JPH08318563A - Continuous production of hollow container - Google Patents

Abstract

PURPOSE: To continuously produce a hollow container made of a saturated polyester resin. CONSTITUTION: To the bottom part of a biaxially stretched blow molded hollow container molded by biaxially stretching blow molding, a shield plate 2A having the shape fitted to the bottom part of the hollow container and having a slit is arranged and, by heating the bottom part of the hollow container from below through the slit, the bottom part of the hollow container is crystallized and, next, the shield plate 2A is detached from the hollow container and the bottom part of a new hollow container is heated and crystallized in the same way. The shield plate is not cooled at the time of heating but cooled or allowed to stand to cool before the heating for crystallization of the hollow container succeeding to the completion of heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing a hollow container made of a saturated polyester resin, and more specifically, to a pressure resistance and heat resistance during heat sterilization of contents, which is excellent in impact resistance. The present invention relates to a method for manufacturing a heat resistant hollow container.

[0002]

2. Description of the Related Art The inventors of the present invention have heretofore used a pressure- and heat-resistant self-standing hollow container manufacturing method, in which a plurality of legs are radially bulged around a center of a bottom portion, and the legs and the legs are joined together. In the case of a bottom structure with a valley line formed in between, by crystallizing the bottom where the stress due to the internal pressure of the hollow container concentrates, the bottom may creep deform during heat sterilization of the container and lose self-standing stability. I found it disappeared. However,
Regarding the above-mentioned bottom crystallization, when the crystallization time is shortened to increase productivity, the bottom of the hollow container causes heat shrinkage, and when the heat shrinkage of the bottom of the hollow container is suppressed, the crystallization time becomes longer and the productivity is improved. There was a drawback that it did not go up.

[0003]

DISCLOSURE OF THE INVENTION As a result of earnest research, the researchers of the present invention have used a shield plate, and while the shield plate is not always cooled and the container bottom is not heated, the vicinity of the container bottom is kept. Cool the shield plate to a temperature at which heat contraction can be suppressed, and do not perform this cooling while heating the bottom of the container.By allowing the heat of the bottom of the container to raise the temperature of the shield, the vicinity of the bottom of the container The present invention has been found to reduce the time of exposure to a temperature at which heat shrinks to suppress heat shrinkage in the vicinity of the bottom of the container, and gradually increase the temperature of the shielding plate to shorten the crystallization time of the bottom of the container. Reached

That is, according to the present invention, a shielding plate having a shape in which a specific portion is opened and which fits with the bottom of the container is installed between the bottom of the biaxially stretched blow hollow container and the heating device, and the bottom of the container is specified. By heating and crystallizing the part selected from the parts without impairing the productivity, the bottom part does not deform by creep during heat sterilization of the container and the self-sustaining stability is not lost, and it also has chemical resistance. An excellent method for producing a pressure- and heat-resistant self-standing hollow container is provided.

[0005]

The first invention of the present invention is as follows:
At the bottom of the biaxially stretched blow hollow container molded by biaxially stretched blow molding, a shielding plate having a shape that fits the bottom of the hollow container and having a slit is installed, and a hollow is formed from below the slit. A method of crystallizing the bottom of the hollow container by heating the bottom of the container, then detaching the shield plate from the hollow container, and heating and crystallizing the new hollow container in the same manner. In this case, the shielding plate is not cooled, and after the heating is completed, until the heating for the subsequent crystallization of the hollow container, the shielding plate is cooled or allowed to cool. It is a manufacturing method.

A second aspect of the present invention is formed by biaxial stretch blow molding, in which a plurality of legs are radially bulged around the bottom center of the bottom, and between the legs. It has a self-supporting structure with a valley line formed, and (a) below.
Alternatively, at the bottom of the biaxially stretched blow hollow container having (b), a shielding plate having a shape fitting with the bottom of the hollow container and having a slit is installed, and the bottom of the hollow container is provided from below the slit. At least one of the following (A) to (E) on the bottom of the hollow container is crystallized by heating, and then the shielding plate is detached from the hollow container and heated in the same manner for a new hollow container. A method of crystallizing, wherein the shielding plate is not cooled during its heating, and the shielding plate is cooled or released after the heating is completed and before the heating for the subsequent crystallization of the hollow container. It is a continuous production method of a hollow container made of a saturated polyester resin to be cooled.

