Technological background Thermocouple devices of the type indicated are used widely for controlling the flow of gas in burners of domestic heating boilers, of cooking hobs, of gas ovens in general, and all similar apparatus. Apparatus of this type generally has a gas-supply valve the opening/closure of which is controlled by an electromagnetic unit which is connected to a thermocouple for ensuring safety shutting-off of the valve if the flame in the burner should accidentally go out.

Typically, the potential difference generated by the thermocouple as a result of contact with the flame serves to keep the closure member of the valve in the open position by electromagnetic attraction and in opposition to a biasing force, generally of a resilient nature, for ensuring the safety closure of the closure member in the absence of a flame.

It is known to mount the contact terminals of the thermocouple, which are normally constituted by a phase conductor and an earth conductor, on a body of the valve unit, by connection with threaded connectors. This system has been found particularly inconvenient since it requires the use of tools for mounting/removal operations; moreover, it may be unreliable owing to possible slackening of the threaded connections.

It is also known to mount the contact terminals by means of quick push-fit connectors both for the phase conductor and for the earth conductor. An example of a device having these characteristics is known from European patent No. 619460. This describes the mounting of the thermocouple by the provision of a pair of axial push-fit connector elements on the body of the valve unit and a corresponding pair of push-fit connector elements on the thermocouple terminals for making a connection by the quick axial push-fit connection of the phase and earth conductors to the valve body.

Description of the invention A principal object of the invention is to improve the tightness of the connection between the terminal and the valve unit, in particular insuring improved axial locking of the thermocouple terminals relative to the valve unit with respect to possible slipping-off of the conductors, but at the same time to ensure that operations to mount and remove the thermocouple are very quick.

This and other objects which will become clear from the following description are achieved by the invention by means of a thermocouple safety device formed in accordance with the appended claims.

Brief description of the drawings The characteristics and the advantages of the invention will become clearer from the following detailed description of a preferred embodiment thereof which is described by way of non-limiting example with reference to the appended drawings, in which: Figure 1 is a partial, exploded, perspective view of a thermocouple safety device according to the invention, Figure 2 is a partial axial section through the device of Figure 1, in the assembled condition, Figure 3 is a partial section taken on the line III-III of Figure 2, Figure 4 is a partially-sectioned side elevational view of the device of the preceding drawings, Figure 5 is a partial axial section through a variant of the device according to the invention.

Preferred embodiment of the invention With reference to the drawings mentioned, a safety device according to the invention, with a thermocouple 2, for a gas burner (not shown), is generally indicated 1.

The thermocouple 2 of the device comprises a phase conductor 3 and an earth conductor 4 each carrying, at a corresponding end, a respective terminal 3a, 4a for electrical connection to an electromagnetic unit 5, shown schematically in Figure 2.

The electromagnetic unit 5 is housed in a tubular body 6 of the device in which a gas-supply valve seat (not shown) is formed in conventional manner; the valve seat is associated with a respective closure member, also not shown, the opening/closure of which are controlled by the magnet of the unit 5 in a conventional manner which is not a subject of the present invention.

A collar-like element 7 extends coaxially from the tubular body 6 along an axial axis X and is advantageously connected to an axial end of the body 6 by means of a threaded connector.

The collar-like element 7 can house in its interior a head 8 made of insulating material and formed with two main portions 8a, 8b having cylindrical surfaces and extending axially as extensions of one another. The head 8 is also hollow axially in order to receive in its interior a female quick push-fit connector 9 which is mechanically and electrically connected to the terminal 3a of the phase conductor 3. This connector 9 can be push-fitted axially onto a corresponding male connector 10 projecting coaxially from the body 6 in the axial cavity of the collar-like element 7, and electrically connected to the electromagnetic unit.

The earth conductor 4 is connected, at its terminal 4a, to a connection element, generally indicated 11, which is resiliently deformable and can be coupled with the collar-like element 7, as will become clear from the following description.

