JP7811528B2 - Lid - Google Patents

Description

The present invention relates to a lid suitable for microwave-safe paper containers for heated processed foods such as gratin and doria.

In recent years, with the rise in the need for solo meals, there has been an increasing demand for fully cooked products such as gratin and doria at supermarkets and convenience stores. Since such gratin and doria are typically reheated in a microwave oven just before serving, they are widely sold in shallow, heat-resistant cup-shaped paper containers, the lids of which are typically made of transparent resin.

However, because gratin and doria containers are shallow and typically reheated to high temperatures, the edges of the lids are also quite hot when removed from the container after microwave cooking, and because the insulating properties of the paper container make it difficult to cool. This creates problems such as burns when carrying or eating the container with your hands, and the heat makes it difficult to remove the lids.

Consequently, a lid for a gratin/doria container that can be easily held with one hand after microwave heating has been known, which has a finger loop formed through a recessed groove near the outer edge of the lid and a protrusion connected to the finger loop (see Patent Document 1).

However, the lid described in Patent Document 1 employs a so-called external fitting method, in which a fitting protrusion is provided on the outer peripheral skirt portion to fit onto the paper container. This structure allows heated steam to fill the container body's inner wall up to the top, making it inevitable that the gripping portion would become very hot immediately after heating. Furthermore, the protrusions formed on the finger loop portion of the lid described in Patent Document 1 are small dot-shaped protrusions in plan view, and when heated steam enters, there is no space within the small protrusions to moderate the temperature of the heated steam, meaning that the protrusions themselves inevitably become very hot.

Japanese Patent Application Laid-Open No. 2021-155053

The problem that this invention aims to solve is to provide a lid for a paper container with a curled opening edge, which keeps the temperature of the handle low immediately after heating in a microwave oven with the lid closed, and which quickly cools down over time, making it easy to handle with bare hands from immediately after cooking until eating.

After extensive research to solve the above-mentioned problems, the inventors discovered that by adopting a so-called inner-outer fitting, in which the fitting portion of a lid for a cylindrical paper container clamps the upper inner and outer wall portions of the container body, and by providing intermittent ridges with long sides in the circumferential direction on the upper surface of the fitting portion along the outer edge of the lid, the temperature of the ridges does not become too high immediately after cooking in a microwave oven and quickly cools down after cooking, thereby completing the present invention.

That is, the present invention provides a lid for a cylindrical paper container having an opening at the top and a curled opening edge at the top end thereof, the lid having a top surface, a lid wall hanging down from the outer edge of the top surface, a groove bottom extending outward from the lower end of the lid wall, and a fitting portion continuing from the outer edge of the groove bottom and clamping the side wall of the cylindrical paper container,
The fitting portion has an inner fitting wall that extends upward from the outer edge of the groove bottom and abuts against the inner wall surface of the container, an annular fitting upper portion that covers the curled opening end, and an outer fitting wall that extends downward from the outer edge of the annular fitting upper portion and abuts against the upper outer wall of the container, and the lid body is further characterized in that the annular fitting upper portion has intermittent convex protrusions along the circumferential direction of its annular structure.

This invention provides a lid for a paper container with a curled opening edge, which keeps the temperature of the handle low immediately after heating in a microwave oven with the lid closed, and quickly cools down over time, making it easy to handle with bare hands from immediately after cooking until eating.

FIG. 1 is a perspective view of a paper container body. FIG. 2 is an end view of a cross section cut along the diameter of the paper container body in a plan view. FIG. 3 is a perspective view of the lid of the present invention. FIG. 4 is a plan view of the lid of the present invention. FIG. 5 is a partially enlarged view of the plan view of FIG. FIG. 6 is a front view of the lid of the present invention. FIG. 7 is an end view of the lid of the present invention. FIG. 8 is a partial enlarged view of the end face of the lid of the present invention. FIG. 9 is an end view showing the end face of the fitting portion between the paper container body and the lid body. FIG. 10 is a perspective view of the paper container body and the lid body in a fitted state.

