Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
_ELD OF INVENTION - ll~Z~8
The present invention relates to a safety closure or
shutoff device suitable for a circuit or distribution system
for fluid under pressure, comprisiny a pipe adapted to be
inserted into the circuit or distribution system, a piston
displaceable relatively to the pipe and so arranged as to
close off a flow section for fluid through the pipe when it
is in one of its end positions and to provide a flow duct
for the fluid in another of its positions.
BACKGROUND OF THE INVENTION
Safety closure devices are already known which can
be used for shutting off a pipe for gas under pressure, in
which the piston is actuated by the shock wave produced by
an explosion upstream of the device. Such a device is designed
so as to react to a sudden and very considerable increase in
the pres~ure and generally comprises special means which have
to ensure the closure at these high pressures, this involving
a size and a construction which do not permit the device to be
used for other applications.
OBJECT OF THE INVENTION
The present invention seeks to provide a device
adapted to be incorporated into a circuit or a supply or
distribution system for fluid of different types, for example,
in a hydraulic control circuit, such as a control circuit for
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hyclraulic brakes or jacks, or a distribution system for a
compressed gas or a vapour under pressure, or even for a
liquid, such as water or petroleum, without having any
effect on the normal functioning of such a circuit or
distribution system, but permitting an undesired flow of
the fluid to be prevented in the event of the distribution
system or piping breaking in the part situated downstream
of the device or in the event of another phenomenon leading
to an undesirable pressure drop downstream of the device.
SUMMARY OF THE INVENTION
According to the invention there is provided a safety
closure or shut-off device suitable for a distribution
s~stem for fluid under pressure, comprising a conduit
adapted to be inserted in the said system, a piston
displaceable in a piston chamber forming part of the
said conduit, at least one flow passageway of adjustable
section being provided through the piston, an outlet
orifice of the piston chamber being arranged to be closed
by the piston when the piston is in one of its end
positions in the piston chamber, the difference of fluid
pressure between the upstream and downstream sides of
the piston tending to push the piston towards said end
position, the displaceme~t of the piston being hindered by
the sliding resistance of the piston, means for adjusting
the section of the flow passageway independently from the
1~38Z9B
- 3a -
position of the piston in the conduit so as to make it
possible to adjust the value of the pressure difference
bet:ween the upstream and downstream sides of the piston
in such a manner that, up to a given maximum flow rate,
the force acting to push the piston towards the position
for shutting off the conduit is less than the force needed
to overcome the sliding resistance, so that the piston
remains immobilized in a position allowing the fluid to
pass through the conduit, whereas an increase of the
said pressure difference over a threshold value causes a
displacement of the piston to the position for completely
shutting off the conduit.
According to one preferred embodiment, the piston
comprises two parts, which are displaceable relatively to
lS one another for forming a flow duct of adjustable section.
More particularly, the said parts of the piston may be
traversed by an orifice forming at least a part of the
flow duct, the relative
1~38298
displacement of the two parts of the piston permitting the
section of this orifice to be regulated. The closure device
according to the invention may comprise piston-restraining
means, these being in the form of mechanical, hydraulic,
pneumatic, magnetic and/or electromagnetic means. The said
means may be arranged for automatically adapting the res-
training force to variationsin pressure upstream of the
piston and/or may be adjustable from outside the pipe of the
device.
The device according to the invention may comprise a
mechanical member, such as a rotatable rod, extending through
the wall of the pipe, the said member being coupled to one of
the adjustement of the section of the flow duct. According to
one embodiment, an actuating element extends through a lateral
openlng in the pipe and ls fast with an ad~usting member ar-
ranged for assuring the tight closure of the said opening in
the pipe.
According to a modified form of the invention, the
piston may be controlled by means of a rod passing through the
wall of the pipe, by a flexible membrane or diaphragm fixed to
the rod and mounted inside a chamber integral with the pipe.
Hydraulic or pneumatic means may be provided for acting
on the diaphragm so as to control the restraining force of the
piston and/or so as to actuate the latter under the effect of
an external control for shutting off the distribution system.
