IMPROVED GASKET OF ELASTOMER MATERIAL IN THE FORM OF A CLOSED OR OPEN FRAME FOR COOKING OVEN DOORS

Abstract: A frame gasket is described for cooking oven doors, which comprises a tubular profile (1) with inner longitudinal cavity (2) and peripheral flange (3), having only one butt joint, if any, even if the frame is of the four-side closed type. Coupling metal inserts are provi­ ded for engagement into associate holes (12, 13) of the abutment surface (14) about an over opening. In a first embodiment said inserts are either L-shaped (5, 6), pos­ sibly of asymmetrical legs, with coupling tabs (9) for the corner bent portions of the frame, or formed as elon­ gated metal plates (8) with spring-like prongs (9′) for engagement into holes (13) of the rectilinear lengths. These prongs (9′) and the coupling tabs protrude from the profile through slots (11) formed by removal of mate­ rial. In a second embodiment the metal inserts (20) are all identical, formed of a longitudinal plate length (21) to be fitted into the cavity (2) and fonded at an end thereof with a hooked tab (22) projecting outwardly through a hole (27) of the profile, there being provided two of said insert members (20) at each corner region (25, 25′) and one of them at each free end of the frame when it is open with three sides.

Description: The present invention relates to an improved gasket of elastomer material to be particularly used between a cooking oven opening and the associate door, being in the form of a three-side open frame or of a four-side closed frame. Various types of gaskets in elastomer material are known for cooking ovens, formed of three-side or four-side frames applied to the oven front portion which provides for a shoulder abutment against the associate door when closed. Sometimes the lower side may be missing, at the zone where both the vapour leakage and the heat loss are smaller. These gaskets may be integrally moulded, with corners already formed, but at so high costs that cannot be accepted by oven manufacturers. Less expensive are the frame-type gaskets formed of three or four separate pieces, one for each side, which however show discontinuity at the corners where the vapour leakage and heat losses are considerable. Furthermore their assembly may be rather difficult, especially when these gaskets are embedded in the sheet iron from which they partially protrude to the outside, during the preassembly step. It is true that frame-type gaskets have been recently provided in which the continuity at the corners is ensured by means of resilient metal prongs to be inserted into corresponding holes on the oven front portion, both at the corner zones and if necessary also along the longitudinal sides. Problems of mechanical breakage are however present due to the thermal expansions of the prong metal engaging the elastomer material under a certain stress. According to the Italian Utility Model 188 263 a continuous gasket is also known having shaped and spaced apart plugs of the same material, integrally formed for fitting into suitable slots provided in the sheet iron. In this case the seal tightness is certainly good, but a heavy employment of labour is required for fitting into the slot. Another difficulty derives from the end-to-end or butt joint of a four-sided gasket at a corner region. GB-A-2 113 827 requires to this effect an additional fastener means as an integrally moulded button, thus rendering necessary that each gasket corner is separately moulded to form said button and to embed a hooked metal insert. DE-A-3 509 928 shows a gasket with an inner longitudinal cavity along which metal inserts called "rails" are caused to slip therein until reaching the prefixed corner positions where they are bent to be properly shaped. FR-A-2 553 170 discloses a C-shaped profile at the inside of which the metal inserts are fixed by adhesive, without solving the problem of the butt joint. GB-A-2 106 974 only states that the strip (of gasket) is joined in an end-to-end fashion along one of the straight sides, thus excluding that a butt-joint be positioned at a corner. Furthermore according to this patent slits for housing the anchoring inserts are obtained by cutting the gasket profile, with problems of centering the insert therein and the danger of tearing or ripping the gasket, of silicone-based elastomer, by giving rise to a weakened line or preferential direction of continuation of the cutting under stretching, thus rendering necessary the use of adhesive not only to keep the correct position, but also to stop the tearing action. Centering problems are also present in FR-A-2 553 170 and DE-A-3 059 928, where a tab-shaped protruding member of the metal insert is caused to pass outwardly through the wall of the inner cavity. All these prior patents and particularly GB-A-2 106 974 and DE-A-3 05 9928 disclose, if any, metal inserts in a tubular profile which are always in contact with the adjacent edges of a slit cut in the same profile. Therefore it is an object of the present invention to provide a gasket according to the preamble