(A) The neck and neck, the support ring and the lower part of the support ring are crystallized. (B) The mouth and neck or the mouth and neck and the support ring have an inner diameter of 60 to 80% with respect to the outer diameter, and stress and strain are relaxed by heating, and the lower portion of the support ring is crystallized. thing. (A) Bottom center. (B) Peripheral area around the center of the bottom. (C) A portion near the center of the bottom of the valley line. (D) The part from the edge of the peripheral part of the bottom center part of the leg part to the ground contact part. (E) A portion between (C) and (D).

The present invention will be described in detail below.

The resin used for the hollow container made of the saturated polyester resin of the present invention is preferably a saturated polyester resin whose main repeating unit is ethylene terephthalate, and the saturated polyester resin contains a homopolymer of polyethylene terephthalate as a main component.

As the saturated polyester resin, a part of the terephthalic acid component is aromatic dicarboxylic acid such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid. Alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid; aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid; P-β-
A copolymer obtained by substituting at least one other difunctional carboxylic acid such as hydroxyethoxybenzoic acid and oxyacid such as ε-oxycaproic acid for copolymerization can be used.

In the saturated polyester resin, a part of the ethylene glycol component is, for example, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentylene glycol, diethylene glycol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol,
It may be a copolymer obtained by substituting one or more polyfunctional compounds of other glycols such as 2,2 (4′-β-hydroxyethoxyphenyl) sulfonic acid and their functional derivatives, and copolymerizing them.

The saturated polyester resin used in the container of the present invention preferably has an intrinsic viscosity of 0.7 to 1.0,
It is particularly preferably 0.75 to 0.90.

Further, the saturated polyester resin used in the present invention may appropriately contain additives such as colorants, heat deterioration inhibitors, antioxidants, ultraviolet absorbers, antistatic agents, antibacterial agents and lubricants. .

In the present invention, as the heating device, a device that generates heat can be used, and specifically, an infrared heater, hot air, an infrared lamp, a quartz tube heater, a high frequency heating device and the like can be used. Further, it goes without saying that a heat source other than this can be used.

In the present invention, the shielding plate is made of a metal such as aluminum, iron or copper or a heat resistant resin.
Ceramic or the like can be used, and the surface of the shielding plate is preferably smooth.

In the present invention, a shielding plate having a slit is installed at the bottom of a biaxially stretched blow hollow container, and the bottom of the hollow container is heated from below the slit to crystallize the bottom of the hollow container. In, a method of desorbing the shield plate from the hollow container and heating and crystallizing it in the same manner for a new hollow container, without cooling the shield plate at the time of heating,
It is a continuous manufacturing method of a hollow container in which the shielding plate is cooled or allowed to cool after the heating is completed and before the subsequent heating for crystallization of the hollow container. The shielding plate is preferably cooled or allowed to cool to a temperature not exceeding the glass transition temperature of the resin used in the container.

The shielding plate according to the present invention comprises (A) the center of the bottom of the bottom of the biaxially stretched blow hollow container and / or (B) the periphery of the center of the bottom and / or (C) the bottom of the valley. A portion close to the central portion and / or (D) a portion from the edge of the peripheral portion of the leg portion to the ground portion and / or
(E) A portion corresponding to a portion selected from the portion between (C) and (D) is opened and has a shape that fits with the bottom of the container. Among the combinations (A) to (E), the combination containing (B) and (C) is particularly preferable, and (E) can be combined as necessary. The shielding plate has a shape that fits with the bottom of the container, and the engraving for fitting is made up of 60 of the bulging portion of the leg.
% Or more, preferably 80% or more. As a result, heat shrinkage due to heating can be prevented, and only the portion corresponding to the opening of the shielding plate can be heated and crystallized with high accuracy.

