EP1608913B1

EP1608913B1 - Plug for connection of a thermocouple to a magnet assembly of a gas valve for gas flow control in a burner

Info

Publication number: EP1608913B1
Application number: EP04721203.0A
Authority: EP
Inventors: Giorgio Offredi
Original assignee: Castfutura SpA
Current assignee: Castfutura SpA
Priority date: 2003-03-31
Filing date: 2004-03-17
Publication date: 2015-12-02
Anticipated expiration: 2024-03-17
Also published as: PL1608913T3; EP1608913A2; EG23725A; EP1608913B8; RU2349839C2; MXPA05010558A; WO2004088205A2; WO2004088205A3; RU2005131200A; BRPI0407881A; ITSV20030013A1

Description

A plugging assembly comprising a thermocouple, a magnet assembly of a gas valve for gas flow control in a burner, a plug for connection of said thermocouple to said magnet assembly, which magnet assembly comprises a first male terminal connected to a magnet assembly conductor and placed within a second tubular cylindrical terminal connected to the ground terminal of the magnet assembly, and which plug comprises an insulating body having an insulating male terminal whose shape is complementary to the inner cavity of the second tubular cylindrical terminal, which insulating male terminal has a hole that coincides with the first male terminal of the magnet assembly and houses in said hole a first female tubular terminal which is designed for engagement on the first male terminal of the magnet assembly, whereas the insulating terminal engages in the second tubular terminal of the magnet assembly, the plug having a second female terminal which is housed in the insulating body and whose aperture is complementary to the external shape of the second tubular terminal of the magnet assembly and which second female terminal of the plug engages on said second tubular ground terminal of the magnet assembly when the first male terminal of the magnet assembly is engaged in the first tubular terminal of the plug, the first tubular terminal of the plug being connected to a conductor that communicates with the hot junction of a thermocouple and the second female terminal of the plug being connected to a conductor that communicates with the cold junction of the thermocouple.
Several types of plugs are known for connection of thermocouples to magnet assemblies of safety gas flow control valves. The thermocouple has the function of sensing the flame and ensuring safe operation of the burner. Hence, there has always been a need for a plug or other means for safe electric connection with the thermocouple. When there is no such connection between the thermocouple and the safety magnet assembly, gas flow to the burner is prevented and the flame extinguishes or the burner cannot be kept on, whereby the burner is no longer operating.
Here, it is highly important, especially for gas-fired household appliances, such as cookers, heating boilers, water heaters, or the like, to have means for safe connection between the thermocouple and the magnet assembly which controls a gas flow control valve.
An example of means for safe electric connection between the thermocouple and the magnet assembly which controls a gas flow control valve is described in the document WO 03/085324 .
The document WO 03/085324 discloses a thermocouple safety device, particularly for gas burners, comprises a phase conductor (3) and an earth conductor (4) of the thermocouple, each carrying a respective terminal (3a, 4a) for electrical connection to an electromagnetic unit (5) for controlling the opening/closure of a valve seat for the supply of the gas to the burner, as well as a tubular body (6) for housing the magnetic unit, from which body a collar-like element (7) extends coaxially along an axial axis (X). The device comprises, at the free end (4a) of the earth conductor (4), a resiliently deformable connection element (11) which can be coupled with the collar-like element, transversely relative to the axial axis, for the restraint of the thermocouple relative to the tubular body of the device. The device further comprises quick push-fit connection means between the terminal (3a) of the phase conductor (3) and the electromagnetic unit (5). The quick push-fit connection means comprises a female connector (9) and a male connector (10) which can engage one another axially, the female and male connectors being electrically connected to the phase conductor (3) of the thermocouple and to a magnet of the electromagnetic unit (5) of the device, respectively.
A number of different solutions have been suggested, but all of them have some drawbacks. Recently, as described in EP 619460 , a plug like the one described hereinbefore has been provided, in which both the first tubular terminal connected to the hot junction of the thermocouple and the second tubular terminal connected to the cold junction of the thermocouple are stably fixed in an insulating body, in corresponding relative positions, complementary to the relative positions of the corresponding terminals of the magnet assembly, and the whole is integrated in the insulating body to form a bipolar plug with substantially coaxial connection terminals. This arrangement has the undeniable advantage of allowing for a one-step connection between the two terminals of the magnet assembly and the two thermocouple conductors.
Nevertheless, coaxial coupling of terminals requires tolerances, especially for the tubular ground terminal, to be set and met with the highest accuracy, otherwise the plug fits hardly, if ever at all, on the terminals of the magnet assembly. Therefore the mutual clamping force between terminals shall not exceed a predetermined limit. It can easily occur that, due to either insufficiently accurate tolerances - these products being non-precision products - or frequent uncoupling and coupling of terminals, coupling is loose and such as to allow an accidental disconnection of terminals, resulting in a loss of functionality of the thermocouple and in the safety problems deriving therefrom. Also, since terminals have to be pushed deeply into the coupling condition to prevent any accidental uncoupling, the terminals of the plug may be deformed or displaced, whereby the contact or coupling with the corresponding terminal of the magnet assembly is partial, loose or insufficient.
