DE69511489T2 - Insulated cup and process for its manufacture - Google Patents

Description

The present invention relates to a method for manufacturing a heat-insulated cup according to the preamble of claim 1. Furthermore, the invention relates to a heat-insulated cup according to the preamble of claim 13.

A generic heat-insulated cup is known from the publication EP-0 458 081 A3. This heat-insulated cup has a cup body and a paper protective cover which is attached to cover a side wall of the cup body. The paper protective cover consists of an embossed sheet into which embossed dots are pressed.

A known heat-insulated cup comprises a paper cup body and a paper protective cover having a heat-insulating structure surrounding the cup body. The cup of this type can be easily disposed of when it is no longer needed. In addition, the cup materials can be reused when necessary.

A cup having a cup body and a corrugated cardboard attached to the cup body so as to surround the cup body is disclosed, for example, in JP-U-50-27 080, wherein the corrugated cardboard comprises two cover boards, i.e., thicker sheets, and a corrugated paper sheet sandwiched between these cover boards. In this prior art, it is necessary to form the two hard cover boards into truncated cone shapes differing from each other in circumferential length so that the corrugated cardboard can be smoothly wound or wrapped around to conform to the shape of the cup body. The requirement for special shapes results in a difficult process in producing the cover boards. In addition, the corrugated cardboard tends to elastically separate from the cup body. If an external force exceeding an elastic limit is applied to the corrugated cardboard, the liners of the corrugated cardboard will curl, so that the external appearance of the cup will deteriorate.

A technique for overcoming the above-mentioned problems is disclosed, for example, in JP-A-54-1178. It is disclosed that a large number of cuts are made on the outer cover board of the corrugated board to facilitate the wrapping of the corrugated board into a cylindrical shape. However, the cylindrical body thus formed has poor heat insulating ability. In addition, the external appearance of the cylindrical body is not satisfactory.

The object of the present invention is to provide a heat-insulated cup which is suitable for mass production at low cost.

In addition, a heat-insulated cup is created that has a suitable external appearance.

In addition, a heat-insulated cup is created in which a protective cover is firmly attached to the cup body.

In addition, a heat-insulated cup is created that exhibits a low tactile temperature when the cup filled with hot contents is held by a person.

In addition, a heat-insulated cup is created, the surface of which effectively prevents a user's fingers from slipping when the cup is held by a person.

Finally, a heat-insulated cup is created that can be easily removed from a multitude of cups arranged telescopically one above the other.

The above-mentioned object is solved by means of the features defined in the characterizing part of claim 1. Preferred embodiments of the method for producing a heat-insulated cup according to claim 1 are set out in the dependent claims 2 to 12, respectively. The above-mentioned object is also solved by means of the features defined in the characterizing part of claim 13. Preferred embodiments of the heat-insulated cup according to claim 13 are defined in the dependent claims 14 to 30, respectively.

This invention will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings.

Fig. 1 shows a perspective partially broken away view of a heat insulated cup according to an embodiment of the present invention together with a lid shown in a position removed from the cup.

Fig. 2 shows a partially broken front view of the heat-insulated cup shown in Fig. 1.

Fig. 3 shows a cross-sectional view of the side wall of the cup body included in the heat-insulated cup shown in Fig. 1.

Fig. 4 shows a cross-sectional view of the cover board used in the heat-insulated cup shown in Fig. 1.

Fig. 5 shows a flow chart of the process for manufacturing the heat-insulated cup shown in Fig. 1.

Fig. 6 is a plan view showing how an adhesive is applied to a blank of a protective cover.

Fig. 7 shows a plan view of a modification of the blank of a protective sheet and also shows how an adhesive is applied to this blank.

Fig. 8 shows a plan view of a modified manner of applying an adhesive to a blank of a protective sheet.

Fig. 9 shows a plan view of a modification of a blank of a protective sheet.

Fig. 10 shows a plan view of another variation of a blank of a protective sheet.

Fig. 11 is a cross-sectional view of a modification of a flange portion of the heat-insulating cup shown in Fig. 1.

Figs. 12A to 12D collectively show a process for forming the flange portion shown in Fig. 11.

Fig. 13 shows a plan view of a modification of a cover board.

Fig. 14 shows a cross-sectional view of a modification of the side wall of the cup body.

Fig. 15 shows a process for producing a raw material sheet used for forming the side wall shown in Fig. 14.

Fig. 16 is a partially broken front view of a heat-insulating cup according to another embodiment of the present invention.

17A and 17B show a cross-sectional view taken along a line XVII-XVII shown in Fig. 16 and a cross-sectional view of a modification of the heat-insulating cup shown in Fig. 16, respectively.

Fig. 18 shows a process for manufacturing the heat-insulated cup shown in Fig. 16.

Fig. 19 shows a perspective partially broken away view of a heat-insulated cup according to another embodiment of the present invention together with a lid shown in a position removed from the cup.

Fig. 20 shows a perspective partially broken view of a modification of the heat-insulated cup shown in Fig. 19.

Fig. 21 shows a perspective view, partially broken away, of another modification of the heat-insulating cup shown in Fig. 19.

Fig. 1 shows a perspective partially broken view of a heat-insulated cup 10 according to an embodiment of the present invention, and Fig. 2 shows a partially broken front view of the heat-insulated cup 10 shown in Fig. 1. A lid 11 of the cup 10 is shown in a manner removed from the cup 10.

The cup 10 comprises a cup body 12 having a paper side wall 14 formed in an inverted truncated cone shape and a bottom wall 16. The side wall 14 is made by wrapping a paperboard into a truncated cone shape in such a way as to allow the side end portions 15 of the wrapped paperboard to overlap each other, followed by adhering the covered end portions 15 of the wrapped paperboard cardboard boxes. On the other hand, the bottom wall 16 has a short cylindrical foot portion which is engaged with the lower end portion of the side wall 14. Further, the lower end portion of the side wall 14 is folded inward so that the foot portion of the bottom wall 16 is wrapped therein. As a result, the lower end portion of the resulting cup body is sealed.

The peripheral upper open end portion of the side wall 14 is folded outward such that the folded portion makes at least one complete turn to form a flange portion 18 for reinforcing the cup body 12. The sheet-like lid 11 is attached to the flange portion 18. The lid 11 is made of paper or a laminate structure comprising a paper sheet, such as a laminate structure consisting of a paper sheet and an aluminum foil adhered to the paper sheet. An adhesive layer is formed on the lower surface of the lid 11. After filling contents into the cup body 12, the lid 11 is attached to the flange portion 18 of the side wall 14. It is possible to mount a cover 11A made of a blank of a transparent resin to the flange portion 18 as shown in Fig. 19, instead of using the sheet-like cover 11.

The heat-insulated cup 10 also includes a protective cover 20 covering substantially the entire area of the outer surface of the side wall 14 of the cup body 12. The protective cover 20 is made of a multi-layer structure including an embossed paper sheet 24 attached to cover the entire outer surface of the side wall 14 and a paperboard cover board 28 attached to cover the entire area of the embossed paper sheet 24.

Both the side wall 14 and the bottom wall 16 of the cup body 12 are made of a white high quality cardboard with a basic weight of approximately 210 g/m² and a thickness of about 280 µm. As shown in Fig. 3, a polyethylene film 13 having a thickness of about 45 µm is formed by being laminated on the inner surface of the paperboard used for forming the side wall 14 of the cup body 12. Such a polyethylene film is also formed on the inner surface of the paperboard used for forming the bottom wall 16. Desirably, a paperboard for forming the side wall 14 having a basis weight within a range between 170 g/m² and 310 g/m² and a thickness within a range between 220 µm and 420 µm is used. On the other hand, the thickness of the polyethylene film 13 should desirably be within a range between 20 µm to 60 µm.

