Method for manufacturing a cutting head, cutting head and perforator

Abstract

This document describes a method for manufacturing a cutting head for a perforator used to cut bone tissue. The method comprises the following steps: machining a cutting head, comprising a plurality of cutting edges, from a material with a Rockwell C hardness (HRC) of less than 30 HRC; and surface finishing of the machined cutting head, the process of which does not include hardening. A cutting head is also provided.

Description

[0001] The present disclosure relates to a method for manufacturing a cutting head for a perforator, a cutting head and a perforator. In a particularly preferred embodiment, the disclosure relates to a method for manufacturing a cutting head for a perforator for cutting a hole in the skull of a human or animal. General state of the art

[0002] To perform surgical procedures within the cranial cavity, it is first necessary to gain access to the cavity by drilling one or more holes through the skull bone (the cranium). The process of drilling a hole through the skull is called trepanation. Trepanation is a difficult and delicate procedure because sufficient force must be applied to the drill bit to penetrate the hard layers of bone tissue, but the drill bit must be stopped immediately after perforating the skull to prevent damage to the dura mater or the soft tissue inside the skull.

[0003] Current perforators generally resemble conventional drills in that a forward force or pressure must be applied to drive the drill head through the skull. A major risk with such prior art designs is that, during cranium perforation, the forward force or pressure on the drill head can drive the drill head inward through the newly created hole and into the cranium, potentially damaging the dura mater.

[0004] Attempts to reduce this risk of dura mater damage have focused on stopping the rotation of the drill head once the cranium has been perforated, so that the rotating cutting or drilling head does not tear or otherwise damage the dura mater. Prior art skull perforators, in which the drill head is not permanently coupled to a drive shaft of an electric drill, provide a way to stop the drill head's rotation once the cranium has been perforated. However, these prior art cutting heads do not reduce the risk of dura mater damage if the drill head does not disengage from the drive shaft in a timely manner.

[0005] Furthermore, the manufacture of cutting heads for state-of-the-art perforators is time-consuming and labor-intensive. Specifically, the cutting heads are typically manufactured by: drilling and milling to achieve the correct shape; hardening to ensure the drill head is sufficiently hard to penetrate bone tissue; grinding to sharpen the cutting edges; deburring; and finally, surface finishing.

[0006] The inventors recognized the need for a simpler method for manufacturing a cutting head for a perforator used to cut bone tissue. They also recognized the need for a perforator with a cutting head that is easy to manufacture, yet functions well and offers significant functional reserves. Brief description of the invention

[0007] The disclosure provides a method for manufacturing a cutting head for a perforator, a cutting head and a perforator as defined in the attached independent claims, to which reference is now made. Preferred or advantageous features of the disclosure are set forth in dependent subclaims.

[0008] In a first aspect, the disclosure provides a method for manufacturing a cutting head for a perforator, wherein the method consists of: machining a cutting head comprising a plurality of cutting edges from a material having a Rockwell C hardness HRC of less than 30 HRC; and surface-treating the machined cutting head.

[0009] In contrast to known methods for manufacturing cutting heads, the present method allows the cutting head to be machined directly from a starting material to a cutting head with essentially the desired final shape. This is because the cutting head is machined from a material with a relatively low HRC of less than 30 HRC.

[0010] According to conventional wisdom in engineering, perforator cutting heads, in order to be suitable for cutting bone, must be hardened to over 50 HRC and then sharpened by grinding. However, the inventors have surprisingly discovered that a cutting head machined from a material with a hardness of less than 30 HRC, after machining and without hardening, still cuts bone tissue well and performs as well as, or even better than, a conventional cutting head made from a harder material.

[0011] According to the method of the present disclosure, the cutting head, after being machined from the starting material, is only surface-treated to produce the final cutting head. In this way, the time-consuming and costly secondary treatment of the machined cutting head is avoided. If the starting material has been shaped by machining, grinding or other manual processes are no longer necessary.

[0012] The present process therefore comprises only the steps of machining the starting material into the shape of the cutting head and then performing a surface treatment step on the machined cutting head. The process does not include a hardening or tempering step. The process also does not include separate grinding or deburring steps.

[0013] The material, with a Rockwell C hardness (HRC) of less than 30 HRC, is preferably supplied as a blank of a size suitable for machining to a cutting head for a perforator. The material with a Rockwell C hardness (HRC) of less than 30 HRC may be referred to as a blank, a starting material, or a blank made from starting material.

[0014] Prior art perforator cutting heads are typically manufactured from metal that, after hardening, has a Rockwell C hardness of at least 50 HRC, for example, 55 ± 3 HRC for conventional perforator cutting heads made from 1.4034 stainless steel. This is due to the long-standing misconception in the engineering field that perforator cutting edges require high hardness to cut cleanly through bone when a perforator is to be used for processes such as trepanation. To achieve this high-hardness cutting head, prior art methods typically used a high-hardness starting material and involved several energy- and labor-intensive machining steps, including hardening or tempering.In the present invention, however, the inventors provide a perforator cutting head that also performs well when it is manufactured using a significantly simplified manufacturing process without a hardening or tempering step from a starting material with a hardness of less than 30 HRC.

[0015] In known methods for manufacturing cutting heads, the cutting heads must be hardened, which slows down production and increases manufacturing costs. Furthermore, the hardening step necessitates separate grinding or sharpening steps before state-of-the-art cutting heads are ready for use.

[0016] Manual processes, including grinding, often lead to irregularities in the products. By eliminating the need for manual processing and / or grinding, the present method can result in more uniform cutting heads that function more consistently.

[0017] A known exemplary method for manufacturing a cutting head for a perforator comprises the following steps: turning and milling a blank; hardening and tempering; secondary machining such as grinding; deburring (manually and / or mechanically); and surface finishing. Additional inspection and cleaning steps are performed between the machining steps. It is clear that the method according to the present disclosure is much simpler and faster compared to this exemplary known method, as many of the previously required steps are eliminated.

[0018] It should be noted that, according to the present disclosure, "surface treatment" or "surface finishing" refers only to surface treatments, i.e., steps that modify the machined cutting head only superficially. Therefore, steps for "surface treatment" are finishing and / or polishing steps relating to surface finishing processes that improve the surface quality of the machined cutting head without reshaping the workpiece or substantially affecting its hardness. The step of surface treatment of the machined cutting head can be a step of finishing and / or polishing the machined cutting head.

[0019] The hardness of the machined cutting head essentially corresponds to the hardness of the starting material, since there is no hardening step between milling the starting material and the finished cutting head. In the prior art, heat treatment (e.g., hardening) usually introduces stress or distortion into the material of cutting heads. Since no heat treatment is carried out in the method according to the present disclosure, stress or distortion of the material is prevented.

[0020] The hardness according to the disclosure is measured in HRC, Rockwell hardness C, which is commonly used to scale the hardness of metals and metal alloys, especially steel. However, a person skilled in the art may also use any other suitable hardness scale that allows conversion to HRC, e.g., Rockwell hardness B, Brinell hardness, or Vickers hardness.

[0021] HRC can be measured according to DIN EN ISO 14577-1:2015-11.

[0022] In general, Rockwell hardness is calculated using the following equation: HR = N - hd, where HR is an arbitrary, dimensionless number (the Rockwell hardness), N and h are scale factors depending on which Rockwell scale is used, and d is the penetration depth in mm.

[0023] To determine the indentation depth, the Rockwell hardness test comprises four steps: applying an initial force of 98 N; applying a main load; maintaining the main load for a dwell time sufficient to complete the indentation; and releasing the load. The initial and main loads are applied by an indenter. In the HRC test, the indenter is a rounded conical diamond called the Brale indenter. The force N is 100, the indentation height (h) is 500, and the main load is 150 kgf (1471 N). The Brale indenter is a conical diamond with an inclusion angle of 120° ± 0.35° and a tip radius of 0.20 ± 0.01 mm.

[0024] The cutting head can be machined from the raw material by drilling and / or milling. Alternatively, machining can be performed using computer-controlled CNC drilling and milling. The advantage of using CNC machining is that it achieves a high degree of uniformity by reducing the risk of irregularities introduced by manual machining.

[0025] The machining step of the cutting head from the starting material preferably comprises one or more machining processes. The machining step may include or consist of one or more of the following: drilling, milling, single-point cutting, or multi-point cutting. The machining step does not include grinding.