::: ::
i
BRIEF DES~RIPTION OF THE DR~WINGS
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1138298
Various embodiments of the invention will now be
described by way of example with reference to the drawings,
wherein :
Figures 1 and 2 show a first embodiment o~ the
device according to the invention, Figure 1 being a section
along a plane of symmetry passing through the axis of the
piston and Figure 2 being a section on the line II-II of
Figure 1 ;
Figures 3 and 5 re~resent a second embodiment of the
device according to the invention, Figure 3 being a section
on the line III-III of Figure 4 and Figures 4 and 5 being
respectively sections of the device along the lines IV-IV and
V-V of Figure 3 ;
Figures 6 to 9 are diagrammatic views in axial section
of other forms and modifications of the device according to the
invention ;
Figures 10 to 12 also represent another modified form,
Figure 10 being a longitudinal sectional view of the device,
Figure 11 a section on the line II'-II' of Figure 10 and
Figure 12 a section on the line III'-III'of Figure 10.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
.
Referring to the drawings the device which is shown
in Figures 1 and 2 comprises a housing 1 having an inlet
connection part 11 and an outlet connection part 12,
each having a screw thread for enabling the safety
device to be incorpora~ed into a distributlon system,
-- 5 --
~38Z9~3
for example, into the water supply pipe of a washing machine.
The hollow housing 1 comprises essentially three
chambers, namely, an inlet chamber 13, a piston chamber 14 and
an outlet chamber 15. The piston ch~mber 14 is formed by a tu-
bular sleeve 2 mounted in a corresponding hollow portion ofthe housing 1 and having openings for the inlet and outlet of
fluid, such openings being respectively indicated at 21 and
22. By means of these openings, the piston chamber 14 commu-
nicates respectively with the inlet and outlet chambers which,
at their other ends, open on to the corresponding connection
parts. A piston 3, arranged inside the sleeve 2 so as to be
axially displaceable, comprises two juxtaposed parts 31 and
32, through which extend openings 33 and 34, respectively.
Th~ shane of these openings in shown by way of example in
Figure 2. It is so chosen as to permlt the rate oE flow of
fluld through the device to be regulated by a relative rota-
tion between the two parts of the piston. For this purpose,
the part 32 is fast with a regulating rod 4 which extends
through a bore in the part 31 and also the part of the hous-
ing 1 facing the sleeve 2 through a plug 5 screwed into the
:~ housing 1. The part 31 has on its periphery a cam 35 which
is engaged in a longitudinal groove 23 of~the sleeve 2 and
.
- prevents the rotation of the part 31 relatively to the said
sleeye. In the axial direction, the part.s 31 and 32 are displa-
ced together, the rod 4 being designed to carry a fixing ele-
ment, such a.s a spring ring 41, facing the part 31.
At its free end, the rod 4 comprises an adjusting knob
2 8 42 which, firstly, permits a certain angular di.splacement to be
:1~38Z98
imposed on the part 32 of the piston relatvely to the part 31
and, secondly, the displacement of the piston assembly in an
axial direction. At the point where the rod 4 passes through
the~ plug 5, a lipped packing 6 is disposed in the plug and
extends around the rod 4. The tightness at the periphery of
the plug 5 is assured by an annular packing 7. On the downstream
side of the piston, the part 32 of the latter has a conical
portion which is adapted progressively to close the outlet
opening of the sleeve 2 when the piston is displaced in the
direction of flow of fluid. The outlet opening of chamber 14
is additionally formed by the central opening of an annular
packing 8, which ensures a tight closure of the fluid duct
in the final position of the piston at the time of its axial
displacement for closing purposes. When the present safety
dev~ce ls fitted lnto a fluid clrcult havlng a maximum rate
of flow determined downstream of the device, the rate of flow
through the duct 33,34 of the piston is regulated by means of
the knob 42 as a function of this maximal flow. This adjustment
is effected particularly in such a way that the piston remains
in equilibrium in the fluid flow, despite the pressure drop
through the duct 33,34 and the possible leakages of liquid at
the periphery of the piston, this latter not necessarily being
tight.
The surface of the piston exposed to the fluid pressu-
re upstream of the piston is reduced, relatively to the piston
surface on the downstream side of the latter, by the section
27 of the rod 4, which represents a not inconsiderable fraction
1~38Z98
of the total section of the piston. The adjustment of the sec-
tion of the duct 33,34 thus makes it possible, even without
other piston-restraining means, to achieve the equilibrium
of said piston for a given maximum rate of flow. If it should
happen that the pressure downstream of the piston falls sudden-
ly, for example, as a consequence of the pipe breaking, the
piston is displaced in the direction of the flow and comes to
a position closing the opening 22. The pipe is thus closed
automatically in such a case and may be opened again when the
permitted maximum rate of flow is re-established. The piston is
then placed by means of the knob 42 in an axial position per-
mitting the passage of the liquid, by the rate of flow through
the flow passage of the piston being regulated again as requi-
red.
