons 17 are activated by air pressure
applied thereto via air passages 21 under the control of
electrically operated solenoid valves (not shown) but
described hereinafter in connection with the embodiment of
Figures 3, 4 and 5.
An electronic control circuit (not shown) is provided for
control of the respective solenoid valves of the pinch
elements 14, 15 and 16~ The control circuit provides
control of the sequence of opening and closing of solenoid
valves over an operating (pumping) cycle. The control
circuit also provides for ready adjustment of the number of
cycles in given unit time as well as the number of cycles
in a given period. Furthermore by altering the relative
time between opening and closing of the solenoid valves and
hence operation of the pinch elements 14, 15 and 16 the
amount of output per pumping cycle can be regulated.
The control circuitry is of a type to achieve the functions
described herein. The control behaviour in question may be
WO94/21918 PCT~Z94/000~
~la~2~: 6
achieved by hard-wire systems or by-the use of a suitably
programmed microprocessor. Accordingly the actual hardware
is not described herein as it is well within the scope of
the skilled technician to arrive at circuitry designed to
action the functional control of the solenoid valves as
described herein.
In describing a pumping cycle (as shown in Figure 2) it is
convenient to commence at a point where the pump is in
reset mode with all pinch elements 14, 15 and 16 closed
(tube 10 is constricted) as shown in Figure 2a. Pinch
element 14 then opens (Figure 2b) thus the tube to the
inlet side of pinch element 16 will fill with liquid. This
corresponds to the "inlet valve" being open.
As the cycle proceeds pinch element 15 will remain closed
while pinch element 16 opens so as to leave the fle~ible
tube 10 unrestricted up to pinch element 15 (Figure 2c).
This is followed by pinch element 14 closing and then pinch
element 15 opening so that the inlet is closed and the
outlet opened (Figure 2d). This is followed by pinch
element 16 closing to thereby cause discharge of a pulsed
flow of fluid in the direction of arrow A out the outlet
end of tube 10 (Figure 2e). The volume of fluid (or pulsed
flow) will essentially be the volume of fluid in tube 10
under the compression plate 19.
WO94/21918 ~15 6 8 2 7 PCT~Z9~/00022
Following this a new cycle commences by pinch element 14
opening and pinch element 15 closing to thereby return to
the "inlet open" phase (Figure 2b). Pinch element 16 will
then open (Figure 2c) thereby resulting in a pressure
differential causing inlet fluid to be drawn into the empty
space caused by fluid having been expelled from the
fle~ible tube under the previous closing action of pinch
element 16.
The pump according to the present invention is thus simple
in construction and operation yet provides an effective
means of drawing fluid from a bulk or fluid supply and
dispensing same in a pulsed manner of a pre-determined
volume per pumping cycle. Thus if a given total volume of
liquid is to be dispensed in a given period of time the
control circuit can be adjusted so as to detPr~;ne the
number of pumping cycles per unit time to provide the
overall volume in a required time.
Additionally the relative position of pinch element 16 to
the other pinch elements 14 and 15 could be adjusted so as
to regulate the volume dispensed each pumping cycle. Also
the degree of openness of the pinch elements could be
adjusted to once again provide a physical adjustment of the
dispensed volume.
-
WO94121918 PCT~Z94/000~
2~ 8
The flexible tube 10 is preferably a food grade siliconerubber which exhibits the required degree of elasticity as
well as compressibility. The tube can easily be replaced
by simply removing part of the body 18 and if required
releasing any manual clamps of the solenoid operated pinch
elements. Thus replacement of the flexible tube is a much
simpler and more straight forward operation than with
peristaltic delivery pumps. Furthermore as the tube does
not need to be stretched for correct operation it is
lo believed that the tube will be able to eghibit longer life
characteristics.
Figures 3-5 of the drawings show a more detailed embodiment
of the pump. In this embodiment body 18 is formed by a
lS cylinder block 18a and a cover 18b which is attachable to
the cylinder block via threaded fasteners 22 or other
fasteners such as quick release clips, clamps or the like.
In the preferred form of the invention low restriction
fittings 23 and 24 respectively form the inlet 11 and
outlet 12. These low restriction fittings allow full
rotation so as to suit different installation requirements.
In the preferred form the inlet fitting 23 is of larger
bore diameter. Cover 18b effectively forms a removable
anvil which not only clamps the tube 10 and fittings 23 and
24 in position but also, by being readily removable,
provides for easy replacement of tube 10.
~ WO94/21918 PCT~Z94/00022
~5~ 82 ~
Aæ illustrated pistons 17c of pinch element 16 engage with
a connector or compression plate 19 while piston 17b of
pinch element 15 is coupled to a substantially V-shaped
cross section engagement member 25.
In the manner described earlier piston 17a of pinch element
14 has an engagement member 26 through which tube 10 is
threaded. Located above tube 10 and engagement member 26
are engagement surfaces 27 (Figure 3). When pinch element
14 is in the rest position the tube 10 is constricted and
is unconstricted when the pinch element is operative. Thus
when the pump is in the rest position piston 17a closes
tube 10 so as to prevent siphoning and therefore back-flow.
A bias spring (not shown) is preferably engaged between the
underside of engagement member 26 and recess 33 in cover
18b to force the engagement member into the constricting
(closed) position.
