Lid

Abstract

To provide a lid body capable of efficiently warming food product.SOLUTION: A lid body 1 includes a circular top surface part 2. The top surface part 2 includes linear ribs 3 and triangle regions 4. The linear rib 3 protrudes to a rear surface 26, and expands radially from a center of the top surface part 2 toward an outer peripheral edge. The triangle region 4 is defined by the linear ribs 3, the plurality of the triangle regions are arranged along a circumferential direction of the top surface part 2, a center side corner part 41, which is one corner, is directed toward the center of the top surface part 2, and an outer surface 25 is flat.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a lid that covers a container containing food.

Background Art

[0002] In recent years, cooked foods intended to be heated in a microwave oven are displayed and sold at convenience stores and the like. These foods are contained in disposable containers compatible with microwave heating, and are contained and heated in the microwave oven without being taken out of the container.

[0003] Foods containing a large amount of liquid such as soup, such as ramen, soba, and udon, have heat convection in the liquid and tend to have a uniform temperature after heating in a microwave oven. However, pilaf, doria, gratin, risotto, and some frozen foods have less liquid components such as soup compared to ramen and the like. Therefore, in order to minimize the remaining cold parts in these foods, a relatively long heating time in a microwave oven is recommended.

[0004] In response to long-time heating in a microwave oven, these foods are often sold in disposable containers, which are shallow cylindrical paper containers with excellent heat resistance. The lid of the paper container is often made of transparent and heat-resistant plastic in order to enhance the internal visibility. The lid has a circular shape with a flat entire top surface in order to enable stacking and display of foods. Hereinafter, the lid having a circular shape with a flat entire surface is referred to as a conventional lid.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, pilaf, doria, gratin, risotto, and some frozen foods often have uneven temperatures even after being heated in a microwave for a long time. In particular, many users have experienced the bottom center of these foods remaining cold.

[0007] Figure 8 is a thermographic image of gratin placed in a container made of a paper container and a conventional lid, after being heated in a microwave oven. As Figure 8 shows, when heated in a microwave oven, the outer peripheral region E1 is the highest temperature region within the space enclosed by the conventional lid 300 and the container body 100. When the lid is closed with the conventional lid 300, the heat in the outer peripheral region E1 remains in the outer peripheral region E1 and does not contribute to the temperature rise of the food. Therefore, the outside of the food, which is close to the outer peripheral region E1, heats up easily, but the center bottom of the food remains cold.

[0008] In conventional containers, the lid 300 is often made using sheet molding, and from the perspective of stacking and display, the entire outer surface of the top is made flat, resulting in the entire underside of the top surface also being flat. With such conventional lids 300, during heating in a microwave oven, the container body detaches due to the increase in internal pressure, causing heat to escape. Furthermore, conventional lids 300 are not dome-shaped but bulge in an irregular shape in some parts, resulting in an internal structure that does not efficiently circulate the heat from the outer circumference E1.

[0009] This invention was proposed to solve the problems of the prior art described above, and its purpose is to provide a lid that can efficiently heat food. [Means for solving the problem]

[0010] To achieve the above objective, an embodiment of the present invention is a lid that is placed over a container containing food to be heated in a microwave oven, and comprises a circular top surface, the top surface having a plurality of linear ribs that protrude from the back surface of the top surface and spread radially from the center of the top surface toward the outer edge, and a plurality of triangular regions defined by the linear ribs and arranged along the circumferential direction of the top surface, with one corner facing toward the center of the top surface and having a flat outer surface.

[0011] The triangular region may extend to the periphery of the top surface.

[0012] The aforementioned triangular region may extend smoothly without any steps from the peripheral wall of the top surface to one of the corners pointing toward the center of the top surface.

[0013] The top surface may have annular ribs that extend from the peripheral wall of the top surface and extend endlessly around the circumference of the top surface.

[0014] The outer periphery of the top surface may have a smaller diameter than the rim of the container and may further include a fitting portion that surrounds the outer circumference of the top surface and fits onto the rim of the container.

[0015] The aforementioned triangular region may have an equilateral triangle shape. [Effects of the Invention]

[0016] According to the present invention, the dome-shaped expansion of the lid causes heat convection to occur from the outer periphery through the apex of the lid to the center bottom of the container body, thereby efficiently heating the food. [Brief explanation of the drawing]

[0017] [Figure 1] This is a perspective view of the container. [Figure 2] This is a plan view showing the outer surface of the lid. [Figure 3] This is a cross-section of the lid. [Figure 4] This is a perspective view showing the underside of the lid. [Figure 5] This is a cross-sectional view showing heat convection near the lid while heating in a microwave oven. [Figure 6] This is a perspective view of the underside showing the heat convection near the lid during microwave heating. [Figure 7] This shows a thermographic image of the lid of the present invention after heating in a microwave oven. [Figure 8] It shows the thermography of the conventional lid after heating in a microwave oven.

