Cylindrical paper drum and method of fabricating the same

Abstract: A cylindrical body of a fiber drum comprises a roll (2) of a paper material having two opening ends, a curled portion (5) formed by curling the edge of at least one of said two opening ends and a protective material (3) for covering outer surface of the curled portion (5). A method of fabricating a cylindrical body of a fiber drum comprises the steps of winding a length of paper sheet in layers, between which an adhesive is applied, to form a roll (2) of the paper sheet having two opening ends, providing a protective material (3) on an opening edge at either of the two opening ends of the roll (2), and curling inwardly or outwardly the opening edge at said either of the two opening ends of the roll (2) together with the protective material (3) before the adhesive is cured between the layers to form a curled portion (5) covered at an outer surface with the protective material (3).

Description: The present invention relates to a cylindrical body of a paper material consisting a fibre drum and a method of fabricating the cylindrical body. A conventional cylindrical body of a fiber drum is made of a roll of a paper material and its opening edges at both upper and lower ends of the roll are inwardly curled together with metal rings for reinforcement thus forming inwardly curled annular portions. Such am arrangement is disclosed in United Kingdom Patent specification GB 2266490, upon which the preamble of claim 1 is based, in which a fiber drum is attached to top and bottom circular closure elements through the agency at each end of ring crimped over a flange at each opening to form the closure. However, the conventional cylindrical body consumes a considerable length of time for crushing and separating the inwardly curled portions into the metal rings and the paper material for disposal of the drum and will thus be unfavourable for recycling. For solving the above drawback, the applicants of the present invention has proposed a cyclindrical body which has the opening edges at both upper and lower ends of a roll of a cylindrical shape thereof reinforced with ring portions which are curled or outwardly (Japanese Patent Laid-open Publication No. 2001-31055). When the opening edges at both upper and lower ends of its roll made of a cylindrical paper material are curled inwardly or outwardly, the cylindrical body may develop an excessive stress on the ring portions. More specifically, if the edges are inwardly curled, they may generate wrinkles andbecome injuredat the curling. If the edges are outwardly curled, they may produce radial cracks at the curling. As a result, the opening edges of the roll may hardly be guaranteed in the physical strength and their injury and cracks will create paper dust. When the fiber drum is used for storage of powder or granules of medical product or fine chemical, it may be provided with an inner bag or container made of a synthetic resin material for being air-tightly filled with the powder or granules. Yet, if the inner bag or container is fouled with dusts of the paper material of the cylindrical body, it may appear as having suffered from leakage or contamination with the paper dusts and its quality management will hardly be qualified. Accordingly, it is a major issue to inhibit the generation of paper dusts. SUMMARY OF THE INVENTION The present invention is developed in view of the above aspects and its object is to provide a cylindrical body of a fiber drum which can prevent the generation of paper dusts while the opening edges of a roll thereof are being shaped, improve the physical strength of the opening edges, and facilitate its recycling and a method of fabricating the cylindrical body. For achievement of the object, the present invention provides a cylindrical body of a fiber drum comprising: a roll of a paper material having two opening ends; a curled portion formed by curling the edge of at least one of said two opening ends; and a protective material for covering outer surface of the curled portion; characterised in that the protective material is a length of paper tape. This will increase the physical strength of the or each said edge. Also, if the curled end of the curled portion is injured or cracked, its outer surface is protected with the protective material thus inhibiting paper dusts generated at the injury or cracks from dispensing to the outside. The protective material may preferably be a length of paper tape. This will require no particular separation of the protective material from the roll during the disposal process. The invention also provides a method of fabricating the cylindrical body of a fiber drum