[0026] Grinding is an important step in the production of prior art perforators. Prior art perforators are ground in a relatively complex manner using specialized CNC grinding machines that are solely capable of grinding. Hardened blanks, i.e., machined and hardened blanks, are clamped in fixtures and then automatically ground. In contrast, the process of the present disclosure does not require grinding; the cutting head is only drilled and milled – grinding is not considered a “machining” process within the meaning of the present disclosure.

[0027] Optionally, the cutting head and cutting edges are brought into their final shape by machining in a single operation and in a single setup. That is, a blank made of raw material is set up for machining, and the blank is then machined into a cutting head without removing the workpiece (the blank being machined) from the machining fixture. This contrasts with prior art methods where workpieces must be removed from the machining fixture for hardening and tempering before being re-set up for further machining steps. Advantageously, using a single setup for machining saves time and further improves reproducibility.

[0028] Optionally, the surface treatment step of the machined cutting head includes finishing or polishing. Optionally, the surface treatment step of the machined cutting head can include either vibratory finishing or electrolytic polishing. The surface treatment step of the machined cutting head can include either vibratory finishing or electrolytic polishing. Vibratory finishing is an automated process for deburring, edge rounding, surface homogenization, and creating a high-quality visual appearance. Vibratory finishing allows the cutting head to slide more smoothly against other perforator components.

[0029] The edge rounding that occurs during vibratory finishing and electrolytic polishing affects the sharpness of the cutting edges. By controlling the vibratory finishing and / or electrolytic polishing steps, the sharpness of the cutting edges can be adjusted to a desired level. Performing vibratory finishing and / or electrolytic polishing improves the surface finish of the processed cutting head, so that after surface treatment, the cutting head is ready for use in a perforator without further processing.

[0030] Alternatively, the surface treatment step of the machined cutting head can include or consist of dry ice blasting, glass bead blasting or blasting with other abrasives, or brushing directly in a CNC machine. Brushing directly in the CNC machine can be achieved by rotating plastic or metal brushes against the cutting head. This has the advantage that the resulting cutting edges are finished in the CNC machine, eliminating the need to place the machined cutting head in a vibratory finishing device or an electrolytic polishing bath.

[0031] The following processes are not included in the definition of surface treatment of the machined cutting head: turning, milling, grinding, hardening and tempering, and passivation. Therefore, the surface treatment step does not include any of the following: turning, milling, grinding, hardening, and tempering.

[0032] Preferably, the surface treatment step does not include passivation.

[0033] Optionally, the starting material from which the cutting head is machined has a hardness of less than 25 HRC, or less than 20 HRC. Alternatively, the starting material can have a hardness of approximately 18 HRC, for example, between 16 and 20 HRC, between 17 and 19 HRC, or between 17.5 and 18.5 HRC. The lower the HRC hardness, the easier it is to machine the cutting head in a single operation. However, this must be balanced against the requirement for sufficient cutting ability if the perforator cutting head is used to cut through bone tissue.

[0034] It should be noted that the hardness of the machined cutting head can essentially correspond to the hardness of the starting material, as there is no hardening or tempering.

[0035] The inventors have surprisingly found that the cutting head, even at an HRC of approximately 18 HRC, exhibits sufficient cutting capability to be suitable for trepanation, especially for the single-use trepanation common with perforators.

[0036] Alternatively, the material is a stainless steel, in particular an austenitic stainless steel. Austenitic stainless steel can be a particularly suitable material for use in the process according to the present disclosure, since austenitic steel cannot be hardened by heat treatment. Austenitic steel has therefore not been used in perforators to date. However, it has been found to be suitable for use in the process of the present disclosure, which does not include a hardening step (and in particular, no step of hardening by heat treatment). The corrosion resistance of austenitic steels is advantageous when used in perforators.

[0037] The processes of the present disclosure can be carried out with any suitable material, in particular stainless steel, but since there is no hardening step, austenitic steel, which is not hardenable (by heat treatment) and is corrosion-resistant, may be particularly suitable.

[0038] Furthermore, the stainless steel can optionally be one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441. In preferred embodiments, the stainless steel is 1.4404. Advantageously, stainless steel is readily available and relatively inexpensive, yet its properties are suitable for surgical applications. Although 1.4404 is more expensive than some other stainless steels, such as 1.4034, its production makes the cutting heads relatively inexpensive by eliminating unnecessary process steps.

[0039] In this disclosure, the nomenclature for various stainless steel compositions corresponds to DIN steel standards. Alternatively, the material can also be titanium or a titanium alloy.

[0040] Optionally, machining the cutting head can include machining a connector part. The connector part can be at least one recess and / or at least one projection. The connector part can be machined in the same setup and using the same machining process(s) as the rest of the cutting head, e.g., by drilling, milling, single-point cutting, or multi-point cutting.

[0041] In a second aspect, the disclosure provides a method for manufacturing a cutting head for a perforator, wherein the method comprises the following steps: machining a cutting head comprising a plurality of cutting edges from a material having a Rockwell C hardness HRC of less than 30 HRC; and surface finishing of the machined cutting head, wherein the method does not include hardening by heat treatment.

[0042] As outlined above, perforator cutting heads are typically manufactured by: drilling and milling to create the correct shape; hardening (through heat treatment) to ensure the drill head is hard enough to penetrate bone tissue; grinding to sharpen the cutting edges; deburring; and finally, surface finishing.

[0043] Although the method states that no hardening by heat treatment takes place, it is noted that the method preferably does not include any hardening step at all. Hardening by heat treatment is a standard step that usually follows machining (e.g., drilling and milling) of the cutting head and can be omitted in the method of the present disclosure. That is to say, the method does not include a hardening step by heat treatment and cannot include a hardening step.

[0044] Therefore, the disclosure may provide a method for manufacturing a cutting head for a perforator, wherein the method comprises the following steps: machining a cutting head comprising a plurality of cutting edges from a material having a Rockwell C hardness HRC of less than 30 HRC; and surface treatment of the machined cutting head, wherein the method does not include a hardening step.

[0045] Furthermore, the process cannot include a grinding step of the machined (and unhardened) cutting head. As explained above, grinding a hardened cutting head is a standard step in prior art processes for manufacturing cutting heads for perforators, which is generally performed after and required because of the heat treatment. This step can be omitted in the process of the present disclosure (since there is no heat treatment step).

[0046] The material can be a metal. The material can be a stainless steel. In particular, the material can be an austenitic stainless steel. As explained above, austenitic stainless steel can be a particularly suitable material for use in the process according to the present disclosure because austenitic steel cannot be hardened by heat treatment but is corrosion-resistant.

[0047] The stainless steel can be one of the following: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441.

[0048] The process preferably comprises only the following steps: machining the cutting head from a material with a Rockwell C hardness HRC of less than 30 HRC; and surface finishing of the machined cutting head.

[0049] The material can have a hardness (HRC) of less than 25 HRC, less than 20 HRC, between 16 and 20 HRC, between 17 and 19 HRC, or between 17.5 and 18.5 HRC. In a specific example, the material can have a hardness of approximately 18 HRC.

[0050] The machining step of the cutting head from the starting material (the material with a Rockwell C hardness HRC of less than 30 HRC) preferably comprises one or more machining processes. The machining step may include or consist of one or more of the following: drilling, milling, single-point cutting, or multi-point cutting.

[0051] The cutting head is preferably machined from the base material by drilling and / or milling. Alternatively, machining can be carried out using computer-controlled CNC drilling and milling.

[0052] The cutting head and cutting edges can be brought into their final shape by machining in a single machining step using a single device.

[0053] The surface finishing step of the machined cutting head may include finishing or polishing the cutting head and / or the cutting edges. The surface finishing step of the machined cutting head may include or consist of one or more of the following: vibratory finishing, electrolytic polishing, dry ice blasting, glass bead blasting or blasting with other abrasives, or brushing directly in a CNC machine. The surface finishing step does not include any of the following: turning; milling; grinding; hardening and tempering; and passivation.

[0054] All of the features described above with reference to the first aspect of the invention apply equally to the second aspect.

[0055] According to a third aspect, the present disclosure provides a method for manufacturing a perforator component, comprising the steps of the method according to the first or second aspect and further comprising a step of providing a connector for reversibly coupling the cutting head to a drive shaft, wherein the connector has a harder connector part with a higher HRC and a softer connector part with a lower HRC.

[0056] Optionally, the process further includes a step of attaching the harder connector part to the inner cutting head. By attaching the harder connector part to the inner cutting head, the cutting head can be directly engaged by the drive shaft of a perforator.

