WO2015198211A1

WO2015198211A1 - System and method for fastening detection and/or ignition spark plugs and/or inspection window of boilers or the like

Info

Publication number: WO2015198211A1
Application number: PCT/IB2015/054687
Authority: WO
Inventors: Raoul Bianchi; Gianluigi MANISCALCH; Franco POLVARA
Original assignee: Castfutura S.P.A.
Priority date: 2014-06-26
Filing date: 2015-06-23
Publication date: 2015-12-30
Also published as: EP3161382A1; RU2016150323A3; EP3161382B1; RU2016150323A; RU2676491C2

Abstract

System for fastening ignition spark plugs (2) of boilers or the like, comprising a supporting plate (1), which supporting plate (1) has at least one insertion hole (11) intended for the insertion of a spark plug (2) and/or of an inspection window (6), which spark plug (2) comprises an outer ceramic tubular body (21), inside which a detection and/or ignition rod (22) is housed which projects at least from one head end of said ceramic tubular body (21). Said insertion hole (11) having such dimensions that said spark plug (2), in the inserted condition, forms a gap region between the outer surface of the tubular body (21) of the spark plug (2) and the inner surface of the insertion hole (11), at least in said gap region there being provided means (4) for fastening and sealing said spark plug (2) to said supporting plate (1). Said fastening and sealing means (4) are composed of glass material (4) which is brought in the liquid or semi-liquid phase beforehand such to adhere mechanically and/or by chemical/physical adhesion to the outer surface of said tubular body (21) of the spark plug (2) and to the inner surface of said insertion hole (11) and subsequently it is brought to the solid phase.

Description

Castfutura S.p.A.

SYSTEM AND METHOD FOR FASTENING DETECTION AND/OR IGNITION SPARK PLUGS AND/OR INSPECTION WINDOW OF BOILERS OR THE LIKE

The present invention relates to a system for fastening ignition spark plugs of boilers or the like, comprising a supporting plate that has at least one insertion hole intended for the insertion of a spark plug .

The spark plug comprises an outer ceramic tubular body, inside which a detection and/or ignition rod is housed which projects at least from one head end of the ceramic tubular body.

Moreover the insertion hole has such dimensions that the spark plug, in the inserted condition, forms a gap region between the outer surface of the tubular body of the spark plug and the inner surface of the insertion hole.

Finally at least in said gap region there are provided means for fastening and sealing the spark plug to the supporting plate.

The present invention is mainly intended, but not exclusively, for gas-fired boilers or fuel oil boilers for home heating.

Moreover it is specified that the term "detection and/or ignition rod" means an electrode commonly used in boilers known in the prior art.

Ignition electrodes, ionization detection electrodes, condensate detection electrodes, ignition and detection electrodes, starting electrodes are mentioned among these by way of example.

The known solutions used for fastening ignition spark plugs of boilers or the like provide to bind the ceramic insulating body of the spark plug to a metal plate, particularly into an insertion hole obtained therein, by means of different insulators such as fastening rings, resins of different origin or by riveting the metal part on the ceramic.

For example in the case of fastening rings a typical metal ring is used which is placed between the surface of the ceramic body of the spark plug and the inner surface of the housing hole, which ring is deformed due to a compression, such to adhere both to the surface of the ceramic body of the spark plug and to the inner surface of the insertion hole, and thus such to fasten the spark plug to the metal plate.

Thus a tight sealing is obtained that prevents condensate liquids and/or fumes developing inside the boiler from escaping.

This fastening method has clear drawbacks mainly due to the fact that the exerted mechanical forces can cause the spark plug to move from its operating position or can generate localized pressure peaks that cause the ceramic insulator to be broken.

On the other hand, by providing higher tolerances in order to avoid the risk of breaking, it is possible that the ring, by being deformed, does not perfectly adhere to the walls failing in its sealing function, or in more serious cases not guaranteeing a suitable fastening, namely obtaining a loose fastening when radial compression forces act on the spark plug that are not enough to hold it in place.

All the known mentioned solutions result in additional costs due to the need of dielectric strength tests for the materials being used, pressure tightness tests and tests for the mechanical strength against removal .

In addition to the drawbacks described, the known solutions of the prior art are particularly disadvantageous in presence of complex systems, that is systems providing a support bracket that supports two or three spark plugs and other components, such as for example a flame inspection window.

Such a complex system has different critical points, which are about the fastening of the ceramic body to the support bracket, the fastening of the detection and/or ignition rod to the ceramic body and the fastening of the inspection window to the support bracket .

