The present invention relates to a multiaxis milling machine, particularly a milling machine for use in dentistry.

In the reference technical field, multiaxis mills are known which are adapted to perform chip-forming machining processes on “blanks” (sometimes referenced in the technical sector also as“wafers” because of their disk-like shape), usually metal disks, which once arranged on the worktable are subjected to chip-forming machining until the parts of interest (for example, abutments or parts of dental prostheses) are provided.

In order to reduce the intervention of the operator and render the milling machine capable of providing complex three-dimensional geometries, over time milling machines, especially those in dentistry, have evolved progressively, to the point of machining on a plurality of axes with evolved numeric control.

The milling machines to which one will refer hereinafter are those with multiple axes, particularly with five axes.

One drawback of these machines is linked to the arrangement of the blank on the worktable: from the manual placement of the least advanced milling machines there has been a gradual transition to automated placement, for example by means of dedicated handling devices or by means of a robotic arm.

As regards dedicated handling devices, they require providing on the milling machine motors, joints, sensors and kinematic chains specifically designed only for the handling of the blank: obviously this increases undesirably the complexity and the costs of the milling machine.

As regards instead solutions with an anthropomorphic robotic arm, first of all its positional calibration must be extremely precise; obviously, an incorrect positioning of the blank could in fact entail incorrect machining or a halting of the machine with the consequent need for human intervention. Secondly, mills provided with an anthropomorphic robotic arm are not only relatively expensive but also bulky, so that often it is difficult to arrange them in working environments of small size.

Yet another drawback involved in these evolved dental milling machines with robotic arm is related to the fact that said arm has to be suitably protected against the machining dust that is created during milling, which might jeopardize the good operation of the delicate robotic arm or require in any case a suitable protection thereof.

The aim of the present invention is to provide a multiaxis milling machine that solves the technical problem cited above, obviates the drawbacks and overcomes the limitations of the background art, allowing to have available a milling machine that is fast, precise and relatively cheap.

Within this aim, an object of the present invention is to provide a multiaxis milling machine, preferably a multiaxis milling machine usable in dentistry, in which the handling of the blank from the magazine to the working area is automated so as to not require the use and the provision of a robotic arm or of dedicated handling devices.

A further object of the invention is to provide such a milling machine that is capable of giving the greatest assurances of reliability and safety in use.

This aim and these and other objects that will become better apparent hereinafter are achieved by a multiaxis milling machine comprising:

- a workpiece holder assembly adapted to support a worktable for at least one blank being machined

- a working assembly, comprising a working head which comprises a spindle of a milling machine which is adapted to receive a tool

wherein the workpiece holder assembly and the working assembly can move with respect to each other with a plurality of degrees of freedom

- at least one blank magazine, in which

the blank magazine accommodates a plurality of worktables, the workpiece holder assembly comprises couplings for supporting the worktable in a releasable manner, and

the working head comprises grip devices for gripping a worktable from the blank magazine and transporting it from and toward the workpiece holder assembly and for the engagement/release of the worktable with respect to the couplings.

The use of the workpiece holder head for moving the blanks mounted on the worktables from the magazine to the working area allows in fact to overcome the limitations of the solutions known in the background art.

In fact, with respect to known machines provided with dedicated handling devices, in the solution according to the invention it is not necessary to increase the complexity of the construction, since the motors and the kinematic systems for handling the blanks mounted on the worktables are the same ones used for the working head.

With respect, instead, to known machines provided with a robotic arm, the solution proposed here allows to eliminate the drawbacks linked thereto while maintaining a good work efficiency of the milling machine and a high precision.

Further characteristics and advantages will become better apparent from the description of a preferred but not exclusive embodiment of a milling machine according to the invention, illustrated by way of non limiting example with the aid of the accompanying drawings, wherein:

Figure 1 is a top view of an example of a milling machine according to the invention;

Figure 2 is a side view of the milling machine of Figure 1;

Figure 3 is a front view of the milling machine of Figure 1;

Figure 4 is a perspective view of the milling machine of Figure 1;

Figures 5-9 are various perspective views of enlarged-scale details of the milling machine of Figure 1.

