Patent Description:
In particular, the present invention intends to solve some problems inherent to the limits of integral "T" tools or even those made in several assembled parts, since it is envisaged that said tool is made by combining a tool body made of cheap metal material, since the hardness of the metal is not necessary in this portion, and a head made of material of high quality and hardness, and that the tool thus made comprises suitable channels for the passage of cooling water delivered through the head, ultimately obtaining an extremely performing and cost-effective tool.

The present invention is advantageously applied in the field of milling tools, in particular tools of the "T" type, used for machining materials and in particular for creating grooves on workpiece holder tables or the like.

As disclosed in <CIT>, <CIT> and <CIT>, the use of various types of tools which are generally applied on machines for milling or turning products is known.

The tools allow milling or turning operations of products and in some cases there are special tools adapted to make so-called "T-slots", or slots made along parallel longitudinal lines within products such as workpiece holder tables or the like, or tables or base plates, movable or fixed, of many workstations on which the workpieces are fixed by vices.

Therefore, typically, for a slot with the characteristic dimensions shown below, the sequence of operations, with reference to <FIG>, is as follows:.

The problem encountered in actuating this technology is that of finding the best compromise between maximum cost reduction and the highest production efficiency.

Integral tools with a head of diam. ΦM and shank ΦG made in a single piece, all of the same material, if produced with low-cost material such as steel (or HSS) allow very slow machining with high cutting edge wear, while high-performance carbide (or cobalt alloy and tungsten carbide) tools have excellent performance but high costs.

Furthermore, the adoption of a single body for the head and shank requires the creation of a roughly shaped object in a single material, produced with high material removal and high machining costs. Therefore, to carry out quite simple operations which, however, require the creation of undercuts, it is possible to use tools which are either poor, as they are extremely cheap, or performant but very expensive.

All this requires considerable investments in the tools used or in the workmanship by the operators who must also replace any damaged tools, using prolonged execution times both during the machining of the tools and during the machining of the product to be treated, with all the considerable costs which derive therefrom.

In some cases, tools have been made by combining two or more products, for example flat hot-brazed cutting edges, which allow to obtain a body in different materials, but with strong limitations on the cutting geometry, mainly linked to the impossibility of performing a number of cutting edges and helix angles and cutting of any kind and shape, therefore made with an unsatisfactory technology for this specific type of product.

According to some solutions, a "T" type cutting element comprises a cutting head of cylindrical conformation having a cavity of substantially cylindrical conformation, an elongated shank coaxially aligned with the head with an annular space defined between the cavity of the cutting head and a portion of the shank extending therein, such cavity being filled by injection with molten metal.

This technology is not suitable for making grooves which envisage high material removals, since the joint between the head and the shank has a precarious tightness because the joining surfaces are reduced.

It has further been found that the "T" cutting tools known in the art are subject to rapid wear due to the severity of the machining, with a high removal of material in the execution of the "T" slots which subjects the tool to high mechanical and thermal stresses due to the friction between the cutting edges and the piece of hard material to be incised, with the production of high chip volumes.

The overheating of the tool represents a rather significant problem, as it affects the deterioration of the tool which can in a short time progressively lose the integrity of the cutting edges, with all the negative consequences which derive therefrom.

The possibility of bringing pressurised fluid in an optimal manner in the machining area, i.e., from inside the tool, is currently limited to integral tools or with hot-brazed cutting edges in the form of flat shaped plates (with the above limitations) while there are no known solutions applied to hot-brazed tools and internal supply of refrigerant with any number and geometry of cutting edges.

The present invention aims to provide a tool for milling products in hard materials, such as metal or stone material, in particular tools of the "T" type in several assembled products, also comprising cooling means by lubricating-refrigerant fluid, i.e., capable of eliminating or at least reducing the drawbacks highlighted above.

The invention aims in particular to provide a tool of the "T" type for milling hard materials made in two parts with not necessarily the same materials and provided with channels for the passage of refrigerant liquid which is directly supplied into the machining area through the tool itself.

According to the invention, it is envisaged that the body or shank of the cutter, consisting of a substantially cylindrical shaft in which a coaxial inner channel is made connected to the end of the shank with a possible plurality of radially arranged grooves or holes, is inserted into at least one coaxial slot made on the inner side of a head provided with radial holes placed in alignment with said radially arranged holes of the shank. The hot-brazing between the shank and the head occurs after the interposition of hot-brazing material placed between the end of the shank and the bottom of the seat of the head, so that the channels for the refrigerant liquid are perfectly aligned.

