Drilling tool for making an undercut and drilling method for making an undercut

Abstract

A drilling tool for making an undercut within a solid material comprises a shaft extending along a longitudinal axis between a proximal end and a distal end, a gripping portion located at the proximal end, a gripping portion located at the distal end, comprising a blade having a helical course around the longitudinal axis, and a mechanical stop, arranged along the longitudinal extension of the shaft, adapted to create mechanical interference with an outer surface of the solid material so as to interrupt the translational advancement of the tool within the solid material. The shaft has at least a first diameter extending at least from the end portion to the mechanical stop.

Description

[0001] DRILLING TOOL FOR MAKING AN UNDERCUT AND DRILLING METHOD FOR MAKING AN UNDERCUT

[0002] DESCRIPTION

[0003] TECHNICAL FIELD

[0004] The present invention relates to a drilling tool for making an undercut. In detail, the present invention finds particular application in all those fields where it is necessary to drill a solid material in order to create a cavity, inside of which it is necessary to insert devices, such as anchoring devices or the like.

[0005] This invention is used in any technical field for the drilling of a solid material, inside which it is necessary to insert a device that must remain in situ. In particular, the present invention is used in any technical field where it is necessary to drill a material for the insertion of a device and to ensure better retention of the device within the material.

[0006] Purely by way of example, one technical field in which the present invention may be applied is, for example, that of bone drilling surgery, for the application of small implants, such as expansion anchors for the attachment of sutures.

[0007] However, this does not exclude other technical fields such as woodworking, metalworking, construction or others that require the insertion of an element such as a dowel, pin or other body, which then generally expands to bind itself by frictional interference within the cavity. The present invention also relates to a drilling method for making an undercut in a solid material.

[0008] PRIOR ART

[0009] To drill a solid material, drills or milling cutters are used to create a cavity with an entry hole of the same cross-sectional dimension as the cavity itself. This transverse dimension of the cavity and the entry hole is the same as the maximum diameter of the head of the drill or milling cutter, i.e. the maximum diameter of the cutting or drilling profile.

[0010] If a retaining element such as a dowel, pin or anchoring device is to be inserted into the cavity, what prevents the retaining element from slipping out and disengaging from the cavity is only the mechanical interference created by friction between the retaining element and the cavity walls of the solid material. In general, these retaining elements expand to increase pressure and friction against the walls, so as to exert an appropriate retaining force.

[0011] The applicant noted that the grip and engagement between the retaining element and the cavity could be improved.

[0012] In fact, the applicant found that frictional interference alone may not guarantee an optimal and permanent seal between the retaining element and the inner walls of the solid material.

[0013] The applicant noted that this could be improved by using not only mechanical interference but also shape interference.

[0014] Specifically, considering that these retaining devices are inserted inside the cavity and then expand, the Applicant has perceived that by obstructing, at least partially, the entry / exit hole, the retaining element remains firmly constrained inside the cavity.

[0015] The applicant therefore found that making an undercut could provide the necessary shape interference to keep the element in situ within the cavity and prevent it from slipping out.

[0016] At present, there are no known tools or devices capable of making undercuts in a solid material. In fact, as mentioned above, when a hole is drilled in any solid material and with any tool, an entry hole is obtained with a diameter equal to the maximum diameter of the drilling profile, so that the maximum diameter of the internal cavity coincides with the diameter of the hole.

[0017] Purely by way of example, in operations on bones where it is necessary to anchor devices, small tools with very fine drill bits are used to make small cylindrical holes in the bone. Small expansion devices are then inserted which, by friction, anchor themselves inside the cavity in the bone itself.

[0018] The method currently used consists of drilling small holes with a drill-like tool.

[0019] The tools used allow for the creation of simple cylindrical holes with a constant diameter or with a simple conical profile. Although functional, these tools can be improved to allow, for example, the creation of cavities with special geometries or that provide a better grip for the devices inserted inside.

[0020] The purpose of the present invention is to propose a drilling tool for making an undercut in a solid material that improves the prior art and provides a solution that has so far not been foreseen or solved in any way by currently known and used drilling tools.

[0021] Specifically, the present invention proposes a drilling tool for creating an undercut that allows a cavity to be made with an undercut of grip / interference.

[0022] The present invention also proposes a drilling tool for making an undercut within a solid material in such a way as to allow not only frictional but also shape interference between the solid material and a device that can be inserted into the cavity.

[0023] A further purpose of the present invention is to present a drilling method for making an undercut within a solid material that provides the possibility of making a cavity, even a very small one, within the solid material with an undercut.

[0024] These and other purposes are achieved by a drilling tool for making an undercut within a solid material and a drilling method for making an undercut within a solid material in accordance with one or more of the appended claims.

[0025] SUMMARY A first aspect of the present invention is a drilling tool for making an undercut within a solid material.

