Method and apparatus for producing folders

A method and an apparatus for producing folders of the kind comprising two cover sheets, a spine, which is connected with the cover sheets by means of creasing lines, and a binding agent, which is applied to the inside of the spine and which is activable to connect sheets inserted between the cover sheets to the spine. The binding agent is applied to the spine and to the cover sheets while the cover sheets are essentially parallel to each other and perpendicular to the spine.

TECHNICAL FIELD
 The present invention relates to a method and an apparatus for producing
 folders of the kind comprising two cover sheets, a spine, which is
 connected with the cover sheets by means of creasing lines, and a binding
 agent, which is applied to the inside of the spine and which is activable
 to connect sheets inserted between the cover sheets to the spine.
 Folders of this kind have been widely used, especially folders using
 hot-melt glue as the binding agent. On insertion of a stack of sheets in
 the folder into contact with the hot-melt glue in the spine of the folder,
 the folder with contents is placed in a so called binding machine, in
 which the hot-melt glue is heated such that the stack of sheets will sink
 into the glue. After cooling, the stack of sheets is connected with the
 spine of the folder.
 PRIOR ART
 There are previously known a variety of methods and devices for
 manufacturing folders of the above described type.
 A common method is attaching a solid strip of glue to a flat folder blank,
 which will then be folded along creasing lines on either side of the strip
 of glue to define a finished folder. Attachment of the strip of glue and
 forming of the creasing lines may be carried out, for example, in the way
 disclosed in the Swedish patent application as published for opposition
 413 647, and the subsequent folding may take place, for example, in the
 way described in the Swedish patent application as published for
 opposition 431 975.
 These known methods provide folders of high quality, however, it is
 necessary to use two different machines, increasing the costs of
 manufacture. Further, the side edges of the strip of glue will not adhere
 to the cover sheets in the finished folder, which under certain
 circumstances may cause sheets located on the outside in a stack of sheets
 to be situated between the strip of glue and the cover sheets in the
 subsequent binding process, so that said sheets will not adhere to the
 spine of the folder.
 Another known method comprises the steps of forming creasing lines on a
 flat folder blank, or on a web of material, from which folder blanks will
 then be separated, and immediately thereafter spraying hot-melt glue
 between said creasing lines. A method like this is disclosed, for example,
 in the German Offenlegungsschrift 2 611 242.
 The major disadvantages of the latter method is that the folder blank must
 be folded in a subsequent folding operation, that the strip of glue will
 be uneven and will partly cover the creasing lines, and that the side
 edges of the strip of glue will not adhere to the cover sheets of the
 finished folder.
 In order to solve the problem of the side edges of the strip of glue not
 abutting against the cover sheets of the finished folder, a variety of
 solutions have been proposed.
 A solution of this kind is disclosed in the U.S. Pat. No. 4,289,330 showing
 that special strips of glue are attached in the area of connection between
 the cover sheets and the folder spine provided with a strip of glue.
 Manufacture of a folder of this kind is complicated and expensive and is
 difficult to carry out automatically.
 Another solution, evident from the U.S. Pat. No. 4,129,471, comprises the
 spraying of melted glue onto a flat folder blank, whereupon the blank is
 folded in order to define two cover sheets and a spine. Folding is carried
 out along lines located in the glue area. The major disadvantages of this
 solution is that folding is difficult to carry out and that the folding
 edges will be irregular and unsharp.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to eliminate, at least partly, the
 disadvantages of previously known methods and devices of the above kind
 and to provide a method and an apparatus making it possible to produce
 high-quality folders at high speed.
 This object is fulfilled in that the invention is provided with the
 features stated in the characterizing portions of the claims.