A supplementary means for retalnlng the plston in
its posltion of equilibrium isformed by the lipped packing 6.
As the action of this packing on the rod 4 is reinforced when
the pressure of the fluid flow upstream of the piston increases,
the presence of this packing not only makes possible a shift in
the adjustment range of the triggering threshold of the sa-
fety device, but also an avoidance of an inopportune actua-
tion of the said safety device, following an increase in the
pressure upstream of the piston, i.e. in the entry chamber 13.
Other piston-restraining means may be used for replacing
the means mentioned above or for complementing these latter.
It is in particular possible to prov~de a second lipped packing
27 on the periphery of the piston, so as to increase the restrai-
1138298
ning force ~lth a sudden increase in the entry pressure. Accor-
ding to a modified embodiment, the rod 4 may be of very small
section and be provided with a mechanical means, for example
a spring, a magnetic means, an electromagnetic means or a
S hydraulic means for obtaining a restraining force on the pis-
ton, which force may either be constant or variable. More par-
ticulary, adjustment means may be provided for adapting the
safety device to different cases of application or different
operating conditions.
Figures 3 to 5 show one constructional form of the
safety device, in which the piston and the means for adjusting
the section of the flow duct are coaxially arranged. This device
comprises a conduit formed by two coaxial parts, 51,52 which
are formed t their froe ends with means, for example a screw
thread, for permitting the device to be fitted lnto a fluid
distrlbution system or pipeline. On lts other end, the part
51 is terminated by tw~ slde members 51' and 51" ,which extend
the wall of the condui 51 in two diametrically opposite regions
and form beuween them 1wo lateral openings of the pipe or
conduit of the device At their free ends, the parts 51', 51"
are of a reduced thickness, so that the external diameter which
they define correspondj to that of a tubular sleeve 53~formed
with two diametrically opposite notches, into which are fit-
ted the ends of the parts 51',51". The external surface of
the sleeve j3 and of the ends Sl',Sl" are formed with a screw
thread corresponding to an lnternal screw thread of the conduit
27 part 52, th IS making p~ssible the screwing of the part ~-2
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1138Z98
on to the end of the assembly 51,53.
The pistorl of the device according to Figure 3 to
5 is rormed by two parts 60,62 of which the first has a coni-
cal portion co-operating with an annular packing 54 fitted
Ln the member 51. The central portion of the member 60 has
extending therethrough two openings 61,61', which represent
the flow duct through the piston. As the part 62 of the piston
essentially has the form of a disc in which are drilled two
openings permitting the passage of the slide members 51'and
51", it has in its central portior openings 63,63' of the same
shape as the openings 61,61'. The part 62, guided by the side
members 51',51", may only be displaced axially, whereas the
part 60, connected to ~2 by means of a screw 64, can be
shifted angularly in relation to 62. Thus, as shown in
Flgure 5, the openings 61,63 and 61',63' can be offset from
one another in order tc define th~ section of the flow duct
through the device. In order to permit this adjustment, the
part 60 has two latera] arms extending through the lateral
openings formed in the pipe or corduit 51 between the side
members 51' and 51", the ends of these arms being fitted
into a casing formed of two parts 55,56, the internal dia-
meter of which corresponds to the external diameter of the
part 62. The two parts 55 and 56 can be screwed into one
another, an annular packing 57 en uring the tightness of
the assembly at this pcsition. Each part of the casing has an
axial bore of a diameter sli~3htly larger than -~he external
27 diameter o the conduit partS 51 and 52 and lipped packir.gs
-- 1~ --
1138~98
58 and 59 are disposed inside the end portions of the casing
so as to ensure the tightness of the latter relatively to the
pipe or conduit 51,52,
Figure 3 represents one end position of the piston, in
which the fluid arriving by way of the part 52 of the conduit
passes through the flow ducts 61,63 and 61',63', to leave
through the part 51. Quite obviously, the fluid generally
fills the entire internal space of the device. As the part 60
is fast with the casing 55,56, a rotation of the latter
enables the passage section for the fluid to be regulated
by an angular displacement of the part 60 relatively to
52. The assembly comprising the piston and the casing is
displaceable axially against the restraining force produced
by thP frictlon of the packings 58 and 59 on the periphery
of the condults 51,52, As a result of llpped packings being
used, this restraining force increases with an increase in
the fluid pressure inside the casing~
When it happens, that for example, because of a
break in the conduit downstream of the device, the fluid
pressure falls on this side of the device, the diffrence
between the pressures being exerted on the upstream and
downstream sides of the piston will exceed the threshold
value which is essentially defined by the restraining force
of the casing on the pipe or cond~it 51,52. The piston will
then be displaced axially and, at the end of its travel, will
close the opening in the packing ,4 by means of the conical
27 portion of the member 60.