A further drawback consists in that, if the magnet assembly terminals and the plug terminals have no matching sizes, said terminals cannot be mutually engaged. In case of dimensional changes, particularly of valves and/or the magnet assemblies thereof, a single type of plug may not be sufficient, therefore several types of plugs shall be provided, having different sizes corresponding to the different size and/or position characteristics of magnet assembly terminals.
Hence, the invention has the object of providing a bipolar plug as described hereinbefore which, by simple and inexpensive arrangements obviates the drawbacks of prior art plugs, while providing a substantially equal functional convenience as well as an enhanced visual check of successful terminal coupling.
The invention fulfils the above objects by providing a plugging assembly comprising a thermocouple, a magnet assembly of a gas valve for gas flow control in a burner, a plug for connection of said thermocouple to said magnet assembly of a gas valve for gas flow control in a burner, which magnet assembly comprises a first male terminal connected to a magnet assembly conductor and placed within a second tubular cylindrical terminal connected to the ground terminal of the magnet assembly, and which plug comprises an insulating body having an insulating male terminal whose shape is complementary to the inner cavity of the second tubular cylindrical terminal of the magnet assembly, which insulating male terminal has a hole that coincides with the first male terminal of the magnet assembly and houses in said hole a first female tubular terminal which is designed for engagement on the first male terminal of the magnet assembly, whereas the insulating terminal engages in the second tubular terminal of the magnet assembly, the plug having a second female terminal which is housed in the insulating body and whose aperture is complementary to the external shape of the second tubular terminal of the magnet assembly and which second female terminal of the plug engages on said second tubular ground terminal of the magnet assembly when the first male terminal of the magnet assembly is engaged in the first tubular terminal of the plug, the first tubular terminal of the plug being connected to a conductor that communicates with the hot junction of a thermocouple and the second female terminal of the plug being connected to a conductor that communicates with the cold electrode of the thermocouple,
wherein
the second female terminal of the plug is shaped like an open cylindrical bushing, with the insulating body of the plug having a lateral opening for radially fitting the second female terminal of the plug onto the second tubular ground terminal of the magnet assembly, which opening extends level with said second tubular terminal of the magnet assembly, when the first female terminal of the insulating body is coupled with the terminals of the magnet assembly.
The second female terminal of the plug is an open-ring straddling member which engages by radial motion on the second tubular terminal of the magnet assembly and the partially open cylindrical surface of the second female terminal of the plug has an angular extension of more than 180°.
The open-ring member is composed of two opposed tabs having the shape of a sector of a cylinder, each having an angular extension of more than 90°.
The second female terminal of the plug has an open-ring member, over a portion of its length, which has an extension of more than 180° and a pair of opposed side tabs over a remaining portion, which are oriented in the direction of coupling of said second female terminal of the plug with the second female terminal of the magnet assembly, which tabs act as guide means and cooperate with corresponding guide notches, formed in the plug body between the corresponding side walls of the plug body and the central cylindrical element.
The guide tabs may be sized or have thicker rib-like portions or non flat shapes, in such a manner as to cause the material of the tabs to be elastically force fitted in the coupling notches of the insulating body.
Advantageously, the second female terminal of the plug and the insulating body have cooperating release preventing means which become operative at an intermediate coupling position of the second female terminal in the notches of the insulating body.
Alternatively thereto or in combination therewith, the second female terminal of the plug and the insulating body have cooperating abutment means for preventing the second female terminal from being fitted in the notches of the insulating body, which become operative at a predetermined intermediate inserted position of the second female terminal in the insulating body, which abutment anti-insertion means may be defeated by exceeding a predetermined pressure in the insertion direction.
According to yet another characteristic of the invention, the predetermined intermediate inserted position of the second female terminal in the insulating body corresponds to a position in which the second female terminal is ready to be coupled on the second cylindrical ground terminal of the magnet assembly, in which ready position the open-ring part of the second female terminal is adjacent to the second cylindrical terminal of the magnet assembly, and engaged on the central cylindrical element of the insulating body, in which position the open-ring part of the second female terminal is slightly spaced from the external surface of the second cylindrical terminal of the magnet assembly.
Hence, as far as construction is concerned, the plug of the present invention may comprise a second female terminal having two pairs of opposed lateral tabs, i.e. two tabs on each side, which pairs of tabs are at a distance from each other and engage in a corresponding notch of the insulating body, i.e. between the side walls of the aperture for insertion of the terminal in the body of the central cylindrical element of the insulating body, whereas the second pair of guide and retention tabs have, at their free ends, release preventing retention means, cooperating with retaining abutments provided at each of the two lateral insertion notches and anti-insertion abutment means cooperating with transverse abutment projections on the central cylindrical element, the release preventing abutment means on the tabs being a tooth which is able to elastically retract from a position in which it abuts against the abutment means into a position in which it does not interfere with said abutment means, which retractable tooth is pushed into the non-interference position by a pressure exceeding a predetermined threshold.