The embossed paper sheet 24 is made of white bleached kraft paper and has a basis weight of 120 g/m². The embossing 25 consists of a large number of embossed spots and is formed in the entire area of the embossed paper sheet 24. These embossed spots of the embossing 25 are arranged so that first rows extending in a direction at an angle of approximately 45° to the axis of the cup body 12 and second rows crossing the first rows substantially at a right angle are formed. It is required that the embossing 25 is not compressed by normal use of the cup 10. In addition, it is required that the embossed paper sheet 24 is easy to process. To meet these requirements, the embossed paper sheet 24 desirably has a basis weight within a range between 50 g/m² and 180 g/m². It should be noted that bleached kraft paper is made of long fibers and thus is unlikely to break when an embossing treatment is applied to it. More specifically, the embossed portions of the embossing 25 consist of circular projections and circular depressions each having a diameter of about 3.5 mm and arranged alternately at an equal distance. All of the projections and all of the depressions are arranged to form grids which extend in directions which are at an angle of approximately 45 degrees with respect to the axis of the cup body 12 and complementarily overlap each other. The density of the embossed locations of the embossing 25, which includes both the projections and the depressions, is 7/cm². The height of the embossing 25, that is, the vertical distance between the top of the projection and the bottom of the depression, which is uniform over the entire area of the embossed paper sheet 24, is set to approximately 2 mm.

The thermally insulated air layer formed within the protective cover 20 is essentially defined by the shape and size of the embossing 25. In view of the desired thermal insulation properties of the cup 10, the diameter of the projections and depressions forming the embossed points of the embossing 25 should be in the range between 2 mm and 5 mm. The height of the embossing 25 should be in the range between 1 mm and 5 mm as desired. The density of the embossed points of the embossing 25 should be in the range between 3/cm² and 25/cm² as desired. In the embodiment shown in Fig. 2, the embossing 25 consists of circular projections, that is to say projections each with a circular cross section, and circular depressions. In addition, it is possible that the embossing 25 consists of rectangular projections and rectangular recesses whose size is substantially equal to the circular projections and circular recesses described above. Furthermore, a wave pattern may be used instead of the projections and recesses formed in the embossed paper sheet 24.

The paperboard liner 28 has a basis weight of 230 g/m³. Letters or patterns indicating a trade name or the like are applied to the front surface of the liner 28 by means of offset printing or gravure printing. If desired, the liner 28 has a basis weight within a range between 180 g/m² and 270 g/m². If the basis weight exceeds the upper limit of 270 g/m², the cover board 28 becomes excessively rigid, and handling of the cover board for manufacturing the protective cover 20 becomes difficult. On the other hand, if the basis weight is less than the lower limit of 180 g/m², the rigidity and mechanical strength of the cover board 28 decrease. As a result, projections and depressions corresponding to the embossing 25 are formed on the surface of the cover board. Furthermore, the protective cover 20 mounted on the cup body 12 is likely to break during transportation or storage of the heat-insulated cup 10. As shown in Fig. 4, ink layers 29 for representing letters or patterns are formed on the cover board 28. Further, a varnish layer 30 having a thickness between 3 µm and 15 µm is formed to cover the entire surface of the cover board 28. The surface of the lacquer layer 30, which is made of, for example, an OP lacquer (overprint lacquer), a peel-off lacquer and the like, is smoothly finished.

The cup body 12, the embossed paper sheet 24 and the liner board 28 are adhered to each other with synthetic adhesives including, for example, a vinyl acetate type adhesive and an ethylene vinyl acetate (EVA) type adhesive. It is possible to use various other known adhesives such as a starch type adhesive. However, in the case of using a starch type adhesive, projections and recesses corresponding to the embossing 25 are likely to be formed on the surface of the liner board 28. If this is the case, the use of the vinyl acetate type adhesive and the ethylene vinyl acetate (EVA) type adhesive for adhering the liner board 28 to the embossed paper sheet 24 is particularly desirable.

Fig. 5 shows a process for manufacturing the heat-insulated cup shown in Figs. 1 and 2. A known cup manufacturing apparatus is used to manufacture the cup body 12. In the first step, a sector blade 102 is wound into a truncated cone shape to form the side wall 14. On the other hand, a circular sheet 104 is wound along its circumference to form the bottom wall 16. This side wall 14 and this bottom wall 16 are assembled so that a main shape 106 of the cup body 12 is formed, followed by outward folding or curving of the upper open end portion of the cup body 12 to form the flange portion 18. Thereafter, an annular embossed line or mark 19 is formed along the outer peripheral surface of the side wall 14. The annular embossed line 19 is used as a mark when a liquid such as hot water is poured into the cup.

On the other hand, the protective cover 20 is manufactured by a system comprising a known roll embossing machine, a known combining machine and a known die cutting machine. More specifically, a sheet roll 108 of a white bleached kraft paper used as a base paper for the embossed paper sheet 24 and a sheet roll 112 of the liner board 28 are set in the system. Intaglio printing and varnish coating are previously applied to the surface of the raw material sheet of the liner board 28 using a printer 114 and the like. By this printing, letters and patterns indicating the trade name and the like are applied to the surface of the raw material sheet of the liner board 28.

The bleached kraft paper sheet taken out from the sheet roll 108 is embossed by an embossing roller 116 to prepare a raw material sheet of the embossed paper sheet. Thereafter, an adhesive such as a vinyl acetate type adhesive is applied to a surface of the raw material sheet by an application roller 118. In the embodiment shown in Fig. 5, the adhesive application is carried out after the embossing treatment. However, it is possible to carry out the adhesive application simultaneously with the embossing treatment.

A sheet is removed from the sheet roll 112 for the cover board 28 simultaneously with the removal of the bleached kraft paper so that the removed cover board 28 is superimposed on the adhesive-applied surface of the raw material sheet of the embossed paper sheet 24. In this state, the raw material sheet of the cover board 28 is adhered to the raw material sheet of the embossed paper sheet 24 by a pair of spacer rollers 122 and a pressing belt 124. A predetermined distance is provided between the paired rollers 122. In addition, a spring force is applied to one of these rollers so that one roller is elastically movable toward the other roller. Due to this special structure, the cover board and the embossed paper sheet can be stapled together without the embossing 25 formed on the surface of the embossed paper sheet being compressed.

The raw material sheets of the embossed paper sheet 24 and the cover board 28, which are stapled together, are separated by a separator 126 into spacers 128 each having a predetermined width. Thereafter, these spacers 128 are successively punched in accordance with the letters or patterns printed on the cover board 28, so that a sector blank 32 of the protective cover 22 is obtained, the blank 32 having a size that matches the size of the peripheral side surface of the cup body 12. In the manufacturing process shown in Fig. 5, it is possible to omit the step of forming the spacer 128, so that the sector blank 32 of the protective cover 22 can be directly manufactured by punching.

An adhesive agent such as an ethylene vinyl acetate type adhesive agent is then applied to the blank 32 by an application roller 132. Further, the blank 32 provided with the adhesive agent is attached to the side wall 14 of the cup body 12 so that the heat-insulated cup 10 is formed which comprises the cup body 10 and the protective cover 20. The blank 32 provided with the adhesive agent Blank 32 may be attached to side wall 14 using a wrapping device. In this case, blank 32 is adhered by the adhesive on side wall 14 during the process of wrapping blank 32 around side wall 14 of cup body 12. The wrapping process allows the side end portions of blank 32 not to overlap but to abut each other when blank 32 is adhered to side wall 14.

A fitting method may be used instead of the winding method for attaching the blank 32 of the protective cover 20 to the side wall 14 of the cup body 12. In the fitting method, the blank 32 is previously wound into a truncated cone shape substantially conforming to the side wall 14 of the cup body 12, followed by inserting the wound blank 32 along the side wall 14. In this inserting step, the blank is adhered to the side wall 14 of the cup body 12 by an adhesive. The blank 32 of the protective cover 20 is provided with an adhesive application space or an edge portion to which an adhesive is applied at a side end portion as described below, resulting in allowing the side end portions of the protective cover 20 to overlap each other.

An adhesive may be applied to the entire area on the back surface of the blank 32 for attaching the protective cover 20 to the cup body 12. It is also possible to selectively apply the adhesive to band-like side end portions of the blank 32. Furthermore, it is desirable to apply the adhesive to the blank 32 as shown in Fig. 6.

