EP1274646B1

EP1274646B1 - An automatically closing control valve for the delivery of liquids

Info

Publication number: EP1274646B1
Application number: EP01933717A
Authority: EP
Inventors: Giorgio Bacchio
Original assignee: Universita degli Studi di Pavia
Current assignee: Universita degli Studi di Pavia
Priority date: 2000-03-16
Filing date: 2001-03-16
Publication date: 2003-10-01
Anticipated expiration: 2021-03-16
Also published as: IT1317629B1; AU2001260131A1; WO2001068508A1; ATE251084T1; DE60100902D1; US20030089422A1; EP1274646A1; ITMI20000539A1

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

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.
An other type of control valve is disclosed in CH-A-355 045 and corresponds to the preamble of claim 1.

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, according to claim 1.
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.
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 the valve, according to the invention;

Detailed description of some preferred embodiments

With reference to the figure 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.
Advantageously, a nonreturn valve may be inserted in the probe (12) 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, all the results sought in the introduction are reached, resulting in clear advantages in terms of use and reliability of the valve.

Claims

An automatically closing control valve (1) for the delivery of liquids, particularly for low pressure delivery circuits, comprising a main casing (2), a liquid entry aperture (3') and a liquid exit aperture (4') connected to a duct (4) with a section (4") shaped as a Venturi tube, to generate a vacuum in pneumatic actuation means (15, 16) upon the passage of the liquid, a main internal chamber (5) of substantially cylindrical shape, in which a piston (6) slides along the axial direction of said main chamber (5), said piston defining, with its sliding movement, at least one opening and one closing position of said liquid entry (3') and exit (4') apertures, said valve (1) also comprising return elastic means (10) of said piston (6) towards said closing position, pneumatic holding means (11) for holding said piston (6) in said opening position, comprising an open duct (12) for monitoring the reaching of a predetermined maximum level of liquid delivered into a container (B), an end of which is suitable to be closed by said liquid, operatively connected to said pneumatic actuation means (15, 16) and suitable to interact with said pneumatic holding means (11) to control the activation of said return elastic means (10) to put said piston (6) in a closing position upon reaching said predetermined level of liquid delivered characterised in that said pneumatic holding means (11) produce a vacuum in said main internal chamber (5) to hold said piston (6) in an opening position and said pneumatic actuation means (15, 16) actuate valve means (17) suitable to open a passage between main internal chamber (5) and the surrounds of the valve in one position and to interrupt communication between said main internal chamber (5) and the external surrounds of the valve itself in a second position.
A valve according to claim 1, in which said valve means (17) are operated to interrupt said communication by means of spring means and to open said communication by means of a second membrane (16), deformable by the vacuum created in a second pneumatic chamber (15) communicating with said Venturi tube.
A valve according to claim 2, in which said return elastic means of said piston (6) in a closing position are mechanical springs (10).