Currently a complex system, as the one described, is implemented by using different methods and different steps for the assembling, in a particular manner and following a logic order.

Rod/ceramic body fastening: the first operation is the fastening of the rod to the ceramic body by means of different processes depending on the application, the two most used processes are mechanical interference fit or the use of a suitable refractory concrete. These systems hardly meet the needs of the market such as the thrust resistance and torsional strength, but they oblige to use other materials, such as for example hydrophobic concrete for the sealing at PH in the inner end part of the combustion chamber, and silicone in the end outer part of the combustion chamber for guaranteeing the pressure tightness and sealing.

Window/supporting plate fastening: such fastening is mechanically achieved by using a gasket rested on an elastic ring mounted on the window. The whole is inserted in the supporting plate and closed by a screw cover or welded such to guarantee the necessary pressure to the piece. However in many cases a further outer sealing operation is necessary by means of silicone.

Ceramic body/supporting plate fastening: since such fastening has to guarantee an elastic coupling between the ceramic and the plate, which is necessary for accepting the operating tolerances of the materials and such not to damage the ceramic, it is accomplished, as described above, by using a suitable ring made of a yielding material inserted within the hole on the plate. The ceramic body is then inserted inside the ring, by forcing the insertion. The compressions and the expansions of the ring allow the ceramic to match with the plate. Also in this case the parameters required by the market are scarcely satisfied by the application .

As it is clear, a system like the one shown above, in order to be implemented, provides a series of operations that allow the different materials constituting it to be bound while guaranteeing the operation at high temperature (300 °C) , in a highly acid environment (PH<3) and with the presence of high voltage (higher than 10KV) or low signals (currents lower than 5 microA) and with high physical/mechanical properties, such as torsion torque of the rods, thrust torque and low-pressure tightness.

Therefore the operations for accomplishing a complex system of electrodes, on the basis of the known systems of the prior art, are very complicated and require a high accuracy for being carried out, moreover making it necessary to use different materials as binders or sealers for the different interfaces between the components of the system.

The aim of the present invention is to overcome the drawbacks mentioned above.

The present invention achieves the above aims by providing a system for fastening ignition spark plugs of boilers or the like such as described above, wherein the fastening and sealing means are composed of a glass material which is brought in the liquid or semi-liquid phase beforehand such to adhere mechanically and/or by chemical/physical adhesion to the outer surface of the tubular body of the spark plug and to the inner surface of the insertion hole and subsequently it is brought to the solid phase.

The use of a glass material as a binding and sealing material allows the probability of breaking the insulator to be reduced to negligible levels, such as for example the fastening ring, both in the assembling step and in the operating step of the boiler.

Moreover a higher mechanical strength is guaranteed with respect to the known solutions, and the problems deriving from ovalization both of the insertion hole and of the insulators are eliminated, and problems deriving also from excessive tolerances on the diameter are eliminated which can compromise the mechanical strength and the pressure tightness.

All such advantages allow operations, time and costs to be saved both by preventing elements from being structurally broken and therefore requiring less maintenance, both by drastically reducing the need of testing steps such as for the dielectric strength, the mechanical sealing and the pressure tightness.

Although generally three different materials (metal for the plate, ceramic of the spark plug and glass or the like for the fastening and sealing material) are subjected to heating and cooling steps alternate with each other, therefore one may think that the different coefficients of thermal expansion and of shrinkage may cause a progressive decline both of the mechanical sealing and of the mechanical locking (due to the separation of the contact surfaces of said three materials) , on the contrary surprisingly it has been found that experimentally the connection between metal glass ceramic remains stable and therefore both mechanical sealing and locking are maintained.

Moreover the most important functional components, such as thrust resistance, torsional torque, sealing and pressure tightness are enhanced by one order of magnitude with respect to what can be obtained by the current components and the current assembling techniques .

Finally as it will be clear from the method of the present invention, it provides not only to use only one material, but the steps for obtaining the finished product are made more rapid and also more simple.

According to a first embodiment, the ceramic tubular body has a housing hole for housing the detection and/or ignition rod.

In this case the fastening means are also provided between the outer surface of the rod and the inner walls of the housing hole.

Thus also the rod/ceramic body interface has the advantages of using a glass material described above with reference to the ceramic body/supporting plate interface .