Fig. 6 shows that the blank 32 comprises three band-like first regions 34 on which an adhesive is applied with pressure by an application roller, the first regions 34 consisting of two side end regions 34 near the first and second side ends 33a and 33b and a middle region 34. The blank 32 also comprises two second regions 35 on which an adhesive is applied without pressure by a spray, with the two second regions 35 interposed between the three first regions 34. The protective cover 20 is adhered to the side wall 14 of the cup body 12 by this adhesive. These adhesives applied to the first and second regions 34 and 35 may be the same adhesives, such as an ethylene vinyl acetate adhesive, the difference being in the amount applied.

As described above, to the three first regions 34 of the blank of the protective cover 20 shown in Fig. 6, the adhesive is applied in a pressurized state. In addition, to the two second regions 35, the adhesive is applied in a non-pressurized state and in an amount smaller than the application amount to the first regions 34. As a result, the amount of adhesive consumption can be reduced. In addition, it is possible to prevent various problems such as deformation of the cup body 12, the protective cover 20 and the like and peeling at the side end portion of the protective cover 20 caused by shrinkage of the adhesive when the adhesive dries. Furthermore, heat transfer via the adhesive layer to the outer surface of the protective cover 20 in the region other than the first regions 34 can be reduced, so that the sensible temperature of the heat-insulated cup 10 felt by the user is lowered. It should also be noted that the protective cover 20 is adhered to the cup body 12 by the second portions 35 disposed between the three first portions 34, resulting in the protective cover 20 being prevented from slipping or sliding off. It follows that the present invention enables a solution to various problems such as the feeling that the heat-insulated cup is unreliable when held by the user, the likelihood of occurrence of surface roughness on the protective cover 20, and a tendency for the Protective cover 20 detaches from the cup body 12 when the adhesive has peeled off.

Fig. 5 shows that an adhesive spray device 134 is arranged downstream of the application roller 132. In this embodiment, an adhesive is applied to the three first regions 34 of the blank 32 by the roller 132, followed by spraying an adhesive onto the second regions 35 by the spray device 134. As previously described, these adhesives applied to the first and second regions, which may be the same adhesives such as an ethylene vinyl acetate adhesive, differ from each other in the amount applied. For example, with regard to the adhesive concentration in the application step, the application amount for the first areas 34 should be in the range of between 0.1 g/cm² and 0.5 g/cm², while the application amount for the second areas 35 should be in the range of between 0.005 g/cm² and 0.1 g/cm². It is necessary to set the application amount for the first areas 34 at a certain amount, but it is desirable to make the application amount for the second areas 35 small. If the application amount for the second areas 35 is too large, the protective cover 20 may curl, so that the adhesion between the cup body 12 and the protective cover 20 is deteriorated.

As described above, the applicator roller 132 and the applicator sprayer 134 are used for applying the adhesives to the first and second regions 34 and 35 of the blank 32, respectively, allowing these regions 34 and 35 to be supplied with desired amounts of adhesives that are different from each other. These adhesives for the first and second regions are generally applied to the blank 32 at different steps, but they are applied substantially sequentially, resulting in the throughput for the heat-insulated cup not being significantly reduced.

Fig. 7 shows a blank 32 having an adhesive application space or edge portion 36 which is supplied with an adhesive and covered. In addition, the first and second regions 34 and 35 are arranged in a manner different from that shown in Fig. 6. The first band-like regions 34 are positioned at the side end portions and the second elongated region 35 which is elongated in the lateral direction is positioned substantially in the center of the blank 32. An adhesive is applied to these two first regions 34 by the application roller 132, and an adhesive is applied to the second elongated region 35 by the spray device 134.

Fig. 8 shows another variation of the blank 32. In this case, the blank 32 has five first regions 34 comprising two triangular regions at the side end portions and three band-like regions in the central portion. The blank 32 also has four elongated second regions 35 that are vertically elongated and positioned between adjacent first regions 34. Adhesives are applied to these first and second regions 34 and 35 by the application roller 132 and the spray device 134, respectively.

As is clear from Figs. 7 and 8, it is possible to vary the number, positions and shapes of the first and second regions in various ways, respectively. However, it is necessary that the first regions include band-like regions at the side ends of the blank 32. In addition, it is desirable that the second region be positioned substantially in the middle region sandwiched between adjacent first regions.

As another modification, it is possible to apply an adhesive with pressure to the inner surface of the blank 32 by an application roller and an adhesive without pressure to the outer surface of the side wall 14 by a spray device thereby attaching the protective cover 20 to the side wall 40 with these adhesives. In this case, it is necessary that the first areas to which an adhesive has been applied with pressure by an applicator roller comprise band-like areas at the side ends of the blank 32. The second area to which an adhesive has been applied without pressure by a spraying device may be the entire outer surface of the side wall 14 or a selected portion of the portions thereof. When the second portion consists of a selected portion or portions of the outer surface of the side wall 14, it is desirable that the second portion be selected to correspond to the intermediate position between the first portions, such as the second portions 35 on the blank 32 shown in Figs. 6, 7 and 8.

In this modification, since an adhesive is applied to the side wall 14 of the cup body 12 without pressure by a spray device, the adhesive can be evenly applied to a selected portion on the side wall 14 at a predetermined application amount regardless of the curved surface of the side wall 14.

Fig. 9 shows another modification of the blank 32 of the protective cover 20 which has been previously assembled into a cylinder of a truncated cone shape and is fitted over and adhered to the outer surface of the cup body. In this case, the blank 32 has adhesive coating spaces 36a and 36b at the side end portions. The adhesive coating space 36 has the same shape and function as the adhesive coating space 36 shown in Fig. 7. The adhesive coating space 36b is also coated with an adhesive. In addition, the adhesive coating space 36b allows a side 36c of the blank 32 to abut against a conveying guide in the step of conveying the blank 32, resulting in the blank 32 being held perpendicular to a conveying direction.

Furthermore, the blank 32 shown in Fig. 9 has two straight perforations 37 extending across the width of the blank 32. Moreover, the upper and lower arcs of the blank 32 are concentric. As can be seen from the drawing, each of these two perforations 37 extends toward the center of the two concentric circles that comprise the upper and lower arcs of the blank 32. These two perforations 37 are arranged at substantially the same distance from the center of the blank 32. Each hole of these perforations 37 extends through both the embossed paper sheet 24 and the cover board 28, so that the rigidity of the blank 32 is reduced and alignment is achieved in the step of winding the blank 32. In other words, the perforation 37 allows the blank 32 to be easily wound and wrapped around the side wall 14 of the cup body 12 as desired in the step of forming the protective cover 20. It is important to properly determine the size of the hole and the distance between adjacent holes of the perforation 37 in order to prevent the blank from being torn when it is wound to form the protective cover 20. More specifically, the size of the hole and the distance between adjacent holes of the perforation 37 should be set at 5 mm to 8 mm. The perforation 37 can be formed in the punching step of forming the blank 32.

A test was conducted to observe the effect produced by the perforation 37, the results of which are set forth below. In this test, samples 1 to 5 of the blank 32 were prepared, these samples being different from each other by the type of fold line, so as to measure the folding strength of the samples along the fold line. In addition, the workability and the finished state when folding the blank 32 to produce the protective cover 20 were checked. The test conditions and the results of the test are shown in Table 1. The sample 1 shown in Table 1 corresponds to the blank 32 shown in Fig. 9. The perforation 37 of the sample 1 consists of holes each having a size of 5 mm and spaced 5 mm apart from each other. Punching was used to form the perforation 37 on the side of the cover board 28 of the blank 32. Samples 2 to 5 shown in Table 1 indicate verification cases. In these samples, the fold lines were formed as shown in Table 1. More specifically, the term "guide line 1" denotes a groove having a width of 1 mm. The term "minor cut" denotes a groove formed by cutting the embossed paper sheet 24 only with a cutting knife. Further, the term "guide line 2" denotes a groove having a small width formed by a cutting knife. It should be noted that in forming the fold lines, working tools in different directions were used in producing Samples 1 to 5. As for the working direction shown in Table 1, the term "front" means that a working tool was brought into direct contact with the cover board 28 when working started, whereas the term "rear" means that the working tool was brought into direct contact with the embossed paper sheet 24 when working started. Both the workability and the final state were evaluated as "O" meaning "good", "Δ" meaning "fairly good" and "x" meaning "poor". Table 1

Table 1 clearly shows that sample 1 was superior to samples 2 to 5 in terms of folding strength, workability and final condition.

