Note: Descriptions are shown in the official language in which they were submitted.
~4~7~
This invention relates to a method and apparatus for
metering the delivery of liquids, particularly in small
quantities and at high rates. The invention is particularly
applicable to the metering o~ fuel to an internal combustion
engine, however it will ~e readily appreciated that there are
other applications ~or the invention. E~amples of other
applications are the metering of additives or reaction agents
in industrial processes, such as chemical processes. However,
for convenience, the invention will now be specifically des-
cribed and illustrated with reference to its application to
metering fuel to an internal combustion engine.
The advantages of metering fuel to an engine by an
injection system as compared with a carburation system are
well recognised. Because of the improved control over the
quantity of fuel delivered to the engine achieved by fuel
injection systems, a lower specific fuel consumption is
achieved together with an increased power output. Also
fuel injection systems result in a lower pollution level in
the exhaust gases from the engine and improved starting and
2Q acceleration characteristics of the engine.
~lthough there are known a number of effective fuel
injection systems, the carburettor is still the preferred
mea~s of metering the fuel to the engine as it is cheaper to
manufacture and less expensive to maintain, partly because it
is primarily a low pressure device. The high pressure
encountered in fuel injection systems require high precision
in the sizing and surface finish of many components, particularly
in ~uel pumps and metering devices, together with hiyh precision
and quality in seals between moving parts. In known fuel
injection systems the injection is usually achleved by mechanical
mechanisms, such as pistons moving in cylinders, and in view of
the high pressure required to inject the fuel the forces involved
are correspondingly high, and thus absorb signi~icant energy
and require materials and surface treatments to reduce wear.
There has been proposed in United State~ Pa-tent No.
3,698,368 a fuel injection system for two-cycle engines,
however it is not known that this system has been proved
~4'~
comrnercially successful. In several embodiments of this
system described in the United States patent specification a
rigid piston is employed and thus these embodiments exhibit
the general disadvantages discussed hereinbeore.
In one embodiment a diaphragm pump is used and the
suction stroke of the pump varied in order to meter the quantity
of fuel delivered. It is believed that the inherent high
flexib~ity of a diaphragm would operate against the attain-
ment of accurate metering of the fuel.
In view of the relatively high costs of manufacture of
known fuel injection systems they are currently not used on
the more popular makes of motor vehicles in the high volume
low cost catagory. However, in view of the increasing require-
ments for low pollution levels in exhaust gases, it would be
desirable to incorporate fuel injections systems on all motor
vehicles, provided this could be done at a reasonable cost.
It is therefore the principal object of the present
invention to provide a method and apparatus for metering
liquids, such as metering fuel to an internal combustion engine,
which is e~fective in operation, does not require high
precision manufacturing tolerances and finishes, and is
therefore relatively inexpensive to manufacture.
With this object in view there is provided a method of
delivering a metered quantity of liquid comprising ~illing
a chamber with liquid, admitting gas to the chamber at a
pressure sufficient to displace liquid from the chamber upon
selective opening of a discharge port in the chamber, and
controlling the quantity of liquid displaceable from the
chamber by the admission of the gas to regulate the quantity
of liquid delivered.
In order to maintain accuracy and repeatability of the
metered quantity of liquid displaced from the chamber it is
important to ensure that the chamber is filled completely with
the liquid prior to the admission of the gas. Furthermore,
~fter the displacement of each metered quantity of liquid it is
important that the chamber is purged of residual gas before the
7~a
delivery of the next metered quantity of liquid.
Conveniently the liquid is circulated through the chamber
so that all gas is expelled from the chamber prior to
commencement of a delivery cycle, and when delivery of the
liquid i.s required~ circulation is terminated ancl the
chamber is sealed filled with liquid.
More specifically there is provided a method of delivering
a metered quantity of liquid comprising circulating liquid
through a chamber to establish and maintain the chamber fille~
with liquid, terminating said circulation at intervals, admitting
gas to the chamber during said termination of cixculation at
a pressure sufficient to displace liquid from the chamber upon
selective opening of a discharge port in the chamber, and
controlling the quantity of liquid displaceable from the
chamber by the admission of said gas to regulate the quantity
of liquid delivered.
