WO1999033709A1 - Canned goods of low positive pressure having inner pressure checking adaptability, and can body of the same - Google Patents

Abstract

A can body (1) of canned goods of a low positive pressure having inner pressure checking adaptability, wherein a trunk portion (2) and a bottom portion are molded seamlessly into an integral structure, the bottom portion having an annular seating section (3) in the vicinity of an outer circumferential part thereof, a part on the inner side of the annular seating section (3) constituting an inner rising wall (4) extending upward in the inward direction of the can body, a substantially flat bottom wall (6) being formed on the inner side of the inner rising wall (4) to a height larger than that of the seating position by 0.5-6 mm, goods being packed and sealed in the can body (1) in a low positive-pressure state so that an inner pressure at room temperature is 0.2-0.8 kgf/cm2 and more preferably in the range of 0.2-0.6 with scatter of +/- 0.2 kgf/cm2 and preferably +/- 0.1 kgf/cm2, to enable the flat portion of the bottom wall (6) to have a knock-checking adaptability.

Description

 Description Low positive pressure cans with internal pressure inspection suitability and their cans

 The present invention relates to a low positive pressure can having an internal pressure inspection suitability and a can body thereof, particularly a low positive pressure can having an internal pressure inspection suitability capable of performing an internal pressure inspection with the same accuracy as a punching inspection conventionally applied to an internal pressure inspection of a negative pressure can. It relates to a pressure can and its can. Background art

 In the past, for example, canned low-acid beverages such as milk-filled beverages, which are extremely susceptible to spoilage and decay, have been required to have a sealability after filling and a spoilage inspection of the contents. In order to inspect the sealability of the can and the decay of the contents, the can lid or bottom is generally hit with an electromagnetic pulse to generate vibration, and the internal pressure is determined by the correlation between the generated sound (frequency) and the internal pressure of the can. An inspection method called a percussion test is used to detect the tightness due to excessive or insufficient internal pressure, and to detect the presence or absence of expansion due to putrefactive bacteria. Since low-acid beverages are generally hot-filled (hot-packed) and retorted, cans of low-acid beverages are reduced by the shrinkage of the contents and gas in the headspace when the contents cool to room temperature. Negative pressure is generated, resulting in negative pressure canning. Negative pressure cans have a degree of vacuum in the range of approximately 20 to 60 cmHg, have small pressure variations, and have a large change in natural frequency with respect to fluctuations in internal pressure. There is an advantage that leakage and deterioration of the contents can be accurately detected by percussion inspection.

 However, negative pressure canning requires a highly rigid body that can withstand negative pressure, and has the problem of increased can cost because the side walls are thicker than positive pressure cans.

On the other hand, by filling an inert (liquefied / solidified) gas such as liquid nitrogen at the time of sealing, a positive pressure is generated in the can due to the vaporization and expansion of liquid nitrogen, etc., and the rigidity is given by the pressure inside the can. There are positive pressure cans. Positive-pressure canned foods usually have an internal pressure of 1. In the range of 0 ± 0.3 kgi / cm ² (gauge pressure, the same applies hereinafter), and at retort, it reaches 6. Okgf / cm ² or more, so the bottom of the can is inside the can to withstand the internal pressure. It is formed in a dome shape that bulges. Positive pressure cans have a positive pressure applied inside the can compared to negative pressure cans, so they are less susceptible to dents even when exposed to external pressure. This has the advantage that the cost can be reduced.

 As described above, positive pressure cans can be used to reduce the thickness of can materials.However, conventional positive pressure cans lack the suitability for internal pressure inspection and have insufficient quality assurance due to the following reasons. Until now, the contents of low-acid beverages, such as beverages with milk, are relatively thick, with the bottom of the can having a thickness of 0.24 to 0.26 mm and the can body having a thickness of about 0.2 mm. Applied to steel negative pressure cans, positive pressure cans were applied only to relatively perishable and perishable contents.

