CONTROL DEVICE INCLUDING A GAS TAP AND A CATENARY ELEMENT FOR BURNERS OF A COOKING RANGE

TECHNICAL FIELD The present invention relates to a control device for the burners (also simply known as "cooker-rings") of a cooking range, including a gas tap and a catenary element controlled by the movement of a mobile stem of the gas tap.

BACKGROUND ART

The known control devices for the cooker-rings of a cooking range (either of the built-in type, or of the type belonging to a combined household appliance, e.g. including an oven and/or a dishwasher) comprise for each cooker-ring a gas tap and a catenary element provided with a micro switch, the operation of which supplies voltage to a lighter circuit of the cooking range, of a known type, which produces a spark at one or all cooker-rings. The gas tap is generally provided with an axially mobile, rotational control stem provided in use with a control knob, the rotation of which (which for reasons of safety is only possible by determining a simultaneous axial displacement of the mobile element) allows to supply combustible gas to the cooker-ring.

In order to ensure the lighting of the combustible gas as soon as this is supplied to the cooker-ring, the axial movement of the stem/knob assembly is also used to actuate the micro switch, thus producing the generation of the lighting spark simultaneously to gas supply.

In the device known from EP1194720B1, the micro switch is provided with a rocking or translating control

lever, which is snappingly anchored to the mobile stem of the gas tap by means of a C-shaped, snap ring, integrally formed in one piece with the free end of the control lever, so that the latter is axially anchored to be axially displaced along with the stem, however without being rotationally anchored to the same, because the snap ring slides idly in its assembly seat (generally an annular groove) on the stem.

Such a device displays the two-fold drawback of needing to be mounted with extreme accuracy in order to prevent the control lever of the micro switch from damaging and, in use, of being subject to wear due to the continuous rotational sliding to which the snap ring is subjected, the snap ring which anchors the control lever of the micro switch, generally consisting of a catenary element, to the tap stem.

Therefore, in case of damage to even a minimum part of the entire control assembly consisting of the taps and the catenary element, such as that consisting of the control lever with the corresponding snap ring, it is required to replace the whole catenary, with times and costs increasing.

From EP-A-1500881, there is further known a different solution, consisting of a flanged annular bushing which is snappingly fitted on the stem and which may therefore rotate integrally with the same, in addition to being displaced along with the stem; the flanged part of such a bushing is used to interact with the lever of the micro switch, thus actuating it; it is apparent that, in order to ensure the actuation of the micro switch in any annular position of the stem (and of the corresponding bushing) , the flanged part of the bushing must not essentially display any appreciable interruption of continuity. Indeed, it only displays a radial slit which is a few

millimeters wide and the snap-fitting of the bushing as a whole is allowed by a particular shape of the same.

This particularly satisfactory solution generally requires the use of a specific tool for snap fitting the bushing because a relative high mounting force must be exerted on the same.

DISCLOSURE ON INVENTION

It is the object of the present invention to provide a control device of the above described type, which is however free from the drawbacks of EP1194720B1 and which, at the same time, may be mounted by exerting a relatively low mounting force and, thus, without using tools. Specifically, it is an object of the invention to provide a control device for cooker-rings of a cooking range which may use a standard-type catenary while ensuring the actuation of the micro switch in any relative angular position of the tap stem, and which is furthermore cost- effective to make, easy and quick to assemble, of reduced dimensions and high reliability.

According to the present invention, a control device for the cooker-rings or burners of a cooking range is made as defined in claim 1.

Specifically, according to the invention, the device comprises a catenary element for controlling the lighting of the burners and a gas tap provided with a rotating, axially mobile control stem; the catenary element includes a micro switch, a control rod of which is actuated upon an axial motion of the stem, as in EP-A-1500881, by an element (a washer in this case) entirely disjoined from the micro switch and snappingly carried by the stem in a position immediately over the control rod of the micro switch.

According to a first aspect of the invention, the washer is integrally made of a synthetic plastic material and is essentially C-shaped from a plan view, comprising a flange portion delimited by an essentially circular peripheral edge and is provided with a central through hole and a radial opening which interrupts the continuity of the flange portion from the peripheral edge and to the through hole, the radial opening being flanked on both opposite longitudinal sides thereof by corresponding fins which protrudingly extend, parallelly to the hole, from a lower side of the flange portion, in use facing the micro switch, and are shaped so as to be adapted to intercept opposite side flanks of the control rod of the micro switch in use upon a possible relative rotation between the washer and the micro switch. Furthermore, the washer idly engages the stem of the tap, so as to be able to relatively rotate with respect to the same.

Specifically, the washer further comprises an annular collar over the flange portion which extends from the flange portion, parallel to the through hole of the flange portion, on the side opposite to the lower side of the same provided with the protruding fins. The through hole displays a diameter smaller than that of the annular collar as approximately the double the radial depth of an annular groove of the stem of the gas tap in which the washer is snappingly engaged in use.