On the other hand, when the shielding plate is repeatedly used without cooling when the bottom of the container is not heated, the temperature of the shielding plate eventually becomes equal to or higher than the glass transition temperature of the resin used in the container as the heating time elapses. The possibility of significant heat shrinkage near the bottom of the container is extremely high, and even if the temperature of the shielding plate does not rise above the glass transition temperature of the resin used for the container, the temperature of the shielding plate causes the crystals at the bottom of the container to crystallize. The crystallization state varies, which causes a poor crystallization state at the bottom of the container. Therefore, it is possible to control the temperature of the shielding plate at a certain temperature. For example, it is possible to control the temperature of the shield plate to about room temperature.In this case, the heat shrinkage near the bottom of the container is almost suppressed, but the time required for crystallization of the bottom is higher when the temperature is controlled at a higher temperature. It will be longer than that and productivity will be extremely poor. Further, it is possible to control the temperature of the shielding plate to a high temperature within the temperature below the glass transition point of the resin used for the container. In this case, the crystallization time at the bottom is shortened and the productivity is improved. There is a drawback that heat contraction occurs near the bottom.

Therefore, the temperature of the shield plate is not constantly controlled to a constant temperature, and only when the container bottom is not heated, the shield plate is cooled to a temperature at which heat contraction near the container bottom can be suppressed and the container bottom is heated. By not performing this cooling during this period and allowing the temperature of the shielding plate to rise by the heat of heating the bottom of the container, it is possible to shorten the time exposed to the temperature at which heat contraction occurs near the bottom of the container. The heat shrinkage is suppressed, and the temperature of the shielding plate gradually rises, so that the crystallization time at the bottom of the container can be shortened.

As a specific example of the manufacturing apparatus of the present invention, there is an apparatus shown in FIG. In FIG. 1, the basic configuration is
The bottom plate 7, the heating device 3 is installed on the bottom plate 7, and the shielding plate 2A is installed above the bottom plate 7. This shielding plate has the same engraving as the shape of the bottom of the biaxially stretched blow hollow container 1A, and the bottom of the biaxially stretched blow hollow container is (A) the center of the bottom, (B) the center of the bottom, and (C).
At least one selected from a portion near the center of the bottom of the valley line portion, (D) a portion from the peripheral edge of the leg portion to the ground contact portion, and (E) a portion between (C) and (D) It is a shield plate made of aluminum having an opening corresponding to a portion of the place.

The shielding plate has a cooling medium tube connected to the cooling medium pipe provided for cooling, and a cooling medium pipe provided inside the shielding plate for cooling the shielding plate.
Further, a shield plate support plate 6 that supports the shield plate 2A, a container support plate 5 that supports the biaxially stretched blow hollow container 1A installed above it with a support ring 22A, an upper plate 4 installed above it, and an upper plate 4 The container 8 for lifting and lowering and supporting the container, the container pressing plate and container supporting plate 10 for connecting the container lifting and loading cylinder 8 and the container supporting plate 5, and the bottom plate 7 stand upright. Further, it is composed of a shield plate support plate 6, a container support plate 5, and a column 9 that supports the upper plate 4.

A heating device 3 installed below the shield plate 2A.
The heat generated from is transmitted to the bottom of the biaxially stretched blow hollow container through the opening of the shielding plate, and the specific portion of the bottom can be crystallized by heating the specific portion of the bottom for a certain period of time. At this time, since the shielding plate shields the bottom of the container other than the specific part to be crystallized, the heat generated by the heating device is not directly transferred to the bottom of the container other than the opening. It does not crystallize. At this time, the temperature of the surface of the shielding plate when it comes into contact with the biaxially stretched blow hollow container is such that when the temperature of the shielding plate is not adjusted while the container bottom is being heated, the temperature gradually rises due to the heat generated by the heating device. It is preferable that the temperature is not higher than the Tg of the thermoplastic polyester resin. In the present invention,
It is convenient and preferable to install the cooling medium pipe on the side of the bottom of the container, but it is also possible to install it on other parts.

The shield plate 2A has a shape that fits with the bottom of the container. It is preferable that the shield plate and the container bottom are in contact with each other at the time of fitting, but there may be a gap as long as a portion other than a desired portion is not crystallized. In addition, in order to improve the adhesion, a method of manufacturing by pressing the container can be used. When the container is installed on the container support plate at a position substantially corresponding to the engraving on the shield plate, when the bottom part is inserted into the shield plate, the container rotates so that the bottom part matches the shape of the shield plate, The bottom of the container and the shield can be fitted well.