of claim 1 which does not show these problems and difficulties of the prior art. This is obtained through the features of the characterizing portion of claim 1. These and other objects, advantages and characteristics of the sealing frame according to the invention will clearly result from the detailed following description with reference to the drawings in which: FIGURE 1 shows a perspective view of a closed four-sided gasket frame according to the invention; FIGURE 2 shows another perspective view of an open three-sided frame of the invention; FIGURE 3 shows more in detail the particular III of Fig. 1, wherein the butt joint of the profile is near to a corner bent portion; FIGURES 3a, 3b show two embodiments of a L-shaped insert member for a radiused corner zone, wherein the one of Fig. 3b is of the type illustrated in Fig. 3 with the junction in proximity of the corner; FIGURE 4 shows in detail the particular IV of Fig. 1 at an intermediate engagement zone along a rectilinear side of the frame; FIGURES 4a, 4b respectively show the spring-like prong insertand a portion of tubular profile of the frame with slot for the fitting of said insert; FIGURES 5, 5a respectively show in greater detail the particular V of Fig. 2 and the associate coupling insert only; FIGURE 6 shows an oven opening with the stationary portion on which the sealing frame has to be mounted and the oven door at an open position. With reference to Figs. 1-4 a gasket formed of a tubular profile 1 of elastomer material, preferably silicone rubber, is provided in a known manner with an inner longitudinal cavity 2 and a protruding V--angled flange 4 integrally formed by extrusion. According to a particular embodiment of the present invention at the side opposite to the flange 4 two parallel longitudinal ribs 3 are preferably provided having the purpose of ensuring a more efficient tightness of the gasket onto the surface of the stationary abutment zone, particularly the front portion or abutment surface 14 of an oven as represented in Fig. 6, while flange 4 is useful for the sealing with the mobile portion surface, particularly the oven door 15. The flange 4 will be directed no matter either to be convergent towards the oven inside or diverging outwardly. In the first instance a better tightness will be obtained as the flange works under pressure, while in the second one the gasket can be considered as "self-cleaning", since the upper side has the function of a gutter to prevent possible dirty or fluids from entering the sealed opening, and the lower side, if any, has the opposite function of helping possible dirty or fluids to drops therefrom. As the gasket frame is formed of a single profile joined at any point whichever along its perimeter there is no discontinuity of the sealing at the critical areas located at the bent corners. The gasket frame is fastened to the sheet iron surface of oven 14 by means of metal inserts or fits of various type, all provided with a protruding coupling member to be fitted into associate holes 12, 13 formed in the abutment surface 14. A profile stretch, of resilient character, to be preferably established, is obtained by properly arranging the center to center distance between holes 12 of the corner zones and 13 along the longitudinal portions, and designing slightly shorter such a distance at the locations corresponding to the frame fastening. This stretch can be different from a length to another according to the distance between the fastening points, their placement and orientation. Therefore there are corner-radiusing insert members 5 which are L-shaped (see Fig. 3a) and provided with a coupling hook 9 for fitting in holes 12, and metal plate inserts 8 with resilient prongs 9′ for insertion in holes 13. Both these shapes of insert member are accommodated into the inner longitudinal cavity 2 of tubular profile 1 through slots 11 formed by removal of material on the side of the profile opposite to flange 4, at the planar area comprised between the two possible longitudinal ribs 3. The distance between slots 11 is a function of the space between holes 12, 13 and the desired stretch, as stated above. Their shape will be such as to allow the stretched fitting of the inserts when considering the resilient mechanical features of the elastomer material adopted and the size of the members themselves to be inserted. A slight shrinkage of the tubular cross-section, due to stretching, causes an increase of interference between elastomer and metal parts, thus ensuring the mutual fastening thereof in case of particularly severe applications. For a greater safety the metallic parts could be bonded to the profile by a suitable adhesive, although not necessary. As stated before, the butt joint to have the closed profile of Fig. 1 may be formed at any location and, if in proximity of a corner, according to the invention a bent insert member 6 (Fig. 3b) with an elongated leg is advantageously used. As seen in Fig. 3 the longer leg of insert member 6 projects from one end of the profile to which the other end is joined