WO2004099669A1

WO2004099669A1 - Device for controlling the supply of a combustible gas, particularly for cooktops and similar equipment

Info

Publication number: WO2004099669A1
Application number: PCT/IT2003/000280
Authority: WO
Inventors: Massimo Giacomelli; Alessandro Chiorlin; Stefano Zanella
Original assignee: Sit La Precisa S.P.A.
Priority date: 2003-05-09
Filing date: 2003-05-09
Publication date: 2004-11-18
Also published as: AU2003233188A1; EP1623157A1

Abstract

A device for controlling the supply of a combustible gas comprises a valve unit (2) provided in a supply duct (4) and including a first valve seat (5) in the duct, a first plug (6) associated with the seat, a motorized actuator means (7) acting on the first plug (6) for causing the latter to open and/or close the valve seat (5), an electromagnet unit (15) associated for operation with the actuator (7) to impel the first plug (6) to close the first valve seat (5) independently of the operating position of the actuator (7),and a second valve seat (18) in the supply duct (4) positioned coaxially with and in series with the first valve seat (5) with respect to the direction of the gas flow. A second plug (19) associated with the second seat (18) is designed to regulate the flow rate of gas supplied through the second valve seat (18).

Description

Device for controlling the supply of a combustible gas, particularly for cooktops and similar equipment Technical field

The present invention relates to a device for controlling the supply of a combustible gas according to the precharacterizing clause of the principal claim (Claim 1). Prior art

The invention relates particularly, but not exclusively, to the technical field of the control of the supply of combustible gas to burners provided on cooktops, gas ovens and similar equipment.

In this field there is a known method of providing the aforesaid equipment with control devices including valve units designed to supply gas generally at two levels, in other words at a predetermined minimum or maximum gas flow rate. In these known devices, provision is made to shut off the valve unit for safety purposes, in the absence of a flame at the burner, by means of a thermomagnetic flame detection device, of the thermocouple type for example.

In this technical field, it has been found necessary to provide a wider range of functions in the gas supply control devices, for example by enabling the user to control and regulate the supply of gas over the range between the minimum and maximum flow rates, thus making it possible to regulate the intensity of the flame on the cooktop as desired. Description of the invention

A principal object of the invention is to provide a gas supply control device which is structurally and functionally designed to give the equipment a wider range of functions, relating for example to the provision of a control for regulating the flow rate of gas supplied to the burner, but which is also integrated with a system for monitoring the flame and for shutting off the gas supply path for safety purposes, of the thermomagnetic type or any other type which is reliable and conforms to the technical standards governing the field.

Another object is to provide a gas supply control device in which there is implemented, in addition to the flame regulation function, another function by which the flame on the cooktop is turned on and off in a delayed way, at the predetermined level of regulation, according to specified programming procedures.

These and other objects which will are described more fully below are achieved by the invention by means of a gas supply control device made in accordance with the attached claims. Brief description of the drawings

The characteristics and advantages of the invention will be made clearer by the following detailed description of a preferred example of embodiment thereof, illustrated, for the purposes of guidance and without restrictive intent, with reference to the attached drawings, in which

Figure 1 is a functional block diagram of the device according to the invention,

Figure 2 is a view in axial section of the gas supply control valve unit provided in the device according to the invention, and

Figure 3 is a front elevation of a further detail of the device according to the invention. Preferred embodiment of the invention

With reference initially to Figure 1, the number 1 indicates the whole of a device including a valve unit 2 (delimited schematically by the frame drawn in broken lines) for controlling the supply of combustible gas to one or more burners 3 of a cooktop (not shown), made according to the present invention.

The gas is supplied through the valve unit 2 by means of a gas supply duct 4, between a supply aperture 4a and a delivery aperture 4b.

The valve unit 2 comprises, in the supply duct 4, a first valve seat 5 with a corresponding first disc-type plug 6 associated with it, together with a motorized actuator, indicated as a whole by 7. The said actuator comprises an operating stem 8 of the plug 6 with a longitudinal axis X.

The operating stem 8 comprises a first and a second section 9 and 10, which are coaxial with each other, are structurally independent and extend in the form of continuations of each other, and are also connected to each other by a male and female screw coupling.

