According to the prior art, the magnetic core laminations used in electric transformers are made by cutting a magnetic sheet iron in order to form laminations having particular geometrical shapes.

A typical 45° cutting pattern of a magnetic sheet iron, shown in figure 1, is obtained by cutting the magnetic sheet iron in two or more stations wherein each sector is cut-by a specific cutting station.

An aim of the present invention is to provide an improved apparatus, for cutting magnetic sheet iron for manufacturing magnetic core laminations.

An object of the invention is to provide an apparatus which is more compact than the machines conventionally used for cutting magnetic sheet iron into laminations.

A further object of the invention is to provide a reliable and economic apparatus, from the point of view of both the producer and the users.

The above aims and other aims and objects that will be more apparent hereinafter, are achieved by an apparatus for cutting magnetic sheet iron for manufacturing magnetic core laminations as claimed in the appended claims.

Further features and advantages of the invention will be more apparent by the following description of an embodiment of the invention, illustrated, by way of example in the enclosed drawings wherein FIG. 1 is a top plan view of a piece of magnetic sheet iron showing a cutting pattern; FIG. 2 is a top plan view of the apparatus, according to the invention, schematically illustrating the position of the four shears; Figs. 3-6 are top plan views of the apparatus schematically illustrating four cutting stages; FIG. 7 is a partial perspective view of the apparatus according to the invention; FIG. 8 is a top plan view of the shears of the apparatus according to the invention;

FIG. 9 is a side view of the apparatus according to the invention; FIG. 10 shows the two steps of cutting first with a perforating die and then with the two shears, according to the invention.

With reference to the above figures, the apparatus according to the invention, globally designated by the reference numeral 1, comprises a frame 2 supporting a substantially square die 3 having posts 4 each supporting a mould 5 arranged at right angles one between the other.

Each mould 5 bears a respective blade 6 and constitutes a shear member adapted to cut a magnetic sheet iron 7 upon actuation by a respective actuator 8, for example an hydraulic actuator.

The apparatus is provided with four shear members respectively designated by the numerals 10,11, 12, and 13, arranged at right angles one with respect to the next.

The apparatus also comprises a perforating die 9 arranged along the center line of the magnetic sheet iron and adapted to make a hole 14 in a point of the magnetic sheet iron which corresponds to the intersection of the axes of the shear members.

The perforating die 9 may have a round shape, as illustrated in figures 3-6 and 10 or a cross shape, as illustrated in figure 2.

Figure 1 shows the pattern into which the magnetic sheet iron 7 is to be cut in order to obtain three different laminations respectively designated by the reference signs L1, L2 and L3.

A magnetic sheet iron, which is generally in the form of a reel or spool, is fed into the apparatus and its motion is electronically controlled in order to synchronize it with the operation of the shear means, in the following manner.

The first lamination L1 is obtained by cutting the sheet iron 7 with shear members 10 and 12, that cut along the line 15 of L1, and shear members 11 and 13, that cut along the line 16 of L1, as illustrated in figures 3 and 4.

Lamination L2 is obtained by cutting along the lines 15 and 16, as in L1, and by also cutting along the L-shaped line 17 with shear members 11 and 12, as illustrated in FIG. 5.

Lamination L3 is obtained by cutting the sheet iron 7 along the L-shaped lines 18

and 19 using all four shear members 10,11, 12 and 13, as illustrated in FIG. 6.

A critical point is generated at the intersection 20 of the cutting lines and the shear members may not cut the sheet iron perfectly in that point.

For that reason, the apparatus is provided with the perforating die 9 which bores the hole 14 in the sheet iron exactly at the intersection 20 of the cutting lines. The hole 14 may be circular and have a diameter of, for example 8 to 10 mm, or may also be in the shape of a cross or quadrangular.

Preferably, the hole 14 is bored into the sheet iron before the cutting operation.

The apparatus according to the invention allows to manufacture magnetic core laminations from a spool of magnetic sheet iron, in one single cutting station.

The apparatus according to the invention may have numerous modifications and variations, within the scope of the appended claims. All the details may be substituted with technically equivalent elements and the materials employed, as well as the dimensions, may be any according to the specific needs and the state of the art.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.