Hinge-capped case

Abstract

To provide a hinge-capped case having a small gap of a fit portion in appearance while being formed with a thin thickness.SOLUTION: A resin hinge-capped case includes a bottom material and a lid material both of which are in a generally rectangular-tray form to fit with each other. In the case, at least one of the bottom material and the lid material satisfies [1] or [2] in the following. [1] When viewed laterally from a side of a long side with laid on a plane such that an inner side is face down, a central part in a right-left direction is raised upper than at least one end and an amount of deformation in a direction perpendicular to the plane is given in a range of 0.5% or less of a length in a long-side direction of a rectangle. [2] When viewed laterally from a side of the long side with laid on a plane such that the inner side is face down, at least one end in a right-left direction is raised upper than the central part.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a case with a hinge cap.

Background Art

[0002] Conventionally, a case with a hinge cap for containing cooling granules or the like and using them in small amounts has been known (for example, Patent Documents 1 and 2). These are card-type cases in which a tray-shaped bottom member and a lid member are fitted to each other, and have a structure in which a hinge cap integrally formed with the bottom member can be opened and closed. These have the characteristics of having a small number of parts, being low-cost, having excellent portability, and having high pressure resistance.

[0003] The above-mentioned case with a hinge cap is made of resin. In recent years, there has been a social demand to reduce the use of resin in consideration of the environment. Here, when trying to mold a resin product into a thin plate shape by injection molding, a phenomenon may occur in which the resin material does not reach the flow end of the cavity (hereinafter referred to as "short shot"). In Patent Document 3, a proposal has been made to solve this problem.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, when manufacturing a molded body designed to be thin-walled using resin, in addition to the problem of short shots, there is also a problem that the molded body is likely to warp. The same applies to the case with the hinge cap described above. Due to the thinning associated with the reduction in the amount of resin used, warping is likely to occur in each of the bottom member and the lid member. When fitting the warped bottom member and lid member together, a large gap is generated in the fitting portion (side peripheral surface) in terms of appearance, which may have an adverse effect on the quality of the cooling granular material etc. inside. Therefore, an object of the present invention is to provide a case with a hinge cap that is molded into a thin wall while having a small gap in the fitting portion in terms of appearance.

Means for Solving the Problem

[0006] The present invention is a resin case with a hinge cap in which a bottom member and a lid member, both of which are substantially rectangular and tray-shaped, are fitted to each other. The rectangle has a length in the long side direction of 120 mm or less and a length in the short side direction of 70 mm or less. Both the bottom member and the lid member include a bottom plate portion and a side plate portion rising from the periphery of the bottom plate portion. The bottom member has a hinge cap on a part of the side plate portion. A boss is formed on the inner surface of the bottom plate portion of either the bottom member or the lid member, and a pin that fits into a boss hole of the boss is formed on the inner surface of the bottom plate portion of the other. At least one of the bottom member and the lid member has a thin-walled recess on the inner surface of the bottom plate portion. The thickness of the bottom plate portion in the part other than the thin-walled recess is 0.70 mm or less, and the thickness of the bottom plate portion in the thin-walled recess is 80% or less of the thickness of the bottom plate portion in the part other than the thin-walled recess. The present invention provides a case with a hinge cap in which at least one of the bottom member and the lid member satisfies the following [1] or [2]. [1] When lying flat on a plane with the inner surface side facing downward and viewed from the long side in side view, the central portion in the left-right direction is lifted upward more than at least one end portion, and the range of the amount of deformation in the direction perpendicular to the plane is 0.5% or less of the length of the rectangle in the long side direction. [2] When lying flat on a plane with the inner surface side facing downward and viewed from the long side in side view, at least one end portion in the left-right direction is lifted upward more than the central portion.

[0007] The case with a hinge cap of the present invention may further include at least one of the following features. · When satisfying the above [1], further, the range of the amount of deformation is 0.5 mm or less. · When satisfying the above [2], further, the range of the amount of deformation is 3% or less of the length in the long side direction of the rectangle, or 3 mm or less. · Both the bottom member and the lid member satisfy the above [1] or [2]. · The rectangle has a length in the long side direction of 70 mm or more and 120 mm or less, and a length in the short side direction of 40 mm or more and 70 mm or less.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a case with a hinge cap that is formed thin and has a small gap in the fitting portion in terms of appearance.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. The case with a hinge cap of the present embodiment is a card-type case for putting cooling granular materials or the like and using them in small portions.

[0011] <Case with hinge cap> As shown in FIGS. 1 to 3, the case 1 with a hinge cap of the present embodiment (hereinafter sometimes simply referred to as "case") is formed by fitting a tray-shaped bottom member 2 and a lid member 3 to each other. The case 1 is substantially rectangular (here, a rounded rectangle) in plan view, and has an opening 5 in a long side portion on one side. A hinge cap 22 is integrally formed on the bottom member 2 via a thin and bendable hinge 21, whereby the opening 5 can be closed. In this specification, the direction in which the bottom member 2 and the lid member 3 are fitted to each other is referred to as the "thickness direction", and any direction perpendicular to this is referred to as the "width direction".

