Elastomeric sealing gasket for cooking ovens

Abstract: An elastomeric sealing gasket particularly for cooking ovens, to be placed between a front edge of the oven and the door of the oven itself, comprising a continuous strip (1), provided with metal elements (2, 2'), having respective hooks (21, 21') for engagement in respective holes provided in the oven structure, in which said metal hooking elements (2, 2') comprise a base (20) provided with transverse notches (22), which engages in a longitudinal cavity (3) of the strip (1), and is subsequently bent in the case of hooking elements (2) placed at the corners of the gasket (10, 100, 200).

Description: The present invention relates to an elastomeric sealing gasket, made in particular of silicone rubber, particularly for cooking oven doors. As is known, in cooking ovens elastomeric sealing gaskets interposed between the oven door and a rim or flange fitted in front of the mouth of the oven are commonly used to avoid heat loss during operation. These gaskets may be full-frame, that is, consisting of four sides joined together to form a rectangle, or open-frame. Since there is less heat loss in the lower area of the oven, provision is normally made for open-frame gaskets, in which a portion of the lower side is missing, or three-sided open-frame gaskets, in which the lower side is completely missing. Originally, these gaskets were obtained by joining together a plurality of pieces whose length coincided with that of the sides of the frame, and fixing them to the oven by suitable hooking means, provided in the gasket, that engaged in special holes in in the oven structure. For reasons of economy, the gaskets currently used are obtained by bending, and possibly joining at the ends, a single hollow strip with hooking means situated at least in the areas where the strip is bent, namely at the corners of the frame. Metal inserts having a widened base that is inserted in a corresponding hole or slit made in the flat bottom wall of the gasket are used as hooking means. Said widened base of the corner insert is curved in a crescent shape and is almost always manually inserted into the hollow part of the gasket through the hole provided on the bottom of the gasket itself. A hook that engages in a corresponding hole provided on the oven structure protrudes from the base of the metal insert through the hole provided in the gasket. For gaskets with three sides, or in any case of the open-frame type, two terminal metal inserts are provided that are inserted through the ends of the gasket and are normally fixed with adhesive. Gaskets of this type are described, for example; in GB-A-2 106 974 and EP-A-277 098. These gaskets with metal inserts have various drawbacks: the need to have a tubular strip, which has a high cost, also because a considerable amount of material must be used, mainly to provide the hollow inside; the possibility of tears in the gasket in the area where the holes or slits for insertion of the metal inserts are provided; the need to use preformed metal inserts which cannot therefore be adapted to a different radius of curvature if required. FR-A-2 553 170 describes an elastic gasket having a longitudinal C-shaped cavity, in which metal inserts provided with hooking elements for fixing the gasket to a support are inserted. These metal inserts can have a curved shape with a predetermined radius of curvature, in the event that the gasket has to follow a curved profile once mounted. The greatest drawback of this gasket is that, since the metal inserts have a predetermined radius of curvature, they do not allow the gasket to be adapted to different radiuses of curvature that may be used in the joins between the sides of an opening against which the gasket must be applied. In addition, the gasket according to this French patent has no sealing lips on the side from which the hooks of the inserts protrude, so that a good seal is not guaranteed on this side. DE 3 509 928 describes an elastic gasket for the door of an electrical appliance, which is fixed by means of metal inserts having a base that is inserted into the hollow profile of the gasket. This base has a plurality of notches that allow it to be bent. Insertion of the insert in to the gasket can cause tearing thereof. A further drawback of this insert is caused by the fact that if the base is made thin enough to allow bending, it is not very strong and tends to crease in the plane perpendicular to the plane of use of the gasket. If, on the other hand, the base of the insert is made thick enough to avoid this creasing, great difficulty is encountered in giving it the necessary curvature along the corners of the door. The object of the invention is to eliminate the aforementioned drawbacks, providing a gasket for cooking oven doors that allows precise adaptation to the radius of curvature of the corner joins of the mouth of the oven, eliminating