GB2268833A

GB2268833A - Improved digitally controlled solenoid valve

Info

Publication number: GB2268833A
Application number: GB9313537A
Authority: GB
Inventors: Giorgio Bergamini; Venanzio Mininni
Original assignee: Nuovopignone Industrie Meccaniche e Fonderia SpA; Nuovo Pignone SpA; Eniricerche SpA
Current assignee: Nuovo Pignone Holding SpA; Eni Tecnologie SpA; Nuovo Pignone SpA
Priority date: 1992-07-15
Filing date: 1993-06-30
Publication date: 1994-01-19
Anticipated expiration: 2013-06-30
Also published as: GB9313537D0; FR2693785B1; IT1255342B; JPH0658452A; ITMI921714A0; DE4322840A1; ITMI921714A1; FR2693785A1; GB2268833B

Abstract

The circuit comprises a transistor 21 connected to one end 15 of a coil 13 and a current limiting resistor 19 connected to the other end 14 of the coil. In order to open the orifice 3 of the valve, a control signal is applied to terminal 27 thereby switching on the transistor and discharging a capacitor 24 through the coil. An armature 10 is attracted to core 12 against the bias of a spring 9 to open the valve. When an inhibit signal is applied to the terminal 27, the transistor is switched off and the spring urges the armature into a valve closing position. <IMAGE>

Description

b IMPROVED DIGITALLY CONTROLLED SOLENOID VALVE This invention relates to a

new digitally controlled solenoid valve which, by using a transistor for its digital control and the discharge of a capacitor for moving its valving member, achieves efficient operation with low absorbed power, hence enabling it to be applied to all cases in which only a very small power is available. Various types of digitally controlled solenoid valves are already known in the state of the art. In one known type of solenoid valve, the valving member which closes the nozzle orifice by the action of a preloaded spring is rigid with the armature of an electromagnet, the coil of which is energized by a digital control unit when required.

Such a known solenoid valve has however the drawback of requiring considerable power for overcoming the action of said preloaded spring in order to withdraw the valving member from the nozzle orifice, with the result that this type of solenoid valve cannot be used where only a small electrical power is available, such as in the case of intrinsically safe instrumentation, and more so in the case of remote powering. This drawback is encountered in all known typesof solenoid valves, which always require a fairly high power for their operation. The object of the present invention is to obviate the aforesaid drawback by providing a digitally controlled solenoid valve of very low power absorption, therefore requiring very low electrical power for its operation. This is substantially attained in that most of the electrical power required during the opening of the valve to attract the armature and hence move the valving member against the action of the preloaded spring is provided by the rapid discharge of a capacitor, so that only a very small current and hence a very small electrical power is required to maintain the armature in its attracted position, rapid reclosure of the solenoid valve being ensured not only by the action of said preloaded spring but also by short-circuiting the electromagnet coil by a suitably orientated diode. Hence the digitally controlled solenoid valve, comprising a nozzle cooperating via a preloaded spring with a valving.member.rigid with the armature of a fixed electromagnet operated by digital control, is characterised according to the invention in that the two ends of the coil of said electromagnet are connected respectively to a first pole of the d.c. electrical power unit via a first limiting resistor, and to the emitter of a pnp transistor, the collector of which is connected to the.-other pole of said power unit, its base being connected to the digital control unit via a second limiting resistor, said two ends of the coil also being connected together via a diode orientated towards said first pole of the power unit, a capacitor being connected between said first limiting resistor and said collector of the transistor. Again, in order to reduce to a minimum the sensitivity of the moving part of said solenoid valve to vibration and impact, according to a preferred embodiment of the present invention said valving member is made rigid with the end of a balanced rocker lever which is pivoted on the valve body and has its other end acting as the armature for said electromagnet. In this manner the easily achieved perfect balancing of said rocker lever ensures that any axial acceleration to which the solenoid valve may be subjected cannot cause the moving part of the solenoid valve to undergo angular movement, leading to possible leakage from the valving member. The invention is described in detail hereinafter with reference to the accompanying drawing, which illustrates a preferred embodiment thereof by way of non-limiting example in that technical or constructional modifications can be made thereto without leaving the scope of the present invention. For-example., instead of a pnp transistor, an npn transistor can be used, in which case the electrical feed polarity has to be reversed; again, instead of being a simple hinge, the fulcrum of said rocker lever can be formed with one or more flexible foils mounted preloaded in order to also perform the function of said preloaded spring. In said drawing, which represents a section through a digitally controlled solenoid valve according to the invention, the reference numeral 1 indicates the body of the solenoid valve and 2 the nozzle, the orifice 3 of which connects the inlet duct 4 to the outlet duct 5. Said orifice 3 is closed by the valving member 6 which, provided with an elastic seal element 7 and a balancing counterweight 8, is pressed against the nozzle 2 by a preloaded spring 9, and is rigid with one end of a rocker lever 10, which is hinged at 11 to the body 1 and has its other end 10' acting as the armature for the electromagnet 12. The two ends 14 and 15 of the coil 13 of said electromagnet 12 pass through the insulators 16 and emerge into the chamber 17 provided in the valve body 1, where they are connected 18 respectively to the positive pole/of a d.c. power unit, not shown in the figure, via the current limiting resistor 19, and to the emitter 20 of a pnp transistor 21, the collector 22 of which is connected to the earth pole 23 of said power unit. A capacitor 24 is connected in parallel with the power unit downstream of said resistor 19, and the base 25 of said transistor 21 is connected via a current limiting resistor 26 to a digital control unit, not shown in the figure, connected between the poles 27 and 23. Finally, said two ends 14 and 15 of the coil 13 are connected together via a diode 28 orientated towards the pole 18. The solenoid valve operates in the following manner. When the solenoid valve is to be opened, a digital signal is fed to the pole 27 and saturates the transistor 21 to close the power circuit to the coil 13, the capacitor 24 then discharging to provide the excess current necessary to attract the armature 101 and hence withdraw the valving member 6 from the nozzle 2. After said armature 101 makes contact with the electromagnet 12, the - 5 small current provided by the power unit to the poles 18 and 23 is sufficient to maintain said contact between the armature and the electromagnet. When the digital signal for inhibiting the transistor 21 is fed to the pole 27, said power circuit to the coil 13 is opened with the result that current no longer circulates, so that the spring 9 is able to move the valving member 6 against the nozzle 2 and hence close the solenoid valve. Simultaneously the capacitor 24 is recharged by said d.c. power unit, the diode 28 accelerating the 10 dissipation of the energy still present in the coil 13 by shortcircuiting the coil.

1. A digitally controlled solenoid valve, comprising a nozzle cooperating via a preloadable urging means with a valve member operable by the armature of an electromagnet operable by digital control, wherein the two ends of the coil of the electromagnet are connected respectively to a first pole of a DC electrical power unit via a first limiting resistor and to the emitter of a pnp transistor the collector of which is connected to the other pole of the power unit and the base of which is connectable to a digital control unit via a second limiting resistor, wherein said two ends of the coil are also connected together via a diode orientated towards said first pole of the power unit, and wherein a capacitor is connected between said first limiting resistor and said collector of the transistor.

2. A digitally controlled solenoid valve as claimed in claim 1, wherein the valve member is fixed to one end of a rocker lever which is pivoted on the body of the valve and has its other end acting as the armature for the electromagnet.

Claims

3. A modification of a digitally controlled solenoid valve is claimed in

claim 1 or 2, wherein the pnp transistor is replaced by an npn transistor.

4. A digitally controlled solenoid valve as claimed in claim 1 or 3, substantially as hereinbefore described with reference to, and as shown in, the drawing.