When crystallizing the bottom of the container, the biaxially stretched blow hollow container may or may not be subjected to internal pressure. When manufacturing by applying internal pressure, as shown in FIG.
The apparatus includes a container inner pressure load cap 11 attached to a mouth / neck portion 21 of a container, a compressed air supply tube 12 for supplying compressed air for applying an internal pressure to the container, and a compressed air sent to the container. The packing 13 is configured to prevent leakage from the portion 21. Compressed air having an arbitrary pressure can be fed into the container from the compressed air feeding tube 12 to apply an internal pressure.

In the saturated polyester resin hollow container according to the second aspect of the present invention, the bottom portion radially bulges out a plurality of legs around the center of the bottom, and forms a valley line portion between these legs. It consists of a bottom with a self-supporting structure,
In addition, the specific portion is a crystallized portion, and the heated and crystallized portion at the bottom of the hollow container is the specific portion, which is a saturated polyester resin hollow container. More specifically, the hollow container obtained in the second invention is a hollow container having pressure resistance and heat resistance having the following (a) or (b). (A) Crystallized mouth / neck, support ring, and lower support ring. (B) The mouth and neck or the mouth and neck and the support ring have an inner diameter of 60 to 80% with respect to the outer diameter, and stress and strain are relaxed by heating, and the lower portion of the support ring is crystallized. thing.

In the hollow container made of the saturated polyester resin according to the second aspect of the present invention, the heat crystallization portion of the hollow container is (A) to
It has at least one of (E), among which (A) + (B) + (C), (A) + (B) + (C)
+ (D), (B) + (C) + (D), and (B) +
The combination of (C) is preferable, and particularly preferably,
(A) + (B) + (C), (A) + (B) + (C) +
It is a combination of (D) and (B) + (C) + (D).

The hollow container obtained by the production method of the present invention, in which a specific portion is crystallized, has improved chemical resistance to a lubricant used in a conveyor line of a filling factory and also suppresses the occurrence of stress cracks. You can Further, by whitening and crystallizing the bottom portion, the contrast between the transparent portion and the white portion leads to an improvement in aesthetic appearance.

[0028]

The present invention will be described in detail below with reference to examples. Example 1 Polyethylene terephthalate (IV = 0.84) was injection-molded to obtain a bottomed tubular preform having a resin amount of 50.0 g. The (a) mouth and neck of this preform, the support ring and the lower part of the support ring were heated by an infrared heater to be crystallized. After reheating this bottomed tubular preform, it was placed in a blow mold and stretched in the circumferential direction by air blow while being stretched in the axial direction by a stretch rod to obtain a biaxially stretched blow hollow container. . At this time, while the body of the mold was heated to 120 ° C., heat fixing was performed for about 10 seconds, and then air at room temperature was circulated in the blow container to cool it, thereby obtaining a biaxially stretched blow hollow container. .

Next, between the bottom of the biaxially stretched blow hollow container and the infrared heater (heating device), (A) the center of the bottom, (B) the center of the bottom, and (C) the valley line. Of the aluminum shield plate (FIG. 4 and FIG. 4 and FIG. (Shown in FIG. 5), a shield plate having a temperature of 40 ° C. was installed in advance. Next, the bottom of the container is fitted and adhered to a shielding plate (no cooling is performed during heating), the portions (A) to (D) are crystallized by heating, and the hollow container 1B shown in FIG. Thirty
9 mm, body diameter 92 mm) were obtained. As shown in FIG. 6, the bottom of the hollow container 1B is a self-supporting structure in which five legs swell radially around the center at equal intervals and valley lines are formed between the legs. And (A) the center of the bottom, (B) the periphery of the center of the bottom, (C) the portion near the center of the bottom of the valley line, and (D) the edge of the periphery of the leg. The portion further reaching the grounded portion was crystallized, and the density of the crystallized portion was 1.361 to 1.376 g / cm ³ . Also, the time required to crystallize the bottom of the container is 20
It was 0 seconds, and the filling capacity with full water up to the top surface of the mouth of the hollow container 1B was 1530 ml.

