Micro saw balancing system

Abstract

To provide a surgical or dental cutter allowing for executing balance adjustment in an easy and efficient manner, with a motor part separable from a handpiece.SOLUTION: A cutter (1) includes: a handpiece (4) equipped with a transmission module (2) for a cutting tool (3); and a motor (10) removably connected to the handpiece (4). The transmission module (2) includes: a motor connection part configured so that rotation is set by the motor (10); and a motion chain converting a rotational motion of the motor (10) into a first linear motion (M1) of a blade holder (27) via a rotation transmission shaft provided with an eccentric body. The transmission module (2) further comprises a counter-mass (5) arranged so as to, being synchronized with the first linear reciprocating motion (M1) of the blade holder (27), move according to a second linear reciprocating motion (M2) in an opposite direction to the first linear reciprocating motion (M1).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to the field of dental or surgical microsaws, i.e., handpieces equipped with cutting tools. More specifically, the present invention relates to a balance adjustment module for such microsaws.

Background Art

[0002] An electric handpiece equipped with an integral motor that generates a linear reciprocating motion of the saw is known. The Stryker product "Core Reciprocating Saw" is an example of such a microsaw equipped with a reciprocating cutting tool that reciprocates at a frequency of 10,000 to 30,000 reciprocations per minute depending on the movement length of about 3 mm and the motor speed. This product was the subject of now-expired Patent Document 1.

[0003] In this technique, the rotational motion of the motor is converted into a reciprocating linear motion of the blade holder via a finger attached to a ball bearing oriented off-axis with respect to the transmission shaft.

[0004] The drawback of this technique is that the center of mass of the handpiece moves periodically and significantly, resulting in a high level of vibration being directly transmitted to the operator's hand. Also, the vibration limits the cutting efficiency, and as the speed and the power applied to the motor increase, it reaches a peak and, in fact, the vibration increases, so the efficiency decreases as the power increases. Therefore, the cutting accuracy and speed are limited by the movement of the center of mass of the drive shaft clamp blade system.

[0005] In the surgical field, saws for cutting bone are also known. For example, from Patent Document 2, this operates like a chainsaw, i.e., it is based on one or more flexible belts with abrasive teeth and is rotationally driven (e.g., in pairs, in opposite directions around fixed high-rigidity guide components). However, this technique is not suitable for high-precision operations involving small dimensions, and the configuration of the cutting tool also significantly reduces the operability of the tool.

[0006] In the field of surgery, techniques for compensating for vibration using several blades driven in opposite directions are still known, such as the technique described in Patent Document 3. However, this technique is relatively complex to implement and is very cumbersome in terms of the working area of ​​the tool.

[0007] Patent Document 4 further describes a cutting tool that is subjected to both low-frequency reciprocating motion and very high-frequency ultrasonic vibration. A conversion element with oblique grooves in which drive pins are positioned allows the reciprocating motion to be applied to the blade drive cylinder and jointly to the counterweight cylinder, respectively. However, a drawback of this type of tool is that the motor part and the blade drive part cannot be separated due to the integrated balancing device.

[0008] A much older technology disclosed in Patent Document 5 relates to a surgical instrument comprising a connecting rod system connected to a rotor integrated with a motor shaft, with a counterweight provided on the rotor. The drawback of such technology is that the counterweight is directly incorporated into the motor portion, which affects its performance and further hinders the modular configuration of the balancing device. Therefore, a technology free from these known limitations is needed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] U.S. Patent No. 4,036,236 [Patent Document 2] U.S. Patent No. 5,725,530 [Patent Document 3] International Publication No. 97 / 10765 [Patent Document 4] U.S. Patent Application Publication No. 2015 / 066032 [Patent Document 5] U.S. Patent No. 3,642,002 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a new dental or surgical microsaw in which balancing can be performed in a simple and efficient manner and the motor part can be separated from the handpiece.

[0011] Another object of the present invention is to propose a new dental or surgical microsaw that requires minimal space and minimal fitting compared to existing technologies. [Means for solving the problem]

[0012] According to the present invention, these objectives are surgical or dental cutting devices comprising a motor connected to a handpiece equipped with a transmission module for a cutting tool, wherein the transmission module is A motor coupling section configured to be rotationally driven by a motor, This is achieved by a cutting device comprising a motion chain that converts the rotational motion of a motor into a first linear reciprocating motion of a blade holder via a rotary transmission shaft equipped with an eccentric body.