This is obtained by means of a tool for milling products in hard material according to claim <NUM> and a manufacturing method thereof according to claim <NUM>.

The dependent claims of the present solution outline advantageous embodiments of the invention.

The invention aims in particular to provide a tool of the "T" type for milling metal materials or the like which envisages creating a body, or shank, made of a generally different material with respect to the head, or in any case consisting of a separate product from the head and which must be assembled therewith by hot-brazing and which at the same time allows a flow of lubricating-refrigerant fluid inside the tool itself.

The presence of passages inside the tool for the passage of fluid and hot-brazed areas makes it necessary to design a specific head coupling area so that, during the hot-brazing, the filler material, once it has reached the liquid state, does not flow inside the inner passages, obstructing them after solidification.

Other features and advantages of the invention will become apparent from reading the following description of an embodiment of the invention provided by way of nonlimiting example, with the aid of the figures illustrated in the appended tables of drawings, in which:.

Referring to the appended figures, and initially in particular to <FIG>, the reference numeral <NUM> generally indicates a tool for milling products in hard materials, such as metal or stone material, in particular a tool of the "T" type, consisting of a body or shank <NUM> and a cutting head <NUM>.

In particular, the tool consists of a cylindrical or generally axial-symmetrical shank <NUM>, and a head <NUM> which is initially rough with a substantially discoidal shape, where the head <NUM> and the shank <NUM> are of different materials, or in any case are initially separate objects. The initially rough head <NUM> becomes the sharp head, comprising the cutting edges, after the sharpening process.

According to a first embodiment depicted in <FIG>, the rough head <NUM>, which in the images is depicted before the sharpening adapted to form the cutting edges, has a cylindrical edge <NUM> and two circular surfaces <NUM> and <NUM> which form two opposite faces, a front and a rear.

In the head <NUM>, inside one of the two circular surfaces <NUM> and <NUM>, a first substantially circular slot <NUM> is obtained, arranged with the main axis thereof parallel to the rotation axis of the tool.

In turn, inside the first slot <NUM> a second slot <NUM> is also obtained, also substantially circular, concentric and arranged coaxially to the main slot <NUM>, where the second slot <NUM> is smaller than the first slot <NUM>.

The shank <NUM>, as illustrated in <FIG>, comprises an end <NUM> from which an appendage <NUM> extends, where the end <NUM> and the appendage <NUM> are configured for their coupling with the head <NUM> at the slots <NUM> and <NUM>, respectively, with the aim of adding, in addition to fixing by hot-brazing as we will see below, also a further mechanical fixing action obtained by coupling between sections, even non-circular, or possibly by interposing auxiliary fixing elements of circular or prismatic section, with any number of sides.

In this regard, the end <NUM> of the shank <NUM>, adapted to couple with the head <NUM>, has a section such as to fit precisely into the first slot <NUM> of the head <NUM>, and the appendage <NUM> has a section such as to fit precisely into the corresponding slot <NUM> of the head <NUM> itself.

The shape of the slots <NUM> and <NUM>, as well as the respective ends <NUM> and appendage <NUM> of the shank, are circular or prismatic with any number of sides, which can be flat, concave or convex.

According to the embodiment depicted in <FIG> and <FIG>, it is envisaged that both the end <NUM> and the appendage <NUM> of the shank <NUM> and the slots <NUM> and <NUM> of the head <NUM> are provided with anti-rotation recesses <NUM>' and <NUM>", respectively, to which fixing pins <NUM> are associated configured to prevent the relative rotation of the shank <NUM> and the head <NUM>.

According to an embodiment of the invention, the shank <NUM>, moreover, is provided with a central channel <NUM> parallel and coaxial to the outer cylindrical surface, and, in this embodiment, with radially arranged lateral holes <NUM>, placed in a first case on the appendage <NUM> of the shank itself, as depicted in <FIG> and <FIG> and in a second case on the end <NUM> of the shank <NUM>, as depicted in <FIG> and <FIG>.

According to a further embodiment, the shank <NUM> is provided with the central channel <NUM> parallel and coaxial to the outer cylindrical surface, but without radially arranged lateral holes <NUM>, as we will see in detail below.