[0012] As for the size of the case 1, the length in the long side direction of the rectangle is 120 mm or less, and the length in the short side direction is 70 mm or less. The length in the long side direction may be 110 mm or less, or may be 100 mm or less. The length in the short side direction may be 70 mm or less, may be 60 mm or less, or may be 50 mm or less. As the lower limit, the length in the long side direction may be 60 mm or more, may be 70 mm or more, or may be 80 mm or more. The length in the short side direction may be 30 mm or more, may be 40 mm or more, or may be 50 mm or more.

[0013] More specifically, the length in the long side direction of the rectangle may be 95 mm to 105 mm, and the length in the short side direction may be 45 mm to 55 mm. Also, the length in the long side direction of the rectangle may be 75 mm to 85 mm, and the length in the short side direction may be 45 mm to 55 mm.

[0014] The bottom member 2 and the lid member 3 are each substantially rectangular (rounded rectangle), but the portion forming the opening 5 is a recess that is recessed inward of the rectangle. Both the bottom member 2 and the lid member 3 have a bottom plate portion 23, 33 that extends in the width direction and side plate portions 24, 34 that rise and extend in the thickness direction from the periphery of the bottom plate portion 23, 33. The side plate portions 24, 34 are continuous along the periphery of the bottom plate portion 23, 33 except for the portion that becomes the opening 5 of the case 1.

[0015] On the inner surface of the bottom plate portion 23 of the bottom member 2, there are a total of seven bosses 25 (25a, 25b, 25c, 25d, 25e, 25f, 25g) formed at four locations near each of the four rounded portions, two locations along the two long sides and closer to the recess side forming the opening 5 than the center of the long side, and one location at the center in plan view. For example, as shown in FIG. 4(A), the boss 25g is a hollow cylinder protruding in the thickness direction, and the hollow portion becomes a boss hole by being partitioned by a partition wall (the wall forming the cylinder). The depth of the boss hole coincides with the height of the boss 25g. This structure is common to all the bosses 25. The thickness T 3 of the partition wall will be described later.

[0016] On the other hand, on the inner surface of the bottom plate portion 33 of the lid member 3, pins 35 (35a, 35b, 35c, 35d, 35e, 35f, 35g) are formed at positions corresponding to the bosses 25 (25a, 25b, 25c, 25d, 25e, 25f, 25g) formed on the bottom plate portion 23 of the bottom member 2. For example, as shown in FIG. 4(B), the pin 35g includes a base portion 35ga that rises from the bottom plate portion 33 and a tip portion 35gb that further protrudes and extends from the upper surface of the base portion 35ga. Inside the pin 35g, a cylindrical space is formed so as to penetrate the tip portion 35gb and the base portion 35ga, and its depth is the same as the height of the pin 35g. In the present embodiment, among the pins 35, only the pin 35g has the base portion 35ga, and the other pins 35 do not have a base portion, and a cylinder having a thickness corresponding to the tip portion 35gb protrudes. As another embodiment, all the pins 35 may have a base portion. Having a base portion makes it easier to ensure strength even when the thickness of the pin is thin.

[0017] The bottom member 2 has thin-walled concave portions 26, 26 with a reduced wall thickness. The thin-walled concave portions 26, 26 are formed in a rectangular shape extending in the long side direction at positions between the boss 25g located at the center in plan view and the long side of the side plate portion 24. The lid member 3 also has thin-walled concave portions 36, 36 formed in the same manner. These thin-walled concave portions 26, 36 correspond to material-removing portions for suppressing the occurrence of sink marks and warping in injection molding described later. The thickness of the thin-walled concave portions 26, 36 will be described later.

[0018] The total area of the thin-walled concave portions 26, 26 of the bottom plate portion 23 and the total area of the thin-walled concave portions 36, 36 of the bottom plate portion 33 may be 10% to 80%, may be 15% to 70%, or may be 20% to 60% with respect to 100% of the area of the inner surfaces of the bottom plate portions 23, 33 that extend in the width direction among the inner surfaces of the bottom member 2 and the lid member 3 (the total area of the portions with thin-walled concave portions and the portions without thin-walled concave portions).

[0019] 4(A) and (B), the side plate portion 24 of the bottom member 2 is provided with a raised portion 24a at its end along the inner circumferential surface. On the other hand, the side plate portion 34 of the cover member 3 is provided with a lowered portion 34a at its end along the inner circumferential surface. The raised portion 24a and the lowered portion 34a abut against each other to seal the bottom member 2 and the cover member 3 when the bottom member 2 and the cover member 3 are fitted together. In order to improve the sealability, engagement protrusions may be provided at the ends of the side plate portions 24, 34 at portions corresponding to the raised and lowered heights of the raised and lowered portions 24a and 34a, respectively.