of a fiber drum comprising the steps of winding a length of paper sheet in layers, between which an adhesive is applied, to form a roll of the paper sheet having two opening ends, providing a protective paper tape material on an opening edge at either of the two opening ends of the roll, and curling inwardly or outwardly the opening edge at said either of the two opening ends of the roll together with the protective material before the adhesive is cured between the layers to form a curled portion covered at an outer surface with the protective paper tape material. As the curled portion is formed within a short period of time, a number of the cylindrical bodies can be fabricated at higher efficiency. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a cylindrical body showing one embodiment of the present invention; Fig. 2 is a cross sectional view of one side of the cylindrical body according to the embodiment of the present invention; Fig. 3 is a partially enlarged cross sectional view of the cylindrical body according to the embodiment of the present invention; Fig. 4 is an explanatory view showing a process of forming a green roll of the cylindrical body; Fig. 5 is a cross sectional view of one side of the cylindrical body where its roll is protected with a protective tape material; Fig. 6 is a front view of a forming machine; Fig. 7 is a cross sectional front view showing the roll placed in the forming machine; Fig. 8 is an enlarged cross sectional view of a primary part of the roll with a curled portion provided at one opening edge thereof; Fig. 9 is a cross sectional front view showing an action of the curled portion being outwardly expanded by a forming die; Fig. 10 is a cross sectional front view showing the curled portion fractured with a chuck; Fig. 11 is a partially enlarged cross sectional view of a cylindrical body showing another embodiment of the present invention; Fig. 12 is a perspective view of the cylindrical body of the another embodiment of the present invention; Fig. 13 is a cross section view of one side of the cylindrical body of the another embodiment where its body is protected with a protective tape; Fig. 14 is partially enlarged cross sectional view of the cylindrical body of the another embodiment of the present invention; and Fig. 15 is partially enlarged cross sectional view of the cylindrical body of the another embodiment of the present invention. DETAILED DEACRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described in more detail. Fig. 1 is an external view of a cylindrical body of a fiber drum showing one embodiment of the present invention and Fig. 2 is a front view showing the cross section of one side of the cylindrical body. Fig. 3 is a partially enlarged cross sectional view of the cylindrical body. As shown, the cylindrical body 1 of the fiber drum comprises a roll 2 made of a paper material and a protective tape 3 of a paper material provided as a protective member. The roll 2 may be fabricated by rolling a thick paper board into a cylindrical form or a plurality of paper sheets into a multi-layer form which will be explained later in more detail. The protective tape 3 may be a length of craft tape having an adhesive coating provided on the back side thereof . As shown in Figs. 1 to 3, one edge at one opening 4 of the roll 2 is inwardly curled to form a curled portion 5 of an annular form which extends circumferentially and has an oval shape in the cross section. The protective tape 3 is bonded to the circumference of the curled portion 5. The curled portion 5 is pressed down together with the protective tape 3 so that its inner cavity is eliminated. Similarly, the edge at the other opening end 6 of the roll 2 is curled to have a curled portion 7 which is identical in the shape to the curled portion 5 provided at the edge of the opening end 4. The curled portion 7 like the curled portion 5 is protected with another protective tape 3 and pressed down by the same manner. As both the roll 2 and the protective tape 3 of the cylindrical body 1 are made of paper materials, they need not separation during the disposal process of the cylindrical body 1 but can easily be recycled for reuse. The two curled portions 5 and 7 are protected with the corresponding protective tapes 3 and even if they are wrinkled and inj ured when being curled and thus produce paper dusts, the protective tapes 3 can inhibit the paper dusts from being scattered out to the outside. Also, the curled portions 5 and 7 are pressed down so that their inner cavities are eliminated and their physical strength will be increased. The protective tapes 3 of the embodiment are made of, but not limited to, the craft