WO2007098789A1

WO2007098789A1 - A valve unit

Info

Publication number: WO2007098789A1
Application number: PCT/EP2006/005888
Authority: WO
Inventors: Luca Peron; Massimo Giacomelli; Stefano Garbin
Original assignee: Sit La Precisa S.P.A.
Priority date: 2006-02-28
Filing date: 2006-06-20
Publication date: 2007-09-07
Also published as: ITPD20060062A1

Abstract

A valve unit for controlling the supply of a combustible gas comprising at least two valve means (3,5; 4,6) and solenoid means (7) operationally associated with the valve means to control the latter between a first operating condition in which the solenoid means are electrically supplied and a second operating condition in which the solenoid means are not electrically supplied, each valve means being provided with a respective ferromagnetic core (9, 9') associated with the magnetic circuit of the solenoid means (7) in order to control the respective valve means between these operating conditions. The solenoid means (7) comprise a single core (15) whose winding turns (15a) encompass both the ferromagnetic cores (9, 9') for the electromagnetic control of the respective valve means and the ferromagnetic cores (9, 9') are disposed in a mutually spaced relationship with their respective directions of operational displacement mutually spaced from one another.

Description

A valve unit Technical field

The present invention relates to a valve unit for controlling a combustible gas supply having the characteristic features set out in the preamble of the main claim. Technological background

These units are used in particular to control the supply of combustible gas to a burner or like consumer unit in order to vary its supply pressure or the flow of gas supplied in a controlled manner. A typical application is in the system controlling the supply of gas to burners of boilers for domestic heating and/or heating of domestic hot water.

In accordance with current technical regulations, these units normally have to comprise a dual valve device adapted to intercept the gas path in such a way that they are operationally independent and to ensure that the passage of gas is intercepted by one of the valve devices even when the other device is subject to an operating malfunction.

A typical application comprises the arrangement in cascade of a pair of electrovalves comprising respective shutters whose control rod is axially displaced by means of an electromagnet actuator in opposition to a resilient spring adapted to recall the shutter into the position intercepting the corresponding valve seat (for instance when there is no electrical supply to the electromagnet). Typically, this pair of electrovalves has an exclusively on/off function, i.e. it is adapted to ensure the safe opening or closing of the respective valve seats disposed along the supply duct, although more complex versions may be embodied with proportional or stepped operators, i.e. able to assume a plurality of positions as a function of the value of the electrical supply signal supplied to the electrovalve.

In a first known solution, the electromagnetic actuators comprise respective and separate magnetic circuits with separate and distinct electrical coils forming the respective winding turns for the generation of the magnetic field. In order to obviate the need for a double coil, which entails fairly significant space, weight and cost constraints, valve units with dual valve devices having respective electromagnetic actuators actuated by means of a single electrical coil have been proposed in the prior art. One example is disclosed in US Patent Specification 4 921 011. In this solution the single coil encompasses the ferromagnetic core of only one of the actuators and the magnetic circuit is closed externally to the coil on the core of the other actuator. Although this solution enables the use of a solenoid with a single coil for the simultaneous control of both actuators, it nevertheless has some drawbacks. In practice, the magnetic circuit has a high reluctance during the ignition phase of the actuators as a result of the individual reluctances disposed in series in the circuit. If the reluctance is expressed as the ratio between the magnetomotive force applied to the magnetic circuit and the induction flux generated thereby and linked with the circuit, it will be readily appreciated that a request for a higher magnetomotive force requires a greater quantity of turns in the coil, thereby increasing weight, bulk and cost (chiefly as a result of the copper). Moreover, the magnetic circuit of this solution entails, as a result of its geometry, significant dispersions of the magnetic flux linked thereto, leading to a reduction of efficiency or the need to compensate by means of high numbers of ampere turns.

A further known solution, disclosed for instance in European Patent 1 559 936, also proposes a magnetic circuit with a single excitation coil, in which the valve devices together with the electromagnetic actuators are, however, coaxial with one another with a concentric arrangement of the valve seats as well. In this solution, the ferromagnetic cores are therefore guided coaxially to one another with relative magnetic attraction for the displacement of the respective shutters. This geometry nevertheless requires high dimensional precision to ensure the coaxial sliding of the parts moving within the seat or concentrically coupled holes. This consequently requires higher machining tolerances and may also entail problems of operational reliability when it is not possible fully to ensure that the two valve devices are functionally independent. This arrangement is not, moreover, very flexible in terms of the layout of supply ducts, in particular when one of the two valve devices has to have particular features, for instance when it is to be applied to a servo-assisted valve circuit. Disclosure of the invention

The main object of the present invention is therefore to provide a valve unit structurally and operationally designed to remedy the drawbacks discussed above with respect to the known prior art.

