Manufacturing method for double walled container

Abstract

A manufacturing method of double walled container comprises preparing a parison having a rigid outer layer and a flexible inner layer, enclosing the parison within a mold including split mold halves, thereby forming a molded parison including a pre-blow cylindrical section, a pre-blow conical bottom section, a pre-blow bottom projection, and a lower parison excessive burr, blowing gas into an inside of the molded parison, thereby forming a blown parison including a cylindrical section and a bottom section, the bottom section including a bottom projection, and removing the lower parison excessive burr from the blown parison, wherein the flexible inner layer is fixed to the rigid outer layer in the bottom projection.

Claims

1. A manufacturing method of double walled container, comprising: preparing a parison having a rigid outer layer and a flexible inner layer, enclosing the parison within a mold including split mold halves, thereby forming a molded parison including a pre-blow cylindrical section, a pre-blow bottom section, a bottom projection, and a lower parison excessive burr, blowing gas into an inside of the molded parison, thereby forming a blown parison including a cylindrical section and a conical bottom section, the conical bottom section including the bottom projection, and removing the lower parison excessive burr from the blown parison, wherein the flexible inner layer is fixed to the rigid outer layer in the bottom projection, and wherein the split mold halves comprise mold cylindrical sections for forming the cylindrical section, mold conical bottom sections for forming the conical bottom section, mold bottom projection forming sections for forming the bottom projection, and parison excessive burr receiving recesses for receiving the lower parison excessive burr.

2. The manufacturing method according to claim 1, further comprising: installing a standing skirt member around the bottom section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic longitudinal cross-sectional view of a double walled container manufactured by an embodiment of method of manufacturing a double walled container according to the present invention.

(2) FIG. 2 is an enlarged schematic cross-sectional view of the cylindrical lateral wall of a double walled container manufactured by the first embodiment of method of manufacturing a double walled container taken along line II-II in FIG. 1.

(3) FIG. 3A is a schematic front view of the bottom section of a split mold and FIG. 3B is a schematic left side view of the bottom section of the right side split mold half of FIG. 3A.

(4) FIG. 4A is a schematic front view of a lower part of a parison after being sandwiched between the two split mold halves and FIG. 4B is a schematic left side view of the lower part of the parison after being sandwiched between the two split mold halves.

(5) FIG. 5A is a schematic front view of a lower part a parison after being sandwiched between the two split mold halves and blown to expand, FIG. 5B is a schematic left side view of the lower part of the parison after being sandwiched between the two split mold halves and blown to expand and FIG. 5C is a partial cross-sectional view taken along line Vc-Vc shown in FIG. 5A.

(6) FIG. 6A is a schematic front view of a lower part of a double walled container after the excessive burr of the parison is cut off after the molding process, FIG. 6B is a schematic left side view of the lower part of the double walled container after the excessive burr of the parison is cut off after the molded process and FIG. 6C is a partial cross-sectional view taken along line VIc-VIc shown in FIG. 6A.

(7) FIG. 7A is a schematic cross-sectional view of a first exemplar bottom projection of an embodiment of double walled container, FIG. 7B is a schematic cross-sectional view of a second exemplar bottom projection of an embodiment of double walled container and FIG. 7C is a schematic cross-sectional view of a third exemplar bottom projection of the embodiment of double walled container, while FIG. 7D is a schematic cross-sectional view of a fourth exemplar bottom projection of the embodiment of double walled container and FIG. 7E is a schematic lateral view of the fourth exemplar bottom projection of an embodiment of double walled container.

(8) FIG. 8 is a schematic perspective view of a skirt member.

BEST MODE FOR CARRYING OUT THE INVENTION

(9) Now, a method of manufacturing of double walled container according to the present invention will be described below by referring to the drawings. As shown in FIG. 1, a double walled container 10 manufactured by an embodiment of method of manufacturing the same according to the present invention comprises a mouth section 12, a neck/shoulder section 14, a cylindrical section 18, a bottom section 20, a bottom projection 21, a cap 24 having a pump 22 and a skirt member 26.

(10) The double walled container 10 is formed by blow molding of a molding material that is supplied in the form a parison P. As may easily be imaginable by seeing the enlarged cross-sectional view of the cylindrical section 18 shown in FIG. 2, the parison P for forming the double walled container 10 comprises a flexible inner layer 36, which includes three layers of a low density polyethylene (LDPE) layer 31, an adhesive layer 32 typically made of a polyolefin-based adhesive resin material and an ethylene-vinyl alcohol copolymer layer (EVOH) layer 33, and a rigid polypropylene (PP) outer layer 38, which are arranged in the above-mentioned order from the inside. The outer surface of the flexible inner layer 36 and the inner surface of the rigid outer layer do not show any adhesiveness relative to each other and hence can easily be separated from each other.

(11) As shown in FIG. 6A and FIG. 6B, the split mold halves D1 and D2 for parison blow molding respectively have at their lower parts mold cylindrical sections 61 for forming the cylindrical section 18 of the container to be manufactured, mold skirt member forming/installing small diameter sections 62n for forming the skirt member installing small diameter section 62m, a mold skirt member forming/installing large diameter sections 64n for forming the skirt member installing large diameter section 64m that are located below the sections 62n, the skirt member installing small diameter section 62m and the skirt member installing large diameter section 64m being to be used for installing the skirt member 26 to the container, mold conical bottom sections 66 for forming the bottom section 20 of the container, a mold bottom projection forming sections 68 for forming the bottom projection 21 of the container and parison excessive burr receiving recesses 69 for receiving the parison excessive burr 60 (shown in FIGS. 4A through 5C), which is the part of the parison P located below the part sandwiched between the mold conical bottom sections 66 and the mold bottom projection forming sections 68 of the split mold halves D1 and D2.