The quantity of liquid displaceable by the admission of
the gas may be controlled by varying the relative positions
of the entry of the gas to the chamber and ~e discharge of the
liquid from the chamber. It will be appreciated that when the
gas is admitted to the chamber essentially only that liquid
between the levels of the gas entry and the liquid discharge
port will be displaced by the incoming gas and that liquid
outside the space between the levels of gas ent.ry and the
liquid discharge is essentially not removed.
The admission of the gas to the chamber est~blishes
an interface between the gas and the liquid over the cross-
section of the chamber. This interface moves along the chamber
from the point of gas entry towards the point of liquid dis~
charge displacing the liquid in advance of the interface ~owards
the liquid discharge. Upon the interface reaching a location
whereby the liquid is no longer in direct communication with
the discharge point further movement of the interface is
prevented and thus the discharge of liquid ceases.
Alternatively the quantity of liquid discharged may be
controlled by control of the volume of the chamber between the
gas entry point and liquid discharge point and thus these points
~4~7~
may remain Eixed.
With the previously stated object in view there is also
provided apparatus for delivering a metered quantity of
liquid comprising a chamber having a selectively openable dis-
charge port, means operable to supply liquid to said chamber
to fill the chamber with said liquid preparatory to delivering,
means operable to selectively admit gas to the chamber at a
pressure sufficient to displace liquid therefrom upon opening
of the discharge port, and means to control the quantity of
liquid displaceable from the chamber by the admission thereto
of the gas.
More specifically, the invention provides apparatus
for delivering a metered quantity of liquid comprising a
chamber having a selectively openable discharge port, means
to circulate liquid through the chamber to maintain the chamber
filled with liquid, means to terminate said circulation at
intervals, means operable to admit gas to the chamber at a
pressure sufficient to displace liquid therefrom during terminat-
ion of said circulation and upon opening of the discharge valve,
and means to control the quantity of liquid displaceable from
the chamber by the admission of said gas.
Conveniently the liquid is pumped through a closed
circuit incorporating the chamber, and inlet and outlet valves
are provided to temporarily isolate the chamber from the closed
circuit to terminate the circulation through the chamber. The
inlet and outlet valves are located so that the cha~nber is
maintained filled with liquid during circulation. Upon the
inlet and outlet valves being closed they are maintained closed
duxing the admission of the gas to the chamber until the dis-
placement of liquid by the gas is completed.
Conveniently, the chamber is provided with ports for
the gas to enter the chamber and the liquid to be discharged
from the chamber, and one or both of said ports are relatively
movable. The quantity of liquid displaceable from the chamber
by the incoming gas may thus be controlled by movement of one
or both of said ports towards one another to decrease the
quantity displaceable from the chamber, and apart to increase
the quantit~.
_ _
779
The means to control the quantity of liquid displaceable
from the chamber may be manually operated or operated auto-
matically by a preset programme responsive to selected
conditions.
The advantage of this invention is the delivery of the
liquid from the chamber by the admission of gas thereto rather
than by movement of a piston or plunger which must carry a seal
suitable to withstand the high pressure encountered. Such a
seal must also withstand the high speed and high frequency of
operation arising from one power stroke and one return stroke
for each delivery. By the present invention the moving component
is only required to move to effect variations in fuel demand
which are small, infrequent and slow compared with the movement
of a mechanica~ pump piston.
The invention will be more readily understood from the
following description with reference to the accompanying drawings
of a practical application of the method and a practical
construction of the apparatus of the invention. The drawings
and following description are not the only practical forms of
the method and apparatus of the invention and are not limiting
on the scope of the invention.
In the drawings:-
FIGURE 1 is a schematic representation of one practicalapplication of the method delivering metered quantities o~
liquid;
FIGURE 2 is a schematic representation of the method
illustrated in Figure 1 with the addition of a practical arrange-
ment for the controlling of the valves;
FIGURE 3 is a sectional view of a practical arrangement
of the apparatus for deliverir.g metered quantities of liquid;
FIGURE 4 is a fragmental section along line 4-4 in
Figure 3;
FIGURE 5 is an enlarged view of the chamber portion of
the apparatus shown in Figure 3.
FIGURE 6 is a sectional view of another practical arrange-
ment of the apparatus for delivering metered quantities of li~uid.
In the following description with reference to the
accompanying drawings the method and apparatus is considered
' '~
to be applied to a fuel injection system for an internal
combustion engine, however it will be appreciated that it is
equally applicable to any type of liquid which is required
to be delivered in metered quantities or any purpose.
