Solenoid valve for irrigation control units

Abstract: A solenoid valve for an irrigation control unit comprises a cut-off element (7) movable inside a respective seat (25, 26) between a closed position and an open position; the cut-off element (7) defines inside the seat (25, 26) a chamber (26) in constant communication with the inlet (2) of the solenoid valve, so that the pressure exerted on the cut-off element (7) by the water present at the inlet of the solenoid valve is balanced by the pressure exerted on the cut-off element (7) by the water present in the chamber (26), the cut-off element (7) is provided with a passing conduit (12) that can be opened so that the chamber (26) can be put in communication with the outlet (3) of the solenoid valve so that, since the pressure exerted on the cut-off element (7) by the water present at the inlet of the solenoid valve is no longer balanced by the pressure exerted on the cut-off element (7) by the water present in the chamber (26), the cut-off element (7) is displaced by the thrust of the water present at the inlet of the solenoid valve in said open position; the solenoid valve also comprises a bistable electromagnetic device (14-22) comprising an electromagnetically-operated valve suitable for determining alternatively the closing and the opening of said passing conduit (12) as a result of the generation of an electrical control impulse and up to the generation of an opposite electrical impulse.

Description: The present invention relates to a solenoid valve for irrigation control units. In the gardening sector, automatic timed irrigation systems provided with control devices that can be programed by the user are increasingly gaining ground. Such devices comprise substantially a control unit that operates one or more solenoid valves. The solenoid valves comprise a hydraulic element for cutting-off the flow of water, and an electromagnet for the operation of said hydraulic element. Solenoid valves for irrigation control units should meet very specific requisites: for example, they should have a small size, they should not require any maintenance, they should have a very low consumption of electrical energy, and they should also operate with a very low water pressure (this occurs when the water to be used for irrigation is provided by a tank where rain water is collected). The object of the present invention is to provide a solenoid valve for irrigation control units that meets the above requisites. US-A-4502661 discloses a solenoid valve according to the preamble of claim 1. FR-A-2602299 discloses a bistable electromagnetic device for actuating a hydraulic valve. EP-A-0340625 discloses a solenoid valve having a permanent magnet at one end of a piston chamber and a metallic stop at the opposite end. According to the present invention, such object is achieved with a solenoid valve for irrigation control units comprising the further features defined in the characterizing part of claim 1. A solenoid valve according to the present invention operates substantially on the difference in pressure between the inlet and a chamber that can be put in communication with the outlet; the valve is thus reliable and does not require any maintenance. The bistable electromagnetic device allows consumption to be greatly reduced, since the solenoid valve has to be powered only for short time intervals during its closing or opening operations, but once the solenoid valve has been opened or closed there is no longer any absorption of electrical power. The features of the present invention will be made more evident by the following detailed description of an embodiment thereof, described as a non-limiting example in the enclosed drawings, wherein: Fig. 1 shows a cross-section of a solenoid valve according to the present invention, in a closed condition; Fig. 2 shows a cross-section of said solenoid valve in a condition intermediate between the closed condition and an open condition; Fig. 3 shows a cross-section of said solenoid valve in the open condition; Fig. 4 shows diagramatically an electrical circuit for driving the solenoid valve. As shown in Fig. 1, a solenoid valve according to the present invention comprises a hollow casing 1, for example in ABS, consisting of an inlet section 2, an outlet section 3 and a cut-off section 4. The cut-off section 4 comprises a first portion 5, that extends from the upper wall of the hollow casing 1, and a second portion 6 that extends from the lower wall of the hollow casing 1 so as to define a seat for a gasket 7. The gasket or out-off element 7 comprises a gasket casing 8, for example in ABS, on which a rubber membrane 9 is fastened; in the gasket casing 8 there is a hole 11 drilled as an extension of one of twelve holes 10 present in the membrane 9; in the gasket casing 8 there is also drilled, substantially in a central position, a further passing hole 12. The casing of the valve 1 also comprises a flange 13, comprising a flat part 44, that defines the seat for the gasket together with the portion 6, and a substantially cylindrical appendix 42 that defines inside it a cylindrical chamber 21 wherein a steel piston 14 slides. The piston 14 has at the upper end a rubber plug 15 that, when