A cutting tool for disc-shaped metal sheets

Abstract: The invention finds application in the field of cutting tools, in particular for the cutting of disc-shaped metal sheets. More precisely, the invention relates to a disc-shaped tool (1) equipped with a knife with a circular cutting edge (4), having laterally two curved flanks (3). The knife (4) inserts itself into the width of a disc-shaped metal sheet (2), partially separating it into two sheets (5).

Description: The invention relates to a cutting tool for disc-shaped metal sheets. By metal sheets, partly-machined flat rolled steel sheets are intended, having one dimension much smaller than the other two; in other words, metal sheets which are thin but thick enough to be further reduced in width by subdivision into further sheets. The metal sheets specifically referred to are those having disc shape. The prior art embraces tools which are substantially disc-shaped, which narrow down in the proximity of the external perimeter which perimeter functions as a knife and wedge to penetrate into the width of the sheet in order to obtain a partial separation into two sheets, thus producing a "Y"-shaped conformation in which the "arms" of the letter "Y" represent the two separated sheets, while the "leg" represents the uncut sheet. Said tools are particularly applied in the making of pulleys since they can perform on a single metal sheet, thus avoiding the necessity of welding two distinct parts which together constitute the pulley. With regard to the making of pulleys, the prior art embraces both methods where a welding of two distinct parts is envisaged, and methods where the pulleys are realised from a single block of disc-shaped metal and using tools as described above. Said tools however have several drawbacks. Their maximum penetration depth is limited and rather modest. It has been found that the tool advancement towards depths superior to the thickness of the metal sheet happens with intolerable deviations from the original advancement plan, provoking deformations, ondulations and sometimes even complete breaking of the metal sheet. Aim of the present invention is to eliminate the above-described drawbacks and in particular to effect a cut into the width of a metal sheet which is without deviations from the advancement plan and which is able to reach greater depths with respect to those prior art tools. A further aim is to obtain savings in working costs, producing, for example, a pulley, in a shorter time. Said aims are fully attained by a cutting tool for disc-shaped metal sheets according to claim 1. The tool is disc-shaped and equipped with a circular perimetral knife to be inserted internally to the width of the sheet to be cut in order to obtain a partial separation or split into two sheets, wherein the knife or central cutting edge has laterally two curved flanks shaped so as to remain in contact with and to deviate, deform and "channel" according to their form, the two metal sheets produced by the cut. These and other characteristics will better emerge from the description that follows, of a preferred but not exclusive embodiment of the invention illustrated purely in the form of a non-limiting example in the accompanying figures, in which: Figures 1, 2 and 3 schematically and in several successive work phases illustrate the tool and the metal sheet and are partially sectioned according to a plane containing the rotation axis; Figure 4 illustrates in elevation a partly finished piece of work obtained by means of the use of the tool on a disc-shaped sheet. With reference to the figures, 1 indicates the cutting tool, particularly suitable for disc-shaped metal sheets. The tool 1 is also disc-shaped, equipped with a central knife or central cutting edge 4 arranged around the external perimeter of the disc and equipped laterally with two curved flanks 3. Said curved flanks 3 extend, in the illustrated embodiment, for an angle between 90° and 180° and can have an arc-shaped section, though not necessarily, inasmuch as their form depends substantially on the type of object to be created from the metal sheet, or more normally in this case a partly-worked piece, destined to be subjected to further working. Said curved flanks 3 are preferably identical between themselves and symmetrical with respect to the knife 1. The essential characteristics of the tool 1 are represented by the conformation of the curved flanks 3 which revolve about the axis of the tool 1 and have a profile, viewable in any axial section, constituted by a tract of curve that has its concavity turned towards the outside of the said tool 1. The tool 1 is particularly suitable for the production of pulleys, wheels or hub-caps of the single-piece type, starting with a single disc-shaped metal sheet 2. The disc-shaped metal sheet is placed in rotation by known means and is brought into contact with the tool 1, said tool 1 being freely rotatably mobile. While the metal sheet and the tool revolve, the tool 1 penetrates progressively into the width of the metal sheet 2, splitting it into two sheets 5, which are deviated to run along the curved flanks 3 and constrained to press forcibly against them so that said sheets 5 follow the said curved surfaces 3 round and thus assume the particular conformation, as illustrated in figures 2 and 3. In figure 4 a partly-worked piece 6, obtained in the above-described way, is illustrated: from this piece a pulley, a wheel or a hub-cap can be obtained by further working, all from the same single piece. The conformation of the tool, which, after the cutting zone of the knife 4 has been passed, forces the two sheets 5 to deviate, deform and follow the curved conformation of the curved flanks 3, guarantees great dynamic stability to the cutting operation and permits of the tool's 1 obtaining correct and centred radial penetrations and thus cuts which are very deep and qualitatively much superior to those attainable with the usual tools. An advantage provided by the invention is represented by the fact that with a second shaping of the sheets 5 single-sheet discs of various forms and dimensions can be realised.

Claims: Cutting tool for disc-shaped metal sheets, equipped with at least one knife having at least one central circular cutting edge (4) to be inserted internally to the width of a disc-shaped metal sheet (2) rotating about a first axis, to be cut in order to obtain a partial separation or split into two sheets (5), wherein said knife or cutting edge (4) laterally exhibits two curved flanks (3) characterised in that each flank having a U-shaped profile constituted by a curved section having its concavity turned towards the external surface of the tool (1); the two curved flanks (3) being shaped such as to remain in contact, to deviate, to deform and channel the two sheets (5) produced from cutting the metal sheet (2)in accordance with a shape of said flanks (3), and to bend said two separated sheets (5) back toward the rotating axis of said disc-shaped sheet (2) during the operation of said cutting tool. A tool as in claim 1, wherein the said curved flanks (3) revolve about the axis of the tool (1). A tool as in claim 1, wherein the curved flanks (3) are identical between themselves and symmetrical with respect to the knife or central cutting edge (4) of the tool (1). A tool as in claim 2, wherein the said tool (1) is rotatably free about its own axis.

Inventors: MAGNONI FRANCO, MAGNONI, FRANCO
Applicants: FATA EUROP GROUP, FATA EUROPEAN GROUP S.R.L.
Application year: 1991
Main classification: B21H1
IPC codes: B21H1