The subject matter of the present invention is a door assembly for a premixed burner boiler according to the preamble of the main claim.

It is known that a usual boiler for heating rooms and producing sanitary water includes, in an outer case thereof, an opening through which a gas burner is inserted into the boiler during assembling (or maintenance) operations. Such burner is associated with a closing element to close such opening of the boiler case, said closing element being commonly referred to as a "door" of the boiler.

The burner is associated with a first face of such door suitable for facing the inside of the case of the boiler. In order to prevent the second face of such door, external to the boiler, from overheating during the operation of the burner, an insulating element is arranged on the first face. Specifically, such first face has an annular shape whose central bore is connected to an admission duct carrying a mix of air and gas towards the burner arranged in correspondence with said bore. Around said bore and on said first face there is placed the insulating material (together with a usual electrode for burner ignition) .

Presently, depending on the insulating element, different modes are known for its binding to the door of the boiler. In the case of "fibrous" insulating elements, they are glued or mechanically fixed to the door. In the case that this element be made from vermiculite, it is fixed by way of screws to said door, said screw cooperating with a widened element generating a pressure locally distributed on the insulating element so as to press it onto the door. The screw fixes it to the latter.

The known screw binding solutions require relatively long and complex fixing operations. Furthermore, the presence of screws and pressing elements acting onto the insulating element might create structural tensions therein which, over time, lead to a cracking of the insulating element, with a consequent loss of effectiveness of the latter and possible detachments thereof from the door of the boiler.

An object of the present invention is to offer a door assembly for boilers that is improved with respect to the known door assemblies. Let's point out that by "door assembly" we mean a set or assembly comprising at least the door of the boiler (as indicated above), an insulating element associated therewith, a burner, and accessories (including inspection glasses, and ignition and flame detection electrodes) as usually present in such an assembly of a boiler.

Another object is to offer a door assembly of the type indicated above that can be assembled quickly and simply.

A further object is to offer a door assembly of the mentioned type that retains its effectiveness unchanged for a very long time.

These objects and others that will be apparent to those skilled in the art are achieved by a door assembly according to the attached claims.

For a better understanding of the present invention, the following drawings are attached for merely explanatory, but not limitative, purposes, wherein:

figure 1 shows an exploded perspective view of an embodiment of the present invention;

figure 2 shows a transparent perspective view of the invention shown in figure 1 ;

figure 3 shows a cross-sectional view according to the trace 3-3 in figure 2 ;

figure 4 shows an enlarged view of the part identified by the letter A in figure 2 ;

figure 5 shows an enlarged front view of a detail of the invention as shown in the preceding figures;

figure 6 shows a rear view of the detail shown in figure 5; and

figure 7 shows an exploded view of the detail shown in figure 5.

With reference to the mentioned figures, a door assembly for a boiler, in particular a premixed burner one (i.e. one operating on a predetermined air/gas mix), is generically identified by the reference numeral 1 and comprises the true door 2 of the boiler, an insulating element 3 associated with such door 2, and a burner (not shown) . The door 2 comprises a (substantially flat) body 5 which a duct 6 is associated with for feeding an air/gas mix to the burner; such duct 6 is associated with the door 2 so as to open in correspondence with a bore 7 provided in a first face 8 of such door suitable for facing the inside of a boiler for heating a room and for producing sanitary water which the assembly 1 is associated with. The burner is associated with such face 8.

The duct 6 is bound to a second face 11 of the door 2 suitable for being placed outside said boiler. Such door is fixed by means of screws (not shown) to a case of the boiler and encloses an opening thereof. The screws are suitable for co-operating with perforated fins 10 of the body 5 of the door 1.

The first face 8 of the body 5 of such door consequently has an annular shape and is arranged around the bore 7. Such face 8 includes a raised outer edge 14 and a raised inner edge 12, placed at a short distance from the outer edge 14. In correspondence with such inner edge 12, in positions diametrically opposed to each other, there are present two projections 15 each provided with a threaded hole 15A. Such hole is located between two reliefs 16 and 17 having an axis W perpendicular to the edge 12 and suitable for operating as guides and a lock (in a plane transversal to said axis W) for a base 20 of a corresponding locking element 21 suitable for co-operating with the insulating element 3 in turn suitable for being placed on the face 8 of the body 5, between the bore 7 and the above mentioned inner edge 12. Such insulating element 3 is ring-shaped and presents a central bore 25 suitable for being arranged above the bore 7.