(1) In the case of positive pressure canning, the internal pressure is generated by the charged gas, so the variation in internal pressure is larger than that in negative pressure canning. With conventional gas displacement positive pressure cans, positive pressure cans with an internal pressure variation of ± 0.3 kgi / cni ² or more with respect to the set pressure, but still with an internal pressure variation of ± 0.3 kgf / cm ² or less with the set pressure Is not provided. For this reason, even if the can pressure can be measured accurately, it is difficult to distinguish whether the measured internal pressure is due to deterioration of the contents or due to the variation in the filling gas amount due to the large variation range. It is difficult to detect spoiled cans accurately.

 (2) In the case of a positive pressure can with a dome-shaped bottom in order to increase pressure resistance, the bottom wall is unlikely to change with the internal pressure, and an accurate internal pressure change should be inspected in the internal pressure test such as a beating test using the bottom. Quality assurance as a can of perishable contents that cannot be made.

③ Furthermore, if the positive pressure canned by conventional gas replacement method, since the can internal pressure is high, generally 1. 0 ± 0. 3 kgf / cm 2, even with very small pressure variations due to small leaks and corruption However, it is difficult to detect the internal pressure due to the low internal pressure fluctuation rate of the whole. . Also, The same applies to the case where the internal pressure of the can is detected based on the displacement of the lid, the bottom or the body, or the case where the internal pressure of the can is detected by pushing the body or the like at a predetermined pressure and measuring the reaction force. When the can pressure is high, the rigidity of the can increases, and the amount of change in the displacement or the reaction force is small, so that the internal pressure inspection becomes difficult.

 陽 When retort sterilizing positive pressure cans by the conventional gas replacement method, etc., the internal pressure increases during retort processing, and the positive pressure state further increases, so the strength to withstand the internal pressure, especially buckling Pressure resistance of the can bottom and lid is required. Therefore, it is difficult to withstand the retort treatment with the conventional bottom shape for negative pressure cans. In order to make cans necessary for retort treatment, the can bottom must be thickened. The advantage of positive pressure canning, which is used to reduce the thickness, is lost. Disclosure of the invention

 Thus, the present invention solves the problems of positive pressure cans that lack the suitability for internal pressure inspection as described above, and allows the use of thin-walled cans for canning low-acid beverages such as milk-filled beverages. Specifically, it has excellent suitability for low pressure inspection such as percussion, etc., has a high ability to detect leakage and deterioration, withstands an increase in internal pressure during retort processing, and It is an object of the present invention to provide a low positive pressure can having an internal pressure inspection suitability and a can body thereof, which can reduce the thickness of the can and reduce the cost of the can.

The positive pressure can having the suitability for an internal pressure test of the present invention for solving the above-mentioned problems is a can which is obtained by filling and sealing the contents so that the internal pressure of the can is at least a positive pressure with respect to an external pressure. The inner pressure of the can at room temperature is in the range of 0.2 to 0.8 kgf / cm ² , preferably 0.2 to 0.6 kgi / cm ² , so that it is suitable for internal pressure inspection. It is. The can internal pressure, in the range of the set pressure ^{0. 2~0. 8 kgf / cm 2} , variation ± 0. ² kgf / cm 2 or less, preferably may is ± 0. 1 kgf / cm ² or less. It is not preferable that the variation is 0.2 kgf / cm ² or more because the reliability of detecting a small internal pressure change due to a small leak or deterioration is low. The internal pressure inspection characteristics are For example, when performing internal pressure inspection by percussion inspection, the response of the sound (frequency) generated by the impact is small even with a small change in the internal pressure of the can, and the displacement of the outer periphery of the can is measured with a displacement meter. When performing internal pressure inspection, the response of the displacement of the measurement site to the minute change in the can internal pressure is good.Furthermore, the internal pressure is measured by pushing the outer peripheral part of the can at a predetermined pressure and measuring the reaction force. When performing an inspection, it refers to the ability to measure the internal pressure accurately, with a good response to the reaction force even for minute changes in the internal pressure of the can.

 In order to reduce the cost of the can body, a seamless can having a body portion and a bottom portion integrally formed is desirable. Further, the bottom portion of the can body has an annular grounding portion, and the inside of the outer annular grounding portion is provided. It is desirable to have a bottom wall that becomes a substantially flat part, and to have internal pressure inspection suitability at the bottom. If the can is a seamless can and the bottom is a dome-shaped can, the lid or the body of the can shall be suitable for internal pressure inspection.

