Note: Descriptions are shown in the official language in which they were submitted.
7~
A PUMP FOR SUPPLYING A LIQUID ADDITIVE
rro A FLOW OF LIQUID
This invention relates to a pump for supplying a liquid
additive to a ~low o~ liquid,
Pumps for this puxpose are well known, see for example
oU~E~ Patent Nos. 1243732 and 1387880, Both o~ those
5 pumps are primarily for use in horticul-ture i.e. for
introducing quantities o~ liquid -fertilizer into
irrigation water. Whilst they operate satisfactorily
in their intended en~ironment, in particular they
overcome the problem of injecting additive into flowing
10 liquid9 they are not the first choice o~ pump ~or certain
other environments e,g. environments where there is no
electricity i.e~ remote rural areas, or environments
where ~ire hazards have to be avoided at all costs
e.g. in petro-chemical industrial plant. For use in
15 petro-chemical industrial plant, pumps may be ~lame proo~ed
and other appropriate measure may be taken. However these
measures in themselves tend to greatly increase the
production costs of the pumps.
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It is there$ore an object of the present invention
to provide a pump which is suitable -for use in a wide
range of environments, whether industrial, agricultural
or horticultural 9 and which does not depend ior its
operation on an electricity supply, and finally, which
is of a simple and economic construction to manufacture
and service~ According to one aspect of the present
invention there is provided a pump for supplying liquid
additive to a flow of liquidS comprising a aosing
chamber communicating with an inlet opening and an
outlet opening for a liquid additive, each said opening-
being controlled by a non return valve~ a first
displaceable member arranged in said dosing cha~ber
and operative to dispense said liquid additive, said
first displaceable member being operatively connected
byconnection means to a second displaceable member
arranged iIl an opera-ting chamber, said second
displaceable member being arranged $o partition said
operating chamber into ~irst and second opera-ting
chambers, each of said first and second operating
chambers having a respective por-t for CQmmuniCatiOn
with a supply o~ operating ~luid~ operating switc~ing
means ~or controlling the supply of operating fluid to
said ports of said ~irst and second operating chambers,
said operating switching means being operative such
that when one of said first and second operating
chambers is being supplied with operating fluid the
respective other operating chamber is being evacuated
whereby successi.ve switching
of said operating switching means effects reciprocation
of said connection means and thereby dispensing oi
measured qua~tities o~ liquid additive from the ~osing
chamber, wherein said operating switching means is fluid
actuated9 and a pilot switching means is mechanically
associated with said reciprocating connection moans
~2~6
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and is operati~ely coupled by ~luid couplings to
the ~luid actuated operating switching means, the
pilot switching means and the ~luid actuated switching
means thus coupled being operable such that, at the
end o~ each stroke of the reciprocating connection
means~ said ~luid ac-tuated switching means is
actuated to change the supply o~ operating fluid ~rom
one to the other of said operating chambers.
In the pre~erred embodiment said first displaceable
member is a piston, said dosing chamber is arrangad
wi-thin a dosing head, said second displaceable
member is an operating diaphram, said operating chambers
are de~ined by an operating head, and the connectior
means includes piston rod means coupled with both
displaceable members
Embodiments o~ such a pump may be constructed to
operate with either hydraulic or p~eumatic actuation
i.e. with either a liquid, ~or example water, or air
as the operating ~luid which is supplied and evacuated
from the ~irst and second operating chambers.
In a particular application namely in a water
puri~ication system ~or the supply o~ puri~ied water
for domestic purposes in isolated villages in under-
developed territories, the operating ~luid may be the
water which is being purified. This water may be
pumped, for exampleJ by a diesel pump to a village
~0 reservoir and the pressure of the water in transit
may be employed to drive this pump ~or the additive
(i.e. agent ~or puri~ying the water). In this case~
it should be appreciated that the water evacuated from
the ~irst and second opera-ting chambers is directed
back to ~ource, whereby the precious co~odity (water)
is not lost.
~L2~
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On the other hand, the pump may be pneumatically
actuated, for example, in industrial environments
where it is common place for there to be an abundant
supply of compressed air for driving industrial plant.
