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EP 0 267 803 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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30.12.1992 Bulletin 1992/53 |
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Date of filing: 13.11.1987 |
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International Patent Classification (IPC)5: B65D 90/22 |
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Fluid transport tankers
Tanker zum Transport von Flüssigkeit
Citernes pour le transport de liquide
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Designated Contracting States: |
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BE DE ES FR GB NL SE |
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Priority: |
14.11.1986 GB 8627326
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Date of publication of application: |
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18.05.1988 Bulletin 1988/20 |
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Proprietor: EMCO WHEATON U.K. LIMITED |
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Margate, Kent CT9 4JR (GB) |
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Inventor: |
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- James, Simon
Monkton
Kent CT12 4JW (GB)
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Representative: Davies, Christopher Robert et al |
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Frank B. Dehn & Co.,
European Patent Attorneys,
179 Queen Victoria Street London EC4V 4EL London EC4V 4EL (GB) |
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References cited: :
EP-A- 0 129 488 US-A- 4 091 848
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US-A- 4 024 897 US-A- 4 109 677
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] This invention relates to fluid transport tankers, such as road or rail tankers,
and to pneumatic control means therefor.
[0002] It is known to provide pneumatic control means in conjunction with e.g. road tankers
for controlling the operation of various components associated with the tanker such
as the inlet/outlet and vent valves, such means being intended both to increase safety
as regards filling and delivery procedures in the case of toxic or inflammable fluids
and also to reduce the possibilities for embezzlement.
[0003] Such an arrangement is known from EP-A-0 129 488, wherein a pneumatic safety circuit
includes a pressure switch connected via a pipe to a manually operated control valve.
Under normal operation the control valve must be vented to atmosphere before a filler
arm attached to the tanker can be disconnected. In the event that the tanker driver
attempts to drive away without first disconnecting the filler arm, the pressure retained
in the pipe acts on the pressure switch which in turn actuates a warning signal.
[0004] In a further known arrangement such as US-A-4 024 897, the tanker is provided, as
a security feature, with a barrier member typically in the form of an elongate bar
or shield which is arranged e.g. for pivotal movement between a first position wherein
it extends in front of the outlet valve or valves and a second position permitting
access to the outlet valve(s) so that a delivery conduit can be connected thereto.
[0005] In another known arrangement, pneumatically operable locking means for the barrier
member are adapted to retain the member in its first position, such locking means
being connected to a pneumatic control unit of the tanker and only being releasable
in response to a pneumatic signal therefrom. Such arrangements help to avoid embezzlement
by unauthorised personnel who do not have access to the control unit.
[0006] In one known arrangement the locking means for the barrier member also forms part
of a safety means for the tanker in that movement of a locking element of the locking
means to release the barrier member is also effective to open a pneumatic switch which
applies a pneumatic signal to actuate means preventing movement of the tanker. Such
means may be effective to apply the tanker brakes or alternatively to inhibit the
engine starting electrical circuit, and in either case the effect is to prevent movement
of the tanker at all times when the barrier is unlocked. This avoids the possibility
of the driver inadvertently moving the tanker when one or more of the outlet valves
are connected to a delivery conduit, and also ensures that the tanker cannot be driven
off after delivery has taken place with the operator having neglected to return the
barrier to its first position and lock it therein.
[0007] It has also been proposed, as an additional safety feature particularly applicable
to tankers wherein filling is carried out by pumping in fluid under pressure via the
same valves which are used to discharge the fluid, that a pneumatic signal from the
switch associated with the locking means is additionally applied to a means which
enables filling of the tanker to take place. Such means may be in the form of a pressure
sensitive pneumatic switch coupled to an electrical switch arranged to isolate the
pumping means for the tanker from its power source, so that the pumping means can
only possibly be energised when the switch is turned on and thus only when the locking
means for the barrier member is released.
[0008] However, in known systems of this type it is desirable to provide at least one manually
operable master shut down switch whereby the control means can be readily deactivated
in an emergency, and problems in this respect can arise in the prior art arrangement
discussed above in that disabling of the said means enabling filling of the tanker
to take place also results in the means preventing movement of the tanker being disabled
which is undesirable even in an emergency shut down condition of the control means.