The can internal pressure 0. 2 ~ 0. 8 kgf / cm 2 , preferably 0.2 to 0. Of 6 kg f / cm ² range, as shown in the graph of FIG. 5, the punch biopsy, versus the can internal pressure change The rate of change (slope) of the vibration frequency at the bottom of the can is large, and the vibration frequency changes significantly even with a slight change in the internal pressure, confirming that the measurement of the internal pressure of the can can be detected well. . This range is in a positive pressure state equivalent to the vacuum level of the negative pressure can, and means that it can be punched with the same accuracy as that of the negative pressure can. If the pressure inside the can is outside the above range, the change in the vibration frequency with respect to the change in the pressure inside the can is small, resulting in poor judgment. Furthermore, if the internal pressure of the can is 0.8 kgf / cni higher than ² kg, the differential pressure between the inside and outside of the can is too large during retort processing (immediately after removal from the retort kettle) if the can is to be retorted. In a can bottom shape with a substantially flat surface, the can material must be made thick to maintain pressure resistance, and is inferior in suitability for pressure testing. In addition, the displacement of the lid, bottom, or body is measured in the can pressure range within the range of the can pressure described above, and when the internal pressure is to be inspected, good internal pressure inspection is appropriate except for the dome-shaped bottom with high rigidity. It has a an outside the can internal pressure range 0.2 determination kgf eight m ² Yori in smaller cans pressure seal guarantee is insufficient, the can internal pressure is higher than 0. 8 kg i / cm ² Within this range, the rigidity of the can increases, and the amount of change in displacement is small, making accurate internal pressure inspection difficult.

 The content of the positive-pressure cans is not particularly limited, and the content is a low-acid beverage, the content is sealed at a positive pressure by a gas replacement method, and the retort is sterilized after filling and sealing. It can be suitably applied to any of the following, and has an internal pressure inspection suitability at any of the bottom, the trunk, and the lid. The gas replacement method referred to in the present invention is not limited to the case in which an inert gas such as nitrogen gas is blown into a head space to perform replacement, and a liquefied gas such as liquid nitrogen or a solidified gas such as dry ice is placed in a can. It also includes the case where positive pressure is generated in the can due to its vaporization and expansion.

The can body used for the low positive pressure can of the present invention has a body portion and a bottom portion formed integrally with a seamless, the bottom portion has an annular grounding portion near an outer peripheral portion, and the inside of the annular grounding portion is formed inside. A bottom wall having a substantially flat shape and a height of 0.5 to 6 mm from the ground position, wherein the bottom wall has an inner rising wall rising up into the can; The center portion of the bottom wall has applicability for percussion. The shape of the bottom of the can is preferably that an annular bead having a depth of 0.1 to 4 mm from the bottom wall to the inside of the can is formed at the bottom of the inner rising wall of the annular grounding portion. Preferably, the ground diameter of the can bottom is 70 to 98% of the can body diameter, and the flat part diameter of the can bottom is 60 to 90% of the ground diameter. In addition, it is desirable that the inclination angle of the rising wall be 65 to 110 °. The annular bead is not limited to an inverted U-shaped cross section, but may be formed so as to have a gentle slope from the top to the bottom wall so as to continue to the bottom wall. Incidentally, the annular bead height from the ground position of good _c the bottom wall flat portion be plural rows formed not limited to one, the 0.5 deformed bottom after Les preparative belt as匪以is under the If it is higher than the grounding part, the thickness from the grounding to the rising part will be reduced due to molding, and this will cause a decrease in withstand voltage performance. In addition, it is not preferable that the content is small with respect to the can height, and that the material cost is relatively increased. In addition, the depth of the annular bead should be 0.1 The above range is preferable because the effect of the above is not sufficiently obtained, and when the depth is 4 mm, the molding becomes difficult. Furthermore, if the sloped wall of the riser wall is smaller by 65 °, the pressure resistance of the grounding part will be reduced, and the area of the flat bottom wall will be smaller, which may cause deterioration of suitability for internal pressure inspection. If it is too large, molding becomes difficult.

