Direct acting solenoid valve

Abstract

Direct acting solenoid valve comprising a hollow valve body (2), an obturator member (13), a movable core (12) fixedly coupled with the obturator member (13), a solenoid (10) energizable to control the movable core (12), a spring (19) configured to urge the obturator member (13) towards the valve seat (7), and a permanent magnet (21) configured to attract the movable core (12) away from the valve seat (7). The obturator member (13) is holdable in an open position by combined application of magnetic forces from the permanent magnet (21) and solenoid (10) to the movable core (12). De-energization of the solenoid (10) causes the obturator member (13) to move from the open position to a closed position. Electric power needed by the solenoid (10) to hold the obturator member (13) in the open position is lower than electric power needed by the solenoid (10) to remove the obturator member (13) from the closed position.

Description

[0001] Direct acting solenoid valve

[0002] The present invention relates to a direct acting solenoid valve, used in particular, but not solely, in household appliances.

[0003] More specifically, the invention relates to a direct acting solenoid valve of the type comprising a hollow valve body with an inlet and an outlet for the flow of a fluid, between which a chamber is formed in the valve body, wherein a valve seat is provided in the chamber, said valve seat being formed in the valve body, and wherein the valve body comprises a tubular portion connected with the chamber, an obturator member movably mounted in the chamber and cooperating with the valve seat to control fluid communication between the inlet and the outlet, said obturator being movable between a closed position in which the obturator is engaged with the valve seat, and an open position in which the obturator is away from the valve seat, a movable core fixedly coupled with the obturator member and displaceable towards and away from the valve seat, said movable core being arranged in the tubular portion, a solenoid mounted in a fixed position and surrounding the tubular portion, said solenoid being energizable to control the movable core, and resilient means configured to urge the obturator member towards the valve seat, said resilient means comprising a helical spring interposed between the valve body and the obturator element.

[0004] In household electrical appliances powered with a low-power low-voltage (LPLV) system, the electric power to solenoid valves is supplied and adjusted by a control unit of the electrical appliance. This electric power is not passively controlled by the resistance of the coil of the solenoid valve as in other, conventional power supply systems.

[0005] The LPLV system enables the hydraulic valves to be powered in two phases, i.e.: a first phase called starting, in which the movable core of the valve begins to move by action of the magnetic force generated by the coil, towards a position such as to hydraulically open the valve; a second phase called retention, in which the movable core is held in the position in which the valve is hydraulically open.

[0006] An object of the present invention is to provide a direct acting solenoid valve which is adapted for use in LPLV supply systems.

[0007] This and other objects are achieved according to the invention with a direct acting solenoid valve of the above defined type, wherein the valve further comprises a permanent magnet mounted in a fixed position and configured to attract the movable core away from the valve seat, wherein the obturator member is holdable in the open position by combined application of magnetic forces from the permanent magnet and solenoid, wherein de-energization of the solenoid causes the obturator member to move from the open position to the closed position, wherein electric power needed by the solenoid to hold the obturator member in the open position is lower than electric power needed by the solenoid to remove the obturator member from the closed position, and wherein stop protrusions extending radially inwards from a spring seat cooperate with a flange portion of the obturator element to define an innermost end-of-travel position for the obturator element, wherein this innermost end-of-travel position defines a minimum distance of the movable core from the permanent magnet such that the magnetic force applied by the permanent magnet is lower than the elastic force applied by the spring.

[0008] In view of the low power needed during the retention phase in which the movable core / obturator member is held in the open position, the amount of copper wire of the winding of the coil can be reduced and compensated by the permanent magnet, which is economically more advantageous than the amount of copper wire which is replaced by the permanent magnet.

[0009] Further features and advantages of the invention will become apparent from the detailed description that follows, provided by way of non-limiting example with reference to the accompanying Figure 1, which shows a sectional view of a direct acting solenoid valve according to the present invention.

[0010] The direct acting solenoid valve comprises a hollow valve body, indicated as a whole at 2, which in the exemplary embodiment illustrated comprises a first body portion 2a and a second body portion 2b, coupled together in a liquid-tight seal by the interposition of a sealing O-ring 3.

