Particularly, the invention refers to an improvement introduced in the retention and sealing system for the pressure lid of these cans.

Background of the Invention For decades, metal cans have been known for having a structural ring conventionally secured to the upper edge of the tubular body of the can and including a pending inner peripheral skirt defining the opening for accessing the inside of the can, and also a generally cylindrical seat, to which is pressure fittable the peripheral wall of a sealing lid which is manually removable and also recloseable during the period in which the can is used.

In these prior art cans, the sealing and the axial retention of the lid in the mounted position are achieved by pressure seating the peripheral wall of the lid against the inner peripheral skirt of the structural ring. This type of constructive solution has some deficiencies resulting from the small degree of axial locking of the lid and also from the fact that the free lower edge of the skirt, which is not subject to treatment, is in contact with the canned product.

In order to eliminate the aforementioned inconveniences, there has been developed the constructive solution which is object of the co-

pending patent application PI9600454 of the same applicant, according to which the axial locking of the lid is achieved by providing, in one of the parts defined by the peripheral skirt of the access opening and peripheral wall of the lid, an annular groove fittable in a corresponding circumferential recess having a section similar to that of the annular groove and provided at the other of said parts. In this construction, the groove and the recess have substantially coincident profiles of a semicircular shape, defined so that said parts fit each other with a substantially complete contact between its confronting surfaces.

Although guaranteeing a greater axial locking of the lid, avoiding its undue opening due to shocks, internal pressure increase, etc., and allowing an adequate degree of hermeticity to be achieved, keeping the canned product out of contact with air, this construction has the disadvantage of requiring great precision in the formation of the annular groove and circumferential recess, in order that said groove and recess have minimal mutual superficial contact when the lid is closed.

Due to dimensional imperfections that generally exist in these cans, the fitting between the groove and the corresponding circumferential recess usually occurs with a certain radial gap, reducing the contact between the respective confronting surfaces to only one tangency circumferential line. This contact does not guarantee an adequate hermeticity to the can, allowing the canned product to deteriorate.

Another common deficiency of the known constructions for the can and lid refers to the achievement of automatic closing of cans at the filling units of said cans. It is usually observed cans in which the

conventionally secured peripheral edge of the inner ring of the can is placed on a plane which is at the same level or slightly above the plane of the upper edge of the lid seated at the central opening. In such cases, an inadequate closing may usually occur, with insufficient introduction and pressure of the lid against the can when the latter is passing under the closure roll or piston of the filling machine.

Still another deficiency of the known constructions refers to the accumulation of the product which is spilled over the structural ring of the can during the progressive consumption of the can content, making subsequent closings of the lid more difficult and consequently making possible the contact of air with the product inside the can, allowing, for example, the oxidation of the product and also, in the case of products having volatile elements in their composition, such as paints, the evaporation of said elements, causing the hardening of the remaining product in the can.

Disclosure of the Invention It is therefore an object of the present invention to provide a can with a pressure lid having high levels of axial retention and hermeticity, without requiring great dimensional precision or constructive complexity in the formation of the parts that are going to be interlocked.

It is also an object of the present invention to provide a can of the type described above which turns the problem of product accumulation over the can structural ring little or non relevant in the conditions of subsequent closings of the lid and hermeticity of the reclosed can.

It is still an object of the present invention to provide a can as described above which conducts to a

safe closing of the lid at the product filling units.

These and other objectives and advantages of the present invention are achieved through a can with a pressure lid comprising a tubular body which carries, upperly and internally, a structural ring with an inner peripheral edge, which receives a peripheral wall of a lid, one of the parts defined by the peripheral wall of the lid and the strutuctural ring including a circumferential groove which is fittable, in a closed can condition, in a corresponding circumferential recess provided at the other of said parts, at least one of said parts being elastically deformable to allow the fitting and removal of the lid. The circumferential recess and the circumferential groove are shaped and dimensioned so that, in a closed can condition, they may be mutually seated along at least two tangency circumferential lines, which are concentric and placed in planes which are parallel and axially displaced to each other and transversal to the can axis, said tangency circumferential lines being radially external to the innermost radial circumferential line of the groove, being the plane of at least one of said tangency circumferential lines lower than the plane of said innermost radial circumferential line of the groove.

Generally, the inner peripheral edge of the structural ring incorporates a pending skirt to receive the peripheral wall of the lid and in which is provided one of the elements defined by the circumferential groove and the circumferential recess.