[0057] The harder connector part preferably has a higher Rockwell C hardness than the cutting head.

[0058] Optionally, the harder connector part has a Rockwell C hardness of at least 40 HRC, while the softer connector part has a Rockwell C hardness of less than 30 HRC. The softer connector part can be part of the cutting head or provided on it, which, as described above, has a Rockwell C hardness of less than 30 HRC. The inventors have surprisingly found that combining a relatively softer connector part with a relatively harder connector part allows the perforator to be highly functional and reliable, while at the same time being cheaper and faster to manufacture (especially when the softer connector part is provided on the cutting head).

[0059] In typical perforator designs, the cutting head is spring-loaded away from the drive shaft, so that when no pressure is applied to the tip of the cutting head, the cutting head and the shaft are separated, and the cutting head does not rotate, even if the drive shaft is turning. The connection between the cutting heads and the drive shaft is controlled by a connector that couples the cutting head to the drive shaft when pressure is applied to the tip of the cutting head. When the pressure is released, the connector decouples the cutting head from the drive shaft, so that the cutting head no longer rotates. One part of the connector can rotate with the drive shaft, so that the connector part of the stationary cutting head comes into contact with the connector part of the drive shaft when it is already rotating at high speed.

[0060] The need for the connector and cutting head to withstand this sudden impact has typically led designers of such prior art devices to make all connecting elements as hard as possible. As a rule, both interacting parts (e.g., both the pin and the recess) are made of the same high-hardness material to prevent damage if the two parts collide during use.

[0061] The present inventors have found that if the hardness of the softer connector part that may be provided on the cutting head is too close to the hardness of the harder connector part of a perforator, the parts may damage each other, which may occasionally prevent the decoupling mechanism from functioning safely after trepanation is complete.

[0062] In the perforator manufactured according to the present disclosure, the components of the coupling mechanism work together, due to the relatively low hardness of the softer connector part compared to the relatively high hardness of the harder connector part, to smooth the softer connector part during initial coupling, thereby ensuring safe decoupling of the cutting head when it moves into the distal position.

[0063] That is to say, in the perforator manufactured according to the present disclosure, the connector is designed such that, when the cutting head is in the distal position, the harder connector part is not in contact with the softer connector part, and, when the cutting head is in the proximal position, the harder connector part comes into contact with the softer connector part, so that the connector couples the inner cutting head to the drive shaft. The connector can also, or alternatively, connect an inner cutting head to an outer cutting head.

[0064] The term “distal” refers here to parts of the perforator that are positioned in the direction of the cutting edges of the perforator, which are intended to be in contact with the bone tissue during use, while the term “proximal” refers to parts that are further away from the bone to be drilled and are, for example, closer to the hand of the user holding the drill.

[0065] Optionally, the harder connector part has an HRC of at least 45 HRC; furthermore, optionally, at least 50 HRC; and even further, optionally, approximately 55 HRC.

[0066] Optionally, the softer connector part is at least 10 HRC, optionally at least 20 HRC, optionally at least 30 HRC, or optionally approximately 37 HRC (for example, between 34 and 40 HRC) softer than the harder connector part. That is, the harder connector part can be at least 10 HRC, optionally at least 20 HRC, optionally at least 30 HRC, or optionally approximately 37 HRC harder than the softer connector part.

[0067] Optionally, the harder connector part is made of stainless steel. Furthermore, optionally, the harder connector part is made of stainless steel 1.4034. Alternatively, the connector is made of stainless steel 1.4057, 1.4021, or 1.4112. The harder connector part may be hardened.

[0068] Optionally, the connector comprises: at least one coupling pin; and / or at least one ball; and / or at least one recess or cap; and / or at least one drive surface, such as an edge, an inclined plane, or a spiral plane. For example, the connector may include at least one pin attached to the cutting head and at least one recess for engagement with the at least one pin in a distal end of the drive shaft. Alternatively, at least one recess may be provided on the cutting head for engagement with at least one pin on the drive shaft.

[0069] Alternatively, at least one of the cutting head and the drive shaft can comprise a drive surface configured to engage with a drive surface or pin on the other of the cutting head and the drive shaft. A perforator with a connector comprising a drive surface and a pin is disclosed in WO2021198418A1, and all disclosures relating to connecting means between the drive shaft and the cutting head are incorporated herein by reference.

[0070] Pin-and-recess connectors are known in prior art perforators, and ball connectors are known in other fields. Advantageously, any type of connector can provide a secure, releasable engagement between the cutting head and the drive shaft of a perforator or between an inner and an outer cutting head.

[0071] In known connectors with a recess and pin of the type disclosed in US Patent No. 4,456,010, the positions of the recess and pin parts can be reversed. For example, the pin can be mounted in the drive shaft and the recess in the cutting head, or vice versa.

[0072] The connector can, for example, include a pin that is mounted on the drive shaft such that the pin extends radially from the shaft. The pin is preferably designed to engage in a corresponding recess in the cutting head in order to couple the cutting head to the drive shaft.

[0073] Alternatively, the connector can also include a section of the drive shaft with a recess. The recess can be designed to engage with a corresponding pin mounted on the cutting head.

[0074] At least part of the connector, e.g., the more rigid connector section, can be made from standard parts, i.e., standard components. Standard parts or components are parts used in a wide variety of products and may conform to specific DIN or ISO standards. They are very common and inexpensive.

[0075] In a fourth aspect, the revelation provides for a cutting head that was manufactured according to the procedure described in the first or second aspect, and in a fifth aspect, the revelation provides for a perforator component that was manufactured according to the procedure described in the third aspect.

[0076] In a sixth aspect, the disclosure provides a perforator for drilling bone tissue, comprising: a drive shaft with an axis of rotation A; an inner cutting head with the same axis of rotation A; and an outer cutting head arranged coaxially around the inner cutting head. The inner cutting head is designed to be displaceable relative to the drive shaft along the axis of rotation A between a distal position, in which the cutting heads cannot be driven by the drive shaft, and a proximal position, in which the cutting heads can be driven by the drive shaft. The perforator further comprises a connector for reversibly coupling at least two of the drive shaft, the inner cutting head, and the outer head to each other when the inner cutting head is in the proximal position.The connector comprises a harder connector part with a first Rockwell C hardness HRC and a softer connector part with a second HRC that is lower than the first HRC.

[0077] The perforator connector consists of at least two interacting parts—the harder connector part and the softer connector part—that interlock to couple at least two of the inner cutting head, the outer cutting head, and the drive shaft. A connector can alternatively be referred to as a coupling mechanism. Various types of connectors are known in engineering, such as pin-and-recess couplings, in which the connector consists of a pin and a separate recess that interlock when the inner cutting head is in the proximal position.

[0078] In the prior art, both parts of the connector (i.e., both the pin and the recess) are made of the same material, which, in the opinion of the present inventors, can lead to problems. In the present disclosure, the inventors have found that advantages can be achieved by making the two interacting parts of the connector from materials of different hardness. For example, a pin-recess type connector can be provided in which the pin is a harder connector part and the recess is a softer connector part, or vice versa.

[0079] As explained above with regard to the method of the present disclosure, providing the perforator with a relatively softer connector part and a relatively harder connector part allows the perforator to be very functionally reliable and, at the same time, especially when the softer connector part is provided on a cutting head produced according to the method of the present disclosure, to be cheaper and faster to manufacture.

[0080] In particular, the inventors surprisingly discovered that if the hardness of the connector parts (e.g., the pin and the recess of a pin-recess connector) is too similar, the connector parts can damage each other, which can sometimes prevent the reliable function of the decoupling mechanism after trepanation. Due to the relatively lower hardness of the softer connector part compared to the relatively higher hardness of the harder connector part, in the perforator of the present disclosure, the connector parts or the components of the coupling mechanism work together to smooth the connector parts during initial coupling, thereby ensuring reliable decoupling of the cutting head.

[0081] The connector is designed such that when the inner cutting head is in the distal position, the harder connector portion does not engage with the softer connector portion, and that when the inner cutting head is in the proximal position, the harder connector portion engages with the softer connector portion, thus coupling at least two of the inner cutting head, the outer cutting head, and the drive shaft. For example, the connector can couple the inner cutting head to the drive shaft, or the inner cutting head to the outer cutting head, or the outer cutting head to the drive shaft. Alternatively, the connector can couple all three—the inner cutting head, the outer cutting head, and the drive shaft—when the inner cutting head is in the proximal position.