In this manner, an overall device which is very easy and quick to assemble is obtained, because the washer serving as abutting actuating element for the micro switch is totally disjointed from the same and may thus be mounted on the gas tap (on the stem of the gas tap in this case) separately from the micro switch. This may therefore be mounted either before or after the washer, directly onto the body of the gas tap in a known manner,

e.g. snappingly, and may thus belong to a standard-type catenary, unlike the micro switch of EP1194720B1.

At the same time, the washer being highly flexible by virtue of the wide radial opening thereof, the width of which is essentially equal to the diameter of the hole if measured in a circumferential direction, the washer may also be easily and rapidly mounted, even without tools, by orienting the radial opening as far away as possible (on the opposite side) from the control rod of the micro switch to be actuated, by ensuring that such a radial opening, which interrupts the continuity of the flanged portion of the washer for a much larger angular width than the dimensions of the control rod of the micro switch, will never be in any case placed at such a control rod, despite the rotation in use of the tap stem operated by the user, both for lighting and then for adjusting the flow rate of the gas to be fed to the flame.

As a matter of fact, when the tap stem is rotated in use, the washer, which is snappingly mounted but idle on the same and is thus angularly and integrally anchored to the stem only by "static" or "breakout" friction, will rotate along with the stem but only to have one of the two fins (according to the direction of rotation) abutting against a side flank of the control rod. At this point, the washer will no longer be able to rotate while the stem will be free to complete the rotation set by the user, because the washer is free to slide with a low friction (once the static or breakout friction is overcome, which is commonly much higher than the "dynamic" friction, i.e. than the friction between the two relatively moving bodies) in its mounting seat on the stem, preferably consisting of an annular groove.

In this manner, however, the washer of the control device according to the invention, unlike the snap ring

anchoring the stem to the rod of the micro switch of EP1194720B1, is forced to only occasionally rotate relatively to the tab stem, i.e. when the condition of interference occurs between a fin and the rod of the micro switch. Therefore, on the one hand, the wear in use of the washer of the device according to the invention is considerably lower than that of the corresponding element of EP1194720B1; and, on the other hand, if and when the washer of the device according to the invention is worn or broken, it will be sufficient to replace it with another identical washer, without involving replacements of neither the gas tap nor the catenary to which the micro switch belongs, thus with very low costs and intervention times . The entire control device according to the invention then has a low cost, because it uses standard components (gas tap, catenary) or low production cost components, such as the aforesaid C-washer.

On the basis of the foregoing description, the invention further relates to a washer for the snapping application on a stem of a gas tap for actuating a control rod of a micro switch upon an axial displacement movement of the stem, according to claim 10.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will be apparent from the following description of a preferred embodiment thereof, exclusively provided by way of non-limitative example, with reference to the accompanying drawings, in which:

- figure 1 shows a top perspective view of a control device made according to the invention; and figure 2 shows, on an enlarged scale, a top

perspective view of an essential element of the control device in figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION In figures 1 and 2, numeral 1 indicates as a whole a control device for the cooker-rings or burners of a cooking range (known and not shown for the sake of simplicity), comprising a standard-type gas tap 2, thus known, provided in use with a control knob (known and not shown for the sake of simplicity) and an element 4 of a catenary 5 (known as a whole and of which only the element 4, along with a pair of electric wires 6 connected in cascade to other identical elements 4 (not shown) is therefore illustrated for the sake of simplicity, the wires 6 being shown only with dashed lines for the sake of simplicity) for controlling the lighting of the mentioned cooker-rings of the aforesaid cooking range (known and not shown) .

According to the invention, the catenary 5 is also a standard-type catenary, and the catenary element 4 comprises a micro switch 7, also of a known type, snappingly and integrally mounted (in a known manner which is therefore not described in detail) to a body 9 of the gas tap 2, which is in turn provided with a control stem 10, rotating and axially moving about and along an axis A, arranged vertically in use.

The micro switch 7 displays a control rod 11, which is actuated in use upon an axial motion (a sliding motion along the axis A) of the stem 10 by an abutting element which, according to a first aspect of the invention, is defined by a washer 12, better illustrated in figure 2 on an enlarged scale, made as an element totally disjointed from the micro switch 7 and snappingly carried by the stem 10 in a position immediately over the control rod 11 of the micro switch 7, as clearly shown in figure 1.

The washer 12 is integrally made of a synthetic plastic material and is essentially C-shaped according to a plan view (i.e. parallel to the laying plan thereof, which is perpendicular to axis A) , because it comprises a flange portion 15 delimited by an essentially circular peripheral edge 16 and is provided with a central through hole 18 and a radial opening 20 which interrupts the continuity of the flange portion 15 from the peripheral edge 16 and to the through hole 18. According to a fundamental aspect of the invention, the radial opening 20 is flanked on both opposite longitudinal sides 21,22 thereof by corresponding fins 23 which protrudingly extend, parallel to the hole 18, and thus in an axial direction with respect to axis A, from a lower side 25 of the flange portion 15, facing in use the micro switch 7.

The fins 23 are shaped so as to be adapted to intercept in use opposite side flanks 26 of the control rod 11 of the micro switch 7 following a possible relative rotation between the washer 12 and the micro switch 7, e.g. caused by a rotation of the stem 10 about the axis A.