PREFERRED EMBODIMENT
 FIG. 1 shows a finished folder 1 made in accordance with the invention,
 which folder consists of two cover sheets 2 and 3, a spine 4 and a strip
 of glue 5. The cover sheets 2 and 3 are shown in FIG. 1 as parts of a
 single folder blank of cardboard or plastic but may consist of, for
 example, a front cover sheet of transparent plastic, which near the spine
 4 is attached to a flap of the remaining part of the folder made of
 cardboard. Creasing lines 6 and 7 are formed in the area between the spine
 4 and the cover sheets 2 and 3. Creasing lines 8 and 9 are also formed in
 the cover sheets 2 and 3 at a short distance from the spine 4. The strip
 of glue 5, consisting of a thermoplastic so called hot-melt glue, is
 attached to the spine as well as to those portions of the cover sheets 2
 and 3 which are located between the creasing lines 6 and 8, and 7 and 9,
 respectively.
 The folder 1 is used as a cover for a stack of paper sheets to be connected
 to the spine 4 of the folder via the strip of glue 5. The way in which
 this prebinding, so called binding, is carried out does not form part of
 the present invention and will therefore not be described. However, for
 understanding of the way binding is carried out, reference is made to the
 U.S. Pat. No. 4,678,386.
 FIGS. 2 and 3 show a conveyor 10, both upper parts 10a and 10b of which are
 moved step by step to the right in the figures. The speed of the conveyor
 10 and the times for starting and stopping the same are synchronized with
 the various operations carried out at stations A-F.
 A web of material 12 wound on a reel 11 is the starting material in the
 production of folders 1 at the stations A-F. The web 12 is fed to the
 right in FIGS. 2 and 3 and is cut into folder blanks 13 at the station A
 (=FIG. 4) by rollers 14 provided with cutting edges 14a and cutting
 grooves 14b. Each folder blank 13 delivered from the station A is
 transferred to the conveyor 10 where it is held by non-illustrated means
 whilst being transported during the entire production procedure. The web
 10 is stopped when the folder blank 13 is at the station B (=FIG. 5). At
 this station, the creasing lines 6-9 are formed in the folder blank 13 by
 creasing means including a fixed die 15 with elongated recesses 15a and an
 upwardly-downwardly movable punch 16 with elongated projections 16a, which
 are partly pressed into the recesses 15a, thereby forming the creasing
 lines.
 After creasing and activation of the conveyor 10, the folder blank 13 will
 arrive at the station C (=FIG. 6) where the conveyor will be stopped once
 again. At this station, the folder blank 13 is folded along the creasing
 lines 6-9 by folding means including a fixed die 17 and an
 upwardly-downwardly movable punch 18. The die 17 is provided with an
 elongated recess 17a, the width of which slightly exceeds the distance
 between the creasing lines 6 and 7, and the height of which slightly
 exceeds the distance between the creasing lines 6 and 8, and 7 and 9,
 respectively. The side walls of the recess 17a are preferably parallel but
 may deviate somewhat from this orientation. When the punch 18 is pressed
 downwards towards the folder blank 13 resting on the die 17, the lower
 portion of the punch, which fits into the recess 17a, will urge the
 central portion of the folder blank delimited by the outer creasing lines
 8 and 9 thereon into the recess 17a in order to define a U-shaped channel
 in the folder blank, while the portion of the punch which is not
 immediately above the recess will press the portions of the folder blank
 located outside the creasing lines 8 and 9 towards the die 17.
 On reactivation of the conveyor 10, the folder blank 13 will be transported
 to the station D (=FIG. 7), the shape of the folder blank remaining
 essentially the same as shown in FIG. 6. The folder blank 13 will keep
 this shape by the die 17 also extending into the station D and by an
 abutment 19, which presses the cover sheets 2 and 3 in the direction of
 the die 17, extending from the end of the station C up to and including
 the end of the station D. At the station D liquid hot-melt glue is sprayed
 into the U-shaped channel of the folder blank 13 by means of a nozzle 20,
 the lower end of which is inserted into the channel and is situated at a
 short distance from the spine of the folder blank. Injection of glue is
 suitably carried out from a fixed nozzle while the folder blank 13 is
 transported by the conveyor but, alternatively, may be carried out with
 the folder blankstanding still at the station D while the nozzle is
 displaced in the longitudinal direction of the conveyor 10.
 After application of the glue, the folder blank 13 is transported to the
 station E (=FIG. 8) with the U-shaped channel of the blank still being
 guided by the die 17, which also extends from the station D up to and
 including the station E, and possibly with the cover sheets 2 and 3 still
 outside the creasing lines 8 and 9 pressed down by the abutment 19, which
 in that case will also extend into the station E. At the station E, the
 strip of glue deposited on the folder blank will be cooled, for example,
 by a fan 21 blowing cooling air into the U-shaped channel of the folder
 blank. Cooling may take place when the conveyor 10 is moving or when it is
 standing still. On completion of the cooling, the glue in said channel
 will have solidified and adhered to the spine of the folder blank as well
 as to the areas of the cover sheets 2 and 3 which are located next to the
 spine.
 After cooling, the folder blank is transported to the station F (=FIG. 9)
 where its cover sheets are pressed upwardly-inwardly by two jaws 22 and 23
 which are movable towards and away from each other such that the cover
 sheets 2 and 3 will be essentially parallel to each other. Movement of the
 jaws 22, 23 may take place during movement of the conveyor 10 or during
 standstill of the same.
 The finished folder 1 will finally be removed from the conveyor 10 in some
 suitable, non-illustrated way.
 The apparatus described above and shown in the drawings may be modified in
 various ways. Thus, although the quality of the folder will be lowered,
 station B may be omitted, and creasing may be carried out by means of the
 punch 18 at the station C while the punch is carrying out the folding.
 Further, the abutment 19 may be omitted and an elongated nozzle for
 application of the glue may be inserted between essentially parallel or
 slightly diverging cover sheets 2, 3. If the cover sheets 2, 3 are further
 kept in these positions, cooling of the strip of glue will be less
 effective but, on the other hand, the jaws 22, 23 will probably not be
 required.
 Another modification conceivable is to place the cutting station A after
 the glue application station D or the cooling station E which, however,
 may imply that the adherence of the strip of glue to the folder blank will
 be impaired at the cutting, that the configuration of the cutting device
 must be made more sophisticated and/or that the external dimensions of the
 finished folders will vary.
 Although only one embodiment of the invention and some modifications of the
 same have been shown in the drawings and described above, it will be
 appreciated that the invention is not limited to said embodiment but will
 only be limited by what is stated in the claims.