In turn, the head <NUM> is also provided with respective radially arranged holes <NUM> orthogonal with respect to the axis of the head itself, which coincides with the axis of the shank <NUM>.

In a first case the radial holes <NUM>, as depicted in <FIG> and <FIG>, are arranged starting from the cylindrical edge <NUM> of the head <NUM> to open internally at the annular edge of the second slot <NUM>, while in a second case the radial holes <NUM>, as depicted in <FIG> and <FIG>, are still arranged starting from the cylindrical edge <NUM> of the head <NUM> to open internally at the annular edge of said first slot <NUM>. Where the holes <NUM> and <NUM> are made in an advanced position, as depicted in <FIG> and 8a, the holes <NUM> can be replaced by open front grooves placed on the end face of the appendage <NUM> of the shank <NUM>.

The radial holes <NUM> made in the head <NUM> are placed in alignment with the radially arranged lateral holes <NUM> placed in a first case on the appendage <NUM> of the same shank and in a second case on the end <NUM> of the shank <NUM>, so that the joint of the end of the shank <NUM> with the slots <NUM> and <NUM> of the head <NUM> causes the formation of a through connection for refrigerant fluid from the central channel <NUM> of the shank at the exit towards the outside of the radial holes <NUM>, at the material machining area.

According to the embodiment depicted in <FIG>, which envisages that the shank <NUM> is provided with the central channel <NUM> parallel and coaxial to the outer cylindrical surface, but without radially arranged lateral holes <NUM>, the end <NUM> of the shank <NUM> penetrates into the first slot <NUM> while the appendage <NUM> is configured to penetrate only partially into the second slot <NUM>, so as to allow the connection between the channel <NUM> of the refrigerant fluid, which opens at the centre of the appendage <NUM>, and the radial holes <NUM> through the pre-chamber formed by the same slot <NUM> which is created between the end of the shank and the head.

The different embodiments of the tool are depicted in <FIG> illustrating sectional views of the tool according to the invention with the shank separated from the head, and in <FIG> illustrating sectional views of the tool according to the invention in its embodiments in joined mode with the shank inserted and fixed in the head.

From an operational point of view, it is envisaged that, for the fixing by hot-brazing of the end of the shank inside the slots <NUM> and <NUM>, welding material <NUM> is used which is placed in the slots <NUM> or <NUM> based on the advanced or retracted positioning of the appendage <NUM> of the shank <NUM> or on the end <NUM> of the shank itself.

According to a first embodiment depicted in <FIG> and <FIG>, when the lateral holes <NUM> of the shank <NUM> are placed in an advanced position on the end of the appendage <NUM>, and possibly on the front face of the same appendage <NUM>, to coincide with the radial holes <NUM> placed at the second slot <NUM> of the head <NUM>, the welding material <NUM> is placed on the bottom of the first slot <NUM>, while when the lateral holes <NUM> are placed on the end <NUM> of the shank <NUM> to coincide with the radial holes <NUM> placed at the first slot <NUM>, the welding material is placed on the bottom of the second slot <NUM>.

The passages of any lateral holes <NUM>, present only in some embodiments, and radial holes <NUM> are therefore configured to prevent the mutual connections from closing in the hot-brazing step, since the welding material could fill them with molten alloy which solidifying, would plug them. Therefore, it is necessary to envisage an axial misalignment, hence the two proposed sections, which ultimately allow to keep the passages from the alloy "distanced".

The mechanical coupling between the head and the shank is configured to confer both the maximum strength to the brazed joint and to ensure the radial alignment of the passages.

Such combinations of shank and head configuration allow the permanent passage of internal lubricant-refrigerant fluid near the area subject to hot-brazing.

The final sharpening of the tool, occurring starting from a rough head <NUM> of cylindrical shape, allows to obtain any cutting geometry, in particular any number of cutting edges and values of helix angles and cutting angles, as in the example depiction of <FIG>.

It should be noted that, according to a preferred embodiment, all the holes and/or the inner cooling passages are made before the brazing, both on the shank and on the head; therefore, after brazing the tool is ready for sharpening.

Depending on whether the holes are on the end <NUM> or on the appendage <NUM>, the shape of the brazing area or the gap which the alloy must fill changes. The correct choice of coupling tolerances must ensure that the alloy fills all and only the areas to be filled.