Advantageously, the open-ring terminal and/or the first female terminal of the plug are made of tinned phosphor bronze. This material has steadier elastic properties, when accounting for the constant heating and cooling effects on the terminal, as compared, for instance, with a tinned or non tinned copper terminal. This allows to keep the electric contact characteristics of the connection substantially unchanged with time.
The above construction of the plug according to this invention shows that, in comparison with the prior art coaxial plug, when the plug is fitted on a terminal of the magnet assembly, the plugging force to be exerted is lower, although a perfect electric and mechanical connection is obtained, which is constant with time and resistant to accidental stresses.
The invention further relates to a process for coupling the terminals of a thermocouple with the terminals of a magnet assembly of a gas flow control valve, wherein the thermocouple comprises two terminals to be coupled to two corresponding terminals of the magnet assembly, characterized by the following steps:

Coupling, by axially plugging the insulating body, as well as the first tubular terminal, onto the corresponding pin-like terminal of the magnet assembly,
coupling the second female terminal to the cylindrical terminal of the magnet assembly by a transverse and/or radial displacement thereof toward said terminal of the magnet assembly,
Due to the above, thanks to the second tubular cylindrical terminal of the magnet assembly, the cylindrical shape of said terminal has the function of a lead-in surface for radial expansion of the second ground terminal of the plug.

Also, the axially opened cylindrical surface of the second female terminal of the plug, having an angular extension of more than 180° has an appreciable elastic deformability whereby, within precise size limits, said second female terminal of the plug is highly adaptable to the different sizes of the second terminal of the magnet assembly.
Moreover, the second terminal of the plug has to be manually pressed with a radial movement onto the second terminal of the magnet assembly, and this allows for a tactile and, within certain limits, visual check of the proper engagement between the two second terminals.
Particularly, said release-preventing retention means operate in an intermediate inserted position of the terminal in the insulating body of the plug, which position corresponds to a position in which an open-ring part of the terminal is ready for coupling, in which said open-ring part is directly radially adjacent to the cylindrical terminal of the magnet assembly and axially fitted onto the insulating body of the plug.
The provision of two pairs of guide tabs on each side of the female terminal allows to accurately guide the second female terminal of the plug in its coupling stroke, while preventing the elastic expansion deformation resistance of the ring member, upon coupling thereof with the cylindrical terminal of the magnet assembly, from causing the inclination of the second female terminal of the plug, which may occur when a single pair of guide tabs is provided.
Furthermore, the second pair of tabs, which is designed for interlocking cooperation by their teeth in the guides of the insulating body holds the second female terminal on the insulating body of the plug before coupling thereof to the corresponding second terminal of the magnet assembly, thereby simplifying plug coupling, because otherwise the second terminal would be free and, once the plug has been plugged by its first terminal onto the terminals of the magnet assembly, the second female terminal of the plug would need to be first positioned at the aperture of the insulating body and later radially compressed for plugging. By this arrangement, the second female terminal is already in the proper ready-for-coupling position and, once the plug has been fitted onto the terminals of the magnet assembly, it only needs to be pushed radially inwards to be coupled to the second cylindrical terminal of the magnet assembly.
The advantages of the present invention are self-evident from the above description and consist in simplifying the electric connection of a thermocouple to a magnet assembly of a gas flow control valve, while ensuring an optimal electric connection, even for considerable size tolerances between the terminals of the connection plug, without prejudice to easy fitting of the plug onto the terminals of the magnet assembly.
The above clearly shows that the plug can be coupled to the magnet assembly by only providing a small additional step as compared with the coupling step required in coaxial plugs. Such additional operation is very fast and simple and allows for a tactile and visual check of the actual proper coupling at least of the ground contact.
The invention relates to further improvements, which form the subject of the dependent claims.
The characteristics of the invention and the advantages derived therefrom will appear more clearly from the following description of an embodiment shown in the accompanying drawings, in which:

Fig. 1 is an exploded perspective view of the inventive plug in combination with the terminal-equipped end of the magnet assembly of a gas flow control valve.
Fig. 2 is a perspective view of the plug when fitted and coupled on the terminal-equipped end of the magnet assembly of a gas flow control valve.
Fig. 3 is a perspective view of the mounted plug, with the female terminal, designed for connection to the second cylindrical ground terminal of the magnet assembly of the valve, ready for radial coupling to said terminal of the magnet assembly.
Fig. 4 is a perspective view of the plug as shown in Fig. 3 with the female terminal being pushed into the insulating body of the plug in a position that corresponds to the position in which it is coupled to the ground terminal of the magnet assembly.
Figs. 5 and 6 are cross sectional views of the plug with the female terminal, designed for connection to the second cylindrical ground terminal of the magnet assembly of the gas flow control valve, being ready for displacement to the position in which it is coupled to said cylindrical ground terminal of the magnet assembly and coupled therewith respectively.

Referring to Figure 1, the latter shows the part with the terminals for connection to a magnet assembly of a gas flow control valve, for instance in low-cost cookers or the like.