These and other objects to be set out in detail in the following description are achieved by the invention by means of a valve unit embodied in accordance with the accompanying claims. Brief description of the drawings Further characteristic features and advantages of the invention are set out in detail in the following description of a preferred embodiment thereof, given solely by way of non-limiting example, made with reference to the accompanying drawings, in which:

Fig. 1 is a view in axial section of a valve unit of the invention; Fig. 2 is a partially exploded perspective view of a detail of the valve unit of Fig. 1;

Fig. 3 is a view corresponding to Fig. 1 showing the direction of flow of the gas through the unit in two separate operating conditions. Preferred embodiment of the invention In these Figures, a first embodiment of a valve unit for controlling the supply of a combustible gas to a burner or like consumer unit in accordance with the present invention is shown overall by 1.

The unit 1 comprises a supply duct 2 for the transfer of gas from a supply member (not shown) to a burner apparatus (not shown) provided with a first and a second valve seat, shown by 3 and 4 respectively, associated with respective shutters 5, 6. The shutters 5 and 6 cooperate with the corresponding seats 3 and 4 in order to carry out the function of opening and closing the gas path (on/off function).

Respective electromagnetic actuators operationally associated with solenoid means shown overall by 7 are provided for the control of the shutters 5, 6.

In further detail, each of the control rods of the shutters 5, 6 is formed as two coaxial sections of ferromagnetic material inserted in a magnetic circuit generated by the solenoid means 7, capable of mutual attraction, in which the lower section, connected to the shutter, is directly urged by resilient recall means into the position closing the valve seat, as will be explained in detail below.

The electromagnetic actuator operationally associated with the shutter 5 will be described in detail; the other actuator associated with the shutter 6 is structurally identical and the same reference numerals followed by the apostrophe sign C) will be used for corresponding components.

The coaxial sections of the control rod of the shutter 5 (6) comprise a first and a second core shown respectively by 8 and 9 (8' and 9') which are structurally independent from one another and coaxial with the shutter, the upper core 8 (8') being made rigid with a stationary structure of the valve unit, and the lower core 9 (9') being coupled to the shutter and guided in a sliding manner in the body of the valve unit and thus capable of relative movement with respect to the fixed core. The cores 8, 9 (8', 9') are capable of mutual magnetic attraction as a result of the excitation of the solenoid means 7 at the location of respective surfaces 8a, 9a (8a', 9a') facing one another and forming an air gap 10 (10').

A spring forming a means resilien y recalling the shutter 5 (6) into the position intercepting the corresponding valve seat is shown by 11 (H'). An abutment member of the spring 11 (H') is shown by 12 (12') and is connected rigidly to the stationary part of the valve unit. Each spring 11, 11' therefore acts between the stationary portion of the valve body and the respective shutter 5, 6 in order to urge this shutter to close the corresponding seat 3, 4 when there is no magnetic attraction between the cores 8, 9 (8' 9') under the action of the resilient force exerted by the spring. According to a main characteristic feature of the invention, the solenoid means 7 comprise a single electrical coil 15 whose winding turns 15a encompass both the ferromagnetic cores 9, 9' for the control of the respective shutters, in accordance with the configuration shown in detail in Fig. 1. The coil 15 is provided with an outer carcass 16 which forms the yoke structure adapted to guide the magnetic flux generated by the magnetomotive force of the coil.

In accordance with the invention, the ferromagnetic cores 9, 9' are also disposed in a spaced relationship with one another with their respective directions of axial displacement mutually spaced from one another. In further detail, these operating directions, shown respectively by X and X' for the respective cores 9, 9', are oriented parallel to one another.

A central median plane of axial symmetry of the coil is shown by Y and the cores 9, 9' are disposed in a symmetrical mirror position with respect to this plane.

The carcass 16 is also advantageously symmetrical with respect to the median plane Y so as to distribute the magnetic flux linked with both moving electromagnetic control cores in a balanced manner.

In Fig. 1, the main direction of flow of the magnetic field generated by the coil is shown by a sequence of continuous arrows. In this respect, the yoke defined by the carcass 16 and by lower plates 18 of the valve unit provides, in the vicinity of the cores 9, 9' a circuit with a substantially C- shaped cross section, the open side of this circuit being closed by each pair of cores 8, 9 (8', 9') of the respective shutter 5, 6. The choice of this arrangement, as well as the provision of a gap 19 between the plates 18, makes it possible efficiently to guide the magnetic flux linked with the cores 9, 9' thus minimising flux dispersions and increasing the overall efficiency of the electromagnetic control.

In operation, the supply of the coil 15 causes the generation of the magnetic flux adapted to enable the simultaneous magnetic attraction of the two cores 9, 9' against the respective fixed cores 8, 8' against the resilient action of the springs 11, 11' with the consequent opening of the valve seats. Vice versa, when the supply of the coil 15 is discontinued, the resilient recall forces of the springs tend to urge the shutters to close against their respective valve seats, providing for the function of safe interception of the gas path through the duct 2.