[0020] The thickness of each part will be described. The thickness T of the part of the bottom plate part 23, 33 that is not the thin recessed part 26, 36 1 The thickness T is 0.70 mm or less. 1 may be 0.65 mm or less, 0.60 mm or less, 0.55 mm or less, 0.50 mm or less, 0.45 mm or less, 0.40 mm or less, or 0.35 mm or less. 1 The specific range of the thickness T of the thin recesses 26, 36 may be 0.50 mm to 0.70 mm, 0.55 mm to 0.65 mm, or 0.58 mm to 0.63 mm. 2 may be 0.40 mm or less, may be 0.35 mm or less, may be 0.30 mm or less, or may be 0.25 mm or less. 2 The specific range of may be 0.35 mm to 0.55 mm, 0.40 mm to 0.53 mm, or 0.44 mm to 0.52 mm. 2 is the thickness T of the portion other than the thin recesses 26 and 36 1 It is 80% or less, may be 75% or less, or may be 70% or less. 1 and T 2 If the thickness T of the thin recesses 26 and 36 is within these numerical ranges, then if a short shot occurs, it is likely to occur in the thin recesses.2 may be 40% or more, 50% or more, or 60% or more of the thickness T of the portion other than the thin concave portions 26 and 36. 1

[0021] Alternatively, the thickness T in the thin concave portions 26 and 36 2 may be 70% - 80%, 71% - 79%, or 72% - 78% of the thickness T of the portion other than the thin concave portions 26 and 36. By setting this value within the range of 70% - 80%, in addition to facilitating appearance inspection by guiding the occurrence position of short shots, the occurrence of short shots itself is likely to be suppressed. 1

[0022] The thickness T of the side plate portions 24 and 34 4 may be the same as the thickness T of the portion other than the thin concave portions 26 and 36 of the bottom plate portions 23 and 33, excluding the portion where the step - up portion 24a or step - down portion 34a is formed. Alternatively, the thickness T of the side plate portions 24 and 34 1 may be 110% - 180%, or 130% - 150% of the thickness T of the bottom plate portions 23 and 33, considering the formation of the step - up portion 24a or step - down portion 34a. Alternatively, the thickness T of the side plate portions 24 and 34 4 may be 250% - 350%, or 270% - 300% of the thickness T of the bottom plate portions 23 and 33, considering the formation of the step - up portion 24a or step - down portion 34a. The specific range of the thickness T 1 may be 1.50 mm - 2.00 mm, 1.60 mm - 1.90 mm, or 1.65 mm - 1.80 mm. 4 1 4

[0023] The thickness T of the side plate portion 34 of the lid member 3 4 may be thinner than the above numerical range, for example, 0.4 mm - 1.5 mm, or 0.5 mm - 1.2 mm. It is preferably thinner than the thickness T of the side plate portion 24 of the bottom member 2. For example, the thickness T of the side plate portion 34 of the lid member 3 4 4is 0.6 mm to 1.0 mm, and the thickness T of the side plate portion 24 of the bottom member 2 4 is 1.5 mm to 1.9 mm. The thinner the side plate portions 24 and 34 are, the more easily they are affected by the warping deformation of the bottom plate portions 23 and 33, and the more easily they deform together with the warping deformation of the bottom plate portions 23 and 33. This deformation also affects the appearance of the side circumferential surface of the case 1 after fitting, and also causes the gap of the fitting portion in appearance to become large.

[0024] In the boss 25g, the thickness T of the partition wall that partitions the inside and outside of the boss hole 3 may be 0.60 mm to 1.00 mm, may be 0.60 mm to 0.90 mm, may be 0.80 mm to 0.90 mm, or may be 0.60 mm to 0.80 mm. Further, the thickness T of the partition wall 3 is the thickness T of the portion of the bottom plate portion 23 that is not the thin-walled concave portion 26 1 may be 90% to 150%, may be 100% to 140%, or may be 110% to 130%. Note that this value is the same for bosses 25 other than the boss 25g.

[0025] As the resin constituting the bottom member 2 and the lid member 3, a thermoplastic resin is preferable, and particularly, a polypropylene resin and a polyethylene resin are preferable. The preferable melt flow rate of the thermoplastic resin will be described in the item of the manufacturing method described later.

[0026] At least one of the bottom member 2 and the lid member 3 satisfies the following [1] or [2]. [1] When lying flat on a plane with the inner surface side facing downward and viewed from the long side in side view (see FIG. 5(A)), the central portion in the left-right direction is lifted upward from at least one end portion (see FIG. 5(B). A so-called "convex upward" state), and the range of the deformation amount in the direction perpendicular to the plane is 0.5% or less of the length in the long side direction of the rectangle. [2] When lying flat on a plane with the inner surface side facing downward and viewed from the long side in side view (see FIG. 5(A)), at least one end portion in the left-right direction is lifted upward from the central portion (see FIG. 5(C). A so-called "convex downward" state.)

