EP2771620B1

EP2771620B1 - Gas burner for a cooking hob, with a container detecting system

Info

Publication number: EP2771620B1
Application number: EP12798845.9A
Authority: EP
Inventors: Jean-Marc Brun
Original assignee: Thirode Grandes Cuisines Poligny SAS
Current assignee: Thirode Grandes Cuisines Poligny SAS
Priority date: 2011-10-24
Filing date: 2012-10-22
Publication date: 2019-03-27
Anticipated expiration: 2032-10-22
Also published as: WO2013061241A1; FR2981734B1; EP2771620A1; ES2730714T3; FR2981734A1

Description

The present invention relates to a gas burner of a cooking table or hob, provided with a container detecting system, the aim of which is to provide for supplying the burner with gas when the container is put in a cooking position on the hob, above the burner, and, vice versa, to cut off the gas supply when the container is not on the hob.
The word container means any cooking means able to contain foods and/or liquids to be heated, of the saucepan, frying pan, pot, casserole etc., type made in any appropriate, whether coated or not, material (steel, cast iron, copper, aluminium, ...).
The state of the art includes JP-A-2007 333262 , JP-A-2006 300342 , JP2007 218524A , JP 2006118817A and WO 98/50736 .
Preferably, although not exclusively, hobs provided with burners having a container detecting system are used in professional catering, that is both commercial and collective, for preventing a continuous or nearly continuous use of burners in an open position (high heat) upon operation, when no container is present on the burners. Indeed, it is estimated that the high heat only operates during 30% of the time with a container on the burner.
Thus, significant energy savings are achieved as a result of the gas supply being interrupted as soon as the container is removed from the grid of the hob it is positioned on. Moreover, with such systems, burning risks to the staff by the then open flames of the burners, without containers, are avoided and, in addition, the ventilation needs are reduced.
The systems currently on the market implement either a mechanical detection by the weight of the container operating a contact, by means of a return mechanism and axes, or an electric, ohmic detection using the conduction of the container for closing an electronic contact connected with the gas supply of the burners. The electric signal delivered by the contacts of such systems is sent to a solenoid valve acting on the gas supply of the burners, when the presence of the container on the hob, above the burner, is detected.
Although these systems are widely used, they prove, upon use, to have some drawbacks.
Indeed, as they are located in areas submitted to splashes of any nature to be daily cleaned, and to temperatures able to reach as high as over 300°C, the systems should be often dismantled and assembled again, which is not easy because of their tricky design, more specifically, as far as the weight detection system is concerned (tricky to dismantle return and axis connection mechanism). And they do not also guarantee a long term full tightness with respect to potential electric risks.
Moreover, the ohmic detection system does not operate when containers are externally coated with a coating such as enamel, or even with a cumulated non conductive dirt layer.
The present invention aims at overcoming such drawbacks and relates to a gas burner provided with a container detecting system, wherein the design of the system is novel, simple and reliable, while providing, more specifically, an easy assembling/- dismantling operation and a full independence from the nature of the material of the containers.
To this end, the gas burner is as recited by claim 1.
Thus, thanks to this invention, the presence of the container is detected magnetically by a simple move of the magnet, the magnetic field of which actuates the magnetic detector which, in turn, allows for the opening of the gas supply of the burner. Moreover, as the magnet and the detector are independent from each other, this results in extremely easy and quick assembling/dismantling operations helping to facilitate the cleaning.
The manufacturing simplicity of the resulting system should be noticed, providing, upon use, a high operating reliability and a reduced manufacturing cost through the use of usual components (magnet and detector) withstanding thermal constraints, amongst others. Furthermore, such a magnetic detection system is not responsive to the above described electric conduction problems (enamelled containers, dirt layer, etc.) and is fully tight with respect to electric parts through the absence of seals.
Obviously, such burners thus provided with the magnetic detection system are not only to be used with hobs for professional catering purposes, but also for hobs for private persons.
According to the invention, said magnet and said magnetic detector of the detection system are substantially aligned according to the vertical axis of said burner, said magnet being mounted slidingly with respect to said burner, whereas said detector being integral with the hob is located under said burner.
Thus, a system is achieved operating through a simple translation, in the present case the sliding of the magnet as a result of the contact of the container in a cooking position on the hob, having led to the magnet getting closer in the direction of the detector and thus the variation of the magnetic field. This variation involves, at the level of the gas control of the specific burner, the gas supply of the latter. And moving the magnet apart as a result of the container being removed leads to the supply being cut off through the inverse variation of the magnetic field.