[0026] Such a drilling tool preferably comprises a shaft extending along a longitudinal axis between a proximal end and a distal end, a gripping portion located at the proximal end, an end portion, located at the distal end, comprising a central shaft and a blade, extending radially from the central shaft; the blade has a cutting edge profile with a helical course around the longitudinal axis. The tool further comprises a mechanical stop, arranged along the longitudinal extension of the shaft, adapted to create mechanical interference with an outer surface of the solid material so as to interrupt the translational advancement of the tool within the solid material. Advantageously, the shaft has at least a first diameter extending from the end portion to the mechanical stop.

[0027] Preferably, the blade has an outer diameter greater than the first diameter of the shaft, such that the ratio between the outer diameter of the blade and the first diameter of the shaft is comprised between 1 mm and 6 mm. Advantageously, the blade comprises a plurality of ridges, each having a predefined thickness and a pitch between two consecutive ridges. The pitch is dimensionally related to both the thickness of the ridges and a maximum length of the end portion such that the pitch is comprised between twice the thickness of the ridge and half the maximum length of the end portion.

[0028] Each ridge comprises a predefined thickness comprised between 0.01 mm and 2 mm, preferably between 0.01 mm and 0.5 mm.

[0029] The pitch between two consecutive ridges is preferably comprised between 1 mm and 2 mm.

[0030] The outer diameter of said blade can have either a constant geometry profile or a variable geometry profile. The variable geometry profile varies between a minimum and a maximum diameter.

[0031] In addition, each ridge has a solid angle at the tip having an amplitude comprised between 2° and 90°, preferably between 20° and 45°. The central shaft of the end portion has an outer diameter such that the dimensional ratio between the first diameter of the shaft and the outer diameter of the central shaft of the end portion is comprised between 0.5 and 2.9, preferably between 0.5 and 1 .5.

[0032] Advantageously, the outer diameter of the central shaft of the end portion has a dimension greater than or equal to the dimension of the first diameter of said shaft, such that the dimensional ratio between the first diameter of the shaft and the outer diameter of the central shaft of the end portion is greater than 0.5 and less than or equal to 1 .

[0033] The central shaft of the end portion has an outer diameter such that the ratio of the outer diameter of the blade to the outer diameter of the central shaft of the end portion is comprised between 1 .01 and 3.

[0034] The blade has a working surface with radial extension to the longitudinal axis, projecting from the first diameter of the shaft.

[0035] Advantageously, the radial extension of the working surface of the blade is constant along the longitudinal axis for at least 80% of the longitudinal length of the blade.

[0036] Alternatively, the radial extension of the working surface of the blade can also advantageously vary along the entire longitudinal length of the blade or for a substantial part of it. Purely by way of non-limiting example, the working surface of the blade can have a constant radial extension for a portion ranging from 5% to 90%, preferably 25% to 75%. However, different values of radial extension of the working surface of the blade are permissible and do not depart from the scope of protection of the present invention.

[0037] The mechanical stop is defined by a predetermined portion, along the shaft, having a transverse dimension with respect to the longitudinal axis greater than the first diameter of the shaft.

[0038] Advantageously, the mechanical stop is defined by a change in diameter of the shaft itself, at a predetermined portion along the longitudinal extension of the shaft. Thus, the shaft has a second diameter greater than the first diameter; the first diameter extends from the end portion to the mechanical stop, while the second diameter extends from the mechanical stop to the gripping portion.

[0039] In an alternative configuration, the mechanical stop is defined by an abutment element, which is associated with the shaft at a predetermined portion along the longitudinal extension of the shaft; the abutment element advantageously has a larger transverse dimension with respect to the longitudinal axis than the first diameter of the shaft.

[0040] Advantageously, the abutment element is part of an additional element that can be associated with the shaft; the relative position between the shaft and the additional element can be defined and fixed by means of a positioning system that locks the relative sliding between the shaft and the additional element.

[0041] The proximal end of the shaft is configured to connect to an electric actuator to promote rotation of the shaft about the longitudinal axis. The shaft can also be operated manually, without the need for an electric actuator.

[0042] Preferably, the end portion is made as a single piece with the shaft.

[0043] Alternatively, the end portion is removable from the shaft and interchangeable with other end portions having different geometries.

[0044] A second aspect of the present invention is a drilling method for making an undercut within a solid material.

[0045] The method comprises the steps of: preparing a drilling tool for making undercuts in accordance with the above. Advancing the tool and thus the shaft with rototranslational motion along a longitudinal axis in such a way that the blade of the end portion pierces the solid material entering completely inside it.

[0046] Advancing the tool and thus the shaft with rototranslational motion along the longitudinal axis until a mechanical stop is brought into abutment against an outer surface of the solid material when the blade is completely inside the solid material and a proximal end of the blade is placed below the outer surface of the solid material at a distance comprised at least between 0.5 mm and 100 mm.