[0027] Here, the "central part" refers to the area between both ends and is the part that is the maximum point of the warped shape. Also, the "range of deformation amount" refers to the height difference between the part where the height of the warped shape from the plane with the bottom member 2 or the lid member 3 laid flat is the maximum and the part where it is the minimum in the entire long side direction.

[0028] Also, for the "range of deformation amount", similar values can be obtained by calculations based on the virtual planar shape. In this case, the "range of deformation amount" is the sum of the absolute values of the parts where the deviation from the virtual planar shape in the direction perpendicular to the plane with the bottom member 2 or the lid member 3 laid flat is the largest in the plus direction and the minus direction respectively. Here, the "virtual planar shape" is the spatial existence position of the bottom member 2 or the lid member 3 assuming that no warping occurred at all. The deviation between this original spatial existence position and the actual spatial existence position with warping corresponds to the "deformation amount". To give a calculation example of the "range of deformation amount" in this sense, in the above [1], when the deformation amount (deviation from the virtual planar shape) at one end is -0.20 mm, the deformation amount at the other end is -0.18 mm, and the deformation amount at the central part is +0.25 mm, the range of deformation amount is |-0.20| + |+0.25| = 0.45 (mm).

[0029] When the above [1] is satisfied, furthermore, it is preferable that the range of deformation amount is 0.5 mm or less.

[0030] When the above [2] is satisfied, furthermore, it is preferable that the range of deformation amount is 3% or less of the length of the long side of the rectangle, and more preferably 2% or less. Similarly, when the above [2] is satisfied, furthermore, it is preferable that the range of deformation amount is 3 mm or less of the length of the long side of the rectangle, and more preferably 2% or less.

[0031] The above numerical ranges are preferably satisfied by both the bottom member 2 and the lid member 3. It is also possible that the bottom member 2 satisfies [1] and the lid member 3 satisfies [2], or that the bottom member 2 satisfies [2] and the lid member 3 satisfies [1]. Alternatively, both the bottom member 2 and the lid member 3 may satisfy [1], or both the bottom member 2 and the lid member 3 may satisfy [2].

[0032] The case 1 is formed by the lid member 3 and the bottom member 2 fitting together. When fitting, as described with reference to FIG. 4, the outer peripheral surface of the tip portion 35gb of the pin 35g comes into contact with the inner peripheral surface of the boss 25g to generate friction, and the upper surface of the tip portion of the pin 35g and the bottom of the boss hole, and the upper surface of the base portion 35ga of the pin 35g and the upper surface (thickness portion) of the boss 25g come into contact or approach each other. In addition, the raised portion 24a of the side plate portion 24 and the lowered portion 34a of the side plate portion 34 come into contact with each other, closing the bottom member 2 and the lid member 3.

[0033] In the case 1, the thickness of the bottom plate portions 23 and 33, which occupy a large area among the bottom member 2 and the lid member 3, is 0.70 mm or less. Since it is thinner than a conventional case with a hinge cap, less material is required for manufacturing compared to the conventional one. Further, since the bottom member 2 and the lid member 3 have thin-walled recesses 26 and 36, even less material is required. Also, the thickness of the partition wall forming the boss 25 is 0.60 mm to 1.00 mm, which is relatively thicker than the thickness of the bottom plate portions 23 and 33. Therefore, it can withstand the pressure in the thickness direction of the case 1 and can have an appropriate fitting force.

[0034] FIG. 6 is a side view of Case 1 as viewed from the long side direction. On the side peripheral surface of Case 1, the fitting portion between the bottom member 2 and the lid member 3 can be seen in appearance. The fitting portion is a portion where the side plate portion 24 of the bottom member 2 and the side plate portion 34 of the lid member 3 should contact and adhere to each other at the tips in the thickness direction of Case 1. The fitting portion may have a situation where the bottom member 2 and the lid member 3 are in close contact, or there may be an appearance gap G (in FIG. 6, the case where the value of the gap G is 0 is depicted). The gap G is preferably 0.15 mm or less at the long side portion, more preferably 0.12 mm or less, and even more preferably 0.10 mm or less. The gap G is preferably 0.15 mm or less at the short side portion, more preferably 0.10 mm or less, and even more preferably 0.09 mm or less. The said gap is measured with a gap gauge. Since Case 1 has a sufficiently small gap, it is excellent in moisture-proof property and can suitably maintain the quality of the contents.