According to the invention, said moving magnet of the detection system is linked to a pusher able to receive said container and mounted slidably in a casing of a support fastened to said burner, a return resilient means in the position of said pusher with respect to the support being provided in the casing. Thus, during the absence of a container, the magnet pusher is maintained in a high position, remote from the magnetic detector closing the gas supply.
In particular, said pusher has the shape of a stem ending, on the upper side, with a flattened conical head arranged so as to receive said container, and wherein, on the lower side, a bore is arranged for receiving said magnet.
Although the choice of a sliding operation of the moving magnet with respect to the detector is preferred, it could be contemplated having a pivoting choice, said magnet pivoting with respect to the burner, and the magnetic detector detecting, as a result of the container being positioned in place, such pivoting of the magnet allowing the gas supply of the burner.
As far as the magnetic detector of the system is concerned, it could be a flexible blade switch, for establishing the electric connection with the gas supply of the burner when the detector is submitted to the variation of the magnetic field as a result of the magnet being brought closer under the weight of the container. Such a structurally simple and reliable choice provides for the operating reliability upon use.
Moreover, on the magnetic detector, a means is provided for adjusting its position with respect to the magnet. For instance, said controlling means comprises a micrometric screw mounted on a stationary support of the detector and acting on the latter against a return resilient means. Thus, it is possible to accurately adjust the moment (corresponding to a variation of the magnetic field) where the supply of the burner should occur and, conversely, the supply should be cut off.
In order to achieve this, an electric connection is provided between the magnetic detector and a solenoid valve controller controlling the gas supply of the burner.
This invention also relates to a hob comprising at least one gas burner with which there is associated a system for detecting a container. Advantageously, said detection system is such as defined above.
The FIGS. of the appended drawing will better explain how this invention can be implemented.
FIG. 1 is a partial perspective view of an embodiment of a hob having each represented gas burner being provided with a container detection system according to this invention.
FIG. 2 is a sectional and enlarged perspective view of one of the burners with its detection system.
FIG. 3 shows in a longitudinal section, the burner with the detection system in its two positions, respectively in the absence and in presence of a container.
As shown on FIG. 1, the hob 1 comprises, in the illustrated embodiment, two gas burners 2, 3 provided with a container detecting system 4. A different number of burners is obviously possible. This hob 1 usually has the shape of a parallelepipedic tray with a bottom 5, side walls 6 and an upper part 7 with an aperture 8 on the circumference of which a grid 9 is arranged being able to receive the cooking means such as the container R illustrated in mixed line on FIG. 3.
Under the grid 9 the two burners 2, 3 are arranged, respectively in the front and in the rear with respect to the exterior side wall 6 of the hob 1, and supplied with gas by individual delivery ducts 10 connected to the cylindrical pots 11 of a vertical longitudinal axis A of the burners, only the duct 10 of the rear burner being shown on FIG. 1.
With each burner a safety/ignition assembly 12 is furthermore associated, comprising more specifically a pilot light, a thermocouple and an ignition electrode and on which lies, through non shown complementary fastening means, the side skirt of the cylindrical pot 11 of the corresponding burner. Such a safety/ignition assembly 12 will not be further detailed, and could be, for information, that described in European patent 1,225,394 in the name of the Applicant.
More specifically on FIGS. 2 and 3, the gas delivery duct 10 can be seen in the direction of the burner 2, which duct is on one side, fastened to the corresponding side wall 6 of the hob with screws and, on the other side, to the cylindrical pot 11 of the burner. Upstream the duct 10 a jet 13 is arranged being connected to the gas supply controlled by a solenoid valve controller 14 being schematically shown in the shape of a rectangular pad on FIG. 3.
The container detection system 4 on its respective burner, such as the burner 2 on FIGS. 2 and 3, is according to this invention of the magnetic type and comprises, to this end, two main components, that is a magnet 15 and a detector 16. The magnet 15 is associated with the burner 2, whereas the detector 16 is integral with the hob 1, in particular the bottom 5 thereof.
In order to detect the presence of a container positioned on the grid 9, and as a result, allow for the gas supply of the burner 2, the magnet 15 is made movable with respect to the burner so that the variation of the magnetic field, generated by the movement of the magnet, is noticed by the detector 16. In this embodiment, the movement of the magnet 15 is sliding and is achieved by a pusher 17 with which the magnet 15 is associated and being mounted slidably in a tubular shaped support 18 fastened to the pot 11 of the burner. The thus assembled pusher and support as an actuator are of a cylindrical shape and are arranged at the centre of the burner 2, substantially in the vertical longitudinal axis A of the cylindrical pot 11.