tape having the adhesive layer provided on the back side thereof. For example, the protective tapes 3 may be made of a synthetic resin material such as poly-propylene tape or cellophane tape. Those materials of the tape can equally inhibit paper dust generated at the reinforcement of the opening end or any crack of the edge from being scattered out. A method of fabricating the cylindrical body 1 will now be described. The method starts with a step of forming a green cylindrical body 1a as shown in Fig. 4. More specifically, a length of paper sheet S coated at its upper side with an adhesive Q before curing is wound in seven to eight layers on the mandrel of a drum forming machine (not shown) to form a roll 2 of the green cylindrical body 1a. The adhesive Q may be any commercially available hydrophilic adhesive composed mainly of e.g. poly-vinyl acetate emulsion or poly-vinyl alcohol. Then, a protective tape (a protective member) 3 of a paper material which has an adhesive coating provided on the back side thereof and a synthetic resin coating provided on the front side thereof is circumferentially applied to the outer surface of each of edges 81 and 82 at both opening ends of the green cylindrical body 1a, hence completing the roll 2. The width of the protective tapes 3 is so sized as to cover completely the curled ends 5a and 7a of their respective curled portions 5 and 7 (See Figs. 2 and 3). The protective tapes 3 may be applied as slightly spaced from the opening edges 81 and 82 so long as covering completely the curled ends 5a and 7a of the curled portions 5 and 7. The roll 2 is then transferred to a curled portion forming step which may be carried out by a forming machine M shown in Fig. 6. The forming machine M performs a sequence of three steps, (1) the first step of inwardly curling both edges 81 and 82 of the roll 2, (2) the second step of increasing the cross section of each inwardly curled portion radially and outwardly, and (3) the third step of pressing down the inwardly curled portions. The forming machine M has a forming die 9 of substantially a circular shape in the plan view placed on a platform 10 supported by the floor bed and fixedly held at an intermediate of its outer side with an annular chuck support 11. A first chuck 12a and a second chuck 12b which travel forward and backward on the horizontal are provided on the upper side of the chuck support 11. The first chuck 12a located upper has a guide region 13 provided on the inner wall thereof for inwardly curling the edge of the roll with its guiding surface 131. The inner wall of the second chuck 12b located lower is a taper surface 14 which is tilted to increase the opening towards the lower end and opposite to a taper surface 14 of the outer side of the forming die 9 tilted at the same angle. A vertically movable pressing member 16 is provided precisely above the forming die 9 for pressing down the roll 2 against the forming die 9. In action, the roll 2 of the layers of the paper sheet S before the adhesive Q is cured is loaded and placed upright on the guide region 13 of the first chuck 12a as shown in Fig. 7. While Fig. 7 illustrates the edge at the other opening 6 for simplicity of the description, the edge at the one opening 4 of the roll 2 can also be shaped after turned up side down. When the pressing member 16 is lifted down, the opening edge 81 moves along and on the guiding surface 131 as shown in Fig. 8. As the protective tape 3 slides directly along the guiding surface 131 of the guide region 13 and the taper surface 14 of the first chuck 12a extending continuously from the guide region 13, the edge 81 is inwardly curled to form the curled portions 5 and 7. When pressed down, the inner layers of the paper sheet S of the roll 2 lag behind the outer layers due to a difference in the curvature radius at the curled portion 5 or 7. The layers of the paper sheet S when curled are not separated but remain bonded to each other by the action of the adhesive Q. Also, the adhesive serves as a lubricant to assist the lagging. Simultaneously, as the layers of the paper sheet S are curled, portions of the adhesive Q between the layers of the edge 81 of the roll 2 are squeezed out hence running over the inner side of the roll 2. As a result, the portions of the adhesive Q may contribute to the higher adhesivity and when cured, the improved rigidity of the curled portions 5 and 7. By the above manner, the curled portions 5 and 7 of the roll 2 are formed at the one opening 4 and the other opening 6 respectively. As known, the curled portions 5 and 7 are instantly formed in a sequence. Then, as the adhesive Q is cured between the layers of the paper sheet