AN AUTOMATICALLY CLOSING CONTROL VALVE FOR THE DELIVERY OF LIQUIDS

Abstract: An automatically closing control valve for liquids which includes entry (3') and exit (4') apertures and an internal chamber (5) in which a piston (6) that opens and closes the entry (3') and exit (4') apertures slides. The valve (1) has springs (10, 20) that closes the piston (6), mechanical or pneumatic means (11, 22, 23) to keep the piston (6) open and a monitoring probe (12, 26). The probe (12, 26) communicates with pneumatic means (15, 16, 28, 29) that keep the piston (6) in an opened position and that operate the springs (10, 20) that returns the piston (6) upon reaching maximum level. The aperture (4') is connected to the nozzle (4'') shaped as a Venturi tube, which creates the vacuum to activate the pneumatic means (15, 28).

Description: AN AUTOMATICALLY CLOSING CONTROL VALVE FOR THE DELIVERY OF LIQUIDS Field of the invention The present invention refers to an automatically closing control valve for the delivery of liquids, in particular for low pressure delivery circuits in which the liquid is delivered due to gravity. State of the art Circuits for the low pressure distribution of liquids are used in applications where large liquid flows are unnecessary. For examples, in research and experimentation laboratories, relatively small containers are filled with different liquids, e.g. water or other. The ducts of the hydraulic distribution system of the liquid have interception taps or valves, that may be opened manually or automatically and are equipped with safety devices to automatically close the tap or valve upon reaching the desired level in the container or vessel, thus avoiding liquid spilling over the edge resulting in damage to the surrounding area, especially when using corrosive liquids. The known safety systems assembled on ducts or on the valves themselves for their automatic closure are quite complexes devices which makes them expensive to produce. Embodiments of these types of safety mechanisms are found in the field of pump pistol grips for fuel distribution. The international patent application WO-A-9911566 shows a pistol grip of this kind for fuel distribution. However, this valve type, because of its complexity, is unsuitable for use in distributing circuits of liquids in laboratory installations where economic considerations are important. Summary of the invention Therefore the present invention aims to obviate the above mentioned drawbacks of the known valves which automatically close liquid distribution circuits upon reaching a predetermined liquid level, especially in the case of circuits operating at low pressure. One of the main aims of the present invention is to produce a valve with high operating reliability and structural simplicity including a minimum number of component parts. A further aim of the present invention is to produce a valve that is also cheap to produce. These aims are reached by an automatically closing control valve for the delivery of liquids, particularly in low pressure delivery circuits, which according to claim 1 , includes a main casing, an entry and an exit aperture of the liquid, a main internal chamber of basically cylindrical shape, in which a piston slides along the axial direction of said main chamber, said piston defining, with its movement, at least one opening and one closing position of said entry and exit apertures, said valve also having return elastic means of said piston towards said closing position, holding means of said piston in an opening position and monitoring means of a predetermined maximum level of liquid delivered into a container, characterised in that said monitoring means are operatively connected to pneumatic actuation means suitable to interact with said means holding said piston in an opening position to control the activation of said return elastic means to put the same piston in a closing position when said predetermined maximum level of delivered liquid is reached. Due to such an arrangement, the valve interrupts the delivery of the liquid upon reaching the desired level in the container in an automatic and reliable way, though presenting a simple configuration. Advantageously, in the valve a duct, having a section shaped as a Venturi tube is connected to said exit aperture to generate, upon passage of the liquid, a vacuum in said pneumatic actuation means. This arrangement creates the vacuum necessary to operate the pneumatic control means of the valve in a simple and reliable way. Brief description of the figures Further aims and advantages of the present invention will become more apparent in view of the detailed description of preferred, but non-exclusive, valve embodiments, shown as explanatory, non-limiting examples, with the help of the enclosed drawings in which: figure 1 represents a sectional view of a first embodiment of the valve, according to the invention; figure 2 represents a sectional view of a second embodiment of the valve, according to the invention. Detailed description of some preferred embodiments With reference to the figures mentioned, a valve, denoted as a whole, by 1 includes a main casing 2, basically of elongated form and set in a basically horizontal position during operation. A duct 3 of liquid entry, connected to a hydraulic circuit of known type and not shown in the figures, is connected to an entry aperture or port 3' made in the upper part of the valve casing. In the lower part of the valve is connected an exit duct or nozzle 4, set in a basically vertical position, that supplies a container B with liquid, flowing due to gravity in the direction of arrow S. The interior of the valve casing bears, for most of its length, a cylindrical chamber 5 