As described above, the lid of the present invention is a lid for a paper container having an opening at the top and a curled open end, and has a top surface, a lid wall that hangs down from the outer edge of the top surface, a groove bottom that extends outward from the lid wall, and a fitting portion that continues from the outer edge of the groove bottom and clamps the upper part of the side wall of the cylindrical paper container.

Here, the fitting portion that clamps the upper sidewall of the paper container has a structure that employs a so-called internal/external fitting method (e.g., fitting portion 24 in Figure 3). The fitting portion includes an inner fitting wall (e.g., fitting portion 24a in Figure 3) that extends upward from the outer edge of the groove bottom and abuts the inner wall surface of the container; an annular fitting upper portion (e.g., ridged protrusion portion 24c and non-protrusion portion 24b in Figure 3) that covers the curled opening end; and an outer fitting wall (e.g., fitting outer wall 24d in Figure 3) that extends downward from the outer edge of the annular fitting upper portion and abuts the upper outer wall of the container. This constriction of the upper sidewall of the paper container from both the inside and outside prevents steam from migrating upward from the lower end of the fitting portion when heated in a microwave oven, thereby suppressing the temperature rise at the upper end of the fitting portion. The state in which the fitting portion clamps the upper sidewall of the paper container body can be shown, for example, in Figures 9(a) and 9(b). Here, Figure 9(a) is an end view taken along line A-A in Figure 4 when the lid is closed, and Figure 9(b) is an end view taken along line B-B in Figure 4 when the lid is closed.

The upper fitting portion is also characterized by having intermittent ridge projections (e.g., ridge projections 24c in Figure 3) along the circumferential direction of the annular structure. In other words, the upper fitting portion has ridge projections that are connected at equal or approximately equal intervals around the periphery of the lid, with non-projecting portions (e.g., non-projecting portions 24b in Figure 3) in between.

The planar shape of such a convex projection may be substantially rectangular, elliptical, polygonal, etc., but in the present invention, a substantially rectangular shape with the long side extending circumferentially is preferred, as this ensures a sufficiently large space within the convex projection and provides excellent grip when holding the container with the hand. Here, the convex projection forms an internal space of a predetermined size between itself and the top of the container body wall. Therefore, even if heated steam passes through the mating inner wall and reaches the internal space, the steam will diffuse within the internal space, preventing a rise in temperature at the gripping portion.

In order to ensure sufficient internal space, the size of the convex projection is preferably such that the long side of the base (convex projection length (a)) in a generally rectangular plan view is 4 to 10 mm, the long side of the top end (b) is 3 to 8 mm, the short side (convex projection width (d)) in a generally rectangular plan view is 0.5 to 2 mm, and the height from the base to the top end (convex projection height (h)) is 0.5 to 2 mm. Here, the convex projection height (h) from the base to the top end is expressed as the height (h) at which the length of the perpendicular to the line segment passing through both bottom ends of the convex projection in a cross-sectional view is at its maximum, as shown in Figure 8(a). Here, Figure 8(a) is an end view taken along the line A-A in Figure 4.

The above-mentioned convex protrusions are arranged intermittently along the outer periphery of the lid of the present invention, and the length between the convex protrusions in the circumferential direction, i.e., the length of the non-protrusion portion (e.g., the gap length (c) in Figure 5), is preferably 1.5 to 3 mm.

The annular fitting portion is preferably formed to minimize the gap, following the shape of the curled opening edge located at the top of the container body opening. Specifically, its diametric width (fitting portion width (w)) is preferably 2.5 to 5 mm. Here, the diametric width (w) of the annular fitting portion is, for example, as shown in Figure 8(b), the linear length between the intersection point x of a tangent to the fitting inner wall 24a of the annular fitting portion and a line passing horizontally through the vertex of the non-protruding portion 24b of the annular fitting portion, and the intersection point y of a perpendicular line tangent to the fitting outer wall 24d and a line passing horizontally through the vertex of the non-protruding portion 24b of the annular fitting portion. Here, Figure 8(b) is a B-B end view of Figure 4.

