Note: Descriptions are shown in the official language in which they were submitted.
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'ICASTING APPARATUS"
The invention relates to a casting apparatus
and in particular to a way of mounting parts of the
casting apparatus together. -
The casting of low melting point alloys is of
increasing importance. Such alloys are often cast to
form complex metal cores for use in moulding plastics -
material; the plastics material being moulded about
the metal core and the core subsequently removed by
melting the metal alloy.
In our copending European Patent Application
No. 90301038 we describe casting apparatus for
supplying molten metal to a die which comprises a
cylinder with a piston mounted therein for ;
reciprocating movement to fill and deliver molten
metal from the cylinder, connection means for
connecting the cylinder to a supply of molten metal
and to a die the connection means being provided with `
valve means to open and close the connection means
between the cylinder and the supply and between the
cylinder and die. In a preferred embodiment the
valve means is a ball valve having a first port for
communication with the supply of molten alloy, a
second port for communication with the cylinder, and
a third port for communication with the die. In this
way the valve may be operated to open the connection ~ ~
between the supply and the cylinder to fill the i
, ~ cylinder with metal on retraction of the piston while
maintaining the connection between the cylinder and
the die closed and then adjusted to close the
connection between the supply and the cylinder and
open that between the cylinder and the die to permit
~etal to be dispensed into the die on the forward
stroke of the piston.
The whole arrangement of cylinder, piston,
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connection means and valve means is usually mounted
submerged within a tank of the molten metal. This
not only provides molten metal at the supply port of
the valve but also ensures that all of the apparatus
is surrounded by molten metal and is thereby
maintained at an even temperature: this reduces the
likelihood of local solidification of metal or
variations in alloy composition.
However, the need to surround the apparatus
with molten metal leads to difficulties in -
maintaining the apparatus. Normally the cylinder and
valve are bolted on a side wall of the tank. The ~ ~
cylinder must be positioned very accurately to align ~ ~-
with the cooperating piston and its operating means
which is mounted overhead on the machine frame. The
cylinder is fixed at its lower end onto a block which
is bolted rigidly to the valve body. The valve body
is attached to the tank wall by bolts passing through
holes in the tank wall from the outside into
receiving threaded holes in the valve body which
bolts ars then tightened or released from outside.
Often further pieces of apparatus are bolted on to
the outside wall of the tank over the heads of the
bolts for the cylinder or valve mountings.
While such an arrangement keeps the bolts out
of the tank of molten metal and can locate the ;~
cylinder and valve firmly and accurately it has ~ ;
several drawbacks. '
, I , It is necessary to be able to remove the
cylinder and valve for maintenance and repair
purposes. With the conventional arrangement the tank ~
must be drained so that the cylinder and valve can be ;
removed from their mountings and lifted out of the
tank and this involves considerable downtime. There
are also many bolts to be undone in diverse places
and often other components must be removed to gain - ~
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access to those bolts. This all means that removal
of the cylinder and valve for routine maintenance or
repair is time consuming and costly.
It is also known from GB-2063127 to provide
S casting apparatus comprising a tank receiving molten
metal in use, a housing comprising a dispensing
cylinder and a valve means in communication with the
cylinder, locating means for removably locating the
housing in the tank, a dispensing port, connection
means defining a passageway between the valve means ;
and the dispensing port, the connection means
includi~g a releasable couplinq through which the
passageway normally extends and having first and
second parts which are separable to facilitate
removal of the housing, the first and second parts
being connected to the dispensing port and the valve
means respectively and being relatively swivelable to
allow adjustment of the housing relative to the tank.
A disadvantage of this arrangement is that air
may enter the connection means when the coupling is ;
released to allow removal of the housing.
According to the present invention the casting
apparatus is characterised in that the first part of
the coupling is mounted on an internal surface of the
tank beneath the normal level of molten metal in the
tank.
Preferably the first part of the coupling
comprises a domed projection which projects upwardly
from a bottom surface of the tank and the second part
of the coupling comprises an annular seat through
which the passageway communicates with the valve
means. The coupling is therefore in effect a ball
and socket coupling allowing three-axis adjustment of
the housing position relative to the tank. An
advantage of such an arrangement is that the domed
projection also assists in locating the housing
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relative to the tank during reassembly.