Moreover thus it is possible to insert the rod inside the body and to insert the body inside the supporting plate, to place the glass material at the two interfaces and by only one pass in oven, for heating the glass material up to the melting temperature, the finished product is obtained.

Preferably the pass in the oven for melting the glass is only one, but it is possible to provide two or more passes on the basis of the constructional needs of the system and on the basis of the thermal properties of the glass being used.

The glass material employed may be provided in several forms, such as for example:

- a glass solid such as a glass ring,

- a mixture obtained with glass in microgranules and a suitable diluent and placed in position by means of a pneumatic dispenser,

- a disc of sintered glass.

Moreover a combination of such forms is possible, as well as a whole of different technologies and different types of glass are possible depending on the desired performances.

As anticipated, the invention relates also to complex systems, that provide the use of different components fastened to the supporting plate.

Therefore according to a further variant embodiment, the supporting plate has at least one further insertion hole intended for the insertion of an inspection window, the fastening means being provided between the outer surface of the inspection window and the inner surface of the further insertion hole.

Also such arrangement has the advantages of the use of the glass material mentioned above, as well as the advantages related to the execution speed for obtaining the finished product.

According to a preferred embodiment, the insertion hole has greater dimensions at the upper surface of the supporting plate and smaller dimensions at the lower surface of the supporting plate, such to form at the lower surface abutment surfaces for the abutment of corresponding abutment elements provided on the component to be inserted, both the electrode and the inspection window.

With a particular reference to the ignition and/or detection spark plug such abutment elements will be provided on said ceramic tubular body.

The presence of the abutment surfaces, as it will be clear from the annexed shown embodiments, prevents the glass material from leaking in the liquid phase.

Preferably the abutment elements are composed of a radial enlargement of the tubular body.

The abutment elements are therefore made as one piece with the tubular body and such characteristic is particularly advantageous as regards the automation of the fastening process, since the precise positioning of the tubular body within the insertion hole is made easier by the presence of the abutment elements.

The same advantages about the leakage of the glass material and about the positioning of the components, may be obtained also with reference to the rod/ceramic body interface.

According to a further embodiment the housing hole at the upper head side of the tubular body has a conical and/or cylindrical section tapered downwardly in the direction opposite to the head side, such to form abutment surfaces for the abutment of corresponding abutment elements provided on the detection and/or ignition rod.

As anticipated the glass material can be composed of a combination of different glass mixtures and/or of a combination of glass materials having different characteristics. For example the glass material can be composed of a combination of glass materials having a different melting temperature.

The use of glass materials with a different melting temperature improves mechanical sealing properties between a different component and another one .

Moreover it is possible to provide to diversify the type of used glass material for the type of component to be fastened in the complex system described above.

Therefore for example it is possible to provide a glass material for the fastening of the inspection window different than that used for fastening the tubular body of the spark plug, depending on constructional needs.

Due to the advantageous characteristics in using the glass material described above, the present invention relates also to a method for fastening ignition spark plugs of boilers or the like.

The method of the present invention provides to insert a spark plug into an insertion hole provided in a supporting plate, which spark plug comprises an outer ceramic tubular body, inside which a detection and/or ignition rod is housed which projects at least from one head end of the ceramic tubular body.

The insertion hole has such dimensions to form a gap region with predetermined dimensions between the outer surface of the ceramic tubular body of the spark plug and the inner surface of the insertion hole when the spark plug is inserted into the hole.

In the gap region there are further provided means for fastening and sealing the spark plug to said supporting plate.

The fastening and sealing means are composed of a glass material the method providing the following steps :

a) positioning the glass material in the solid phase at said gap region

b) heating the glass material at such a temperature equal to the melting temperature thereof, such that the glass material, once in the liquid or semiliquid phase, adheres mechanically and/or by a chemical/physical adhesion to the outer surface of said ceramic tubular body of the spark plug and to the inner surface of the insertion hole,

c) passing the glass material to the solid phase for the fastening of the spark plug to the supporting plate and relevant sealing.

As mentioned above the method of the present invention allows the product to be made even by only one pass in the oven, namely it is necessary only to insert the tubular body in the insertion hole, to position the glass material at the gap region and to heat the glass material .