In this case since the volumes of air used by this
pump are rela-tively small, the air ~rom the first and
second operating chambers ma~ be evacuated to atmosphere.
In a preferred embodi~ent, the fluid actuated switching
means is a spool valve or a slide valve which is
actuated under fluid con-trol by the pilot switching
means, -the condition of said pilot switching l~eans
controlling the application of pilot operating fluid
from said pilot switchirlg means to said fluid actuated
switching means and thereby the selection of which of
said firs-t and second operating chambers is supplied
with operating fluid.
In the preferred embodiment, said pilot switching
means is a spool or slide valve arranged to control by
fluid control the fluid actuated switching means and
itself being mechanically actuated to change state at
each end ofeach s-troke o~ thereciprocating connection means
bymeansof actuating stopsassociated with the reciprocating
connection means.
It should be appreciated that the chambersi~ the operating
head and dosing head may be relatively proportioned
(that is to say the effective piston area and diaphram
area may be relatively proportioned) as to ensure that
the pressure of the additive leaving the ~osing head
is sufficient for injection of the addi-tive into the
liquid i~to which it is to be mixed. It will be
readily appreciated that the outlet of the dosing head
may be coupled to a vessel or pipework through which
said liquid is flowing. Typical values of the
, .
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mechanical advantage which may be obtained with
embodiments of the pu~ps herein defined arc ~rom
11:1 down to 2.5:1. A ratio of ll:i indicates that
the pressure of the liquid to be dosed may be eleven
times greater than the pressure of the operating
fluid. It is an advantageous feature o~ the
construction o~ embodiments of the invention that
the size of dosing head and piston associated therewith
may be a customised unit with the remainder of the
structure defining the pump being of standard
components.
The aforegoing defined pUlUp with a single dosing head
may be termed a "simplex" pump By the addition of a
second dosing head itself having a secondconnection means
operatively connected with said member, a "duple~"
pump is provided whereby the pump is capable of
metering additive via each of the two dosing heads.
~he additives dosedby the two dosing heads may be the
same additives, for example, to two dif~erent flows
of liquid or different additives, for example7 to the
same flow of liquid. The dosing capacity o~ the two
dosing heads may be the same or different.
The volw~e of additive passed by the or each dosing
head on each actuation thereof may be adjustable.
~ For this purpose the connection between the ~ember of
; the dosing head and the member oft~s operating
head may include a variable lost motion coupling
thereby to adjust the effective stroke of theconnee-tion means.
The lost motion coupling preferably has cali~ration
means giving a visual indication of the dosing rate
of the dosingchamber f~ different settings of the lost
motion coupling.
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An embodiment o~ the invention will now be described
by way ol' example only~ with reference t~ the
accompanying drawing which shows in sectional
elevation a pump ~or supplying a liqLuid additive
to a flow o~ liquidO
In the drawing there is shown a "simplex" pump ~or
supplying a liquid additive to a flow o-i liquid. A
dosing head 10 defines a dosing chamber il
communicating with an inlet opening 12 and an outlet
opening 13 for a liquid additive. Each of the ~enings
i2, 13 is controlled by a respective non re-turn valve 15.
A ~irst displaceable member 20, which is in the ~orm oi
a piston member, is arranged in the dosing chamber 11
and is operative to dispense said liquid additive
through the outlet opening 13. This ~irst displaceable
member 20 is opera-tively connected by connection means
30 (to be ~urther described) to 2 second displaceable
member 40, the latter being arranged in an operating
cham~er 50. ~he second displaceable member 40, which
is in the ~orm of a diaphragm, is arranged to partition
operating chamber 50 into ~irst and second operating
chambers 51, 52. Each of the ~irst and second operating
chambers 51, 52 having a respective port 53~ 54 for
communication wi-th a supply o~ operating ~luid 55.