in which is set a piston 6 which may move inside said chamber 5. The piston has rubber rings 7 which ensure a goods seal with the internal walls of the chamber 5. The piston 6 is secured to a control rod 8 which bears a knob 9 or similar, at its end external to the valve, which can be operated by pressure exerted manually or with an actuator used by the operator. The rod 8 is kept in an extracted position by a spring 10, which in figure 1 is positioned to the left of the valve. In this position, the piston 6 totally blocks both apertures 3', 4' of ducts 3, 4 completely closing the passage of the liquid. When the operator pushes the knob 9 of rod 8 sliding the piston towards the right-hand part of figure 1 , the ducts 3 and 4 communicate with each other and the liquid starts to flow through valve 1. The end section 4" of the duct 4 is shaped as a Venturi tube. In flowing inside the nozzle 4", the liquid creates a Bernoulli effect which transmits a vacuum through duct 11 to the right-hand part of the chamber 5. The force exerted by the vacuum acts on the piston 6 and counterbalances the returning action of the spring 10, keeping the rod 8 in a recessed position in the casting 2 and the piston 6, shifted towards the right-hand part in relation to the figure, keeps the entry duct 3 in communication with the exit duct 4. A duct 12, which is considerably narrower that duct 11 , is set in a basically vertical position in relation to the liquid level in container B. Its upper aperture leads into duct 11. The duct 12 serves as a probe through which a flow of air is generated, directed upwards in the direction of the arrow 14, by the vacuum created in the nozzle 4". As long as the liquid flows between the ducts 3 and 4, passing through the left part of chamber 5 in relation to piston 6, the Bernoulli effect is maintained in nozzle 4" which balances the effect of spring 10 and the piston stays in a balanced open position. A second duct 13, one end of which is connected to the probe 12 and its other end is connected to a chamber 15, acts on a membrane 16 which controls a valve 17. This valve 17 is kept in a closing position by a spring 18 which closes a duct 19 which puts the chamber 5 in communication with the outside, where atmospheric pressure is generally present, through apertures not shown in the figure. As long as the probe 12 does not come into contact with the liquid, its lower aperture stays free and a large amount of the force generated by the vacuum acts through duct 11 on the piston 6. The distribution of the passage of the vacuum through the various ducts is obtained through appropriate choice of the dimension of the sections of ducts 11 , 12 and 13. The probe 12 thus acts as a by-pass duct and the amount of vacuum transmitted instead through the duct 13 in the second chamber 15 is insufficient to compress the spring 18, allowing the valve 17 to open. When the lower end of the probe 12 is reached by the liquid level delivered into container B by main duct 4, its aperture closes and the air flow which ran in the same duct 12 is thus interrupted. The vacuum present in duct 12 tends to suck the liquid in it upwards, but a priority action is caused in duct 13 since the liquid density is greater than that of the air and therefore the vacuum is diverted into the second chamber 15 through tube 13. The vacuum builds up due to the passage of the liquid inside nozzle 4" and this increase of the vacuum in the chamber 15 is sufficient to produce a force acting on the membrane 16 which, becoming deformed, is able to compress the spring 18. Hence, valve 17 is moved by the membrane 16 and opens the duct 19 allowing the external air to flow into chamber 5 since the pressure inside it rises to that of atmospheric level. The piston 6 is pushed towards the left part, due to the concurrence of the returning action of spring 10 and of the pressure acting in the right-hand part of chamber 5, and simultaneously closes the entry and exit apertures (3', 4'). The valve 1 is thus automatically brought back to its closing position in which the piston 6 is towards the left part of the figure. As long as the probe 12 stays closed by contact with the liquid surface in container B, the valve 1 cannot be opened again, unless knob 9 is kept pressed by an operator, since the vacuum which should prevail in ducts 11 and 13 is insufficient to keep the piston 6 in a moved position towards the right-hand part of the chamber 5. It is necessary to ensure suitable dimensions of all duct and holes sections present in the various parts, in order to produce a valve delay system. This avoids that, during the transitory stage of piston closure, the flow of liquid that runs through ducts 3 and 4 does not reduce the vacuum in duct 13 by such as amount for which the elastic force of the spring 18 would prevail, closing the duct 19 which would take the piston 6 once again towards the right, reopening communication between the delivery ducts 3 and 4. The system would then become unstable. With particular reference to the embodiment of the valve shown in figure 2, though staying within the scope of the invention, it has some structural differences shown before. The parts corresponding to those of the embodiment of figure 1 are denoted by the same reference numbers. The piston 6 in its rest position, shown in figure 2, prevents communication between the delivery ducts 3 and 4. A spring 20 keeps the piston in this closing position. A rod 21 is joined at the piston 6 at its end which is internal to the chamber 5 and has a knob 9 at its other end. The rod 21 is pulled to the right side in figure 2, acting against the force exerted by spring 20, to put the delivery ducts 3 and 4 in communication with