In the present invention, the convex protrusion is located on the upper surface of the lid fitting portion, but it is preferable that it be located on the outside to prevent the intrusion of heated steam. Specifically, it is preferable that the midpoint of the width (d) of the convex protrusion is located outside the midpoint of the width (w) of the fitting portion.

Furthermore, it is preferable that the ratio of the width (d) of the ridge projection to the width (w) of the mating portion [(d)/(w)] be in the range of 0.15 to 0.8, as this keeps thermal conductivity to the ridge projection low and improves the vapor diffusion effect in the space within the ridge projection.

The lower end of the fitting outer wall further bends inward in cross section to enclose the upper part of the side wall of the paper container body, narrowing the curled edge and connecting to a skirt portion (e.g., skirt portion 25a in FIG. 6). Furthermore, the lower end of the skirt portion is positioned lower than the curled opening end, and the skirt portion preferably has a fitting locking portion (e.g., fitting locking portion 25b in FIG. 6) that protrudes inward like a convex strip to further strengthen the internal and external fitting of the lid body of the present invention and ensure a secure attachment with a clicking sensation when the lid body is fitted. The size of this fitting locking portion is preferably 20 to 60 mm in length in the circumferential direction of the outer edge of the lid body 2 (e.g., fitting locking portion width _W25b in FIG. 6).

Next, the top surface of the lid 2 (for example, top surface 21 in Figure 3) is preferably circular or elliptical in plan view, but it is preferable to match the shape of the opening of the container body. In particular, for use as a container for single-serving doria or gratin, it is preferable to use a container body that is circular in plan view, and for the top surface shape of the lid 2 to also be circular in plan view to match this.

It is also preferable to have a thread-end-like ridge portion (e.g., thread-end-like ridge portion 21a in Figure 3) that forms a convex ridge at the top along the outer periphery of the top surface, as this increases the rigidity and strength of the entire lid body 2, stabilizes the fitting state, and effectively prevents the grip portion from becoming too hot.

The height (t2) of the ridge-like ridge portion on the top surface of the lid (see Figure 8(b)) is preferably 0.8 to 1.5 mm, as this improves the rigidity and strength of the entire lid. Furthermore, it is preferable that the radius of curvature Re of the ridge-like ridge portion 21a be 0.4 to 0.8 mm, as this improves the strength of the entire lid and improves the stability of the fit.

Furthermore, the ridge-like protrusions on the top surface of the lid may be arranged seamlessly around the outer edge of the top surface, but by forming them intermittently through missing portions 21b as shown in Figure 3, the strength of the ridge-like protrusions themselves is increased, effectively preventing the top surface from buckling due to external forces.

The top surface preferably has steam holes that allow steam generated during cooking to be released to the outside. The steam holes can be in a variety of shapes, including round holes, linear elongated holes, L-shaped elongated holes, diagonal lines, S-shaped elongated holes, C-shapes, U-shapes, and tongue-shaped holes. These steam holes can also be formed by cutting with a press, irradiating with a laser, or irradiating with ultrasonic waves.

Among these, for use in gratin and doria containers, C-shaped, U-shaped, and tongue-shaped notched valves are preferred because they are heated to high temperatures and emit a large amount of steam, and because they minimize the penetration of high-temperature steam into the peripheral edge of the lid of the present invention and allow it to be efficiently emitted through the steam holes in the top surface. It is preferable to form multiple such C-shaped, U-shaped, or tongue-shaped notched valves on the top surface, and specifically, it is preferable to have 2 to 6 of them in place in terms of steam emission efficiency.

