Gas burner with a control thermocouple

Abstract: A gas burner with a control thermocouple, comprising a support (4) in which a seat (38) is provided for a thermocouple (42) powering the electromagnet (18) of a safety valving member (22), characterised in that said seat (38) has its base insulated from its side wall and provided with a connector (48) permanently connected to said electromagnet and connectable to a pole provided at the lower end of said thermocouple when this is inserted into said seat from above and has its side wall, at which the other pole terminates, in contact with the side wall of the seat (38).

Description: This invention relates to a gas burner with a control thermocouple. Gas burners with a control thermocouple are known, particularly for built-in cooking hobs. One known type comprises a cup-shaped support, a burner body in which a stream of gas and air is created, and a flame divider applied to the burner body and comprising a plurality of holes through which this stream is made to leave in order to be ignited. The burner is often provided with a themocoupled which when struck by a flame from the ignited gas leaving one of said holes generates a weak electric current powering an electromagnet which by overcoming the elastic reaction of a spring keeps open a valving member via which the gas is fed into the burner. If the flame is extinguished, either by voluntary intervention of the user or for accidental reasons, the thermocouple ceases to generate the weak current, the electromagnet is no longer energized and the effect of the spring prevails on it to return the valving member into its closed position. On re-igniting the gas the electromagnet has to be reset, by manually holding the valving member open against the action of the spring for the flame to heat the thermocouple and allow it to generate the weak current enabling the electromagnet to maintain the valving member open. The connection between the thermocouple and the electromagnet is currently in the form of a coaxial cable, which is directly welded to the two thermocouple terminals and is connected to the electromagnet terminals by a threaded quick connector. Consequently in order to fix the thermocouple, to which the coaxial cable is welded, in its seat in the burner body it has to be inserted sideways from below, involving a certain effort and slowness in installing and replacing the thermocouple because of the need for access to the interior of the cooking hob. GB-A-2249383 describes a gas cooker comprising two burners and a gas valve operated by a push and twist control knob controlling the supply of gas both of the burners and two thermocouples to detect the presence or absence of flame at the burners, the arrangement being such that the gas valve will be closed in response to the absence of flame at either one or both of the burners and detected by the corresponding thermocouple. The main object of the invention is to enable the thermocouple of a gas burner for a cooking hob to be installed and replaced without the need for access to the hob interior. This and further objects which will be apparent from the description given hereinafter are attained according to the invention by a gas burner with a control thermocouple powering the electromagnet of a safety valving member, as described in claim 1. Two preferred embodiments and two executive modifications of the present invention are described in detail hereinafter by way of an example with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a gas burner according to the invention; Figure 2 is a vertical section on the line II-II of Figure 3 showing it in its assembled state; Figure 3 is a vertical section therethrough on the line III-III of Figure 2; Figure 4 is a detailed partial exploded perspective view showing a modified execution of the thermocouple connection; Figure 5 is the same view as Figure 4, but showing a further modified execution; and Figure 6 is a perspective view of a different embodiment of the burner support. As can be seen from the figures the burner according to the invention, indicated overall by 2, comprises in the embodiment shown in Figures 1-3 a cup-shaped support 4 provided lowerly with a pair of feet 6 with indentations 8 for its bayonet-fitting into the base 10 of the cooking hob 12. For this purpose, in a position below the circular aperture provided in the cooking hob 12 for the burner 2, said base 10 comprises two shaped apertures 14 through which the two feet 6 can be inserted, their indentation 8 then being made to engage the edge of said apertures by rotating the cup-shaped support 4, to hence bayonet-fit said support 4 to the base 10 in an extremely rapid and simple manner. Within the cup-shaped support 4 there is provided a radial duct 16 housing an electromagnet 18 for operating the valving member 20, which connects the gas feed pipe 22 to a nozzle 24 provided axially on the base of the support 4. On the diametrical prolongation of the duct 16 there is provided a resetting unit 26 for the electromagnet 18, comprising a rod 28 operable axially to temporarily urge the valving member 20 into its open position against the elastic reaction of a spring 30. In the lateral wall of the cup-shaped support 4 there are provided, in diametrically facing positions, two vertical thickened regions 32 and 34 provided with two seats 36 and 38 for an ignition spark plug 40 and for a