the piston is at the upper end of its stroke (as in Fig. 1) closes the lower mouth of the passing hole 12 of the gasket casing 8. A small helical spring 16, reacting against the flange 13, elastically urges the piston 14 in such upper end of the stroke. Under the flat part 44 of the flange 13 there is a disc 17 in galvanized steel and, below this, a permanent magnet 18, for example in barium ferrite, and a support in galvanized steel 19. Inside the support 19, round the cylindrical part of the flange 13, there is an electrical winding (coil) 20. On the bottom of the cylindrical chamber 21, fastened to the support 19 by means of a nut 46, there is a steel anchor pin, provided with a circular groove 23 wherein there is an O-ring 24; the anchor pin 22 also acts as a lower limit for the stroke of the piston 14. The support 19, the magnet 18, the disc 17 in galvanized steel, the small piston 14 and the anchor pin 22 constitute a magnetic circuit wherein the lines of magnetic flux generated by the winding 20 are concentrated, when an electric current flows through it. There is shown in Fig. 4 a diagrammatic representation of a possible power circuit for the solenoid valve: the electrical winding 20 is powered, through a switch 40, by a voltage generator 41 (for example a battery). The switch 40 has three operative positions (shown with a continuous line, with a dash-and-dot line and with a dash-and-two-dots line), two of which allow the connection to be made of each end of the winding 20 alternatively to either the positive pole or to the negative pole of the voltage generator 41; in this way, it is possible to invert the direction of the current in the winding 20, and as a consequence to invert the lines of the magnetic flux generated inside the winding 20. When the switch 40 is in the third operative position (shown with a line with one dash and two dots) the winding 20 is disconnected from the voltage generator 41. When the solenoid valve is in the closed condition, that is when the piston 14 is in the position of the upper end of its stroke shown in Fig. 1, the plug 15 closes the lower mouth of the passing hole 12 in the gasket casing 8. Any water present in the inlet section 2 of the casing 1 cannot flow into the outlet section 3, since the membrane 9 is up against the first and the second portion 5, 6; but the second portion 6 is shaped so as to define an annular chamber 25 in communication with the inlet setion 2, and thus water present in the inlet section 2, flowing through the holes 10 and 11, penetrates inside a second chamber 26 under the gasket casing 8, defined at its lower end by the flat part 44 of the flange 13 and at its upper end by the gasket casing 8. Since the pressure of the water in this second chamber 26 is equal to the pressure in the inlet section 2 and in the chamber 25, the thrust exerted on the membrane 9 from above is balanced by the thrust exerted on the gasket casing 8 from below: thus, the gasket 7 is kept in the closed position by a balance of pressures, and the small thrust exerted by the helical spring 16 on the piston 14 ensures that the plug 15 closes the mouth of the hole 12. In order to determine the opening of the solenoid valve, the winding 20 is connected to the voltage generator 41, for example by placing the switch 40 in the position shown with a continuous line in Fig. 4. The current that circulates in the winding 20 generates a magnetic field whose lines of flow are concentrated in the magnetic circuit constituted by the support 19, by the magnet 18, by the small piston 14 and by the anchor pin 22; such magnetic field determines the downward sliding movement of the small piston 14, that moves to the position of Fig. 2, where it is held by the pin 22. Since the magnet 18 has a stable magnetisation, the winding 20 can be disconnected from the generator 41 (by moving the switch 40 to the position shown with a the dash-and-two-dots line in Fig. 4). With the piston 14 in this position, the lower mouth of the hole 12 in the gasket casing 8 is open, and the chamber 26 is in communication with the outlet section 3 of the casing 1: the pressure exerted by the water on the membrane 9 is no longer balanced by the pressure exerted by the water present in the chamber 26 on the gasket casing 8, and thus the gasket casing 8 nmoves downward, opening a passage between the inlet section 2 and the outlet section 3 of the casing 1 (Fig. 3). When the solenoid valve is to be closed, the winding 20 is once again connected to the voltage generator 41 by putting the switch 40 in the position shown with a dash-and-dot line in Fig. 4: the direction of circulation of the current in the winding 20 is opposite to that of the previous case, and as a consequence the direction of the magnetic field is also opposite; the small piston 14 is taken back to the position of Fig. 1, wherein it is maintained even after the winding 20 has been disconnected from the voltage generator 41 thanks to the fact that the magnet 18 attracts the piston 14 in a direction opposite to the previous one; the upward movement of the piston 14 determines the upward movement of the gasket casing 8, that is once again taken to the position where the solenoid valve is closed.