These terminals generally include a first terminal (not shown), which is connected to the phase terminal of the magnet assembly and is a pin-like element. Coaxial to said first pin-like terminal, a second cylindrical terminal 2 is provided, which is for instance a bushing. A detailed description of the magnet assembly construction is for instance provided in the afore mentioned EP 619460 , whereto reference is made for further information.
A flame control thermocouple, also not shown, is typically connected to the magnet assembly of the valve, which thermocouple is usually composed of two electrodes, i.e. an inner pin-like electrode and an outer cap-like electrode. The two electrodes are mechanically secured together to generate an electrically conductive area in the end portion of the cap. A ground conductor connected to the outer cap and a signal conductor connected to the inner pin-like conductor branch off the two electrodes respectively.
Then, the conductor ends for connection to the two electrodes are connected to a plug 3 which is designed to be coupled to the magnet assembly of the valve. This plug 3 comprises two coupling terminals, i.e. a central terminal 103, which is connected to the inner pin-like electrode, whereas the conductor associated to the outer electrode of the thermocouple is connected to a second open-ring female terminal which is generally designated by 203.
The plug 3 has a body made of an insulating material 303, which includes a central cylindrical element made of an insulating material 403. Said central element 403 is supported in a cantilever fashion by a rear wall 503 of a plug case, which comprises said rear wall, two side walls 603 and a front wall 703 having a central hole 803 wherefrom the free end of the central cylindrical element 403 projects. The central cylindrical element 403 further has a central coaxial hole 903 for engagement with the first terminal 103 connected to the pin-like conductor of the thermocouple. Said terminal has a tubular shape and is equipped with at least one pair of radial tabs or tabs 4 that radially diverge from the outer wall of the terminal 103 toward the rear end for connection to the conductor connected with the pin-like electrode of the thermocouple. The electric connection with said conductor occurs by mechanical fastening of the conductor, at an end 5 that is suitably shaped in a manner known per se. Particularly, said end 5 of the tubular terminal 103 has a wall whose angular extension is of less than 360°, particularly substantially 180°, two pairs of diametrically opposed tabs 6, 6' extending from the two opposite ends thereof, for securing the conductor. Particularly, the end tabs 6' are secured against the end sheathed portion of the conductor, whereas the next tabs 6 are secured on the sheathless end of the conductor.
The radially diverging tabs 4 are designed to cooperate with radial abutment steps or shoulders formed in the central hole 903, behind which steps or shoulders the tabs automatically snap as soon as the tubular terminal 103 is introduced in the hole 903 and reaches the proper axial position relative to said hole. This position is such that the front end of the first terminal 103 is level with the front end of the cylindrical insulating element 403, whereas the opposite conductor fastening end remains inside the hole 903, thereby only leaving the sheathed conductor portion exposed.
The cylindrical insulating element 403 for interlocking engagement of the first tubular terminal 103 connected to the inner pin-like electrode or phase electrode of the thermocouple has an outside diameter that substantially corresponds to the inside diameter of the cylindrical ground terminal 2 of the magnet assembly. Furthermore, this central cylindrical element 403 has a diametrical notch, at least at its end portion, to allow for a certain elastic diameter reducing deformation when the plug is forced onto the terminals of the magnet assembly.
One of the sides of the insulating body 3 of the plug is open and the cylindrical element 403 is wholly accessible from the outside. The diametrically opposed side walls 603 are at a certain distance from the central cylindrical element and form, between said two sides 603 and the cylindrical element, two parallel and diametrically opposed recesses or notches 10. These notches are designed to house the second open-ring or straddling female contact terminal. This terminal 203 has, at its end designed to be turned toward the terminals of the magnet assembly, a pair of tabs 7, having the shape of a sector of a circle which form together an open-ring element. The tabs 7 shaped like sectors of a circle have an angular extension of more than 90°, hence the open-ring element formed thereby has an angular extension of more than 180°. Behind said tabs 7 the terminal 203 has a semi-cylindrical wall, two pairs of flat guide tabs 8 and 9 extending from the diametrically opposed ends thereof. At the terminal end opposed to the open-ring element, means 5 are provided for fastening connection to a conductor connected to the cold or ground electrode of the thermocouple, which are substantially identical or similar to those described for the first terminal 103.
The two pairs of tabs 8, 9 are spaced in the axial direction of the terminal, are oriented perpendicular to the median plane of the insulating body 3 and are designed for engagement in the notches 10 at the two sides of the central cylindrical element 403, which notches extend all along said cylindrical element 403.
Particularly, a first pair of guide tabs 8 has thicker portions 108 adapted to allow the tabs 8 to be elastically force-fitted into the lateral notches, to provide a stable and safe coupling, while allowing the tabs 8 to fit in the side notches by using a predetermined force and the open-ring terminal 203 to be radially deformed outwards to reiterate the coupling step.