thermocouple 42 respectively. The seat 36 for the spark plug 40 is of essentially cylindrical shape and houses in its wall one or more spring clips 44 for the snap-engagement of the spark plug 40, which can be inserted into the seat from the top, ie from above the cooking hob 12. Alternatively the seat 36 for the spark plug 40 can be internally threaded so that the spark plug 40 can be engaged by screwing-in. The seat 38 for the thermocouple 42 is also of essentially cylindrical shape and is internally threaded, with its lower part arranged to allow the insertion of an insulating block 46, in the base of which, accessible from above, there terminates a metal strip 48 connected to the electromagnet 18 by a cable 50. In proximity to its upper edge the cup-shaped support 4 also comprises a flange 52 on which the cooking hob 12 can rest, as described hereinafter. In the cylindrical wall above this flange there is provided a circumferential groove 54 for a steel locking ring 56. The burner of the invention also comprises a body 58 to be fitted to the cup-shaped support 4 and comprising an axial duct 60 forming part of the Venturi tube and comprising in its lower wall a plurality of angularly equidistant identical apertures 62 surrounded by an adjustment ring 64. This comprises further equidistant apertures 66 which face the apertures 62 to a greater or lesser extent depending on the angular position of the ring 64, to hence enable the quantity of air drawn from the outside by the Venturi effect provided by the gas leaving the nozzle 24 to be adjusted. The angular position of the ring 64 relative to the axial duct 60 is maintained by a screw 70 passing through a slot 72 provided in the ring 64 and engaging the duct. The burner body 58 is maintained with the lower end of the axial duct 60 slightly spaced from the base of the cup-shaped support 4 by feet 74 projecting lowerly from the body 58 and resting on an inner circumferential step 78 provided in proximity to the upper adge of the support 4. Three spaced-apart feet 74 are provided; two of these are perfectly cylindrical whereas the third has a certain circumferential development so as to interfere with the thickened regions 32, 34 of the cup-shaped support 4, and hence determine a unique angular position of the burner body 58 relative to said cup-shaped support 4. With reference to this obligatory angular position the upper part 76 of the burner body 58 comprises two internal thickened regions 80 and 82 comprising a seat 84 and 86 acting as vertically upward extensions of the seat 36 and 38 for the spark plug 40 and thermocouple 42 respectively. The burner according to the invention also comprises a flame divider 88 of traditional form, provided with a plurality of radial holes for the emergence of the air-gas mixture and also provided with an indentation 90 cooperating with a projection 92 provided on the upper part 76 of the burner body 58 to prevent relative rotation. These holes can be provided in one or two circumferential rows and in themselves do not form part of the invention. Finally the flame divider is closed upperly by a removable cover 94. When suitably assembled one on the other, the described components form the burner of the invention. For its installation the cup-shaped support 4 is firstly bayonet-fitted into the hob 10 after which the various connections are made to the gas feed pipe, to the power unit for the spark plug 40 and to the mechanical or electrical controls of the resetting unit 26. With particular regard to the connection to the power unit, a cable generally extends from this unit and is provided at its end with one element of a quick connector of fast-on type. The other element of the fast-on connector is generally fixed directly to the spark plug 40. After the two elements of the fast-on connector have been connected together and the spark plug 40 has been inserted into its seat 36 and snap-locked by the spring clip 44, the cooking hob 12 is fitted. For this purpose a silicon rubber ring 53 on which to rest the cooking hob 12 is placed on the cup-shaped support 4 of the burner, or rather on the flange 52 of all the installed burners, the hob then being locked to each burner by fitting the locking ring 56 into the corresponding groove 54. This locking action is provided by that portion of the ring 56 which projects from the groove 54, and can be improved if instead of being perfectly circular, as shown in the drawings, the ring comprises a plurality of projecting arms uniformly distributed along its circumference. This enables the aperture provided in the cooking hob 12 at each burner to be made somewhat larger than the diameter of the cup-shaped support 4, hence making the installation of the cooking hob 12 substantially more comfortable and rapid. The termocouple 42 is then mounted on the cup-shaped support 4. To achieve this, said thermocouple is inserted into its seat 38 and then pushed downwards until its lower terminal adheres to the strip 48 to provide electrical contact therewith. A gasket 43 is interposed between the thermocouple 42 and the upper edge of its seat 38 to prevent agents which could oxidize the contact between the thermocouple and the strip from entering said seat. This electrical contact can also be improved by silver-plating the strip 48 and the lower end of the thermocouple 42. Then after the adjustment ring 64 has been fixed in the required