any risk of tearing the gasket in the areas where the metal inserts with fixing hooks are housed. Another object of the invention is to provide such a gasket that is economical and allows rapid, automatic fixing of the metal inserts. These objects are achieved with the gasket according to the invention which has the characteristics listed in appended claim 1. Preferred embodiments of the invention appear from the dependent claims. During extrusion of the gasket according to the invention a cavity is obtained therein that is open on the outside for insertion of suitably shaped- metal inserts, possibly after preliminary treatment of the cavity with silicone glue. The metal inserts have a base provided with a plurality of crosswise notches, forming an indentation on the inner side, and a hook protruding from said base for engagement in a hole in the oven structure. The indentation on the inner side of the base of the insert allows easy bending thereof, to cause it to take on a curved shape, which is necessary when the inserts are placed at the corners of the frame. This bending of the bases of the metal inserts can be done when they are fitted on the gasket or, more advantageously, during installation of the gasket on the oven. In the latter case there is the advantage of obtaining bending of the insert automatically during fitting, of the gasket, when it is slightly stretched to bring the various hooks into engagement with the corresponding holes provided in the oven structure. The cavity made in the gasket is L-shaped, with a horizontal branch parallel to the bottom wall of the gasket, and the other branch entering perpendicularly into the thickness of gasket. Correspondingly, the cross section of the base of the metal insert has an L-shaped profile, thus causing stiffening in the plane perpendicular to that containing the indentation. To further stiffen the metal insert using very small thicknesses, stiffening ribs are advantageously, provided both coinciding with the protruding hook and with the flange of the insert perpendicular to one containing the indentation. The gasket according to the invention can be produced in a completely automated fashion and therefore at low-cost. Further characteristics of the invention will be made clearer by the detailed description that follows, referring to a purely exemplary and therefore non-limiting embodiment thereof, illustrated in the appended drawings, in which: Figure 1 is a diagrammatic plan view of a four-sided closed-frame gasket according to the invention; Figure 2 is a diagrammatic view of a three-sided open-frame gasket according to the invention; Figure 3 is a diagrammatic plan view of an open-frame gasket, without a portion of one side, according to the invention; Figure 4 is an axonometric view of a portion of a gasket according to the invention and of a metal hooking element shown separately from the gasket before application; Figure 5 is a diagrammatic plan view of a corner hooking element, applied to a gasket, before bending; Figure 6 is a similar view to that in Figure 5, after bending of the hooking element and with a part of the gasket cut away; Figure 7 is a cross section of the gasket, in which the corner hooking element is shown hatched; Figure 8 is a plan view of a metal corner hooking element before bending; Figure 8A is a cross section taken along the line A-A in Figure 8; Figure 9A is a plan view of a metal terminal hooking element for open-frame gaskets, which does not form part of the invention but is useful for understanding the invention; Figure 9B is a side elevation of the element in Figure 9A. With reference to these figures, the gasket for cooking ovens according to the invention comprises a continuous elastomeric strip 1, in particular of silicone rubber, and a plurality of metal elements 2, 2', 2", whose function will be described below. The continuous strip 1, obtained by extrusion, has a substantially L-shaped cavity or longitudinal seat 3, which has a continuous opening 4 extending along a flat bottom wall 5 of the gasket. A branch 3' of the L-shaped cavity 3 extends parallel to the wall 5, whilst the other branch 3", which is shorter, extends perpendicularly to the first downward into the body of the strip 1. Parallel to the two sides of the bottom wall 5 of the strip 1 extend respective lips 6, 7 which improve the seal against the surface on which the gasket is applied. A protruding, longitudinal fin 8 is provided on the opposite side of the wall 5 to form a seal against the complementary element of the oven where the gasket is interposed, in particular against the oven door. The fin 8 can be directed, depending on the solutions adopted, so as to point inwards, as illustrated in the appended figures, or outwards, indifferently. In the embodiment illustrated in the appended figures, the strip 1 has a tubular inner chamber 9, but it is obvious that said chamber 9 is not