On the other hand, the second pair of tabs 9 has elastic means for interlock retention of the open-ring female terminal 203 in a position in which the latter is ready for coupling with the cylindrical terminal 2 of the magnet assembly once the insulating body 3 has been fitted with its central cylindrical portion 403 in the cylindrical terminal 2 of the magnet assembly, and the first terminal 103 in the central hole 903 of said cylindrical body 403 has been forced to engage on the first pin-like terminal of the magnet assembly disposed coaxially inside the cylindrical terminal 2. The ready position is shown in Figures 3 and 5.
The sectional views of Figures 5 and 6 are clearer illustrations of the construction of the second tabs 9, as well as the two positions in which the open-ring terminal 203 is ready for coupling, and in which it is actually coupled to the terminal 2 of the magnet assembly.
At the free ends, the two opposed guide tabs 9 of the second pair have an external tooth 109 which has a saw-tooth profile, with the less steep face oriented in the direction of insertion in the notches 10.
On the inner side which delimits the notches 10, the two side walls 603 of the insulating body 3 have, starting from the end that first receives the guide and retention tabs 9, a first inclined lead-in surface 110 which converges toward the central cylindrical body 403 and along which the ends of the two tabs 9 move, while being slightly elastically forced against each other. At an intermediate location of the depth of the notches 10, such inclined lead-in surface is connected to the remaining inner surface of the corresponding side wall 603 by a step-like widened portion 210, behind which the tooth 109 snaps onto the corresponding guide and retention tab 9. The positions of the teeth 109 and step-like widened portions are defined in such a manner that they engage with each other when the open-ring end to be coupled to the cylindrical terminal 2 of the magnet assembly spaced from said cylindrical terminal 2 fitted on the end of the cylindrical insulating element 403 and more precisely when the ends of the two tabs 7, shaped like sectors of a circle, are at a slight distance from said cylindrical terminal 2 of the magnet assembly.
Such combination of the tooth 109 of the guide and retention tabs 9 and the step 210 of the inner surface of the side wall 603 of the insulating body that outwardly delimits the notches 10 is not sufficient to ensure the stable positioning thereof, as it has the only function or retaining the tabs 9 against release thereof from the notches 10. In fact, as particularly shown in Figures 5 and 6, at a predetermined distance from the teeth 109 the two guide and retention tabs 9 have, on the face opposite the teeth 109 a projection 209 that elastically retracts toward the opposite face of the tabs 9 or away from the opposite tab 9, which projections 209 have the shape of a triangular tooth turned toward the central cylindrical element 403 of the insulating body 403 and come in contact therewith when the teeth 109 engage behind the steps 210.
In accordance with a further advantageous characteristic, level with the guide and retention tabs 9, the central cylindrical element 403 has an annular strip coincident with the elastically retracting projections 209, which is shaped in such a manner as to facilitate retraction or displacement of the projections 209, and to generate an easily defeatable and reversible condition of stable retention of the terminal in the position in which it is coupled with the terminal 2 of the magnet assembly. To this end, in the area in which the central cylindrical element 403 contacts the projections 209, said central cylindrical element 40 has a flattened portion 12, that is inclined toward the end of the tabs 9 in the direction of said tabs 9. Each of said flattened portions extends toward the corresponding tab 9 thereby forming a projection 13 having a predetermined length in the plugging direction which, on the face opposite the inclined surface 12 forms an inclined engagement surface 14. The inclined engagement surface 14 is inclined toward the center of the central element 403 and toward the bottom of the corresponding notch 10, whereby the projection 13 has a trapezoidal section, particularly having the shape of a scalene trapezoid, having its steeper face turned toward the access aperture of the notches 10 and the less steep face turned toward the bottom of the notches 10. The inclination of the surface 14 is lower than that of the opposite surface 12 and allows to retain the tabs 9 in the terminal coupling position, and to easily displace, by exerting a predetermined radial pulling force, the terminal 203 back into the temporary locked position, i.e. the ready position, by allowing the teeth 209 to pass beyond the projection 13 and to be positioned in contact with the inclined surfaces 12.
The remaining portion, coincident with the teeth 209 and provided on the central cylindrical element 403 is a flattened portion 15 which is oriented parallel to the corresponding tab 9 or parallel to the direction of insertion of the tabs 9 in the notches 10 and which flattened portion 15 is recessed with respect to the projection 13 to such an extent that the tooth 209 of the corresponding tab 9 is at a distance from and does not interfere with said flattened portion 15.
The elastically withdrawing tooth 209 of each tab 9 is advantageously made of an appropriately triangularly shaped tongue, which is made of a portion of the tab 9 separated therefrom by cuts on three sides, whereas at the side opposite to the insertion end of the tab, the tongue is still connected to the rest of the tab 9.
Referring to Figures 3 and 5, and 2, 4 and 6, the operation of the plug of the invention is as follows:

Before being coupled with the terminals of the magnet assembly of the gas flow control valve, the plug is as shown in Figures 3 and 5, with the second open-ring female terminal 203 in a position in which it is ready for radial coupling, i.e. not fully inserted in the aperture and in the notches 10 and stably held in said position by the teeth 209 of the tabs 9 which abut against the steps 210 of the outermost wall that delimits the notches 10 and retain the terminal 203 against release thereof and with the teeth 209 abutting by their face turned in the direction of further insertion of the terminal 203 in the notches 10, against the flattened portions 12 of the central cylindrical body 403.