[0009] Viewed from one aspect the invention provides a fluid transport tanker comprising
a barrier member arranged for movement between a first position wherein it is so located
as to prevent connection of a delivery conduit to one or more outlet valves of the
tanker and a second position wherein access may be gained to said valve(s) for connection
of a delivery conduit thereto; characterised in there being pneumatically operable
locking means for the barrier member comprising a locking element arranged to retain
the member in its first position, such element being retractable in response to a
pneumatic signal applied to the locking means to release the barrier member, there
being pneumatic control means including first and second pneumatic switches respectively
operable in response to retracting movement of said locking element to actuate means
enabling filling of the tanker via said outlet valve(s) to take place and to actuate
means preventing movement of the tanker, said first switch being connected to a pneumatic
pressure source via at least one manually operable master shut down switch of the
control means and said second switch being connected to the same or further pneumatic
source independently of said shut-down switch.
[0010] Viewed from a second aspect the invention provides a pneumatic control means for
a tanker as aforesaid.
[0011] Thus, in accordance with the invention whilst the safety features discussed above
associated with the barrier member locking means are retained, problems concerning
the possibility of disabling the tanker filling means and at the same time preventing
movement of the tanker in an emergency condition are avoided.
[0012] The means preventing movement of the tanker may take any convenient form, and typically
may be adapted to apply the tanker brakes and/or disable the engine ignition and/or
an electrical engine starting circuit in response to a pneumatic signal applied from
said second switch. The means enabling filling to take place may also take any suitable
form, and may typically comprise pneumatically responsive electrical switch means
arranged in an electrical supply circuit for fluid inlet pumping means for the tanker
whereby the pumping means can only be actuated when said switch means is turned "on"
consequent upon a pneumatic signal being applied thereto from the first switch associated
with the barrier member locking means. In a preferred such embodiment, the electical
switch means is also responsive to a pneumatic switch means responsive to a vapour
outlet conduit connection of the or each fluid container of the tanker and to a fluid
sensor provided at the top of the container, so that the pumping means is also automatically
disabled when there is no vapour outlet conduit connected to the container to collect
vapour forced therefrom during filling, and when the container is full.
[0013] In a particularly preferred embodiment the barrier member locking means and the first
and second pneumatic switches responsive to movement of the locking element thereof
form part of a common unit and viewed from a third aspect the invention provides such
a unit for a tanker and for pneumatic control means therefor as aforesaid.
[0014] Advantageously, the unit comprises a housing defining an elongage bore, and a plunger
slidably mounted in the bore, a free end of said plunger being arranged to project
from the housing and forming or being connected to said locking element, said first
and second pneumatic switches each comprising respective axially spaced inlet and
outlet ports communicating with said bore and sealing means associated with the plunger
arranged to isolate said respective ports from one another in the locked condition
of said element and to communicate said respective ports with one another when the
locking element is retracted. It is also required that the housing includes an inlet
port communicating with said bore arranged for the application of a pneumatic signal
for retracting the plunger so as to release the locking element, and in a particularly
advantageous arrangement such inlet port is common with the inlet port of the first
pneumatic switch of the unit, so that the pneumatic signal applied to the means enabling
filling of the tanker to take place is firstly used to retract the locking element.
This has the advantage that a common pneumatic supply line connected to the pressure
gas source via one or more master shut down switches may be used for retracting the
plunger and for enabling filling so that the number of connections to the unit can
be reduced. In a preferred embodiment the plunger is moved against the force of a
biasing spring, in which case in the embodiment discussed above wherein the plunger
actuating signal is applied via the master shut down switch(es), the locking element
is preferably arranged to be held in its retracted condition by camming engagement
with the barrier member when in its second position which ensures that the second
switch is held open and the tanker is thus prevented from moving even in the event
that a shut down switch of the control means is closed.
[0015] A preferred embodiment of the invention will now be described, by way of example
only, with reference to the accompanying drawings, wherein:
Figure 1 is a schematic diagram illustrating the locking means for the outlet valve
barrier member of e.g. a road tanker together with the associated parts of the pneumatic
control means; and
Figure 2 illustrates in partial cross-section a preferred form of locking means and
pneumatic switches associated therewith.
[0016] Referring to the drawings, as shown schematically in Figure 1 a road tanker is provided
with first and second locking means 1 provided adjacent each end of a barrier member
(not shown) arranged, in a first position thereof, to extend in front of outlet valves
of the tanker. The locking means 1 each include a locking element 2 retractable upon
application of a pneumatic signal applied from a pneumatic control unit (not shown)
via a first inlet line 3, the two locking means 1 being arranged in series in this
respect. Thus, in their extended condition the locking elements 2 engage in complementary
recesses associated with the barrier member to retain the member in its first condition
wherein access may not be gained to the outlet valves of the tanker for connection
of delivery conduits thereto. Upon retraction of the locking elements 2 consequent
upon a pneumatic switch being operated in the control unit so as to apply a pneumatic
signal via line 3, the barrier member is released and can be moved e.g. by pivoting
away from the outlet valves.