Embodiments for Carrying out the Invention

[0018] (Configuration) The lid according to an embodiment of the present invention will be described in detail while referring to the drawings. In each drawing, for ease of understanding, the thickness, dimensions, positional relationship, ratio, shape, etc. may be emphasized and shown, and the present invention is not limited to those emphases. Hereinafter, when the lid covers the container body, the side of the container body is referred to as the lower side or the bottom side, the top surface side is referred to as the upper side or the top side, and the direction in which the lid extends orthogonal to the vertical direction is referred to as the radial direction.

[0019] FIG. 1 is a perspective view of a container 200. The container 200 contains food to be warmed in a microwave oven. Examples of the food contained in the container 200 include dishes such as doria, gratin, or risotto with a small amount of liquid components such as soup. The food is placed in the microwave oven and warmed while being contained in the container 200.

[0020] This container 200 includes a container body 100 and a lid 1. The container body 100 has a bottom and a wide opening and contains food. The lid 1 is mounted so as to cover the container body 100 and closes the opening of the container body 100. The lid 1 remains covering the container body 100 during heating by the microwave oven. The container body 100 is made of paper, and the mouth edge is curled outward in the radial direction to form a flange. The lid 1 has a fitting portion 6 at its outermost periphery, and by fitting the fitting portion 6 onto the curled mouth edge, it is detachably attached to the container body 100.

[0021] Figure 2 is a plan view showing the outer surface 25 of the lid 1. Figure 3 is a cross-sectional view of the lid 1. As shown in Figures 2 and 3, the lid 1 is manufactured by sheet molding using a plastic sheet such as polypropylene. The lid 1 is circular in top view and has a top surface 2, annular ribs 5, and a fitting portion 6 arranged concentrically from the center of the circle toward the outer circumference. The top surface 2, annular ribs 5, and fitting portion 6 are integrally formed by sheet molding, connecting them seamlessly in one piece.

[0022] The top surface 2 is located in the innermost shell, including the center of the lid 1, and has a slightly smaller diameter than the lid 1. This top surface 2 comprises a top surface 21 and a peripheral wall 22. The top surface 21 is a roughly circular region that extends radially and extends along the horizontal plane. The peripheral wall 22 extends endlessly around the periphery of the top surface 21. It extends downward from the periphery of the top surface 21 as its base. The boundary 23 between the top surface 21 and the peripheral wall 22 is smoothly curved.

[0023] The outer surface 25 of the top surface 21 has concave grooves 24 that extend radially from the center of the top surface 2 towards the periphery. Apart from these grooves 24, the outer surface 25 of the top surface 21 is a flat area without any irregularities or bulges that extends horizontally.

[0024] Figure 4 is a perspective view showing the back surface 26 of the lid 1. As shown in Figures 3 and 4, linear ribs 3 are formed on the back surface 26 of the top surface 21. The back surface 26 of the top surface 21 is the surface opposite to the outer surface 25 and is the surface enclosed by the top surface 21 and the peripheral wall 22. The linear ribs 3 correspond to the concave grooves 24 that appear on the outer surface 25 and protrude from the back surface 26 of the top surface 21. The linear ribs 3 spread radially from the center of the top surface 21 toward the outer edge. For example, six linear ribs 3 spread out at 60-degree intervals and equidistant around the circumference.

[0025] Each linear rib 3 converges before reaching the center of the top surface 21, and a collective bulge 31 is formed at the center of the back surface 26 of the top surface 21. The collective bulge 31 bulges out from the back surface 26 of the top surface 21, has an expansion along the back surface 26 of the top surface 21, and forms a circular spur gear shape. The side surface 31a of the collective bulge 31 is inclined toward the center of the top surface 21. Furthermore, the side surface 31a is smoothly curved so as to be concave toward the center of the top surface 21. Note that the side surface 31a is located between adjacent linear ribs 3.

[0026] Each linear rib 3 extends from the collective bulge 31 toward the periphery of the top surface 21, and the end 32 of each linear rib 3 is connected to the peripheral wall 22 of the top surface 2. This end 32 is the tip of the linear rib 3 opposite to the collective bulge 31. Just before connecting to the peripheral wall 22, the end 32 spreads out in a smooth fan shape along the back surface 25 of the top surface 21 before connecting to the peripheral wall 22.

[0027] The linear ribs 3, the aggregate bulge 31, and the peripheral wall 22 define triangular regions 4 on the top surface 21. Therefore, the triangular regions 4 are aligned along the circumference of the top surface 21. When the linear ribs 3 extend radially at 60-degree intervals, each triangular region 4 has an equilateral triangle shape, and there are six such regions along the circumference of the top surface 21.