Preferably the apparatus includes clamping
means operable to clamp the housing in position
relative to the tank, which clamping means includes a
compliant mounting facilitating limited movement of
the housing.
An advantage of such an arrangement is that the
compliant mounting functions to relieve stress
resulting from expansion or contraction of metal in
the tank in the event of solidification occuring.
Preferably the clamping means comprises spring
means operable to bias the housing in a downward
direction towards the bottom surface of the tank.
Such spring bias is needed to counter the upward pull
created by suction in the cylinder when the piston is
raised to recharge the cylinder. The spring bias is ;
also necessary to counter the tendency for the
casting apparatus to float when immersed in molten ~
metal o~ greater density than the components of the ;;
apparatus. The spring bias also ensures complete
sealing between the domed projection and the seat ~
which together comprise the coupling. ;;
Preferably the clamping means comprises at ;
least one rod connected to the housing and extending
upwardly so as to project above the normal level of ~
molten metal in the tank and a frame fixed to the ~ ;
tank and overlying the housing, the spring means
being operable between the frame and the rod so as to
downwardly bias the rod. An advantage of such an
arrangement is that the clamping means can be ;
actuated and adjusted externally of the molten metal
within the tank. '
Conveniently the locating means comprises a ~,-
plurality of pegs projecting downwardly fro~ the
housing to an adjustable extent and engaging
cooperating holes provided in bosses pro;ecting ;~
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upwardly of a bottom surface of the tank. The
attitude of the housing relative to the tank can be
adjusted by adjusting the extent to which the pegs
project. It is important to ensure correct
alignment of the piston and cylinder when the piston
is actuated from an actuating mechanism mounted on a
frame overlying the tank.
Advantageously the connecting means comprises -
an outlet pipe extending between the first part of
the coupling and the dispensing port and wherein the
outlet pipe passes through the tank such that the
passageway defined therein is located beneath the
normal level of molten metal within the tank. This
arrangement ensures that the outlet pipe is
maintained at the temperature of molten metal within
the tanX and also ensures that positive liquid
pressure exists within the passageway so that the
likelihood of air being drawn into the passageway is
reduced.
Preferably the housing comprises a mounting
block extending horizontally in use, the dispensing
cylinder being connected to one end of the mounting
block so as to extend vertically upwards therefrom
and the valve means being connected to the other end
of the mounting block, the mounting block being
provided with a horizontally extending conduit
communicating between the cylinder and the valve
means.
Preferably the valve means has a first port for
communication with molten metal in the tank, a second
port for communication with the cylinder via the
connecting means and a third port for communication
with the dispensing port. For example, a 3-way ball
valve such as that described in our copending
European Patent Application No 90301038 may be
employed or a 3-way plug valve may be employed such -
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as that described in United States pending patent
application No. 268492 filed 8th Nove~ber 1988.
The invention will now be described by way of
example with reference to the accompanying drawings ~;
in which~
Figure 1 is a sectional view through casting
apparatus according to the invention;
Figure 2 is a staggered cross-sectional view
through the apparatus with the left hand side taken
on direction A-A of Figure 1 and the right hand side
taken through line B-B of Figure 1. For clarity many
details have been omitted from this drawing;
Figure 3 is a plan view of the mounting block
of the apparatus of the invention. Again many ~ -~
details have been omitted for clarity; -;-~
Figure 4 is a cross-section through the ~
compliant mounting means for the clamping means along ~ ;
line C-C' in Figure 3; and
Figure 5 is an end elevation of an alternative
casting apparatus having a modified clamping means.
Referring to Figures 1 to 4, the casting
apparatus indicated generally by 1 is suitable for ~;
casting metal alloys having low melting temperatures -~
for example having solidus temperatures in the range ~; -
of 35 to 300C. The apparatus 1 has a tank 2 to
hold molten alloy 3 with its normal level shown as ~,
3a. The tank 2 is insulated so that the alloy 3 may ;
be maintained in its molten state. Within the tank 2
and immersed in the molten alloy 3 is a cylinder 4 , ~
and cooperating piston 5. The piston 5 may be ~-
hydraulically, pneumatically or otherwise operated.
