Abstract:
A booklet of sheets folded to create a curved spine is fixedly held by clamping jaws adjacent to the spine and a forming roller is passed one or more times along the length of the protruding spine with sufficient pressure to produce a flattening of the curvature of the spine. The deformation of the spine of the booklet means that the sheets lie flat after the treatment. A retractable stop plate defines the amount by which the spine protrudes beyond the jaws.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to methods of and apparatus for producing booklets and the like, and is also concerned with booklets and the like when produced by these methods. The term “booklet” used hereinafter is intended to cover any set of folded sheets which are stitched or stapled along an axis, which are glued, or which are simply folded. The term “booklet” is therefore intended to include items such as brochures, pamphlets, manuals and the like. 
     DESCRIPTION OF THE PRIOR ART 
     Customarily, the folding of a set of up to perhaps 30 or so sheets in a stitcher/folder machine results in the finished product having a distinct bow adjacent to the spine. This means that the booklet tends to open out, giving it a less attractive appearance, and also making it more difficult to stack a number of such booklets for storage and transportation purposes because they will not lie “flat”. One cannot stack a large number of such booklets all with the spine on the same side, because the stack becomes lop-sided. One has to stack the booklets with some spines on one side and some on the other, in order to equalise the stack. 
     A number of different forms of apparatus are known which are concerned with improving the fold of a set of sheets, usually by the use of a creasing device. GB2031798A shows the use of “smoothing arms” which have surfaces which press against the spine of the book, but not in a sense to deform the spine. The purpose of the smoothing arms in GB2031798A is to smooth material accumulations around the stitching holes and to prevent the entry of glue through the stitching holes into the interior of the book. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide methods of and apparatus for treating such booklets so that the sheets will lie flat after treatment. 
     It is a further object of the present invention to provide methods of and apparatus for treating such booklets in which the spine of the booklet is deformed so that the sheets will lie flat after treatment. 
     In accordance with the present invention there is provided a method of treating a booklet of sheets folded to create a curved spine which comprises the steps of fixedly holding the folded booklet adjacent to the spine to create a protruding portion, and passing a forming means along the length of the protruding portion with sufficient pressure to produce a flattening of the curvature of the spine. 
     Preferably, the forming means is a pressure roller which is caused to undergo one or more passes along the length of the spine. 
     The amount by which the spine of the booklet protrudes clear of means by which it is fixedly held is adjustable so that this dimension can be varied in dependence inter alia on the number of sheets in the booklet and the material of which the sheets are composed. The amount of protrusion is preferably from 0.5 mm to 1.75 mm. 
     In a preferred embodiment of the invention the booklet is held clamped by jaws, which may be ribbed to improve their grip, which engage the booklet adjacent to the spine. 
     Also in accordance with the present invention there is provided apparatus for treating a booklet of sheets folded to create a curved spine, which comprises clamping means arranged fixedly to hold a set of folded sheets of material with a portion of the spine protruding from the clamping means, and forming means displaceable along the length of the protruding portion to exert pressure against the spine sufficient to produce a flattening of the curvature of the spine. 
     Preferably, the forming means comprises a roller which is arranged to be able to make one or more passes along the length of the spine. 
     In a preferred embodiment the clamping means comprises a pair of jaws, possibly ribbed, which are arranged to grip the folded sheets adjacent to the spine. 
     Also in accordance with the invention there is provided a booklet comprising a plurality of sheets of material folded about an axis and having the spine of the booklet deformed to a flattened shape. 
    
    
     BRIEF REFERENCE TO THE DRAWINGS 
     In order that the invention may be more fully understood, one presently preferred embodiment in accordance with the invention will now be described by way of example and with reference to the accompanying drawings. In the drawings: 
     FIG. 1 illustrates the insertion of a set of sheets into the clamping jaws; 
     FIG. 2 illustrates the clamping jaws closed onto the folded sheets; 
     FIG. 3 illustrates the passage of a roller to deform the spine; 
     FIG. 4 is a side view of the parts illustrated in FIG. 3, showing the passage of the roller along the spine; and 
     FIG. 5 shows the removal of the booklet after deformation of the spine. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The apparatus shown in the drawings is shown only schematically, to illustrate the sequence of movements involved in carrying out this embodiment of the method of the invention. 