In particular, the pusher 17 comprises a stem 19 mounted slidably in a casing or an axial passage 20 of the support 18, and ending in a flattened conical head 21. This projects from the grid 9 by an appropriate distance D, so as to act as a contact with the container when the latter is positioned on the grid, as will be further detailed later on. At the opposite of the head 21, the stem 19 is drilled with a bore 22 inside of which the magnet 15 is integrally received.
As far as the support 18 of the pusher and therefore of the magnet 15 is concerned, it is immobilized by a fastening member 23, such as a recessed nut, in a transversal base 24 integral with the cylindrical pot 11. The support 18 therefore stands vertically in the axis A of the burner 2, while crossing it throughout its length with the flattened conical head 21 projecting from the grid 9.
In the internal passage 20 of the support 18, between the bottom of the recessed nut 23 and an external annular shoulder 25 of the pusher, a return resilient means 26 is provided, such as a helical spring, acting so as to spontaneously returning the pusher in an outlet position as soon as a container is removed from the grid, with its flattened head 21 located above the grid 9 by the desired distance D.
The magnetic detector 16 is, as far as it is concerned, aligned substantially under the «magnet 15 pusher 17 - support 18» assembly and is arranged in an axial casing 28 of a stationary support 29, in the shape of a tubular foot. This foot 29 is fastened perpendicularly to the bottom 5 with one, lower, of its ends. As the bottom is somewhat tilted for draining water, the support foot is not strictly vertical and aligned with the pusher according to the axis A, as shown on the FIGS. As far as the upper end of the foot is concerned, it is obstructed by a protective plug 30 covering a micrometric screw 31 to be screwed on such upper end and acting, for setting purposes, against the detector 16. For instance, the latter is a flexible blade switch of the Reed bulb type, more specifically selected for its operating reliability, its resistance to high temperatures and its low cost.
Furthermore, an electric connection 32 goes out of the detector 16 in the passage 28 of the tubular foot 29, then crosses the bottom 5 so as to be connected to the solenoid valve controller designated in 14 by the rectangle and connected to the inlet of the delivery duct 10 with the jet 13 so as to allow for the gas supply in the latter.
Moreover, in the casing 28 of the tubular foot 29, between the magnetic detector 16 and the bottom 5 a return resilient means 33 is arranged, such as a helical spring, constantly acting on the detector so as to maintain it against the adjusting screw 31. This, the spacing distance could be accurately adjusted between the magnet 15 and the detector 16 as desired so as to determine the variation of the magnetic field value necessary for triggering the gas supply of the burner. The micrometric screw 31 allows such a function
When no container is positioned on the grid 9 of the hob 1 (FIGS. 2 and 3), the flattened head 21 of the pusher 17 externally protrudes from the grid, by the predetermined distance D, under the action of the spring 26 placing in abutment the shoulder 25 of the pusher against an internal shoulder 34 arranged in the axial passage 20 of the support 18. The magnet 15 integral with the pusher is spaced apart from the detector 16 by a distance D1 for which the magnetic field generated by the magnet will have no effect on the magnetic detector. Thereby, no signal is sent by the link 32 to the controller 14, corresponding to the gas supply being cut off in the direction of the relevant duct 10 of the burner 2.
On the other hand, when a container R shown in mixed line on FIG. 3 is placed in a cooking position being positioned on the grid 9, the bottom RF of the container is applied against the flattened head 21 leading to the descent of the pusher 17 according to the axis A, by the distance D. The head 21 is located at the level of the grid 9 and the magnet 15 has come closer to the magnetic detector 16 for being located at a distance D2, equal to D1-D. As the magnet 15 comes closer to the detector 16, this results in an increase of the magnetic field the variation of which results in the detector 16 being actuated. The latter then delivers, via the link 32, a signal to the controller 14 allowing for the gas supply of the burner 2 via the delivery duct 10, and the ignition of the flame by the relevant assembly 12.
As soon as the container R is removed from the burner, after cooking, the pusher 17 is spontaneously returned in the high outlet position, with its head 21 projecting from the grid 9, by the helical spring 26 resulting in the magnet 15 being spaced apart from the detector 16 with a decrease of the magnetic field, and the simultaneous cut off of the gas supply of the burner 2.
Thus, such a burner with a magnetic system for detecting a container allows, in addition to limiting the energy consumption to the single presence of a container on the hob, to be insensitive to the electric conductive value of the container being used, easy to assemble/dismantle and to clean through the composition of the system into two main independent components (magnet pusher - detector), robust upon use, without making use of seals and of a low cost. Furthermore, the system is particularly tolerant to geometry deviations, such as angle or position deviations.