More particularly, the second section 10 of the stem carries from one of its axial ends, an externally threaded shell which is screwed into a female thread formed in a blind hole of the first section 9. The latter section has a first portion 9a (incorporating the female thread) with an external shell having a polygonal profile which is engaged in an axially slidable way in a through hole 11 of a corresponding profile formed centrally in a rotor 12 of an electric motor 13 with a hollow shaft. Thus the first portion 9a is fixed as regards rotation to the rotor and is axially slidable with respect to it, as a result of the male and female screw coupling.

The motor 13 is preferably of the reversible stepping type.

The first section 9 of the stem comprises a second portion 9b, which extends axially to form a continuation of the first portion and is connected to the latter in an oscillating way, and on which the first plug 6 is fitted. A spring 14 for taking up the axial play in the movement of the stem along the axis X is provided in the articulated connection between the portions 9a and 9b.

The valve unit 2 is also provided with an electromagnet unit, indicated as a whole by 15, comprising an electromagnet 16 with a first part or fixed core 16a carrying a magnetizing winding and a second moving armature part 16b which can be attached by magnetization to the fixed core. The moving armature part of the electromagnet 16b is connected to the end of the second section 10 of the stem, opposite the threaded portion.

The number 17 indicates a first spring acting between the stationary structure of the valve unit and the first plug 6 so that the latter tends to close the valve seat 5, in opposition to the plug raising action imparted by the motorized actuator 7.

The valve unit 2 also comprises a second valve seat 18 formed in the duct 4, positioned coaxially with the first seat 5 and downstream of it with respect to the direction of the flow of gas. The second valve seat 18 is associated with a second plug 19 coupled to the first plug 6, as described more fully below.

The second plug 19 is structurally independent of the first plug 6 and has a corresponding stem 20 carrying at one end a widened portion 21 which is axially retained by a pair of appendages 22 of the stem 8, as shown schematically in Figure 2.

The said plugs 6 and 19 are therefore connected to each other with a limited degree of relative axial sliding, with a spring 23 acting between them. Guide means are provided on the stem 20 for guiding the second plug 19 coaxially with the first plug in its relative sliding with respect to the latter.

The second plug 19 also has a truncated conical needle 24 which passes through the valve seat 18 and which can vary the gas supply cross section according to the axial sliding of the second plug 19 in the opening and closing operations, in order to regulate the flow rate through the said plug.

The number 25 indicates a minimum duct, which has a calibrated throttle with a screw for regulating the minimum flow rate. The duct 25 forms a by-pass of a section of the duct 4, upstream from the valve seats 5 and 18, having a passage cross section 26 which can be shut off by the first plug 6, as described more fully below.

The device 1 comprises, according to the invention, an electronic circuit assembly, shown schematically in Figure 1 and identified by the numerical reference 27, which is electrically connected at one end to a thermocouple sensor 28 for detecting the flame at the burner 3 and at the other end to the electromagnet unit 15 and to the motor 13 for controlling the rotation of the motor.

The circuit assembly 27 has comparison means (not shown) for comparing the signal received from the thermocouple with a reference value and for consequently operating the electromagnet unit 15 to move the plugs 6 and 19 so that they close the corresponding valve seats, if no flame is detected at the burner 3. Conveniently, if there is no flame at the burner, the circuit assembly is designed to cut of the electricity supply to the electromagnet 16 so that both plugs 6 and 19 are moved to close the corresponding valve seats by the elastic action of the springs 17 and 23.

The circuit assembly 27 also has means for regulating the angular rotation of the stepping motor 13 according to a predetermined number of levels, each level being correlated with a corresponding supply flow rate (which is therefore matched to a corresponding upward travel of the second plug 19), so that the gas flow rate (and consequently the flame intensity) is regulated over the aforesaid range of levels.

Means of setting the predetermined level are provided in the circuit assembly, with suitable push button means 29 to enable the user to select the desired level setting.

Timing means are also provided, using an incorporated timer element, for programming the ignition and/or extinguishing of the flame at the burner 3, at the predetermined flame intensity level. A digital clock 30 with programming keys is provided for this purpose.

The circuit assembly 27 is combined with a display unit 31 (one for each of the burners 3 provided) which displays the set flame level and which comprises one or more indicators 32.