Finally according to a possible embodiment of the method of the present invention, the ceramic tubular body has a housing hole for housing the ignition and/or detection rod, the glass material being placed at the upper head side of said ceramic tubular body. These and other characteristics and advantages of the present invention will be more clear from the following description of some embodiments shown in the annexed drawings wherein:

Figs la and lb are two perspective views of a variant embodiment of the fastening system of the present invention;

Fig.2 is a section of the spark plug belonging to the fastening system of the present invention;

Fig.3 is the section of a detail of the spark plug belonging to the fastening system of the present invention ;

Fig.4 is a possible embodiment of the fastening means ;

Fig.5 is a possible embodiment of the inspection window belonging to the system of the present invention .

It is specified that in the figures described below some possible embodiments of the system of the present invention are shown, but such embodiments have to be intended merely for illustrative purposes and for better understanding the claimed characteristics.

Therefore such embodiments have not to be intended as a limitation of the inventive concept of the present invention, that provides to use a glass material for fastening the ceramic tubular body inside an insertion hole obtained in a supporting plate.

With particular reference to figures la to 2, the system for fastening ignition spark plugs of boilers or the like, comprises a supporting plate 1, that has at least one insertion hole 11 intended for the insertion of a spark plug 2, that comprises an outer ceramic tubular body 21, inside which a detection and/or ignition rod 22 is housed which projects at least from one head end of the ceramic tubular body 21.

The insertion hole 11 has such dimensions that the spark plug 2, in the inserted condition, forms a gap region between the outer surface of the tubular body 21 of the spark plug 2 and the inner surface of the insertion hole 11.

At least in said gap region there are provided means 4 for fastening and sealing the spark plug 2 to the supporting plate 1.

The fastening and sealing means 4 are composed of glass material which is brought in the liquid or semi- liquid phase beforehand such to adhere mechanically and/or by chemical/physical adhesion to the outer surface of the tubular body 21 of the spark plug 2 and to the inner surface of the insertion hole 11 and subsequently it is brought to the solid phase.

Therefore the glass material 4 is placed at the upper aperture of the insertion hole 11, it is heated up to the melting temperature, it becomes liquid and it pours into the gap region, such as shown in figure 2.

Advantageously such as shown in figure 2, the insertion hole 11 has greater dimensions at the upper surface of the supporting plate 1 and smaller dimensions at the lower surface of the supporting plate 1, such to form at the lower surface abutment surfaces for the abutment of corresponding abutment elements provided on the ceramic tubular body 21.

Preferably the abutment elements are composed of a radial enlargement 211 of the tubular body 21.

Once the spark plug 2 is inserted within the insertion hole 11, the radial enlargement 211 abuts against the bottom wall 111 of the insertion hole.

From figure 2 it is clear how the presence of the radial enlargement 211 not only allows the tubular body 21 to be firmly fastened in place, but it also prevents the glass material in the liquid phase from escaping outside the gap region.

Preferably the ceramic tubular body 21 has a housing hole 23 for housing the detection and/or ignition rod 22.

Such as shown in figure 3, the fastening means, composed of glass material, are provided between the outer surface of the rod 22 and the inner walls of the housing hole 23.

Particularly in figure 3 the glass material 4 is placed in the solid phase above the housing hole 23.

Such as described above, the glass material 4 is heated up to the melting temperature and it pours into the housing hole 23 for fastening the rod 22 inside the tubular body 21.

Still with reference to figure 3, the housing hole

23 at the upper head side 212 of the tubular body 21 has a conical and/or cylindrical section tapered downwardly in the direction opposite to the head side 212, such to form abutment surfaces 231 for the abutment of corresponding abutment elements 221 provided on the detection and/or ignition rod 22.

As described above for the ceramic tubular body 21 also in this case the abutment elements 221, once the rod 22 is inserted within the housing hole 23, abut against the bottom wall 231 of the housing hole 23 and they keep the rod 22 in place and prevent the glass material 4 from escaping under the bottom wall 231 of the hole 23.

Moreover the embodiment shown in figure 3, is particularly advantageous if provided in combination with the variant embodiment providing the glass material 4 to be composed of a glass ring 41, such as shown in figure 4.

In the solid phase the glass ring 41 may be placed around the rod 22 and the ceramic tubular body 21, after inserting the system within a oven for reaching the melting temperature of the glass and by only one pass in the oven and after subsequently cooling it the finished product is obtained.

Advantageously the ring 41 can be made of coloured glass, such to immediately recognize it.

Moreover the glass material may be made of a combination of glass materials having different melting temperatures .

As mentioned above, the present invention mainly relates to complex systems, that is systems providing a supporting plate having more than one insertion hole 11 intended for the insertion of different components.