[0011] The first body portion 2a and second body portion 2b may be made for example of a molded plastic material.

[0012] The valve body 2 has two conduits 4 and 5, which may serve either as inlet or outlet for a flow of fluid, especially a liquid.

[0013] Between these conduits 4, 5, a chamber 6 is formed in the valve body 2. A valve seat 7 is formed in the chamber 6. The valve seat 7 is formed in the valve body 2. In particular, the valve seat 7 is formed in the first body portion 2a.

[0014] In the second body portion 2b of the valve body 2, a control coil or solenoid 10, made in a manner known per se with insulated electric wire, is mounted in a fixed position. The leads of this coil or solenoid are connected to respective terminals (not shown) for connection to a control circuit (not shown). In the embodiment shown in Figure 1, the coil 10 is wound around a reel 10a of non-magnetic material, which is assembled with a shell structure 10b of ferromagnetic material. The shell structure 10b comprises a pair of opposite tubular portions 10c, lOd which are coaxial with each other and extend inwardly from respective axial end portions lOe, lOf of the shell structure 10b. The tubular portions 10c, lOd of the shell structure 10b are configured to receive the tubular portion 2c of the valve body 2. The reel 10a carrying the coil 10 is coaxially mounted around the tubular potions 10c, lOd. The reel 10a and the coil 10 are enclosed by an insulating casing 10g with a substantially cylindrical shape.

[0015] A tubular portion 2c connected to the chamber 6 extends from the second body portion 2b of the valve body 2. Inside of the tubular portion 2c of the second body portion 2b, a movable core 12 of ferromagnetic material is mounted in a slidable manner guided by the tubular portion 2c. The movable core 12 is a piece of a substantially cylindrical shape.

[0016] One end of the movable core 12 protruding from the tubular portion 2c forms a terminal head 12a, joined to the rest of the movable core 12 by a portion of reduced diameter, in the form of a neck 12b.

[0017] Above the terminal head 12a and around the neck 12b of the movable core, an obturator member 13 is attached. A head portion of the obturator member 13 comprises a sealing element 13a which is intended to engage with the valve seat 7 when the obturator member 13 is in the closed position shown in Figure 1. In the open position (not shown), the obturator member 13 is away from the valve seat 7.

[0018] A spring seat 2d interposed between the tubular portion 2c and the chamber 6 is formed in the second body portion 2b. A helical spring 19 is interposed between the valve body 2 and the obturator element 13, in particular between a shoulder surface of the spring seat 2d and a flange portion 13b of the obturator element 13 extending radially outwards. First stop protrusions 2e extending radially inwards from a side surface of the spring seat 2d cooperate with the flange portion 13b of the obturator element to define the outermost end-of-travel position of the obturator element / movable core. Second stop protrusions 2f extending radially inwards from a side surface of the spring seat 2d cooperate with the flange portion 13b of the obturator element to define the innermost end-of-travel position of the obturator element / movable core. The helical spring 19 tends to push the assembly formed by the movable core 12 and the obturator member 13 towards the valve seat 7.

[0019] A permanent magnet 21 is mounted in a fixed position on the valve body 2. The permanent magnet 21 is configured to attract the movable core away from the valve seat 7. In the embodiment shown in Figure 1, the permanent magnet 21 is arranged at one end of the tubular portion 2c opposite to the movable core 12, in particular inside of the tubular portion 2c. According to alternative embodiments (not shown), the permanent magnet 21 could be arranged outside of the tubular portion 2c or in other positions in the valve body 2. The position in which the permanent magnet 21 is arranged is such that the magnetic force applied to the movable core 12 by the permanent magnet 21 is lower than the elastic force applied to the obturator member 13 by the spring 19 in every position of the movable core 12 and obturator member 13 between the closed position and the open position. In particular, the position of the second stop protrusions 2f define a minimum distance of the movable core 12 from the permanent magnet 21 such that the magnetic force applied by the permanent magnet 21 is lower than the elastic force applied by the spring 19 even in the innermost end-of-travel position of the movable core / obturator member.

