EP1724102A1

EP1724102A1 - Mandrel for molding container bottom and method of manufacturing the same

Info

Publication number: EP1724102A1
Application number: EP04718735A
Authority: EP
Inventors: Yoji; C/O Shikoku Kakoki Co. Ltd. NISHIO
Original assignee: Shikoku Kakoki Co Ltd
Current assignee: Shikoku Kakoki Co Ltd
Priority date: 2004-03-09
Filing date: 2004-03-09
Publication date: 2006-11-22
Also published as: WO2005084929A1; EP1724102A4

Abstract

The container bottom molding mandrel fitted with a container blank when folding and sealing a portion that is to become a container bottom of a square tubular container blank B into a flat shape includes a tubular mandrel main body 31 having four contacting parts 41 along which four corners of the container blank B lie; a bottom plate 32 for closing the basal end of the mandrel main body 31; and a top plate 33 for closing the distal end of the mandrel main body 31. The mandrel main body 31 is made of a thin thickness pipe molded article. A part 42 having a concave traverse plane is formed between adjacent contacting parts 41.

Description

TECHNICAL FIELD

The present invention relates to a container bottom molding mandrel used when folding and sealing a portion that is to become the container bottom of a square tubular container blank into a flat shape in packaging machines for manufacturing a gable top container filled with drink and the like, and a method of manufacturing the same.

BACKGROUND ART

A conventionally known container bottom molding mandrel of this kind includes a tubular mandrel main body having four contacting parts along which four corners of the container blank lie, a bottom plate for closing the basal end of the mandrel main body, and a top plate for closing the distal end of the mandrel main body, and the mandrel main body is formed through cutting, forging, or casting, and the bottom plate and the top plate are fastened to the mandrel main body by a bolt and the like (e.g., Japanese Laid-Open Utility Model Publication No. S62-199331 ).
Furthermore, in such a mandrel, a cooling water inlet and a cooling water outlet are formed in the bottom plate, a concave part is formed at the back surface of the top plate, the opening of the concave part is covered by a closing plate so as to form a cooling chamber in the concave part, an inlet side communication port and an outlet side communication port are formed in the closing plate, the cooling water inlet and the inlet side communication port are communicated by a feeding side cooling water pipe traveling down through the hollow interior of the mandrel main body, and the cooling water outlet and the outlet side communication port are communicated by a returning side cooling water pipe extending parallel to the feeding side cooling water pipe.
The mandrel top plate is generally known to be formed by stainless steel since the strength to withstand the sealing pressure must be ensured, and the mandrel main body is generally formed by aluminum since lighter weight must be achieved in addition to strength.
The sealing pressure is applied on the mandrel top plate when sealing the bottom part of the blank. The thickness of the mandrel main body must be made large to ensure the strength to withstand the sealing pressure, and thus the weight of the entire mandrel tends to be larger.
Since the mandrel main body is made of aluminum, measures for wear resistance, corrosion resistance and the like are necessary. In particular, the hygienic problem regarding the outer surface of the mandrel, which is the portion that contacts the inner surface of the container, is recently given importance, and a more reliable corrosion resistance is being demanded as a strong medical agent tends to be used in cleaning and sterilizing the mandrel and the surrounding thereof.
Since the bottom plate and the top plate are fastened to the mandrel main body by a bolt and the like, the hygienic problem is becoming more complicating as the medical agent and the like enters the gap between the adjacent members.
No problem arises in cooling the distal end portion of the mandrel since the cooling water circulates to the cooling chamber of the mandrel in the conventional mandrel. However, since portions other than the distal end portion, for example, the peripheral wall portion of the mandrel main body, does not directly contact the cooling water, lack of cooling occurs. In particular, when the machine is for example, stopped, the heater heats the peripheral wall portion of the mandrel main body, thereby increasing the surface temperature of the relevant portion and causing insertion defect of the mandrel due to lowering in the sliding of the carton.
The present invention aims to provide a container bottom molding mandrel of lighter weight that excels in wear resistance and corrosion resistance, and that maintains uniform temperature of the outer surface of the entire mandrel, and the method of manufacturing the same.

