In this description, the term cutting and winding machine refers to a machine capable of unwinding a reel of strip-like material, for example, paper or plastics film, cutting it perpendicular to its axis into two or more sections and rewinding the cut sections to form reels having an axial extent less than that of the original reel.

The cut sections are usually rewound onto a pair of separate shafts in such a way that contiguous sections of the original reel are rewound onto different shafts in an alternately offset arrangement. In particular, the various sections are rewound onto respective tubular cores, usually made from cardboard and positioned co-axially about the shafts.

More specifically, the present invention concerns a shaft for supporting cut reel sections, comprising a cylindrical body having at least one cavity in its outer surface accommodating a resilient envelope connectable to a source of fluid under pressure, for example, compressed air, and a plurality of first annular members disposed coaxially along the body.

In a prior art device described in EP-A-767 130, the first annular members are capable of expanding circumferentially upon inflation of the resilient envelope, and exerting a pressure on the inner surfaces of the cores onto which the cut reel sections are rewound, thus enabling the transmission of the rotary motion from the shaft to these latter.

However, the circumferential expansion of the first annular members does not ensure the secure axial locking of the cut reel sections. It is therefore necessary to put spacer elements between each adjacent pair of cut sections in order to prevent them slipping axially. However, the disposition of these spacers on the shaft introduces an additional processing phase into the production process, with associated costs and complications.

In order to overcome this disadvantage, the object of the present invention is a shaft of the type indicated above, characterised in that it includes a plurality of second annular members disposed along the body, coaxial with respect thereto and in a radially outer position with respect to the aforesaid first annular members, at least one seat being formed between at least one first and one second annular member, accommodating an engagement element capable of projecting radially from the outer surface of the second annular member upon relative rotation of the first annular member with respect to the second annular member, and of applying a localised pressure to the facing inner surface of one of the cores.

This localised pressure holds the cut section of the reel and the associated core to the underlying annular member, thereby avoiding relative slippage, both circumferentially and axially.

A further object of the present invention is a cutting and winding machine including at least one shaft of the type described above.

Further advantages and characteristics of the present invention will become clear from the following detailed description, given purely by way of non-limitative example and with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a cutting and winding machine including a pair of shafts according to the invention; Figure 2 is a side view of the machine of Figure 1; Figure 3 is a view in section of one of the shafts of the invention, taken on the line III-III of Figure 1; and Figure 4 is a view in section taken on the line IV-IV of Figure 3.

In Figures 1 and 2, the reference numeral 10 indicates a cutting and winding machine which is in itself known and only described in outline in this document.

The machine 10 comprises a support frame 12 to which is pivoted a first shaft 14 which is rotatable and capable of supporting a reel 16 of strip material to be unwound.

Also mounted on the frame 12 are a plurality of rollers 18 for guiding the strip 20 unwound from the reel 16, and a cutting shaft 22 which supports a plurality of longitudinally spaced cutters, not visible in the drawings, capable of cutting the strip 20 into several sections in a direction parallel to its length and perpendicular to the axes of the first shaft 14 and the guide rollers 18.

Finally, pivoted to the frame 12 is a pair of rewinding shafts 24 provided with means capable of causing the rotation thereof and on which are positioned longitudinally spaced tubular cores 26, usually formed from pressed cardboard. A respective section 28 of the cut strip is wound around each core 26, forming a reel the axial extent of which is less than that of the original reel 16.

Each rewinding shaft 24 comprises (Figures 3 and 4) a cylindrical body 30 having a plurality of equally circumferentially spaced cavities 32 on its outer surface, rectangular in section and extending at right angles and parallel to the axis 34 of the shaft 24.

Each cavity 32 accommodates a respective resilient envelope 36 connectable in a known way not illustrated in the drawings (for example, by means of ducts formed in the body 30) to a source of fluid under pressure, for example, compressed air.

A plurality of first annular members 38 is disposed coaxially along the body 30. Furthermore, a plurality of second annular members 40 is disposed along the body 30, coaxially with respect thereto and in a radially outer position with respect to the first annular members 38. Each second annular member 40 is disposed around a first annular member 38 such that the two associated annular members 38,40 are symmetrical with respect to a plane perpendicular to the axis 34 of the shaft 24.

Respective rolling element bearings 42, comprising an outer race 44 and an inner race 46 between which is interposed a ring of ball bearings 48, are interposed between axially adjacent pairs of associated first 38 and second 40 annular members.

Each second annular member 40 has a T-section with laterally projecting wings 50 that rest on the respective outer races 44 of the adjacent rolling element bearings 42.

Between each first annular member 38 and the associated second annular member 40 surrounding it is formed a plurality of circumferentially-spaced seats capable of accommodating an associated spherical engagement element 52 which, as will be explained in detail in the following description of the operation, is capable of projecting radially from the outer surface of the second annular member 40.