 As the metal material of the can applied to the present invention, a metal plate such as tinplate, TFS, surface-treated copper plate, or a laminated plate obtained by laminating a synthetic resin such as a polyester film on such a metal plate is used. Materials and methods for manufacturing cans are particularly limited, such as seamless cans formed by a combination of squeezing and ironing or stretching, or 3-piece cans with a lid wrapped around the bottom. However, according to the present invention, according to the present invention, the thickness of the bottom of the can is reduced to 0.15 to 0.25 mm for steel and to 0.25 to 0.35 mm for aluminum. Is possible. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-sectional view of a main part of a can body for low positive pressure cans according to an embodiment of the present invention, and FIG. 2 is a schematic view of the main part,

Figures 3—A, 3—B, 3—C, 3—D, and 3—E are schematic diagrams of main parts of a can for low positive pressure cans according to other different embodiments of the present invention. Fig. 4-1A and Fig. 4-B are graphs showing the amount of displacement of the bottom of the can with respect to the internal pressure of the can. Fig. 4-A is the case of the can of the embodiment shown in Fig. 1. Fig. 4-B shows the case of the can shown in Fig. 3-A.

Fig. 5 is a graph showing a comparison of the internal pressure versus frequency distribution curves of the canning of positive pressure cans and negative pressure cans with can bottoms. In the case of negative pressure cans, the absolute value is shown. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a main part of a can according to an embodiment of the present invention. This embodiment The can body 1 is a two-piece can (seamless can) in which the body and bottom are integrally formed, a steel plate or an aluminum plate, or a composite plate formed by laminating a PET film or the like on these plates. They were formed by ironing or by combining them with stretching. The bottom of the can 1 has a mountain-shaped annular grounding portion 3 and a valley-shaped annular bead 5 between a body wall 2 and a bottom wall 6. The bottom of the inner riser wall 4 of the annular grounding portion 3 projects from the bottom wall surface into the can and is folded back to form an annular U-shaped bead 5 protruding into the can. ing. In the present embodiment, the bottom wall 6 inside the annular bead is formed entirely flat.

 The inclination angle α of the outer rising wall 7 of the annular ground part 3 is in the range of 5 ° to 30 °, and the inclination angle of the inner rising wall 4 is in the range of 65 ° to 110 °. In addition, the height h of the center of the bottom wall from the grounding surface is such that the can bottom expands as the internal pressure increases during retort processing, and the bulge remaining on the bottom wall protrudes outward from the annular grounding part when the temperature returns to room temperature. It is not necessary to make a hole, 0.1 to 10 mm, preferably 0.5 to 6 mm. Furthermore, it was confirmed that the annular bead 5 plays a role of increasing the pressure resistance of the bottom against the internal pressure, and that the internal pressure resistance is improved by increasing the depth to some extent. The presence of the annular bead 5 functions to increase the pressure resistance of the bottom part because the annular bead shape increases the peripheral rigidity against the swelling to the outside of the flat bottom wall with the increase of the internal pressure, and In order to obtain this effect, the depth m of the annular bead 5 is set to 0.

1-5mm, preferably 0.1mm-3 range is good. The ground diameter of the annular grounding part 3 is in the range of 70 to 98% of the can body diameter from the viewpoint of independence and strength, and the diameter of the flat part of the bottom wall is 60 It was confirmed that the formation in the range of ~ 90% was a good range for the internal pressure inspection at the bottom.

By forming the bottom in the shape as described above, improved compressive strength of the bottom wall, the thin cans 2-piece can withstand the can out differential pressure 5 kg f / cm ² to be assumed at the time of retort sterilization A pressure resistance can be obtained. The pressure resistance is equal to the rate required for sterilizing the contents during retorting as described later. This is a strength that can withstand a pressure increase during the tilting process. The thickness of the bottom of the can is 0.15 to 0.25mm for steel, and steel for aluminum, to maintain the pressure resistance and to make the plate as thin as possible. Since the pressure resistance is poor, the range of 0.25 to 0.35 mm is appropriate.