[0017] As shown in Figure 1, the downstream one of the locking means is connected via a
further pneumatic line 4 to a pressure sensor 5 which is in turn coupled to an electrical
switch arranged in the electrical power supply for a pumping means (not shown) used
to pump fluid into the tanker. The line 4 is connected to the pressure sensor 5 via
a pneumatic switch means 6 which is responsive firstly to a vapour outlet hose interlock
and secondly to a level sensor provided inside the tanker adjacent the top wall thereof.
Thus, the line 4 is only connected to the pressure sensor 5 when a hose is connected
to the respective container of the tanker for release of vapour forced out during
filling, and, furthermore, the pumping means is disabled when the container is full.
[0018] As will be discused in more detail below in conjunction with Figure 2, the barrier
member locking means each comprise first and second pneumatic switches 7, 8 which
are opened when the locking element 2 is retracted. The first switches 7 are arranged
in series to communicate the pneumatic line 3 with the line 4 and thus to apply a
pneumatic signal via the switching means 6 to the pressure sensor 5. In this way,
it will be appreciated that it is only possible to energise the pumping means when
the locking elements are retracted. The pneumatic line 3 is connected to a pneumatic
pressure gas source via one or more manually operable master shutdown switches (not
shown) of the control means, so that in the event of such switches being closed in
an emergency condition a pneumatic signal is no longer applied to the pressure sensor
5 and the pump means is thus disabled.
[0019] As also shown in Figure 1, the second switch 8 of the downstream one of the locking
means connects a futher pneumatic supply line 9 with a line 10 leading to means preventing
movement of the tanker. Such means could be adapted to apply the tanker brakes and/or
to disable the electrical starting circuit of the tanker. The line 9 is connected
to the pneumatic gas source in a circuit which is separate from the master shutdown
switches whereby in an emergency condition closing of the shutdown switches does not
affect the movement preventing means.
[0020] A preferred form of locking means 1 is illustrated in Figure 2 and comprises a housing
30 formed e.g. of aluminium having formed therein an elongate bore 11 in which a plunger
12, the front end of which forms the locking element 2, is slidably mounted. The first
and second switches 7, 8 include respective inlet and outlet ports 13, 14; 15, 16
which are axially spaced and which communicate with the bore 11. Sealing means in
the form of O-rings 20 are carried by the plunger so that in the extended condition
of the locking element shown in elevation in the lower part thereof in Figure 2, the
respective inlet and outlet ports 13, 14; 15, 16 are isolated from one another. Upon
application of a pneumatic signal via line 3 to inlet port 13, the plunger 12 is urged
rightwardly as shown in Figure 2 against the force of a biasing spring 21 so that,
as shown in section in the upper part of the Figure, the respective ports 13, 14;
15, 16 are communicated with one another. A port 22 open to atmosphere is provided
to permit release of air from the region behind the plunger as it is moved between
its extended and retracted positions. As shown in Figure 2, the preferred locking
means and associated switch means constitutes a simple and robust unit, the bore being
closed at the end remote from the locking element 2 by means of a plug 25 arranged
to seat the spring 21 and retained in place via a circlip 26. Apertures 27 are provided
whereby the unit may be secured by means of mounting bolts in a desired location adjacent
the barrier member.
[0021] Whilst certain broad aspects and specific features of apparatus have been described
and illustrated herein, modifications may be apparent to those of relevant skill which
retain one or more of the advantages thereof.
1. A fluid transport tanker comprising a barrier member arranged for movement between
a first position wherein it is so located as to prevent connection of a delivery conduit
to one or more outlet valves of the tanker, and a second position wherein access may
be gained to said valve(s) for connection of a delivery conduit thereto;
characterised in there being pneumatically operable locking means (1) for the barrier
member comprising a locking element (2) arranged to retain the member in its first
position, such element (2) being retractable in response to a pneumatic signal applied
to the locking means (1) to release the barrier member, there being pneumatic control
means including first and second pneumatic switches (7,8) respectively operable in
response to retracting movement of said locking element (2) to actuate means enabling
filling of the tanker via said outlet valve(s) to take place and to actuate means
preventing movement of the tanker, said first switch (7) being connected to a pneumatic
pressure source via at least one manually operable master shut down switch of the
control means and said second switch being connected to the same or further pneumatic
source independently of said shut-down switch.