Preferably, these indicators 32 are shaped in the form of a sector of a circle and are adjacent to each other, as shown in Figure 3, and their number is equal to the number of flow rate levels that can be set. Thus these indicators, of the backlit type for example, are made to represent to the user the predetermined level between the maximum and minimum levels (arranged in the anti-clockwise direction, for example). Alternatively, all the indicators from the minimum level to the predetermined level can be backlit, to indicate the setting that has been input.

In operation, in an initial condition in which the gas duct 4 is shut off, the valve seats 5 and 18 are closed by the corresponding plugs 6 and 19, as a result of the elastic action of the springs 17 and 23. The electromagnet 16 is de- energized and no current is supplied to the motor 13. Starting from this condition, the motor 13 is initially operated for a predetermined number of angular steps, the total extent of which is correlated, by means of the thread pitch of the male and female screw coupling, with a predetermined axial travel of the second section of the stem. The travel of this section of the stem is such that the moving armature 16b is brought up to the fixed core 16a of the electromagnet, in the proximity of the area of electromagnetic attraction. The subsequent energizing of the electromagnet generates an electromagnetic attractive force which can keep the armature 16b attached to the fixed core in the position shown in Figure 2.

A subsequent rotation of the motor 13, in the opposite direction to the preceding rotation, causes the first section to be screwed on to the second section of the stem, causing a relative axial sliding of the first section and the consequent movement of the first plug 6 away from the seat 5, in opposition to the action of the spring 17, with the corresponding opening of the seat 5. It should be noted that the second plug continues to close the second seat until the first plug has been raised through a distance equal to the axial relative sliding play between the plugs. When this travel has been completed, the further rotation of the motor causes both the plugs to be raised together so that the corresponding valve seats are opened.

It should be observed that this initial opening causes the supply to be provided at the maximum flow rate, since the needle 24 is in such a position as to form a maximum cross section of passage of the gas through the second valve seat.

According to the number of steps of rotation completed by the motor 13 (each corresponding to one level of supply flow rate) and selected with the setting means, the supply flow rate is regulated at the desired level with consequent regulation of the flame intensity. This regulation makes it possible to move from maximum flow rate to minimum flow rate, through a predetermined number of intermediate values (levels).

In conditions of minimum flow rate, the first plug 6 is moved so that it closes the passage cross section 26 and the gas flows in the minimum duct 25, thus providing the minimum flow rate according to the preset calibration.

Conversely, in normal operating conditions, the gas duct 4 is shut off by causing the motor 13 to rotate in the opposite direction until both plugs are made to close the corresponding valve seats.

Conversely, if predetermined conditions occur which require the closing of the valve seats, for example if the flame at the burner 3 is accidentally extinguished, the thermocouple signal is converted by the circuit assembly into a signal for cutting off the electricity supply to the electromagnet unit, so that the plugs 6 and 19 close the seats 5 and 18 as a result of the elastic action of the springs 17 and 23. This action is always guaranteed, regardless of the position of the motorized actuator.

Accordingly, the spring 17 is designed with a size and elastic constant such that the safe closing of the valve seats by their respective plugs is guaranteed, regardless of the axial position which the operating stem has reached.

It should be noted that, in these conditions, the spring 23 acting between the plugs has characteristics which ensure that an elastic closing force is applied to the second plug 19, independently of the first plug 6. Alternatively, in conditions of closing for safety purposes, in conjunction with the cutting off of the electricity supply to the electromagnet 15, the motor 13 may be caused to rotate in such a way that, together with the elastic action of the springs, it helps to move the plugs towards the corresponding valve seats, until the seats are closed if necessary, in such a way that a double action is provided to achieve the condition in which the gas duct is shut off.

In operation, the ignition, regulation and extinguishing of the flame are caused, by the programming means, to take place with a time delay or according to sequences programmed by means of the desired settings.

Thus the invention achieves the proposed objects while having numerous advantages over the known solution.

A principal advantage consists in the fact that the device according to the invention provides a wider range of functions, in terms of regulation and programming of the flame intensity, while providing a safety shut-off system based on reliable thermomagnetic means and conforming to the relevant standards.