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1138Z98
Once the cause for the actuation of the device has
been overcome, the piston may be once again placed in its
initial position, such as that shown in Figure 3, and the
device reassumes its monitoring function on the pipeline
or distribution system.
Figure 6 illustrates ina somewhat diagrammatic form
one embodiment of the closure device, in which the piston is
subjected to a magnetic restraining force which is adjustable
from outside the pipe or conduit. The pipe 71 has an inlet
opening 72 and an outlet opening 73 formed by a packing 74,
this latter being retained by means of a closure element 75
formed with an internal connecting thread. The opposite end
of the pipe 71 is closed by a member 76 having at its centre
an opening for the passage ofa piston rod 80. The said opening
is surrounded by a lipped packing 77 for ensuring tightness
and for providing a certain retaining force which is variable
with the inlet pressure of the fluid. The piston of this
device is made in two parts 78 and 79, of which the latter has
a conical closure part similar to the preceding examples. The
two parts of the piston are mounted so that they are rotatable
relatively to one another, the part 78 being guided axially
by a lug 78' which engages in a longitudinal groove. In this
way, only the part 79 can be displaced angularly for regula-
ting the section of the fluid flow duct through the piston.
25 This adjustment is effected by means of the piston rod 80,
which carries at one end an adjusting knob 81 and which, at
27 its other end, turns freely in the two parts of the piston.
. - 12 -
~38Z9B
In its axial movement, the rod 80 is made fast with the pis-
ton by means which are indicated diagrammatically. A pinion
82, fast with the rod 80, is clisposed inside a hollow of the
member 79 and co-operates with a pinion 83 mounted on the
member 78. In its turn, the pinion 83 controls an internal
toothing 84 on the member 79. The assembly thus constitutes
a reduction mechanism facilitating the adjustment of the
section of the flow duct by means of the adjusting knob 81.
The part 78 of the piston comprises an annular ma-
gnet 85 which is magnetised in the axial direction. Arranged
externally of the tubular conduit 71 which, in this case, is
made of a non-magnetic material, are two annular magnets 86
and 88 which are likewise magnetised axially, in the same direc-
tion as the ring 85. These external annular or rlny magnets
are encased in support members 87 and 89, respectively, which
are displaceable axially on the conduit 71 by means of an
endless screw 90 fitted in two supports 92 and 93 integral
with the conduit 71. The screw 90 has a right-hand thread
on a part co-operating with the support 87 and a left-hand
thread on a second part co-operating with the support 89, so
that a rotation of the adjusting knob 91 permits the magnets
86 and 88 to be displaced in opposite directions relatively
to the conduit 71. This permits themagnetic force of attrac-
tion exerted by the magnets 86 and 88 on the magnet 85 to be
regulated and, consequently, the retaining force by which the
piston tends to be held in its intermdiate rest position
27 against the difference in pressures being exerted on the two
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i~38Z98
upstream and downstream faces, respectively.
Figure 7 illustrates a modification, according to
which the piston has a part 94 of magnetically permeable
material co-operating with an electromagnet disposed outside
the conduit 71, which here also in non-magnetic. This electro-
magnet comprises an armature 95 and a coil 96 supplied by a
circuit (non shown). This arrangement permits the retaining
force of the piston to be regulated by an ~justment of the
current passing in the coil 96 and is thus particularly well
suited for a remote control of this retaining force.