Furthermore, when providing a C-shaped, U-shaped, or tongue-shaped notched valve, a recess one step lower than the top surface may be provided within the top surface, with the notched valve provided within the bottom surface of the recess. Alternatively, a groove-shaped recess may be provided in the top surface, with the notched valve provided across the recess. Alternatively, an inverted dome shape may be formed with the lower side at the apex, and the notched valve provided within this groove or inverted dome.

The lid of the present invention has a lid wall (e.g., lid wall 22 in Figure 3) that hangs down outward from the periphery of the top surface, and a groove bottom (e.g., groove bottom 23 in Figure 3) that extends outward from the lower end of the lid wall, the outer edge of which is connected to the mating inner wall of the mating portion (e.g., mating inner wall 24a in Figure 3).

In the present invention, by positioning the groove bottom as low as possible, the height of the mating portion can be ensured, which is preferable because it allows the paper container body and curled opening end to be more firmly and constrictively fitted together at the mating portion. From this perspective, the height from the groove bottom to the apex of the non-protrusion portion 24b of the mating portion (for example, the distance t1 from the groove bottom to the line segment passing horizontally through the apex of the non-protrusion portion 24b as shown in Figure 8(b)) is preferably 5.5 to 10 mm.

The lid wall, groove bottom, and mating inner wall thus form an annular recess (e.g., annular recess R in Figure 7). Furthermore, in the present invention, to increase the strength of the annular recess, it is preferable to provide annular ribs on both the inner and outer edges of the groove bottom, each of which is formed with downwardly projecting ridges and a smokeless edge running circumferentially. Such annular ribs can be represented, for example, as inner annular rib 23a and outer annular rib 23c in Figure 3. Therefore, when such annular ribs are provided, the groove bottom structure, as shown in Figure 3, is arranged in the following order from the contents side: inner annular rib 23a, groove bottom horizontal portion 23b, and outer annular rib 23c.

It is also preferable that the upper wall of the lid has an inwardly bulging recess for stacking (e.g., recess 27 in Figure 3). It is preferable that such a recess is formed integrally with the cutout portion (cutout portion 21b in Figure 3) as shown in Figure 3.

The size of the lid 2 can be selected appropriately to match the container body, but if it is circular in plan view, the length between the mating outer walls in the diameter direction (e.g., diameter W1 in Figure 6) can be in the range of 140 to 200 mm, and the diameter of the top surface (e.g., diameter W2 in Figure 6) can be in the range of 100 to 170 mm. Furthermore, the width in the height direction of the lid 2 (e.g., height T1 in Figure 6) is preferably in the range of 11 to 60 mm.

When the lid body 2 is elliptical in plan view, the length between the mating outer walls in the diameter direction is preferably 150 to 300 mm in the major axis direction and 100 to 200 mm in the minor axis direction, and the width in the height direction of the lid body 2 (for example, height T1 in Figure 6) is preferably in the range of 11 to 60 mm.

The lid can be made of a synthetic resin sheet, such as polystyrene, polypropylene, polyethylene, or other polyolefins, that is heat-resistant and suitable for use in a microwave oven.

These sheet materials can also be made from the aforementioned synthetic resins with inorganic materials dispersed therein, or stretched sheets obtained by stretching the aforementioned sheets. Among these, uniaxially or biaxially stretched sheets of polystyrene, polypropylene, etc. are particularly preferred because they also have the heat resistance required for microwave heating. Stretched polypropylene sheets are particularly preferred because they have excellent oil resistance and heat resistance, as well as good moldability and the ease with which they can be formed into slit valves.

The paper container body 1 used in the present invention is a paper container body having an opening at the top, and essential components including a curled opening end with the upper edge curled outward, a body, and a bottom. The planar shape of the opening is circular or oval, just like the lid, and the shape can be selected appropriately depending on the contents to be stored. The paper container body 1 can store a variety of foods, such as gratin, doria, pasta, curry, pilaf, pho, soup, and prepared dishes, but a circular shape is preferable, especially when used as a container for single-serving gratin or doria.