DISCLOSURE OF THE INVENTION

A container bottom molding mandrel according to the present invention is mandrel fitted with a container blank when folding and sealing a portion to become a container bottom of a square tubular container blank into a flat shape, and includes: a tubular mandrel main body having four contacting parts along which four corners of the container blank lie; a bottom plate for closing a basal end of the mandrel main body; and a top plate for closing a distal end of the mandrel main body, wherein the mandrel main body is made of a thin thickness pipe molded article, and a part between adjacent contacting parts is formed to have a traverse plane of a concave shape.
The four corners do not only refer to the corners of the container blank in a narrow sense, and also includes two orthogonal planes in the vicinity of the four corners of the container blank. The four contacting parts not only refer to the part contacting the corner of the container blank in a narrow sense, and also includes the part contacting the two orthogonal planes at least in the vicinity of the four corners.
The thin thickness molded article is not limited to that obtained by roll molding the thin thickness pipe material having a circular traverse plane, and may be that obtained by roll molding the thin thickness pipe material having a rectangular traverse plane, or that obtained by bending and molding a thin thickness plate to a pipe shape and welding the seam.
The thickness pressure of the thin thickness pipe molded article is, in view of strength and lighter weight, between 0.8 mm and 3.0 mm, but is preferably between 1 mm to 2 mm for enhancing the molding stability.
In the container bottom molding mandrel according to the present invention, the mandrel main body is lighter since it is made of a pipe molded article.
Further, if the part between the adjacent contacting parts is formed into a part having a concave traverse plane, the buckling strength of the mandrel main body is ensured regardless of the lighter weight of the mandrel main body.
Further, when a cooling water inlet and a cooling water outlet are formed in the bottom plate, a concave part is formed at a back surface of the top plate, an opening of the concave part is covered by a closing plate so as to form a cooling chamber in the concave part, an inlet side communication port and an outlet side communication port are formed in the closing plate, the cooling water inlet and the inlet side communication port are communicated by a cooling water pipe traveling down through a hollow interior of the mandrel main body, and the cooling water outlet and the outlet side communication port are communicated by the hollow interior of the mandrel main body, the cooling water may flow into the cooling chamber through the inlet side communication port by the cooling water pipe, and the cooling water that flows out from the cooling chamber through the outlet side communication port may fill the hollow interior of the mandrel main body. Therefore, the temperature of the outer surface of the entire mandrel main body is uniformly maintained.
Further, when the mandrel main body, the bottom plate, and the top plate are made of metal of the same material, and are integrated through welding, the gap between the corresponding parts is eliminated. Accordingly, it is possible to prevent contamination in the gap adjacent to the inner surface of the container blank.
A method of manufacturing the container bottom molding mandrel according to the present invention includes the steps of: molding a mandrel main body by roll molding a pipe material of a circular traverse plane made of steel having a uniform thickness; forming the bottom plate by welding a stainless steel plate material to the basal end of the mandrel main body; and forming the top plate by welding a stainless steel plate material to the distal end of the mandrel main body.
According to the method of manufacturing the container bottom molding mandrel according to the present invention, the measures for wear resistance and corrosion resistance associated with aluminum are not necessary since the mandrel main body, the bottom plate, and the top plate are all made of stainless steel.
Further, since the mandrel main body is molded by roll molding a pipe material of a circular traverse plane having a uniform thickness, lighter weight is more easily achieved.
Moreover, the hygienic problem is avoided since the mandrel main body, the bottom plate, and the top plate are integrated by welding the bottom plate and the top plate to the mandrel main body.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a longitudinal cross sectional view of a mandrel according to the present invention.
Fig. 2 is a transverse cross sectional view taken along line II-II of Fig. 1.
Fig. 3 is an exploded perspective view of the mandrel.
Fig. 4 is an explanatory view showing a molding state of the mandrel.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiment of the present invention will now be described with reference to the drawings.
In Fig. 1, only one mandrel 12 attached to a rotating body 11 is shown, but normally, a plurality of mandrels 12 are radially attached about a rotating axis of the rotating body 11 in use. A square tubular container blank B is fitted to the mandrel 12, but the distal end portion that is to become the container bottom of the container blank B is already folded and sealed to a flat shape. The container blank B is made of a mainly paper stacked body having a thermoplastic resin layer on both surfaces.
The rotating body 11 is intermittently rotatably driven so that the mandrel 12 is sequentially stopped at a supply station, a heating station, a folding station and a sealing station. At the supply station, the square tubular container blank B is fitted to the mandrel 12 so that the portion that is to become the container bottom projects out from the mandrel 12. At the heating station, the projecting portion of the blank B is heated by hot air. At the folding station, the heated portion of the blank B is folded into a flat shape. At the sealing station, the folded portion is pressure sealed.
A circular bottomed attachment hole 21 for attaching the mandrel 12, and a cooling water supply passage 22 and a cooling water discharge passage 23 each communicating to the bottom thereof are respectively opened at the rotating body 11.
The mandrel 12 includes a tubular mandrel main body 31, a bottom plate 32 for closing the basal end of the mandrel main body 31, a top plate 33 for closing the distal end of the mandrel main body 31, and a cooling water pipe 34 that travels longitudinally through the hollow interior of the mandrel main body 31 from the bottom plate 32 to the top plate 33.
The mandrel main body 31 is made of a substantially star shaped stainless steel pipe molded article having a uniform traverse plane across the entire length. Fig. 2 shows the traverse plane of the mandrel main body 31 in detail. The mandrel main body 31 includes four contacting parts 41 having a substantially C-shaped traverse plane that lie along the four corners of the container blank B, and four non-contacting parts 42 having a substantially arch shaped traverse plane formed into a concave shape by having the part between the adjacent contacting parts 41 depressed inward. Each contacting part 41 includes two planar portions 41a contacting in an area to area manner to the two orthogonal planes of the corresponding corner of the container blank B.
The bottom plate 32 is made of a round bar stainless steel plate material that is fitted into the mandrel attachment hole 21. A flange 51 is integrally arranged at the distal end of the bottom plate 32. The flange 51 has a substantially square shape with a peripheral surface greater than the outer surface of the container blank B. A plurality of bolts 52 are passed through the flange 51 and screw fitted to the periphery of the attachment hole 21 of the rotating body 11.
An annular groove 53 is formed at the outer peripheral surface of the bottom plate 32, and an O-ring 54 is fitted thereto. Further, a packing 55 is interposed between the bottom surface of the attachment hole 21 and the end face of the bottom plate 32. A feeding side communication hole 56 and a returning side communication hole 57 are formed in the packing 55 so as to coincide with the opening ends of the cooling water supply passage 22 and the cooling water discharge passage 23, respectively. The cooling water inlet 58 is formed so as to communicate with the feeding side communication hole 56, and the cooling water outlet 59 is formed so as to communicate with the returning side communication hole 57 at the bottom plate 32.
The top plate 33 is made of a substantially square stainless steel plate material having a peripheral surface that substantially matches the entire periphery of the inner surface of the container blank B. A V-shaped groove 61 extending in the transverse direction through the central part is formed at the surface of the top plate 33. The V-shaped groove 61 is provided for molding the container bottom, and at the same time, to provide a V-shaped recess for stabilizing container bottom in the container bottom.
A circular concave part 62 is formed at the central part of the back surface of the top plate 33. The concave part 62 includes an inner small diameter portion 63 and an outer large diameter portion 64 continuing by way of a step. A closing plate 65 is fitted to the large diameter portion 64, so that the small diameter portion 63 forms the cooling chamber 66. An inlet side communication port 67 and an outlet side communication port 68 are formed in the closing plate 65.
The inlet end of the cooling water pipe 34 is inserted into the cooling water inlet 58, and the outlet end of the cooling water pipe 34 is inserted into the inlet side communication port 67.
The cooling water supplied to the cooling water pipe 34 through the cooling water supply passage 22 flows into the cooling chamber 66. The periphery of the cooling chamber 66 is efficiently cooled by the cooling water that flows in. The cooling water in the cooling chamber 66 flows out to the hollow interior of the mandrel 12 through the outlet side communication port 68, and the cooling water that flows out fill the hollow interior of the mandrel 12. Therefore, the entire mandrel main body 31 is evenly cooled. The cooling water that has completed its task is discharged from inside the mandrel main body 31 through the cooling water outlet 59.
The mandrel main body 31 is ultimately molded to a pipe material P3 having a substantially star shaped traverse plane from the pipe material P1 having a circular traverse plane made of stainless steel through an intermediate pipe material P2 having a square traverse plane by roll molding using a plurality of types of squeeze rollers R1 to R5. The pipe material P3 having a substantially star shaped traverse plane is cut to a predetermined length to form the mandrel main body 31. The stainless plate material that is to become the bottom plate 32 and the top plate 33 are joined to the respective ends of the mandrel main body 31 through welding.