     As shown in FIG. 1, a plurality of sheets  10  of paper or other material stitched/stapled at, as indicated at  11 , one or more positions along an axis to maintain the sheets in register is brought to a position above a pair of open clamping jaws  12 . The clamping jaws  12  are elongate bars which extend the length of the set of sheets  10 . Above the set of sheets is a displaceable blade  13 , in alignment with the stitching  11 , which by a downward movement will force the set of sheets down between the jaws  12 , thereby folding the sheets about the stitching axis. Below the clamping jaws  12  is a stop plate  14  which limits the downward movement of the set of folded sheets when deposited between the jaws. When the spine of the sheets contacts the stop plate  14 , the blade  13  is retracted upwards. Each of the clamping jaws  12  is provided with a longitudinally extending rib  16  which runs the length of the jaws. Alternatively, the facing surfaces of the jaws may be embossed or milled or provided with some other patterning to improve the grip. As shown most clearly in FIG. 2, the jaws engage and grip the set of folded sheets  10  when they are moved inwards to exert a clamping effect. Instead of moving both jaws  12  towards each other, one can alternatively have one jaw fixed and the other jaw movable towards and away from it. It is essential that the set of sheets  10  is firmly gripped by the clamping jaws to prevent any movement. The distance x between the upper surface of the stop plate  14  and the underside of the clamping jaws  12  is an important feature of the invention. This distance is adjustable, so that one can control the amount by which the set of folded sheets  10  protrudes below the jaws. As shown in FIG. 2, the protruding portion of the set of sheets is still convex in shape at this stage. 
     The amount of protrusion x will vary depending inter alia on the number of sheets  10  and the material of which they are composed. The sheets will normally be a paper material but the thickness, surface finish, etc. will vary and adjustment will need to be made to allow for this. A cover sheet of a different material may also have an effect. It has been found that a protrusion x of from 0.5 mm to 1.75 mm produces the optimum results under most circumstances, but it should be understood that these figures are preferred figures only and do not limit the scope of the invention. 
     If ribs  16  are provided on the jaws  12 , then the distance between the ribs  16  and the upper surface of the stop plate  14  may be between approximately 5 mm and 10 mm. 
     As shown in FIGS. 3 and 4, when the set of sheets  10  has been firmly gripped by the clamping jaws  12 , the stop plate  14  is retracted to one side and, either automatically or under the control of an operator, a forming roller  18  is arranged to travel the length of the clamping jaws, below the jaws, thereby compressing and deforming the convex spine of the sheets into a flattened shape. In its passage beneath the clamping jaws  12  the forming roller  18  is almost in contact with the jaws. This is an important feature in producing the required effect. The roller  18  thus exerts a substantial upward pressure against the spine of the folded sheets in its passage along the length of the jaws. Depending upon the number of sheets and the materials used, the roller  18  may make a single pass or more than one pass along the length of the spine in order to create the desired flattening of the spine. 
     When the roller  18  has performed its function it is returned to its inactive position at one end of the jaws and the jaws  12  are opened as shown in FIG. 5 to permit the booklet thus formed to be removed either downwards or alternatively upwards. If the booklet is to be removed upwards then after retraction of the roller  18  the stop plate  14  is moved back into position below the booklet before the clamping jaws  12  are opened. The booklet can then be lifted from the apparatus. It will be seen from FIG. 5 that the booklet when released from the jaws has a crease on front and back from the pressure of the ribs  16 . 
     By flattening the spine of the booklet in this way, the resulting product will lie flat without appreciable bowing adjacent to the spine, hence facilitating subsequent storage and transportation of the booklets. 
     Although reference has been made above to the set of sheets  10  being stitched, i.e. stapled, together before insertion into the forming apparatus, the invention can also be carried out without the sheets being stitched. In the latter case, the set of sheets can be simply folded or one could use an adhesive, for example a pressure sensitive adhesive, which will secure the sheets together under the pressure which is generated. That would require the application of the adhesive to the sheets before the folded set of sheets is inserted between the clamping jaws. 
     Although not shown in the drawings, and not described in detail above, the sequence of steps which make up the method in accordance with the invention can be controlled by an operator or can be part of an automated system after the apparatus has been set up for a particular production run. The apparatus of the present invention can also be provided as an additional element of a booklet production apparatus. In producing booklets it is conventional to stitch, then to fold, and then to trim. The forming step of the present invention would desirably follow the folding operation and would be followed by the trimming operation. Trimming is preferably left until last, in case the forming operation causes any misalignment of the sheets. 
     While the present invention has been described with reference to a particular embodiment, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present invention.