FIELD OF THE INVENTION

5 The present invention relates to the technical sector relating to the bending of bands of metal sheet having an open ring shape, giving it a helical shape; the bands bent in this way can be assembled into multiple units such to obtain for example an Archimedes screw for transporting products or bolts for foundation piles.

10 In particular, the invention relates to a method for bending a band of sheet metal to give the band a helical shape and to an apparatus suitable for implementing this method.

DESCRIPTION OF THE PRIOR ART

An apparatus is well known for bending a band of metal sheet having a shape of 15 an open ring, designed to a helical shape to the bands. These bands usually have a circular development and are identifiable in an inner radius, an outer radius and a circular development sector; in other words, these bands are in the form of circular rings devoid of a circular sector having an angle of between ten and twenty degrees. The bands of sheet metal are flat and have to be bent to assume 20 a predetermined helical pitch. Once bent, the bands can be welded into multiple units to form helices of a desired length, and be used for example as Archimedes screws for conveying products; in particular, for simplifying the operations of welding it is important that the two ends of the band be bent parallel to one another and lie on a plane parallel to the axis of the helix.

25 Figure 1 illustrates a band of metal sheet which is flat and is shaped as an open ring; figure 2 shows the band of figure 1 after it has been bent to take on a helical shape.

The above-mentioned known apparatus comprises a first member having a first abutting surface which can restingly receive a band of sheet metal of the above- described type; the first abutting surface is flat and horizontal and abuts a first radial portion of the lower band.

A punch is also provided, which is vertically mobile such as to exert a pressure on the band resting on the first abutting surface and thus to bend the band itself. The punch is provided with a second abutting surface for abutting the band at a respective second radial portion of the upper band; the position of the punch with respect to the first member is such that if the projections of the first abutting surface and of the second abutting surface are considered with respect to a common horizontal plane, the angle which remains identified between these two projections is between five and ten degrees. As a consequence, the same angle is identifiable between the first radial portion and the second radial portion.

This means that when the punch descends, from top to bottom in order to bend the band, the second abutting surface is particularly close to the first abutting surface. The mutual proximity of the first abutting surface with respect to the second abutting surface is necessary in order to contain the consequent relative rotation of the band during the bending step (in fact, from a horizontal position the band would tend to rotate and then to assume a vertical position).

The second abutting surface has a guillotine shape and is inclined at a given angle with respect to a horizontal plane; the guillotine is necessary in order to give the band a helical shape: in fact, during the bending step the second abutting surface contacts the second radial portion progressively as the punch continues its downward stroke. As a result, a bending occurs, of the part of band between the first radial portion of the lower band and the second upper radial portion of band, such that the part of the band takes on a shape that is alike to a portion of helix.

To give the band a helical shape it is necessary to repeat the bending step described above several times, rotating the band each time by an angle equal to the angle between the first lower radial portion and the second upper radial portion above; the process ends when the band has been bent along its entire development and has thus taken on a helix shape. A disadvantage of this bending method consists in the fact that the above- described bending steps must be repeated many times (up to forty times), due to the fact that the angle between the first radial portion and the second radial portion is limited, as mentioned, to a value, for example, of between five and ten degrees.

By varying the inclination of the second surface with respect to a horizontal plane, the pitch of the spiral that is obtained is simultaneously varied; the orientation of the second surface, on the other hand, establishes the left-handed or right- handed helical turn of the band. Whenever it becomes necessary to change the pitch and/or shape, left or right, of the band that is to be obtained, the punch has to be replaced with one having suitable characteristics. This is particularly disadvantageous from the economic and practical point of view (storage and retrieval of the punches), as a considerable number of punches have to be available. SUMMARY OF THE INVENTION

In the light of the above, the aim of the present invention is to obviate the aforementioned drawbacks.

The above objects are obtained with a method for bending a band of sheet metal to give the band a helical shape, according to claim 1 , and with an apparatus that actuates this method, according to claim 6.

The above-mentioned method comprises steps of: supplying a band of sheet metal shaped as an open ring; abutting a first portion of the band with a first abutting surface; exerting a pressure on a radial second portion of the band, such that a part of the band comprised between the first portion and the radial second portion assumes a shape alike to a portion of helix. The step of abutting the first portion of the band comprises blocking the band. The pressure exerted on the second radial portion is obtained by: contacting the radial second portion of the band by means of a second abutting surface, and thereafter rotating the second abutting surface by a first angle and in a predetermined first direction such that the part of the band comprised between the first portion and the radial second portion assumes a shape alike to a portion of helix.