[0047] Continuing with the rotation only of the tool for a number of rotations such as to create a cavity completely internal to the solid material, partially closed by an edge or shoulder of solid material defining an undercut with a thickness comprised at least between 0.5 mm and 100 mm.

[0048] Activating a reverse rotation of the tool to extract the blade.

[0049] Remove the tool and the end portion from the solid material in such a way that the edge has a central hole, which places the internal cavity in fluid communication with the outside, having a diameter equal to the first diameter of the shaft and smaller than the largest diameter of the blade. The method involves creating an internal cavity with a blind bottom, when the mechanical stop is in abutment against the outer surface of the solid material. This cavity has a larger diameter equal to the largest diameter of the radial extension of the blade.

[0050] The cavity also has an internal geometry equal to the involute of the outer profile of the blade.

[0051] BRIEF DESCRIPTION OF THE DRAWINGS

[0052] A drilling tool for making an undercut within a solid material as described and claimed is illustrated in the following figures, which are for illustrative and non-exhaustive purposes, wherein:

[0053] - Figure 1 is a side view of the drilling tool in accordance with the present invention;

[0054] - Figure 2 is a side view of the drilling tool in Figure 1 , associated with a handle element, in accordance with the present invention;

[0055] - Figure 3 is a side view of an embodiment variant of the drilling tool in Figure 1 , associated with a handle element, in accordance with the present invention; - Figures 4 to 7 are some enlarged views of the end portions of the drilling tool of the present invention, according to various exemplary and non-exhaustive embodiments;

[0056] - Figure 8 is a side view of the drilling tool shown in Figure 2, associated with an electric actuator;

[0057] - Figure 9 is a side view of the drilling tool shown in Figure 3, associated with an electric actuator;

[0058] - Figure 10 depicts the steps in the drilling method covered by the present invention.

[0059] DESCRIPTION

[0060] With reference to the accompanying figures, 1 denotes a drilling tool in accordance with the present invention.

[0061] In particular, the present invention relates to a drilling tool for making an undercut within a solid material.

[0062] Specifically, the drilling tool that is the subject of the present invention makes it possible to make a cavity with an undercut, specifically an undercut positioned at the entrance hole in that cavity. In other words, the drilling tool which is the subject of the present invention makes it possible to make a cavity that is not completely open, but such that it presents a partial closure of the incoming hole; in this way, the perforated side of access to the cavity presents a narrowing that makes it possible to make an undercut or a shoulder that mechanically interferes, by shape interference, with any element inserted inside. This prevents or makes it more difficult for the inserted element to escape.

[0063] In the remainder of this description, reference will be made to the terms proximal and distal, with explicit reference to the hand of the user: “proximal” therefore means the portion, the end or the part of the tool or component most proximal to, and therefore nearest to, the user holding the tool, while “distal” means the portion, the end or the part of the tool or component most distal, and therefore furthest from the body, from the hand of the user holding the tool.

[0064] The drilling tool 1 is a tool that can make a cavity within a solid material and simultaneously create an undercut within the cavity.

[0065] This is made possible by a careful combination of geometric parameters that allow the tool, which is the subject of the present invention, to make an undercut below the outer surface of the solid material into which the tool enters, making the cavity. These geometric parameters will be presented in the course of this description.

[0066] This tool 1 , in accordance with the present invention, comprises a shaft 2 extending along a longitudinal axis X, between a proximal end 2p and a distal end 2d. Advantageously, the longitudinal axis X is straight.

[0067] The tool 1 also has a gripping portion 3 located at the proximal end 2p of the shaft 2.

[0068] As shown in Figure 1 , the gripping portion 3 can be an integral part of the shaft 2, close to the proximal portion 2p, or, as shown in Figure 2, it can be an additional gripping element 12 that can be rigidly connected to the shaft 2 to facilitate gripping.

[0069] In this configuration, this handle 12 also serves for the manual movement of the tool and placing it in rototranslation.

[0070] Near the distal end 2d, the tool 1 has an end portion 4 comprising a blade 5 with a cutting profile with a helical course around the longitudinal axis X.

[0071] The end portion 4 has a central shaft 4s, a natural continuation of the shaft 2, from which the blade 5 extends radially.

[0072] The blade 5 is, therefore, a spiral winding around the central shaft 4s. The end portion 4 has the same extension as the extension of the blade 5. Alternatively, the end portion 4 can be seen as a threaded portion, whose cutting thread is defined by the blade 5.

[0073] The end portion 4 comprises a free end 4d having a tip and resulting, therefore, advantageously tapered outwards to facilitate drilling and insertion of the blade 5 through the solid material M. The end portion 4 has a length h2 comprised between 2 mm and 50 mm, preferably between 10 mm and 40 mm, even more preferably between 10 and 20 mm.