[0035] <Manufacturing Method> The manufacturing methods of the bottom member 2 and the lid member 3 will be described. As these manufacturing methods, ordinary injection molding as resin molding may be performed, or injection molding using a supercritical fluid may be performed. Especially when the MFR of the resin is small, injection molding using a supercritical fluid that can enhance the fluidity of the resin is preferable. Hereinafter, injection molding using a supercritical fluid will be described.

[0036] The manufacturing method of the present embodiment includes the following steps. (A) Step of preparing a molten resin composition containing a resin material and a supercritical state. (B) Step of injecting the molten resin composition into the cavity of the mold. (C) Step of holding the pressure of the cavity and cooling it after the step (B). (D) Step of recovering the molded product from the mold. The series of steps from step (A) to step (D) can be implemented, for example, using a MuCell injection molding machine (「MuCell」 is a registered trademark of Trexel.Co.Ltd) (see, for example, Japanese Patent No. 6085729 and Japanese Patent No. 6430684).

[0037] [Step (A)] First, a molten resin composition containing a resin material and a supercritical fluid is prepared. Examples of the resin material include thermoplastic resins, and specific examples thereof are polypropylene resin and polyethylene resin. The melt flow rate of the thermoplastic resin is preferably 15 g / 10 min or more, more preferably 20 to 40 g / 10 min, and still more preferably 25 to 36 g / 10 min. When this value is 15 g / 10 min or more, the occurrence of short shots tends to be suppressed. On the other hand, when it is 40 g / 10 min or less, a container excellent in drop resistance tends to be manufactured. Here, the melt flow rate (MFR) means a value measured under the conditions of a temperature of 230°C and a load of 2.16 kg in accordance with the method described in JIS K7210-1:2014.

[0038] When carbon dioxide is used as the supercritical fluid, 1 to 3 parts by mass of supercritical carbon dioxide is added to 100 parts by mass of the resin material to prepare a molten resin composition. When the amount of carbon dioxide is 1 part by mass or more, the occurrence of short shots can be suppressed due to the decrease in the viscosity of the molten resin composition caused by the addition of carbon dioxide. In addition, voids can be formed inside the molded body by promoting foaming caused by supercritical carbon dioxide. On the other hand, when the amount of carbon dioxide is 3 parts by mass or less, the holding pressure in step (C) can be set relatively low, and post-swelling tends to be suppressed.

[0039] When nitrogen is used as the supercritical fluid, 0.5 to 1.5 parts by mass of supercritical nitrogen is added to 100 parts by mass of the resin material to prepare a molten resin composition. When the amount of nitrogen is 0.5 part by mass or more, the occurrence of short shots can be suppressed due to the decrease in the viscosity of the molten resin composition caused by the addition of nitrogen. In addition, voids can be formed inside the molded body by promoting foaming caused by supercritical nitrogen. On the other hand, when the amount of nitrogen is 1.5 parts by mass or less, the holding pressure in step (C) can be set relatively low, and post-swelling tends to be suppressed.

[0040] The temperature of the molten resin composition (screw cylinder temperature) may be set according to the melting point or MFR of the resin material. When using a polypropylene resin, this temperature is preferably 200 to 250°C, more preferably about 210 to 230°C. When using a polyethylene resin, this temperature is preferably about 220 to 240°C. When this temperature is at or above the lower limit value, the resin easily flows in the cavity. On the other hand, when it is at or below the upper limit value, there is a tendency to suppress resin scorching.

[0041] The molten resin composition may contain components other than the resin material and the supercritical fluid. That is, the molten resin composition may further contain, for example, a filler, a colorant, a slip agent, an antistatic agent, etc., as necessary.

[0042] [(B) Process] Prepare a mold corresponding to the shapes of the bottom member 2 and the lid member 3 of the case 1 to be manufactured. This mold has a shape corresponding to a shape in which the thickness of the bottom plate portions 23, 33 in the thin-walled recesses 26, 36 of the case 1 to be manufactured is 80% or less of the thickness of the bottom plate portions 23, 33 in the portions other than the thin-walled recesses 26, 36. Then, inject the molten resin composition prepared in the (A) process into the cavity through the gate of the mold. The injection speed is preferably 60 mm / second or more, more preferably 200 mm / second or more, and still more preferably 250 mm / second or more. When the injection speed is 60 mm / second or more, it is easy for the resin to reach the flow end, and there is a tendency to suppress the occurrence of short shots. The upper limit value of the injection speed is, for example, 350 mm / second.

[0043] The maximum value of the injection pressure is preferably 180 MPa and more preferably 150 MPa.

[0044] The gate position of the cavity is preferably provided at a position other than the thin-walled recesses 26 and 36 of the bottom member 2 and the lid member 3, respectively. In particular, in the bottom member 2 having the hinge cap 22, it is preferable to position the gate closer to the side where the hinge cap 22 is formed due to the formation of the hinge cap 22. More specifically, a position closer to the hinge cap 22 side in the long side direction of the case 1 and a position closer to the hinge cap 22 side in the short side direction of the case 1 are preferable.