Once the plug has been fitted onto the terminals of the magnet assembly of the valve, i.e. their central pin-like terminal has engaged in the first tubular terminal 103 of the plug and the access end of the central cylindrical portion 403 has simultaneously engaged into the cylindrical ground terminal 2 of the magnet assembly which becomes radially aligned with the open-ring part of the second terminal 203, said second terminal is pushed radially inwards in the direction of further insertion in the insulating body. During such radial displacement, which requires a certain predetermined pressure, the sector-shaped tabs 7 that form the open-ring of the terminal 203 expand and elastically snap to adhere against the outer surface of the cylindrical terminal 2 of the magnet assembly, and further the elastically retractable teeth 203 are deflected outwards by the inclined lead-in surface and pass beyond the corresponding trapezoidal projection 12, further moving along the additional radial coupling path, whereas the tabs 8 are elastically forced into the notches 10 thanks to the thicker portions 108.
Thanks to this arrangement, i.e. to the provision of the elastically retractable teeth 209, the coupling resistance that is generated between the open-ring part and the cylindrical terminal 2 of the magnet assembly is compensated for in the axial direction. This is achieved by providing the teeth 209 with a substantially corresponding coupling resistance. In combination with the tabs 8 this prevents the terminal 203 to be axially inclined upon coupling.
According to a further characteristic, the free ends of the sector-shaped tabs 7 which form the open-ring, which are to be coupled to the cylindrical ground terminal 2 of the magnet assembly may be extended to form lead-in extensions, formed by tabs that are inclined to diverge from the central axis of the open-ring and have a direction substantially corresponding to a tangent to the point whereat they contact the cylindrical ground terminal 2 of the magnet. This facilitates the expansion of the open-ring element during the radial coupling stroke against the cylindrical terminal 2 of the magnet assembly.
The plug may be disengaged from the terminals of the magnet assembly by simply exerting a pulling force in the axial direction of the plug. For a new plugging action, the second terminal 203 shall be brought back into the ready position, by exerting a slight pulling action for disengagement from the notches 10 in the radial direction, which is required to bring back the teeth 109 to the position in which they abut against the steps 210 and to let the elastically retractable teeth 209 pass over the lead-in surface 14, and abut against the corresponding flattened portion 12, as shown in Figure 5.
This return operation is necessary, because an optimal radial force for coupling the open-ring element of the terminal 203 onto the cylindrical terminal 2 of the magnet assembly is assured by radially loading the sector-shaped tabs 7, in the rest position, in such a manner as to form an open-ring whose inside diameter is slightly smaller than the outside diameter of the cylindrical terminal 2 of the magnet assembly. In these conditions, the terminal 203 cannot be held in the coupling position, i.e. fully inserted in the insulating body 3, and a new coupling with the terminals of the magnet assembly may be obtained by a simple axial insertion.
The coupling procedure may seem relatively complex, but the additional step of radially pushing the terminal 203 into the insulating body 3 and of displacing it back into the defined ready position before a new coupling operation is fast and simple and always ensures an optimal electric connection between the terminals of the magnet assembly and the plug.

Claims

A plugging assembly comprising a thermocouple, a magnet assembly of a gas valve for gas flow control in a burner, a plug for connection of said thermocouple to said magnet assembly, which magnet assembly comprises a first male terminal connected to a magnet assembly conductor and placed within a second tubular cylindrical terminal (2) connected to the ground terminal of the magnet assembly, and which plug comprises an insulating body (3) having a central cylindrical element (403) whose shape is complementary to the inner cavity of the second tubular cylindrical terminal (2) of the magnet assembly, which insulating male terminal (403) has a hole (903) that coincides with the first male terminal of the magnet assembly and houses in said hole (903) a first female tubular terminal (103) which is designed for engagement on the first male terminal of the magnet assembly, whereas the insulating terminal (403) engages in the second tubular terminal (2) of the magnet assembly, the plug having a second female terminal (203) having an aperture which is complementary to the external shape of the second tubular terminal of the magnet assembly and which second female terminal (203) of the plug engages on said second tubular ground terminal (2) of the magnet assembly when the first male terminal of the magnet assembly is engaged in the first tubular terminal (103) of the plug, the first tubular terminal (103) of the plug being connected to a conductor that communicates with the hot junction of a thermocouple and the second female terminal (203) of the plug being connected to a conductor that communicates with the cold electrode of the thermocouple,
Characterized in that
the second female terminal (203) of the plug is housed in the insulating body (3) and shaped like an open cylindrical bushing, with the insulating body (3) of the plug having a lateral opening for radially fitting the second female terminal (203) of the plug onto the second tubular ground terminal (2) of the magnet assembly, which opening extends level with said second tubular terminal (2) of the magnet assembly, when the first female terminal (103) of the insulating body (3) is coupled with the terminals of the magnet assembly.