[0074] A mechanical stop 6 is arranged along the longitudinal extension of the shaft 2; this mechanical stop 6 is configured to create mechanical interference with an outer surface S of the solid material M within which a cavity with an undercut is to be made.

[0075] The mechanical stop 6, by abutting against the outer surface S of the solid material M, prevents the tool from translating further and advancing by screwing itself into the material as it continues its rotation about the longitudinal axis X (Figure 10 - B).

[0076] In this way, the relative position between drilling tool 1 and solid material M is maintained, along the longitudinal direction I coinciding with the extension of the longitudinal axis X (Figure 10).

[0077] Alternatively, the mechanical stop could be replaced with an electronic stop, implemented by robotic motorisation of the shaft itself, thus capable of stopping the advancement of the shaft at the desired predetermined and programmed position.

[0078] The portion 21 of shaft 2 extending from its distal end 2d to the mechanical stop 6 has a length hi having an extension comprised between 1 mm and 400 mm, preferably between 10 mm and 50 mm, even more preferably between 20 mm and 30 mm.

[0079] Advantageously, the shaft 2 has at least a first diameter D1 extending at least from the end portion 4 to the mechanical stop 6, then from the distal end 2d of the shaft to the mechanical stop 6. In particular, the shaft 2 may have a constant diameter.

[0080] The central shaft 4s of the end portion 4, extending for the entire winding of the blade 5, has an outer diameter D1 ’.

[0081] In an embodiment, the outer diameter DT of the central shaft 4s is equal to the diameter D1 of the shaft 2.

[0082] The geometric ratio between D1 and DT can vary between 0.5 and 2.9, preferably between 0.5 and 1 .5.

[0083] In a preferred configuration, however, the first diameter D1 of shaft 2 is less than or equal to the outer diameter D1 ’ of the central shaft 4s of the end portion 4. Therefore, in a preferred configuration, the ratio between D1 and D1 ’ is less than or equal to 1 .

[0084] Preferably, the shaft 2 also has at least a second diameter D2 extending from the mechanical stop 6 to the gripping portion 3.

[0085] Advantageously, the first diameter D1 is smaller than the second diameter D2. In an alternative configuration, not illustrated, the first diameter D1 can be the same size as the second diameter D2.

[0086] The blade 5 of the end portion 4 has a working surface 7 extending radially with respect to the longitudinal axis X. In other words, the blade 5 is projecting with respect to the first diameter D1 of the shaft 2, transversely to the longitudinal axis X. Therefore, the blade 5 has an outer diameter D3 greater than the first diameter D1 of the shaft. Preferably, the ratio of the outer diameter D3 of the blade 5 to the first diameter D1 of the shaft 2 is comprised between 1 mm and 6 mm, more preferably between 1 .01 mm and 3 mm, even more preferably between 1 .5 mm and 2 mm.

[0087] Furthermore, the ratio of the outer diameter D3 of the blade 5 to the outer diameter DT of the central shaft 4s of the end portion 4, thus the ratio of the maximum overall diameter of the end portion 4 to the minimum overall diameter of the end portion 4, is comprised between 1 .01 and 3, preferably between 1 .5 and 2.5, even more preferably between 1 .5 and 2.

[0088] The outer profile of the blade 5, which has a helical course, can have a constant or variable geometry, as shown by way of non-exhaustive example in Figures 4-7. In other words, the blade may have a constant diameter along the longitudinal axis X for at least 80% of the longitudinal length of the blade 5 itself. In this way, the involute of the outer profile of the blade 5 is essentially a cylinder (Figure 4).

[0089] Alternatively, as illustrated in Figures 6 and 7, which represent only two exemplary forms without wishing to exclude other possible geometries, the blade 5 may have a working surface 7 having a radial extension of variable amplitude along the longitudinal axis X. In other words, the outer diameter D3 of the blade 5 may not be constant but vary between a minimum D3’ and a maximum D” along the longitudinal axis X, Thus, the involute of the outer profile of the blade 5 has drop, cone, truncated cone, spherical, wave, cylindrical, sawtooth or other possible geometries.

[0090] Therefore, in this case, if the geometric profile of the blade 5 varies between a maximum D” and a minimum D3’, the ratio between the outer diameter of the blade 5 and the first diameter D1 of the shaft 2 is defined between the maximum diameter D” of the blade and the diameter D1 of the shaft.

[0091] Similarly, if the geometric profile of the blade 5 varies between a maximum D3” and a minimum D3’, the ratio of the outer diameter of the blade 5 to the outer diameter DT of the central shaft 4s of the end portion 4 is defined between the maximum diameter D” of the blade and the outer diameter D1 ’ of the central shaft 4s.

[0092] The geometry of the extension of the blade 5 determines the geometry of the cavity that is made within the solid material, as will be further described below.