each other. The rod 21 also has a tooth 22, axially protruding from the external surface, which beats against an end 25 of a lever 23, fixed around a fulcrum to the frame of valve 1 at point 24, when the rod 21 reaches the extracted position to the right of the figure upon manual or automatic operation by an operator. In this position, the tooth 22 keeps the piston 6 locked in a position where the delivery ducts (3,4) are in communication with each other and the liquid is able to flow into container B. In flowing through nozzle 4, with its section 4" shaped as a Venturi tube, a Bernoulli effect is caused which transmits a vacuum towards the probe 26 open at its lower part. A second duct 27 communicates, at one end, with duct 4 and with the probe 26 in its intermediate section. Its other end is in communication with a chamber 28 closed on one side by a flexible membrane 29. The membrane 29 is connected to lever 23 by a tie rod 30 which when pressed may turn the lever 23 around the fulcrum 24. The appropriate choice of duct sections 26 and 27 ensures that during liquid delivery through valve 1 , as long as the lower section of duct 26 stays open, the vacuum generated by nozzle 4" and transmitted through duct 27 into chamber 28 is unable to deform the membrane 29 so as to turn lever 23 downwards and thus release tooth 22 of lever 21. In fact, a large part of the vacuum flows through the probe 26. When the liquid level in container B reaches the level set by the position of the lower end of probe 26, its lower aperture closes and the vacuum generated by nozzle 4" is wholly sent towards the chamber 28. The force thus generated is sufficient to deform the membrane 29 to such an extent which allows rotation of the lever 23 downwards with the consequent release of tooth 22 and freeing the rod 21 which, under the effect of spring 20, is brought back to the closing position of communication between the delivery ducts 3 and 4. The liquid flow is thus interrupted and the valve stays closed, also avoiding, in this valve arrangement, exceeding the liquid level required. Advantageously, a nonreturn valve may be inserted in the probe (12, 26) to improve the closure of the passage and avoid the liquid from being sucked back up the same probe upon reaching the maximum level. Hence, with the aforesaid valve embodiments, all the results sought in the introduction are reached, resulting in clear advantages in terms of use and reliability of the valve.

Claims: CLAIMS i 1. An automatically closing control valve for the delivery of liquids, particularly for 2 low pressure delivery circuits, including a main casing (2), an entry aperture (3') 3 and an exit aperture (4') of the liquid, a main internal chamber (5) of basically 4 cylindrical shape, in which a piston (6) slides along the axial direction of said main 5 chamber (5), said piston defining, with its movement, at least one opening and one 6 closing position of said entry (3') and exit apertures (4'), said valve (1 ) also having 7 return elastic means (10, 20) of said piston (6) towards said closing piston, holding 8 means (11 , 22, 23) of said piston (6) in an opening position, monitoring means (12, 9 26) of a predetermined maximum level of liquid delivered into a container (B) 10 characterised in the said monitoring means (12, 26) are operatively connected to π pneumatic actuation means (15, 16, 28, 29) suitable to interact with said means 12 (11 , 22, 23) holding said piston (6) in an opening position to control the activation 13 of said return elastic means (10, 20) to put the same piston (6) in a closing position 1 upon reaching said predetermined level of liquid delivered. 1 2. A valve as in claim 1 , characterised in that a duct (4) with a section (4"), having 2 a section shaped as a Venturi tube, is connected to said exit aperture (4'), to 3 generate, a vacuum in said pneumatic actuation means (15, 16, 28, 29) upon the 4 passage of the liquid. 1 3. A valve as in claim 2, characterised in that said means (12, 26) monitoring the 2 reaching of a predetermined level of liquid delivered into a container (B) include an 3 open duct (12, 26) the lower end of which is suitable to be blocked by said liquid. 1 4. A valve as in claim 3, characterised in that said means holding the piston (6) in 2 an opening position are made up of a mechanical leverage (23, 24, 30) for locking 3 the same piston (6), acting on a rod (21 ) anchored in an axial position to the piston 4 (6) itself. i 5. A valve as in claim 4, characterised in that said mechanical leverage (23, 24, 2 30) is suitable to be unlocked by the deformation of a first membrane (29) 3 operated by a vacuum generated in a first pneumatic chamber (28). i 6. A valve as in claim 3, characterised in that said means holding the piston (6) in 2 an opening position are made up of pneumatic means generating a vacuum in 3 said main chamber (5). 7. A valve as in claim 6, characterised in that valve means (17) suitable to open and interrupt communication between said main chamber (5) and the external surrounds of the valve itself are provided. 8. A valve as in claim 7, characterised in that said valve means (17) are operated to interrupt said communication by spring means and to open said communication by a second membrane (16), deformable by the vacuum created in a second pneumatic chamber (15). 9. A valve as in one or more of the previous claims, characterised in that said return elastic means of said piston (6) in a closing position are made up of mechanical springs (10, 20).

Inventors: BACCHIO GIORGIO, BACCHIO, GIORGIO
Applicants: BACCHIO GIORGIO, UNIV PAVIA, BACCHIO, GIORGIO, UNIVERSITA' DEGLI STUDI DI PAVIA
Application year: 2001
Main classification: B67D5
IPC codes: B67D5