A plugging assembly as claimed in claim 1, characterized in that the second female terminal (203) of the plug is an open-ring straddling member, which engages by radial motion on the second tubular terminal of the magnet assembly.
A plugging assembly as claimed in claim 1 or 2, characterized in that the axially opened cylindrical surface of the second female terminal (203) of the plug has an angular extension of more than 180°.
A plugging assembly as claimed in claim 2, characterized in that the open-ring member is composed of two opposed tabs having the shape of a sector of a cylinder, each having an angular extension of more than 90°.
A plugging assembly as claimed in one or more of the preceding claims, characterized in that the second female terminal (203) of the plug has an open-ring member, over a portion of its length, which has an extension of more than 180° and a pair of opposed side tabs (8) over a remaining portion, which are oriented in the direction of coupling of said second female terminal (203) of the plug with the second female terminal of the magnet assembly (2), which tabs (8) act as guide means and cooperate with corresponding guide notches (10), formed in the plug body (3) between corresponding side walls (603) of the plug body (3) and the central cylindrical element (403).
A plugging assembly as claimed in claim 5, characterized in that the tabs may be sized or have thicker rib-like portions (108) or non flat shapes, in such a manner as to cause the material of the tabs (8) to be elastically force fitted in the coupling notches (10) of the insulating body (3).
A plugging assembly as claimed in claims 5 or 6, characterized in that the second female terminal (203) of the plug and the insulating body (3) have cooperating release preventing means (210, 109) which become operative at an intermediate coupling position of the second female terminal (203) in the notches (10) of the insulating body (3).
A plugging assembly as claimed in any of claims 5 to 7, characterized in that the second female terminal (203) of the plug and the insulating body (3) have cooperating abutment means (209, 12) for preventing the second female terminal (203) from being fitted in the notches (10) of the insulating body, which become operative at a predetermined intermediate inserted position of the second female terminal (203) in the insulating body (3), which abutment anti-insertion means (209, 12) may be defeated by exceeding a predetermined pressure in the insertion direction.
A plugging assembly as claimed in one or more of the preceding claims, characterized in that the second female terminal (203) and the insulating body (3) have both release preventing means (210, 109) and anti-insertion means (209, 12) in combination.
A plugging assembly as claimed in claim 8, characterized in that the predetermined intermediate inserted position of the second female terminal (203) in the insulating body (3) corresponds to a position in which the second female terminal (203) is ready to be coupled on the second cylindrical ground terminal (2) of the magnet assembly, in which ready position the open-ring part of the second female terminal (203) is adjacent to the second cylindrical terminal (2) of the magnet assembly, and engaged on the central cylindrical element (403) of the insulating body (3), in which position the open-ring part of the second female terminal (203) is slightly spaced from the external surface of the second cylindrical terminal (2) of the magnet assembly.
A plugging assembly as claimed in any of claims 5 to 8 or 10, characterized in that the second female terminal (203) of the plug has two pairs of opposed lateral tabs (8, 9), i.e. two tabs (8, 9) on each side, which pairs of tabs are at a distance from each other and engage in a corresponding notch (10) of the insulating body (3), i.e. between the side walls (603) of the aperture for insertion of the terminal (203) in the insulating body (3) and the central cylindrical element (403) of the insulating body (3), whereas the second pair of guide and retention tabs (9) have, at their free ends, release preventing retention means (109), cooperating with retaining abutments (210) provided at each of the two lateral insertion notches (10) and anti-insertion and release preventing abutment means (209) cooperating with transverse abutment means (12, 13, 14) on the central cylindrical element (403), the release preventing and anti-insertion abutment means on the tabs (9) being a tooth (209) which is able to elastically retract from a position in which it abuts against the abutment means (12, 13, 14) into a position in which it does not interfere with said abutment means (12, 13, 14), which retractable tooth is pushed into the non-interference position by a pressure exceeding a predetermined threshold.
A plugging assembly as claimed in claim 11, characterized in that the guide and retention tabs (9) have elastically retractable abutment means (209), which cooperate with abutment surfaces (12, 13, 14) of the central cylindrical element (403) and operate toward delimiting the stroke of insertion of the terminal (203) in the insulating body (3) of the plug, the insertion limiting abutment surfaces (12) and the release preventing abutments (14) of said abutment means (12, 13, 14) , as well as the elastically retractable abutment means (209) and the release preventing means (109) on the tabs (9) being at such a distance from each other that the terminal (203) is locked in position both against release and against insertion, whereas the insertion limiting abutment surfaces (12) form lateral lead-in faces of transverse projections (13) for the tabs (9) that may be surpassed by using a predetermined radial pressure on the terminal (203), sufficient to control the elastically retractable abutment means (209) into a position in which the corresponding transverse projection (13) may be overtaken.