The cylinder 4 is mounted so as to extend upwardly ~
from a rear end 50 of a horizontally extending ~-
mounting block 11. A valve indicated generally by 8 ;
is mounted within a front end 51 of the mounting ~ ~
block 11. The cylinder 4, mounting block 11 and ~ ~;
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valve 8 are normally bolted together as a single unit
or housing 73.
The cylinder 4 has a lower end plate 52 in
which is formed an opening 6 which opens into a
conduit 7 which communicates with the valve 8. The
conduit 7 extends horizontally through mounting block
11. The opening 6 acts as both the inlet and the
outlet of the cylinder 4 and is situated so that it
is below the piston 5 at all times during operation.
The illustrated valve 8 is a 3-port ball valve
which may be hydraulically, pneumatically or
otherwise operated. The 3-port ball valve 8 has a
ball 9 mounted on a lower end 5~ of a vertically
extending stem 54 and located between seats 38 and
39. The valve 8 is provided with an upwardly
directed fir5t port 55 which is open to the molten
alloy 3 within the tank 2, a laterally located second
port 56 which opens to the connecting means 7 and so
i9 in communication with cylinder 4 and a downwardly
directed third port 57 which is in communication with
the dispensing port 10 via a releasable coupling 59,
61 (described below) and a pipe 80 defining a
passageway 81. Normally the dispensing port 10 will
be connected to a die (not shown) ~ia a flow valve
(not shown) which may be operated by a rotary
actuator. The dispensing port 10 is positioned just
below the normal level 3a of the molten metal 3.
This is to ensure that positive pressure always
exists in the passageway 81 so that air bubbles are
not drawn back into the apparatus during operation by
the presence of any leakage.
The movements of piston 5 and valve stem 54 are
controlled, ~or example by electrical control means,
so that they cooperate together to dispense molten
metal from the tan~ through the dispensing port 10.
The piston 5 and stem 54 are detachable from their
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respective operating means so that the dispensing ~;
cylinder, ball valve and mounting block can be
removed from the tank.
During assembly of the casting apparatus 1,
both the cylinder 4 and the valve 8 are secured to
the mounting block 11 with the cylinder 4 being
mounted so as to extend upwardly from the block and
the valve 8 forming a horizontal extension of the
mounting block. The mounting block 11 is then
located on the base plate 60 of the tank 2 via rear
and front location means 12, 14 respectively and -~
secured by clamping means 13. The location means
consist of rear, and front means indicated generally
by 12 and 14 respectively. The clamping means are ` ;
indicated generally by 13. The location means 12 and
clamping means 13 are more clearly illustrated in
Figures 2 and 3.
From Figure 3 it can be seen that there are two
rear location means 12 one on either side of the
mounting block 11 and similarly two clamping means 13
one on either side of the mounting block. There is
only one front location means 14. Figure 2 is a
staggered cross-section which on the left hand side -
cuts through rear left location means 12 and on the ~ ~
right hand side cuts through right clamping means ~ ;;,
13. The corresponding left clamping means 13 which
should appear in the left hand side of Figure 2 has -
been omitted for clarity. ~
, Rear location means 12 consists of support 16- ;
protruding laterally from the rear end 50 of the ~-
mounting block 11 and is provided with a threaded ~
vertical bore 58 through which passes a cooperating ~ -
threaded screw 17. A smooth pe~ 18 forms a downward ,,
projection of the screw 17 which is of narrower ;~
cross-section than the rest of the screw. The peg 18
is normally received within a cooperating hole 20 in
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a boss 19 which is fixed to and projects upwardly
from a horizontal base plate 60 of the tank. The
rear of the mounting block 11 is thus located both
vertically and laterally by the rear location means
S 12.