Claims

A gas burner for a hob, provided with a container detecting system (4),
said detection system being configured for enabling the gas supply of the burner when the presence of the container is detected and for disrupting the gas supply of the burner when the absence of the container is detected,
said detection system (4) is of the magnetic type and comprises
- a moving magnet (15), connected to said burner and arranged for being able to be moved by the container when the latter is placed in a cooking position, and

- a magnetic detector (16) arranged on the hob for detecting the movement of the magnet by the container, and in that said magnet (15) and said magnetic detector (16) of the detection system are substantially aligned according to the vertical axis (A) of said burner, said magnet being mounted slidably with respect to said burner, whereas said detector integral with the hob is located under said burner,
characterized in that
said moving magnet is linked to a pusher (21) able to receive said container and mounted slidably in a casing (20) of a support (18) fastened to said burner, a return resilient means (26) in the position of said pusher with respect to the support being provided in the casing
and in that
the magnetic detector (16) comprises a means for adjusting its position with respect to the magnet.
The burner according to claim 1, wherein said pusher (17) is of the shape of a stem (19) ending, on the upper side, in a flattened conical head (21) arranged so as to receive said container, and wherein, on the lower side, a bore (22) is arranged for receiving said magnet.
The burner according to any of claims 1 to 2, wherein said magnetic detector (16) of said system is a flexible blade switch for establishing the electric link with the gas supply of the burner when it is submitted to the variation of the magnetic field as a result of the magnet (15) being brought closer under the weight of the container.
The burner according to any of claims 1 to 3, wherein said adjusting means comprises a micrometric screw (31) mounted on a stationary support (29) of the detector and acting on the latter, against a return resilient means (33).
The burner according to any of claims 1 to 4, wherein an electric link (32) is provided between the magnetic detector (16) and a solenoid valve controller (14) controlling the gas supply of the burner.
A hob (1) comprising at least one gas burner (2, 3) with which there is associated a system (4) for detecting a container (R),
characterized in that said detection system (4) is such as defined by any of claims 1 to 5.