essential for the purposes of the invention and could be omitted. Figure 1 diagrammatically shows a gasket 10 with four sides, forming a closed rectangular frame; Figure 2 diagrammatically illustrates a gasket 100 with three sides forming an open frame without the lower side, and Figure 3 shows a gasket 1000 with a rectangular open frame, without a portion of the lower side. The above mentioned metal hooking elements 2, 2' are used to fix the gaskets to the corresponding wall of the oven, whilst the metal element 2", shown hatched in Figure 1, acts as a joining element to join the ends of the closed-frame gasket 10 in Figure 1. Obviously the end join of the gasket in Figure 1 could be made in other ways, for example by gluing the end edges of the gasket directly to one another. The structure and application procedure of the metal elements will now be described, in particular for the element 2 which can be placed at the corners of the gasket. As can be seen in the appended figures, and particularly in Figures 4, 8 and 8A, the metal element 2, advantageously obtained by shearing and bending a metal sheet, particularly of stainless steel, has a base 20, L-shaped in section, and a central element 21 protruding on the outside and bent to form a hook. The hook 21 protrudes from a flat flange 20' of the base 20 and foresees a first portion 21' substantially perpendicular to the flange 20', a second portion 21" substantially parallel to the flange 20' and a third end portion 21''' inclined towards the outside with respect to the flange 20'. Such configuration of the hook 21, thanks particularly to the presence of portion 21" parallel to the plane of usage of the gasket, strictly connects the gasket to the oven plane, preventing accidental slipping off or incorrect positioning of the metal element 2. The base 20 foresees, starting from its free edge, a series of substantially V-shaped notches 22, the other flange 20" of the base 20 extending perpendicularly to the flange 20' in the opposite direction to that toward which the hook 21 protrudes. As will be seen better below, the purpose of the notches 22 is to allow bending of the metal element in the plane of the flange 20'. In the appended figures the tips of the V-shaped notches 22 are disposed in the plane of the flange 20' of the L-shaped base, at a certain distance from its edge. However, if it is wished to further facilitate bending of the metal element, the depth of the notches 22 could be increased, until they also partially involve the other flange 20" of the base 20. The flange 20" of the base 20 serves to stiffen the metal element in the plane perpendicular to that of the flange 20' and thus prevent the metal element from bending in said plane. To further increase this stiffness, a longitudinal rib 50 is provided on the flange 20' (see particularly Figures 8 and 8A). A similar rib 51 is provided on the hook 21 to increase the strength of the latter. A possible further stiffening rib could also be provided at the longitudinal edge of the L-shaped base 20 or in the proximity of said edge on the flange 20'. The dimensions of the L-shaped base 20 of the metal element 2 are such that it can fit perfectly in the cavity 3 of the gasket, as shown in the appended figures. To improve fixing, silicone adhesive can preferably be placed in the cavity 3, before the metal element 2 is inserted, so as to ensure a better hold. The hook 21 obviously protrudes from the opening 4 provided on the bottom wall 5 of the gasket. Bending of the bases 20 to obtain the corner joins shown in Figures 1 and 6 can be done during application of these metal elements on the strip. However, at least for open-frame gaskets this bending can be done possibly at the same time as fixing of the gaskets on the ovens. In this case, in fact, bending of the bases 20 of the metal elements 2 takes place virtually spontaneously when the installer slightly stretches the gasket to insert the hooks 21 in the corresponding holes provided on the wall of the oven, causing said bases to take on the exact radius of curvature of the tops of the mouth of the oven. Obviously the distances at which the elements 2 are applied to the strip 1 are predetermined according to the distances of the corresponding engagement holes for the hooks 21, taking into account the fitting tension required of the gasket. Figures 9A and 9b, which do not form part of the invention, illustrate a metal hooking element 2' to be placed at or near free ends of the open-frame gaskets 100 and 1000 shown in Figures 2 and 3. This element 2' has a flat base 20 and a hook 21' provided on the longitudinal axis of the base 20, protruding from one end thereof A rib 52 is provided longitudinally to the element 2', on one side of the base 20, and extends to involve the terminal hook 21', in order to give the metal element greater stiffness. Respective series of teeth 55 are provided on the two opposite