[0082] Optionally, the harder connector part has a first HRC of more than 30 HRC and the softer connector part has a second HRC of less than 30 HRC.

[0083] Optionally, the second HRC of the softer connector part is less than 25 HRC. Alternatively, the second HRC is less than 20 HRC. Alternatively, the second HRC is approximately 18 HRC, for example, between 16 and 20 HRC, between 17 and 19 HRC, or between 17.5 and 18.5 HRC.

[0084] Optionally, the HRC of the harder connector part is at least 40 HRC. Alternatively, the first HRC is at least 45 HRC. Alternatively, the first HRC is at least 50 HRC. Even further optionally, the first HRC is approximately 55 HRC, for example, between 52 HRC and 58 HRC.

[0085] Optionally, the softer connector part is at least 10 HRC; optionally at least 20 HRC; optionally at least 30 HRC; optionally approximately 37 HRC, for example between 34 and 40 HRC, softer than the harder connector part. That is, the harder connector part can be at least 10 HRC; optionally at least 20 HRC; optionally at least 30 HRC; optionally approximately 37 HRC, harder than the softer connector part.

[0086] As is known for connectors, such as pin-recess type connectors, the position of the connector parts in the perforator can be reversed without affecting the perforator's function. For example, the perforator can be provided with a recess in the distal end of the drive shaft and a corresponding pin attached to a proximal end of the inner cutting head. When the cutting head moves into the proximal position, the pin is received in the recess, and the drive shaft is coupled to the cutting head.Similarly, if the positions of the pin and the recess are reversed, so that the recess is provided at the proximal end of the cutting head and the pin is provided at the distal end of the drive shaft, the connector still functions in the same way, as the pin is received into the recess and the drive shaft is coupled to the cutting head when the cutting head moves into the proximal position.

[0087] Similarly, the position of the harder connector part and the softer connector part can be changed without affecting the function of the perforator of the present disclosure.

[0088] Optionally, the connector is designed for reversible coupling of the drive shaft with at least one of the cutting heads when the inner cutting head is in the proximal position, so that the connector transmits a rotary motion from the drive shaft to the cutting heads.

[0089] In some preferred embodiments, one of the connector parts is provided on the inner cutting head and the other connector part is provided on the drive shaft.

[0090] In some preferred embodiments, the connector is designed to reversibly couple all three components—the drive shaft, the inner cutting head, and the outer head—to one another when the inner cutting head is in the proximal position. Advantageously, fewer components can be used when the connector couples all three components: the drive shaft, the inner cutting head, and the outer head.

[0091] Optionally, the softer connector part comprises a first softer connector part provided at one of the inner cutting head, the outer cutting head and the drive shaft, and a second softer connector part provided at another of the inner cutting head, the outer cutting head and the drive shaft.

[0092] Optionally, the first, softer connector part is provided on the drive shaft, the second, softer connector part is provided on the outer cutting head, and the harder connector part is provided on the inner cutting head. Specifically, the first, softer connector part can be a recess in a distal end of the drive shaft, the second, softer connector part can be a triangular opening in the outer cutting head, and the harder connector part can be a pin at the proximal end of the inner cutting head.

[0093] Optionally, the softer connector part is provided at least one of the following: the inner cutting head, the outer cutting head and the drive shaft; and the harder connector part is provided at another at least one of the following: the inner cutting head, the outer cutting head and the drive shaft.

[0094] In some embodiments, the softer connector portion is provided at the inner cutting head. When the softer connector portion is provided at the inner cutting head, it may preferably be provided as at least one recess in the inner cutting head. The entire inner cutting head may have one HRC equal to the second HRC; that is, if the softer connector portion is at least one recess in the inner cutting head, the second HRC of the softer connector portion is equal to the HRC of the inner cutting head.

[0095] The softer connector part can alternatively be provided on the drive shaft, for example as a pin attached to the drive shaft or as a recess formed in the drive shaft. The entire drive shaft can advantageously have a hardness equal to the second hardness.

[0096] In some embodiments, one of the harder and the softer connector parts is provided at the inner cutting head, and the other connector part is provided at the drive shaft.

[0097] For example, if the harder connector part is provided at the inner cutting head, the softer connector part is provided at the drive shaft. Alternatively, if the harder connector part is provided at the drive shaft, the softer connector part is provided at the inner cutting head.

[0098] Optionally, the softer connector part is provided on at least one of the following: the inner cutting head, the outer cutting head, and the drive shaft; and the harder connector part is not attached to any other component of the perforator. Optionally, in this embodiment, two of the inner cutting head, the outer cutting head, and the drive shaft, or all three, may be provided with a softer connector part. In this embodiment, the harder connector part may be at least one ball. The perforator may be designed such that the ball can move freely relative to the inner cutting head and the outer cutting head when the inner cutting head is in the distal position, and such that the ball is enclosed between the inner cutting head and the outer cutting head when the inner cutting head is in the proximal position.

[0099] In this aspect, a variety of connector types can be used, as long as the connector includes a softer connector part designed to engage with a harder connector part when the inner cutting head is in the proximal position.

[0100] Optionally, the connector comprises: at least one coupling pin; and / or at least one ball; and / or at least one recess, indentation, or spherical cavity (partially spherical cavity); and / or at least one driving surface such as an edge, an inclined plane, or a spiral plane. For example, the connector may comprise at least one coupling pin and at least one recess, or the connector may comprise at least one ball and at least one recess or cavity to receive the ball when the cutting head is in the proximal position. The recesses may be square, semi-cylindrical, or preferably shaped with an inclined insertion edge and a driving surface to impel the rotation of the pin or ball when it engages with the recess.

[0101] Optionally, part of the connector can be designed to convert the rotation of the inner and outer cutting heads relative to each other about the axis of rotation A into a translational displacement of the inner cutting head along the axis of rotation. For example, the perforator can include softer and harder connector sections designed to transmit the rotation of the drive shaft to the outer cutting head when the inner cutting head is in the proximal position.

[0102] Optionally, one of the harder and the softer connector portions includes an angled edge designed to convert a relative rotation of the inner and outer cutting heads into a translational displacement of the inner cutting head along the axis of rotation. Alternatively, the harder connector portion is the coupling pin, and the outer cutting head includes a groove or opening in a wall, the groove or opening having a proximal end to receive the pin when the inner cutting head is in the proximal position, and an angled edge to guide the pin toward the distal position in response to the relative rotation of the inner and outer cutting heads.

[0103] Optionally, the inner cutting head is made of stainless steel. Furthermore, optionally, the stainless steel is austenitic. Even further optionally, the stainless steel is one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441. In a preferred embodiment of the perforator, the inner cutting head is made of unhardened stainless steel 1.4404. This embodiment is particularly preferred when the softer connecting part is provided on the inner cutting head, e.g., as a recess.

[0104] Optionally, the inner cutting head includes machined cutting edges. Optionally, the cutting edges are drilled and milled. Furthermore, optionally, the cutting edges are CNC drilled and milled.

[0105] Optionally, the cutting edges are surface-treated or surface-machined. Optionally, the cutting edges are surface-treated by: finishing; and / or polishing. Furthermore, optionally, the cutting edges are vibratory-finished and / or electrolytically polished.

[0106] According to a seventh aspect of the present disclosure, a perforator for drilling bone tissue is provided, comprising: a drive shaft with an axis of rotation A; an inner cutting head with the same axis of rotation A;and a connector for reversibly coupling the inner cutting head to the drive shaft, wherein the inner cutting head is designed to be displaceable relative to the drive shaft along the axis of rotation A between a distal position in which the inner cutting head is not driven by the drive shaft and a proximal position in which the connector couples the inner cutting head to the drive shaft in order to transmit the rotary motion from the drive shaft to the inner cutting head, and wherein the connector comprises a harder connector part with a first Rockwell C hardness HRC and a softer connector part with a second HRC that is lower than the first HRC, the softer connector part being provided at least one by the inner cutting head and the drive shaft.

[0107] Optionally, the perforator further comprises an outer cutting head arranged coaxially around the inner cutting head. The outer cutting head may preferably be made of the same material as the inner cutting head, such that the Rockwell C hardness of the outer cutting head may be less than 30 HRC. The outer cutting head may preferably be a cutting head manufactured according to any aspect of the disclosure described above.