Figure 8 represents another modification in a device
similar to that of Figure 6, in which the similar elements
have been given the same reference numerals. In the case of
Figure 8, the piston 97 is also formed of two parts displa-
ceable angularly relatlvely to one another and one of these
parts is fast with a rod 98 passing through the wall 76 of
the conduit and having an adjusting or control knob 81 its free
end. The peripheral part of the piston is formed with an in-
flatable packing 99 which communicates with a passage 100
passing through the piston rod 98. This passage is connected
to the outside of the conduit 71 by way of a connecting
member 101 to a fluid source (not shown) of adjustable pressure.
By hydraulic or pneumatic means, the adjustment of this pres-
sure permits of adjusting the frictional force effective
between the inflatable packing 99 and the inside wall of the
conduit 71.
27 According to a modification, the passage 100 may
- 14 -
~i38Z98
communicate with the piston chamber through a lateral opening
102 in the rod 98, so as to cause the fluid pressure upstream
of the piston to act on the packing 99 and as a result to
ca~lse the retaining force to be dependent on the fluid pressure
at the inlet o~ the safety device.
Figure 9 represents another constructional form of the
device as regards the control section thereof. The piston, which
is not shown in this Figure, is once again d.isplaceable in
a cylindrical tube 103 and is fast with a control rod 108
provided with an adjusting knob 81. That part of the device
which is not shown may be constructed as in the preceding
Figures, the control knob 81 permitting the regulation of the
section of the fluid flow duct to be supervised. The conduit
103 is extended by a tube 104 which is screwed on the end of
the said conduit 103, thls latter having a closure member 105
provlded with a lipped packing 109 for ensuring the tightness
of the passage of the rod 108 through the member 105. A flexible
diaphragm 110 is fixed inside the tube 104 by means of a tube
; 111 held in the tube 104 by a cover 106 screwed on to the end
of the tube 104. The diaphragm 110 is fixed to the rod 108
whlch extends through it, by means of a member 112 which is
represented diagrammatically. A packing 107 ensures the
tightness of the passage for the rod 108 through the cover 106,
this latter having a fluid inlet opening 113.
A fluid inlet opening 114 may also be provided in the
part of the wall 104 disposed between the diaphragm 110 and
: 27 the closure plate 105 of the piston chamber. Thus, the piston
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:` ;~: ` `
~38Z98
can be controlled by the difference between the pressures obtain-
ing on either side of the diaphragm 110, thereby particularly
permitting the piston to be actuated in one direction or the
other and/or for its restraining force to be defined. In this
constructional form, the device may thus serve as a valve
remotely controlled by hydraulic or pneumatic means. The fluid
inlet 113 may for example be connected to a device supervising
the degree of filling of a tank supplied by means of the device
in Figure 9, so that the latter is actuated automatically, when
a predetermined level is reached in the tank, by the pressure
of the fluid admitted through the opening 113 and being exerted
on the diaphragm 110, causing the displacement of the piston
towards the closure or shut-off position.
The device which i8 shown in Figures 10 to 12 comprises
lS a cylindrical housing 1', forming a tubular chamber. The housing
1' is formed with a lateral threaded tubular neck 2a', per-
mitting it to be connected, by means of a fluid-tight union of
conventional type, to an inlet pipe for fluid under pressure,
and an axial threaded tubular neck 2b', permitting it to be
connected to an outlet pipe for fluid under pressure. This
arrangement permits the device to be incorporated into a cir-
cuit or distribution system for a flow of fluid under
pressure.