With reference to the accompanying figures, an embodiment of the invention is described therein and in the description in which the multiaxis milling machine 1 is a dental milling machine, designed to provide parts of dental prostheses starting from a so-called blank or disk-like wafer G (metallic or made of resin) that is worked by chip-forming machining.

The multiaxis milling machine 1 comprises a workpiece holder assembly 2 adapted to support a worktable 21 for at least one blank G being machined, while the working assembly 3 comprises a working head 31 which in turn comprises a spindle 32 of a milling machine which is adapted to receive a tool.

The workpiece holder assembly 2 and the working assembly 3 can move with respect to each other with a plurality of degrees of freedom.

The milling machine 1 furthermore comprises at least one blank magazine 4, preferably on board the machine.

The blank magazine 4 accommodates a plurality of worktables 21. Characteristically, according to the invention, the workpiece holder assembly 2 comprises couplings 22 in order to support the worktable 21 in a releasable manner.

It should be noted, in this context, that the worktable 21 is an operating component of the machine 1, in that it is coupled directly to the couplings 22 which are, as will be noted also hereinafter, rotatable and motorized, so as to impose on the worktable 21 a rotary motion about the axis A.

The coupling between the couplings 22 and the worktable 21 is provided preferably by means of shape interlocks, so as to ensure a precision of one hundredth of a millimeter.

The blanks G, during working, remain stably coupled to the worktable 21, which is moved synchronously with the working head so as to provide a rotation about the axis A, which is strictly part of the working axes of the machine 1.

The blanks G to be machined are coupled stably to the worktable 21 , for example, in the case shown in the figures, by means of crescent-like fixing elements.

The working head 31 comprises instead grip devices 5 for gripping a worktable 21 from the blank magazine 4 and conveying it from and toward the workpiece holder assembly 2 and for engaging/releasing the worktable 21 with respect to the couplings 22.

The milling machine 1 is, in particular, a milling machine with five axes X, Y, Z, A, B shown in the drawings; each axis corresponds to one degree of freedom that exists between the working head 3 and the worktable 21 on which the blank G being worked is mounted during the machining process.

In greater detail, the directions X, Y, Z are mutually perpendicular, in order to define a Cartesian triplet, along which the head 3 and the worktable 21 (in the assembled condition) can move with respect to each other: in the embodiment shown, along the directions X and Z there are two linear guides (for example tracks) along which the whole working assembly 3, which comprises the working head 31, moves; along the direction Y there is another linear guide (for example a track) along which the whole workpiece holder assembly 2, which comprises the worktable 21, moves linearly.

The axis A is instead a circular trajectory along which the worktable

21 moves rotationally about its own longitudinal axis, moved by the motorized couplings 22, while the axis B is a circular trajectory along which the working head 31 moves rotationally so as to make the spindle 32 rotate correspondingly.

In order to perform the movements along the axes X, Y, Z, A, B there are, besides the guides, which are linear or circular according to the cases, dedicated motor and transmission means, which are not described in detail here because they are generally known to the person skilled in the art and not the subject matter of the invention.

Going back to the milling machine 1, it comprises, in the illustrated example, two magazines 4 for the blanks G, a horizontal one and a vertical one.

Each magazine 4 can be fixed with respect to the workpiece holder and/or working assemblies or movable together with one of them, being coupled thereto and being moved along the axes X, Y, Z, A, B with the same motor means, transmission and guides.

In the illustrated example, in fact, the blanks G are coupled in pairs to a same worktable 21, which, in the working condition, is mounted on the supports 29 of the workpiece holder assembly 2.

Specifically, each worktable 21 comprises a plate-like support, which comprises in turn two substantially semicircular flared regions, in which two blanks G are accommodated mutually side by side, fixed in a stable manner to said worktable 21.

The substantially semicircular flared regions allow machining of the blanks G on the two opposite main faces without having to remove them and reposition them; as mentioned, in fact during the machining process the blanks remain fixed directly (without the interposition of pallets or intermediate part supports or others) to the worktable 21, which, moved by the motorized couplings 22 to which it is coupled directly (without the interposition of any other element), allows to machine the blanks G on the two faces and according to the milling trajectories necessary to provide the finished parts.