Fig. 10 shows yet another modification of the blank 32 of the protective cover 20 shown in Fig. 9. In this case, a cutout 38 is formed at the upper and lower ends of each of the two perforations 37, respectively, so as to facilitate the winding of the blank 32 along these perforations 37. Of course, the presence of these cutouts 38 serves to ensure the winding of the blank 32. Desirably, the cutouts 38 should be approximately 3 mm long. These cutouts 38 can be formed together with the perforations 37 in the blank 32 punching step.

The blank 32 shown in Fig. 10 also has an adhesive application space 36. The upper and lower ends of the space 36 are defined by the inclined sides 39, each of which is inclined by approximately 15° with respect to the upper or lower arc of the blank 32. When these inclined sides 39 are inclined as shown in Fig. 10, the surface of the adhesive application space 36 is unlikely to be exposed even if the blank 32 is wound to form a truncated cone shape, which is a shape slightly different from the predetermined shape. In other words, the presence of the space 36 makes it possible to prevent the external appearance of the resulting protective cover 20 from being impaired even if the blank 32 is wound slightly unsatisfactorily.

Fig. 11 shows a cross-sectional view of a modification of the flange portion 18. In this modification, the upper end portion of the side wall 14 of the cup body 12 is folded and curled outward so as to make at least one complete turn. Then, the curled portion is squeezed by pressing in a vertical direction so that the curled portion can become flat. The inner surface of the The flange portion 18 has no adhesion state, and the restoring force of the flange portion 18 causes the lower surface of the flange portion 18 to abut against an upper end portion 20a of the protective cover 20. As a result, the flange portion 18 is prevented from being further deformed by its restoring force. It should also be noted that a gap G occurring on the outer surface of the protective cover 20 between the upper end of the protective cover 20 and the lower end of the flange portion 18 is reduced to 0.5 mm or less.

In the conventional heat-insulating cup, a gap of at least about 1.0 mm was formed between the protective cover and the flange portion of the cup body because it was necessary to use a tool for mounting the protective cover to the cup body. This above-mentioned large gap can probably accommodate a cup handling arm. However, in the modification shown in Fig. 11, the gap in question is reduced to 0.5 mm or less, so that the above-mentioned difficulty is eliminated.

The flange portion 18 is crimped by being pressed in a vertical direction so that it has a flat surface. As a result, the area of the flat surface of the flange portion 18 brought into contact with the lid 11 is increased so that satisfactory sealing properties are ensured. In addition, even if the crimped portion before forming the flange portion 18 has the same size, the overhang length L of the flange portion 18 from the protective cover 20 is increased as compared with the case where the crimped portion is not crimped. As a result, the heat-insulated cup is prevented from falling out of a conveyor holder of the conveyor. In this modification, the overhang length L is set to be in a range between 1.5 mm and 2.5 mm.

Fig. 12A to 12D together show the formation of the flange portion 18 shown in Fig. 11. More specifically, After forming the basic shape 106 of the cup body 12 shown in Fig. 5, the side wall 14 of the cup body 12 is folded outwardly along its open upper peripheral region and thereafter wound to make at least one complete turn so that a curled portion 42 is formed as shown in Fig. 12A.

In the next step, the curled portion 42 is flattened by being crimped under heat and pressure so that the flange portion 18 is formed with an upper plate 44 and a lower plate 46 as shown in Fig. 12B. In this step, the curled portion 42 is not completely crimped. More specifically, a free space should be provided inside the flange portion 18. In addition, the upper plate 44 and the lower plate 46 should not be bonded to each other. In this embodiment, only the inner surface of the side wall 14 is coated with a polyethylene film 13 as shown in Fig. 14. As a result, even if the curled portion 42 is completely crimped, the upper plate 44 is not bonded to the lower plate 46. In addition, the top of the curled portion 42 is not adhered to the upper portion of the side wall 14. However, it is desirable that the curled portion 42 is not completely crushed because the restoring force of the flange portion 18 is utilized in the subsequent step.

Immediately after the crimped portion 42 is crimped, the protective cover 20 is adhered to the side wall 14 of the cup body 12 as shown in Fig. 12. As described above, the upper plate 44 and the lower plate 46 are not adhered to each other within the flange portion 18, resulting in the flange portion 18 being caused to be deformed back to its original shape of the curved portion 42 due to its restoring force as shown in Fig. 12D. In other words, the lower plate 46 is pushed to the upper edge 20a of the protective cover 20 so that the width of a gap formed along the outer surface of the protective cover 20 between the protective cover 20 and the flange portion 18 decreases. It is desirable that the flange portion be deformed so as to cause the lower plate 46 to abut against the upper edge 20a of the protective cover 20 as shown in Fig. 11 so that the flange portion 18 is prevented from being further deformed due to its restoring force.

As described above, the flange portion 18 is deformed by flattening the curved portion 42, so that the contact area between the lid 11 and the flange portion 18 increases and thus the overhang length of the flange portion 18 from the edge of the protective cover 20 increases. Furthermore, the width of the gap G between the protective cover 20 and the flange portion 18 can be reduced to a desired value of 0.5 or less by utilizing the restoring force of the flange 18. In utilizing the restoring force of the flange portion 18, it is important to properly select the position of the upper edge 20a of the protective cover 20 and the material of the side wall 14. It is also important to prevent the upper plate 44 and the lower plate 46 of the flange portion 18 from being stuck together.

Fig. 13 shows a plan view of the surface of the cover board 28 according to a modification of the present invention. In this modification, a surface embossing 48 consisting of a protruding and recessed grid pattern is formed on the entire outer surface of the cover board 28. The grid pattern of the embossing 48 is defined by a large number of grooves, which include first grooves extending in a direction at an angle of approximately 45° with respect to the axis of the cup body 12 and second grooves crossing the first grooves at substantially right angles. The average distance between the first grooves and between the second grooves is approximately 1 mm. In other words, the average width of the grid element is set to approximately 1 mm. Furthermore, the embossing 48 has an average roughness defined by a ten-point average roughness (JIS B 0601) of approximately 54 µm.

The raw material sheet of the linerboard 28 passing through the printer 114 shown in Fig. 5 further passes through an embossing roller for forming the embossing 48 thereon. After forming the embossing 48, the raw material sheet roll 112 of the linerboard is inserted into a device for adhering the embossed linerboard 24 to the raw material sheet.

Desirably, the embossing 48 has an average width of the raster element within a range between 500 µm and 1500 µm. In addition, the average roughness of the embossing 48 defined by the ten-point average roughness should desirably be within a range between 40 µm and 100 µm, with the greatest roughness being less than 120 µm. If the raster width and the surface roughness mentioned above are larger than the upper limits mentioned above, the letters or patterns applied to the outer surface of the heat-insulated cup are likely not to be recognized clearly and sharply. In contrast, if the raster width and the surface roughness are smaller than the lower limits of the ranges mentioned above, the actual temperature of the heat-insulated cup is felt to be higher by the user. In addition, the surface of the cup can slip. Furthermore, patterns other than the embossing 48 can be formed on the surface of the cover cardboard 28. For example, a so-called "dot pattern" can be formed on the surface of the cover cardboard 28, which consists of a large number of projections and depressions, each of which is essentially the same size as the grid element in the embossing 48.

In the case of the use of the modified cover board 28 as described above, the protective cover 20 the embossed paper sheet 24 having the embossing 25 of large spots and the cover board 28 having the embossing 48 having the grid pattern formed thereon, the cover board 28 covering the outer surface of the embossed paper sheet 24. This special structure enables the letters or patterns formed on the outer surface of the protective cover 20 to be easily and accurately visually recognized. In addition, the surface of the protective cover 20 is unlikely to slip when held by the user. Furthermore, the large embossed spots of the embossing 25 formed in the embossed paper sheet 24 serve to effectively suppress heat transfer to the outer surface of the protective cover 20. In addition, the slightly embossed grid pattern of the embossing 48 formed on the cover board 28 serves to lower the effective temperature of the heat-insulating cup which is felt by the user when holding the cup.