[0013] The transmission module is further characterized by comprising a counter mass arranged to move in a second linear reciprocating motion that is synchronized with the first linear reciprocating motion of the blade holder and in the opposite direction to the first linear reciprocating motion.

[0014] One advantage of the proposed solution is that it reduces vibration levels without requiring the simultaneous implementation of complex solutions and without creating significant additional space in both the handpiece and cutting tool work areas.

[0015] Another advantage of the proposed solution is that it provides a modular structure for the transmission conversion system that ensures both sufficient connection strength between the handpiece and the motor at the operational level, and easy disassembly of the motor portion for use in combination with other surgical instruments.

[0016] In one preferred embodiment, the first motion chain of the transmission module comprises a first drive finger for a blade holder attached to a first portion of the eccentric body, and a second drive finger for a countermass attached to a second portion of the eccentric body.

[0017] The advantage of this solution is that it can be easily integrated into existing technology simply by doubling the number of fingers, without the need to create a parallel transmission mechanism for the countermass that could cause parasitic vibrations, such as those that increase vibrations rather than effectively reduce them.

[0018] In a more preferred embodiment, the eccentric body is arranged symmetrically in a "V" shape, the first drive finger of the blade holder is attached to a first series of bearings around the first portion of the eccentric body, and the second drive finger of the blade holder is attached to a second series of bearings around the second portion of the eccentric body.

[0019] The advantage of this solution is that counter-synchronous motion of the countermass can be generated by using an eccentric body of a normal form in the transmission motion chain and simply adding a second finger symmetrically mounted on a series of bearings. Thus, the integration of the counter-mass actuated system is particularly easy on the same motion chain with minimal spatial requirements.

[0020] According to another preferred embodiment, the geometric shape of the counter mass is adapted to the geometric shapes of the cutting tool and blade holder, providing maximum flexibility in the design of the balancing system. Therefore, preferably, the counter mass is cylindrical to correspond to a blade holder in the form of a shaft, which is also cylindrical.

[0021] According to another preferred design, the counter mass is axially guided along a transmission axis that vectorially corresponds to the longitudinal displacement direction of the blade holder and the cutting tool by at least one axial guide element inserted into at least one guide hole made in the counter mass.

[0022] The technical advantage of this solution is that it can compensate as much as possible for the vibrations generated by the back-and-forth movement of the cutting tool, which is usually also guided in this direction, by the blade holder. Therefore, the vibrations are limited to the same direction, there is no need to control interfering movements, and the automatic balancing operation becomes easier.

[0023] According to an even more preferred variant corresponding to this embodiment, the axial guide element is formed by a first axial guide rail and a second axial guide rail that connect a first frame part connected to the motor in parallel to a second frame part that supports and axially guides the blade holder of the transmission module, and the first axial guide rail and the second axial guide rail are inserted into respective guide holes of the counter mass.

[0024] The additional technical advantages of this variant are, on the one hand, that the guiding characteristics of the counter mass can be maximized, and on the other hand, that space can be left in the center to accommodate the connecting shoe for the blade holder. Also, due to the fact that the rails function simultaneously as guide pins for the counter mass and as connecting elements for the frame of the transmission module, the number of parts required for its realization can be reduced, and thus the manufacturing cost can be reduced.

[0025] In yet another preferred embodiment, the surgical or dental cutting device according to the present invention is characterized in that the transmission module also includes a cooling device for the counter mass.

[0026] The advantage of this solution is that it optimizes the balancing of the device obtained through the countermass by minimizing the effects of undesirable heating resulting from friction when the overall kinetic energy of the system increases.

[0027] According to a more preferred embodiment for realizing such a cooling device, the first axial guide rail comprises a first integrated cooling duct, and / or the second axial guide rail comprises a second integrated cooling duct.

[0028] The advantage of this solution is that the cooling mechanism can be directly integrated with the guide element, which minimizes the overall system size and therefore eliminates the need for dedicated parts to perform this additional technical cooling function, which is carried out by the directly integrated element, thus allowing other functions to be performed simultaneously.

[0029] In yet another preferred embodiment, the transmission module is detachably connected to the motor, and the weight of the countermass is determined to be greater than a minimum value defined in relation to the total weight of the blade holder and the cutting tool as a function of the disconnection force of the transmission module from the motor, the travel length of the cutting tool, and the frequency of the oscillation of the reciprocating motion of the cutting tool.

[0030] In another preferred embodiment, the weight of the counter mass is determined to be lower than a predetermined value determined by the heat balance.