It is indeed worth noting that according to the invention, while snappingly engaging the stem 10 in the manner which will be described below and, thus, being able to follow the same in rotation by effect of the static or "breakout" friction which is normally present between two bodies in reciprocal contact, according to the invention the washer 12 is idly mounted on the stem 10 of the tap 2, i.e. it engages along with the through hole 18 thereof a cylindrical portion of the stem 10 by means of a coupling which, according to the normal machining tolerances, can be defined "free" (i.e. with radial clearance, e.g. h7/F8 according to the basic shaft system) or "uncertain" (i.e. with clearance close to zero, e.g. h7/H8), and in all cases it is therefore free to rotate relatively to the

stem 10 with a low friction (in this case "dynamic" and of "skimming" type), i.e. by sliding on the stem 10.

In order to ensure a correct coupling with the stem

10 in the above-described manner, the washer 12 further comprises an annular collar 30 over the flange portion 15 and which extends from the flange portion 15, parallel to the hole 18 (and therefore axially in the direction of axis A) , on the side opposite to the lower side 25 of the flanged portion 15, i.e. on the opposite sides with respect to the protruding fins 23 provided on the face 25 itself.

The radial opening 20 also interrupts the continuity of the annular collar 30, which is thus laterally open; the radial opening 20 further displays a width, measured transversally to an axis of symmetry of the through hole 18, coinciding in use with axis A, essentially equal to the diameter of the hole 18 itself.

The fins 23 extend transversally to the hole 18 and parallel to the longitudinal sides 21, 22 of the opening 20, between the immediate proximity of the peripheral edge 16 of the flange portion 15 and the immediate proximity of the collar 30, whereby they essentially flush or nearly flush with both.

Essentially, at the radial position of the annular collar 30 and inside the radial opening 20 which interrupts the continuity thereof, the flange portion 15 is further provided with corresponding prismatic teeth 40,

41 (figure 2) to snappingly engage the stem 10, obtained flushing with the through hole 18 and which protrudingly extend, in a circumferential direction and from opposite longitudinal sides 21, 22 of the through opening 20, within the latter.

Specifically, the teeth 40, 41 extend in a radial

direction for the entire length, along such a radial direction, of the annular collar 30 and display on the laying plane of the flange portion 15, an essentially trapezoidal shape according to a plan view, as clearly shown in figure 2.

In this manner, the teeth 40,41 are adapted, in use, to interfere with the cylindrical side surface of the stem 10 both during the insertion operation of the washer 12 on the same, and after the insertion; in the first case, they force the washer 12 to elastically open in a circumferential direction, to thus allow the teeth 40,41 to overcome the stem 10; in the second case, i.e. with the hole 18 coaxially coupled with the stem 10, they have overcome the stem 10 and thus withhold the washer 12 on the stem 10 on the side of the opening 20 and despite the same; however, during a possible extraction of the washer 12, it will be sufficient to exert on the washer 12 a traction in a radial direction from the opposite side to that provided by the opening 20 to produce a new spreading of the washer 12 by elastic deformation and thus allow the teeth 40,41 to overcome the stem 10 again, this time "backwards", thus releasing the washer 12 from the same.

More in detail, the washer 12 idly engages the mobile stem 10 of the gas tap 2 by means of the collar 30, which cooperates in contact with the cylindrical side surface of the stem 10; and by means of the through hole 18, which idly engages an annular groove 50 of the stem 10 of the tap 2. Furthermore, the hole 18 is made so as to display a diameter smaller (lower) than that of the radially innermost wall of the annular collar 30 and the dimensional ratio thereof is chosen so that the difference between the internal diameter of the collar 30 and the internal diameter of the hole 18 is essentially equal to double the radial depth of the annular groove 50.

The collar 30 is also provided, on the side opposite to the radial opening 20, with a circumferential opening 60 obtained at an upper edge 61 of the collar 30, opposite to the flange portion 15; the opening 60 displays however a width, in a circumferential direction transversal to the hole 18, smaller than the width of the radial opening 20 in the same direction. In this manner, the elastic deformation of the washer 12 is facilitated in the step of assembling/disassembling on/from the stem 10, while maintaining however a certain rigidity of the washer 12 as a whole, which allows to guarantee the reliable mounting of the same on the stem 10, i.e. to ensure that the washer 12, which can be assembled/removed by exerting a relatively low force, cannot be accidentally disengaged from the stem 10.

When the device 1 is assembled, the radial opening 20 is normally arranged oriented in a position diametrically opposite to that of the control rod 11 of the micro switch 7 with respect to the stem 10 of the gas tap, so that, during a normal use, with the tap 2 being open, it is in most cases at 90° with respect to the rod 11, as shown in figure 1.

However, if the rotation of the stem 10 is greater, the opening 20 can never be at the rod 11, because it is prevented, according to the invention, by the presence of the fins 23, for which the washer 12 is forced to slide on the stem 10, idly on the same.

The flange portion 15 is thus always in a condition of abuttingly cooperating against the rod 11 upon an axial displacement movement of the stem 10, by operating the micro switch 7, regardless of the angular position taken by the stem 10. However, the relative sliding motion between the washer 12 and the stem 10 is reduced to a minimum.