[0108] In embodiments comprising an outer cutting head, the connector may further be configured to couple the outer cutting head to the inner cutting head when the inner cutting head is in the proximal position, so that the rotational movement is transferred from the inner cutting head to the outer cutting head. Optionally, one or a portion of either the softer or the harder connector portion may be provided at the outer cutting head.

[0109] According to an eighth aspect of the present disclosure, a perforator for drilling bone tissue is provided, comprising: a drive shaft with an axis of rotation A; an inner cutting head with the same axis of rotation A; and an outer cutting head arranged coaxially around the inner cutting head. The inner cutting head is designed to be displaceable relative to the drive shaft along the axis of rotation A between a distal position, in which the cutting heads are not driven by the drive shaft, and a proximal position, in which the cutting heads are driven by the drive shaft.The perforator further comprises a connector for reversibly coupling the inner cutting head and the outer cutting head to each other when the inner cutting head is in the proximal position, and wherein the connector comprises a harder connector part with a first Rockwell C hardness HRC and a softer connector part with a second HRC that is lower than the first HRC.

[0110] According to a ninth aspect of the present disclosure, a cutting head for a perforator for cutting bone tissue is provided, wherein the cutting head comprises a plurality of cutting edges, characterized in that the cutting head is made of austenitic steel with a Rockwell C hardness HRC of less than 30 HRC.

[0111] The austenitic steel can be one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441.

[0112] Austenitic steel can have a hardness (HRC) of less than 25 HRC, less than 20 HRC, between 16 and 20 HRC, between 17 and 19 HRC, or between 17.5 and 18.5 HRC. In one particular example, the austenitic steel has a hardness of approximately 18 HRC.

[0113] The "perforator for cutting bone tissue" can be called a "bone perforator," "skull perforator," or "skull drill." The cutting head for a perforator can be called a "perforator cutting head," "bone perforator cutting head," "skull perforator cutting head," or "skull drill cutting knob."

[0114] Each feature of one aspect of the disclosure may be applied to other aspects of the disclosure in any suitable combination. Furthermore, each, some, and / or all of the features of one aspect may be applied to each, some, and / or all of the features of another aspect in any suitable combination. In particular, all procedural features provided in respect of the first aspect may be applied to each of the other aspects. Furthermore, and in particular, each feature provided in respect of the perforator according to the sixth aspect may be applied mutatis mutandis to a perforator according to the seventh or eighth aspect, or to the cutting head according to the ninth aspect.

[0115] It should also be noted that particular combinations of the various features described and defined in any aspect of the invention can be realized and / or provided and / or used independently of one another. Description of specific embodiments of the invention

[0116] Specific embodiments of the invention will now be described with reference to the figures, in which: Fig. 1 is a flowchart of an exemplary process according to the disclosure; Fig. 2 a cross-section along the axis of rotation A of an exemplary perforator according to the invention; Fig. 3a is a side view of the distal end of an exemplary drive shaft; Fig. 3b a detailed side view of the exemplary drive shaft Fig. 3a is engaged with a connector pin; Fig. 4 a semi-transparent view of the assembled exemplary perforator without its cylindrical housing in its position; Fig. 5a is a side view of an outer cutting head of another exemplary perforator according to the present disclosure; Fig. 5b a side view of an inner cutting head of the further exemplary perforator of Fig. 5a is; Fig. 6a a perspective isometric view of a cutting head arrangement of the further exemplary perforator of the Fig. 5a and Fig. 5b is; Fig. 6b a cross-sectional view of the further exemplary perforator of the Fig. 5a, Fig. 5b and Fig. 6a is; Fig. 7 a cross-section along the axis of rotation A of the further exemplary perforator of the Fig. 5a, Fig. 5b, Fig. 6a and Fig. 6b is; the Fig. 8 and Fig. 9 cross-sections along the axis of rotation A of another exemplary perforator are shown, wherein the inner cutting head is in a distal position or a proximal cutting position; Fig. 10a a side view of an inner cutting head of the further exemplary perforator of the Fig. 8 and Fig. 9 is; and Fig. 10b a perspective isometric cross-section of the further exemplary perforator of the Fig. 8, Fig. 9 and Fig. 10a is. Specific description

[0117] Fig. Figure 1 illustrates the steps of a method according to the present disclosure, which includes a step of machining a cutting head comprising a plurality of cutting edges from a material having a Rockwell C hardness HRC of less than 30 HRC. In one embodiment, the material is unhardened stainless steel 1.4404 with an HRC of about 18 HRC (corresponding to about 215 HB).

[0118] A blank made of the starting material (1.4404 stainless steel) with an HRC of less than 30 is set up in a CNC machining fixture and machined in a single CNC machining operation by drilling and milling the blank into the shape of a perforator cutting head. The cutting head is then directly machined into its desired finished shape, and the process involves only one further step: surface finishing or treatment of the machined cutting head.

[0119] The shape of a perforator cutting head is well known in engineering and includes a variety of cutting edges designed for use in a perforator for cutting bone.

[0120] In the exemplary embodiment of the method, the surface finishing step consists of vibratory finishing.

[0121] In this embodiment, an OTEC CF series vibratory finishing machine with ceramic grinding elements is used. The shape of the grinding elements can vary from round to sharp-edged; however, in this embodiment, they are triangular prisms with a height of 1 to 5 mm and a tip-to-tip diameter of 1 to 5 mm.

[0122] It should be noted that larger grinding elements cause more abrasion and could damage thin-walled parts. Therefore, the size of the grinding elements must be chosen to ensure they are appropriately dimensioned.

[0123] In this example, the vibration speed is set to 220 to 350 rpm for edge rounding and to 120 to 220 rpm for surface smoothing. A cutting oil is used as a lubricant, but other emulsions can also be used. The cutting oil is the same type used in CNC drilling and milling. This facilitates cleaning the parts, and the oil protects them during vibratory finishing.

[0124] In this embodiment, approximately 50 to 200 cutting heads, e.g., 125 cutting heads, are simultaneously inserted into the vibratory finishing machine. The more parts placed in the machine at once, the greater the material removal rate. Conversely, the fewer parts placed in the machine, the longer the vibratory finishing process takes.

[0125] After vibratory finishing, the cutting head is ready for use in a perforator without any further processing steps.

[0126] Alternatively, the surface finishing step can also consist of electrolytic polishing of the machined cutting head.

[0127] In contrast to the prior art, the process does not include any steps of grinding, hardening or tempering the cutting head.

[0128] Since the process does not involve hardening or tempering the starting material, the hardness of the cutting head is essentially the same as the hardness of the starting material used for the blank. For example, in one embodiment where the starting material is unhardened stainless steel 1.4404 with a hardness of approximately 18 HRC, the cutting head produced by the process also has a hardness of approximately 18 HRC.

[0129] The Fig. Figures 2 to 4 show a perforator design similar to the prior art perforator disclosed in US Patent No. 4,456,010. However, in the perforator according to the present disclosure, the cutting heads of said perforator have a hardness of less than 30 HRC and preferably about 18 HRC, while the connecting pin has a hardness of about 55 HRC, being made of hardened stainless steel 1.4034.

[0130] In Fig. 2 The perforator 10 comprises an inner cutting head 12, a hollow outer cutting head 14 arranged coaxially around the inner cutting head, and a drive shaft 16, all of which are rotatable about the same axis of rotation A. The drive shaft has a distal end 15 and a proximal end 17. The proximal end 17 can be connected to a hand drill, for example, one containing a motor. In particular, the proximal end 17 is a standardized connector 17A, such as a Hudson connector.

[0131] The distal end of the perforator 10 terminates in the distal tip 20 of the inner cutting head, which comes into contact with the bone during use and in Fig. 2 shown below. The proximal end of the perforator 10 terminates in the standardized connector 17A of the drive shaft, which is located in Fig. 2 is shown above.

[0132] The inner cutting head 12 is movable along the axis of rotation A between two positions: a distal position, in which the inner cutting head is not connected to the drive shaft 16, and a proximal cutting position, in which the inner cutting head 12 is connected to the drive shaft 16. The inner cutting head is biased away from the drive shaft 16 and into the distal position by a spring 18, such that the inner cutting head moves into the proximal cutting position only when the distal tip 20 of the inner cutting head 12 is pressed against a surface to be drilled, such as bone. The force with which the distal tip 20 must be pressed against the surface to overcome the bias force of the spring 18 is determined by the spring constant of the spring 18 and the axial distance between the distal position and the proximal cutting position.

