GB2296075A

GB2296075A - Solenoid actuated pilot valve

Info

Publication number: GB2296075A
Application number: GB9524187A
Authority: GB
Inventors: Fulvio Benna; Piero Quarello
Original assignee: Elbi International SpA
Current assignee: Elbi International SpA
Priority date: 1994-12-12
Filing date: 1995-11-27
Publication date: 1996-06-19
Anticipated expiration: 2015-11-27
Also published as: GB9524187D0; GB2296075B

Abstract

The valve unit (18) comprises a first cup-shaped element (20) made of plastics material with a base that has an external axial shank (21) in which a longitudinal duct (21a) is formed between the seat of the pilot valve and a distal vent opening (24). A second annular element (40) of plastics material is anchored around the shank of the first element and is secured thereto by ultrasonic welding. <IMAGE>

Description

A SUPPORT AND GUIDE UNIT FOR AN OBTURATOR OF A SOLENOID VALVE AND A METHOD FOR THE MANUFACTURE THEREOF DESCRIPTION The present invention relates to a support and guide unit for a diaphragm obturator of a solenoid valve having an electrically-operated pilot valve.

More specifically, the subject of the invention is a support and guide unit comprising: a first, cup-shaped element of plastics material the base of which has an external axial shank in which a longitudinal duct extends between a valve seat for the pilot valve formed on the base wall of the first element and a vent opening located at the distal end of the shank, and a second, annular element also of plastics material, anchored around the shank and defining, with the base of the first element, an annular seat for restraining the diaphragm obturator.

The support and guide unit according to the invention is characterized in that the second element is anchored to the shank of the first element with interference coupling by ultrasound welding.

A further subject of the invention is a method of manufacturing a support and guide unit of the aforesaid type, the main characteristics of the method being defined in appended Claims 4 et seq.

Further characteristics and advantages of the invention will become clear from the following detailed description given purely by way of non-limiting example with reference to the appended drawings, in which: Figure 1 is a sectioned view of a solenoid valve with an electrically-operated pilot valve including a support and guide unit for a diaphragm obturator according to the invention, Figure 2 is a sectioned view of the support and guide unit included in the solenoid valve shown in Figure 1, on an enlarged scale, Figure 3 shows the detail indicated III in Figure 2, on an enlarged scale, and Figure 4 is a view similar to that of Figure 3 showing two elements of the support and guide unit according to the invention before their mutual coupling.

In Figure 1, a solenoid valve of the type currently used, for example, for controlling the admission of water from the water mains to a washing machine (a laundry-washing machine or a dishwasher) is generally indicated 1.

The solenoid valve 1 comprises a body 2 in which an inlet connector 3 and an outlet connector 4 are formed.

A filter 5 and a flow regulator 6, both of known type, are disposed in the inlet connector 3.

A substantially annular inlet chamber 7 is formed in the body 2 between the inlet connector 3 and the outlet connector 4 around a tubular projection 8 of the body which forms a valve seat 9. An outlet duct 10 in the tubular projection 8 communicates with the outlet connector 4.

An annular obturator, generally indicated 11, is associated with the valve seat 9. The obturator comprises an annular element 12 which acts as the valve element proper in cooperation with the seat 9. The annular element 12 is connected to another annular element 13 by a diaphragm 14. The annular element 13 is clamped between the body 2 and an end flange 15 of a tubular casing 16 outside which an excitation coil 17 is disposed.

The obturator proper 12 is engaged in a corresponding seat in a support and guide unit, generally indicated 18.

In the embodiment according to Figures 2 to 4, the support and guide unit 18 comprises a first element 19 of moulded plastics material with an upper, cup-shaped portion 20 and a lower tubular shank 21 integral therewith. The shank 21 extends from the lower wall of the cup-shaped portion 20 and an axially intermediate region thereof forms a radial shoulder 22.

The shank 21 defines an axial duct 21a which opens at the top in a valve seat 23 formed in the base of the cupshaped portion 20. At the bottom, the duct 21a terminates in a vent opening 24 communicating with the outlet duct 10 of the solenoid valve (Figure 1).

With reference to Figure 1, a core 25 mounted for moving axially in the tubular casing 16 bears an obturator 26 at its lower end. A helical spring 27 is disposed between the other end of the core 25 and the end wall of the casing 16. When the coil 17 is in the de-energized condition, the spring 27 pushes on the core 25 so that the obturator 26 presses on the valve seat 23 (Figure 1).

As can be seen in Figure 1, the diaphragm 1 4 separates the chamber 7 from an overlying control chamber 28 defined between the flange 15 of the casing 16, the diaphragm 14 and the support and guide unit 18.

As can best be seen in Figure 2, the diaphragm 14 bears partially against the side surface of the cup-shaped portion 20 of the element 19 of the support and guide unit. At least one groove, indicated 29 in Figure 2, is formed in the side of the cup-shaped portion 20 and its lower end is connected to an annular recess 30 formed in the lower face of the base of the cup-shaped portion 20.

The recess 30 faces a duct 31 in the obturator 12 (Figure 2).

The chamber 7 of the solenoid valve is permanently in communication, through the duct 31 and the grooves 29 and 30, with the overlying control chamber 28 in which the valve formed by the obturator 26 and by the seat 23 is located. This valve (the pilot valve) can be controlled by the excitation of the solenoid 17 and is normally closed.

In operation, the hydraulic fluid supplied to the inlet connector 3 of the solenoid valve reaches the control chamber 28, in known manner, through the duct 31 and the grooves 30 and 29 described above. The hydraulic pressure in the chamber 28 exerts a greater force on the support and guide unit 18 and on the diaphragm 14 than that exerted thereon by the hydraulic pressure in the chamber 7. In the de-energized condition of the solenoid 17, the principal valve formed by the obturator 12 and by the valve seat 9 consequently remains closed.