 The bottom of the can body of this embodiment has the above-described shape, and an embodiment of a low positive pressure can having the suitability for percussion of the present invention using the can body will be described.

A low acid beverage with milk is hot-backed into a can and filled with liquid nitrogen or dry ice or other inert gas (hereinafter simply referred to as nitrogen) and sealed. At that time, room temperature after filling with nitrogen etc. The internal pressure of the can is set to be 0.2 to 0.8 kgf / cm ^2, preferably 0.2 to 0.6 kg i / cm ² , which is lower than that of the positive pressure can which is usually carried out, and Filling and sealing are performed by controlling the filling amount of nitrogen or the like so that the set pressure maintains an accuracy of ± 0.2 kgi / cm ^2, preferably ± 0.1 kgiZcm ² . In the present invention, it is important to set the internal pressure to a low value and to reduce the variation in the set pressure, so that the detected internal pressure of the can is caused by deterioration. It is possible to determine whether the pressure is simply due to the variation in the internal pressure of the can. If the bottom pressure of a conventional negative pressure can is used for the inspection of the can pressure, it is possible to accurately detect deterioration.

As a method for accurately obtaining the set internal pressure for gas replacement, for example, a liquefied gas such as liquid mist or dry ice, such as liquid nitrogen, and low-temperature nitrogen are placed in the head space of a can filled with contents immediately before winding. A method of simultaneously filling with an inert gas such as a gas can be adopted. By blowing a mist-like liquefied gas or a mixture of dry ice and an inert gas of a predetermined particle size into the head space, the air in the head space is expelled and replaced by gas. By making liquefied gas or dry ice that evaporates into an inert gas into fine particles in the form of mist, the influence of viscosity becomes more dominant than the effect of inertia at the time of seam tightening. Liquefied gas or dry ice remains in the can without being affected by the centrifugal force due to the rotation of the can, and does not scatter outside. Generates internal pressure, 內 Regardless of the variation, a constant internal pressure can always be obtained. By controlling the ratio between the vaporization expansion and the temperature expansion, the filling internal pressure can be controlled, and a desired internal pressure can be accurately and stably obtained.

Next, in the retort sterilization process performed after sealing and filling, the retort sterilization process is performed so that the pressure difference between the inside and the outside of the can during the retort process is within 5 kgi / cm ² . In the present invention, the pressure difference between the can and the outside of the can of 5 kgf / cm ² is 0.2 in the present invention before the retort sterilization.

Since ~ 0. 8 kgf / cm ^2, preferably it is set to ^{0. 2~0. 6 kgi / cm 2} , can tolerate the pressure rise during retorting to 4. 2~4. 8 kgi / cm ² This means that this increase in pressure is within the range where sufficient retort treatment can be ensured to sterilize the low-acid beverage content.

The cans manufactured through the above processes are back-ringed against the rise in can pressure during the retort sterilization process, even though the can material is a thin-walled can made mainly of steel or aluminum. The bottom of the can has sufficient pressure resistance. Moreover, at room temperature, the internal pressure of the can has an accuracy of 0.2 kgi / cm ^2, preferably ± 0.1 kgf / cm ² , so that deterioration of the contents can be detected. At least the center of the bottom wall of the can is a flat surface, so it has excellent tapping suitability. Therefore, according to the present invention, a low-acid beverage that requires retort sterilization can be filled in a thin two-piece can to have pressure resistance and to ensure sufficient deterioration detection ability of the contents. However, compared to conventional low-acid beverage cans, it can be made thinner and lighter, and can be used for aluminum cans and can cost can be reduced.