A plugging assembly as claimed in claims 11 or 12, characterized in that each guide and retention tab comprises as release preventing means (109) an end tooth (109) whose abutment face is oriented in the direction of extraction of the terminal (203) from the insulating body (3) and which cooperates with an intermediate inner step (210) facing toward the bottom of the corresponding notch (10) for insertion in the insulating body (3) and, at a distance toward the opposite end, each guide and retention tab (9) has an elastically retractable tooth (209) that cooperates with an inclined abutment surface (12) which is the side face of a transverse abutment projection (13), the distance of the release preventing retention step (210) from the inclined abutment surface (12) corresponding to the distance of the abutment surface of the release preventing retention tooth from the elastically retractable insertion limiting tooth (209) and said teeth (109209) being positioned on the guide tabs (9) in such a position that the terminal (203) is temporarily locked in a position in which it is ready to be coupled on the corresponding terminal (2) of the magnet assembly, and radially adjacent thereto, and may be compressed inwards into the insulating body to a position in which it is coupled on the terminal of the magnet assembly, by exerting a pressure adapted to exceed the predetermined elastic deformation force aimed at bringing it back to a position in which it does not interfere with the insertion limiting projections of the elastically retractable abutment teeth.
A plugging assembly as claimed inclaim 13, characterized in that the release preventing retention step (210) which cooperates with the release preventing tooth (109) on the retaining tab (9) is a step (210) formed in the inner surface of the side wall (603), whereas the inclined abutment surface (12) and the associated anti-insertion abutment projection (13) are provided on the central cylindrical element (403) along a correspondingly shaped portion, that coincides with the elastically retractable anti-insertion abutment tooth (209) of the guide and retention tab (9), the release preventing retention tooth (109) and the elastically retractable anti-insertion abutment tooth (209) projecting out of opposed faces of the guide and retention tabs (9).
A plugging assembly as claimed in claims 13 or 14, characterized in that the release preventing retention step (210) formed on the side wall (603) that delimits the notches (10) has a sawtooth shape, with a first lead-in surface (110) turned toward the access aperture of the notch (10), which is joined to the rest of the wall by a widening step (210) and the cooperating release preventing retention tooth (109) on the guide and retention tab (9) also having a sawtooth profile, with an opposite orientation of the lead-in and retaining abutment faces.
A plugging assembly as claimed in one or more of the preceding claims 11 to 15, characterized in that the anti-insertion retention tooth (209) is formed by a resilient tongue, which projects toward the inner side of the notches (10) for insertion of the guide and retention tabs (9), which tongue is obtained by making cuts and appropriately corner bending of the same wall of the tabs (9), whereas the anti-insertion abutment projection (13) is a transverse projection having a trapezoidal cross section.
A plugging assembly as claimed in claim 16, characterized in that the trapezoidal projection has a scalene shape, with the steeper face turned toward the opening side of the notches (10) and the less steep face turned toward the bottom of the notches (10).
A plugging assembly as claimed in any of claim 11 to 17 characterized in that the transverse abutment means (12, 13, 14) comprises an inclined surface (12), an opposite engagement surface (14) and a projection (13) wherein the inclination of the engagement surface (14) is lower than that of the opposite surface (12) and allows to retain the tabs (9) in the terminal coupling position, and to easily displace, by exerting a predetermined radial pulling force, the terminal (203) back into a temporary locked position, i.e. the ready position, by allowing the teeth (209) to pass beyond the projection (13) and to be positioned in contact with the inclined surfaces (12) while the force required to overtake the anti-insertion abutment of the retractable anti-insertion tooth (209) against the projection (13) is calibrated to be of the same order of magnitude as the force for coupling the open-ring part of the second female terminal (203) on the second cylindrical terminal (2) of the magnet assembly.
A plugging assembly as claimed in one or more of the preceding claims 2,4 and/or 5, characterized in that the open-ring member of the second female terminal (203) of the plug has expansion encouraging means cooperating with the cylindrical surface of the second terminal (2) of the magnet assembly upon radial coupling.
A plugging assembly as claimed in claim 19, characterized in that the open-ring member comprises two cylinder sector branches (7) wherein each of the two cylinder sector branches (7) of the open-ring member may have a radially outwardly inclined end tab, so that the tabs of the two branches form opposed surfaces which diverge toward the free ends.
A process for coupling and uncoupling the terminals of a thermocouple with the terminals of a magnet assembly of a gas flow control valve part of a plugging assembly according to any of the claims 1 to 20, wherein the thermocouple comprises two terminals to be coupled to two corresponding terminals of the magnet assembly, characterized by the following steps:
Coupling, by axially plugging the insulating body (3), as well as the first tubular terminal (103), onto the two corresponding pin-like terminal of the magnet assembly,

coupling the second female terminal (203) to the cylindrical terminal (2) of the magnet assembly by a transverse and/or radial displacement thereof toward said terminal (2) of the magnet assembly.
A process as claimed in claim 21 characterized by providing a plugging assembly according to claim 10 or to any of claims 11 to 18 when linked to claim 10, and characterized in that uncoupling is obtained by coaxially disengaging the plug from the magnet unit terminals, and where in a new coupling requires a return step by outwardly radially pulling the second female terminal (203) into the ready position.