[0045] Even if the linear distance from the gate of the cavity to the farthest flow end (hereinafter referred to as "maximum flow length") is 60 mm or more, it is preferable that the molten resin composition reaches the flow end. The maximum flow length may be, for example, 70 mm or more or 80 mm or more. The upper limit value of the maximum flow length is, for example, 120 mm.

[0046] The injected resin enters the cavity. At this time, when the thickness of the part constituting the side plate part is larger than the part constituting the bottom plate part, the resin enters the side plate part faster. Therefore, the part constituting the side plate part is likely to be filled first, and the position away from the inside of the side plate part is likely to be the final filling part. In particular, in this embodiment, since the thickness of the part that becomes the thin-walled recess is small, the resin entry speed of this part is slow, and it is likely to be the final filling part.

[0047] [Step (C)] After the above step (B), the cavity is held under pressure at a pressure condition of 15 to 80 MPa and cooled. When this pressure is 15 MPa or more, it is possible to promote the foaming of supercritical carbon dioxide and nitrogen while suppressing the occurrence of short shots. On the other hand, when it is 80 MPa or less, it tends to be possible to promote the foaming of supercritical carbon dioxide and nitrogen while suppressing the occurrence of after-swelling. This value is preferably 15 to 50 MPa, more preferably 15 to 30 MPa. Alternatively, it may be 40 to 70 MPa. The holding pressure time may be determined while considering the gate seal time, and may be, for example, 0.1 to 1.5 seconds.

[0048] From the perspective of producing a thin-walled portion, it is preferable not to perform a process called "core-back" for reducing the pressure inside the cavity. Core-back is a process of moving the movable part of the mold to expand the volume of the cavity before the molten resin composition filled in the cavity finishes solidifying (see Japanese Patent No. 6085729).

[0049] [Step (D)] When the temperature of the molded article (bottom member or lid member) in the mold drops to about 30 to 60°C, the molded article is recovered from the mold. In the present embodiment, since pressure holding is performed in the (C) step and "core-back" is not performed as described above, large voids that can be visually confirmed are not formed so much in the molded article of the present embodiment. However, there are small voids that cannot be visually confirmed with the naked eye. It can be said that the molded article of the present embodiment mainly aims at weight reduction by thinning rather than weight reduction by voids.

[0050] In the manufacturing method having these series of steps, by adjusting the temperature at which the resin is melted in the (A) step, the amount and injection speed of the resin used in the (B) step, the pressure of pressure holding in the (C) step, etc., the degree of warpage of the bottom member 2 and the lid member 3 can be adjusted. For example, when the pressure of pressure holding is increased, warpage is likely to be "convex upward" (the shape in Fig. 5(B)), and when the pressure of pressure holding is decreased, warpage is likely to be "convex downward" (the shape in Fig. 5(C)).

[0051] By fitting the bottom member and the lid member manufactured by the above manufacturing method, a case with a hinge cap can be obtained. Since the bottom member and the lid member constituting the case with a hinge cap of the present embodiment are thinner than conventional ones, there is a concern that short shots may occur during injection molding. In this regard, according to the manufacturing method of the present embodiment, since the fluidity of the molten resin composition is good and the occurrence of short shots can be suppressed, a molded article with a reduced resin usage amount compared to the conventional one can be manufactured without problems.

[0052] In addition, since both the bottom member and the lid member have thin-walled recesses, it is possible to guide the position where short shots are likely to occur to the portion of the thin-walled recess. That is, when there is no thin-walled recess, if a short shot occurs, it is likely to occur at a position far from the gate (for example, a rounded corner portion). When there is a thin-walled recess, due to the relationship of the required pressure, the molten resin composition enters the portion of the thin-walled recess later, so if a short shot occurs, it is likely to occur in the portion of the thin-walled recess. Therefore, the moldability of the side plate portion is not impaired and the fitting property is maintained. Further, when a short shot occurs, it occurs in the portion of the thin-walled recess, so the portion to be focused on during the appearance inspection of the molded product becomes clear and the inspection becomes easy.

[0053] The problem of short shots occurring is likely to occur when the shape of the molded body is asymmetric due to having an attachment portion to be filled with resin, such as the bottom member 2 having the hinge cap 22. According to the manufacturing method of the present embodiment, it is particularly effective for molding a member (bottom member 2) having an attachment portion (hinge cap 22) that is a factor in the asymmetric shape. On the other hand, the lid member 3 without the hinge cap 22 has a smaller degree of asymmetry and tends not to have short shots occur.