Furthermore, since thin containers are the norm for gratin and doria, a shallow cylindrical container is preferable.

Here, the curled opening edge located at the opening of the paper container body 1 has a shape that is curled outward, and may be partially curled, semi-rolled, or curled outward one or more times. However, a shape that is curled outward one or more times is preferred, as this increases the rigidity of the curled opening edge itself, ensures the fitting strength when the lid is fitted, and effectively prevents heated steam from entering the fitting portion.

The body portion extending from the curled opening end is preferably formed into a cylindrical shape, with an oil-resistant film laminated to its inner surface. In this case, the laminate film is preferably laminated to a paper substrate before being used to form the container, and therefore it is preferably laminated continuously onto the surface of the curled opening end.

The bottom of the paper container body 1 has a shape similar to the shape of the opening.
Here, it is preferable that the inner diameter of the opening of the paper container body 1 is slightly wider than the diameter of the bottom, as this provides excellent container strength and makes it easier to grip after cooking. Specifically, the ratio of the opening inner diameter (D12) to the bottom diameter (D11) [(D12)/(D11)] is preferably in the range of 1.01 to 1.2. That is, the body preferably has an inverted truncated cone shape that widens upward. The opening inner diameter (D12) refers to the length of the line segment connecting the straight line on the wall surface in the cross section of the paper container 1 to the inflection point that continues to the curled opening end in the diameter direction.

As mentioned above, the paper container body 1 is preferably a shallow cylindrical container, and in this case, it is preferable that the ratio of the bottom diameter (D11) to the height (H12) [(H12)/(D11)] is 0.2 to 0.6.
Furthermore, in the present invention, it is preferable that the bottom 11 of the paper container body 1 is configured as an upper bottom from the viewpoint of heating efficiency during microwave cooking, and in this case, it is preferable that the height (H11) of the upper bottom is in the range of 0.1 to 0.3 in terms of the ratio [(H11)/(H12)] to the height (H12) of the paper container body 1.

The paper container body 1 may also be a bottomless paper cylinder with a curled opening end and a body, with a bottomed resin inner container that covers the inside fitted at the curled opening end.

<Implementation>
This embodiment uses a cylindrical paper container body 1 shown in Figure 1 as the container body, and essential components include a bottom 11, a body 12, and a curled opening end 13. Here, the body 12 is folded to have an upwardly expanding inverted truncated cone shape, as shown in Figure 2, and the ratio of the opening inner diameter (D12) to the bottom diameter (D11) [(D12)/(D11)] is 1.05. Furthermore, as shown in Figure 9, the curled opening end 13 has an outwardly wound shape that wraps around more than once. The bottom 11 is formed in an upside-down shape as shown in Figure 2, and the ratio [(H11)/(H12)] to the height (H12) of the paper container body 1 is 0.15.

Next, as shown in Fig. 3, the lid 2 has a top surface 21, a lid wall surface 22 hanging down from the outer edge of the top surface 21, a groove bottom 23 extending outward from the lower end of the lid wall surface, and a fitting portion 24 continuing from the outer edge of the groove bottom 23 and clamping the side wall of the cylindrical paper container. The fitting portion 24 has a fitting inner wall 24a extending upward from the outer edge of the groove bottom and abutting the inner wall surface of the container, an annular fitting upper portion covering the curled opening end, and a fitting outer wall 24d extending downward from the outer edge of the annular fitting upper portion and abutting the upper part of the outer wall of the container. In other words, as shown in Fig. 9, the curled opening end of the paper container body 1 has a structure in which the fitting portion 24 is fitted from the inside and outside, thereby exhibiting excellent fitting strength and effectively preventing the intrusion of heated steam from the contents into the vicinity of the curled opening end during cooking. 7, the cover wall surface 22, the groove bottom 23, and the fitting inner wall 24b form an annular recess R, and by making this recess deep enough, the height of the fitting portion 24 is increased, effectively preventing the intrusion of heated steam into the vicinity of the curled opening end. For this reason, in this embodiment, the fitting portion height (t1) in FIG. 8(b) is 7.7 mm.
Furthermore, the upper annular fitting portion is provided with elongated ridges 24c which are arranged at intervals along the circumferential direction of the annular structure.