[0020] The permanent magnet 21 defines a magnetic circuit together with the shell structure 10b, particularly with the tubular portions 10c, lOd of the shell structure 10b. Moreover, the spring 19 is arranged outside of this magnetic circuit. This provides the movable core 12 with a force characteristic which does not have a phase of decrease over the entire travel of the movable core / obturator member.

[0021] The permanent magnet 21 can be made of ferromagnetic metal or a plastic material mixed with a magnetic powder, such as plastics-bonded ferrite. In an embodiment in which the permanent magnet is made of plastic material mixed with a magnetic powder, the permanent magnet 21 can be formed as a part of the valve body.

[0022] In the de-energized condition of the control coil or solenoid 10, the direct acting solenoid valve assumes the closed position illustrated in Figure 1.

[0023] When an electric current is caused to circulate in the coil or solenoid 10 in a predetermined direction, the magnetic field correspondingly developed attracts the movable core 12 and the obturator member 13 connected thereto towards the solenoid 10, against the action of the helical spring 19, which becomes compressed. The direct acting solenoid valve switches into the open position in which the obturator 13 is away from the valve seat 7, and a liquid flow is allowed to pass between the conduits 4 and 5.

[0024] Advantageously, the obturator member 13 is held in the open position by the combined application of magnetic forces from the permanent magnet 21 and solenoid 12. Therefore, the electric power needed by the solenoid 12 to hold the obturator member 13 in the open position is lower than the electric power needed by the solenoid 12 to remove the obturator member 13 from the closed position. The electric power can thus be reduced during the phase of retention of the movable core / obturator member. When the passage of current in the coil or solenoid 10 is interrupted, the assembly formed by the movable core 12 and the obturator member 13 returns to the closed condition of Figure 1, under the action of the spring 19.

Claims

CLAIMS1. Direct acting solenoid valve comprising a hollow valve body (2) with an inlet and an outlet (4, 5) for the flow of a fluid, between which a chamber (6) is formed in the valve body (2), wherein a valve seat (7) is provided in the chamber (6), said valve seat (7) being formed in the valve body (2), and wherein the valve body (2) comprises a tubular portion (2c) connected with the chamber (6), an obturator member (13) movably mounted in the chamber (6) and cooperating with the valve seat (7) to control fluid communication between the inlet and the outlet (4, 5), said obturator member (13) being movable between a closed position in which the obturator member (13) is engaged with the valve seat (7), and an open position in which the obturator member (13) is away from the valve seat (7), a movable core (12) fixedly coupled with the obturator member (13) and displaceable towards and away from the valve seat (7), said movable core (12) being arranged in the tubular portion (2c), a solenoid (10) mounted in a fixed position and surrounding the tubular portion (2c), said solenoid being energizable to control the movable core (12), resilient means (19) configured to urge the obturator member (13) towards the valve seat (7), said resilient means comprising a helical spring (19) interposed between the valve body (2) and the obturator element (13), and a permanent magnet (21) mounted in a fixed position and configured to attract the movable core (12) away from the valve seat (7), wherein the obturator member (13) is holdable in the open position by combined application of magnetic forces from the permanent magnet (21) and solenoid (10) to the movable core (12), wherein de-energization of the solenoid (10) causes the obturator member (13) to move from the open position to the closed position, and wherein electric power needed by the solenoid (10) to hold the obturator member (13) in the open position is lower than electric power needed by the solenoid (10) to remove the obturator member (13) from the closed position, characterized in that stop protrusions (2f) extending radially inwards from a spring seat (2d) cooperate with a flange portion (13b) of the obturator element (13) to define aninnermost end-of-travel position for the obturator element (13), wherein this innermost end- of-travel position defines a minimum distance of the movable core (12) from the permanent magnet (21) such that the magnetic force applied by the permanent magnet (21) is lower than the elastic force applied by the spring (19).

2. Direct acting solenoid valve according to claim 1, wherein the movable core (12) is a piece of ferromagnetic material.

3. Direct acting solenoid valve according to claim 1 or 2, wherein the permanent magnet (21) defines a magnetic circuit together with a shell structure (10b) of the solenoid (10).

4. Direct acting solenoid valve according to claim 3, wherein the helical spring is arranged outside of the magnetic circuit defined by the permanent magnet (21) and shell structure (10b) of the solenoid (10).

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