[0133] When no pressure is applied to the distal tip 20 of the inner cutting head, the inner cutting head 12 and the drive shaft 16 are separated, and neither the inner nor the outer cutting head 12, 14 rotates, even if the drive shaft 16 is rotating. A cylindrical housing 22 is arranged coaxially around the outer cutting head 14.

[0134] The connection between the inner cutting head 12 and the drive shaft 16 is achieved by means of a recess-pin coupling, which has a recess 24 (in Fig. 2 not visible, as the cross-section runs along the recess, but in the Fig. 3A and Fig. (3B shown) in the distal end 15 of the drive shaft 16 and a corresponding coupling pin 28 extending diametrically through the inner cutting head 12, near its proximal end. The coupling pin 28 and the recess 24 act as a connector that reversibly couples the inner cutting head to the drive shaft. At least the recess 24, but optionally the distal end 15 of the drive shaft or the entire drive shaft 16, has a lower HRC hardness than the coupling pin 28. In particular, the HRC hardness of the recess 24 (or the distal end 15 or the drive shaft 16) can be less than 30 HRC or about 18 HRC.

[0135] That is, in this embodiment, the connector which reversibly couples the inner cutting head 12 to the drive shaft 16 comprises a harder part, which is a coupling pin 28 provided on the inner cutting head 12, and a softer part, which is a recess 24 provided in the distal end 15 of the drive shaft 16.

[0136] The outer cutting head 14 is not displaceable along the axis of rotation A and comprises two triangular openings 30 through which the two opposite ends of the coupling pin 28 extend, as shown in Fig. Figure 4a shows that the triangular openings 30 are arranged such that the apex of each triangular opening 30 points towards the proximal end of the perforator. Therefore, the displacement of the inner cutting head 12 towards the proximal cutting position moves the coupling pin 28 towards the apex of the triangular opening 30.

[0137] When the distal tip 20 of the inner cutting head 12 is pressed against a bone during use, a force is exerted that moves the inner cutting head 12 against the preload spring 18 until the coupling pin 28 engages with the recess 24 in the rotating drive shaft 16. In this proximal cutting position, the coupling pin 28 also engages with the side or tip of the triangular openings 30, so that rotational force is transferred from the inner cutting head 12 to the outer cutting head 14, and both cutting heads rotate together. As long as force is applied to the tip 20 of the inner cutting head to keep the coupling pin 28 engaged with the recess 24, the rotating drive shaft transmits rotational force to the cutting heads, causing both cutting heads to rotate and the perforator to pierce the bone at an inner cutting diameter of the inner cutting head 12 and at an outer cutting diameter of the outer cutting head 14.

[0138] However, as soon as the distal tip 20 of the inner cutting head 12 perforates the bone (for example, the inner surface of the cranium), the force exerted by the bone on the inner cutting head 12 is greatly reduced, so that it is exceeded by the force exerted on the inner cutting head 12 by the preload spring 18, causing the preload spring 18 to force the coupling pin 28 out of the recess 24 in the drive shaft. Both the inner and outer cutting heads should then immediately cease rotating to prevent damage to the dura mater when the preload spring 18 forces the inner cutting head 12 into its distal position.

[0139] In a preferred embodiment of the present invention, the inner cutting head 12 of the perforator 10 has a hardness of approximately 18 HRC, while the coupling pin 28 has a hardness of approximately 55 HRC (+ / - 3 HRC). The outer cutting head 14 preferably also has a hardness of approximately 18 HRC. In the present embodiment, the connector therefore comprises two softer connector parts: the recess 24 in the drive shaft 16 and the triangular openings 30 of the outer cutting head 14.

[0140] In the Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. Figure 7 shows an alternative perforator 70 according to the present disclosure. The perforator 70 comprises an outer cutting head 50 extending along the axis of rotation A, having bores 54 at its proximal end for receiving connector pins 60 of the perforator. The outer cutting head 50 has cutting edges 56 at its distal end.

[0141] The perforator 70 further comprises an inner cutting head 52 with cutting edges 57 at its distal end and engagement recesses 58 for engagement with the connector pins 60.

[0142] The inner and outer cutting heads 50, 52 of the perforator 70 have a hardness of about 18 HRC, while the connecting pins 60 have a hardness of about 55 HRC (+ / - 3 HRC) and are standard parts.

[0143] As above regarding the perforator 10 of the Fig. 2, Fig. 3a, Fig. 3b and Fig. As described in Figure 4, the inner cutting head 50 of the perforator 70 is rotatable along the axis of rotation A between a distal position and a proximal position. In the distal position, the connecting pins 60 are not engaged with the recesses 58 in the inner cutting head 52, so that the inner cutting head 52 and the outer coupling head 50 are not coupled.

[0144] In the proximal position, the connecting pins 60 engage with the recesses 58 in the inner cutting head 52 and the bores 54 in the outer cutting head 50, as shown in Fig. 6B shown, so that the rotation of the inner cutting head 52 is transferred to the outer cutting head 50.

[0145] Between the recesses 58 for engagement with the connecting pins 60, i.e., which form the proximal end of the inner cutting head 52, are projections 63a, 63b, 63c, which, as shown in Fig. 6A shows that the cutting head extends beyond the distal end of the outer cutting head 50 when the inner cutting head 52 is in the proximal position.

[0146] The projections 63a, 63b, 63c are designed such that, when the inner cutting head 52 is in the proximal position, they engage with corresponding recesses 72 in a distal end of the drive shaft 74. Therefore, when the inner cutting head 52 is moved from the distal position to the proximal position, the projections 63a, 63b, 63c engage with the corresponding recesses 72 of the drive shaft 74, so that the rotational movement of the drive shaft 74 is transmitted to the inner cutting head 52. As explained above, in this embodiment, the rotational movement of the inner cutting head 52 is transmitted to the outer cutting head 50 via the connecting pins 60.

[0147] In this embodiment, the connector has a harder connector part (pins 60) and a softer connector part (recesses 58) designed to couple the inner cutting head 52 with the outer cutting head 50.

[0148] The Fig. 8, Fig. 9, Fig. 10A and Fig. Figure 10B illustrates a further alternative perforator 300 according to the present disclosure. In this embodiment, the perforator 300 of the disclosure comprises a ball coupling. A hollow distal end part 303 of the drive shaft 302 of the perforator 300 comprises three openings 305 (in the Fig. 8 and Fig. Figure 9 shows only one opening 305, which are provided in a cylindrical wall of the drive shaft 302. The three openings 305 are round holes and are arranged at equal intervals around the circumference of the drive shaft. A ball 310 is received in each of the three openings 305. Each opening 305 is dimensioned to restrict the axial movement of the ball (along the axis of rotation A) and the rotational movement (about the axis of rotation A) relative to the drive shaft 302.

[0149] The perforator 300 has an inner perforator pin 314 or an inner cutting head extending along the axis of rotation A, and a cutting head 312 arranged coaxially around the perforator pin 314. Although the inner displaceable perforator head 314 of the perforator 300 is shown as a perforator pin 314 having a relative tip diameter significantly smaller than that of the cutting head 312, the perforator 300 is equally applicable to alternative perforators with an inner cutting head and an outer cutting head, or an inner drilling head and an outer machining head, as described in detail above with respect to the other embodiments of the perforator.

[0150] The spring 304 pre-tensions the perforator pin 314 away from the drive shaft 302 into a distal position, as shown in Fig. Figure 8 shows that the drive shaft 302 engages with a cylindrical housing 308 of the perforator 300 via two sliding rings 306. The hollow distal end 303 of the drive shaft 302 is arranged coaxially around a proximal end of the perforator pin 314. The cutting head 312 is arranged coaxially around both the perforator pin 314 and the distal end 303 of the drive shaft 302. As further shown in Fig. As shown in Figure 8, each ball 310 is constrained not only by the opening 305 in the drive shaft 302, but also by the perforator pin 314 and the cutting head 312. Therefore, each ball 310 is constrained within a predefined space when the perforator pin 314 is in the distal position, as shown in Figure 8. Fig. Figure 8 shows that within this space, the ball or balls 310 can move in a radial direction (i.e., along the radius of the perforator in a direction towards and away from the axis of rotation A). Therefore, since at least part of the inner surface of the cutting head 312 is radially spaced from the drive shaft 302, even if the inner surface of the cutting head 312 does not border an opening 305 in the wall of the drive shaft 302, a space 307 between the drive shaft 302 and the cutting head 312 can exist.