In this hollow container 1B, at 5 ° C., 2.
After filling with 5 gas volumes of carbonated water and capping, the carbonated water returned to room temperature, and then a hot water shower at 70 ° C. was applied for 30 minutes. Then, it was showered with water at 20 ° C. for 10 minutes to cool, and the total height of the bottle and the deformation rate of the body diameter were measured. As a result, the total height of the hollow container is 307 mm.
The deformation rate of the body diameter was 0.9%. Next, when 12 filled containers were placed upright on the concrete from a height of 2.0 m, the bottom of the container was not broken in all cases.

Example 2 In Example 1, (b) the mouth and neck as a preform and the support ring had an inner diameter of 60 to 8 with respect to an outer diameter.
It is 0%, stress and strain are relaxed by heating, and the one under the support ring is heated by an infrared heater to be crystallized, and further, the shielding plate shown in FIG. 7 and FIG. (B) Peripheral part of the bottom center of the blow hollow container, (C) A part near the bottom center of the valley line part, and (D)
The same procedure was performed except that the portion from the edge of the peripheral portion of the leg portion to the ground contact portion was crystallized. The bottom of the resulting container is shown in FIG.
As shown in Figure 5, it has a self-standing structure in which five legs swell radially around the center at equal intervals and valley lines are formed between the legs. The peripheral portion of the bottom center portion, (C) the portion near the bottom center portion of the valley line portion, and (D) the portion from the edge of the peripheral portion to the grounding portion are crystallized, and the density of the crystallized portion is Is 1.361 to 1.37
It was 6 g / cm ³ . The time required to crystallize the bottom of the container was 200 seconds, and the hollow container had a filling capacity of 1530 ml up to the top of the mouth, a total height of 309 mm,
The body diameter was 92 mm.

This hollow container was filled with 2.5 gas volumes of carbonated water at 5 ° C., capped, and after the carbonated water returned to room temperature, a hot water shower at 70 ° C. was applied for 30 minutes. Then, it was showered with water at 20 ° C. for 10 minutes to cool, and the total height of the bottle and the deformation rate of the body diameter were measured. As a result, the total height of the hollow container was 307 mm, and the deformation rate of the body diameter was 0.9%. Next, when 12 filled containers were placed upright on the concrete from a height of 2.0 m, the bottom of the container was not broken in all cases.

Comparative Example 1 The same procedure as in Example 1 was carried out except that (a) the neck and neck of the preform, the support ring and the lower part of the support ring were not crystallized, and the bottom of the container was not crystallized. It was The hollow container has a filling capacity of 1 up to the top of the mouth.
The total height was 530 ml, the total height was 310 mm, and the body diameter was 92 mm.
This hollow container was filled with 2.5 gas volume of carbonated water at 5 ° C., capped, and after the carbonated water returned to room temperature, a hot water shower at 70 ° C. was applied for 30 minutes. Then, it was cooled by showering with water at 20 ° C. for 10 minutes. The bottom of the container of the bottle was protruding, and there was no self-sustaining stability.

Comparative Example 2 In Example 1, the shielding plate was cooled to a temperature of about room temperature,
Even when the bottom of the container was heated, the temperature of the shielding plate was kept at about room temperature without stopping the circulation. The density of the crystallized part at the bottom of the container is
Although it was crystallized to have a weight of 1.361 to 1.376 g / cm ³ , the shielding plate cools the bottom of the container.
It took time to reach the crystallization temperature, and the time required for crystallization was as long as 280 seconds, resulting in poor productivity.

Comparative Example 3 In Example 1, the temperature of the shielding plate was controlled to 65 ° C., which is close to the glass transition temperature of the polyethylene terephthalate resin, and the temperature of the shielding plate was controlled without stopping the circulation even when the bottom of the container was heated. The density of the crystallized portion at the bottom of the container is 1.3.
The time required for crystallization to be 61 to 1.376 g / cm ³ was shortened to 120 seconds, but the bottom of the hollow container caused thermal contraction and the full water filling capacity was decreased. Also,
Even if the volume of the bottle is increased in anticipation of the amount of heat shrinkage, there is variation in the amount of heat shrinkage.
Have difficulty.