INDUSTRIAL APPLICABILITY

The container bottom molding mandrel and the method of manufacturing the same according to the present invention are suitable when used in folding and sealing the portion that is to become the container bottom of a square tubular container blank into a flat shape in packaging machines for manufacturing a gable top container filled with drink.

Claims

A container bottom molding mandrel fitted with a container blank when folding and sealing a portion to become a container bottom of a square tubular container blank into a flat shape, the container bottom molding mandrel comprising:
a tubular mandrel main body having four contacting parts along which four corners of the container blank lie;

a bottom plate for closing a basal end of the mandrel main body; and

a top plate for closing a distal end of the mandrel main body, wherein

the mandrel main body is made of a thin thickness pipe molded article, and

a part between adjacent contacting parts is formed to have a traverse plane of a concave shape.
The container bottom molding mandrel according to claim 1, wherein
a cooling water inlet and a cooling water outlet are formed in the bottom plate,
a concave part is formed at a back surface of the top plate,
an opening of the concave part is covered by a closing plate so as to form a cooling chamber in the concave part,
an inlet side communication port and an outlet side communication port are formed in the closing plate,
the cooling water inlet and the inlet side communication port are communicated by a cooling water pipe traveling down through a hollow interior of the mandrel main body, and
the cooling water outlet and the outlet side communication port are communicated by the hollow interior of the mandrel main body.
The container bottom molding mandrel according to claim 1 or 2, wherein
the mandrel main body, the bottom plate, and the top plate are made of metal of the same material, and are integrated through welding.
A method of manufacturing a container bottom molding mandrel according to any one of claims 1 to 3, comprising the steps of:
molding a mandrel main body by roll molding a pipe material of a circular traverse plane made of steel having a uniform thickness;

forming the bottom plate by welding a stainless steel plate material to the basal end of the mandrel main body; and

forming the top plate by welding a stainless steel plate material to the distal end of the mandrel main body.