Claims: A solenoid valve for an irrigation control unit comprising a cut-off element (7) movable inside an annular chamber (25, 26) between a closed position and an open position wherein one inlet (2) of the solenoid valve communicates with an outlet (3) of the same, said cut-off element (7) defining inside said annular chamber (25, 26) a first chamber (25) in constant communication with the inlet (2) of the solenoid valve, said chamber (25) being in communication with a second chamber (26) via a hole (10, 11) so that the pressure exerted on the cut-off element (7) by the water at the inlet of the solenoid valve is balanced by the pressure exerted on the cut-off element (7) by the water in the second chamber (26), said cut-off element (7) being also provided with a passing conduit (12) that can be opened so that said second chamber (26) can be put into communication with the outlet (3) of the solenoid valve so that, since the pressure exerted on the cut-off element (7) by the water at the inlet of the solenoid valve is no longer balanced by the pressure exerted on the cut-off element (7) by the water in the second chamber (26), the cut-off element (7) is displaced by the thrust of the water at the inlet of the solenoid valve in said open position, characterized in that the solenoid valve further comprises a bistable electromagnetic device (14-22) including a movable valve member (14) for causing alternately closing and opening of said passing conduit (12) as a result of the generation of opposite electrical control pulses, said movable valve member (14) comprising a metal piston (14) slidingly movable within a fixed casing (42) between a first position, in which said piston (14) protrudes from one end of the fixed casing (42) and engages the cut-off element (7) to close the passing conduit (12), and a second position, in which said passing conduit (12) is open, electrical coil (20) arranged around the fixed casing (42) and within a one-piece metallic support (19) which is laterally open along at least one side and which has first and second parallel planar legs perpendicular to a longitudinal axis of the fixed casing (42) and integrally connected to each other by a lateral connecting wall, a metallic anchor pin (22) extending into another end of the fixed casing (42) and fixed to a first one leg of the support (19) to provide a stop element for the piston (14) in said second position, pulse supplying means (40, 41) for alternately supplying electrical control pulses of opposite sign to said electric coil (20) to said first and second positions, respectively, and a permanent magnet (18) fixed externally of the second leg of the support (19) to keep the piston (14) in said first or second position, respectively, after the end of each control pulse and until a next pulse. A solenoid valve according to claim 1, characterized in that said annular chamber (25, 26) is defined in a valve casing (1) by a plurality of valve casing portions (5, 6) and said cut-off element (7) comprises a casing (8) slidably housed in said annular chamber (25, 26) and provided with said passing conduit (12), and a membrane (9) superimposed over and fastened to said casing (8), said membrane (9) cooperating with said valve casing portions (5, 6) to ensure sealing between said inlet (2) and outlet (3) of the solenoid valve.

Inventors: PASUT CLAUDIO, PASUT, CLAUDIO
Applicants: CLABER SPA, CLABER S.P.A.
Application year: 1995
Main classification: F16K31
IPC codes: F16K31, A01G25