Brief Description of the Drawings The invention will be described below with reference to the attache drawing, in which: Figure 1 represents schematically a partial diametrical section view of the upper portion of a can

which is closed by a pressure lid and built according to the present invention; and Figure 2 represents schematically an enlarged view of part of figure 1 in which occurs the locking and sealing between the lid and the can.

Best Way of Carrying Out the Invention The present invention will be described according to what is illustrated in figures 1 and 2, in relation to a can comprising a tubular body 10 of any polygonal contour, e. g. cylindrical, in which upper edge 11 is conventionally secured a structural ring 20, which inner peripheral edge defines a generally circular upper opening, taking up a substantial part of the total area of the can contour and forming the seat onto which is seated and retained a lid 30.

According to the present invention, the structural ring 20 of the tubular body 10 presents its inner edge incorporating a pending skirt 21, which defines a retaining seat for the lid 30. The structural ring 20 of the can is shaped in order to have, medianly, at least one reinforcing upper annular groove 22, obtained by folding the sheet of the inner ring 20 and having, for example, an inverted"U"shape with rounded edges and projecting above the medium plane of said structural ring 20. The provision of this reinforcing upper annular groove 22 may take place jointly with the usual provision of a lower annular groove 23 projecting below the plane of the structural ring 20.

The provision of the reinforcing upper annular groove 22 allows achieving a greater stiffening of the structural ring 20 of the can, reducing the thickness of the sheet that forms said structural ring, with a consequent reduction of material consumption.

In the illustrated construction, the free end of the

pending skirt 21 is curved upwardly until it finds an adjacent portion of the inner surface of the pending skirt 21, in order to define a circumferential groove 24, which is tubular and has, for example, a substantially circular transversal profile.

In another possible construction (not illustrated) the pending skirt 21 is eliminated or substituted by an inclined inner portion of the structural ring 20, in order to have the circumferential groove 24 adjacent the inner edge of the structural ring and curved upwardly and radially outwardly until it finds an adjacent portion of the upper surface of the strutural ring.

The lid 30 has a bottom wall 31, wherefrom is upwardly projected a peripheral wall 32 in which free end is defined an upper peripheral edge 33. It must be noted herein that the dimensioning of the reinforcing upper annular groove 22 and peripheral edge 32 of the lid 30 is carried out in order that the plane which contains said upper peripheral edge 33 of the lid 30 in a closed condition is located above the planes which contain, respectively, the top of the reinforcing upper annular groove 22 and the upper edge conventionally secured in the tubular body 10 of the can. Since the plane containing the upper peripheral edge 33 of the lid 30 is the one more axially upwardly located, it will be guaranteed the action of the closure means at the product canning units, such as roll and piston, against the lid and, consequently, the full automatic closing of the latter.

The peripheral wall 32 of the lid 30 is provided with a circumferential recess 34, which is obtained through plastic deformation and medianly located, for locking the lid 30 to the can, as described hereinafter.

In the closing condition of the can, the

circumferential recess 34 of the lid 30 is fitted by being seated against the circumferential groove 24 of the pending skirt 21 of the can, in the closed can condition. In this condition, the peripheral wall 32 of the lid 30 is seated against the pending skirt 21 of the structural ring 20, and the upper peripheral edge 33 of the lid 30 is seated on the structural ring 20, limiting the fitting axial displacement of the lid 30.

The circumferential groove 24 and the circumferential recess 34 are dimensioned in order to keep the lid 30 fitted in the can, avoiding spontaneous openings, but allowing the removal of said lid 30 when the user applies an axial extraction force. The release occurs with an elastic deformation of the pending skirt 21 of the structural ring 20, sufficient to separate the circumferential groove 24 from the circumferential recess 34.

The bottom wall 31 of the lid 30 is provided with a tubular drawn back portion 35, which is axial and median, and preferably projecting upwardly, in order to provide an additional internal volume to the can that is going to be closed and consequently providing additional safety to the can against spontaneous opening of its lid due to an internal pressure increase.

The tubular drawn back portion 35 presents an annular step 36 which reduces the diameter of an upper portion of said tubular drawn back portion 35, and which defines a stop to avoid the introduction of another lid when cans are stacked. The tubular drawn back portion 35 further presents, on its upper end wall 37, an inclined circumferential plane 37a for structural reinforcement of the lid. The peripheral wall 32 of the lid 30 is further provided with a lower edge 38,

defining a ramp along which slides the circumferential groove 24, through elastic deformation of at least one of the parts defined by the peripheral wall 32 of said lid 30 and pending skirt 21, during the downward displacement of the lid toward the closed position.