The front location means 14 consists of a domed
projection 59 having a generally spherical domed
surface 15. The projection 59 projects upwardly
from a bottom surface 82 of the tank 2 defined by ~ .
the base plate 60 and is provided with a vertically
extending passage 30 therethrough. The passage 30 is
aligned with port 57 of the ball valve 8 to provide
communication between the valve and the dispensing .
port 10. The ball valve 8 is provided with an
annular seat 61 which sits on the top of the domed : .
projection 59 and seals therewith.
The projection 59 and the annular seat 61 are
relatively swivelable whilst continuing to provide
communication between the passage 30 and the port 57
20 so that the orientation of the housing 73 relative to
the tank 2 is possible. The projection 59 and
annular seat 61 are separated when the housing is
removed from the tank 2 and thereby constitute a
releasable coupling 59, 61.
The clamping means 13 consists of a support 21
which projects horizontally on each side from the
middle of the mounting block ll and which is provided
with a smooth vertical bore 62 through which passes a
, I j vertical clamping rod 22. The clamping rod 22 has a
30 threaded lower end 23 which cooperates with a
threaded boss 24 which is mounted through a ccmpliant
mounting means 43 to the base plate 60 of the tank
2. The clampin~ rod 22 i5 also provided with a
collar 2S which is wider than the bore 62 in the
35 support 21 so that it limits downward movement of the
rod 20. A second collar 41 on the clamping rod is
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spaced beneath the suppoxt 21 and limits upward
movement of the rod 22 relative to the support. The
upper end of the rod 22 is provided with a hexagonal
head 63 to facilitate turning of the rod 22 to screw
or unscrew the rod 22 in the boss 24.
The compliant mounting means 43 accomodates ~ `
local strains caused by solidification or melting of
alloy 3 beneath the mounting block 11. Some alloys,
for example bismuth alloys expand on solidification
and this can produce local strains underneath the
mounting block 11. Alloys which contract on
solidification can also cause strain on remelting.
The compliant mounting means 43 permits the mounting
block 11 to rise or fall slightly in relation to the
base plate 60 of the tank 2. Thus the boss 24 into `
which the clamping rod 22 is screwed is welded to the
centre of a rectangular horizontal metal plate 64
provided at each end with a downward extension 44
through which a smooth bore 46 has been drilled. The
plate 64 is then fixed to the base plate 60 of the
tank 2 by two screws 45 which pass through the smooth
bore and then screw into the tank base. The plate 64
and extensions 44 constitute the compliant mounting
means 43. The metal plate 64 has some inherent ~;
flexibility enabling boss 24 to move up and down ',
relative to the tank base plate 60.
A loop 40 is connected in an upwardly extending
position to the mounting block 11 so that a long rod
(not shown) with a hook on the end may be hooked
through the loop to lift the mounting block from the ,,
tank. ,
At start up, before the tank 2 is filled with ;
molten alloy 3, the mounting block 11 complete with
dispensing cylinder 4 and ball valve 8 secured
thereto is lowered into the tank so that the two pegs ~- ;
18 rest in the hole~ 20 of the two bosses 19 and the
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annular seat 61 of of the ball valve 8 around the
port 57 rests on the domed surface 15 of projection
59. The screws 17 may then be screwed up and down
and the mounting block 11 tilted on the domed surface
15 until the dispensing cylinder 4 and piston 5 are
correctly aligned to connect the operating means.
The presence of both the screws 17 and the domed
sur~ace 15 provides great flexibility in the
positioning of the mounting block 11 and facilitates
very accurate positioning. Once the screws 17 have
been adjusted to the correct position they need not
again be altered and may be fixed in position by
means of lock nuts 42 The mounting block 11 can then
be removed from the tank 2 and returned without need
lS for further adjustment of screws 17.
Once the positioning of the mounting block 11
has been correctly aligned it can be clamped in
position by means of the clamping means 13. The two
rods 22 are screwed into the corresponding bosses 24
with the aid of a hexagonal socket and extension bar
(not shown) inserted from above. The mounting block
11, dispensing cylinder 4 and ball valve 8 are then
all held ~irmly in position.
Piston 5 and valve stem 9c are then connected
to their respective operating means (not shown).