angular position on the radial duct of the burner body 58, this latter is placed in position and on it are then positioned the flame divider 88 and the cover 94. If after a certain time the spark plug 40 needs replacing, the cover 94, the flame divider 88 and the burner body 58 are firstly removed, then the spark plug is withdrawn upwards from its seat, so also withdrawing its ignition cable until the fast-on connector emerges. Then after replacing the spark plug, the duct with the new spark plug connected to it is reinserted into the seat 36 until it becomes locked by the spring clip 44. If the thermocouple 42 needs replacing, this can be achieved with equal ease and rapidity by simply unscrewing the thermocouple 42 from its seat after removing the cover 94, the flame divider 88 and the burner body 58. From the aforegoing it is apparent that the burner of the invention is particularly advantageous compared with traditional burners in that the installation and replacement of the thermocouple are made extremely rapid and simple, without requiring access to the interior of the cooking hob 12 and hence without having to remove it. In addition to this important advantage the burner of the invention also has further advantages, and in particular: because of the fact that the electromagnet 18 is mounted in the cup-shaped support 4 instead of in the gas tap operated by the external control knob, normal gas taps can be used, ie not especially designed for thermoelectric safety, and hence smaller and much less costly; the fact of mounting the electromagnet in the cup-shaped support eliminates one of the two cables which connect the thermocouple to the electromagnet, consequently substantially simplifying the assembly of the cooking hob in that the burner is supplied by the manufacturer as a preassembled unit complete with all accessories; because the spark plug can also be inserted from above, all maintenance can be done without it being necessary to remove the cooking hob; the air flow adjustment system using the ring 64 enables much finer adjustment to be achieved than in the case of traditional systems in which a sleeve axially adjustable relative to the Venturi duct is used; it also eliminates the risk of losing the adjustment, in contrast to traditional air flow adjustment systems in which the position of the adjustable sleeve is maintained by a small screw, which on the one hand is not allowed to penetrate into the interior of the Venturi duct otherwise it would alter its operation and on the other hand if not properly tightened cannot ensure that the sleeve is securely fixed to the Venturi duct, in particular because of thermal expansion; the bayonet system used for fixing the cup-shaped support 4 to the underlying base makes very rapid assembly possible without the use of screws or other implements and without having to operate from underneath said base; the systems used for fixing the cooking hob to the cup-shaped support 4 avoids the need for screws, which always require a certain effort for their application, together with the need to make threaded holes and the risk of damaging the enamel of the cooking hob; finally the fact that the thermocouple 42 and spark plug 40 are housed within the cup-shaped support 4 results in improved protection of said components against impact and dirt, easy cleanability of the cooking hob and considerable simplification of its manufacture, which requires only one circular hole to be made for each burner. In the executive modification shown in Figure 4, in which the safety unit comprising the electromagnet 18, its resetting unit 26 and the valving member 20 has been omitted for simplicity of representation, the cup-shaped support 4 comprises an appendix 96 containing, in a position vertically below the seat 38 for the thermocouple 42, a seat 98 for housing as an exact fit a connector 100 for the thermocouple. This connector comprises a cylindrical base 102 to which a concave terminal 104 is upperly fixed and electrically insulated from the base 102 by an insulating element 106. A coaxial cable 50 has its core 108 connected to the terminal 104 and its sleeve 110 connected to the concave terminal 104. The coaxial cable 50 is connected to the electromagnet 18. This modification enables standard connectors 100 to be used for connecting the thermocouple 42, in contrast to the preceding. In the executive modification shown in Figure 5 the cup-shaped support 4 comprises, in a position below the seat 38 for the thermocouple 42, a small compartment 112 open laterally for the insertion of a U-shaped spring 114, on the upper part of which there is applied a layer of insulating material 116 on which the terminal 118 is applied for central contact with the thermocouple 42. The connection cable 50 from the electromagnet 18 is connected to the terminal 118. This modification is advantageous for the greater ease of mounting of the thermocouple terminal and hence for the improved ability to industrialize the burner assembly cycle. In the embodiment shown schematically in Figure 6, the seat for the electromagnet 18 is provided in the cup-shaped support 4 immediately below the seat 38 for the thermocouple 42, hence also eliminating the connection cable 50 between the two and the inevitable contact resistance which this implies, and in addition achieving a more compact configuration and a more rapid installation of the burner.