[0028] The central corner 41, one of the corners of the triangular region 4, is formed by the side surface 31a of the aggregate bulge 31 and faces the center of the top surface 21. The base 42 of the triangular region 4 is the boundary 23 between the top surface 21 and the peripheral wall 22, and the inner surface 43 of the triangular region 4 is smoothly connected from the boundary 23 to the central corner 41 without any steps or irregularities. Furthermore, the triangular region 4 narrows from the boundary 23 towards the central corner 41.

[0029] As shown in Figure 3, the annular rib 5 is connected to the lower end of the peripheral wall 22 of the top surface 2 and endlessly surrounds the outer circumference of the top surface 2. The annular rib 5 has an outer diameter identical to the inner diameter of the container body 100, bulges downward, and fits inside the container body 100.

[0030] The fitting portion 6 is located radially outward from the top surface portion 2 and the annular rib 5, and after expanding radially outward by the thickness of the rim of the container body 100, it bends and extends downward so as to hook onto the lower end of the rim.

[0031] (when heated) Before heating such a container 200 in a microwave oven, the outer surface 25 of the top surface 21 of the lid 1 is flat except for the groove 24. Therefore, multiple containers 1 containing food can be stacked vertically and displayed in a store.

[0032] Figure 5 is a cross-sectional view showing the thermal convection near the lid 1 during microwave heating, and Figure 6 is a rear perspective view showing the thermal convection near the lid 1 during microwave heating. In Figure 6, for the sake of the drawing, the convection C is depicted as being limited to a single triangular region 4.

[0033] As shown in Figures 5 and 6, when heated in a microwave oven, the outer peripheral region E1 of the lid 1 and container body 100 is heated most, just as with a conventional lid 300. However, because the lid 1 has triangular regions 4 demarcated by linear ribs 3, the airflow around the lid 1 is rectified, and convection C occurs, guiding the heat from the outer peripheral region E1 to the center of the top surface 2. The linear ribs 3 prevent the heat convection C from leaking into the adjacent triangular region 4, and the convection is smoothly guided to the center of the top surface 2.

[0034] Since the base 42 of the triangular region 4 extends to the peripheral wall 22, the triangular region 4 efficiently absorbs heat from the outer peripheral region E1 and, together with the linear ribs 3, collects convection C toward the central corner 41. This base 42 is arc-shaped with the central corner 41 as its center and is integrated with the boundary 23 which is curved from the vertical to the horizontal direction. Therefore, the triangular region 4 absorbs heat from the outer peripheral region E1 even more efficiently. Furthermore, the back surface 26 of the triangular region 4 is smooth throughout and has no steps, so the heat absorbed from the outer peripheral region E1 is easily guided to the triangular region 4 and concentrated toward the central corner 41.

[0035] As a result, convection C is generated near the top surface 2, from the outer peripheral region E1 to the central region E2 of the top surface 2. This convection accumulates in the central region E2, which becomes hot and high-pressure. Consequently, the top surface 2, which was flat except for the groove 24 before heating in the microwave oven, bulges out into a dome shape with the central region E2 as its apex.

[0036] Here, since annular ribs 5 are formed around the outer circumference of the top surface 2, the outer edge of the top surface 2 is relatively resistant to deformation. Also, the top surface 2 has a smaller diameter than the lid 1, and the fitting portion 6 is located outside the top surface 2. Therefore, the central area E2 of the top surface 2 becomes relatively higher pressure than the outer area E1, and when the lid 1 tries to be pushed up by the pressure, the fitting portion 6 bites into the container body 100 more strongly, reducing the force that would cause the lid 1 to come off. As a result, distorted changes in the top surface 2 and the detachment of the lid 1 are suppressed, and the dome-shaped changes of the top surface 2 are facilitated.

[0037] The dome-shaped change of the top surface 2 further promotes convection C from the outer region E1 to the central region E2. Figure 7 shows a thermograph of the lid 1 after heating in a microwave oven. Comparing Figure 7 with Figure 8, which is a thermograph of a conventional lid 300, it can be seen that in the thermograph of Figure 7, the central region E2 is hotter than the outer region E1, and convection C occurs, where the heat from the outer region E2 is concentrated in the central region E2.

[0038] The heat accumulated in the central region E2 due to the dome-shaped change of the top surface 2 is converted into a downward flow from the central region E2 towards the central bottom E3 of the container body 100. This high-temperature downward flow also warms the center of the bottom of the food contained in the container body 100. The top surface 2 is provided with a collection bulge 31, and the inclined and curved side surface 31a forms the central corner 41 of the triangular region 4. Therefore, the convection C accumulated in the central region E2 slides along the central corner 41 and easily becomes a downward flow.