The tank 2 is then filled with molten alloy to
its normal level 3a and the metal dispensed by
operation of the piston 5. Initially the piston 5 is
in its up position and the cylinder 4 is full of
moltén alloy 3. In operation the control system
actuates the piston 5 so that it begins to move
down. The speed of the piston is controlled by the
control system. As the piston 5 starts to move down
the control system also actuates the 3-port ball
valve 8 so that the second and third ports 56 and 57
are open and in communication with one another. The
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first port 55 is closed, closing the supply of molten ~ `
alloy 3 from the tank 2 to the cylinder 4. As the
piston 5 continues to move down molten alloy 3 is
forced from the cylinder 4 along the connecting means
S 7 through the second port 56 and out through the
third port 57 to the dispensing port 10 from which it
is dispensed to a die. Once this dispensing stroke
of the piston 5 is complete, the control system
operates the ball valve 8 so that the third port 57
is closed and first and second ports 55 and 56 are
open and then retracts the piston 5 so that the
molten alloy 3 is drawn from the tank 2 through ports
55 and 56 along the connecting means 7 and into the ~ ;
cylinder. The ball valve 8 is then again actuated to
close port 55 and open ports 56 and 57 so that molten
alloy can once again be dispensed. `
After many cycles it will be necessary to ;~,,
remove the ball valve 8 for maintenance or repair. ;
With the casting apparatus 1 of the present invention
this is a very simple procedure and there is no need `~
to drain the tank 2 fully. The level 3a of metal ;
alloy 3 is allowed to drop below the dispensing port ; ;
10 to level 3b so that, when the dispensing cylinder ,
4 and valve 8 are disconnected metal alloy can not
syphon out through the dispensing port 10. Then one ; `~
simply unscrews the rods 22 with the aid of a :
hexagonal socket so as to unclamp the mounting block
11. One also uncouples the piston 5 and stem 54 from
their~respective operating means. A long rod with a
hook on the end is then lowered into the molten metal ,
and hooked beneath loop 40. Then when the rod is `
pulled vertically upwards the mounting block together
with the attached dispensing cylinder 4 and ball
valve 8 is removed in one piece from the tank~ The
mounting block 11, dispensing cylinder 4 and ball
valve 8 can then be cleaned and examined for
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maintenance and repair purposes. When it is desired
to return the mounting block 11 to the tank 2 it is
simply necessar,v to lower the mounting block back
into the tank using the rod hooked around the loop
40. The mounting block must be carefully positioned
so that the pegs 18 on the bottom of screws 17 drop
into the holes provided for them in the bosses l9
mounted on the base plate 60 of the tank 2. The
other end 51 of the mounting block 11 will then sit
on the domed surface 15 of projection 59. It then
remains only to lower the clamping rods 22 onto the
bosses 24 and then to screw them up so that the
threaded ends 23 bite on the threads provided in the -
bosses 24 mounted on the base plate 60 of the tank 2.
It will be appreciated that this provides a
very quick and simple way of removing both the
cylinder 4 and the valve 8 from the tank 2.
A further advantage of the apparatus of the
present invention is that it enables one easily to
substitute a dispensing cylinder of one diameter for
a dispen3ing cylinder of greater or lesser diameter.
one normally choose3 the diameter of the cylinder 4
and the cooperating piston 5 according to the
quantity of the metal alloy 3 which one wants to
dispense. Because with the prior art mounting
arrangements it was so cum~ersome to remove a
dispensing cylinder from a tank, changing to a
dispensing cylinder of a different size has
previously involved a large amount of downtime and
loss of production. With the casting apparatus 1 of
the present invention it is much more simple to
remove the dispensing cylinder 4 and this can easily
ke substituted for one of a different size. The
different cylinder could be mounted to the same
mounting block 11 in place of the original cylinder 4
or a separate mounting block assembly and cylinder
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could be substituted for the original mounting block
assembly and cylinder.
If desired, one may even use an alternative
mounting block (not shown) which has two dispensing
cylinders mounted on it for operation by two separate
operating means and which both dispense into the
connecting passage 7.