[0151] Each ball 310 can move freely in the circumferential direction (i.e., rotate about the axis of rotation A), for example, in response to the rotational movement of the drive shaft 302. Since each ball 310 is enclosed, so that its movement relative to the drive shaft 302 is restricted, the balls 310 rotate together with the drive shaft 302 about the axis of rotation A. That is, the balls 310 can rotate freely relative to the cutting head 312 and the perforator pin 314 when the perforator pin 314 is in the distal position, as shown in Fig. 8 shown. Therefore, the rotary motion of the drive shaft 302 is not transmitted to the cutting head 312 or the perforator pin 314 when the perforator pin 314 is in its distal position.

[0152] The perforator pin 314, similar to the inner cutting heads 12, 52 of the perforators 10, 70 of the prior art, is movable along the axis of rotation A between two positions. In a distal position, the perforator pin 314 is not connected to the drive shaft 302 via the balls 310, and in a proximal cutting position, as in Fig. As shown in Figure 9, the perforator pin 314 is connected to the drive shaft 302 via the ball 310. The perforator pin 314 is biased away from the drive shaft 302 and into the distal position by a preload spring 304, so that the perforator pin 314 only moves into the proximal cutting position when the distal tip 500 of the perforator pin 314 is pressed with sufficient force against a surface, such as the bone to be drilled.

[0153] When no pressure is applied to the distal tip 500 of the perforator pin 314, the perforator pin 314 and the cutting head 312 are disconnected from the drive shaft 302, since the ball 310 is neither connected to the perforator pin 314 nor to the cutting head 312 and can rotate freely relative to the cutting head 312 and the perforator pin 314 together with the drive shaft 302. Therefore, neither the perforator pin 314 nor the cutting head 312 rotates, even when the drive shaft 302 rotates.

[0154] The perforator pin 314 terminates in a distal section. The distal part includes a distal head 502 with a sharpened distal tip 500. The distal tip 500 is designed to penetrate the center of a bone disc to be cut. However, the distal head 502 and its sharpened distal tip 500 are designed to rub or scrape the bone rather than cut it when the perforator is used. The perforator pin is also oriented to create or drill a single, through-hole by penetration rather than cutting around the circumference of a circular bone disc. Thus, the function and structure of the perforator pin 314 of the present invention differ significantly from the inner cutting / drilling head 12 of the prior art perforators described above.

[0155] The distal part of the perforator pin 314 further consists of a distal shaft 506, which has a smaller diameter than the distal head 502. Therefore, the proximal end of the distal head 502, forming a lip 504, is connected to the distal shaft 506. The lip 504 can hold a bone disc to be cut, into which the distal head 502 has penetrated, in its position. The function of the lip 502 can thus be compared to the barbs of a barbed arrowhead. This ensures that a bone disc being cut remains stable during trepanation. Furthermore, the lip 504 can restrict the movement of the bone disc relative to the perforator pin 314, so that the bone disc can be removed after completion of the trepanation with the perforator 300.

[0156] The distal shaft 506 terminates proximally in a central shaft 508 with a diameter larger than the diameter of the distal shaft 506. The perforator pin 314 has a flange 510 at a proximal end of the central shaft 508, which is designed to engage in a flat inner surface 400 of an inner bore of the cutting head 312 when the perforator pin 314 is in the Fig. The distal position is shown in Figure 8. The flat inner surface 400 is perpendicular to the axis of rotation A. Therefore, the axial position of the flange 510 limits the distal axial movement of the perforator pin 314. When the perforator pin 314 is in the distal position shown in Figure 8, the axial movement of the perforator pin 314 is limited. Fig. As shown in Figure 9, in the proximal cutting position, the flange 510 is designed to engage with a flat end face 402 of the drive shaft 302. Therefore, the axial position of the flange 510 limits the axial movement of the perforator pin 314 proximally.

[0157] As in the Fig. 10A and Fig. As shown in Figure 10B, an engagement region 407 of the perforator pin 314 comprises a first plurality of indentations 512 designed to receive a portion of the spheres 310 when the perforator pin 314 is in its proximal cutting position. Likewise, an inner surface of the outer cutting head 312 comprises a second plurality of indentations 514, each designed to receive a portion of the spheres 310.

[0158] The first plurality of indentations 512 is angled relative to the axis of rotation A, so that any preload force of the spring 304 acting on the flat end surface 406 of the perforator pin 314 to push it in a distal direction along the axis of rotation A can be distributed between the spring 304 and the angled indentations 512 coupled to one of the balls 310.

[0159] When pressure is applied to the tip of the perforator pin 314 and the perforator pin 314 is forced from the distal position into the proximal cutting position, a cylindrical surface 408 allows the balls 310 to run easily along the cylindrical surface 408 and engage with the engagement region 407 of the perforator pin 314, as shown in Fig. Figure 9 shows that the engagement region 407 is positioned on the perforator pin 314 on a distal side of the cylindrical surface 408, such that when the perforator pin 314 moves into the proximal cutting position, the engagement region 407 is axially aligned with the openings 305 in the wall of the drive shaft 302 and the balls 310 (i.e., positioned at the same axial height as them), as shown in the Fig. 9 and Fig. 10B shown.

[0160] At least the perforator pin 314 of the perforator 300 has a hardness of approximately 18 HRC, and the balls 310 have a hardness of 55 HRC (+ / - 3). The outer cutting head 312 can also have a hardness of approximately 18 HRC. That is, the balls 310 form the harder connecting part, and at least the engagement region 407 of the perforator pin 314 forms the softer connecting part. In a preferred embodiment, however, the outer cutting head 312 and the drive shaft 302 have a hardness of 18 HRC, so that the harder connecting part, i.e., the balls 310, engages with softer connecting parts on the perforator pin 314, the outer cutting head 312, and the drive shaft 302.

[0161] Although the perforator 300 is shown with a perforator pin 314 and not with an inner cutting head 12, 52, the “ball coupling” connector mechanism can likewise be applied to a perforator with an inner cutting head and an outer cutting head, such as the perforators 10 and 70.

[0162] The manufacturing process of the present disclosure is applicable to the manufacture of various types of cutting heads (inner cutting heads 12, 52, 314 or outer cutting heads 14, 50, 312), various shapes of perforator heads (e.g., the perforator pin 314 and the inner cutting heads 12, 52 and outer cutting heads 14, 50, 312), and perforators 10, 70, 300 with various connector or coupling mechanisms. Similarly, perforators 10, 70, 300 with any type of construction and any type of connector or coupling mechanism can be constructed according to the present disclosure.