[0054] In addition, the case of the present embodiment has a thin-walled design in which the bottom member and the lid member are likely to warp, but since the direction and range of the warpage amount generated during manufacturing are within a predetermined range, the gap generated in the fitting portion of the side circumferential surface of the case can be reduced. This prevents an adverse effect on the quality of the contents. In the manufacture of conventional bottom members and lid members, it was common sense to eliminate warpage and achieve a completely flat shape, which was considered the quality aimed for in manufacturing. However, in the present embodiment, warpage deformation occurring within a predetermined range is deliberately tolerated, or the manufacturing conditions are deliberately adjusted so that warpage deformation within a predetermined range occurs, and the direction and degree of warpage deformation of the bottom member and the lid member are supported by the fitting force of the boss and the pin, thereby suppressing the generation of gaps in the fitting portion.

[0055] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiment, the boss 25 is provided on the bottom member 2 and the pin 35 is provided on the lid member 3, but a mode in which a pin is provided on the bottom member and a boss is provided on the lid member may also be adopted.

[0056] In addition, in the above embodiment, a mode in which the boss 25 and the pin 35 are fitted by frictional force is shown. However, in order to further increase the fitting force, a rib-shaped reduced-diameter portion extending in the circumferential direction is provided on the inner peripheral surface of the boss 25, and a rib-shaped enlarged-diameter portion extending in the circumferential direction is provided on the outer peripheral surface of the tip portion 35gb of the pin 35. A mode may be adopted in which the reduced-diameter portion and the enlarged-diameter portion are fitted by sliding past each other in the boss hole during fitting.

[0057] In addition, in the above embodiment, a mode in which two rectangular recesses are provided in both the bottom member 2 and the lid member 3 as the thin-walled recesses 26 and 36 is shown. However, the shape of the thin-walled recesses 26 and 36 may be other than rectangular, and the number may not be two.

[0058] In addition, in the above embodiment, a plurality of ribs protruding in the thickness direction and toward the end side of the side plate portion 24 may be provided on the inner surface side of the side plate portion 34 of the lid member 3. For example, three ribs are provided along the long side and two ribs are provided along the short side. These ribs reinforce the structure of the side plate portion 34 and also function to receive the stepped portion 24a of the bottom member 2 from the side during fitting.

[0059] In addition, the bottom plate portions 23 and 33 may contain bubbles of a size that cannot be visually confirmed. This makes it easier to suppress the occurrence of warping that is likely to occur in a thin molded body.

Examples

[0060] Hereinafter, the content of the present invention will be described more specifically with reference to experimental examples. Note that the present invention is not limited to the following experimental examples.

[0061] <Resin material> The following main material and colorant were mixed at a weight ratio of 100:5. · Main material: Polypropylene (manufactured by Sun Allomer Co., Ltd., random copolymer "PM931V", MFR: 22 g to 28 g / 10 minutes) · Colorant: Commonly used white colorant

[0062] <Molding of bottom member> Using nitrogen as the supercritical fluid, the bottom member 2 with a hinge cap shown in Fig. 2 was injection molded under the conditions shown in Table 1. The design values are as follows. Overall size: Long side 100 mm × short side 52 mm Thickness of flat part: 0.6 mm Thickness of thin-walled concave part: 0.45 mm Thickness of side plate part: 1.7 mm The gate position was set at a position closer to the hinge cap 22 side in the long side direction of the bottom member 2 and at a position closer to the hinge cap 22 side in the short side direction of the bottom member 2. The maximum flow length (L) in design, that is, the straight-line distance from the gate to the farthest position of the molded body, was 83 mm in design. Short shots did not occur.

[0063] <Molding of lid member: Experimental Examples 1 to 10> Using nitrogen as the supercritical fluid or without using the supercritical fluid, the lid member 3 shown in Fig. 3 was injection molded under the conditions shown in Table 1. The design values are as follows. Overall size: Long side 100 mm × short side 52 mm Thickness of flat part: 0.6 mm Thickness of thin-walled concave part: 0.45 mm Thickness of side plate part: 0.8 mm The gate position was set at a position closer to the concave part forming the opening 5 in the long side direction of the lid member 3 and at a position closer to the concave part forming the opening 5 in the short side direction of the lid member 3. The maximum flow length (L) in design, that is, the straight-line distance from the gate to the farthest position of the molded body, was 83 mm in design. Short shots did not occur in any of the lid members in Experimental Examples 1 to 10.

[0064]

Table 1

[0065] <Confirmation test> For the lid members molded in Experimental Examples 1 to 10, the amount of deformation was measured, and the range of the amount of deformation was determined. Then, each lid member was fitted with a common bottom member to form a case, and the amount of gap on the side circumferential surface thereof was determined.