Claims

1. Device for controlling the supply of a combustible gas, comprising a valve unit (2) provided in a supply duct (4), the said valve unit (2) including: a first valve seat (5) in the duct and a first plug (6) associated with the said seat, a motorized actuator means (7) acting on the said first plug (6) to cause it to open and/or close the valve seat (5), an electromagnet unit (15) associated for operation with the actuator (7) to impel the first plug (6) towards a position in which the first valve seat (5) is closed, independently of the operating position of the actuator (7), a second valve seat (18) in the supply duct (4), positioned coaxially with and in series with the first valve seat (5) with respect to the direction of the gas flow, a second plug (19) associated with the second seat (18) and designed to regulate the flow rate of gas supplied through the said second valve seat (18), the said first and second plugs (6, 19) being connected to each other so that they are both operated by the said actuator means (7) to open and/or close the corresponding valve seats (5, 18) and in response to the command for regulation of the gas flow rate, and are additionally impelled to a position in which the corresponding valve seats are closed by the said electromagnet unit (15) independently of the operating position of the actuator means (7) on the occurrence of a predetermined condition which requires the shutting off of the flow of gas through the supply duct.

2. Device according to Claim 1, in which the said first and second plugs (6, 19) are connected to each other and can slide axially with respect to each other to a limited extent only.

3. Device according to Claim 1 or 2, comprising a first spring (17) for elastically returning the first plug (6) to a position in which the first valve seat (5) is closed and a corresponding second spring (23) acting between the first and the second plugs (6, 19).

4. Device according to one or more of the preceding claims, in which the said actuator means (7) comprises an operating stem (8) with a first and a second section (9, 10) of stem which extend axially to form continuations of each other and which are connected together by a male and female screw coupling, the said first and second sections (9, 10) of stem being connected at their corresponding free ends to the first plug (6) and to a moving armature (16b) of the electromagnet unit (15).

5. Device according to Claim 4, in which the said first section (9) of stem comprises a first part (9a) which is fixed with respect to rotation to a hollow shaft of a rotor (12) of an electric motor (13) and which is free to slide axially with respect to the shaft.

6. Device according to Claim 4 or 5, in which the said first section (9) of stem comprises a second part (9b), forming a continuation of the first part (9a), having an axial end connected in an articulated way to the first part and carrying the second plug (19), guide means being provided to axially guide the said parts in the movement of the said plugs as a result of a rotation of the rotor (12) about its axis of rotation.

7. Device according to one or more of the preceding claims, comprising flame sensor means (28) designed to be associated with a burner (3) to which the gas is supplied through the said valve unit (2) and an electronic circuit assembly (27) connected to the said sensor means (28) and to the electromagnet unit (15) to cause the said plugs (6, 19) to close the corresponding valve seats (5, 18) according to a signal generated by the sensor and indicating the absence of a flame at the burner.

8. Device according to Claim 7, in which the motor (13) operating the actuator (7) is of the stepping type and the said circuit assembly (27) comprises means for controlling the angular rotation of the said motor according to a predetermined number of levels, each level being correlated with a corresponding flow rate of gas supplied through the second valve seat, in such a way that the supply of gas is regulated according to the said levels.

9. Device according to Claim 8, in which means of setting the predetermined level of the flow rate of the gas supplied are provided in the circuit assembly (27).

10. Device according to Claim 9, in which programming means are provided in the circuit assembly for timing the ignition and/or extinguishing of the flame at the burner (3) at the predetermined level of flow rate of the gas supply.

11. Device according to one or more of Claims 7 to 10, in which the said circuit assembly (17) comprises means (31) of displaying the values and times set by means of the circuit assembly.

12. Device according to Claim 11, in which the said display means comprise means (32) for indicating the levels of flow rate of the gas supply.

13. Device according to Claim 12, in which the said indicator means (32) are shaped in the form of sectors of circles, adjacent to each other, for displaying the levels of flow rate of the gas supply.

14. Device according to Claim 13, in which the said indicator means (32) are of the backlit type.

15. Cooktop comprising a plurality of burner positions, each associated with a corresponding burner (3), each burner being supplied with gas through a valve unit (2) controlled by a device according to one or more of Claims 1 to 14.

16. Cooktop according to Claim 15, comprising a circuit assembly (27) according to one or more of Claims 7 to 14, incorporating the functions of control and display of the levels of flow rate of the gas supply for each of the said burner positions.