[0163] Embodiments of the disclosure can be described with reference to the following numbered paragraphs, with preferred features set out in the dependent paragraphs: 1. A method for manufacturing a cutting head for a perforator, the method comprising the following: Machining of a cutting head comprising a multitude of cutting edges from a material with a Rockwell C hardness HRC of less than 30 HRC; and Surface treatment of the machined cutting head. 2. Method according to paragraph 1, wherein the cutting head is machined by drilling and milling, optionally by computer-controlled CNC milling. 3. Method according to paragraph 1 or 2, wherein the cutting head and the cutting edges are brought into their final shape by machining in a single machining step using a single device. 4. Method according to paragraph 1, 2 or 3, wherein the step of surface treatment of the machined cutting head includes finishing or polishing the machined cutting head. 5. A method according to any of the preceding paragraphs, wherein the step of surface treatment of the machined cutting head comprises one of the following: vibratory finishing; and electrolytic polishing. 6. Method according to any of the preceding paragraphs, wherein the material has an HRC of less than 25 HRC, preferably between 17 and 19 HRC. 7. Method according to any of the preceding paragraphs, wherein the material is a stainless steel and optionally wherein the stainless steel is one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441. 8. A method for manufacturing a perforator component comprising the steps according to one of the preceding paragraphs and further comprising a step of providing a connector for reversibly coupling the cutting head to a drive shaft, wherein the connector has a harder connector part with a higher HRC and a softer connector part with a lower HRC. 9. The method according to paragraph 8, further comprising a step of attaching the harder connector part to the inner cutting head. 10. Method according to paragraph 8 or 9, wherein the harder connector part has an HRC of at least 40 HRC. 11. Method according to paragraph 8, 9 or 10, wherein the connector comprises: at least one coupling pin; and / or at least one ball; and / or at least one recess or cap; and / or at least one driving surface, such as an edge, an inclined plane, a spiral plane. 12. Cutting head, manufactured by the method according to any of paragraphs 1 to 7, or perforator component, manufactured by the method according to any of paragraphs 8 to 11. 13. Perforator for drilling bone tissue, comprising: a drive shaft with an axis of rotation A; an inner cutting head with the same axis of rotation A;and an outer cutting head arranged coaxially around the inner cutting head, wherein the inner cutting head is designed to be displaceable relative to the drive shaft along the axis of rotation A between a distal position in which the cutting heads are not driven by the drive shaft and a proximal position in which the cutting heads are driven by the drive shaft, wherein the perforator comprises a connector for reversibly coupling at least two of the drive shaft, the inner cutting head and the outer head to each other when the inner cutting head is in the proximal position, and wherein the connector comprises a harder connector part with a first Rockwell C hardness HRC and a softer connector part with a second HRC that is lower than the first HRC. 14. Perforator according to paragraph 13, wherein the first HRC of the harder connector part is higher than 30 HRC and the second HRC of the softer connector part is less than 30 HRC. 15. Perforator according to paragraph 13 or 14, wherein the second HRC of the soft connector part is less than 25 HRC, or optionally the second HRC is approximately 18 HRC. 16. Perforator according to paragraph 13, 14 or 15, wherein the first HRC of the harder connector part is at least 40 HRC. 17. Perforator according to any one of paragraphs 13 to 16, wherein the softer connector part is softer by at least 10 HRC or at least 20 HRC or at least 30 HRC than the harder connector part. 18. Perforator according to any of paragraphs 13 to 17, wherein the connector is designed to reversibly couple the drive shaft to at least one of the cutting heads when the inner cutting head is in the proximal position, so that the connector transmits a rotary motion from the drive shaft to the cutting heads. 19. Perforator according to paragraph 18, wherein one of the connector parts is provided on the inner cutting head and the other connector part is provided on the drive shaft. 20. Perforator according to any one of paragraphs 13 to 18, wherein the connector is designed to reversibly couple all three, the drive shaft, the inner cutting head and the outer head, together when the inner cutting head is in the proximal position. 21. Perforator according to paragraph 20, wherein the softer connector part comprises a first softer connector part provided at one of the inner cutting head, the outer cutting head and the drive shaft, and a second softer connector part provided at another of the inner cutting head, the outer cutting head and the drive shaft. 22. Perforator according to paragraph 20 or 21, wherein the softer connector part is provided at least one of the following: the inner cutting head, the outer cutting head and the drive shaft; and the harder connector part is provided at another at least one of the following: the inner cutting head, the outer cutting head and the drive shaft. 23. Perforator according to paragraph 20 or 21, wherein the softer connector part is provided on at least one of the following: the inner cutting head, the outer cutting head and the drive shaft; and the harder connector part is not attached to any other component of the perforator. 24. Perforator according to any one of paragraphs 13 to 17, wherein the connector is designed to reversibly couple the inner cutting head with the outer cutting head when the inner cutting head is in the proximal position, so that the connector transmits the rotary motion from the inner cutting head to the outer cutting head 25. Perforator according to paragraph 24, wherein one of the connector parts is provided at the inner cutting head and the other of the connector parts is provided at the outer cutting head. 26. Perforator according to paragraph 24 or 25, further comprising a drive shaft connector for reversibly coupling the drive shaft to at least one of the cutting heads when the inner cutting head is in the proximal position. 27. Method for manufacturing a cutting head for a perforator, the method comprising the following steps: machining a cutting head comprising a plurality of cutting edges from a material having a Rockwell C hardness HRC of less than 30 HRC; and surface finishing of the machined cutting head, wherein the method does not include any steps of hardening or grinding the machined cutting head. 28. The method according to paragraph 27, comprising only the following steps: machining the cutting head from a material having a Rockwell C hardness HRC of less than 30 HRC; and surface finishing of the machined cutting head. 29. Method according to paragraph 27 or 28, wherein the step of machining the cutting head from the starting material comprises one or more mechanical machining processes, optionally wherein the machining step comprises or consists of one or more of the following: drilling, milling, single-point cutting or multi-point cutting. 30. Method according to paragraph 29, wherein the cutting head is machined from a blank of the starting material by drilling and / or milling and optionally wherein the machining is carried out by computer-controlled CNC drilling and milling. 31. A method according to any of paragraphs 27 to 30, wherein the surface finishing step of the machined cutting head comprises finishing or polishing the cutting head and / or the cutting edges, and optionally wherein the surface finishing step of the machined cutting head comprises or consists of one or more of the following: vibratory finishing, electrolytic polishing, dry ice blasting, glass bead blasting or other blasting media blasting, or brushing directly in a CNC machine. 32. Method according to any one of paragraphs 27 to 31, wherein the material is stainless steel, or optionally the stainless steel is austenitic stainless steel. 33. Method according to paragraph 32, wherein the stainless steel is one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441. 34. Method according to any of paragraphs 27 to 33, wherein the material has an HRC of less than 25 HRC or less than 20 HRC or between 16 and 20 HRC or between 17 and 19 HRC or between 17.5 and 18.5 HRC or about 18 HRC. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2021198418A1

[0069] US 4,456,010 [0071, 0129] Cited non-patent literature

[0000] DIN EN ISO 14577-1:2015-11

[0021]

Claims

[1] A method for manufacturing a cutting head for a perforator for cutting bone tissue, the method comprising the following steps: Machining a cutting head comprising a plurality of cutting edges from a material having a Rockwell C hardness HRC of less than 30 HRC; and Surface finishing of the machined cutting head, and in which the process does not include hardening by heat treatment. [2] A method according to claim 1, wherein the method does not include a curing step. [3] A method according to claim 1 or 2, wherein the method further does not comprise a step of grinding the machined cutting head. [4] A method according to claim 1, 2 or 3, wherein the material is a metal. [5] The method of claim 4, wherein the material is a stainless steel. [6] The method of claim 5, wherein the stainless steel is an austenitic stainless steel. [7] A method according to claim 6 or 7, wherein the stainless steel is one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441. [8] A method according to any one of the preceding claims, comprising only the following steps: machining the cutting head from a material having a Rockwell C hardness HRC of less than 30 HRC and surface machining the machined cutting head. [9] A method according to any one of the preceding claims, wherein the material has an HRC of less than 25 HRC. [10] The method of claim 9, wherein the material has an HRC of less than 20 HRC. [11] A method according to claim 9 or 10, wherein the material has an HRC between 16 and 20 HRC or between 17 and 19 HRC or between 17.5 and 18.5 HRC. [12] The method of claim 11, wherein the material has an HRC of about 18 HRC. [13] A method according to any one of the preceding claims, wherein the step of machining the cutting head comprises one or more of the following: drilling, milling, single-point cutting or multi-point cutting. [14] Method according to claim 13, wherein the cutting head is machined by drilling and milling, optionally computer-controlled CNC milling. [15] A method according to any one of the preceding claims, wherein the cutting head and the cutting edges are machined to their final shape in a single machining step using a single device. [16] A method according to any one of the preceding claims, wherein the step of surface treating the machined cutting head comprises finishing or polishing the machined cutting head. [17] The method of claim 16, wherein the step of surface treating the machined cutting head comprises one of the following: vibratory grinding; and electrolytic polishing. [18] A method of manufacturing a perforator component comprising the steps of any preceding claim and further comprising a step of providing a connector for reversibly coupling the cutting head to a drive shaft, the connector comprising a harder connector part having a higher HRC and a softer connector part having a lower HRC. [19] Cutting head manufactured according to the method of any one of claims 1 to 17, or perforator component manufactured according to the method of claim 18. [20] Cutting head for a perforator for cutting bone tissue, the cutting head comprising a plurality of cutting edges, characterized bythat the cutting head is made of austenitic steel with a Rockwell C hardness HRC of less than 30 HRC. [21] Cutting head according to claim 20, wherein the austenitic steel is one of: 1.4301; 1.4305; 1.4306; 1.4307; 1.4310; 1.4401; 1.4404; 1.4435; and 1.4441. [22] Cutting head according to claim 20 or 21, wherein the austenitic steel has an HRC of less than 25 HRC or less than 20 HRC. [23] Cutting head according to claim 20, 21 or 22, wherein the austenitic steel has an HRC between 16 and 20 HRC or between 17 and 19 HRC or between 17.5 and 18.5 HRC. [24] Cutting head according to one of claims 20 to 23, wherein the austenitic steel has an HRC of about 18 HRC.

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