The various components of the system are shown in
Figures 1 and 2 using B.S.I./I.S.O. fluid power symbols.
Referring now to Figure 1 the metering chamber 2 is
defined by a stationary member 1 and a movable member 3 which
is a ~ree fit in ~he bore of the stationary member 1. Fuel
is drawn from the fuel tank 100 by the low pressure fuel
pump 101 and delivered through valve means 102 to the metering
chamber 2 at inlet port 6. When the chan~er 2 is full, excess
fuel flows from the metering chamber 2 through the clearance
between movable member 3 and member 1, out through ou-~let
port 7 and hence through valve means 103 to return to fuel
tank 100. Preferably the seal 104 is located between movable
member 3 and ~tationary member 1 to prevent leakage.
Migh pressure gas is stored in source 105 and is prevented
from flowing into the metering chamber 2 by valve means 106
which is normally closed and gas port 14 in the movable member 3.
Fuel is prevented from flowing from the metering chamber 2
via gas port 14 by the normally closed valve means 106.
Similarly fuel is prevented from flowing out of metering chamber
2 through discharge port 9 by valve means 107 which is normally
closed.
It will be understood that except during the delivery
cycle the metering chamber 2 is maintained filled with fuel
by the pump 101 with the amount of fuel contained in metering
ch~Imber 2 determined by the position of movable member 3
relative to fixed member 1.
To deliver a metered quantity of fuel from the chamber 2,
valve means 102 and 103 are closed so th'lt no further fuel can
enter or leave metering chamber ~ via inlet and outlet ports
6 and 7 respectively. Valve means 106 and 107 are then opened
so that high pressure gas from source 105 enters the metering
ch~mber 2 through gas port 14, and displaces the metered quantity
of fuel in the chamber 2 throu~h discharge port 9 and open valve
7~
means 107 into line 108. Thus the metered ~uantity of fuel
is injected into an appropriate part of the engine. Sufficient
yas must be permitted to enter the metering chamber 2 to
displace the metered quantity of fuel, however the quantity
of gas supplied may exceed this minimum and the excess yas is
discharged through the discharge port 9 with the fuel.
To repeat the cycle, valve means 106 and 107 are closed
and valve means 102 and 103 are opened so that residual gas in
the metering chamber 2 is expelled through port 7 and valve 103
~0 to the vented fuel tank 100, and fuel is again circulated through
metering chamber 2 by the ~uel pump 101 thus filling the chamber 2
with fuel. It is normal for the pump 101 to operate continuously
while the injection device is in use.
The quantity of liquid delivered during each cycle is
controlled by the position of the movable member 3 in the bore
of the stationary member 1 as the gas inlet port 14 is located
at the innex end the movable member 3 and the discharge port 9
at the opposite end of the chamber 2, and thus all the liquid
in the chamber 2 will be displaced on the admission of the gas
through port 14.
However it is to be understood that if the discharge
port 9 is located in the wall of chamber 2 spaced from the end
of the chamber the quantity of liquid discharged through the
port 9 is determined by volume of liquid in the chamber between
the gas inlet port 14 and the discharye port 9. In both these
arrangements the quanti-ty of fuel delivered each cycle is
controlled by the position of the movable member 3O It is also
to be understood that the positions of the discharge port 9
and gas inlet port 14 may be interchanged whereby the discharge
port is disposed in the movable member 3 and the gas inlet port
is disposed in the stationary member 1.
The valve means 102, 103, 106 and 107 described with
reference to Figure 1 may be actuated to change from the
metering position to the delivery position by applying thereto
a pneumatic signal transmitted from the control valve means 109
in timed relationship to the engine cycle, as indicated in
Figure 2. Upon activation of the con-trol valve means 109 hiyh
g _
: .
7~9
pressure gas is applied to each of the ~alve means 102, 103,
106 and 107 to open valve means 106 and 107 and close valve
means 102 and 103 to change their positions from the metering
to the delivery positions. Upon return of control valve means
109 to its original position~ the gas pressure in the control
lines to valves 102, 103, 106 and 107 is vented
and valve means 102 and 103 open while valve means 106 and 107
are closed.
It will be understood that some of the valve means
referred to in the preceding description with respect to
Figures 1 and 2 may be in the form of check valves.