Fig. 14 is a cross-sectional view of a modification of the side wall 14 of the cup body 10. In this modification, a matting treatment is applied to the polyethylene film 13 covering the inner surface of the side wall 14 so that a matted surface 13a is formed. The matted surface should have an average roughness as defined by the ten-point average roughness (JIS B 0601) of 10 µm to 30 µm. If the average roughness of the matted surface is less than the lower limit of the above-mentioned range, blocking is likely to occur. On the other hand, if the above-mentioned average roughness is greater than the upper limit of the above-mentioned range, the matting treatment itself becomes difficult. The average roughness of the matted surface as defined by the ten-point average roughness should not be greater than 60% of the thickness of the polyethylene film 13. Otherwise, it may happen that 13 pinholes are formed in the polyethylene film, which leads to low reliability in terms of resistance to water penetration Incidentally, other hard films that can be heat sealed, such as a polyester film, may be used instead of the polyethylene film 13.

In the modification shown in Fig. 14, the inner surface of the sides 14 of the cup body 12 is covered with a plastic layer such as the polyethylene film 13 having a relatively rough surface, that is, a roughness defined by the ten-point average roughness of 10 µm to 30 µm. As a result, even when a large number of heat-insulated cups are telescopically stacked, the individual cups can be easily released from the stacked arrangement despite the fact that the protective cover 20 has a high elasticity. When the outer surface of the cover board 28 is covered with a varnish layer, the release of the individual cups from the stacked arrangement can be further facilitated. Furthermore, the plastic layer should have a roughness defined by the ten-point average roughness that is not greater than 60% of the thickness of the plastic layer so that the formation of tenon holes in the plastic layer is prevented.

Tests were conducted to confirm the effect produced by the matting treatment and to observe the relationship between the marking treatment applied to the surface of the polyethylene film 13 and the varnish layer formed to cover the outer surface of the cover board 28. In these tests, the static friction force and the static friction coefficient between a polyethylene film having a matted surface and a varnish layer having a smooth surface were measured on the basis of JIS K 7125. Table 2 shows the test data of samples AD used in these tests. In Table 2, "roughness" indicates the ten-point average roughness of the polyethylene film and "varnish layer" indicates the type of varnish layer. Samples A and B were prepared so as to conform to the surface roughness shown in Fig. 14. side wall 14, while samples C and D were manufactured to have a less frosted surface, the static friction forces (gf) and static friction coefficients measured during the tests being shown in Table 2 under "SFC" and "CSF", respectively. Table 2

As is clear from Table 2, the static friction coefficient for Samples A and B is smaller than that for Samples C and D. This clearly supports that the matting treatment applied to the polyethylene film 13 as shown in Fig. 14 enables the individual heat-insulated cups, which are telescopically stacked one on top of the other during storage, to be easily released from the stacked arrangement.

Fig. 15 shows how a matting treatment is applied to the polyethylene film 13 formed to cover the side wall 14 of the cup body 12. In the first step, a raw material sheet of the side wall 14 of the cup body 12 is prepared. As shown in Fig. 14, molten polyethylene is supplied from an extruder 144 to the raw material sheet 140 coming from a sheet roll 142 to coat the raw material sheet 140 with a polyethylene film. Thereafter, the polyethylene film formed to cover the raw material sheet 140 is cooled by a cooling roll 146 having a surface subjected to a matting treatment. As a result, a Matting treatment is applied as the raw material sheet 140 is moved along the surface of the cooling roll 146. Further, the raw material sheet 140 after the cooling treatment and the matting treatment is wound on a sheet roll 148.

Fig. 16 shows a partially broken front view of a heat-insulating cup according to another embodiment of the present invention, and Fig. 17A shows a cross-sectional view taken along the line XVII-XVII shown in Fig. 16. The reference numerals have already been explained in conjunction with the embodiments shown in Figs. 1 and 2 and are also used in Figs. 16 and 17A to designate the same elements of the cup.

In the embodiment shown in Figs. 16 and 17A, the protective cover 20 is made of a multi-layer structure comprising a first thin paper sheet 22 designed to cover the entire outer surface of the side wall 14, the embossed paper sheet 24 designed to cover the entire area of the first thin paper sheet 22, a second thin paper sheet 26 designed to cover the entire area of the embossed paper sheet 24, and the paperboard cover board 28 designed to cover the entire area of the second thin paper sheet 26.

The embossed paper sheet 24 and the cover board 28, which have already been described in connection with Fig. 2, are used in the embodiment shown in Figs. 16 and 17A. The first thin paper sheet 22 is opaque and white, exhibits medium performance whitening properties and should have a basis weight of approximately 30 g/m². Likewise, the second thin paper sheet 26 is opaque and white, exhibits medium performance whitening properties and should have a basis weight of approximately 30 g/m².

The first thin paper sheet 22 cooperates with the cover board 28 to prevent the embossed paper sheet 24 from being warped, to improve the adhesive strength between the cup body 12 and the protective cover 20 and to facilitate the automatic roll feeding or sheet-by-sheet feeding of the embossed paper sheet 24, thereby improving the productivity for the heat-insulated cup. To meet these requirements, it is necessary that the first thin paper sheet 22 exhibit adequate mechanical strength and adequate rigidity. More specifically, it is necessary that the first thin paper sheet 22 have a basis weight that is within the range between 20 g/m² and 100 g/m². If the basis weight exceeds the upper limit of this range, the first thin paper sheet 22 becomes excessively rigid, resulting in poor workability in manufacturing the protective cover 20. On the other hand, if the basis weight is less than the lower limit of the above-mentioned range, the rigidity and mechanical strength of the first thin paper sheet 22 become excessively low. As a result, the first thin paper sheet 22 is likely to be torn during the manufacturing process of the protective cover 20. In addition, the embossed paper sheet 24 cannot be sufficiently prevented from being warped.

The second thin paper sheet 26 is intended to prevent the cover board 28 from having grooves or the like that correspond to the projections or the like formed on the surface of the embossed paper sheet 24, to prevent the outer surface of the cover board 28 from having adhesive marks so that the external appearance is not impaired, and to facilitate the automatic roll feeding or sheet-by-sheet feeding of the embossed paper sheet 24 so as to improve the productivity of the heat-insulated cups. In order to meet these requirements, the second thin paper sheet 26 is required to have adequate mechanical strength and adequate rigidity. More specifically, That is, the second thin paper sheet 26 is required to have a basis weight which is in the range between 20 g/m² and 100 g/m². If the basis weight exceeds the upper limit of this range, the second thin paper sheet 26 becomes excessively rigid, resulting in poor workability in manufacturing the protective cover 20. On the other hand, if the basis weight is less than the lower limit of the above-mentioned range, the rigidity and mechanical strength of the second thin paper sheet 26 become excessively low. As a result, the second thin paper sheet 26 is likely to be torn during the manufacturing process of the protective cover 20.

Fig. 18 shows how to manufacture the protective cover included in the heat-insulated cup shown in Fig. 16. In the first step, an embossing treatment is applied to a white bleached kraft paper sheet coming from a sheet roll 152 so as to prepare a raw material sheet of the embossed paper sheet 24 bearing the embossing 25. Thereafter, the both surfaces of the raw material sheet of the embossed paper sheet 24 are provided with an adhesive such as a vinyl acetate type adhesive by adhesive rolls 156 and 158. The adhesive application may be carried out immediately after the embossing treatment or simultaneously with the embossing treatment.

Simultaneously with the unwinding of the bleached kraft paper sheet from the roll 152, the first and second thin paper sheets 22 and 26 are unwound from the raw sheet rolls 162 and 164, respectively, so as to be superimposed on the upper and lower surfaces of the raw material sheet of the embossed paper sheet 24 and thereafter adhered to the raw material sheet of the embossed paper sheet 24 by a pair of spacer rollers 166 and a pressing belt 168. One of the paired rollers 166 is fixed and the other roller is elastically urged toward the one roller by a spring force so that a predetermined gap is formed between the paired rolls. The special construction enables the first and second thin paper sheets 22 and 26 to be adhered to the embossed paper sheet 24 without compressing the embossing 25.