[0093] In particular, the solid angle a of the thread of the blade 5 preferably has an amplitude comprised between 2° and 90°, more preferably between 10° and 60°, even more preferably between 20° and 45°. In other words, this angle is the solid angle, at the tip, of each ridge 50 defining the blade 5, i.e. the angle delimited by the sloping outer walls of the blade's thread and defining the steep sides of each ridge 50.

[0094] Preferably, the thickness CT, measured at the tip, of each of the ridges 50 defining the blade 5 is comprised between 0.01 mm and 2 mm, even more preferably comprised between 0.01 mm and 0.5 mm.

[0095] Advantageously, the pitch p between two consecutive ridges 50 of the blade 5 is preferably between twice the thickness CT of each ridge and half the length h2 of the end portion 4, thus of the length of the blade 5. Therefore, the pitch is preferably 2*CT < p < h2 / 2. A preferred value of the pitch can be, for example, comprised between 0.5 mm and 3 mm, preferably between 1 mm and 2 mm, even more preferably between 1.5 mm and 2 mm.

[0096] This range makes it possible to ensure, on the one hand, that not too much material is removed inside the hole created in the threaded section, and on the other hand, that there is a minimum number of revolutions in the threaded section. The correct dimensioning and the dimensional relationship between the pitch and the thickness of the ridge are important in order to obtain a tool capable of removing a sufficient portion of the internal solid material M to create the undercut through the outer surface S of the solid material M while avoiding the breakage of the outer surface S. This creates an entry hole through the outer surface S that is only as wide as the diameter D1 of the shaft 2, a cavity inside the solid material M and an undercut below the outer surface S, as will be explained below.

[0097] As mentioned above, the tool 1 comprises a mechanical stop 6 which is preferably made by a diameter variation along the shaft 2.

[0098] In particular, the mechanical stop 6 is defined at a predetermined portion along the longitudinal extension of the shaft 2 and may be made either as a variation in diameter of the shaft 2 itself (Figures 1 , 2, 4, 6-8) or as an additional element 8, associated with the shaft 2, which has a transverse dimension, with respect to the longitudinal axis X, greater than the first diameter D1 of the shaft 2 (Figures 3, 5, 9).

[0099] A first embodiment of the mechanical stop 6 (Figures 1 , 2, 4, 6-8) is, therefore, that it is made by a change in the diameter of the shaft 2 itself. At the mechanical stop 6, therefore, there may be a change in diameter of the shaft itself 2 such that, when considering travelling along the shaft from the gripping portion 3 to the end portion 4, the shaft 2 changes diameter, reducing from the second diameter D2 greater than the first diameter D1 which is smaller (Figures 1 and 2).

[0100] An alternative configuration (Figures 3, 5, 9) may provide for an additional element 8 which can be associated with said shaft 2; this additional element 8 is configured in such a way as to make an abutment element 13 acting as a mechanical stop 6, which can be located at a predetermined portion along the longitudinal extension of the rod. This abutment element has a transverse dimension D4, measured orthogonally with respect to the longitudinal axis X, which is greater than the first diameter D1 of the shaft 2.

[0101] In order to position the shaft 2 correctly with respect to the additional element 8, a positioning system 81 (visible in Figure 3) can be provided, alternatively positioned on the shaft 2 or the additional element 8, which creates a mechanical interference by preventing further relative movement between the shaft 2 and the additional element 8. The positioning system 81 therefore locks the shaft 2 in the correct and desired position with respect to the additional element 8, so that the abutment element 13 acting as a mechanical stop 6 is positioned at the correct desired distance from the end portion 4.

[0102] In the configuration involving the shaft 2 in association with the additional element 8, the shaft 2 can have a constant diameter, i.e. present a first diameter D1 having the same size as the second diameter D2. This is possible because, with an outer element acting as a mechanical stop 6, the change of diameter is no longer essential. It is not excluded, however, that even in this configuration the shaft may have a change in diameter.

[0103] In detail, the alternative configuration is illustrated in Figure 3: the shaft 2 can be associated with a cannulated device 11 , such as a guide (aimer), which acts as the additional element 8. In particular, this device 11 has a sleeve 9 in the shape of a cannula, inside which said shaft 2 can be axially inserted.

[0104] The sleeve 9 has an axial length less than the length of the shaft 2, so that when the shaft is inserted into it and the two components are correctly coupled in the operating position, a distal edge 9d of the sleeve 9 is positioned at the predetermined portion of the mechanical stop 6. In this way, the distal edge 9d of the sleeve 9 acts as an abutment element 13 and, therefore, as a mechanical stop 6.

[0105] The distal edge 9d therefore has a transverse dimension (i.e. diameter) D4 greater than the first diameter D1 of the shaft 2.

[0106] Advantageously, the cannulated device 11 may also include a handle element 12 from which the sleeve 9 extends.

[0107] In this configuration, the gripping element 12 defines the gripping portion 3.