The mechanical coupling (regardless of the section) can be made by means of not totally circular sections (therefore with some flat faces) or with the insertion of fixing pins <NUM>, as depicted in <FIG>. For these pins <NUM>, special housings <NUM>' are arranged placed on the head and shank, or enlargements/narrowings of the circular sections of the same shape as the pins (which will be cylindrical or prismatic with any number of sides).

In the case of a particular shape of the head, these narrowings could also be incorporated into the shape of the slots <NUM> and <NUM>, as depicted in <FIG>, thus making the use of additional pins unnecessary in such a case.

As depicted in <FIG>, the joining between the body or shank <NUM> of the tool and the cutting head <NUM> of a milling tool of the "T" type, occurs by inserting welding material <NUM> in the slots <NUM> and/or <NUM>, and subsequently also inserting the end <NUM> and the appendage <NUM> of the shank <NUM> in the same slots <NUM> and <NUM> of the head <NUM>.

During the melting, the welding material <NUM>, initially resting on the bottom of at least one of the slots <NUM> or <NUM>, also fills the entire "gap" between the shank and the slots, creating a very large and solid tightness surface.

According to the embodiment depicted in <FIG>, the sealing area made by brazing the welding material <NUM> is highlighted.

The depth of insertion of the end <NUM> and the appendage <NUM> into the slots <NUM> and <NUM> is calculated in relation to the diameter of the channel itself.

For example, by way of illustration, the ratio between the insertion depth and the diameter of the shank is greater than or equal to <NUM>, or <NUM>%.

The shank can however have, in areas not affected by the joining with the head <NUM> in the slots <NUM> and <NUM>, even different diameters.

The steps which, according to the invention, allow to obtain the milling tool are defined in claim <NUM>.

As mentioned, the joint between the two materials forming the shank <NUM> and the head <NUM> of the tool <NUM> allows the maximum reliability and performance of the tool and at the same time a reduction in the production and consequent marketing costs, making the tool potentially very attractive on the market.

Claim 1:
A tool (<NUM>) of the "T" type used for milling metal products or other hard materials, such as for making grooves with undercuts on a workpiece holder or the like, said tool comprising:
- a substantially axially symmetric shank (<NUM>) comprising an end (<NUM>) thereof provided with an appendage (<NUM>);
- a head (<NUM>) separated from said shank (<NUM>) and joinable therewith, of substantially cylindrical or trunco-conical discoidal conformation having a greater diameter than said shank (<NUM>) and delimited by two opposite faces (<NUM>, <NUM>) of which the face (<NUM>) facing said shank (<NUM>) comprises a first slot (<NUM>), arranged with the main axis thereof parallel to the rotation axis of the tool, inside which a second slot (<NUM>) which is concentric and arranged coaxially to the main slot (<NUM>) is also obtained, where the second slot (<NUM>) is smaller than the first slot (<NUM>);
wherein said shank (<NUM>) is provided with at least one central longitudinal channel (<NUM>), and in that said head (<NUM>) is provided with holes (<NUM>) arranged radially and communicating with said central channel (<NUM>), so that the mutual connection between the shank (<NUM>) and the head (<NUM>) causes a passage of refrigerant fluid introduced from the base of the shank and delivered by the radial holes (<NUM>) of the head (<NUM>); characterised in that the end (<NUM>) of the shank (<NUM>) and/or its appendage (<NUM>) are provided with radially arranged lateral holes and/or grooves (<NUM>) placed in connection with the radial holes (<NUM>) of the head (<NUM>);
wherein the end (<NUM>) of the shank (<NUM>) is fixed to the inside of the slots (<NUM>, <NUM>) by welding material (<NUM>) which is placed in the slots (<NUM>, <NUM>) based on the positioning of the lateral holes and/or grooves (<NUM>) on the end of the appendage (<NUM>) of the shank (<NUM>) or on the end (<NUM>) of the shank itself;
wherein, when the lateral holes (<NUM>) of the shank (<NUM>) are placed in an advanced position on the end of the appendage (<NUM>) to coincide with the radial holes (<NUM>) placed at the second slot (<NUM>) of the head (<NUM>), the welding material (<NUM>) is placed on the bottom of the first slot (<NUM>);
and wherein, when the lateral holes (<NUM>) are placed on the end (<NUM>) of the shank (<NUM>) to coincide with the radial holes (<NUM>) placed at the first slot (<NUM>), the welding material is placed on the bottom of the second slot (<NUM>).