for causing the frame to close itself. Bonding is provided by a suitable adhesive, especially silicone-based, as well as by the metal insert being fitted to the profile inner walls, and mechanical resistance resulting from the portion of adhesive mass polymerized in the gaps formed between some notches 10 which are provided on the longer leg of insert member 6 and the inner walls of profile. Consequently, the radiused corners of the frame and fastening at these zones are provided by bent metal insert members 5, 6 which at the same time give the profile an adeguate stretch along its axial direction, and the gasket fastening also orthogonally to the abutment surface 14 is provided by the metal plate inserts 8 which are also fitted into the slots 11 formed on the rear side of the profile (see Figs. 4, 4a, 4b). The open-shape or three-side frame (Fig. 2) is obtained making similarly use of only two bent corner inserts 5, of two elongated coupling inserts 7 (Figs. 5, 5a) and possibly, to improve the fastening in a perpendicular direction, of some metal plate inserts 8. The coupling insert 7 is fitted with its elongated portion into cavity 2 of the tubular profile 1 from which it protrudes with a hooked tab 9a which, contrary to the coupling hooks 9 associate to insert members 5 and 6, extends longitudinally while reamaining on the same plane of the insert member with no need of slots 11. As it results from the foregoing description, at least three different types of metal inserts are required, all provided with a protruding engagement element capable of fitting into corresponding holes of the abutment surface. Furthermore, for a good accommodation of the profile in the vicinity of the corners, it is important that the L-shaped metal inserts have a bending radius coincident with the one required for the profile. It will be noted that the tensioning of the free lenghts of profile 1 will be suitably calculated in order to ensure a correct operation of the gasket within the temperature range required, without any deformation or bowing. As it will be seen from the foregoing description, the frame gasket is of a single piece and there is, if any, only one butt joint with possible rubber-metal contact. Finally this gasket can be easily and readily mounted, as well as removed from its seat with likewise easiness and rapidity to be cleaned, thus ensuring very good hygienic conditions in addition to an ever efficient thightness.

Claims: 1. A frame-like gasket of elastomer material, particularly for cooking oven doors, formed of a tubular profile (1) with inner longitudinal cavity (2) and having a continuous, frontally protruding peripheral flange (4), with only one butt joint, if any, and metal coupling inserts (5, 6, 8) being provided for engagement under stretch in associate holes (12, 13) on an abutment surface (14) of sheet iron, said coupling inserts being located at the inside of the tubular profile (1) from which they project outwardly, partially through slots or holes (11) with protruding portions (9, 9′), characterized by the fact that said slots (11) are obtained by removal of material at the rear portion of profile (1) and their size in a plane orthogonal to the longitudinal axis of the tubular profile (1) is greater than the corresponding size of the protruding portion (9, 9′) of the metal insert therein, whereby at least one edge of said slot (11) is out of contact with said protruding portion. 2. A gasket according to claim 1, wherein said metal inserts (5, 6) have coupling hooks (9) protruding from said slots (11) in proximity of the corner zones of said frame for fitting into holes (12) of the sheet iron surface (14), and have a radiused L-shape. 3. A gasket according to claim 2, wherein said L-shaped inserts (6) have two legs of different length, asymmetrical with respect to the coupling hook (9) for engagement at corner regions in whose vicinity a butt joint is provided, the longer leg of said insert (6) being along the junction side. 4. A gasket according to one of the claims 2 or 3, wherein said metal coupling inserts (8) interposed between those (5, 6) at the corner zones for fastening in a direction perpendicular to the abutment surface (14) are comprised of an elongated metal plate and protruding resilient prongs (9′) to be fitted into said holes (13). 5. A gasket according to claim 1, formed of only three-sides of profile (1) without any butt joint, wherein each one of the two free ends of said profile is fastened to the abutment surface (14) by means of additional coupling inserts (7) longitudinally protruding from the inside (2) of the tubular profile (1) and provided with longitudinally extending hooked tabs (9a). 6. A gasket according to at least one of the preceding claims, wherein the rear side of profile (1), opposite to said protruding peripheral flange (4) has two longitudinal parallel ribs (3) laterally defining a strip of profile (1) where said slots (11) are formed.

Inventors: BOCCA, LUIGI
Applicants: GIAT S.R.L.
Application year: 1988
Main classification: F24C15
IPC codes: F24C15