2. A fluid transport tanker as claimed in claim 1 wherein said means preventing movement
of the tanker is adapted to apply the tanker brakes.
3. A fluid transport tanker as claimed in claim 1 wherein said means preventing movement
of the tanker is adapted to disable the engine ignition.
4. A fluid transport tanker as claimed in claim 1 wherein said means preventing movement
of the tanker is adapted to disable an electrical engine starting circuit.
5. A fluid transport tanker as claimed in any preceding claim wherein means enabling
filling to take place comprise pneumatically responsive electrical switch means (5)
arranged in an electrical supply circuit for fluid inlet pumping means for the tanker
whereby the pumping means can only be actuated when said switch means (5) is turned
"on" consequent upon a pneumatic signal being applied thereto from the first switch
(7) associated with barrier member locking means (1).
6. A fluid transport tanker as claimed in claim 5 wherein said electrical switch means
(5) is also controlled by a pneumatic switch means (6) responsive to a vapour outlet
conduit connection of the or each fluid container of the tanker and to a fluid sensor
provided at the top of the container.
7. A fluid transport tanker as claimed in any preceding claim wherein the barrier member
locking means (1) and the first and second pneumatic switches (7,8) of the control
means responsive to movement of the locking element (2) thereof form part of a common
unit.
8. A fluid transport tanker as claimed in claim 7 wherein the unit comprises a housing
(30) defining an elongate bore (11), and a plunger (12) slidably mounted in the bore,
a free end of said plunger being arranged to project from the housing and forming
or being connected to said locking element (2), said first and second pneumatic switches
(7,8) each comprising respectively axially spaced inlet and outlet ports (13,14; 15,16)
communicating with said bore and sealing means (20) associated with the plunger arranged
to isolate said respective ports from one another in the locked condition of said
element and to communicate said respective ports with one another when the locking
element (2) is retracted, said housing further comprising an inlet port (13) communicating
with said bore arranged for the application of a pneumatic signal for retracting the
plunger so as to release the locking element.
9. A fluid transport tanker as claimed in claim 8 wherein said inlet port (13) is common
with the inlet port (13) of the first pneumatic switch (7) of the unit.
10. A fluid transport tanker as claimed in claim 8 or 9 wherein said plunger (12) is moved
against the force of a biasing spring (21).
11. A fluid transport tanker as claimed in any of claims 7 to 10 wherein said locking
element (2) is arranged to be held in its retracted condition by camming engagement
with the barrier member when in its second position.
1. Tankfahrzeug zum Transport von Fluiden,
umfassend ein zwischen einer ersten Stellung und einer zweiten Stellung bewegbar angeordnetes
Sperrteil, wobei das Sperrteil in der ersten Stellung eine den Anschluß einer Abgabeleitung
an ein oder mehrere Auslaßventile des Tankfahrzeugs verhindernde Lage aufweist, und
wobei in der zweiten Stellung des Sperrteils ein Zugriff auf das Ventil bzw. die Ventile
möglich ist, um daran eine Abgabeleitung anzuschließen,
gekennzeichnet
durch eine pneumatisch betreibbare Blockiereinrichtung (1) für das Sperrteil, die
ein das Sperrteil in der ersten Stellung haltendes Blockierelement (2) umfaßt, welches
auf ein an die Blockiereinrichtung (1) angelegtes pneumatisches Signal ansprechend
zurückziehbar ist, um das Sperrteil freizugeben,
und eine pneumatische Steuereinrichtung mit ersten und zweiten pneumatischen Schaltern
(7, 8), die zur Betätigung einer die Befüllung des Tankfahrzeugs über das Auslaßventil
bzw. die Auslaßventile ermöglichenden Einrichtung und zur Betätigung einer eine Bewegung
des Tankfahrzeugs verhindernden Einrichtung jeweils auf die Rückzugsbewegung des Blockierelementes
ansprechend betreibbar sind, wobei der erste Schalter (7) über wenigstens einen manuell
betätigbaren Hauptausschalter der Steuereinrichtung mit einer pneumatischen Druckquelle
verbunden ist und der zweite Schalter unabhängig von dem Hauptausschalter mit derselben
oder einer weiteren pneumatischen Quelle verbunden ist.
2. Tankfahrzeug nach Anspruch 1, wobei die eine Bewegung des Tankfahrzeugs verhindernde
Einrichtung dazu eingerichtet ist, die Bremse(n) des Tankfahrzeugss zu betätigen.