More specifically, every locking element 21 is a substantially L-shaped "clip" with a base 20 and a wall 26 raising from such base and having a free end 27 folded back. Such clip element 21 presents the base 20 having two parallel arms 28 and 29 delimiting a slit 30, open at the ends 31 of such base; such arms 28 and 29 are suitable for being arranged on their corresponding projection 15 on the sides of the reliefs 16 and 17. Said arms are suitable for co-operating with a head 39 of a screw 32 inserted into the hole 15A of every corresponding projection 15, said head holding the base 20 of the (elastically deformable) element or clip 21 fixed onto its respective projection.

The wall 26 of the element or clip 21 raises from its corresponding projection and folds back, with its end 27, towards the inside of the first face 8 of the body 2, i.e. towards the bore 7. In the embodiment shown in the figures, a side portion or recess 36 is obtained in a side of the insulating element 3, said recess including an upper part 37 (i.e. the most distant part from the face 8) tilted and hollowed out, and a lower part 38 suitable for receiving a corresponding projection 15.

On the tilted and hollowed part 37 of the recess 36 the tilted end 27 of the wall 26 of the element or clip 21 elastically rests, said end 27 thereby pressing the insulating element 3 towards the face 8 of the body 5 of the door 2.

Obviously, if the insulating element does not have the part 37 tilted and hollowed, but the side wall of the insulating element 3 is continuous (but still tilt), then the end 27 of the clip would rest on such wall directly from the side portion 36 (which, in this case, presents the part 38 only, suitable for receiving the projection 15) .

The clip element also presents a tooth 40 projecting towards the face 8 and suitable for co-operating with a recess 41 thereof to lock the clip in the face 8. Such tooth is present in correspondence with a connection part between the base 20 and the wall 26. This locking, together with the action exerted by the end 27 of the element 21, enables the latter to exert such a pressure onto the insulating element as to press it against the face 8 of the body 5 of the door 2.

As a matter of fact, let's suppose to associate such insulating element 3 with the body 5. For this purpose, every screw 32 is inserted into its respective hole 15A of its corresponding projection 15. Thanks to the reliefs 16 and 17, such screw does not penetrate completely its respective hole and remains, with its head 39, far away from the projection 15 in correspondence with the sides of such reliefs 16 and 17.

Then the insulating element 3 is put onto the body 5 and the elements or clips 21 are positioned in correspondence with the recesses 36 of the insulating element 3. Then the base 20 of every clip 21 is made slide onto its corresponding projection; in this operation, the reliefs 16 and 17 of the latter guide such base to slide onto the projection 15. Since the head 39 of the screw 32 present in correspondence with such projection 15 is raised therefrom on the sides of the reliefs, the arms 28 and 29 of said base 20 slide under such head in such a way as not to be capable of lifting themselves from said projection.

Then the wall 26 is put in contact with the insulating element 3 within its corresponding recess 36 and the tooth 40 is made penetrate into its respective recess 41. In this way, the element or clip 21 is locked onto the insulating element 3 so as to press it towards the first face 8 of the body 5 of the door 2.

In this way, the binding operation of the element 3 onto the door 2 clearly takes place in a fast way and without any risks of breaking or deforming the insulating element 3.

In order to separate the latter from the door 2 it is sufficient to take the tooth 40 out of the recess 41 to "slip off" the base 20 of the element or clip 21 from the head 39 of the screw 32 fixed to the projection 15. Having removed said clips, the insulating element 3 is freely separable from the door 2, for instance, in order to replace it. All of this without splitting nor breaking such element .

Therefore, the door assembly here described is easy to assemble and disassemble, cannot cause the insulating element to break because it is not subjected to screws or pressing elements screwed therein, and can be implemented at reduced production costs.

A specific embodiment of the invention has been described. Others are also possible, like that wherein the elastically deformable element or clip 21 can have a different shaped part 26, but still such as to press the insulating element against the door 3 whenever it is fixed to the latter. Or, in correspondence with the hole 15A there might be present one relief 16 or 17 suitable for operating as a guide for positioning the base 20 of the element 21 on its respective projection 15. Such solutions and others derivable by one skilled in the art from the present description are also to be considered to fall in the scope of the invention as set forth by the attached claims .