The second abutting surface contacts the second radial portion, preferably entirely; and thereafter the second abutting surface is rotated by a first angle and in a first direction, which determines a pressure on the second radial portion such as to cause a bending of the part of band comprised between the first portion and the second radial portion. The specific rotation of the second surface is chosen so that this bending enables the part of band to assume a shape similar to the above-mentioned portion of helix.

The fact of blocking the first portion of band enables a second radial portion to be chosen that is further away from the first portion with respect to the prior art, which advantageously enables imparting a helical path on the band, by performing a smaller number of operating bending steps; by way of example, with the present invention the angular distance between the first portion and the second radial portion can be about twenty degrees. Thus productivity can be considerably increased with respect to the prior art, as it significantly reduces the time required to obtain a band having a helical shape.

In addition, the pitch the bent band is to assume can be selected, simply by adjusting the angle by which the second abutting surface is rotated; this is extremely advantageous due to the fact that a member can be used which bears the second abutting surface, and the angular travel that the second abutting surface must pass through can be adjusted as required.

As the second abutting surface is opposite or aligned to the first abutting surface when the second abutting surface contacts the second radial portion, the band can be bent such as to confer a left-handed or right-handed direction to the band. In an embodiment, a fourth abutting surface can be provided that is opposite the second abutting surface; the fourth abutting surface can rotate through a second angle and in a second direction, opposite the first direction. In this way, according to production needs, the second abutting surface or the fourth abutting surface can be activated such as to obtain a band having a left-handed or right-handed helical shape. To this end, the second abutting surface and fourth abutting surface can be fashioned in an opening provided in a second member and can rotate the second member in one direction or the other according to production requirements.

The above-mentioned apparatus comprises: a first member having a first abutting surface for abutting a first portion of a band of metal sheet having an open ring shape; a second member having a second abutting surface for abutting the band, the second member being mobile with respect to the first member in order to abut, via the relative second abutting surface, a radial second portion of the band, and being dimensioned such as to exert a pressure, via the relative second abutting surface, on the radial second portion of the band such that a part of the band comprised between the first portion and the radial second portion assumes a form alike to a portion of helix; characterised in that it comprises blocking means of the first portion of the band, comprising the first abutting surface; and in that: the second member is activatable in rotation such that the second abutting surface can contact the radial second portion of the band when the second member is in a non-operating position and such that the second abutting surface subsequently rotates by a first angle and in a first direction such that the part of the band comprised between the first portion and the radial second portion assumes a form alike to a portion of helix.

The advantages of the apparatus actuating the above mentioned method have already been discussed above with reference to the method. BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the invention will be described later in the following description, in accordance with what is set out in the claims and with the aid of the appended tables of drawings, in which: figure 1 is a view from above of a band of sheet metal shape as an open ring, flat and exhibiting a circular shape; figure 2 is a perspective view of the band of figure 1 after it has been bent to assume a helical shape; figures 3A-3C are three perspective views of an apparatus according to the present invention; figures 4A, 4B are perspective views of the apparatus of figures 3A-3C which apparatus implements the method according to the present invention such as to obtain bands having a right-handed helical path; figures 5A, 5B are perspective views of the apparatus of figures 3A-3C which apparatus implements the method according to the present invention such as to obtain bands having a left-handed helical path.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, (10) denotes in its entirety an apparatus for bending a band of sheer metal such as to confer thereon a helical shape, object of the present invention, which apparatus actuates a bending method for conferring on the band a helical shape, also object of the present invention.