[0108] Preferably, the end portion 4 is made as a single piece with the shaft 2.

[0109] However, a configuration in which the end portion 4 is removable from the shaft and interchangeable with another end portion 4 carrying a blade 5 having a different geometry can also be envisaged.

[0110] Advantageously, the proximal end 2p of the shaft 2 is configured to be connected to an electric actuator 10 which promotes rotation of the shaft 2 about the longitudinal axis X. The electric actuator 10 is thus able to place the shaft in rotation about its longitudinal axis X, thereby causing the rotation of the end portion 4 and, consequently, the blade 5.

[0111] In use, the drilling tool 1 according to the present invention is used to make an undercut within a solid material.

[0112] In other words, the drilling tool 1 described here makes it possible to create a cavity, within a solid material, which is partially open at the top. This means that the transverse dimension, i.e. the diameter, of the entry hole through the solid material is smaller than the actual transverse dimension of the internal cavity C, thus always measured along the same direction orthogonal to the drilling direction.

[0113] In fact, the cavity C has a diameter equal to the diameter D3 of the drilling blade 5.

[0114] With the use of the drilling tool 1 in question, the cavity is delimited at the top (or at least at the perforation side) by a perforated wall or perforated shim, which thus creates an undercut, i.e. an edge 20 with a shoulder, with the inside of the cavity itself. Therefore, at the top, the cavity presents an edge 20 or shoulder projecting radially inwards and centrally perforated. In other words, the side walls of the cavity do not run into the ground but are interrupted against the aforementioned perforated wall or shim placed above and partially closing the cavity.

[0115] This shoulder can be particularly useful when it is necessary to insert a body into the cavity C and also have an element that creates mechanical interference.

[0116] Figure 10 schematically illustrates the steps involved in the drilling method for making an undercut within a solid material.

[0117] Figure 10 is divided into three main steps A, B and C.

[0118] Step A is the advancing and drilling of the solid material.

[0119] The following steps are therefore envisaged: preparing a drilling tool for making undercuts in accordance with what is described, advancing the tool 1 , in particular the shaft 2 along the longitudinal axis X (first frame of step A illustrated in Figure 10), with rototranslational motion, so that the blade 5 of the end portion 4 penetrates the solid material M entering completely inside it. The entry of the end portion 4 and the blade 5 takes place along a helical path traced by the winding, around the axis X, of the blade 5 itself. The entry hole that is created has a diameter equal to the first diameter D1 of the shaft 2, from which the working surface 7 of the blade 5 radially projects in a helical course. The outer surface S and the solid material M are then perforated by a helical path with a transverse extension equal to the maximum diameter of the blade D3 (or D3”). It should be noted that through the rototranslational entry, the blade advances through the material along a helical channel with an extension equal to the transverse extension D3 of the blade 5, but does not create a hole of equal size. The central hole that is formed has a size equal to the first diameter D1 of the shaft because, being full, it necessarily occupies that space which is subtracted from the solid material.

[0120] Continuing, the method involves advancing the tool 1 , and thus the shaft 2, with rototranslational motion along the longitudinal axis X (as shown in the second and third frames of step A, which show two different moments of first drilling of the tool 1 within the solid material) until the mechanical stop 6 is brought in abutment against an outer surface S of the solid material (fourth frame of step A).

[0121] This occurs when the blade 5 is completely inside the solid material and a proximal end 5p of the blade 5 is placed below the outer surface S at a distance with a thickness d comprised at least between 0.5 mm and 100 mm.

[0122] Then, the rototranslation continues until the stop element 6 comes into abutment against the outer surface S of the solid material M. In Figure 10, translation is indicated by the arrow I, rotation by the arrow Ri.

[0123] From this moment, we move on to the second step or step B of Figure 10: the method then involves the step of continuing with only the rotation of the tool 2, keeping the relative axial position between the tool and the outer surface S stable and firm thanks to the support of the stop element 6 against the latter.

[0124] Rotation Ri alone continues for a number of rotations such as to make a cavity C completely inside the solid material.

[0125] In fact, the mechanical stop 6 acts as an abutment by pressing against the outer surface S of the solid material from above and from the outside and counteracts the translational movement of the tool; this prevents the further screwing of the drilling tool inside the material from dragging the whole tool downwards, inside the material: if this were the case, i.e. if rotation were continued without having an element that also prevents the simultaneous translation of the tool, only a helical path would be created within the material (as a result of the screwing of the tool into the solid material) and not a cavity with an undercut.

[0126] Then, by keeping the tool stationary in translation, thus preventing it from translating further along the axis X, while continuing to rotate it about the longitudinal axis X, the blade 5 still rotating at the same height along the longitudinal axis X, digs laterally, removing the solid material and forming a cavity.