Although one embodiment of the present invention has been described above, the present invention can be variously modified within the scope of the technical idea, and is not limited to the above embodiment. Further, in the above embodiment, the case where the internal pressure inspection is performed by punching is described, but the positive pressure can of the present invention is not necessarily limited to punching. For example, the displacement of the outer periphery of the can, such as the lid, the bottom, or the body of the can, is measured with a displacement meter and converted to the internal pressure of the can to perform a low pressure test, or the outer periphery of the can is pushed in at a predetermined pressure. It is also suitable for measuring the reaction force and converting it to the can internal pressure state to perform internal pressure inspection. Applicable to Regardless of which internal pressure test method is adopted, the measurement site on the outer periphery of the can is in a state where it is easy to accurately measure the change in the frequency, displacement, or reaction force in response to the change in the internal pressure. It is necessary to set the internal pressure range where loss can be detected. Therefore, in the present invention, the can internal pressure 0.5 at room temperature 2~0. 8 kgi / cm ² is preferably set to the range of 0. 2 ~ 0. 6kgi / cm 2, and ± respect to the set pressure 0 It was confirmed that maintaining a precision of 0.2 kgf Zcm ^2, preferably ± 0.1 kgfcm ² , was a low positive pressure can with the most suitable internal pressure inspection suitability. The content is not necessarily limited to low-acid beverages.

 FIG. 3 shows various embodiments in which the shape of the can bottom of the can body of the present invention is modified. Similar effects can be obtained by employing these shapes. In the following embodiment, only portions different from the can of the embodiment shown in FIG. 1 will be described. The can body 10 in the figure (a) has a slightly larger inclination angle β of the inner rising wall 12 of the annular grounding portion 11, and the annular bead 13 has a straight line from the top to the bottom wall 14. It has a gently inclined portion 13 'that is gently inclined in a shape and continues to the bottom wall.

 The can body 15 shown in FIG. 5B has a particularly different bottom wall shape. The bottom wall 17 of the present embodiment has a flat central portion 17 ′, but an outer peripheral portion 11 ″ is formed so as to be inclined toward the end of the gentle inclined portion 16 ′ of the annular bead 16. (C) is characterized in that the annular grounding portion 21 is formed to be wide as a whole, that is, the annular grounding portion 21 has a tip portion 21 ′ And a gentle inclined surface 2 1 ″, and an inner rising wall 22 extending from the gentle inclined surface to the annular bead 23. In the can body 25 shown in FIG. 4D, the annular grounding portion 26 is wider than that of the embodiment shown in FIG. 5A, and is also wider than that of the embodiment shown in FIG. The bottom wall 27 is formed high, corresponding to a narrow one. The can body 30 shown in FIG. 3E has an annular bead formed between the annular grounding portion 31 and the flat bottom wall 34 in two lines of a four-shaped bead 32 and a ώ-shaped bead 33. Is equivalent to

Example Example 1

 Surface thickness of laminated polyester film on both sides of surface treated copper ^ K

Squeeze and stretch from a 0.18mm copper plate blank, stretch the can with a can body diameter of 53mm, a ground contact diameter of 46.8nun, inclination angle of outer rising wall α = 10 °, inner rising The inclination angle of the wall i3 = 78 °, the height of the bottom wall from the ground contact position h = 3.3 mm, the flat wall diameter of the bottom wall 35.6 mm, the depth from the flat part to the annular groove 1.9 mm, In addition, a seamless can having an inclination angle of 43 ° and a can height of 10 Omm was formed. The thickness of the bottom of the can was 0.18 mm.

The molded seamless can was filled with 190 g of milk coffee and liquid nitrogen so as to generate an internal pressure of 0.5 ± 0.1 kgf / cm ² , and then sealed and sealed. Heat sterilization and cooling in the usual retort treatment step were performed to obtain positive pressure canned 100 cans. It was confirmed that the obtained can had no abnormal deformation of the can and had a pressure resistance to the retort treatment. A percussion inspection was performed on all the cans obtained. As a result, it was confirmed that all the cans had proper perforation accuracy with respect to the internal pressure, and that all the cans had suitability for perforation.

Comparative Example 1

Using a seamless can molded in the same manner as in Example 1, 190 g of milk coffee was filled, and liquid nitrogen was filled so as to generate an internal pressure of 1.0 ± 0.1 kgf / cm ² . Thereafter, it was rolled and sealed, and then subjected to heat sterilization and cooling in a usual retort treatment step to obtain 100000 positive pressure cans. Among these, it was found that local buckling deformation occurred in the 250 rise cans on the inner riser wall, and the pressure resistance under these internal pressure conditions was insufficient. Regarding the remaining cans that have not buckled, the flat part near the annular bead has relatively large deformation. No percussion suitability was obtained.