The raw material sheet having the first and second thin paper sheets 22 and 26 each adhered to the embossed paper sheet 24 is separated by a separating device 172 to produce spacers 156 each having a predetermined width. The spacer 165 has a size such that a plurality of protective covers 20 can be produced from each spacer 165.

On the other hand, offset printing by a printer 176 or varnish coating is applied to the surface of the raw material sheet of the cover board 28 to obtain a raw material sheet roll 174 of the cover board 28. By this printing, letters or patterns relating to the trade name of the heat-insulated cup are applied to the surface of the raw material sheet of the cover board 28, which forms the surface of the protective cover 20 of the resulting heat-insulated cup. Thereafter, the raw material sheet of the cover board 28 is separated by a separating device 178 to produce spacers 175 having the same size as the spacers 165.

Furthermore, the spacers 165 are stacked one on top of the other and automatically fed one by one by a feeder 182, followed by applying an adhesive such as a vinyl acetate type adhesive to the second thin paper sheet 26 by an adhesive application roller 186. The spacers 175 are also stacked one on top of the other and fed one by one by a feeder 184 simultaneously with the feeding of the spacer 165 such that the spacer 175 is superimposed on the adhesive-applied surface of the spacer 165 and is adhered to the spacer 165 by a pair of spacer rollers 188 and a pressing belt 192, so as to form a spacer 194 having a One of the paired rollers 188 is stationary, the other roller being elastically movable towards the one roller by a spring force, which means that the intermediate pieces 165 and 175 can be stapled together without the embossing 25 of the embossed paper sheet 24 being compressed.

The intermediate piece 194 of the stapled structure having a plurality of cutout portions or sector portions on which the letters or patterns relating to the trade name of the heat-insulated cup are printed is punched in the subsequent step to obtain a plurality of sector blanks 32 of the protective cover 20. Further, the protective cover 20 is attached to the cup body 12 as described above, so as to obtain a heat-insulated cup shown in Fig. 17.

In the manufacturing process shown in Fig. 18, a plurality of spacers 165 each comprising the embossed paper sheet 24 are stacked one on top of the other. However, in this step, the projections/recesses, i.e., the embossing 25, of the embossed paper sheets 24 comprised in the adjacent spacers 165 do not engage with each other since the first and second thin paper sheets 22 and 26 have been previously adhered to the respective surfaces of the embossed paper sheet 24. As a result, the spacers 165 for adhering the cover board 28 to the spacer 165 can be automatically fed one by one in the subsequent step, resulting in increased productivity for the heat-insulated cups. Furthermore, the second thin paper sheet 26 prevents the cover board from bearing traces of the stapling operation and irregularities consistent with the surface condition of the embossed paper sheet 24. In other words, the second thin paper sheet 26 effectively prevents the external appearance of the heat-insulating cup from being impaired.

The first thin paper sheet 22 of the protective cover 20 is adhered to the side wall 14 of the cup body 12 with an adhesive to fix the protective cover 20 to the cup body 12. As a result, even if the protective cover 20 is wrapped around the side wall 14 in the adherence step, the protective cover 20 can be adhered to the cup body 12 without failure. In addition, point-by-point adherence is achieved between the first thin paper sheet 22 and projections of the embossed paper sheet 22 and between the second thin paper sheet 26 and projections of the embossed paper sheet 22. The adherence process is performed on a flat plane or a curved plane having a large radius of curvature. In addition, the first and second thin paper sheets 22 and 26 can be deformed as desired. It follows that the first and second thin paper sheets 22 and 26 can be satisfactorily adhered to the embossed paper sheet 24.

In the manufacturing process shown in Fig. 18, the spacers 165 having a predetermined width are automatically fed one by one to form spacers 194. However, automatic feeding from a roll as shown in Fig. 5 may be adopted instead of feeding one by one. More specifically, the raw material sheets of the first and second thin paper sheets 22 and 26 are adhered to the upper and lower surfaces of the embossed paper sheet 24 to obtain a laminate structure, followed by winding the laminate structure as a first roll before separation, the roll corresponding to the roll 108 shown in Fig. 5. On the other hand, letters or patterns are successively printed on the surface of the raw material sheet before the separation of the cover board 28, followed by winding up the raw material sheet printed with letters or the like as a second roll corresponding to the roll 112 shown in Fig. 5. Thereafter, these raw material sheets are unwound from the first and second rolls simultaneously with each other such that the raw material sheet of the cover board 28 is adhered to the second thin paper sheet 26 of the raw material sheet of the laminated structure which is unwound from the first roll. Further, the resulting adhered sheet is separated to obtain the spacers 194 having a predetermined size or to directly obtain the sector blank 32 of the protective cover 20.

In the modified process described above, it is possible not to wind up the first roll but to feed the attached raw material sheets 22, 24 and 26 as they are and to combine them directly with the raw material sheet of the cover board 28 fed from the second roll.

Furthermore, both the first and second thin paper sheets 22 and 26 may be added to the protective cover 20 shown in Fig. 2, which comprises the embossed paper sheet 24 and the cover board 28. In this case, the projections/recesses, i.e., the embossing 25, of the embossed paper sheet 24 included in the adjacent stacked intermediate pieces do not interfere with each other. As a result, the embossed paper sheet 24 can be automatically fed from a roll or can be easily fed individually, resulting in improved productivity and low manufacturing cost for the heat-insulating cup.

When only the first thin paper sheet 22 is adhered to the protective cover 20 comprising the embossed paper sheet 24 and the cover board 28, as shown particularly in Fig. 17B, surface contact is achieved between the first thin paper sheet 22 and the cup body 12, resulting in improved adhesive strength between the cup body 12 and the protective cover 20. In addition, the embossed paper sheet 24 is sandwiched between the first thin paper sheet 22 and the cover board 28. As a result, the embossed paper sheet 24 is prevented from being deformed over time, as for example, is warped, so that a high adhesive strength between the cup body 12 and the protective cover 20 is ensured over a long period of time.

In the case of adding only the second thin paper sheet 26 to the protective cover 20, the second thin paper sheet 26 prevents the cover board from having an irregularity that matches the surface state of the embossed paper sheet 24 or from having traces of the stapling process, so that the external appearance of the heat-insulated cup is prevented from being impaired.

Fig. 19 shows a partially broken away perspective view of a heat-insulated cup 10 according to another embodiment of the present invention, the cup 10 including a cover 11A shown removed from the cup 10. The reference numerals already explained in connection with the embodiment shown in Figs. 1 and 2 are also used in Fig. 19 to designate the same elements of the cup.

In this embodiment, a black horizontal line 52 is drawn as a marking line over substantially the entire outer peripheral surface of the side wall 14 of the cup body 12 so as to provide a criterion for pouring, for example, hot water into the cup. The marking line 52 may be printed with black ink using, for example, carbon black on the cardboard used for the side wall 14. The marking line 52 should be printed such that when the cardboard printed with the line 52 is wound to form the side wall 14, the two ends of the line 52 are aligned with each other, thus allowing the line 52 to define a predetermined liquid level within the cup.

The cover 11A made of a transparent resin mold is mounted on the flange portion 18 of the side wall 14. It It is possible to use a cover 11A made of paper. Furthermore, a sheet-like cover 11 as shown in Fig. 1 may be mounted to the flange portion 18 instead of the cover 11A.

The protective cover 20 used in the embodiment of Fig. 19 has a multi-layer structure consisting of the first thin paper sheet 22, the embossed paper sheet 24 and the cardboard cover board 28. However, the protective cover 20 may have another multi-layer structure. For example, the protective cover 20 may consist of the embossed paper sheet 24 and the cover board 28 as shown in Fig. 2, or it may consist of the first thin paper sheet 22, the embossed paper sheet 24, the second thin paper sheet 26 and the cover board 28 as shown in Fig. 16. Furthermore, the protective cover 20 may be formed of only the embossed paper sheet as shown in Fig. 22, which will be described below.