A piston of cylindrical section, composed of two
separate parts, namely, a front part 3a' and a rear part 3b',
is placed inside the housing 1'. The maximum external diameters
27 of the parts 3a' and 3b' are at least approximately equal to
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1138;i~8
one another and are slightly smaller than the internal
diameter of the housing 1', in order to allow the piston 3a'-
3b' to slide freely, by sliding along the internal wall of
the cylindrical chamber defined inside the chamber 1'. A sealing
O-ring 4' encloses the part 3a' and i-t is placed in a cylindrical
groove, of which the lateral sides are formed by the faces
30a' and 30b' of the parts 3a' and 3b' of the piston facing one
another and perpendicular to the longitudinal a~is of the hous- -
ing 1', and of which the bottom is formed by a part 20' of the
peripheral face of the part 3a' of the piston, having a diame-
ter smaller than the maximum external diameter of this piston
part. The value of this diameter is such that, when the O-ring
4' is not subjected to any lateral force of compression by
the faces 30a' and 30b', it i5 subject to a compressive force
between the part 20' of the wall of the part 3a' of the piston
and the inside wall of the cylindrical chamber of the housing
1', whlch is sufficient to establish a frictional force oppos-
ing the displacement of the piston 3a'-3b' inside the said
chamber. In the absen.ce of any compressive force on the side
walls of the O-ring packing 4' by the faces 30a' and 30b',
this frictional force has a minimal value corresponding
to a minimum of pressure difference ~etween the downstream
face and the upstream face of the piston while the apparatus
is functioning~ This fr3ctional force can be regulated to
higher values, as will hereinafter be described, by bringing
the faces 30a' and 30b' closer to one another, so as to exert
27 a compression on the side walls of the packing 4'.
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~138Z98
Two fluid flow orifices 5a', having the general shape
of an arc of a circle are formed through the part 3a' of the
piston (~igures 10 and 12) and two flow orifices 5b', having a
shclpe and dimensions corresponding to the orifices Sa', are
formed through the wall 3b' of the piston and are each faced
opposite a corresponding orifice 5a'.
That end of the cyiindrical chamber of the housing l'
which is situated alongside the outlet neck 2b' for the fluid
is provided with an member 6' flared out conically towards the
interior of this chamber and terminating in a cylindrical
bore of the same internal diameter as that of the fluid outlet
passage in the neck 2b'. The member 6' is preferably formed
by a single member of a plastic material which is slightly
elastically deformable.
15The ~ront end of the part 3a' of the plston forms a
cone positioned on the axis of the flared part and the cylin-
drical bore of the member 6', so that when the piston 3a',3b'
slides in the housing l', this cone is progressively driven
into this flared portion and this bore, so as to cause the
progressive closure of the orifice of the fluid outlet duct,
: this closing action being complete when the external wall of
this cone comes to bear against the internal wall of the flar-
ing in the member 6'. The member 6' is preferably made of a
slightly deformable plastic material, this permitting an
excellent tightness of the closure to be obtained. It is
also preferable for the part 3a' of the piston, or at least
27 its conical end, to be made of a slightly deformable plastic
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1138Z98
material, for example of hard rubber, similar to or identical
with the material which forms the member 6'.
It is to be noted that the conical form of the front
end of the piston, as well as the partially flared form of
the member 6', permit the effect known as "hammering" to be
avoided at the time of closure.Thepart 3b' of this piston is
provided with a cylindrical part 7' which forms the upstream
face of the piston and on which is applied the force result-
ing from the pressure difference between the upstream and
downstream sides of the piston in the cylindrical chamber
when a fluid under pressure is flowing in the circuit through
the cylindrical chamber and passing through the piston 3a',
3b' by way of its flow orifices 5a' and 5b'.
A rotatable disc 8' is interposed between the part
3b' of the piston and the part 7', whlle being retained by
this latter, 50 as to be ~pableofturning in the seating which
is formed between the lateral rim of the part 3b' of the piston
and the inside wall of the part 7' which are opposite one
another (Figures 10).
The part or member 7' has extending therethrough an
arcuate flow orifice 9', to which corresponds an arcuate flow
orifice 10' formed through the rotatable disc 8'. As will be
seen from Figure 11, it is possible by rotation of the disc 8'
to bring the orifice ld' into complete or partial coincidence
~; 25 with the orifice 9' or, on the contrary, to eliminate any
coincidence between these two orifices, this arrangement per-
:
~ 27 mittlng the section of the fluid flow duct through the piston
`:
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~38Z98
to ~e regulated.
The relative displacement in rotation of the parts
3a' and 3b' of the piston is prevented by the presence of
two guidiny rods 11', which are screwed into the part 3a'
o~ the piston and which each slide in an orifice formed inside
the part 3b', so that only a movement of relative approach
of the parts 3a' and 3b', one relatively to the other, is
possible axially of the piston.