One practical arrangement of the apparatus will now be
described with reference to Figures 3, 4 and 5, in which
components corresponding to those referred to with respect
to Figures 1 and 2 are designated by the same reference numeral.
The apparatus comprises a body 1 having a metering
cavity 2 formed generally centrally therein. Four independent
ports co-operate with the metering cavity 2, namely fuel inlet
port 6, ~uel outlet port 7, gas port 14 and discharge port 9.
The fuel inlet port 6 communicates with fuel passages 4 and 5
with the passage 4 adapted at the face of the body 1 to be
connected to a fuel supply, such as a low pressure pump
del~ering fuel from a storage tank. The fuel outlet port 7
communicates with the fuel passage ~, which is again adapted
at the face of the body 1 for connection by a conduit to the
fuel storage. Thus when the ports 6 and 7 are open, fuel
may be circulated from the storage tank through the metering
cavity 2, enteriny the cavity via the passages 4 and 5 and the
port 6, and leaving the cavity by the port 7, and passage 8.
The fuel inlet port 6 and fuel outlet port 7 are
controlled by respective valve elements 22 and 27 operated by
identical control mechanisms. The valve elements 22 and 27
are connected to the ends of rods 21 and 26 respectively, which
at their opposite ends are connected to respective diaphragms
19 and 24. Respective sprinys 20 and 25 act through the
associated diaphragms and rods to hold the valve elements 22 and
27 in an open position with respect to the ports 6 and 7~ Fluid
~L4~
pressure may be applied to the diaphragms 19 and 24 through
the passages 18 and 23 to oppose the action of the springs 20
and 25 respectively, so that the ports 6 and 7 are closed by
the valve elements 22 and 27.
The discharge port 9 is normally closed by the ball
valve 10 which is held in the closed position by the spring
13 acting through the rod 12. The diaphragm 30 is connected
to the rod 12 so that the ball ualve 10 may be moved to open
the port 9 by the application of fluid pressure to the diaphragm
30 through the port 28.
The movable member 3 is screw threaded into -the body 1
in a co-axial relation with the metering cavity 2. The
movable member 3 has a tubular extension portion 37 which
extends into the metering cavity 2 through an appropriate
seal 41, and carries at its lower end the gas inlet port 14.
The valve element 15 closes the gas port 14 under the action
of the spring 17 transmitted to the valve element 15 through
the rod 16 disposed co-axially in the extension 37. The
diaphragm 36 is attached to the rod 16 so that the application
of fluid pressure -to the chambers 35, as hereinafter described,
will raise the valve element 15 to open the port 14.
The chambers 35 communicate via the passages 34 with
the chamber 33 which in turn communicates with the passage
32 adapted at 31 at the face of the body 1 for connection to a
source of gas under high pressure. The gas port 14 communicates
with the chamber 35 via the annular passage formed between the
rod 16 and the exten~ion 37 of the movable member 3.
Rotation of the movable member 3 in threaded engagement
with the body 1 results in the lower end of the extension 37
moving axially in the metering chamber 2 to vary the capacity
thereof and, at -the same time, the position of the gas inlet
port 14 in the metering chamber is varied, whereby the quantity
of fuel delivered during each cycle is controlled~
The operation of the apparatus described above is as
follows:-
1. With the fuel inlet and fuel outlet ports 6 and 7
in the normally open condition, and the gas inlet port 14 and
-- 10 --
,.
73
discharge port 9 in the normally closed positlon, fuel ls
circulated through the metering cavity to maintain it filled
with fuel.
2. Pressure is appliecl to the diaphragrn 19 and 24
respectively to close the fuel inlet and fuel outlet ports 6
~nd 7 which results in a quantity of fuel being isolated
in the metering cavity 2, the quantity depending on the
position of the ex~ension 37 of the movable member 3 in the
metering cavity 2.
3. Pressure is also applied to the diaphragms 30 and
36 so that the valve elements 15 and 10 are moved to oFen the
ports 14 and 9 respectively. The opening of the port 14 admits
the gas under pressure to the metering chamber 2 so that the
liquid in the rnetering chamber is displaced thereform through
the now open discharge port 9 and hence through the delivery
passage 38. Thus the metered quantity of fuel in the metering
chamber 2 is delivered to the appropriate pa~t of the engine
to which the passage 38 is connected.