Comparative Example 2

Positive-pressure can of milk coffee 190 g in the same manner as in Example 1 and Comparative Example 1 except that the amount of liquid nitrogen was reduced so that the can pressure became 0.1 kgf / cm ² 100,000 cans were obtained. All of the cans obtained had insufficient strength of the cans and could not be transported or handled by vendors.

Comparative Example 3

 In the seamless can of Example 1, the diameter of the flat portion was changed to 44 mm, and an attempt was made to obtain a seamless can under the same processing conditions as in Example 1, but the annular groove was cracked and the can was not processed. .

Comparative Example 4

 Further, the diameter of the flat portion was changed to 26 mm in the seamless can of Example 1, and a seamless can was obtained under the same processing conditions as in Example 1, and the same as Example 1 was performed using the can. Through the steps, 10000 cans of positive pressure canned milk coffee (190 g) were obtained. The obtained cans had low pressure resistance at the bottom of the can during retort treatment, and all cans were deformed by the retort treatment and the bottom of the can was deformed.

Example 2

 The following tests were conducted to examine the pressure resistance of the can bottom with the can bottom shape shown in Figs. 1 and 2 and the can bottom with the can bottom shape shown in Fig. 3 (a).

In the can body shape shown in Fig. 1 and Fig. 2, the dimensions are: plate thickness t = 0.185mm, β = 74 °, h = 3.3mm, m = 1.8mm, can inner diameter d = 52.5mm Then, the steel seamless can was drawn and ironed. The internal pressure of the can body, when the pressure difference between the inside the outside and the can at room temperature was gradually raised from Okgi / cm ² until 5 kgf / cm ^2, and returned to the original 0 kg ip / cm ² by lowering thereafter the internal pressure gradually A test was conducted to measure the amount of displacement at the center of the bottom wall. The broken line in FIG. 1 indicates a state in which the bottom of the can is displaced to the maximum.

The result is shown in Fig. 4 (a). In the graph, the upper right corner represents the origin at the origin, the vertical axis represents the displacement (mm) at the center, and the horizontal axis represents the can pressure (kgf / cm ² ). State as a result, the pressure difference between the external cans internal pressure although displacement from the initial shape of the bottom wall central portion at the time of a 5 kgf / cm ² was about 1.5 mm, which restore the internal pressure in but remains slight deformation can bottom, in the range without any problem, the can is up to pressure differences 5kgi / cm ² to poor deformation such packs ring It was confirmed that they did not have sufficient pressure resistance.

Example 3

 A similar experiment was performed on a steel seamless can having the shape shown in Fig. 3 (a). The dimensions of the can are as follows. Body thickness t = 0.185, β = 88. , H = 2.4 mm, m = 1.8 mm, d = 52.5 mm. The result is shown in Fig. 4 (b). It was confirmed that the can body showed substantially the same results. Experimental example

To determine the appropriate range of the can internal pressure for obtaining manometry aptitude, create a positive pressure supply trial canned changing the set pressure of the can internal pressure in the range of 0 to 1 kgf / cm ² per cans, they A punching test was carried out on the test cans, and a punching test was conducted on positive pressure cans. In a similar experiment, negative pressure test cans were prepared by changing the set pressure within the can pressure range of 0 to 10 kgf / cm ² , and a negative pressure punching test was performed at the bottom of the can. The can body used was a 250 g 2-piece can of a steel can laminated with a PET film. The results are shown in the can pressure-frequency distribution curve in Fig. 5. In Fig. 5, triangles indicate positive pressure cans, and X indicates negative pressure cans. The horizontal axis (pressure in the can) for negative pressure cans indicates the absolute value without the minus sign. The vertical axis is the detected vibration frequency.