Operating switching means 60 controls the supply o~
operating ~luid 55 to the ports 53, 54 o~ the ~irst an~
second operating chambers 51, 52. This operating
: switching means 60 is operative such that when one o~
said first and second operating chambers 51, 52 is
being supplied via supply line 61 with operating ~luid
55, the respective other one of the operating chambers
52, 52 is being evacuated via evacuation line ~20
Successive switching operations oi the operating
switching means 60 thereby e~ects reciprocation o~
~2
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the connection means 30 and also thereby the
dispensing of measured quantiti~s O:e liquid additive
from the dosing chamber 11~ The operating switching
me~ns 60 is fluid actuated, i~e the pressure in
- 5 control lines 819 82 ~to be further described)
controls the position of the slide or spool valve
therein. A pilo-t switching means 70 is me¢hanically
associated (as will be ~ur-ther describecl~ with the
reciprocating connection means 30. The pilot switching
means 70 is operatively coupled by ~luid couplings via
lines 81 to 85 to the operating switching means 60.
The pilot switching means 70 and the operating switching
means 60 are operable such that9 at the end of each
stroke of the reciprocatlng connectio~ means 30~ the
operating switching means 60 is actuated to change the
supply o~ operating fluid 55 from one to the other of
the ports 53, 54 and hence ~rom one to the other of
the operating chambers 51, 52.
The operating chambers 51, 52 are defined by an
operating head 90 which, as is evident from the drawing,
is in two parts 91~ 92 bolted together at 93 to clamp
the diaphragm means 40 (o~ the second displaceable
member) abou-t its periphery~ The two operating head
parts 9i, 92 are ~ormed so as to define the chamber 50
therebetween which is partitioned into operating chambers
51, 52 by the diaphragm means ~0. Diaphragm means 40
is itsel~ provided with stiffening discs 41 maintained
in clamped attitude by locking means ~2 threadedly
engaged with one portion 32 o~ the connection means 30.
In addition head parts 91~ 92 are ~ormed to define
passages 95; 96 which at their outer ends are threadedly
engaged by connecting pieces 97, 98. These connecting
pieces 97, 98 couple lines 63, 64 to the operating
head 90 and also define the aforesaid openings 53, $4.
~2~6~71
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In addition part 91 is provided with a passage 94
which accommodates a guide pieoe 99 in threaded
engagement therewith. Guide piece 99 guides the
connecting means 30 in the head part 91. 0-ring
seals 18 are located in passage 94 to co-operate
with guide piece 99. It will be appreciated that as
shown head part 92 has a recess axially aligned with
the passage 94 to accommodate the end 37 of the
connection means 30 on its rightward travel (as seen
in the dra~ing). It should be appreciated from the
aforegoing generalised comments concerning a "duplex"
pump, that for such a pump the operating head part 92
would also have a passage 94 extended through the outer
wall thereof to accommodate its respective connection
means 30 for another dosing head 20 (not shown).
The connection means 30 includes piston rod means 31,
32 connected respectively to the displaceable members
20, 40 (i.e. the piston and the diaphragm). As shown
the piston rod means 31, 32 are associated with a main
piston rod part 33~ Part 33 is directly connected with
piston rod means 32 and thereby the diaphragm means
tsecond displaceable member 40). Part 33 is connected to.
piston rod mears 31 by means o~ a lost motion coupling
including members 34, 35. By the setting of member 35
relative to the part 33 so the degree of lost motion will be
determined. It will be seen that the forward end 36 of the
part 33 enters an axial cavity in the part 31, this ensures
that the end 36 is supported at all times. However, as
3~ the part 33 advances to the left (in the drawing) no motion
of the part 31 (and hence piston or first displaceable
-member 20) occurs until member 35 abuts member 34
of the lost motion coupling. It will be seen that the
member 35 is threadedly engaged at 38 with the part 33
whereby the degree of lost motion may be varied. In
this way the ~olume of additive dispensed by the
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dosing head 10 on each ao-tuation thereof is adjustable.
By varying the posi$ion of the member 35 relative to
the part 33, the effective stroke of the connection
means ~0 is adjusted.