thus to turn to an adhesive Qa, the curled portions 5 and 7 are increased in the rigidity. This is followed by retracting the first chuck 12a from the curled portion 7 and lifting down the pressing member 16 further as shown in Fig. 9. As moved along the taper surface 15 of the outer side of the forming die 9, the curled portion 7 is turned outwardly. If the tilting angle is too large, the curled portion 7 may have flaws extending radially. It is hence essential to determine an appropriate angle of the tilting for eliminating the generation of flaws. As shown in Fig. 10, the tilted curled portion 7 is held directly with the taper surface 15 of the forming die 9 and then the second chuck 12b is advanced in the direction X denoted by the arrow in Fig. 10 to press down the curled portion 7. Any hollow space in the curled portion 7 may decline the physical strength at the opening of the roll 2. The pressing down of the curled portion 7 may require a pressing force to prevent formation of any hollow space. As described above, the curled portions 5 and 7 are covered with the protective tapes 3. Accordingly, the curled portions 5 and 7 are not only reinforced in rigidity but also can be prevented from its paper dusts at any crack being scattered out. Also, as the protective tapes 3 are applied at a fair tension, they can protect the curled portions 5 and 7 from being cracked and when any crack is developed, may minimize its effect. Moreover, as the protective tapes 3 are slippery on the upper side, they allow the edges 81 and 82 to slide directly on the guiding surface 131 and the taper surface 14 of the forming die 9 until the curled portions 5 and 7 are completed. Accordingly, the curled portions 5 and 7 are less susceptible to the cracking or injury. It is a good idea that when the adhesive Q is about cured before the curled portions 5 and 7 are completely shaped, the body is heated up for softening the adhesive Q between the layers of its paper sheet. If the adhesive Q is of a hot melting type, it has to be heated to higher than its melting point. While the curled portions 5 and 7 of the embodiment are fabricated, but not limited to, by inwardly curling the two edges 81 and 82 at both opening ends 4 and 6 of the roll 2, they may be shaped by any other manner. For example, as shown in Fig. 11, each edge 81 (82) of the roll 2 may inwardly be folded down to form a curled portion 51 (71). As the folded ends 5a and 7a of their respective curled portions are equally protected with protective tapes, their physical strength at the opening will be enhanced. The protective tapes 3 may be applied circumferentially to the inner sides of the opening edges 81 and 82 at both ends of a green cylindrical body 1a to form a roll 2 as shown in Fig. 13. Then, each opening edge 81 (82) at one opening 4 or other opening 6 of the roll 2 is outwardly curled to form a curled portion 52 (72), as shown in Figs. 12 to 14. Alternatively, each opening edge 81 (82) of the roll 2 may outwardly be folded down to have a curled portion 53 (73) as shown in Fig. 15. In any case, the generation of paper dusts can be inhibited while the physical strength of the edge at each opening is improved. The above embodiments of the present invention are not limited to the opening edges 81 and 82 provided with their respective curled or folded portions 5 (51, 52, or 53) and 7 (71, 72, or 73) but may permit one of the two opening edges 81 and 82 to be accompanied with the curled or folded portion.

Claims: A cylindrical body of a fiber drum (1) comprising: a roll (2) of a paper material having two opening ends (4,6); a curled portion (5) formed by curling the edge of at least one of said two opening ends; and a protective material (3) for covering outer surface of the curled portion; characterised in that the protective material (3) is a length of paper tape. A method of fabricating a cylindrical body of a fiber drum (1) comprising the steps of winding a length of paper sheet (S) in layers, between which an adhesive (Q) is applied, to form a roll (2) of the paper sheet having two opening ends (4,6), providing a protective paper tape material (3) on an opening edge at either of the two opening ends of the roll, and curling inwardly or outwardly the opening edge at said either of the two opening ends of the roll together with the protective material before the adhesive is cured between the layers to form a curled portion (5a, 7a) covered at an outer surface with the protective paper tape material.

Inventors: KASUYA MOTOHARU, KASUYA, MOTOHARU
Applicants: TAIYO SEALPACK CO LTD, TAIYO SEALPACK CO. LTD.
Application year: 2001
Main classification: B31F1
IPC codes: B65D3, B31F1, B31C1