[0127] Since at the entrance hole there is only the shaft 2 and in particular the part of the shaft having a diameter equal to the smallest or first diameter D1 , while the blade 5 having a transverse extension D3 greater than the first diameter D1 turns completely below the outer surface S, distanced from the latter by at least a thickness d, thus creating a shoulder having a transverse extension e, measured from the side wall of the cavity C to the central edge b of the shoulder 20 itself, equal to half the difference between the diameters D3 and D1 , thus equal to half the difference between the diameter D3 of the blade 5 and the first diameter D1 of the blade 2.

[0128] Once the cavity C has been created and the undercut d outlined, the drilling tool 1 must be removed, taking care not to enlarge the entrance hole by breaking the undercut.

[0129] In the third step C, therefore, the two steps of extracting the tool are illustrated.

[0130] In this step the method involves activating a reverse rotation Ro of the tool to extract the blade 5.

[0131] Translation always occurs along the longitudinal axis X but in the opposite direction, indicated by the arrow O, while rotation occurs in the opposite direction, indicated by the arrow Ro.

[0132] It is possible to retrace the same route as the outward path or create a new one. As the blade passes through the thickness d with a rototranslational motion, at most a second helical trajectory will be created that neither interferes with the first nor causes the thickness d to break. Obviously, the axial dimension of the thickness d must be appropriately calibrated depending on the difference between the diameter D3 of the blade 5 and the first diameter D1 of the shaft 2, the hardness of the solid material, the quality of the material and the loads applied to the body inserted into the cavity.

[0133] Finally, removing the drilling tool and the end portion 4 with the entire blade 5 from the solid material, so that the thickness d made through the surface and a first part of the solid material presents a central hole, which places the internal cavity in fluid communication with the outside, having a diameter equal to the first diameter D1 of the shaft 2 and smaller than the largest diameter D3 (or D3”) of the blade 5.

[0134] The cavity C is thus at least partially enclosed by an edge or shoulder 20 of solid material defining an undercut with a thickness comprised at least between 0.5 mm and 100 mm.

[0135] When the mechanical stop 6 is in abutment against the outer surface S of the solid material, the internal cavity C created is blind and has a larger diameter equal to the largest diameter D3 of the radial extension of the blade 5. The cavity C, made by the fixed-pitch rotation of the blade inside the axis X, has a geometry equal to the involute of the outer profile of the blade 5.

Claims

CLAIMS1 . Drilling tool for making an undercut within a solid material comprising:- a shaft (2) extending along a longitudinal axis (X) between a proximal end (2p) and a distal end (2d),- a gripping portion (3) located at said proximal end (2p),- an end portion (4), located close to said distal end (2d), comprising a central shaft (4s) and a blade (5), extending radially from said central shaft (4s), having a cutting profile with a helical course around said longitudinal axis (X),- and a mechanical stop (6), arranged along the longitudinal extension of said shaft (2), adapted to create mechanical interference with an outer surface (S) of said solid material (M) so as to interrupt the translational advancement of said tool (1 ) within said solid material; said shaft (2) having at least a first diameter (D1 ) extending at least from said end portion (4) to said mechanical stop (6); said blade (5) having an outside diameter (D3, D3”) greater than the first diameter (D1 ) of the shaft (2) such that the ratio between the outside diameter (D3, D3”) of the blade (5) and the first diameter (D1 ) of the shaft (2) is comprised between 1 mm and 6 mm.

2. Tool according to the preceding claim, wherein said blade (5) comprises a plurality of ridges (50), each having a predetermined thickness (CT) and a pitch (p) between two consecutive ridges (50); said pitch (p) being dimensionally related to the thickness (CT) of said ridges and a maximum length (h2) of said end portion (4) such that said pitch is comprised between twice the thickness (CT) of the ridge and half the maximum length (h2) of the end portion (4).

3. Tool according to claim 1 , wherein the outer diameter (D3) of said blade (5) may have either a constant geometry profile or a variable geometry profile; said variable geometry profile varying between aminimum diameter (D3’) and a maximum diameter (D3”).

4. Tool according to one of the preceding claims, wherein said blade (5) comprises a plurality of ridges (50), each ridge (50) having a solid angle (a) at the tip having an amplitude comprised between 2° and 90°, preferably between 20° and 45°.

5. Tool according to one of the preceding claims, wherein said central shaft (4s) of the end portion (4) has an outer diameter (DT) such that the dimensional ratio between the first diameter (D1 ) of said shaft (2) and the outer diameter (DT) of the central shaft (4s) of the end portion (4) is comprised between 0.5 and 2.9, preferably between 0.5 and 1 .5.

6. Tool according to the preceding claim, wherein the outer diameter (DT) of the central shaft (4s) of the end portion (4) has a dimension greater than or equal to the dimension of the first diameter (D1 ) of said shaft (2), such that the dimensional ratio between the first diameter (D1 ) of said shaft (2) and the outer diameter (DT) of the central shaft (4s) of the end portion (4) is greater than 0.5 and less than or equal to 1 .

