"Electrovalve"

The present invention has as its subject a solenoid valve which has an application in apparatuses where there is a need to regulate a flow of water or water vapour. In particular the present invention has an application in steam boilers used in domestic electrical appliances such as, for example, machines for the production of coffee or ironing systems . Solenoid valves of known type comprise a main body made, for example, out of brass, into which flows an inlet union connectable to a boiler of a domestic electrical appliance. Inside the above- mentioned inlet union is formed a duct through which a fluid is made to flow into the inside of the solenoid valve. Similarly, the main body is connected to an outlet union inside which is formed a duct for the outflow of the fluid. Inside the main body is arranged a plunger which, when actuated by a control device, regulates the transit of fluid from the inlet duct to the outlet duct. This control device comprises a cylindrical slider (or nucleus) connected coaxially and rigidly to the plunger, and an electromagnetic coil. In

detail, the plunger is dragged by the slider in such a way as to open or close the passage between the inlet and outlet ducts.

Solenoid valves of known type are normally closed and are opened when a user requires fluid. However, there exist solenoid valves which operate according to an opposite principle. In this case, the solenoid valves are normally open and are closed as required. Around the stem is located an electromagnetic coil for moving the slider. In detail, when the solenoid valve is to be opened, the coil is supplied and generates an electromagnetic field which acts on the slider. Since the slider is made of ferromagnetic material, the slider is lifted and drags the plunger which liberates the passage between the inlet duct and the outlet duct. When the flow is to be closed, the supply to the coil is suspended and a return spring lowers the slider. The plunger therefore returns to prevent the passage of fluid.

Solenoid valves of known type however have a number of disadvantages.

First of all, the slider is subject to a pressure difference which is opposed to the electromagnetic force necessary for its lifting. In fact, inside the hollow cylindrical body in which the slider runs is the fluid under pressure, while the end in which the housing for the plunger is formed is subject to the outlet pressure which is less than the inlet pressure. In this way, in addition to the energy expended in lifting the slider and the plunger, it is necessary also to supply the energy for opposing the force generated by the above-mentioned pressure difference . Furthermore, generating an additional force for cancelling out the force on the slider produced by the pressure difference causes a delay in the response of the solenoid valve.

An object of the present invention is therefore to provide a solenoid valve which resolves the above- mentioned disadvantages.

In particular, it is an object of the present invention to provide a solenoid valve in which the above-mentioned pressure difference is reduced or

eliminated, consequently requiring a lesser quantity of electricity for activating it. Furthermore, it is an object of the present invention to propose a solenoid valve with a limited delay in response.

Further characteristics and advantages will appear more clearly from the detailed description of a preferred, but not exclusive, embodiment of a solenoid valve according to the present invention. This description will be set forth below with reference to the attached drawings, provided solely for indicative and therefore not limiting purposes, in which: figure 1 shows an exploded perspective view of a solenoid valve according to the present invention; figures 2, 3 and 4 each represent a sectional view of the solenoid valve shown in figure 1, in three distinct operating conditions. In accordance with the above-mentioned figures, No. 1 indicates a solenoid valve in accordance with the present invention.

Solenoid valve 1 includes a hollow body 2 into which flows an inlet duct 3 to allow the inflow of

a fluid such as, for example, water or water vapour. In more detail. Solenoid valve 1 includes an inlet union 4 which forms at least in part the inlet duct 3. Similarly, from hollow body 2 flows an outlet duct 5 through which the above-mentioned fluid exits. In detail, solenoid valve 1 includes an outlet union 6 which forms at least in part the outlet duct 5. Inside hollow body 2, inlet duct 3 at least partially overlaps outlet duct 5. Inlet duct 3 is in communication with outlet duct 5 through a communicating orifice 7.

Solenoid valve 1 includes a plunger 8 located inside hollow body 2 and movable between a closed position in which it prevents the transit of the fluid from inlet duct 3 to outlet duct 5, and an open position, in which it allows the transit of the fluid from inlet duct 3 to outlet duct 5. In more detail, in the closed position plunger 8 obstructs orifice 7, while in the open position plunger 8 keeps this orifice 7 free and the fluid can pass freely.