As can be seen, the lost motion coupling formed by
members 34~ 35 is associated with ca,libration means
comprising a threaded member 111 threadedly engaging
a threaded passage in the member 34 and ~reely
displaceable with respect to an associated passage 112
in the mem~er 350 This member 111 carries a pair of
calibration discs 113, ~14. On part ~3 of the connection
means 30 is calibrated marker piece 115 which is
threadedly engageable therewith at the threaded portion
38. l'he disposl-tion o~ the calibra-tion discs 113, 114
relative to the oalibrated marker piece 115 enables
the dosing capacity of the dosing head 10 to be read
off for each o~ a series of adjustments o~ the lost
motion coupling (349 35),
It will be observed that the dosing head 10 accommodates
the piston or displaceable me~ber 20 in the cavity therein
11. It will be no-ted tha-t dosing head 10 is bolted at
122 to a framework 120 which is connected to -the
operating head 90 by further bol-ts 121. Within dosing
head 10 are passages which are threaded to accommodate
the members 16, 17 incorporating the non return valves
15. It will be noted that O-ring seals 18 seal the
joints between members 16, 17 and the dosing head lV~
~0 Likewise, within the chamber 11 the piston 20 carries
piston rings 21 to ensure a seal with respect to
chamber llo Piston 20 is guided by guide piece 29.
llhe fluid aotuated switching means 60 is a spool valve
or slide valve. It is actuated under fluid control by
~L2~4~7~L
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the pilot switching means 70. As can be seen the
pilot switching means 70 has a spool 77 (i-t could be
a slide). The position of this spool 77 (which is
determined as will be ~urther described) determines
the internal condition o~ said pilot switching means 70.
~his internal condition determines whether pilot
pressure ~luid issues from port 71 or port 72 an~ thus
enters switching means 60 via a respective one of lines
81, 82. When the pilot pressure fluid is applied
. 10 along line 81, the internal condition of the switching
means 60 is such that the operating -flu-ld 55 passes to
line 63 and thence operating chamber 51, whilst pressure
~luid in chamber 52 is permitted to be e~acuated slnce
line 64 is now in communication with evacuation line 62.
However, when switching means 70 changes its internal
condition7 the pilot fluid pressure is then applied
along line 82. This causes the inte~nal condition o~
switching means 60 to change state~ In consequence
line 64 is connected to the line 61 so that chamber 52
is pressurized, whilst chamber 51 is evacuated as line
63 is now coupled to evacuation line 62. Thus the
co~dition o~ thc pilot switching mean~ 70 controls the
application o~ pilot operating ~luid from said pilot
switching means 70 to the switching means 60 and thereby
the selection of which o~ the first and second operating
chambers 51, 52 is supplied with operating ~lui~ 55~
The pilot switching means 70, which is also a spool or
slide valve, is itself mechanically actuated -to change
state at each end of each stroke o~ the reciprocating
connection ~eans 30. The spool 77 (it may be a slide)
is acted upon by s-tops 1~1, 132 arranged to contact,
and displace, a respective end of spool 77 at the
transition point in the movement of connection means
30. Stop 131, which in this embodiment is ~ormed by a
67; ~
bolt, is carried by the lost motion coupling member 35
and is adjustable relative thereto, whereby the switch~ng
point may be adjusted. Stop 132 is carried by a member
133. Member 133 is slideably mounted on ths connection
means part 33 and adjustably securecl thereto by
fastening means 134. Since the position o~ member 133
relative to part 33 m~y be adjusted, as ma~ ~ember 132
relative to member 133~ it ~ollows that the switching
point of the switching means 70 may also be adjusted or
tuned relative to the respective transition or end of
stroke of the connection means 30. As stated, direct
contact of the spool 77 with one of the stops i31 or
132 causes the position of spool 77 to change wi-th
respec-t to the housing thexeof, In conse~uence the
condition of the swi-tching means 70 changes with the
resultant change of pilot pressure fluid between the
lines 81~ 82 ~as described above). It will he noted
that pilot switching means 70 has ~ive ports 71 -to 75
communicating with lines 81 to 85. I.ines 81, 82 have
~een explained. Line 85 is the pressure -fluid supply
line and is connected to the main supply line 610
Lines 83, 84 are the exhaust lines for exhausting as
appropriate a respective one of lines 81, 82 when the
other of those lines is pressurised, and these lines
83, 84 are connected to the main evacuation line 62.