The apparatus (10) comprises: a first member (1) having a first abutting surface

(2) for abutting a first portion (3) of a band (4) of metal sheet having an open ring shape; a second member (5) having a second abutting surface (6) for abutting the band (4), the second member (5) being mobile with respect to the first member (1) in order to abut, via the relative second abutting surface (6), a radial second portion (19) of the band (4), and being dimensioned such as to exert a pressure, via the relative second abutting surface (6), on the radial second portion (19) of the band (4) such that a part of the band (4) comprised between the first portion

(3) and the radial second portion (19) assumes a form alike to a portion of helix; (figures 2, 4B, 5B); blocking means of the first portion (3) of the band (4), comprising the first abutting surface (2). The second member (5) is activatable in rotation such that the second abutting surface (6) can contact the radial second portion (19) of the band (4) when the second member (5) is in a non-operating position (A) (figures 3A-3C, 4A, 5A) and such that the second abutting surface (6) subsequently rotates by a first angle and in a first direction (D1) (figures 4B, 5B) such that the part of the band (4) comprised between the first portion (3) and the radial second portion (19) assumes a form alike to a portion of helix. The blocking means (7) are configured so that preferably the first portion (3) is radial. Preferably, the band (4) to be bent is flat (figure 1). The band (4) of figure 1 exhibits a circular shape, so that it is detectable by an inner radius, an outer radius and a sector having a circular development; the circular sector development can be, for example, to an amount of between three hundred and forty and three hundred and fifty degrees. The band (4) can also have an irregular shape, for example oval.

The blocking means (7) preferably include a third abutting surface (8); the first abutting surface (2) and the third abutting surface (8) are opposite and arranged with respect to one another such as to receive there-between the first portion (3) of band (4) and block it.

The distance between the first abutting surface (2) and the second abutting surface (6) is preferably such as to enable a blocking with clearance of the first portion (3) of band (4). In this way, the bending of the band (4) gives the band (4) itself a more regular and uniform helical shape. The first abutting surface (2) and the third abutting surface (8) are identifiable in an opening afforded in the first member (1).

The first member (1) is preferably solidly constrained to the frame (11) of the apparatus (10).

The first member (1) can comprise a disc centrally affording the first opening (9); the first opening (9) can be in the form of a slot open at one end; effectively it can have a stretched C-shape.

The second member (5) can comprise a disc centrally affording a second opening (21 ); the second opening (21 ) can have the shape of a slot open at one end, effectively an elongated C-shape. The apparatus (10) can comprise a support (12) for the second member (5), which for example in the accompanying figures has a half-moon shape and is fixed to the frame (11 ); the second member (5) is rotatable with respect to the support (12).

The apparatus (10) also comprises actuating means for rotating the second member (5). The actuating means can include: a hydraulic cylinder (13) having a jacket (14) thereof fixed to the frame (11) and the stem (15) which is articulated, at free end thereof, with a first arm (16) and a second arm (17) which are fixed to the second member (5). The first arm (16) is for example fixed, by an fastening lug (18), to the second member (5) at a first surface of the second member (5); the second arm (17) is for example fixed, by another fastening lug (18), to the second member (5) at a second surface of the second member (5) which is opposite the first surface.

Figures 4A and 5A are identical and show the second member (5) when in the inoperative position (A).

The lower surface and the upper surface of the first opening (9) of the first member (1 ) can be respectively termed the first abutting surface (2) and the third abutting surface (8).

In the inoperative position (A) the second abutting surface (6) can be referred to as the surface of the second opening (21) of the second member (5) which is parallel and aligned to the first abutting surface (2) of the first member (1 ).

The first abutting surface (2) and the third abutting surface (8) are preferably flat and parallel to a horizontal plane.

The second abutting surface (6) and the fourth abutting surface (20) are also preferably flat and parallel to a horizontal plane when the second member (5) is in the inoperative position (A). Consequently, the second abutting surface (6) and the fourth abutting surface (20) completely contact the second radial portion (19) of band (4) (respectively the lower and the upper portions).

Again with reference to figures 4A, 5A, the band (4) to be bent is arranged so that a first radial portion (3) of the band (4) is interposed between the first abutting surface (2) and the third abutting surface (8) of the first member (1) and so that a second radial portion (19) of the band (4) is interposed between the second abutting surface (6) and the fourth abutting surface (20). In particular, the first portion (3) radially of the band (4) is located at an end of the band (4). The bending of the part of band (4) between the first radial portion (3) and the second radial portion (19) is obtained, starting from the inoperative position (A) of the second member (5), by rotating the second member (5) thereof by a first angle and in a first direction (D1) (upwards-directed arrow in figure 4B) if the band (4) is to be given a right-handed helical shape, or by rotating the second member (5) by a second angle and in a second direction (D2) (downwards-directed arrow of figure 5B) if the band (4) is to be given a left-handed helical shape.