From the graph of positive pressure canned, approximately 0. 2~0. 8 kgi / cm ² is preferably 0. 2~0. 6 kgf / cm ² in the range of the temperature above the oscillation frequency with respect to the can pressure increase gradient It can be seen that it is large and has high detectivity. Further, this range almost coincides with the slope of the negative pressure canned beating inspection curve, and it can be understood that the internal pressure inspection aptitude has almost the same discrimination ability as that of the negative pressure canned.

As described above, according to the present invention, the internal pressure of the can is 0.2 to 0.8 kgf / cm ^2, preferably 0.22 to 0.6 kgf / cm ² , In addition, seamless thin-walled cans can achieve the pressure resistance of the bottom of the can that withstands the increase in internal pressure during retort processing, and because the internal pressure of the can is small, the can is filled and sealed. It can reliably detect spoiled cans by internal pressure inspection. Industrial applicability

 The low-positive-pressure cans having the suitability for internal pressure inspection according to the present invention and the can bodies thereof can be used for decay of low-acid beverages and the like. And the ability to detect spoiled cans is high, so it is particularly useful as cans and their cans that require high detectability of spoiled cans, such as canned low-acid beverages, which are extremely susceptible to spoilage and decay. It is.

Claims

The scope of the claims 1. A can that is filled and sealed so that the internal pressure of the can is at least positive with respect to the outside air pressure, and the internal pressure of the can is 0.2 to 0.8 kgi / cm ² at room temperature. A low positive pressure can with internal pressure inspection suitability, characterized in that it has an internal pressure inspection suitability. 2. The low positive pressure can according to claim 1, wherein the set internal pressure of the can is a filled and sealed can, maintaining an accuracy of ± 0.2 kgf / cm ² .  3. The low positive pressure can according to claim 1, wherein the body and the bottom are cans hermetically sealed in a seamless can body integrally molded.  4. The low sunlight according to claim 3, wherein the seamless can body has an annular grounding portion at the bottom near the outer peripheral portion, and a substantially flat portion inside the annular grounding portion. Pressure canned.  5. The low positive pressure can according to claim 1, wherein the content of the can is a low-acid beverage, which is subjected to retort sterilization after filling and sealing.  6. The low positive pressure can according to claim 1 or 2, wherein the can is brought into a positive pressure state by a gas replacement method.  7. The low-yang B-rollo according to claim 1, wherein the suitability for internal pressure test is a suitability for percussion.  8. The low positive pressure can according to claim 1 or 2, wherein the suitability for the pressure test is a suitability for an internal pressure test by measuring a displacement of an outer peripheral portion of the can with respect to a change in the internal pressure.  9. The low positive pressure can according to claim 1, wherein the suitability for the internal pressure test is a suitability for an internal pressure test by measuring a reaction force of an outer peripheral portion of the can with respect to a change in the internal pressure. 10. The body and the bottom are seamlessly and integrally formed, and the bottom has an annular grounding portion (3, 11, 21, 26, 31) near the outer peripheral portion, and the inside of the annular grounding portion. Constitutes a 內 -side riser wall (4, 1, 2, 22) that rises inward of the can, and has a substantially flat shape inside the inner riser wall. A can body for low positive pressure cans having a suitability for internal pressure inspection, characterized by forming a bottom wall (6, 14, 27, 34) having a height of 6 mm. 1 1. At the bottom of the inner riser wall (4, 1, 2, 22) of the annular grounding part, an annular bead (5, The can according to claim 10, wherein 13, 16, 23, 32) is formed.  12. The ground diameter of the can bottom is 70 to 98% of the can body diameter, and the flat part of the can bottom is 60 to 90% of the ground diameter. Body.  1 3. The can body according to claim 10, 11 or 12, wherein the inclination angle of the inner rising wall (4, 1, 2, 22) is 65 to L10 °.  14. The can body according to claim 11, wherein the annular bead (5, 13, 16, 23, 32) has a gentle slope extending from the top to the bottom wall. .  15. The low-yang according to claim 10 or 11, wherein the thickness of the bottom of the can is 0.15 to 0.25mm for steel or 0.25 to 0.35 for aluminum material. Pressure can body.