Each seat is formed by a radial hole 54 having a conical section formed in the second annular member 40, and a portion 56 cut along a chord of the outer circumference of the first annular member 38 and radially aligned with respect to the associated hole 54.

A tooth 58 protrudes radially outwardly from each first annular member 38 into a circumferentially-extending slot 60 formed in the second associated annular member 40.

Furthermore, a respective layer 62 of a friction material is disposed between each resilient envelope 36 and the facing inner surfaces of each first annular member 38.

In the operation of the machine 10 (Figures 1 and 2), the strip 20, which is slowly unwound from the reel 16, is cut into several sections perpendicular to the axis of the reel 16 by the cutters mounted on the shaft 22.

The cut sections 28 of the strip 20 then form reels having a reduced axial extent after being rewound on an associated core 26 positioned on one of the shafts 24 which are rotated about their own axes.

The cores 26 engage with the associated shaft 24 upon inflation of the envelopes 36, which causes a pressure to be exerted by the layers 62 against the inner surface of the first annular members 38 which are thus driven to rotate due to the friction with the body 30. Conversely, the second annular members 40 initially do not move, until the tooth 58 of the associated rotating first annular member 38 abuts against one of the lateral surfaces of the slot 60 formed in the second annular member 40. The tooth 58 and the associated slot 60 thus constitute means capable of limiting the relative rotation of the first annular member 38 with respect to the second annular member 40 that surrounds it.

This relative rotation-which can advantageously be of the order of approximately 15°-means that the spheres 52 are caused to project from the outside of the holes 54, since there is no longer a cut portion 56 (contrary to that illustrated in Figures 3 and 4) at their lower part along a chord of the outer circumference of the first annular member 38, but a completely curved portion.

The spheres 52-which are prevented from coming right out of the holes 54 by the conical shape of these latter-are thus capable of applying a localised pressure to the facing inner surface of the associated core 26, holding it to the underlying annular member 40, both axially and circumferentially.

In this way, the rotation of the body 30 of the shaft 24 is transmitted through the annular members 38,40 to the cores 26 around which the associated cut reel sections 28 start to wind.

For the correct performance of this operation, the tangential velocity, and thus the tension to which the various sections 28 are subjected, must at any moment be equal to an optimal value that is the same for all the sections 28.

The tangential velocity is given by the product of the angular velocity of rotation and the radius of the section 28 that is being wound. This latter value may, however, vary between the various cut sections 28, if the thickness of the material constituting the original reel 16 is not constant over the width of the strip, for example, due to manufacturing imperfections.

Therefore, in order to keep the tangential velocity of the various sections 28 constant, it is necessary to vary the respective angular velocity for each of these in such a way as to compensate for the variations in the radius caused by anomalous variations in the thickness of the material constituting the original reel 16.

Since the angular velocity of the shaft 24 is clearly the same for all of the cut sections 28, these latter must be able to slip circumferentially with respect to the shaft 24, independently of each other, to enable a variation in their angular velocity.

According to the invention, this slippage may take place between the body 30 of the shaft 24 and the surrounding first annular members 38, each of which, together with the associated second annular member 40, is connected to a single cut section 28. The body 24 and first annular members 38 are, in fact, held together only by the frictional forces exchanged with the layers 62, and not by projecting elements engaging an abutment surface.

Therefore, whenever an anomalous tangential velocity with a rewinding tension that is, for example, greater than the required value arises in a cut section 28, it is capable of overcoming the forces of friction arising between the body 30 and the first annular member 38 associated with this section 28. This therefore causes a relative slippage of the cut section 28 to which the annular members 38,40 are fixed with respect to the body 30, with a variation in its angular velocity such that the tangential velocity and, consequently, the rewinding tension assume the desired value.

In this way, the disadvantages arising from the rewinding of the sections 28 being too loose or too tight, which would be caused by incorrect rewinding tensions, are avoided.

By virtue of the roller bearings 42, present in the preferred embodiment of the present invention described above, the slippage of the first annular members 38 with respect to the body 30 of the shaft 24 can be controlled with extreme precision, which slippage depends upon the forces of friction exchanged with the layers 62.

In fact, since the weight of the cut sections 28 is supported almost entirely by the rolling element bearings 42, the value of the friction forces mentioned above depends substantially on the inflation pressure of the resilient envelopes 36.

Therefore, by acting on this variable, which can be controlled very accurately, it is possible to control the slip of the annular members 38 with respect to the body 30 of the shaft 24 and, consequently, the rewinding tension of the cut sections 28.

Naturally, the principle of the invention remaining the same, the details of construction and the embodiments may be widely varied with respect to that described and illustrated by way of example, without by this departing from its ambit of protection.

In particular, the axial extent of each second annular member 40, and thus the number thereof for a given shaft length 24, can be chosen bearing in mind that there must be at least one annular member 40 for each reel section 28. Obviously, the greater the number of annular members 40 chosen, the greater will be the flexibility of use of the shaft 24, enabling rewinding of a number corresponding at the limit to the number of cut sections 28.