Once the bending of the part of band (4) comprised between the first radial portion (3) and the second radial portion (19) has been completed, the band (4) is rotated by an angle approximately equal to the angle between the first radial portion (3) and the second radial portion (19): in this way a further portion of flat band (4), adjacent to the previous portion, can be interposed between the first opening (9) and the second opening (21) respectively of the first member (1) and the second member (5).

The first member (1) and the second member (5) are preferably vertically orientated and arranged inclined to one another, the reciprocal arrangement thereof defines the angle by which the first radial portion (3) of the band (4) is inclined with respect to the second radial portion (19) of the band (4). For example, the angle is approximately twenty degrees; the angle is preferably between fifteen degrees and thirty degrees. Figures 4B, 5B illustrate the bending step of the last portion of flat band (4); as can be seen, the band (4) of figure 4B has now assumed a right-handed helical shape, while the band (4) of figure 5B has now assumed a helical left-handed shape.

In general terms, to obtain a right-handed helical path of the bent band (4) the second member (5) is provided only with the second abutting surface (6) (the one that has been taken to be the lower surface of the second opening of the second member 5), acting on the lower surface of the second radial portion (19) of band (4): in fact, the fourth abutting surface (20) does not intervene during the fixed bending steps (figures 4A, 4B). Similarly, to obtain a left-handed helical path of the bent band (4) the second member (5) is provided only with the fourth abutting surface (20) (the one that has been taken to be the upper surface of the second opening of the second member), acting on the upper surface of the second radial portion (19) of band (4): in fact, the second abutting surface (6) does not intervene during the fixed bending steps (figures 5A, 5B). The fact that the second member (5) is provided, in the embodiment illustrated in the figures, with a second opening (21) exhibiting both the second abutting surface (6) and the fourth abutting surface (20), gives the advantage that the apparatus (10) can be used to impart a right or left hand helical shape on the band. There exists no need for adjustments or changes of any kind on the apparatus (10) in order to select the type of performance to be obtained (right or left hand), but it is sufficient to rotate the second member (5) in the first direction (D1) (figure 4B) or in the second direction (D2 ) (figure 4B); this is extremely advantageous.

The above-described apparatus (10) more generally actuates a method, which is also object of the present invention, for bending a band (4) of sheet metal to impart a helical shape on the band (4).

The method comprises the steps of: supplying a band (4) of sheet metal shaped as an open ring; abutting a first portion (3) of the band (4) with a first abutting surface (2); exerting a pressure on a radial second portion (19) of the band (4), such that a part of the band (4) comprised between the first portion (3) and the radial second portion (19) assumes a shape alike to a portion of helix. The step of abutting the first portion (3) of the band (4) comprises blocking the band (4). The pressure exerted on the second radial portion (19) is obtained by: contacting the radial second portion (19) of the band (4) by means of a second abutting surface (6), and thereafter rotating the second abutting surface (6) by a first angle and in a predetermined first direction (D1) such that the part of the band (4) comprised between the first portion (3) and the radial second portion (19) assumes a shape alike to a portion of helix.

Depending on the direction (first direction D1 or second direction D2) in which the second abutting surface (6) is rotated, either a right-handed or left-handed helical shape can be obtained for the part of band (4). The blocking of the band (4) can be obtained by positioning the band (4) such that the first portion (3) thereof is interposed between the first abutting surface (2) and a third abutting surface (8).

The blocking can take place with a certain clearance, which can be determined by adjusting the mutual distance between the first abutting surface (2) and the third abutting surface (8).

The steps of blocking the band (4) at the first portion (3) and of exerting a pressure on the second radial portion (19) are preferably repeated on the other portions of the band (4) so as to cover the entire development of the band (4) and thus impart a helical shape to the band (4).

Preferably, the second abutting surface (6) entirely contacts the second radial portion (19) of band (4).

Other minor points of this method are deducible from the above description on the apparatus (10). It is understood that the foregoing has been described by way of non-limiting example, and that therefore constructional variants are possible, all falling within the protective scope of the present technical solution, as claimed in the following.