Figures la and lb show two views of such complex systems, composed of a supporting plate 1, two ignition electrodes 2 and 7, an ionization electrode 5 and an inspection window 6, however there are provided applications having only one of such parts or more electrodes with specific functions.

Obviously in order to implement such a system the supporting plate must have an insertion hole for each component, therefore it has an insertion hole 11 for each spark plug or electrode and a further insertion hole intended for the insertion of the inspection window 6, said fastening means 4 being provided between the outer surface of the inspection window 6 and the inner surface of the further insertion hole.

Figure 5 shows the fastening of the inspection window 6, placed inside the insertion hole, the fastening means 4 made of glass material are placed between the lower surface of the inspection window 6 and the bottom wall 12 of the insertion hole obtained in the supporting plate 1.

Obviously the inspection window will be composed of a material that has a melting point at a temperature higher than the melting point of the glass material 4.

In the end as it results from the figures and the previous description, the system of the present invention provides, by suitably designing the components and by using the glass material as the binder, to assemble even only with a single operation the whole system, considerably simplifying both the number of operations and their complexity and therefore the cost thereof.

From what described above it is possible to find three interface regions that allow fastening one component to another one by using glass material .

1) Ceramic body 21/supporting plate 1 (figure 2) : this is the locking system sealed and resistant to pressure, thrust and torsion, that allows the outside of the ceramic body 21 to be coupled to the supporting plate 1.

Preferably the fastening is accomplished by using the glass ring 41 and by suitably shaping the insertion hole 11 of the plate 1 by creating a drawn part, such that the lower hole is always smaller than the upper one. The ceramic is modified by obtaining an outer ring 211 with a diameter smaller than the upper hole of the drawn part and greater than the inner hole thereof.

The ceramic body 21 is placed inside the drawn part resting on it, now a glass ring 41 is inserted. Then the system is inserted into an oven with a temperature higher than the softening temperature of the glass ring 41, the glass by being melted will take all the empty spaces inside the drawn part without pouring by means of the superimposition of the ceramic ring 211 directly obtained from the ceramic on the drawing material present on the plane of the lower hole. Now by cooling the oven, the glass goes back to its crystalline phase perfectly mechanically sealing the ceramics to the supporting plate 1 resisting to pressure at very acid PHs .

2) Inspection window 6/supporting plate 1 (figure 5) : this is the locking sealed and resistant to the pressure and thrust that allows the inspection window 6 to be coupled and fastened to the supporting plate 1. The working environment has to be provided with a PH lower than 3.

Even in this case the sealing it obtained by creating a drawn part similar to the previous one namely with the desired depth and with a hole in the upper part greater than the hole present in the lower part thereof. On the bottom of the drawn part there is placed a glass ring 4 and above it the inspection window 6 is placed, made of a glass with a melting temperature higher than that of the sealing ring 4.

The piece assembled in this manner is placed in the oven at a proper temperature, the glass 4 will melt filling the spaces and sealing, by the subsequent cooling, the glass 6 to the plate 1. The melting operation in the oven is common to that of the interface between ceramic body 21/plate 1 described above .

3) Rod 22/ceramic body 21 (figure 3) : this is the locking system sealed and resistant to pressure, resistant to thrust and resistant to torsion of the metal rod 22 placed inside the ceramic 21 to the ceramic itself. The working environment has to be provided with a PH lower than 3.

Even in this case the mechanical coupling and sealing between the ceramic body 21 and the rod 22 is accomplished by means of a "drawn part" 23, slot or recess, obtained into the ceramic body 21 and with the diameter of the hole inside it on the supper part being greater than that of the lower part and by means of a swelling 221 obtained by a cold pressure method or other known methods on the rod 22.

In this case the swelling allows the abutment elements 221 to be made.

The rod 22 now is placed within the ceramic body

21, the swelling or the like 221 thereof resting on the sides of the lower hole in the slot 23 present on the ceramic will be positioned while guaranteeing stability and mechanical accuracy. A glass ring 41 will be placed on the rod 22. The semi finished product obtained in this manner will be placed in the oven at a temperature equal to the melting temperature of the glass 41. The glass 41 by being melted will fill the empty spaces in the slot 23, by the subsequent cooling the glass 41 will become again crystalline guaranteeing the mechanical strength, the resistance to pressure, to a very acid environment and to the torsion of the rod 22 with respect to the ceramic body 21.