3. Tankfahrzeug nach Anspruch 1, wobei die eine Bewegung des Tankfahrzeugs verhindernde
Einrichtung dazu eingerichtet ist, die Inbetriebsetzung der Motorzündung zu unterbinden.
4. Tankfahrzeug nach Anspruch 1, wobei die eine Bewegung des Tankfahrzeugs verhindernde
Einrichtung dazu eingerichtet ist, die Inbetriebsetzung einer elektrischen Motor-Starterschaltung
zu unterbinden.
5. Tankfahrzeug nach wenigstens einem der vorhergehenden Ansprüche, wobei die die Befüllung
ermöglichende Einrichtung eine pneumatisch ansprechende elektrische Schalteinrichtung
(5) umfaßt, die in einer elektrischen Speiseschaltung für eine Fluideinlaßpumpeinrichtung
für das Tankfahrzeug vorgesehen ist, wobei die Pumpeinrichtung nur in Betrieb gesetzt
werden kann, wenn die Schalteinrichtung (5) infolge eines von dem mit der Sperrteilblockiereinrichtung
(1) in Verbindung stehenden ersten Schalter (7) an sie abgegebenen pneumatischen Signals
eingeschaltet worden ist.
6. Tankfahrzeug nach Anspruch 5, wobei die elektrische Schalteinrichtung (5) ferner von
einer mit einer Dampfablaßleitungsverbindung des oder jedes Fluidbehälters des Tankfahrzeugs
zusammenwirkenden und auf einen im oberen Bereich des Behälters angeordneten Fluidsensor
ansprechenden pneumatischen Schalteinrichtung (6) gesteuert wird.
7. Tankfahrzeug nach wenigstens einem der vorhergehenden Ansprüche, wobei die Sperrteilblockiereinrichtung
(1) sowie die auf die Bewegung des Blockierelementes (2) ansprechenden ersten und
zweiten Schalter (7, 8) der Steuereinrichtung Teile einer gemeinsamen Einheit bilden.
8. Tankfahrzeug nach Anspruch 7, wobei die Einheit ein eine längliche Bohrung (11) begrenzendes
Gehäuse (30) und einen in der Bohrung gleitbeweglich angeordneten Kolben (12) umfaßt,
wobei ein freies Ende des Kolbens aus dem Gehäuse herausragt und das Blockierelement
(2) bildet oder mit dem Blockierelement (2) verbunden ist, wobei ferner der erste
pneumatische Schalter (7) und der zweite pneumatische Schalter (8) jeweils axialen
Abstand voneinander aufweisende, mit der Bohrung kommunizierende Einlaß- und Auslaßöffnungen
(13, 14; 15, 16) und Dichtmittel (20) aufweist, die mit dem Kolben in Verbindung stehen
und dazu eingerichtet sind, die jeweiligen Öffnungen im blockierten Zustand des Elementes
voneinander zu isolieren und bei zurückgezogenem Blockierelement (2) die Kommunikation
der jeweiligen Öffnungen untereinander herzustellen, und wobei das Gehäuse ferner
eine Einlaßöffnung (13) umfaßt, die mit der Bohrung kommuniziert und für die Anlegung
eines pneumatischen Signals zum Zurückziehen des Kolbens vorgesehen ist, um das Blockierelement
freizugeben.
9. Tankfahrzeug nach Anspruch 8, wobei die Einlaßöffnung (13) mit der Einlaßöffnung (13)
des ersten pneumatischen Schalters (7) der Einheit übereinstimmt.
10. Tankfahrzeug nach Anspruch 8 oder 9, wobei der Kolben (12) gegen die Kraft einer vorspannenden
Feder (21) bewegt wird.
11. Tankfahrzeug nach wenigstens einem der Ansprüche 7 bis 10, wobei das Blockierelement
(2) in seinem zurückgezogenen Zustand durch steuernden Eingriff mit dem Sperrteil
gehalten ist, wenn letzteres in seiner zweiten Stellung ist.