The worktable 21 comprises moreover two engagement shanks 25 which mate with corresponding motorized rotatable couplings 22, so that in the working condition the worktable 21 is conveyed to the couplings 22 and brings to machining the blanks G mounted thereon; once machining is finished, the worktable 21 that supports the machined blanks is placed in the magazine and then a new worktable, with two blanks G not yet machined and coupled to the couplings 22, is picked up.

The couplings 22 can rotate about the axis A and the rotation is imparted by a motor means (for example electric or pneumatic); the engagement shanks 25 transmit the rotary motion from the rotatable motorized couplings 22 to the worktable 21 so that the blanks G are rotated in a corresponding manner about the axis A.

When the worktable 21 has a substantially rectangular shape in plan view, the engagement shanks 25 are arranged on two opposite sides, preferably, as in the case shown, at the shorter sides of the rectangle, so as to reduce the moment of inertia during rotation about the axis A.

The worktable 21, which is removable from said workpiece holder assembly 2, allows to not move the blanks G alone and allows greater machining precision.

Moving on to describe the grip devices 5, they, in a fully general way, can be magnetic, mechanical, hydraulic or pneumatic.

In the shown non-limiting example, the grip devices 5 are of the magnetic type and preferably comprise two magnets, preferably electromagnets, which can be activated selectively when they have to grip magnetically the worktable 21, to move it to the workpiece holder assembly 2 and insert it in the couplings 22 or vice versa if the machining of the blanks G is finished.

As mentioned in other embodiments, the grip devices comprise grip elements, such as for example with a clamp (actuated mechanically, hydraulically or pneumatically), which provide an actual grip of the worktable 21.

Moreover, in other embodiments, the grip elements comprise (only or in combination with the clamp elements) a pin which is accommodated in a seat of the worktable 21 (or vice versa), to perform a mechanical coupling, although not by gripping, as in the case of the clamps.

In practice, during operation, when a machining process has to be started on a new blank G, the working head 31 moves until it reaches a pick- up position proximate to a worktable 21 accommodated in a magazine 4. Then the grip devices 5 are activated and grip the worktable 21 and convey it from the magazine 4 to the workpiece holder assembly 2, using in practice the same motor means, guides and transmissions that move the working head 31 and the spindle 32 during the machining process. In other words, according to the invention, at least some of the motor means for the actuation of the working head 31 coincide with the motor means for the movement of the worktable 21 in said conveyance from and towards the workpiece holder assembly 2, and therefore motor means dedicated to the handling of the worktable that holds the blanks to be machined are not necessary. At this point, the working head 31 mates the worktable 21 with the couplings 22.

As regards the worktable 21, in the preferred and shown solution it comprises a ferromagnetic coupling element 28, which is adapted to cooperate with the magnetic grip devices 5.

Said magnetic grip devices are provided preferably as two grip devices 5 (clearly visible also in Figure 9), which are mounted in the portion of the working head 31 directly above (in the assembled condition) the spindle 32, and each has an L-like overall shape, with the magnetic grip end of one directed towards the one of the other.

As regards the coupling element 28 of the worktable 21, it has a shape that is substantially similar to that of the magnetic grip end of the grip devices 5, which in the provided example is circular.

In order to facilitate a correct placement of the worktable 21 on the couplings 22 it is possible to provide teeth and mechanical coupling seats by interference on both, so that if the worktable 21 should move (for example, rotate) during conveyance from the magazine to the workpiece holder assembly, the presence of teeth and seats ensures that once the worktable 21 has been mated to the couplings 22 it is in a preset and stable position.

The operation of the milling machine is clear and evident from what has been described. In practice it has been found that the milling machine, according to the present invention, achieves the intended aim and objects, since it allows to avoid the drawbacks linked to the presence of the robotic arm and to provide a milling machine that is at the same time relatively less expensive, stronger, more reliable and less bulky, besides being more efficient.

The milling machine thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept.

All the details may furthermore be replaced with other technically equivalent elements.

In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements.

The disclosures in Italian Patent Application no. 102018000006939, from which this application claims priority, are incorporated by reference.

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 interpretation of each element identified by way of example by such reference signs.