The connection element 11 is advantageously configured as a resilient clip including a pair of opposed arms 12,13 which can be opened out resiliently and are connected by a plate-shaped connecting region 14.

The arms 12,13 extend for a distance such that they clasp diametrally- opposed portions of the outer surface of the collar 7 as a result of a movement of the clip transversely relative to the axis X in the direction of the arrow F of Figure 1.

More particularly, each arm 12,13 of the clip is bent to form at least one respective portion 12a, 13a having an arcuate profile corresponding to the circumferential profile of the collar 7 (having the same radius of curvature) so that, during the fitting-together, the arms of the clip are opened out resiliently and the portions 12a, 13a are then engaged on the respective portions of the collar 7 by a snap-fitting of the clip on the collar such as to ensure that the clip is restrained relative to the body 6 both in both transverse and axial directions. It should be noted that, in this case, the axial restraint (along the axis X) is due principally to the surface-frictional forces between the arms 12, 13 and the outer surface of the collar 7 which are generated by the resilient deformation of the clip during its snap-fitting. It should also be noted that the arms 12,13 are shaped so as substantially to fit the shape of the collar 7, thus maximizing the mutual contact area, for a greater mutual restraining action between the parts that are fitted together.

The clip-like connection element 11 and the collar-like element 7 are advantageously made of electrically-conductive material so as to ensure the electrical connection of the earth conductor 4 to the electromagnetic unit 5.

In order to improve the axial locking of the thermocouple 2 relative to the body 6 of the device, auxiliary axial restraint means are also additionally and optionally provided. These means comprise a projection 15 produced by the right-angle bending of an end of the plate-shaped region 14 of the clip, which can engage a circumferential groove 16 defined in the collar 7 when the clip 11 is snap-fitted on the collar. The groove 16 is preferably defined by opposed and facing shoulder surfaces 17,18 extending from the collar-like element 7 and from the tubular body 6, respectively. The projection 15 has a circular recess 15a suitable for mating with the cylindrical surface of the base of the groove 16, for improved mutual bearing contact.

The clip 11 may also comprise a second projection 19, also preferably produced by the right-angle bending of the connecting region 14, at the side remote from the projection 15 and in the same direction as the projection 15.

It should be noted that the projection 19 has a circular recess 19a of similar shape to the recess 15a, suitable for permitting improved bearing of the projection on the outer surface of the head 8, close to a shoulder 8c thereof, so as to interfere with this shoulder during axial sliding of the head away from the body 6, for example, due to accidental slipping-out of the phase conductor.

The projection 19 is advantageously used for connecting the terminal 4a of the earth conductor 4 to the clip 11 mechanically (for example, by soldering) and electrically.

In a variant, shown in Figure 5, the head 8 is produced by a vulcanization process which also produces a circumferential groove 20 capable of mutual engagement with the projection 19, for a bidirectional axial restraining action on the head 8 when the clip 11 is snap-fitted on the collar-like element 7.

In operation, the mounting of the thermocouple involves, initially, the connection of the phase conductor 3 by the axial quick push-fit connection of the connectors 9,10 and, subsequently, snap-fitting of the clip 11 by movement perpendicular to the axial direction in the direction of the arrow F of Figure 1; this fitting ensures the axial restraint of both of the terminals of the conductors 3,4 of the thermocouple relative to the tubular body 6 as well as ensuring the electrical connection of the earth conductor 4.

Conversely, to disconnect the thermocouple 2, it is necessary to remove the resilient clip 11 from the collar-like element 7 preliminarily (so as to disengage the earth conductor 4) and then to disengage the quick push-fit connection of the phase wire 3 axially.

The invention thus achieves the objects proposed, affording many advantages over known solutions.

Amongst these should be included improved axial locking of the thermocouple which is brought about independently of the quick push-fit connection of the phase wire. One of the main advantages is that quick and easy connection of the thermocouple is ensured with a limited overall transverse dimension of the device.