4. The gas pressure is then relieved from the four
diaphragms 19, 24, 36 and 30 so that the fuel inlet and outlet
ports 6 and 7 are opened, and the gas port 14 and the discharge
port 9 are closed by the actions of springs 20, 25, 17 and 13
respectively.
5. Fuel circulation thro1gh the metering chamber 2
is thus re-established,purging the gas therefrom and filling
the chamber with fuel, thereby placing the apparatus in a
condition for the next cycle.
The high pressure pulse of gas which issues from the
port 14 impinging on the stationary liquid in the metering cavity
2, and the somewhat tortuous path through which both liquid
and gas have to escape will result in a certain amount of break
up of the liquid into small droplets. In addition when the
mixtu-re of gas and liquid are allowed to escape into the space
into which injection is taking place, further atomization of
the liquid will occur. The amount of atomization, i.e. the
average droplet size of the spray produced, is determined by
a number of factors such as the ratio of gas to liquid in the
spray, the pressure drop which occurs on injection and the
.,
~4'~9
geometry of the nozzle through which injection takes place.
These can be varied over a wide range and are obvious to those
skilled in the art.
As previously referred to the quantity of fuel displaced
from the metering cavity 2 during each delivery operation is
varied by adjusting the portion of the movable member 3 within
the body 1. Accordingly, by rOtatiQn o the movable member 3
the assembly comprising the port 14, the valve element 15, the
rod 16, the chamber 35, diaphragm 36 and spring 17 are axially
displaced as an integral unit. This axial displacement moves
the extension portion 37 of the movable member carrying the gas
inlet port 14 towards or away from the delivery port 9 in the
body 1 so as to vary the quantîty of liquid which may be
received in the metering cavity 2 between these two ports and
hence vary the quantity of liquid which is metered for delivery
during each delivery cycle.
It will be appreciated that in the embodiment illustrated
only the seals 40 and 41 are subject to contact with moving
components during the operation of the apparatus, however the
movements involved are only those necessary to effect variation
in the metered quantity of fuel and are therefore relatively
small and infrequent.
The adjustment of the movable member 3 or the equivalent
component in other constructions of the metering apparatus may
be effected by electrical or mechanical means or by fluid
pressure. The sensing of the need for adjustment, and the extent
of the adjustment may be determined by suitable sensing devices
responsive to load conditions on the engine, pressure conditions
in the engine cylinder and/or manifold, or by direct operator~
control.
~he pressure pulses required to activate the various
valve elements and provide the gas under pressure to effect
the injection may be supplied from an independent purnp with
or without an intermediate reservoir. The pump ~y operate
at a pressure sufficiently high to meet the pressure requirements
of the injector or may be a low pressure pump operating in
conjunction with a pressure multiplier to give the required
- 12 -
'77~
operating pressure. Alternatively, gas under pressure may
be bled from the cylinder of the engine at a particular point
and/or over a selected period in the working cycle of ~he
engine to operate the valves and lnjector. Again, the
pressure may be applied directly or through a pressure
multiplier.
It will be wnderstood that the disposition and
manner of operating the valve elements in the injection
device illustrated in Figures 3 to 5 may be varied without
departing rom the inventive concept, and thus the present
invention is not limited to the particular disposition and
mechanism shown. By way of example, the valve controlling
admission of the gas under pressure to the metering cavity
may be in the body 1 (stationary member), and the valve
supplying the fuel to the injector in the movable member 3.
By way of another example 7 it is also possible to place all
ports and associated valves in fixed relationship to each
other in the body 1 (stationary member) and use the movable
member purely to vary the volume of liquid displaceable
from the metering cavity 2 by the admission of the gas
thereto.