Additional compliance of the compliant
mounting means 43 may be provided by placing a coil
spring or stack of disc springs between the head of
each screw 45 and the metal plate 64 thus enabling
the metal plate to move upwardly when subjected to a
force sufficient to compress the springs.
An alternative casting apparatus 70 is shown in
Figure 5 and will now be described using
corresponding reference numerals to those of ;
preceding Figures for corresponding elements where
appropriate.
The alternative casting apparatus 70 differs
from the casting apparatus 1 of Figures 1 to 4 in
that it includes a modified clamping means 71. The `
clamping means 71 includes a frame 72 rigidly
connected to the tank 2 and extending above the
normal level 3a of alloy 3 so as to overlay the
housing 73.
Horizontally extending supports 21 project from
opposite sides of the mounting ~lock 11 of the
housing 73 and each support is bored vertically to
receive a vertically extending clamping rod 22.
Each clamping rod 22 has a tubular upper end portion
74 to which is welded a lower boss 75. A screw-
threaded bolt 76 projects downwardly through the
frame 72 to an extent which is adjustable by screw
action and has a downward pro~ecting spigot 77 of
smaller diameter received as a loose fit within the
tubular upper end 74.
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An upper boss 78 is a sliding fit on the spigot - .
77 and a coiled compression spring 79 is located
between the upper and lower bosses 75 and 78. Since
the frame 72 is fixed the rods 22 are biassed
downwardly by the compression springs 79 and this
bias is communicated through the supports 21 to
downwardly bias the housing 73. This bias ensures
sealing engagement between the domed surface 15 and
the annular seat 61 of the valve 8. Adjustment of
the orlentation of the housing 73 relative to the
tanX 2 is possible by adjusting the rear locating
means such that the annular seat 61 swivels relative
to the domed projection 59 with corresponding tilting
of the hou~ing 73. The rods 22 are received as a
loose fit within the supports 21 such that tilting of
the housing 73 during adjustment results in minimal
lateral movement of the upper ends 74. The loose
fit of the spigots 77 within the upper ends 74
accommodates sufficient tilting of the rods 21 during
such alignment.
The frame 72 is rigidly bolted to the tank 2.
When it is required to remove the mounting block 11
from the tank together with the valve 8 and cylinder
4 then the bolts 76 are unscrewed to lift the spigots
77 clear of the springs 79 to uncouple the rods 22.
The mounting block 11 together with the cylinder 4
and valve 8 float to the surface of the alloy 3 and .
can be easily removed.
. I f A *he mounting block 11 is l.ifted clear,of the
domed projection 59 the passage 30 in the projection
com~unicates directly with the molten metal 3 in the ~;
tank 2 so that no air is admitted to the pipe 80. ;
The housing 73 can subsequently be replaced or an
alternative housing located in the tank without there
3S being any risk of introducing air into the pipe 80.
During insertion of the housing 73 into the
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tank 2 the domed projection 59 facilitates location
of the housing as well as the left and right rear
locating means 12.
The springs 79 and upper and lower bosses 78
and 75 respectively provide compliant mounting means
for the housing 73 such that the housing can be ,
lifted away from the bottom surface 82 if sufficient ;~
pressure is applied for example by virtue of metal ;
between the bottom surface and the housing ~;~
solidifying and expanding. Such compliant mounting
means 75, 78, 79 thereby prevent damage from
resulting which might otherwise occur if for example
the housing were bolted rigidly to the tank 2. The
pressure exerted by the springs 79 is however
adjusted such that sufficient downward force is
applied not only to prevent flotation of the housing
73 but also to resist lifting of the housing due to
upward movement of the piston 5 which creates suction
within the cylinder 4 in order to recharge the
cylinder with molten metal.
The alternative casting apparatus 70 also
includes rear locating means 12 as described with
reference to the apparatus 1 and as shown in the left
half of Figure 2. Details of the rear locating ~ ;
means 12 are omitted from Figure 5 for clarity.
The coupling may alternatively comprise a domed
projection extending downwardly from the housing and
locatable in an annular seat formed in the tank.
i 30
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