In order to verify the correct leak-tight operation of each of the valve seats, independently from one another, the duct 2 is provided with a bypass duct 21 and an exhaust opening 20 adapted selectively to bring sections of the duct 2 into communication, as will be described below. The exhaust opening 20 may be intercepted by a screw 20a and is defined by a bushing 20b engaged in a leak-tight manner in a through hole 20c provided in the central section 2a of the duct 2 comprised between the valve seats. The opening 20 causes the central section 2a to communicate with the exterior of the valve unit and opens this section 2a to exhaust. The bypass duct 21 may be selectively intercepted by a screw 21a engaged in a leak-tight manner in a housing 21b of the duct 2 and is adapted to intercept or enable communication between a section upstream and a section downstream of this valve seat. In operation, in order to verify the leak-tightness of the seat 3, the opening 20 is open to exhaust, while the bypass duct 21 remains closed. In this case, it is possible to verify the leak-tightness of the seat 3 in a functionally independent manner from the downstream valve seat 4. The dashed arrows in Fig. 2 show the direction of the gas flow in this operating condition. Vice versa, for verifying the seat 4, the opening 20 is kept closed and the bypass 21 is opened by unscrewing the screw 21a. In this way, the valve seat 3 is bypassed and the gas flows through the valve seat 4. The dot-dash arrows of Fig. 2 show the direction of the gas flow in this second operating condition. The invention achieves the objects set out above and provides the advantages discussed with respect to known solutions.

It will be appreciated in particular that the valve unit of the invention makes it possible advantageously to control a dual valve device by means of a single electrical coil with a saving of up to 30% and more with respect to the copper turns used in known solutions, while providing equivalent efficiency.

A further advantage lies in the fact that the single coil configuration with ferromagnetic control cores of the shutters in a mutual spaced relationship, on the one hand entails no interference or mechanical superimposition between the two valve devices, simplifying their construction and improving their reliability by reducing the risk of operating malfunctions, especially in comparison with known solutions with devices with a coaxial configuration, and, on the other hand, enables more flexibility in the layout of the ducts of the valve unit. A further advantage is that the efficiency which can be achieved with a single coil control of the invention makes it possible to control the two valve devices with full flow regulation, which may overcome the drawbacks of known solutions in which, as a result of lower efficiency (force - actuator stroke), only one of the valves acts on the full flow while the other is inserted in a servo circuit.

Claims

C L A I M S

1. A valve unit for controlling the supply of a combustible gas comprising at least two valve means (3,5; 4,6) and solenoid means (7) operationally associated with the valve means to control the latter between a first operating condition in which the solenoid means are electrically supplied and a second operating condition in which the solenoid means are not electrically supplied, each valve means being provided with a respective ferromagnetic core (9, 9') associated with the magnetic circuit of the solenoid means (7) in order to control the respective valve means between these operating conditions, characterised in that the solenoid means comprise a single core (15) whose winding turns (15a) encompass both the ferromagnetic cores (9, 9') for the electromagnetic control of the respective valve means and in that the ferromagnetic cores are disposed in a mutually spaced relationship with their respective directions of operational displacement mutually spaced from one another.

2. A valve unit according to claim 1, wherein the directions of operational displacement of the electromagnetic control cores (9, 9') are oriented parallel to one another.

3. A valve unit according to claim 1 or 2, wherein each valve means comprises a respective shutter (5, 6) cooperating with a respective valve seat (3, 4) , each electromagnetic control core (9, 9') being disposed coaxially with the corresponding shutter (5, 6). 4. A valve unit according to one of the preceding claims, wherein the electromagnetic control cores (9, 9') are disposed symmetrically with respect to a central median plane of symmetry of the coil (15).

5. A valve unit according to claim 4, wherein the solenoid means comprise a carcass (16) in the form of a yoke having a first and a

5 second yoke portion associated respectively with the electromagnetic control cores (9, 9'), these members being disposed symmetrically with respect to the median plane of symmetry of the coil (15).

6. A valve unit according to claim 5, wherein each of the yoke portions is shaped with a C-shaped cross section, the electromagnetic control o core (9, 9') being disposed between the opposite sides of this section as an axial prolongation of a ferromagnetic portion (8, 8') made rigid with the corresponding yoke, an air gap (10, 10') being defined between this core and this portion at the location of which the mutual magnetic attraction between the core and the portion takes place. s 7. A valve unit according to claim 5, wherein the carcass (16) is centrally discontinuous at the location of the median plane of symmetry of the coil (15) in order to guide the magnetic flux along the respective yoke associated with the corresponding electromagnetic control core. o 8. A valve unit according to one or more of the preceding claims, comprising, in the supply duct (2), at least one exhaust opening (20) and at least one bypass duct (21) adapted selectively to bring duct sections into reciprocal communication or to open to this duct to exhaust so as to make the functions of sealing of the valve seats (3, 5 4) functionally independent from one another.

9. A valve unit according to claim 8, wherein the exhaust opening (20) is provided in the duct section comprised between the valve seats (3, 4) in order selectively to open this section to exhaust, the bypass duct (21) being provided in order selectively to bring into communication a section upstream and a section downstream with respect to the valve seat (3) disposed upstream of this exhaust opening (20), this bypass duct (21) enabling a bypass of the corresponding valve seat (3) between the sections upstream and downstream thereof.