7. Tool according to one of the preceding claims, wherein said central shaft (4s) of the end portion (4) has an outer diameter (DT) such that the ratio between the outer diameter (D3, D”) of the blade (5) and the outer diameter (DT) of the central shaft (4s) of the end portion (4) is comprised between 1 .01 and 3, preferably between 1 .5 and 2.

8. Tool according to one of the preceding claims, wherein said blade (5) comprises a plurality of ridges (50), each having a predefined thickness (CT) comprised between 0.01 mm and 2 mm, preferably between 0.01 mm and 0.5 mm.

9. Tool according to one of the preceding claims, wherein said blade (5) comprises a plurality of ridges (50) and a pitch (p) between two consecutive ridges (50) comprised between 1 mm and 2 mm.

10. Tool according to one of the preceding claims, wherein said blade (5) has a working surface (7) with a radial extension with respect to said longitudinal axis (X), projecting with respect to said first diameter (D1 ) of said shaft (2).

11. Tool according to the preceding claim, wherein the radial extension of the working surface (7) of said blade (5) is constant along the longitudinal axis (X) for at least 80% of the longitudinal length of said blade (5).

12. Tool according to claim 10, wherein the radial extension of the working surface (7) of said blade (5) varies along the longitudinal length of said blade (5).

13. Tool according to one of the preceding claims, wherein said mechanical stop (6) is defined by a predetermined portion, along said shaft (2), having a transverse dimension, with respect to the longitudinal axis (X), greater than the first diameter (D1 ) of said shaft (2).

14. Tool according to one of the preceding claims, wherein said mechanical stop (6) is defined by a change in diameter of the shaft (2) itself, at a predetermined portion along the longitudinal extension of the shaft.

15. Tool according to the preceding claim, wherein said shaft (2) has a second diameter (D2) greater than the first diameter (D1 ); said first diameter (D1 ) extending from said end portion (4) to said mechanical stop (6), said second diameter (D2) extending from said mechanical stop (6) tosaid gripping portion (3).

16. Tool according to any one of claims 1 to 12, wherein said mechanical stop (6) is defined by an abutment element (13) associated with said shaft (2) at a predetermined portion along the longitudinal extension of said shaft; said abutment element (13) having a transverse dimension with respect to the longitudinal axis (X) greater than the first diameter (D1 ) of said shaft (2).

17. Tool according to the preceding claim, wherein said abutment element (13) is part of an additional element (8) which can be associated with said shaft (2); the relative position between said shaft (2) and said additional element (8) being fixable by means of a positioning system (81 ) which blocks the relative sliding between said shaft (2) and said additional element (8).

18. Tool according to one of the preceding claims, wherein said proximal end (2p) of said shaft (2) is configured to connect to an electrical actuator (10) for promoting the rotation of said shaft (2) about said longitudinal axis (X).

19. Tool according to one of the preceding claims, wherein said end portion (4) is made as a single piece with said shaft (2).

20. Tool according to one of the preceding claims, wherein said end portion (4) is removable from said shaft (2) and interchangeable with other end portions (4) having different geometries.

21. Method for making undercuts within a solid material comprising the steps of:- preparing a drilling tool for making undercuts in accordance with one ormore of claims 1 to 20.- advancing said shaft with rototranslational motion along a longitudinal axis (X) in such a way that the blade (5) of said end portion (4) pierces said solid material (M) entering completely inside it;- advancing said shaft with rototranslational motion along said longitudinal axis (X) until a mechanical stop (6) is brought into abutment against an outer surface (S) of said solid material when said blade (5) is completely inside said solid material and a proximal end (5p) of said blade (5) is placed below the outer surface (S) of said solid material at a distance having a thickness (d) comprised between at least 0.5 mm and 100 mm.- continuing with the rotation (Ri) only of said tool for a number of rotations such as to create a cavity (C) completely internal to said solid material, partially closed by an edge (20) of solid material defining an undercut having a thickness (d) comprised at least between 0.5 mm and 100 mm.- activating a reverse rotation (Ro) of said tool to extract said blade (5);- removing said tool and said end portion (4) from said solid material in such a manner that said edge (20) presents a central hole, which places the internal cavity in fluid communication with the outside, having a diameter equal to the first diameter (D1 ) of said shaft (2) and smaller than the largest diameter of said blade (5).

22. Method according to the preceding claim, wherein when said mechanical stop (6) is in abutment against the outer surface (S) of said solid material, an internal cavity with a blind bottom is formed having a diameter equal to the largest diameter (D3, D3”) of the radial extension of said blade (5).

23. Method according to claim 21 or 22, wherein when said mechanical stop (6) abuts against the outer surface (S) of said solid material, an inner cavity with a blind bottom having a geometry equivalent to the involute of the outer contour of said blade (5) is formed.

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