An arrangement in which all ports and associated
valves are placed in fixed relationship to each other is
shown in Figure 6
The apparatus comprises the body 61 having the
metering cavity 62 formed generally centrally therein. The
movable member 63 is axially sledable in the body 61 and
extencls into the metering cavity 62. Four independent
ports cornmunicate with the metering cavity 62, namely fuel
inlet port 66, fuel outlet port 67, gas port 74 and discharge
port 69. The fuel inlet port 66 also communicates with fuel
passage 64, ths passage 64 being adapted at the face of the
body 61 to be connected to a fuel supply, such as a low
pressure pump delivering fuel from a storage tank. The
fuel outlet port 67 communicates with the fuel passage 689
which is again adapted at the face of the body 61 for
connection by a conduit to the fuel storage. Thus when the
ports 66 and 67 are open~ fuel may be circulated from
the storage tank through the metering cavity 62, entering
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~4~7~3
the cavity via the passage 64 and the port 66, and leaving
the cavity by the port 67, and passage 68,
~ he fuel inlet port 66 and fuel outlet port 67 are
controlled by respective valve elements 72 and 77 operated
by identical co~trol mechanisms. The valve elements 72
and 77 are connected to the ends of rods 71 ~nd 76
respectively, which at the opposite ends are connected to
respective diaphragms 79 and 84. Respective springs 70
and 75 act through the associated diaphrag~s 79,84 and
rods 71,76 to hold the valve elements 72 and 77 in an open
position with respect to the ports 66 and 67. Fluid
pressure may be applied to the diaphragms 79 and 84 through
the passages 78 and 83 to oppose the action of the springs
70 and 75 respectively, so that the ports 66 and 67 are
closed by the valve elements 72 and 77.
The discharge port 69 is normally closed by valve
element 90 which is held in the closed position by the
spring 93 acting through the rod 92. The diaphragm 94 is
connected to the rod 92 so that valve element 90 may be
moved to open the port 69 by the application of fluid
pressuxe to the diaphragm 94 through the port 88, annular
groove 95 and port 96.
Gas port 74 is normally closed by valve element
85 under the action of the spring 87 transmitted to the
valve element 85 through the rod 86. The diaphragm 89 is
attached to the rod 86 so that the application of fluid
pressure to the chamber 88, as hereinafter described, will
raise the valve element 85 to open the port 74.
The chamber 88 communicates via the passages 80
with annulus 81 which in turn co~nunicates with the passage
82. Passages 82 and ~8 both connect via passage 98, which
is out of the plane of the section shownj with passage 99
which is adapted at the face of the body 61 for connection
to a source of gas at high pressure. The gas port 74
communicates with passage 82 via the annular passage 81.
The operation of the apparatus described above
is as follows:- .
1. With the fuel inlet and fuel outlet ports 66 and
67 in the normally open condition, and the gas
-13a-
44779
inlet port 74 and discharge port 69 in the normally
closed position, fuel is circulated through the
metering cavity to rnaintain it filled ~ith uel.
2. Pressure is applied to the diaphragms 79 and 8
respectively to close the fuel inlet and fuel
outlet ports 66 and 77 which results in a quantity
of fuel being isolated in the meter-lng cavity 62,
the quantity depending on the position of the mova-
ble member 63 in the metering cavity 62.
3. Pressure is also applied to the diaphragms 94 and
89 so that the valve elements 85 and 90 are moved
to open the ports 74 and 69 respectively. The
opening of the port 74 admits the gas under pressure
to the metering chamber 62 via the annulus between
moving member 63 and fixed member 61 so that the
liquid in the metering chamber is displaced there-
from through the now open discharge port 69 and
hence through the delivery passage 100. Thus the
metered quantity of fuel in the metering chamber 62
is delivered to the appropriate part of the engine
to which the passage 100 is connected.
4. The gas pressure is then relieved from the four
diaphragms 79,84,89 and ~4 so that the fuel inlet
and outlet ports 66 and 67 are opened, and the
gas por~ 74 and the discharge port 69 are closed
by the actions of springs 70,75,87 and 93
respectively.
5. Fuel circulation through the metering chamber 62 is
thus re-established, purging the gas therefrom and
filling the chamber with fuel, thereby placing the
apparatus in a condition for the next cycle~
It is to be understood that, subject to the
manufacturing technique use, real means may be incorporated
between the body 61 and the movable member ~3. Also the
desportion of the respective ports may be varied, and other
constructions of valve mechanisms used.
The statement previously made in regard to the
embodiment illustrated in Figs 3 to S and relating to means
to effect movement of the~movable member 3 apply equally to
-13b-
7 7 ~
the effecting of movement of the movable melrlber 63 i.n the .
embodiment shown in Fig 6. Similarly the previous statements
regarding the source of the pressure pulses to operate
the valve rnechanisms are applicable to the embodiment show~
in Fig 6.
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.
