The covers and wrappers of books are printed on flat sheets that successively are marked and folded along lines that are spaced from each other of a distance substantially coinciding with the thickness of the book (spine of the book), with the cover front and back sides folded near the spine, in such a way as to make it possible to read the book keeping the sheets gathered together on the spine.

It is also possible to make other folds that correspond to the flaps of the wrapper around the cover edges.

To mark the covers and/or wrappers pre-folding machines are used, which are mainly provided with two parallel axes on which rotary marking discs and counteracting cylinders are installed. To each marking disc on one axis corresponds a counteracting cylinder on the other axis.

The central discs are spaced from each other of a distance corresponding to the thickness of the sheets to be bound or of the book to be covered, while the two intermediate discs are positioned only a few millimetres away from the inner discs, in such a way as to obtain a small band of cover that is glued to the first and last page of the book, and the two outer discs are spaced from the inner edges of a distance corresponding to the width of the book pages.

Besides the discs that mark the cover to allow it to be folded, also folding pliers and pressure rollers are provided to fold the flaps of the covers and/or wrappers completely.

Since the thickness and the width of books are variable, the position of the discs and cylinders must be varied consequently.

It is important to consider that the width of the cover edge glued to the first and last page of the book is not of primary importance for the binding and reading of the book and therefore it is often kept constant even for different books.

In the pre-folding machines used at present the adjustment of the distance between the various discs and consequently between the various rollers, as well as between the pliers and pressure rollers, is made by hand, by loosening the fastening screws of discs, rollers, pliers and pressure rollers and by shifting discs, rollers, pliers and pressure rollers by hand and then tightening the relevant fastening screws.

This adjustment operation requires suitable manual skills and considerable precision, and since it is easy to make mistakes or to be imprecise, it takes some time to carry it out properly. In fact, the position of the discs must be extremely precise and furthermore the discs must be perfectly symmetrical with respect to the centre of the spine of the cover or wrapper.

In order to eliminate all the drawbacks mentioned above, a new type of pre-folding machine for covers and/or wrappers with single and symmetrical adjustment of the various discs and rollers has been studied and implemented.

The new pre-folding machine comprises, in its main parts, two symmetrical units, each one of which is provided with marking discs and counteracting cylinders for one half of the cover, with a cover feed system and with pliers and pressure rollers for the folding of the wrapper flaps.

Each symmetrical unit as described above comprises a structure that supports two axes parallel to each other.

Each axis is provided with at least three marking discs and three counteracting cylinders.

A first marking disc is positioned at the end of one axis and the corresponding counteracting cylinder is positioned on the other parallel axis.

This first disc-cylinder assembly carries out the marking that serves to make one of the two folds of the cover spine.

A second marking disc and the relevant counteracting cylinder are installed at a short distance from the first disc-cylinder assembly, in a more central position with respect to the axes. This second disc- cylinder assembly carries out the marking that serves to fold the cover near the spine.

The third marking disc and the relevant counteracting cylinder are positioned along the axes, spaced from the first disc-cylinder assembly of a distance that substantially corresponds to the width of the book page.

The first and second disc-cylinder assemblies are fixed to the two axes, while the third disc-cylinder assembly is applied to the two axes with any system that allows it to be placed in the desired position along the axes.

The two symmetrical units are aligned, so that the two pairs of axes are perfectly aligned and that the first two disc-cylinder assemblies of each symmetrical unit face the other symmetrical unit.

Both symmetrical units are installed on guides or rails that are parallel to the two pairs of axes of the two units: one of the two units is fastened to the guides together with the first disc-cylinder assembly and aligned with the group of sheets to be bound; the second unit slides on the guides in such a way as to approach or move away from the second unit while keeping the axes aligned.

A big screw that engages with parts of the structure of the second symmetrical unit and is provided with a handwheel or handle makes it possible to move said second symmetrical unit near to or away from the fixed symmetrical unit.

The cover feed system comprises two opposing conveyor belts that receive the marked covers and convey them to the pliers for the folding of the flaps.

The conveyor belts are generally in a central position with respect to the two symmetrical units and are coupled so that each cover is held between them thanks to the pressure exerted and moved by the conveyor belts themselves.

The folding pliers are positioned at the sides of the conveyor belts.

Each pair of folding pliers comprises two wings that are symmetrical to each other, hinged to a longer side that is parallel to the direction of movement of the covers and provided with rotation lever systems.

In practice, one of the wings of the pliers is coplanar with the cover and serves as a support for the side of the cover corresponding to the book front, while the other wing is rotated in such a way as to fold the cover flap.

The pliers are installed on guides that are perpendicular to their wings and parallel to the guides and axes of the symmetrical units, so that it is possible to adapt the position of the pliers to the width of the covers or wrappers.

Two metal sheets, positioned above the fixed wings of the pliers, keep the wrappers in the correct position during the folding operations.

Beyond the wings of the pliers that make the flaps of the covers and/or wrappers there are counter-rotating rollers that are perpendicular to the direction of advance of the covers and have the function to move the covers forward and mark and reinforce the fold of the flaps.

The following is just an example among many of a practical application of the invention in question, illustrated in the attached drawings, wherein: Figure 1 shows a plan view of the new pre-folding machine, while Figure 2 shows a vertical section of the same.

The figures show the two symmetrical units (Gs, Gd), each one provided with two axes (A) parallel to each other and provided with marking discs (li) and (le) and corresponding counteracting cylinders (C).

Other cylinders (K) facilitate the shifting of the cover or wrapper to be pre-folded.

In this example the two inner discs (li) and the cylinder unit (C) that is nearest to the axis of the cover comprise two complementary cylinders (D), each one provided with a groove (Dg) and with a raised line (Dr) that marks the two central folds corresponding to the book spine and to the cover opening (Figure 3).

One of the two units (Gd) is fixed with respect to the new machine, while the other unit (Gs) slides in suitable rails (R) parallel to the axes (A) and is translated by means of a worm screw (F), in such a way as to adjust the folding width of the book cover spine.

The covers to be folded are placed into a special feed unit (S) from which they are collected and sent to the pre-folding section through the discs (li) and (le) and the cylinders (C) of the two units (Gd, Gs).

After the pre-folding phase the cover is conveyed to the folding pliers (P) by means of two coupled conveyor belts (N).

Each one of the two pairs of pliers (P) comprises two wings (A1, A2), one of which is fixed and coplanar with the cover and serves as counteracting element for the other wing (A2) that rotates to fold the cover flap around the marking made by the discs (I) of the two symmetrical units (Gd, Gs).

Finally the cover is sent through two counter-rotating rollers (M) that are perpendicular to the direction of advance of the covers and have the function to move the covers forward and mark and reinforce the folding of the flaps.

The above are the basic outlines of the invention, on the basis of which the technician will be able to put it into effect; any change which may be necessary upon implementation is to be regarded as completely protected by the present invention, provided that it is based on the same innovative concept described herein.

Therefore, with reference to the above description and to the attached drawings, the following claims are put forth.