According to the illustrated embodiment, the circumferential groove 24, having a circular cross- section, and the circumferential recess 34 are shaped and dimensioned in order that, in a closed can condition, said parts mutually seat according to at least two tangency circumferential lines 25,26 between the circumferential groove 24 of the pending skirt 21 and the circumferential recess 34, said tangency circumferential lines 25,26 being defined concentrically, and axially and vertically displaced to each other, in respective planes which are mutually parallel and transversal to the can axis, and in order to be radially external to the innermost radial circumferential line of the circumferential groove 24.

According to the present invention, the mutual seating between the circumferential groove may occur through a plurality of tangency circumferential lines, one of said lines being inferiorly placed in relation to the radially innermost line of the groove, in order to actuate in the locking of the lid 30 to the can. In this case, said tangency circumferential line also actuates in the sealing of the can. In the construction presenting the circumferential recess defined in the lid 30, the peripheral wall 32 of the latter is shaped in order to define, below the portion of said wall provided with the circumferential recess 24, a displacement surface along the circumferential groove during the positioning of the lid 30 to a closed condition.

As illustrated, the tangency circumferential lines 25,

26 are defined by the contact between the respective ramp surface portions of the circumferential recess 24 and the circumferential groove 24.

According to the present invention, the tangency circumferential lines 25,26 are defined and kept by an elastic deformation of at least one of said pending skirt 21 and circumferential recess 34 parts, said part being defined in function of the positioning of the tangency circumferential lines 25,26 in relation to the innermost circumferential line of the groove.

In a constructive option of the present invention, at least one of said tangency circumferential lines 25, 26 is below the plane of the innermost circumferential line of the groove. In the solution in which both tangency circumferential lines 25,26 are below the innermost circumferential line of the groove, the seating of the upper peripheral edge 33 of the lid 30 against the structural ring 20 works as a stop to limit the introduction of the lid 30 into the can and also as a keeper of the seating condition of said tangency circumferential lines 25,26. In this condition, both tangency circumferential lines 25,26 actuate to achieve the locking of the lid to the can in a closing condition, the innermost circumferential line further assuring a sealing of the inner content of the can. In this construction, keeping the closed lid condition is achieved through an elastic deformation of the pending skirt 21.

In the illustrated construction, the tangency circumferential lines 25,26 are defined opposite to each other in relation to the plane of the innermost circumferential line of the circumferential groove 24, e. g. by being axially aligned to each other. In this construction, the mutual seating condition between the circumferential groove 24 and the circumferential

recess 34 is achieved through their mutual actuation and is maintained with an elastic deformation of the pending skirt 21 and circumferential recess 34 parts.

The seating of the upper peripheral edge 33 of the lid 30 against the structural ring 20 works only as a stop for limiting the introduction of the lid 30 into the can.

The dimensioning of the circumferential groove 24 and circumferential recess 34 parts is defined so that at least one of these circumferential regions, e. g. the one placed inferiorly in relation to the circumferential groove 24, in the case of the tangency circumferential lines being in opposite sides in relation to the innermost circumferential line of the groove, retains the lid 30 to the can until a determined axial force, upward and voluntary, for extracting the lid 30, results in a radial force of the circumferential region which retains the lid 30 to the can over the circumferential groove 24, sufficient to produce an elastic deformation in at least one of the pending skirt 21 and lid 30 parts, for releasing the mutual fitting obtained in the closing condition of the lid 30 in relation to the can.

In order to avoid problems resulting from dimensional imprecision in the construction of the circumferential groove 24 and circumferential recess 34, the latter is defined with a curved portion having a smaller radius than the radius which constitutes the circumferential recess 34, so that in the fitting condition of lid 30 in the upper opening of the can, the curvature center of the circumferential recess 34 and circumferential groove 24 parts be eccentrically positioned in relation to each other.

The circumferential recess 34 is"V"shaped, having a rounded vertex, determined so that the tangency

circumferential line 26, defined inferiorly in relation to the innermost circumferential line of the circumferential groove 24 during the fitting condition of the lid 30 into the can, guarantees that involuntary upward axial forces on the lid 30 do not result in its removal from the can.

The tangency circumferential lines 25 and 26 determine a pair of seals for sealing the lid 30 to the can which, besides avoiding the involuntary opening of the can, guarantee, independently from dimensional variations between the circumferential recess 34 and circumferential groove 24 parts, the hermeticity of the product stored inside the can.

Although not illustrated, other constructions are possible for the present invention, as for example the provision of at least one circumferential groove which is fittable in a corresponding circumferential recess, which groove and recess can be provided in any of the parts defined by the pending skirt 21 of the can and peripheral wall 32 of the lid 30.