In this embodiment, the convex protrusion is generally rectangular in plan view, with a long base side (convex protrusion length (a)) of 3 mm, a long top side (b) of 5 mm, and a short side (convex protrusion width (d)) of 1 mm in plan view. The height from the base to the top (convex protrusion height (h)) is 1 mm.

Furthermore, the convex protrusions are arranged at equal intervals in the circumferential direction, and the length between two convex protrusions, i.e., the length of the non-protrusion portion 24b (gap length (c) in Figure 5), is 2.3 mm.

The annular fitting portion has a diametric width (fitting portion width (w)) of 3.6 mm.

In the present invention, as described above, the convex protrusion is located on the upper surface of the lid fitting portion, but it is preferable to position it as far outward as possible from the standpoint of preventing the intrusion of heated steam. In this embodiment, the midpoint of the convex protrusion width (d) is located outside the midpoint of the fitting portion width (w), and further, the ratio of the convex protrusion width (d) to the fitting portion width (w) [(d)/(w)] is 0.28.

The lower end of the fitting outer wall 24d further encloses the upper side wall of the paper container body, more specifically, the lower end is positioned lower than the curled opening end, bends inward in cross section, narrows the curled edge, and connects to a skirt portion 25a. The skirt portion has a fitting locking portion 25b that protrudes inward like a convex strip to further strengthen the internal and external fitting of the lid body of the present invention and ensure a secure attachment with a click feeling when the lid body is fitted. The fitting locking portion 25b is arranged in the circumferential direction of the outer edge of the lid body 2 with a fitting locking portion width _W25b of 40 mm.

In order to prevent cuts when touching the hand, although not shown, the end of the skirt (skirt end 26 in Figures 3, 8, and 9) has a continuous, finely textured pattern.

In addition, the outer edge of the top surface 21 has butt-shaped ridges 21a formed intermittently with cutouts 21b. This increases the strength of the butt-shaped ridges themselves and effectively prevents the top surface 21 from buckling due to external forces. In this embodiment, the cutouts 21b are formed integrally with the stack recess 27.
Here, the height (t2) of the butt-shaped ridge portion 21a is 1 mm, and the radius of curvature Re thereof is 0.6 mm.

In addition, in this embodiment, the steam vents 30 formed on the top surface are provided with four C-shaped notched valves, as shown in Figure 3.

Furthermore, in this embodiment, the groove bottom 23 has downwardly projecting annular ribs formed with smokeless ends in the circumferential direction on both the inner and outer edge sides of the groove bottom 23. As shown in Figure 3, the inner annular rib can be represented as the inner annular rib 23a, and the outer annular rib 23c. The groove bottom has a structure in which, from the contents side, the inner annular rib 23a, the groove bottom horizontal portion 23b, and the outer annular rib 23c are arranged in this order, as shown in the end views of Figures 8 and 9.

In this embodiment, the lid body 2 described above can be obtained by molding oriented polypropylene.

The state in which the paper container body 1 and lid 2 are fitted together can be seen in the perspective view of Figure 10. As shown in Figure 9(a), which is the A-A cross section of Figure 4, and Figure 9(b), which is the B-B cross section, the fitting portions 24a and 24d of the lid 2 are in tight, constricting contact with the curled opening end 13. Furthermore, the convex protrusion 24c forms a gap between itself and the upper end of the curled opening end 13, contributing to temperature mitigation of the heated steam.