[0066] (Range of deformation amount) With the inner surface side facing downward and lying flat on a plane, it was viewed from the long side in side view (see Fig. 5(A)), and a total of three positions, namely both end points and the position where the height is the highest or lowest between the two end points, were measured using a straight ruler. One of the measurement positions of the two end points is called "Pt.1", the measurement position between the two end points is called "Pt.2", and the other measurement position of the two end points is called "Pt.3". At the three positions of Pt.1 to Pt.3, the distance between the plane and the edge of the side plate portion was measured, and the deviation between the virtual planar shape and the measured value was defined as the "amount of deformation". Then, the parts where the amount of deformation is the largest in the plus direction and the minus direction respectively were added together with their absolute values to obtain the value of the "range of the amount of deformation".

[0067] (Amount of gap) For the two sides of the side circumferential surface where they are fitted, namely the long-side small lid side (the side with the hinge cap) and the short-side upper side (the side close to the hinge cap), the amount of gap was measured using a gap gauge respectively.

[0068] <Evaluation> The results of the confirmation test are shown in Fig. 7. Among the respective result items of Experimental Examples 1 to 10 shown, the "N" - shaped or "V" - shaped broken line connecting Pt.1 to Pt.3 is a graph connecting the amounts of deformation at each location, visually showing the state where the shape of the lid member is "convex upward" (Fig. 5(B)) or "convex downward" (Fig. 5(C)). The difference between the maximum value and the minimum value of this broken line corresponds to the value of the "range of the amount of deformation". Incidentally, the shape of the bottom member was "convex upward" and the "range of the amount of deformation" was 0.50 mm.

[0069] When the lid member is "convex upward", when the range of the amount of deformation is 0.50 mm, the gap amount of the case becomes 0.15 mm or less (Experimental Example 4). When the range of the amount of deformation exceeds 0.50 mm, the gap amount exceeds 0.15 mm (Experimental Examples 1 to 3). When the lid member is "convex downward", the gap proof of the case becomes 0.15 mm or less regardless of the range of the amount of deformation (Experimental Examples 5 to 10).

Industrial Applicability

[0070] The present invention can be used as a container for putting cooling granular materials or the like and using them in small portions.

Explanation of Signs

[0071] 1... case, 2... bottom member, 3... lid member, 5... opening, 21... hinge, 22... hinge cap, 23, 33... bottom plate portion, 24, 34... side plate portion, 24a... stepped-up portion, 25(25a, 25b, 25c, 25d, 25e, 25f, 25g)... boss, 26, 36... thin-walled concave portion, 34a... stepped-down portion, 35(35a, 35b, 35c, 35d, 35e, 35f, 35g)... pin, 35ga... base portion, 35gb... tip portion, G... gap, T 1 ... thickness of the portion that is not the thin-walled concave portion of the bottom plate portion, T 2 ... thickness in the thin-walled concave portion of the bottom plate portion, T 3 ... thickness of the partition wall of the boss, T 4 ... thickness of the side plate portion.

Claims

1. A resin case with a hinge cap, in which a bottom member and a lid member, both of which are substantially rectangular and tray-shaped, are fitted to each other, wherein the length of the rectangle in the long side direction is 120 mm or less, and the length in the short side direction is 70 mm or less, both the bottom member and the lid member include a bottom plate portion and a side plate portion rising from the periphery of the bottom plate portion, the bottom member has a hinge cap on a part of the side plate portion, a boss is formed on the inner surface of the bottom plate portion of either the bottom member or the lid member, and a pin that fits into a boss hole of the boss is formed on the inner surface of the bottom plate portion of the other, at least one of the bottom member and the lid member has a thin-walled recess on the inner surface of the bottom plate portion, the thickness of the bottom plate portion other than the thin-walled recess is 0.70 mm or less, the thickness of the bottom plate portion within the thin-walled recess is 80% or less of the thickness of the bottom plate portion outside the thin-walled recess, a case with a hinge cap, wherein at least one of the bottom member and the lid member satisfies the following [1] or [2]. [1] When lying flat on a plane with the inner surface side facing downward and viewed from the long side in side view, the central portion in the left-right direction is lifted upward from at least one end portion, and the range of the deformation amount in the direction perpendicular to the plane is 0.5% or less of the length of the rectangle in the long side direction. [2] When lying flat on a plane with the inner surface side facing downward and viewed from the long side in side view, at least one end portion in the left-right direction is lifted upward from the central portion.

2. The case with a hinge cap according to Claim 1, wherein when satisfying [1], further, the range of the deformation amount is 0.5 mm or less.

3. The case with a hinge cap according to Claim 1, wherein when satisfying [2], further, the range of the deformation amount is 3% or less of the length of the rectangle in the long side direction, or 3 mm or less.

4. The case with a hinge cap according to Claim 1, wherein both the bottom member and the lid member satisfy [1] or [2].

5. The case with a hinge cap according to Claim 1, wherein the length of the rectangle in the long side direction is 70 mm or more and 120 mm or less, and the length in the short side direction is 40 mm or more and 70 mm or less.

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