(12) A mold ventilation recess forming protrusion 67m for forming a ventilation recess 67n is formed in the mold skirt member forming/installing large diameter section 64n of one of the split mold halves D1 and D2.

(13) Now, the blow molding method using the split mold halves D1 and D2 will be described below. The split mold halves D1 and D2 are arranged vis-à-vis as shown in FIG. 3B. In this state, parison P is inserted between the split mold halves D1 and D2 as indicated by imaginary lines in FIG. 3A and FIG. 3B.

(14) Subsequently, the split mold halves D1 and D2 are put together to enclose the parison P. Then, as a result, the parison P is subjected to a molding operation, after which the parison P is made to have a pre-blow cylindrical section 70 for forming the cylindrical section 18 of the container to be manufactured, a pre-blow conical bottom section 72 for forming the bottom section 20 of the container, a pre-blow bottom projection 74 for forming the bottom projection 21 of the container and a lower parison excessive burr 60. The lower parison excessive burr 60 is a substantially flat burr that extends downward from the pre-blow conical bottom section 72 along the parting line 78 by way of pinch off line PL.

(15) Thereafter, a blow-in operation of blowing gas into the inside of the parison P is executed. Then, as a result, the cylindrical section 18, the bottom section 20 and the bottom projection 21 of the container as shown in FIG. 5A, FIG. 5B and FIG. 5C are molded from the parison. The pinch off line PL and the parison excessive burr 60 are held undeformed.

(16) Then, the parison excessive burr (60) is scraped off along the pinch off line PL from the parison P that has been subjected to a molding operation as shown in FIG. 6A, FIG. 6B and FIG. 6C. Then, as a result, the part of the bottom section 20 located on the parting line 78 where the parison excessive burr 60 has been attached becomes pitching slit forming section PS. As shown in FIG. 6C, the flexible inner layer 36 is exposed in a center region of the bottom 20 and around the bottom projection 21 and the scraped off edge portions of the rigid outer layer 38 become to be disposed at the opposite sides of the scraped off edge portion of the flexible inner layer 36 at the pitching slit forming section PS.

(17) As for the internal configuration of the bottom projection 21, the outer layer embraces the inner layer without leaving any gap between them as shown in FIG. 7A.

(18) However, a space may exist in the inside of the flexible inner layer 36 in the inside of the bottom projection 21 as shown in FIG. 7B.

(19) The split mold halves D1 and D2 may be provided at the abutting sides thereof with respective projections such that they are located obliquely relative to each other so as to make the laminate of the flexible inner layer 36 and the rigid outer layer 38 meander in the inside of the bottom projection 21 as shown in FIG. 7C.

(20) Additionally or alternatively, the split mold halves D1 and D2 may be provided at the abutting sides thereof with respective projections such that they are located exactly vis-à-vis so as to produce a hole 90 that runs through both the flexible inner layer 36 and the rigid outer layer 38 in the inside of the bottom projection 21 as shown in FIG. 7D.

(21) Then, the skirt member 26 as shown in FIG. 8 is installed to the molded double walled container 10 from which the parison excessive burr 60 has been scraped off.

(22) The skirt member 26 is cylindrical and sealed at the bottom thereof. A skirt member internal peripheral projection 26b, which is to be engaged with the skirt member installing small diameter section 62m, is formed at the upper end of the inner surface of the skirt member 26. A skirt member ventilation recess 26n is formed at the skirt member internal peripheral projection 26b so as to cooperate with the ventilation recess 67n of the mold skirt member forming/installing large diameter section 64n of one of the split mold halves D1 and D2 for the purpose of ventilating the inside of the skirt member 26.

(23) It may be needless to say that the ventilation recess 67n of the mold skirt member forming/installing large diameter section 64n and the skirt member ventilation recess 26n are not required when the bottom of the skirt member 26 is not sealed.

(24) After the contents is filled in the double walled container 10 that is prepared in the above-described manner, the flexible inner layer 36 and the rigid outer layer 38 will be separated from each other to produce a gap at least at the pitching slit forming section PS, where the flexible inner layer 36 and the rigid outer layer 38 are exposed at the part of a center region of the bottom section 20 from which the parison excessive burr 60 has been scraped off. Then, as a result, when the contents are consumed and depleted and the internal capacity of the flexible inner container is reduced, external air gets into the space produced between the flexible inner container and the rigid outer container so that the reduced internal capacity of the flexible inner container is maintained in the rigid outer container. On the other hand, since the bottom section of the flexible inner container is securely held to the bottom section of the rigid outer container by the bottom projection 21, the bottom section of the flexible inner container would not separate and rise up from the bottom section of the rigid outer container.

REFERENCE CHARACTERS

(25) P: parison

(26) PL: pinch off line

(27) PS: pitching slit forming section

(28) 12: mouth section

(29) 18: cylindrical section

(30) 20: bottom section

(31) 21: bottom projection

(32) 26: skirt member

(33) 36: flexible inner layer

(34) 38: rigid outer layer

(35) 60: parison excessive burr

(36) 61: mold cylindrical section

(37) 62m: skirt member installing small diameter section

(38) 62n: mold skirt member forming/installing small diameter section

(39) 64m: skirt member installing large diameter section

(40) 64n: mold skirt member forming/installing large diameter section

(41) 66: mold conical bottom section

(42) 67n: ventilation recess

(43) 68: mold bottom projection forming section