1. Citerne de transport de fluide comprenant un organe formant obstacle, agencé pour
se déplacer entre une première position dans laquelle il est situé de manière à empêcher
la connexion d'un conduit de décharge à une ou plusieurs vannes de sortie de la citerne,
et une seconde position dans laquelle on peut accèder à ladite vanne ou auxdites vannes
pour connecter un conduit de distribution à celle-ci,
caractérisée en ce qu'elle comporte des moyens (1) de verrouillage de l'organe formant
obstacle, actionnables pneumatiquement, comprenant un élément de verrouillage (2)
agencé pour retenir l'organe dans sa première position, ledit élément (2) étant rétractable
en réponse à un signal pneumatique appliqué aux moyens de verrouillage (1) pour libérer
l'organe formant obstacle, les moyens de commande pneumatique comportant un premier
et un second commutateurs (7, 8) pneumatiques actionnables respectivement en réponse
à un mouvement de rétraction de l'élément de verrouillage (2) pour actionner des moyens
permettant de réaliser le remplissage de la citerne par l'intermédiaire de la ou des
vannes de sortie et pour actionner des moyens empêchant le déplacement de la citerne,
le premier commutateur (7) étant relié à une source de pression pneumatique par l'intermédiaire
d'au moins un commutateur principal de coupure des moyens de commande, actionnable
manuellement, et le second commutateur étant relié à la même source pneumatique ou
à une autre source pneumatique indépendamment du commutateur de coupure.
2. Citerne de transport de fluide selon la revendication 1, dans laquelle les moyens
empêchant le déplacement de la citerne sont adaptés pour appliquer les freins de la
citerne.
3. Citerne de transport de fluide selon la revendication 1, dans laquelle les moyens
empêchant le déplacement de la citerne sont prévus pour mettre hors service l'allumage
du moteur.
4. Citerne de transport de fluide selon la revendication 1, dans laquelle les moyens
empêchant le déplacement de la citerne sont prévus pour mettre hors service un circuit
électrique de démarrage de moteur.
5. Citerne de transport de fluide selon l'une quelconque des revendications précédentes,
dans laquelle les moyens permettant de réaliser le remplissage comportent des moyens
(5) formant commutateur électrique sensible pneumatiquement, agencé dans un circuit
d'alimentation électrique de moyens de pompage d'entrée de fluide de la citerne, de
telle sorte que les moyens de pompage peuvent seulement être actionnés lorsque les
moyens formant commutateur (5) sont mis en position de marche par réception d'un signal
pneumatique provenant du premier commutateur (7) associé aux moyens (1) de verrouillage
de l'organe formant obstacle.
6. Citerne de transport de fluide selon la revendication 5, dans laquelle les moyens
(5) formant commutateur électrique sont également commandés par des moyens (6) formant
commutateur pneumatique en réponse à la connexion d'un conduit de sortie de vapeur
du réservoir ou de chaque réservoir de fluide de la citerne, et à un capteur de fluide
prévu au sommet du réservoir.
7. Citerne de transport de fluide selon l'une quelconque des revendications précédentes,
dans laquelle les moyens (1) de verrouillage de l'organe formant obstacle et le premier
et le second commutateurs (7, 8) pneumatiques des moyens de commande sensibles à un
mouvement de l'élément (2) de verrouillage des moyens de verrouillage forment une
partie d'un ensemble commun.
8. Citerne de transport de fluide selon la revendication 7, dans laquelle l'ensemble
comprend un boîtier (30) définissant un alésage allongé (11) et un piston (12) monté
coulissant dans l'alésage, une extrémité libre du piston étant agencée pour faire
saillie à partir du boîtier et constituant une connexion ou étant reliée audit élément
de verrouillage (2), le premier et le second commutateurs (7, 8) pneumatiques comprenant
chacun respectivement des orifices d'entrée et de sortie écartés axialement (13, 14
; 15, 16) communiquant avec l'alésage et des moyens d'étanchéité (20) associés au
piston et agencés pour isoler les orifices respectifs l'un par rapport à l'autre dans
la position verrouillée dudit élément et pour mettre en communication les orifices
respectifs les uns avec les autres lorsque l'élément de verrouillage (2) est rétracté,
le boîtier comprenant en outre un orifice d'entrée (13) communiquant avec l'alésage
et prévu pour l'application d'un signal pneumatique destiné à rétracter le piston
de façon à relâcher l'élément de verrouillage.
9. Citerne de transport de fluide selon la revendication 8, dans laquelle ledit orifice
d'entrée (13) est commun avec l'orifice d'entrée (13) du premier commutateur (7) pneumatique
de l'ensemble.
10. Citerne de transport de fluide selon la revendication 8 ou 9, dans laquelle le piston
(12) est déplacé à l'encontre de la force exercée par un ressort de sollicitation
(21).
11. Citerne de transport de fluide selon l'une quelconque des revendications 7 à 10, dans
laquelle ledit élément de verrouillage (2) est agencé pour être maintenu dans son
état rétracté par contact avec effet de came avec l'organe formant obstacle lorsque
celui-ci est dans sa seconde position.