As soon as the solenoid 17 is excited, the core 25 is attracted upwards against the action of the spring 27; the obturator 26 opens the valve seat 23 and the hydraulic pressure in the control chamber 28 is discharged almost instantaneously through the duct 21a in the shank 21 and the outlet duct 10. The force exerted on the obturator 12, the diaphragm 14 and the support and guide unit 18 by the pressure in the chamber 7 consequently lifts this assembly and moves the obturator 12 away from the valve seat 9. The principal valve is thus opened and the hydraulic fluid can flow from the inlet connector 3 to the outlet connector 4.

As can best be seen in Figures 2 to 4, the support and guide unit 18 also comprises an annular element 40 coupled with the shank 21 of the cup-shaped element 20.

This annular element projects radially relative to the portion of the cup-shaped element 20 which forms the annular shoulder 22. The annular element 40 together with the base of the cup-shaped element 20, defines an annular seat 41 in which the obturator 12 is clamped (Figure 3).

Figure 4 shows the shape of the ring 40 and of the shank 21 of the cup-shaped element 20 before they are coupled.

As can be seen in this drawing, the ring 40 has an internal surface with a stepped profile with a series of cylindrical, annular surfaces 51, 52, 53 connected by radial shoulders 54 and 55. The cylindrical surfaces 51, 52 and 53 have progressively increasing diameters.

The external lateral surface of the tubular shank 21 correspondingly has a similar stepped profile with cylindrical surfaces 61, 62 and 63 connected by radial shoulders 64 and 65. The diameters of the cylindrical surfaces 61 to 63 increase progressively.

The diameters of the successive inner annular surfaces 51, 52 and 53 of the ring 40 are slightly smaller than the diameters of the cylindrical surfaces 61, 62 and 63 of the tubular shank 21. The axial dimensions of the cylindrical surfaces and the radial dimensions of the shoulders of the ring 40 correspond essentially to the axial dimensions of the cylindrical surfaces and to the radial dimensions of the shoulders of the tubular shank 21.

During assembly, the ring 40 is coupled with the end of the tubular shank 21 with interference, with the aid of a sonotrode which brings about ultrasound welding thereof.

An annular groove indicated 50 in Figures 3 and 4 is advantageously formed adjacent the outer cylindrical surface 63 in the shoulder 22 of the cup-shaped element 20. This groove is intended to collect the "flash" which originates from the fusing together of the steps of the ring 40 and the corresponding steps of the shank 21 interfering therewith during the interference coupling by ultrasound welding.

Upon completion of the coupling, the ring 40 and the cupshaped element 20 have the configuration shown in Figure 2 and, on an enlarged scale, in Figure 3.

The annular element 40 is preferably, but not necessarily, tapered away from the cup-shaped element with a frustoconical outer annular surface 40a.

When the solenoid valve 1 is in operation, the ring 40 acts as a guide element for the displacement of the obturator 12. In fact, the ring 40 extends and is guided for sliding axially in the tubular projection 8 of the body 2 of the solenoid valve in which the valve seat 9 is formed.

Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present invention.

Claims

1. A support and guide unit for a diaphragm obturator (12, 14) of a solenoid valve (1) having an electricallyoperated pilot valve (23-26, 17), comprising a first, cup-shaped element (20) of plastics material the base of which has an external axial shank (21) in which a longitudinal duct (21a) extends between a valve seat (23) for the pilot valve (23-26; 17) and a vent opening (24) located at the distal end of the shank (21), and a second, annular element (40) also of plastics material, anchored around the shank (21) and defining, with the base of the first element (20), an annular seat (41) for restraining the obturator (12, 14), characterized in that the second element (40) is anchored to the shank (21) of the first element (20) with interference coupling by ultrasound welding.

2. A support and guide unit according to Claim 1, characterized in that the external lateral surface of the shank (21) of the first element (20) and the internal surface of the second element (40) are formed with respective stepped profiles (51-55; 61-65) which can interfere with one another upon coupling and fuse together as a result of the ultrasound welding.

3. A support and guide unit according to Claim 1 or Claim 2, characterized in that the second element (40) has an external surface (40a) which is tapered away from the first element (20).

4. A method of manufacturing a support and guide unit (18) for a diaphragm obturator (12, 14) of a solenoid valve (1) having an electrically-operated pilot valve (23-26, 17), comprising the steps of: providing a first, cup-shaped element (20) of plastics material, the base of which has an external axial shank (21) in which a longitudinal duct (21a) extends between a valve seat (23) for the pilot valve (23-26; 17) and a vent opening (24) located at the distal end of the shank (21), providing a second, annular element (40) also of plastics material, anchoring the second element (40) around the shank (21) of the first element (20) in a manner such that an annular seat (41) for restraining the obturator (12, 14) is defined between the second element (40) and the base wall of the first element; characterized in that the second element (40) is anchored to the shank (21) of the first element (20) by interference coupling and ultrasound welding.

5. A method according to Claim 4, characterized in that the external lateral surface of the shank (21) of the first element (20) and the internal surface of the second element (40) are formed with respective stepped profiles (51-55; 61-65) which can interfere with one another upon coupling and can fuse together as a result of the ultrasound welding.

6. A support and guide unit for a diaphragm obturator of a solenoid valve having an electrically operated pilot valve substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

7. A method of manufacturing a support and guide unit for a diaphragm obturator of a solenoid valve having an electrically operated pilot valve substantially as hereinbefore described.