[0036]

As described above, according to the present invention, the shielding plate is cooled to a temperature at which heat contraction near the container bottom can be suppressed only when the container bottom is not heated, and this cooling is performed while the container bottom is heated. The heat of the bottom of the container is heated by heating the bottom of the container and gradually increasing the temperature of the shield by crystallizing a specific part of the bottom of the container. It is possible to obtain a pressure- and heat-resistant self-supporting hollow container which can suppress shrinkage, can shorten crystallization time, and also have improved pressure resistance and heat resistance during heat sterilization of contents, and improved impact resistance.

[Brief description of drawings]

FIG. 1 is a front view of the device of the present invention.

FIG. 2 is an enlarged view of the main part (F part) of FIG.

FIG. 3 is a sectional view of a hollow container 1B of the present invention.

FIG. 4 is a plan view of a shield plate 2A of the present invention.

FIG. 5 is a sectional view taken along the line A-A ′ of the shielding plate 2A of the present invention.

FIG. 6 is a bottom view of the hollow container of the present invention.

FIG. 7 is a plan view of a shield plate 2B of the present invention.

FIG. 8 is a B-B ′ sectional view of the shielding plate 2B of the present invention.

FIG. 9 is a bottom view of the hollow container of the present invention.

[Explanation of symbols]

1A Biaxially stretched blow hollow container 1B Saturated polyester resin hollow container 2A, 2B Shielding plate 3 Heating device 4 Upper plate 5 Container support plate 6 Shielding plate support plate 7 Bottom plate 8 Cylinder for lifting / loading container 9 Struts 10 Container pressure load cap Push plate / container support plate 11 Internal pressure load cap 12 Compressed air feed tube 13 Packing 14 Cooling water tube 15 Cooling water pipe 16 Opening 21 Mouth neck 22A Support ring 22B Support ring lower 23 Shoulder 24 Body 25 Bottom 31A Bottom center part 31B Bottom center part 31C Bottom part of valley line part Close to center part 31D Bottom part of leg part Center part from edge of peripheral part to ground contact part 31a Opening part corresponding to bottom center part 31b Bottom part Peripheral part of the central part Corresponding opening 31c Bottom of the valley line part Near the central part Corresponding opening 3 Portions corresponding openings 32 leg 33 valley portion reaching to the ground portion of the edge of the peripheral portion of the bottom center of the d legs

Claims (2)

[Claims] 1. A biaxially stretched blow hollow container molded by biaxially stretched blow molding is provided at the bottom thereof with a shielding plate having a shape that fits with the bottom of the hollow container and having a slit. By heating the bottom of the hollow container from below the slit to crystallize the bottom of the hollow container, then remove the shield plate from the hollow container and heat crystallize the new hollow container in the same manner. The shielding plate is not cooled during the heating, and the shielding plate is cooled or allowed to cool after the heating is completed and before the heating for the subsequent crystallization of the hollow container. A method for continuously producing a hollow container made of a saturated polyester resin. 2. Molded by biaxial stretch blow molding,
A plurality of legs are radially bulged around the center of the bottom of the bottom, and a valley line portion is formed between these legs, and the structure is self-supporting, and (a) or ( In the bottom of the biaxially stretched blow hollow container having b), a shielding plate having a shape that fits with the bottom of the hollow container and having a slit is installed, and the bottom of the hollow container is heated from below the slit. By doing the following (A) ~ (E) of the bottom of the hollow container
Crystallize at least one part of the, then remove the shield plate from the hollow container, in the same manner for a new hollow container,
A method of crystallizing by heating, wherein the shielding plate is not cooled during the heating, and the shielding plate is cooled or cooled after the heating is finished and before the heating for crystallization of the subsequent hollow container. A method for continuously producing a hollow container made of a saturated polyester resin, which is characterized by allowing to cool. (A) Crystallized mouth / neck, support ring, and lower support ring. (B) The mouth and neck or the mouth and neck and the support ring have an inner diameter of 60 to 80% with respect to the outer diameter, and stress and strain are relaxed by heating, and the lower portion of the support ring is crystallized. thing. (A) Bottom center. (B) Peripheral area around the center of the bottom. (C) A portion near the center of the bottom of the valley line. (D) The part from the edge of the peripheral part of the bottom center part of the leg part to the ground contact part. (E) A portion between (C) and (D).