Even in this case the operation in the oven will be preferably only one performed contemporaneously with the other ones. Moreover the superimposition between the frame surrounding the lower hole of the slot 23 and the swelling 221 of the rod 22 together with the proper glass ring 41 will completely prevent the glass from leaking into the through hole present on the ceramic and where the rod 22 is inserted.

Finally generally speaking it is important to note that the dimensions and the shapes of the insertion holes 11 and of the housing holes 23 may also be different from the ones described above depending on particular drawbacks to be solved. It is important that the holes 11 and 23 are present and that the diameter of the hole in the upper part is greater than that present in the lower part.

Even the shape of the glass ring 41 may change depending on the dimensions and types of the holes 11 and 23.

Claims

1. System for fastening ignition spark plugs (2) of boilers or the like, comprising a supporting plate (1) , which supporting plate (1) has at least one insertion hole (11) intended for the insertion of a spark plug (2) and/or of an inspection window (6) , which spark plug (2) comprises an outer ceramic tubular body (21) , inside which a detection and/or ignition rod (22) is housed which projects at least from one head end of said ceramic tubular body (21) ,

said insertion hole (11) having such dimensions that said spark plug (2) , in the inserted condition, forms a gap region between the outer surface of the tubular body (21) of the spark plug (2) and the inner surface of the insertion hole (11) ,

at least in said gap region there being provided means (4) for fastening and sealing said spark plug (2) to said supporting plate (1) ,

characterized in that

said fastening and sealing means (4) are composed of glass material (4) which is brought in the liquid or semi-liquid phase beforehand such to adhere mechanically and/or by chemical/physical adhesion to the outer surface of said tubular body (21) of the spark plug (2) and to the inner surface of said insertion hole (11) and subsequently it is brought to the solid phase.

2. System according to claim 1, wherein said ceramic tubular body (21) has a housing hole (23) for housing said detection and/or ignition rod (22) , said fastening means (4) being provided between the outer surface of said rod (22) and the inner walls of said housing hole (23) .

3. System according to claim 1, wherein said supporting plate (1) has at least one further insertion hole (11) intended for the insertion of an inspection window (6) , said fastening means being provided between the outer surface of said inspection window (6) and the inner surface of said further insertion hole (11) .

4. System according to claim 1, wherein said insertion hole (11) has greater dimensions at the upper surface of said supporting plate (1) and smaller dimensions at the lower surface of said supporting plate (1) , such to form abutment surfaces (111) at the lower surface for the abutment of corresponding abutment elements (211) provided on said ceramic tubular body (21) .

5. System according to claim 4, wherein said abutment elements are composed of a radial enlargement

(211) of said tubular body (21) .

6. System according to claim 2, wherein at the upper head side (212) of the tubular body (21) said housing hole (23) has a conical and/or cylindrical section tapered downwardly in the direction opposite to said head side (212) , such to form abutment surfaces for the abutment of corresponding abutment elements (221) provided on said detection and/or ignition rod (22) .

7. System according to claim 1, wherein said glass material (4) is composed of a combination of different glass mixtures and/or a combination of glass materials having different properties.

8. Method for fastening ignition spark plugs of boilers or the like, which method provides to insert a spark plug (2) into an insertion hole (11) provided in a supporting plate (1) , which spark plug (2) comprises an outer ceramic tubular body (21) , inside which a detection and/or ignition rod (22) is housed which projects at least from one head end of said ceramic tubular body (21) ,

the insertion hole (11) having such dimensions to form a gap region with predetermined dimensions between the outer surface of said ceramic tubular body (21) of the spark plug (2) and the inner surface of said insertion hole (11) when the spark plug is inserted into said hole (11) ,

in said gap region there being provided means (4) for fastening and sealing the spark plug (2) to said supporting plate (1)

characterized in that

said fastening and sealing means are composed of glass material the method providing the following steps :

a) positioning the glass material (4) in the solid phase at said gap region

b) heating the glass material (4) at such a temperature equal to the melting temperature thereof, such that said glass material (4) , once in the liquid or semiliquid phase, adheres mechanically and/or by a chemical/physical adhesion to the outer surface of said ceramic tubular body (21) of the spark plug (2) and to the inner surface of said insertion hole (11) ,

c) passing said glass material (4) to the solid phase for the fastening of the spark plug to said supporting plate (1) and relevant sealing.

9. Method according to claim 8 , wherein said ceramic tubular body (21) has a housing hole (23) for housing said detection and/or ignition rod (22) ,

said glass material (4) being placed at the upper head side (212) of said ceramic tubular body (21) .