The marking line 52 should be visually recognizable from the inside of the cup body 12 covered by the protective cover 20. To facilitate the visual recognition, it is important to properly determine the materials and other conditions of the side wall 14 and the line 52. Of course, it is most desirable that the line 52 be visually recognizable only by light from the inside of the cup body 12. In view of this requirement, the paperboard used to form the side wall 14 should have a basis weight within a range of between 170 g/m² and 310 g/m² and should have a thickness within a range of between 220 µm and 420 µm. The Munsell system lightness Bw of the color of the side wall 14 should be 6 to 10 and preferably 8 to 10. The brightness according to the Munsell system Bm of the color of the marking line 52 should be 0 to 7 and preferably 0 to 5. It is also important that the condition Bw - Bm ≥ 3 is met.

In order to facilitate the optical recognition of the marking line 52, it is also important that the condition Bc - Bm ≥ 1 is satisfied, where Bc denotes the Munsell brightness of the color of the thin paper sheet 22, which is the color of the inner surface of the protective cover 20. Furthermore, the value of Bc should be within a range between 6 and 10, and preferably between 8 and 10. In addition, it has been confirmed by experiments that in the case of using the marking line 52 with the Munsell brightness of 0, the marking line 52 can be easily optically recognized even if the Munsell brightness on the inner surface of the protective cover 20 is close to 0. When the thin paper sheet 22 is not included in the protective cover 20, the inner surface of the protective cover 20 is defined by the embossed paper sheet 24. It follows that the color of the embossed paper sheet 24 is determined according to the above-mentioned conditions for selecting the color of the thin paper sheet 22.

If the basis weight and thickness of the adhesive board used to form the side wall 14 are higher than the upper limit of the above-described ranges, it is difficult to easily visually recognize the marking line 52. On the other hand, if said basis weight and thickness are less than the lower limit of the above-described ranges, the paperboard cannot have the rigidity and mechanical strength required for the cup body 12. If the Munsell brightness Bw of the paperboard used to form the side wall 14 is less than the lower limit of the above-described range, it is difficult to easily visually recognize the marking line 52. It is also difficult to easily visually recognize the marking line 52 if the Munsell brightness Bm of the marking line 52 is higher than the upper limit of the above-described range. For each cardboard box used to form the side wall 14 of the thin paper sheet 22 and the marking line 52, it is desirable that it is colorless, although it is permissible for these elements of the cup to be colored. Furthermore, the marking line 52, which is a single straight line in the embodiment of Fig. 19, may be replaced by, for example, a dashed line, a double line, a linear arrangement of small triangles, dots, letters, numbers and the like.

Fig. 20 is a partially broken perspective view of a modification of the heat-insulating cup shown in Fig. 19. In the modification shown in Fig. 20, a laterally elongated open window 54 is formed in the protective cover 20 so as to partially expose the marking line 52 formed on the outer peripheral surface of the cup body 12. The window 54 can be formed in the step of punching the blank 32 of the protective cover 20, resulting in the window 54 being able to be formed with no substantial increase in the manufacturing cost of the heat-insulating cup. In addition, since the marking line 52 is printed along the entire outer peripheral surface of the side wall 14 of the cup body 12, the horizontal position of the window 54 does not need to be aligned with the marking line 52.

The window 54 allows the marking line 52 to be optically recognized inside the cup body 12 using the incident light from the outside, resulting in the marking line 52 being optically recognized even more easily. This makes it unnecessary to take into consideration the color brightness according to the Munsell system of the inner surface of the protective cover 20, that is, the thin paper sheet 22, although it is necessary to take into consideration the specific brightness in the heat-insulated cup in Fig. 19. However, since it is necessary to use the incident light from the outside for the optical recognition of the marking line 52, it is necessary that the paperboard used to form the side wall 14 has a basis weight of 170 g/m² to 310 g/m² and a thickness of 220 µm to 420 µm. On the other hand, the brightness according to the Munsell system Bw of the color of the side wall 14 should be 6 to 10 and preferably 8 to 10. The brightness according to the Munsell system Bm of the color of the marking line 52 should be 0 to 8 and preferably 0 to 7. Furthermore, it is important that the condition Bw - Bm ≥ 2 is met.

Desirably, any adhesive board used to form the side wall 14 and the marking line 52 is colorless, although it is permissible for these elements of the cup to be colored. Furthermore, the marking line 52 exposed through the open window 54 and formed as a single straight line in the variation shown in Fig. 20 may be replaced by, for example, a dashed line, a double line, a linear array of small triangles, dots, letters, numbers or the like.

The window 54 facilitates visual recognition of the marking line 52 from the inside of the cup. In addition, the level of the liquid poured into the cup can be recognized through the window 54 from the outside of the cup. In other words, the level of the liquid poured into the cup can be compared with the marking line 52. In this way, the window 54 is extremely useful in the case where the user of the cup cannot see into the cup.

It is possible to enlarge the window 54 or to provide a plurality of windows 54 so as to further facilitate the visual recognition of the marking line 52. It should be noted, however, that if the open area created by the window 54 is excessively large, the thermal insulation properties of the cup will be reduced.

Fig. 21 is a partially broken perspective view of another modification of the heat-insulated cup shown in Fig. 19. In the modification of Fig. 21, the marking line 52 is not formed on the cup body 12 at all. . In addition, a triangular window 56 is formed in the protective cover 20. The window 56 can be formed in the punching step for forming the blank 32 of the protective cover 20, with the result that the window 56 can be formed without a substantial increase in the manufacturing cost of the heat-insulating cup.

The window 56 can be recognized from the inside of the heat-insulated cup by utilizing the light incident from the outside, resulting in that the contour itself of the window 56 can be used as a marking criterion. This makes it unnecessary to draw a marking line 52 as in the heat-insulated cup shown in Fig. 19. It is also unnecessary to consider the brightness according to the Munsell system of the color on the inner surface of the protective cover 20, that is, the thin paper sheet 22. However, since it is necessary to recognize the contour of the window 56 by utilizing the light incident from the outside, it is necessary that the cardboard used to form the side wall 14 has a basis weight within a range between 170 g/m² and 310 g/m² and a thickness within a range between 220 µm and 420 µm.

As described above, the window 56 can be recognized from the inside of the cup, allowing use of the window 56 as a marking criterion.

In addition, the level of the liquid poured into the cup can be recognized through the window 56 from the outside of the cup. It follows that the level of the liquid poured into the cup can be compared with the marking criterion using the window 56. In this way, the window 56 is extremely useful in the case where the user of the cup cannot look into the cup.

It is possible to enlarge the window 56 or to provide a plurality of windows 56 so that the optical recognition of the marking criterion is further facilitated. It should However, it should be noted that if the open area formed by the window 56 is excessively large, the thermal insulation properties of the cup will be reduced.

Claims (30)

