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The invention is aimed at the field of industrial machinery, in particular at converting machinery, facilitating cutting of products arranged in logs, i.e., according to formats having geometric features such that one of the three dimensions is predominant over the others.

In converting, a log is represented by products obtained from the conversion line and not yet cut, with a length of up to 3 meters.

More in detail, the invention relates to a bandsaw with a shaped band blade, which, positioned downstream of the converting line, allows the wound or folded product to be cut into commercial formats.

The converting industry deals mainly with the conversion of logs of large size into products destined to be sold to the final consumer (rolls of toilet tissue, kitchen towel, napkins, etc.), obtained by cutting the log into sections of adequately predetermined minimum length.

The cutting operations of the log are commonly carried out by means of industrial bandsaws, also called log saws.

Those with greater cutting precision are provided with a band blade of constant width, with cutting edge orthogonal to the direction of feed of the log, arranged between a pair of flywheels, at least one of which connected to a motor member. The logs are arranged on a bench that normally allows the shifting movements thereof to perform the cut.

Due to the shape of the band blade used, the aforesaid industrial bandsaws must perform out the following movements cyclically:

- stepped movement, adapted to determine feeding of the log and consequent definition of the predetermined cutting length of the log;

- cutting movement, orthogonal to the previous movement, adapted to determine shifting of the log toward the cutting edge of the blade (or vice versa) and consequent dividing of the log into sections of predetermined minimum length;

- return movement, adapted to determine the return of the log to the initial position and consequent performance of a subsequent stepped movement.

These movements, performed in alternation, interspersed by functional stops and decelerations, determine the consequent occurrence of mechanical inertia capable of greatly limiting the cutting speed of the aforesaid industrial bandsaws, and of compromising the overall efficiency of the production lines correlated therewith.

The object of the invention is to overcome the aforesaid limits and negative points of current industrial bandsaws provided with band blade.

The object of the invention is achieved with a bandsaw with a shaped band blade, according to the main independent claim 1.

Further features of the invention are described in the dependent claims.

The invention produces the following important advantages:

- it allows elimination of the cyclical cutting and return movements normally performed by industrial bandsaws, thereby eliminating the mechanical inertia that limits their cutting speed and consequently the overall productivity;

- it allows a decrease in the number of mutually moving members normally present in current industrial bandsaws, thereby reducing their structural complexity and consequently the overall production and running costs;

- it allows the process to be extended to cut logs of different materials (paper, wood, polymers, metals, etc.) with a single blade of constant and extremely limited thickness, thereby reducing buckling loads and consequently the overall stability relative to current industrial bandsaws;

- it allows the cutting of logs of easily combustible materials (paper, wood, etc.) to be performed with a blade distinguished by a limited thermal inertia;

- it allows balancing of the cutting forces, if this is performed out on at least two logs simultaneously, arranged adjacent to the blade provided with two cutting edges;

- it allows the sharpening unit of the blade to be spaced from the cutting point of the log, thereby reducing the potential risk of combustion of the processing waste (paper dust, wood shavings, etc.) caused by the heat and sparks developed by the sharpening process.

Further features and advantages of the invention will be more evident from the more detailed description set forth below, with the aid of the drawings, which show a preferred implementation thereof, illustrated by way of non-limiting example, wherein:

- Figs. 1-2 show, respectively in a front and side plan view, a bandsaw with a shaped band blade according to the invention;

- Figs. 3-4 show, in an open front plan view and in a perspective view, the structure and the operating principle of a shaped band blade for a bandsaw according to the invention.

With reference to the details of the figures, a bandsaw M according to the invention comprises:

- a band blade 1 , shaped to vary linearly from an area 2 of minimum width to an area 3 of maximum width, so as to define at least one cutting edge 4, inclined with respect to the cutting direction of the blade;

- at least one pair of flywheels 5, 6 for operation of said band blade 1 , at least one of the which associated with a motor member 7;

- a bench 8 for supporting and feeding logs L to be cut, provided with cradles 9 for housing the logs.

As is apparent in Figs. 3 and 4, the particular shape of the band blade 1 allows the bandsaw M, forming the subject matter of the invention, to perform the stepped movements of the logs L close to its area of minimum width 2 and to make the cut, by means of the related inclined cutting edge 4, during the subsequent passage of the blade from its area 3 of maximum width, thereby allowing the advantageous elimination of the cutting and return movements commonly performed by current industrial bandsaws, and the mechanical inertia resulting from these movements.

Said bandsaw M can be advantageously applied in the paper converting sector, and in particular in the cutting of wound logs L, into toilet paper or kitchen towel or similar products, to be sold to the final consumer.

Said bandsaw M can if necessary be adapted to cut logs L of materials of any type (wood, polymer, metals, etc.) modifying its method of variation from the area 2 of minimum width to the area 3 of maximum width of the related band blade 1 , and the characteristics of the inclined cutting edges 4 (smooth, serrated, etc.) and of the construction materials (metal alloys, composites, etc.) of the blade. Advantageously the number of flywheels can also be increased.

Operation of the bandsaw is as follows.

The logs L, at least individually or in pairs, in this latter case advantageously arranged on the right and on the left of the band blade 1 inside the cradles 9, are fed during the passage of the area 2 of minimum width of the band blade 1 near the bench 8. At the passage of the area 3 with width increasing to the maximum width, each single log L is cut without the need for any shifting movement of the log or the blade.

The cutting process can thus take place only with the movement for stepped feed of the log(s) and of rotation of the flywheels that transmit motion to the shaped blade.