A headed screw 12' extending through a bore formed
axially of the part 3b' of the piston and engaging in a
threaded bore 13' formed axially of the part 3a' o~ the piston
permits the approach of these two piston parts to be carried
out, by tightening the screw 12' and consequently tightening
the joint 4' between the respective faces 30a' and 30b' of
these parts 3a' and 3b' of the piston. q'he tightening and
slackening off of the screw 12' are obtained by causing the
sliding actuating rod 16' to turn in the appropriate direction,
the said rod carrying an operating knurled wheel 18' at its
end situated outside the housing 1', the end of said rod
arranged inside the housing 1' carrying a hexagonal head 17'
which co-operates with a hexagonal recess 14' formed in the
head of the screw 12'. When the screw 12' is unscrewed, the
parts 3a' and 3b' of the piston are spaced from one another
` because of the elasticity of the O-ring packin~ 4', which tends
to be restored to its original form.
The central part of the disc 8' is also formed with
~ 27 a hexagonal recess 15' having the same shape and dimensions as
- 20 -
98
that of the recess 14'. sy a simple axial sliding movement,
the rod 16' may be positioned so as to be forced to a greater
or lesser extent into the piston, either into a first posi-
tion of maximum insertion, permitting the co-operation of its
head 17' with the hexagonal recess 14', or into a second po-
sition of minimum insertion , permitting the co-operation of
the head 17' with the hexagonal recess 15'. In the first posi-
tion, the rotation of the rod 16' by acting on the knurled
wheel 18' permits the screw 12' to be tightened or slackened
off and thus, as indicated above, for the two parts 3a' and
3b' to be brought closer together, tightening the O-ring
packing 4' between their faces 30a' and 30b', so as to
increase the frictional force of the piston inside the housing
1', or to relax the tightness of the packing 4' so as to reduce
this frictional force. The adjustment of the resistance of the
piston to displacement is thus obtained.
In the second position, the rotation of the rod 16'
makes it possible for the disc 8' to be turned, this having the
effect, as indicated above, of causing a variation in the sec-
tion of the fluid flow duct in the piston and thus permitting
the adjustment of this section.
The upstream end of the housing 1' carries a threadedpart on which is screwed a threaded closure cap 19', of which
the central part has drilled therein a bore formed with a
sealing joint permitting the passage of the rod 16' and
~` allowing movements for axial displacement in rotation of this
rod, while maintaining the tightness of the cylindrical chamber
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. ~13~
formed inside the housing l'. The cap 19' is preferably made
of a hard plastic material. It is clear from the foregoing
description that the device operates by displacement of the
piston towards the downstream end until the orifice of the
fluid outlet duct is closed, when the pressure difference
between the upstream and downstream sides of the piston exceeds
a predetermined value corresponding to the force necessary
for overcoming the frictional force of the piston inside
the cylindrical chamber of the housing 1'. This pressure dif-
ference is itself equal to the difference between the fluid
pressure upstream of the piston and the pressure drop in that
part of the circuit positioned downstream of the piston.
Under normal working conditions of the fluid distribu-
tion circuit, this last pressure drop is high and it may have
a value almost as large as the fluid pressure upstream of
the piston. It is to be noted that the opening of the fluid
flow duct through the piston is preferably regulated in
such a way that the pressure drop caused by the passage of
the fluid through the piston is clearly lower than the pressure
drop in the part of the circuit downstream of the piston.
Thus, in the absence of any anomaly in the part of
the circuit placed downstream of the device, the piston
remains immobile in the cylindrical chamber and the orifice
of the fluid outlet duct in normally open.
On the other hand, in the event of an abnormal decrease
; in the pressure drop in this part of the circuit downstream of
27 the device, resulting for example from the breaking of the
`~
- 22 -
: `:
~3~
pipeline or the failure of the closure valve or cock placed
at the end of this pipeline, the difference in pressures
between the upstream and downstream sides of the piston becomes
hlgher thant the frictional force of this latter, this
immediately causing the closing of the orifice oE the fluid
outlet duct of the housing 1'. In this way, any undesired
flow of fluid downstream of the device is avoided. The
frictional force of the piston is quite obviously regulated
so as to permit the variation of the pressure drop in the
part of the circuit downstream of the device, within the
limits corresponding to normal operation (for example,
between the position of complete closure of the terminal
valve and its position ofmaximum opening) without causing the
displacernent of the piston.
Other applications and formsof the present device may
be easily visualised by a person skilled in the art from the
17 examples as given above.
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