1. A method for producing a heat-insulated cup (10) consisting of a cup body (12) having a paper side wall (14) and a paper bottom wall (16) and a paper protective cover (20) attached to cover the side wall of the cup body, the protective cover (20) comprising an embossed paper sheet (24), characterized by the following steps: Adhering a first raw material sheet of the embossed paper sheet (24) and a second raw material sheet of a cover board (28) to each other with a first adhesive, punching the stapled assembly from the first and second raw material sheets to produce a blank (32) having the shape of the protective cover (20), Applying a second adhesive to the blank (32), flipping the blank (32) in such a way that the cover board (28) is positioned on the outside, and Attaching the folded blank (32) as the protective cover (20) to the side wall (14) of the cup body (12). 2. Method according to claim 1, characterized in that the step of attaching the folded blank (32) to the side wall (14) of the cup body (12) comprises the following sub-steps: Applying the second adhesive to the blank (32) and adhering the blank (32) to the side wall (14) with the second adhesive while wrapping the blank around the side wall. 3. Method according to claim 2, characterized in that both side end portions (33a, 33b) of the blank (32) are arranged opposite each other when the blank is attached to the side wall (14). 4. Method according to claim 1, characterized in that the step of attaching the folded blank (32) to the side wall (14) of the cup body (12) comprises the following sub-steps: Assembling the blank (32) into a cone whose inner shape matches the outer shape of the cup body, and Attaching the cone to the side wall (14) while fitting it over the side wall (14) of the cup body (12). 5. Method according to claim 1, characterized in that the step of attaching the first raw material sheet to the second raw material sheet comprises the following sub-steps: Preparing the first raw material sheet by applying an embossing treatment (116) to a sheet coming from a first sheet roll (108), Applying the first adhesive to the first raw material sheet simultaneously with or after the embossing treatment and Adhering the second raw material sheet of the cover board (28) coming from a second sheet roll (112) simultaneously with the coming out of the sheet from the first sheet roll (108) to the first raw material sheet with the first adhesive. 6. Method according to claim 1, characterized by the further steps: Folding an open upper peripheral end portion of the side wall (14) of the cup body (12) outwardly in such a manner that the folded portion has at least one complete rotation to form a ringed portion (42), pressing the curled portion (42) in a vertical direction to compress the curled portion flat, thereby forming a flange portion (18) having an upper plate (44) and a lower plate (46) that are not bonded together within the flange portion, and Adhering the protective cover (20) to the side wall (14) immediately after the step of pressing the curled portion (42) in such a manner that the flange portion is deformed due to its restoring force, whereby the distance between the lower plate (46) of the flange portion (18) and an upper end (20a) of the protective cover (20) is reduced. 7. The method according to claim 6, characterized by the further step of allowing the lower surface of the lower plate (46) of the flange portion (18) to abut against the upper end portion (20a) of the protective cover (20) so as to prevent the flange portion from further deforming due to its restoring force. 8. Method according to claim 1, characterized in that the second adhesive comprises a first portion which is applied under pressure to two band-like first regions (34) formed at side end regions of the blank (32) of the protective cover (20) and a second portion which is applied without pressure to at least one second region (35) arranged on the blank outside the two first regions. 9. Method according to claim 8, characterized in that the second adhesive further comprises a third portion which is applied together with the first portion under pressure to a band-like region (34) along a centerline of the blank (32) of the protective cover (20). 10. Method according to claim 1, characterized in that the second adhesive has a first portion which is applied under pressure to two band-like first regions (34) which are formed at side end regions of the blank (32) of the protective cover (20) and a second portion which is applied without pressure to at least one second region which is arranged on the side wall (14). 11. Method according to claim 10, characterized in that the second adhesive further comprises a third portion which is applied together with the first portion under pressure to a band-like region (34) along a center line of the blank (32) of the protective cover (20). 12. The method according to claim 1, characterized in that the protective cover further comprises a thin paper sheet (22, 26) which is arranged on at least one surface of the embossed paper sheet (24) and has a basis weight within a range between 20 g/m² and 100 g/m², the method further comprising the following steps: Attaching a third raw material sheet of the thin paper sheet (22, 26) to the first raw material sheet of the embossed paper sheet (24), adhering the second raw material sheet of the cover board (28) to either the first or the third raw material sheet to prepare a coated sheet consisting of the first, the second and the third raw materials, and Punching the coated sheet to produce the blank (32) of the protective cover (20). 13. Heat-insulated cup with a cup body (12) with a paper side wall (14) and a paper bottom wall (16) and an embossed paper protective cover (20) which is attached to cover the side wall of the cup body, characterized in that the protective cover (20) is made by wrapping a blank (32) having a multi-layer construction comprising the embossed paper sheet (24) and a paper liner (28) adhered to the embossed paper sheet, the blank (32) being wrapped such that the liner (28) is positioned on the outside and the blank (32) is adhered to the cup body. 14. A heat-insulated cup according to claim 13, characterized in that the embossed paper sheet (24) has a basis weight within a range between 50 g/m² and 180 g/m² and the cover board (28) has a basis weight within a range between 180 g/m² and 270 g/m². 15. A heat-insulated cup according to claim 13, characterized in that the blank (32) of the protective cover (20) is adhered to the side wall (14) of the cup body (12) in such a manner that both side end portions (33a, 33b) of the blank are arranged opposite each other. 16. A heat-insulated cup according to claim 13, characterized in that an inner surface of the side wall (14) is covered with a plastic sheet (13) having a thickness of 20 to 60 µm, and a matte treatment (13a) is applied to the surface of the plastic sheet to allow the plastic sheet to have a roughness according to the ten-point average roughness within a range between 10 µm and 30 µm which is not more than 60% of the thickness of the plastic sheet. 17. Heat-insulated cup according to claim 16, characterized in that the outer surface of the cover cardboard (28) is covered with a layer of varnish (30). 18. A heat-insulated cup according to claim 13, characterized in that a surface embossing (48) is formed on the outer surface of the coverboard (28) for forming a projection and recess pattern, elements of the projection and recess pattern having an average width within a range between 500 µm and 1500 µm and the surface embossing (48) having a roughness according to the ten-point average roughness within a range between 40 µm and 100 µm. 19. Heat-insulated cup according to claim 13, characterized in that it also has the following: a flange portion (18) prepared by folding an open upper peripheral end portion of the side wall (14) of the cup body (12) outward in such a manner that the folded portion makes at least one complete turn, followed by pressing the folded portion in a vertical direction while preventing the folded portion from sticking to the inside, and a position of an upper end portion (20a) of the protective cover (20) and a material of the side wall (14) are selected such that a gap between the protective cover (20) and the flange portion (18) along the outer surface of the protective cover has a width reduced to 0.5 mm or less by the deformation of the flange portion caused by its restoring force. 20. Heat-insulated cup according to claim 19, characterized in that the lower surface of the flange portion (18) abuts the upper end portion (20a) of the protective cover (20) so as to prevent the flange portion from being further deformed by its restoring force. 21. A heat-insulated cup according to claim 13, characterized in that the protective cover (20) is adhered to the side wall with an adhesive which has a first portion applied under pressure to two band-like first regions (34) formed at side end portions of the blank (32) of the protective cover (20) and a second portion applied without pressure to at least one second region (35) arranged between the two first regions. 22. A heat-insulated cup according to claim 21, characterized in that the adhesive further comprises a third portion applied along the first portion under pressure to a band-like region (34) along a center line of the blank (32) of the protective cover (20). 23. A heat-insulated cup according to claim 13, characterized in that the protective cover (20) further comprises a thin paper sheet (22, 26) arranged on at least one surface of the embossed paper sheet (24) and having a basis weight within a range between 20 g/m² and 100 g/m². 24. Thermally insulated cup according to claim 23, characterized in that the thin paper sheet (22, 26) is arranged between the side wall (14) and the embossed paper sheet (24). 25. Heat-insulated cup according to claim 13, characterized in that the protective cover (20) further comprises a perforation (37) which serves to facilitate the process of turning. 26. A heat-insulated cup according to claim 25, characterized in that the protective cover (20) further comprises cutouts (38) formed at the upper and lower ends of the perforation (37). 27. A heat-insulated cup according to claim 13, characterized in that a mark (52) as a criterion for the liquid poured into the cup (10) is printed on an outer surface of the side wall (14) of the cup body (12), the side wall (14) being formed of a paper sheet having a basis weight within a range between 170 g/m² and 310 g/m² and a thickness within a range between 220 µm and 420 µm, the paper sheet of the side wall (14) having a Munsell system brightness Bw of a color within a range between 6 and 10, the mark (52) having a Munsell system brightness Bm of a color within a range between 0 and 7 and the relationship Bw - Bm 3 is satisfied. 28. A heat-insulated cup according to claim 13, characterized in that a mark (52) as a criterion for pouring liquid into the cup (10) is printed on an outer surface of the side wall (14) of the cup body (12), an open window (54) is formed in the protective cover (20) for exposing at least a part of the mark (52), the side wall (14) being formed of a paper sheet having a basis weight within a range between 170 g/m² and 310 g/m² and a thickness within a range between 220 µm and 420 µm, the paper sheet of the side wall (14) having a Munsell system Bw brightness of a color within a range between 6 and 10, wherein the marking (52) has a brightness according to the Munsell system Bm of a color within a range between 0 and 8 and the relationship Bw - Bm ≥ 2 is satisfied. 29. A heat-insulated cup according to claim 13, characterized in that an open window (56) acting as a mark as a criterion for pouring liquid into the cup (10) is formed in the protective cover (20) and the side wall (14) is formed from a paper sheet having a basis weight within a range between 170 g/m² and 310 g/m² and a thickness within a range between 220 µm and 420 µm. 30. Thermally insulated cup according to claim 13, characterized in that an annular embossed line (19) acting as a mark is formed as a criterion for pouring liquid into the cup (10) on the side wall (14).