Air passages 21 (not shown in Figures 3-5) are coupled to
transfer passages 28 in the upper surface 32 of body 18a as
shown in Figure 5. This upper surface 32 and hence transfer
passages 28 are covered by a manifold plate 34. A
compressed air source is coupled via air inlet 43. In one
form of the invention the manifold plate can be permanently
connected to the cylinder block 18a.
WO94/21918 PCT~Z94/000~
Bores 14, 15 and 16 of manifold plates 34 connect into
respective ones of transfer passages 28. These bores mate
with openings (not shown) in the base of solenoids 29, 30
and 31. Accordingly operation of the solenoid valve
connects the corresponding piston(s) of pinch elements 14,
15 and 16 to either the source of compressed air or a vent
to atmosphere whereupon the piston moves to compress the
tube or allow the flow passage in the tube to open. Thus
for each set of bores 14, 15 and 16 one bore is coupled
to the respective air passage(s) 21 of the pinch element
14, 15 and 16, one bore is coupled to air inlet 43 and one
is coupled to the vent. In operation the corresponding
solenoid valve opens and closes the other bores so as to
couple the air passage 21 to the source of compressed air
or to vent depending on whether the respective piston 21 is
to close or open the tube 10.
Control of compressed air into the various transfer
passages via controlled operation of solenoid valves 29, 30
and 31 and hence to the air passages 21 causes the pistons
17a, 17b and 17c to operate in the sequence of steps as
previously described. The solenoid operated pneumatic
valves 28, 29 and 30 can, for example/ be Burket type 375
pneumatic valves. These are fastened to the manifold plate
34 by fasteners 36.
WO94/21918 PCT~Z94/00022
2~6 ~7
11
Alæo mounted to manifold plate 34 is a cover 37 within
which is mounted a PCB 38 having switches 39 and an L.E.D.
counter/calibration display 40. To complete the pump a
further cover 41 is provided to cover the tops of the
connector plugs 35 attached to the spade t~rm;nA~s on the
tops of the solenoid valves. cover 37 and 41 can be
combined into a single cover unit.
In the illustrated form of this embodiment of the invention
two of switches 39 can be used to increase or decrease the
cycle rate so as to increase or decrease (as the case may
be) the output of the pump per unit time. The
increased/decreased rate can be selected by reference to a
readout appearing on display 40.
A further switch 39 can provide a calibration function
where the pump operates for a pre-determined period. The
user can measure (volumetrically) the total output over the
period of time and work out the output of the pump for the
selected rate of operation.
Another of the switches 39 can be a reset button to reset
the display 40 when the control circuitry is operative to
give a pre-selected period of operation or number of
~ 25 cycles.
WO94/21918 PCT~Z94/00022
i ~lS~ 8~
The control circuit can include a manual on/off switch, an
automatic sensor switch (ie the pump switches on or off
dependent on sensing an external event or operation of
related equipment) or a pressure switch. Other activating
means will be apparent to those skilled in the art.
To maintain operator/user selected operating parameters in
the event of a power down (either due to temporary power
feed problems or due to the pump being switched off) the
control circuit includes an BEPROM to store the selected
operating parameters.
The pump as illustrated in Figures 3-S is of a simple and
straight forward construction as well as being of
aesthetically pleasing appearance.
The pump is self-cont~;ne~ thus a number of pumps can be
clipped together to form a bank of pumps as shown in Figure
5. To this end the pump is preferably formed with an
openable air outlet (not shown) which can be opened and
mated with the air inlet 43 of the next adjacent pump. As
a consequence a single air supply connected to the air
inlet 43 of one pump can feed all pumps in the bank.
2~ In one form of the invention clips 44 can be used to simply
clip the pumps together into a bank as shown in Figure 5.
WO 94/21918 2~ ~ ~ 6 ~ ~ PCT/NZ94/00022
The pump according to the invention can be used in many
different applications and widely diverse fields. It has
application in the medical, pharmaceutical, food, beverage,
biotechnological, chemical and agricultural industries.
The pump provides a simple means of dispensing a regulated
dose of li~uid from a non pressurised source.
Features of the pump are:-
l. Food Safe.
2. Easy to clean.
3. Self Priming.
4. Low Cost.
5. Reversible.
6. No seals or lubrication required.
7. Can be operated dry without damage.
8. High isolation between input and output.
9. Very low parts count in pump assembly.
The pump is open to modification. For example, it has beenfound that tube lO has a favourable service life which
equates to that of the pistons 17 and sealing rings 20.
Thus body 18, tube lO and the pistons could be of a
disposable form whereupon the entire unit could be simply
replaced.
wOg4/2l9l8 PCT~Z94/00022
8 2 t 14
In another form of the invention the pinch elements can be
formed by cams or eccentrics mounted on a shaft which is
driven directly or indirectly by a motor. The axis of
rotation of the shaft will generally be parallel to the
5 longitl-~; n~l a~is of tube lO. Accordingly the
cams/eccentrics will engage with the tube to pinch the tube
in the sequence described herein to achieve the pumping
action.
other means of controlling pinch elements can be employed
or will be apparent to those skilled in the art and fall
within the scope of the invention as defined in the
following claims.