Claims: A gas burner with a control thermocouple (42), comprising a support (4) in which a seat (38) is provided for a thermocouple (42) powering the electromagnet (18) of a safety valving member (22), characterised in that said seat (38) houses an insulating element (46,106,116) provided with a connector (48,104,118) permanently connected to said electromagnet (18) and connectable to a pole provided at the lower end of said thermocouple (42) when this is inserted into said seat (38) from above, said thermocouple (42) having its side wall, at which the other pole terminates, in contact with the side wall of the seat (38). A gas burner as claimed in claim 1, characterised in that the support (4) is of cup-shaped type. A gas burner as claimed in claim 1, characterised in that the seat (38) provided in the support (4) consists of a cylindrical cavity with a threaded side wall, into which a threaded portion of said thermocouple (42) is screwed until its end pole makes contact with the corresponding connector (48,104,118) provided in the insulated element (46,106,116). A gas burner as claimed in claim 1, characterised in that the insulating element (46) supports a strip (48) connected to said electromagnet (18). A gas burner as claimed in claim 1, characterised in that the support (4) comprises a lateral appendix (96), in which in a position vertically below the seat (38) for the thermocouple (42) there is provided a seat (98) for a connector (100) formed from two parts (102,104) electrically insulated from each other, namely an outer part (102) for its fixing into said seat (98), and an inner part forming the connector (104) connectable to the lower pole of the thermocouple (42). A gas burner as claimed in claim 5, characterised in that the two parts (102,104) of the connector (100) are connected respectively to the sleeve (110) and to the core (108) of a coaxial cable (50) connected to the electromagnet (18). A gas burner as claimed in claim 1, characterised in that the support (4) comprises a compartment (112) open laterally for the insertion of an elastic U-piece (114) comprising a portion facing the seat (38) for the thermocouple (42) and carrying an applied terminal (118), which is electrically insulated from the remaining part of the elastic U-piece (114) and is connected to the electromagnet (18). A gas burner as claimed in claim 3, characterised in that the lower end of the thermocouple (42) and the connector (48,104,118) are silver plated. A gas burner as claimed in claim 4, characterised in that the insulating element (46) is mounted on the support (4) by sliding. A gas burner as claimed in claim 1, characterised in that a seal gasket (43) is interposed between the thermocouple (42) and the upper edge of its seat (38) in the support (4). A gas burner as claimed in claim 1, characterised in that in the support (4) there is provided an additional seat (36) for a spark plug (40), which is insertable into it from above. A gas burner as claimed in claim 11, characterised in that at least one spring clip (44) for the snap-engagement of the spark plug (40) is provided in the additional seat (36). A gas burner as claimed in claim 11, characterised in that the additional seat (36) for the spark plug (40) consists of an internally threaded cylindrical cavity into which said spark plug can be screwed. A gas burner as claimed in claim 11, characterised in that on the support (4) there is positioned a burner body (58) comprising an axial duct (60) facing a nozzle (24) provided on the base of said support (4) and an upper support part for a flame divider (88), the lower wall of said axial duct being provided with a plurality of apertures (62) with which there is associated a ring (64) provided with an identical number of apertures (66) and adjustable in its angular position relative to said axial duct (60). A gas burner as claimed in claim 14, characterised in that a screw (70) is associated with the duct (60) of the burner body (58) to lock the adjustment ring (64) in the desired angular position relative to the duct (60). A gas burner as claimed in claim 2, characterised in that the base of the cup-shaped support (4) comprises at least two feet (6) for bayonet-fitting said support (4) into corresponding apertures (14) provided in the base (10) of the cooking hob (12). A gas burner as claimed in claim 1, characterised in that the support (4) is provided with a circumferential flange (52) for supporting the cooking hob (12), and with a circumferential groove (54) above said flange for housing a split ring (56) for locking said cooking hob (12) to said support (4). A gas burner as claimed in claim 17, characterised by comprising a silicone rubber gasket (53) to be interposed between the flange (52) of the support (4) and the cooking hob (12). A gas burner as claimed in claim 14, characterised in that in the support (4) and in the upper part of the burner body (58) there are provided two thickned regions (32,34) in which two seats (36,38) are provided for the spark plug (40) and for the thermocouple (42), which are located inwards of the perimeter of the flame divider (88). A gas burner as claimed in claim 1, characterised in that the safety valving member (22) and the seat for its electromagnet (18) are formed directly within the support (4). A gas burner as claimed in claim 20, characterised in that the electromagnet (18) of the safety valving member (22) is housed within a seat formed directly below the seat (38) for the thermocouple (42).

Inventors: ROS ROBERTO, ROS, ROBERTO
Applicants: DEFENDI OFF MEC SRL, OFFICINE MECCANICHE DEFENDI S.R.L:
Application year: 1993
Main classification: F23D14
IPC codes: F24C3, F23D14