[0039] (Effects and Benefits) As described above, the lid 1 is provided with a circular top surface 2. The top surface 2 has linear ribs 3 and triangular regions 4. The linear ribs 3 protrude from the back surface 26 and spread radially from the center of the top surface 2 towards the outer edge. The triangular regions 4 are defined by the linear ribs 3 and are arranged in multiple rows along the circumference of the top surface 2, with one of the corners, the central corner 41, facing the center of the top surface 2, and the outer surface 25 is flat.

[0040] This allows containers 200, each containing food and covered with a lid 1, to be stacked and displayed. Furthermore, the lid 1 expands into a dome shape when heated in a microwave oven, creating heat convection from the outer periphery E1 to the central region E2 including the lid's apex. Additionally, a downward flow from the central region E2 towards the central bottom E3 of the container body 100 efficiently heats the food.

[0041] The triangular region 4 is designed to extend to the periphery of the top surface 2. This allows heat to be efficiently drawn in from the high-temperature outer region E1 and guided to the central region E2. Because this triangular region 4 extends smoothly without any steps from the peripheral wall 22 of the top surface 2 to the central corner 41, the heat convection C flowing through the triangular region 4 is smoothly guided to the central region E2.

[0042] The top surface 2 has an annular rib 5 that extends from the peripheral wall 22 of the back surface 26 of the top surface 2 and extends endlessly around the circumference of the top surface 2. The annular rib 5 increases the relative strength of the outer edge of the top surface 2 compared to the center of the top surface 2, making the top surface 2 more prone to bulging into a dome shape.

[0043] The outer edge of the top surface 2 has a smaller diameter than the rim of the container 200, and is further provided with a fitting portion 6 that surrounds the outer circumference of the top surface 2 and fits onto the rim of the container 200. As a result, when the top surface 2 tries to lift up due to the pressure inside the container 200, the fitting portion 6 bites into the rim, preventing the lid 1 from coming off.

[0044] Furthermore, the embodiments and examples of the present invention are presented as examples only and are not limited to the above embodiments and examples. The above embodiments and examples can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiments, examples, and their variations are included within the scope of the present invention.

[0045] For example, the triangular regions 4 may be arranged in groups of six to form an equilateral triangle. Alternatively, the triangular regions 4 may be arranged in groups of seven or more to form an isosceles triangle with a narrower central angle 41 than that of an equilateral triangle. Alternatively, the triangular regions 4 may be arranged in groups of five or fewer to form an isosceles triangle with a wider central angle 41 than that of an equilateral triangle.

[0046] However, triangular regions 4 with an equilateral triangle shape are more likely to concentrate heat in the central region E2 without leaking heat convection C to adjacent triangular regions 4, compared to triangular regions 4 arranged in groups of seven or more. This facilitates downward flow from the central region E2 to the central bottom E3, making it easier to heat the central bottom of the food.

[0047] Furthermore, a lid 1 with a series of triangular regions 4 having an equilateral triangle shape has higher strength in its top surface 21 and is more likely to form a well-defined dome shape that facilitates the rectification of convection C from the outer peripheral region E1 to the central region E2, compared to a lid 1 with five or fewer triangular regions 4 arranged in a series. [Explanation of Symbols]

[0048] 1 Lid 2 Top section 21 Top surface 22 Peripheral wall 23 Boundary 24 groove 25 External surface 26 Back side 3 Linear ribs 31 Collective bulge 31a side 32 End 4 Triangular area 41 Center side corner 42 Bottom 43 Inner surface 5. Annular ribs 6. Fitting part 100 Container body 200 containers C Convection E2 central area E3 center bottom

Claims

1. A lid that is placed over a container containing food that can be heated in a microwave oven, It has a circular top surface, The top portion is Multiple linear ribs protrude from the back surface of the top surface and radiate outwards from the center of the top surface towards the outer edge, The aforementioned top surface portion comprises a cluster of bulges that bulge out from the back surface and center, The linear ribs define a series of triangular regions that are arranged along the circumferential direction of the top surface, with one corner facing the center of the top surface, and the outer surface is flat. Having A lid characterized by the following features.

2. The aforementioned triangular region extends to the periphery of the top surface. The lid according to claim 1, characterized by the following:

3. The aforementioned triangular region extends smoothly without any steps from the peripheral wall of the top surface to one of the corners pointing toward the center of the top surface. The lid according to claim 2, characterized by the following:

4. The top surface portion has annular ribs that extend from the peripheral wall of the top surface portion and extend endlessly around the circumference of the top surface portion. A lid according to any one of claims 1 to 3, characterized by the following:

5. The outer edge of the top surface is smaller in diameter than the rim of the container. The lid further comprises a fitting portion that surrounds the outer periphery of the top surface and fits onto the rim of the container. A lid according to any one of claims 1 to 4, characterized by the above.

6. The aforementioned triangular region has an equilateral triangular shape. A lid according to any one of claims 1 to 5, characterized by the following:

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