edges of the base 20, in order to improve the grip with the inner walls of the gasket at the branch 3' of the seat 3, in which the element 2' is housed. The metal element 2", when present, acts as a joining element to make the end join of the four-sided gasket shown in Figure 1 and in practice comprises a flat base 20, similar to that of the element 2' in Figures 9A and 9B, without the terminal hook 21' or with the said terminal hook unbent. Both the element 2' and the possible element 2", which engage in the branch 3' of the L-shaped seat 3 of the gasket are fixed by means of adhesive. From what is described the advantages of the invention are obvious. In particular the shape of the metal element 2 with an L-shaped section and possible reinforcing ribs makes it possible to use very small thicknesses of material, for example of the order of 0.4-0.5 mm, though maintaining a considerable thickness of the element in the plane perpendicular to the plane of the flange 20'. In this way any risk of bending of the metal elements 2 in this plane, for example when the housewife lifts the gasket during cleaning of the oven, is avoided. The flange 20" further helps to distribute on a very wide surface both the stresses due to normal functioning and the stresses casually caused by the housewife when cleaning the oven. Of course the invention is not limited to the particular embodiment described previously and illustrated in the appended drawings, but any modifications within the scope of an expert in the field can be made thereto, without thereby departing from the scope of the invention, as defined in the claims that follow.

Claims: An elastomeric sealing gasket particularly for cooking ovens, to be placed between a front rim of the oven and a corresponding door, said gasket comprising a continuous strip (1), provided with metal elements (2) having hooks (21), the strip (1) having a continuous longitudinal cavity or seat (3) with an outer opening (4), for accommodation of bases (20) of the metal elements (2), having the hooks (21) able to engage in holes provided in the oven structure, at least the base (20) of the elements (2) destined to be placed at the corners of the gasket having a series of notches (22) on one of its sides such as to allow bending of the element (2) in the plane of said base (20), characterized in that said cavity (3) provided in the strip (1) and said base (20) of the metal corner element (2) are L-shaped in section, a first branch (3') of said cavity (3) extending parallel to a bottom wall (5) of the gasket, in which said opening (4) is made, the other branch (3") extending perpendicular to the first branch (3'), down into the body of the gasket, the base (20) of said metal elements (2) having a first flange (20') provided with said notches (22) and another flange (20") perpendicular to the first, the flanges (20', 20") being able to lodge, respectively, in the branches (3', 3") of the cavity (3). A gasket according to claim 1 , characterized in that said notches (22) are substantially V-shaped, with the wide part of the V opening at the free longitudinal edge of said first flange (20'). A gasket according to claim 2 , characterized in that said notches (22) partially involve only the first flange (20') of said base (20) of the metal elements (2). A gasket according to claim 1 or 2 , characterized in that said notches (22) extend on the first flange (20') of the base (20) of said elements (2) until they partially involve the other flange (20"). A gasket according to any one of the preceding claims, characterized in that the said hooks (21) of the metal elements (2) foresee a first portion (21') substantially perpendicular to the first flange (20') of the said base (20) of the metal elements (2), a second portion (21") substantially parallel to the said first flange (20') and a third end portion (21"') inclined towards the outside with respect to the said first flange (20'). A gasket according to any one of the preceding claims, characterized in that said metal elements (2) are provided with reinforcing ribs (50, 51). A gasket according to claim 6 , characterized in that one of said ribs (50) extends longitudinally to said other flange (20") of the base (20) of the element (2), whilst the other of said ribs (51) involves the hook (21) of said element. A gasket according to any one of the preceding claims, charcterized in that said metal elements (2) are held in said cavity (3) by means of silicone adhesive, applied before or after insertion of said elements in the cavity. A gasket according to any one of the preceding claims, characterized in that said base (20) of the corner hooking element (2) is bent after application thereof to the strip (1).

Inventors: CARMELLI ALESSANDRO, FACCOLI ANGELO, CARMELLI, ALESSANDRO, FACCOLI, ANGELO
Applicants: POSA S P A, POSA S.P.A.
Application year: 1998
Main classification: F24C15
IPC codes: F24C15