The present invention will be explained below using examples and comparative examples, but the present invention is not limited to these examples.

Example 1
A paper container shown in Fig. 1 and a lid body shown in Fig. 3 obtained by molding an oriented polypropylene sheet were prepared. These paper containers and lid body have the shapes shown in the above embodiment.
Next, the test doria food was placed in the paper container, and the lid was closed and fitted.
In this case, it was confirmed that skilled operators could close the lid securely due to the clicking sensation when closing it.
Next, it was heated in a 1500W microwave oven for 70 seconds, and the surface temperatures of the ridge projections 24c and the skirt end portion 26 were measured with a thermometer immediately after heating.
Furthermore, the surface temperatures of 24c and 27 were measured 30 seconds and 60 seconds after the end of heating.
The results are shown in Table 1.

Comparative Example 1
A lid having the same shape as in the above embodiment, except that it did not have the ridge protrusion 24c on the upper fitting portion, was used, and a heating test was conducted in the same manner as in Example 1. The surface temperatures of the upper fitting portion and the end of the skirt were measured immediately after heating, 30 seconds after heating, and 60 seconds after heating was completed. The results are shown in Table 1.

From the above results, it can be seen that when cooking in a microwave oven using the lid of the present invention, the temperature of the upper part of the fitting portion is suppressed immediately after heating, and the temperature subsequently drops rapidly.
Also, the temperature rise at the end of the skirt is suppressed immediately after heating, and the temperature then drops rapidly.

1: Paper container body 11: Bottom 12: Body 13: Curled opening end 2: Lid 21: Top surface 21a: Thread-tail-shaped convex rib portion 21b: Missing portion 22: Lid wall surface 23: Groove bottom 23a: Inner edge side annular rib 23b: Groove bottom horizontal portion 23c: Outer edge side annular rib 24: Fitting portion 24a: Fitting inner wall 24b: Non-protrusion portion 24c: Convex rib protrusion portion 24d: Fitting outer wall 25a: Skirt portion 25b: Fitting locking portion 26: Skirt end portion 27: Stacking recess 30: Steam hole a: Convex rib protrusion length b: Non-convex rib portion circumferential length c: Gap length d: Convex rib protrusion width t1: Fitting portion height t2: Thread-tail-shaped convex rib height T1: Lid height h: Convex rib protrusion height R: Annular recess w: Fitting portion width W _25b: Width of fitting engagement part W1: Length between fitting outer walls W2: Diameter of top surface

Claims (3)

A lid for a cylindrical paper container having an opening at the top and a curled opening edge at the top,
The container has a top surface , a lid wall surface hanging down from the outer edge of the top surface , a groove bottom portion extending outward from the lower end of the lid wall surface , and a fitting portion continuing from the outer edge of the groove bottom portion and clamping the side wall of the cylindrical paper container,
the fitting portion has a fitting inner wall extending upward from the outer edge of the groove bottom portion and abutting against the inner wall surface of the container, an annular fitting upper portion covering the curled opening end , and a fitting outer wall extending downward from the outer edge of the annular fitting upper portion and abutting against the upper portion of the outer wall of the container,
the annular fitting upper portion has a shape in which convex ridge protrusions and non-convex ridge portions are alternately arranged along the circumferential direction in a plan view,
the center of the width (d) of the convex ridge protrusion is located outward from the center of the width (w) of the annular fitting upper portion, and the portion of the annular fitting upper portion that is more inward than the convex ridge protrusion in plan view is a non-convex ridge portion;
The non-protruding portion is continuous with the fitting inner wall and the fitting outer wall, and has a shape that follows the curled opening end and abuts against the curled opening end . The lid according to claim 1 , wherein the ridge projection has a generally trapezoidal shape in a circumferential cross section and a generally rectangular shape in a plan view. 3. The lid according to claim 1 , wherein the bottom of the groove has downwardly convex annular ribs on its inner and outer edges .