Solenoid valve 1 also includes a slider (or nucleus) 9 for activating the plunger 8, slidably

movable inside a closing stem 10. This stem 10 consists of a hollow cylindrical body which is screwed onto hollow body 2 for closing solenoid valve 1. Between stem 10 and hollow body 2 is a gasket 11 which ensures the closure seal. Advantageously, stem 10 can be made of plastic material .

Solenoid valve 1 furthermore includes means 12 for compensating the pressure. In fact, between slider 9 and stem 10 there is fluid at the pressure of the inlet fluid. However, the pressure in the outlet duct 5 is acting over a base surface 9a of slider 9 facing plunger 8. In this way, a pressure difference acts on slider 9 which generates a force opposing the lifting of slider 9 and therefore opposing the opening of solenoid valve 1.

The compensating means 12 acting on slider 9 thus produce a cancelling-out of this force. In more detail, compensation means 12 include a cage 13 which coaxially connects slider 9 to plunger 8.

Cage 13 consists of a tubular body and has a first end 13a connected to slider 9 and a second end 13b connected to plunger 8.

Slider 9 has a groove 14 which extends circumferentially over a lateral surface 9b.

Cage 13 has edges bent inwards in proximity to its first end 13a which engage in groove 14 in such a way that the above-mentioned base surface 9a of slider 9 is enveloped by cage 13. In this way, cage 13 can slide with respect to slider 9 coaxially with the latter.

Cage 13 also has bent edges in proximity to its second end 13b which rigidly clasp plunger 8. Slider 9 can therefore move closer to and further from plunger 8.

Plunger 8 with cage 13 and slider 9 can assume different configurations during the use of solenoid valve 1. In the closed configuration (figure 2) of solenoid valve 1, plunger 8 is in its closed position and therefore prevents the outflow of fluid, while slider 9 is in contact with plunger 8.

In the open configuration (figure 4) of solenoid valve 1, plunger 8 is in its open position and slider 9 is distanced from plunger 8.

When the command to open the solenoid valve is given, during the transition between the closed configuration and the open configuration, slider 9 and plunger 8 assume an intermediate configuration

(figure 3). In this further configuration, plunger

8 is in its closed position, while slider 9 is distanced from plunger 8.

In the intermediate configuration, compensation means 12 are activated on slider 9 and include a compensation chamber 15 formed by plunger 8, base surface 9a of slider 9 and cage 13 itself. Compensation chamber 15 is in fluid communication with inlet duct 3 by bypassing through openings 16 formed in proximity to ends 13a, 13b of cage 13. In this way, before plunger 8 is lifted, leaving orifice 7 free, compensation chamber 15 is filled with fluid at the pressure in the inlet duct 3. At this point, the whole of slider 9 is subject to the same pressure, and the pressure difference mentioned above is cancelled out.

Solenoid valve 1 also includes an electromagnetic coil 17 located around stem 10 which acts on slider

9 to set it in motion. In more detail, when the command to open the solenoid valve 1 is given, coil 17 is supplied and generates an electromagnetic field. This field originates a force on slider 9, which is lifted.

When solenoid valve 1 is to be closed, the supply to the coil 17 is suspended, and slider 9 is thrust downwards by a return spring 18 inserted into stem

10 and acting on a base surface 9c of slider 9 opposite to base surface 9a which faces plunger 8. Advantageously, cage 13 can be made of a plastic material. By way of example, cage 13 can be made of polyetheretherketone (PEEK), or of liquid crystal polymer material.

The invention achieves the proposed objects and obtains important advantages. First of all, once the opening command is given, compensation chamber 15 is formed, into which flows fluid at the pressure of inlet duct 3. The above- mentioned pressure ^' difference is thus cancelled out, and consequently the force opposed to the opening of solenoid valve 1 is also cancelled out.

In consequence, the energy required for moving slider 9, and therefore for opening solenoid valve 1, is reduced.

Furthermore, since it is no longer necessary to provide energy also for opposing the force deriving from the pressure difference, the opening of solenoid valve 1 ends up being faster and the delay in response of solenoid valve 1 is consequently reduced. One advantage attributable to solenoid valve 1 according to the present invention relates to the fact that some of its components, like cage 13 and stem 10, can be made in plastic material. This characteristic allows the overall weight of the solenoid valve 1 to be reduced, and it also entails a simplification of the production process for these components.