[0031] One advantage of each of these two solutions is that it allows for the definition of a counter mass, which is preferably smaller than, but not necessarily the same as, the assembly formed by the cutting tool and blade holder. Thus, it is possible to reduce the dimensions of this counter mass and minimize the overall dimensions of such an automatic balancing system, while at the same time maximizing the level of system design to suit the needs, depending on whether the reliability of the motor coupling to the level of heating during use is prioritized, for example, as a function of the operation performed.

[0032] Therefore, according to another particularly preferred embodiment, the weight of the counter mass is simply 25% to 50% of the total weight of the assembly formed by the blade holder and cutting tool, which is optimal in terms of connection reliability and heating during use.

[0033] In yet another preferred embodiment, the density of the counter mass is greater than 7000 kg / m3, which further reduces the volume of the counter mass and therefore its bulk relative to a given weight, resulting in a minimum level of friction and heating generated during use.

[0034] In yet another preferred embodiment, the motor coupling portion of the transmission module consists of a grooved hole that cooperates with a standard coupling nose of the motor, having a series of grooves into which an O-ring is inserted.

[0035] Such a configuration of the transmission module allows for connection with any standard dental or surgical micromotor without requiring its adaptation. Thus, the proposed solution resolves any potential incompatibility issues.

[0036] Furthermore, since the transmission module is compatible with any type of conventional micromotor, and therefore a handpiece equipped with such a transmission module can be sold separately from the "motor" component, which can be easily connected and disconnected, the present invention also relates to such handpieces equipped with such a transmission module independent of the motor.

[0037] Other advantageous configurations will become more apparent from the following description of specific embodiments of the invention, given as non-limiting examples and represented by the accompanying drawings. [Brief explanation of the drawing]

[0038] [Figure 1]This shows a side view of the functional components of a surgical or dental cutting tool according to the present invention, namely a micromotor and a handpiece / microsaw. [Figure 2A] This shows a three-dimensional profile of a typical micromotor for dental or surgical applications. [Figure 2B] This shows a sagittal cross-sectional view of a typical micromotor coupling nose for dental or surgical applications. [Figure 3] This is a perspective view of a surgical or dental cutting tool according to a preferred embodiment of the present invention, which is provided with a transmission module balanced by a short countermass. [Figure 4] This is a perspective view of a transmission module for a surgical or dental cutting tool, according to another preferred embodiment of the present invention, which has a long countermass. [Figure 5] Figure 3 is an exploded perspective view of a transmission module for a surgical or dental cutting tool according to a preferred embodiment. [Figure 6] Figures 3 and 4 are sagittal cross-sectional views of the transmission module. [Figure 7A] This is a plan view of a transmission shaft and an eccentric body and fingers for operating a blade holder and countermass, respectively, according to a preferred embodiment described with reference to the aforementioned figures. [Figure 7B] This is a sagittal cross-sectional view of a transmission shaft and an eccentric body and fingers for operating a blade holder and countermass, respectively, according to a preferred embodiment described with reference to the aforementioned figures. [Figure 8] This is a three-dimensional profile of a transmission module for a surgical or dental cutting tool, according to a preferred embodiment, which includes a long countermast and further comprises an integrated cooling mechanism. [Modes for carrying out the invention]

[0039] Figure 1 shows a side view of the functional components of a surgical or dental cutting tool according to the present invention, which comprises a first part including a motor and another part that constitutes the handpiece itself, i.e., a part operated by a dentist, similar to a conventional dental handpiece.

[0040] Therefore, on the right side of Figure 1, the micromotor 10 and its connecting nose 11 can be distinguished, and the connecting nose 11 conventionally includes a series of grooves in which an O-ring is arranged for transmitting rotational motion, indicated by the arrow R in this figure. Figure 2A shows such a micromotor 10 in a perspective view, which is in all respects similar to a typical micromotor 10 for a handpiece having a short connecting nose 11 in which an O-ring 111 is arranged in a series of grooves 110, as seen in Figure 2B which shows a sagittal cross-section of the connecting nose in detail.

[0041] On the left side of Figure 1, the handpiece housing 4 (i.e., its outer casing) is visible, surrounding the transmission module 2, which will be described below. This transmission module 2 enables the conversion of the rotational motion applied at the inlet of the handpiece 4 into a reciprocating motion M1 of the cutting tool, which is not shown in this figure, and which corresponds to the movement of the blade holder 27 (i.e., the element supporting the cutting tool 3), and will be referred to below as the “first” reciprocating motion M1. These two elements are further shown in Figure 3, which outlines a transmission and automatic balancing mechanism according to a preferred embodiment of the present invention.

[0042] The left end of the handpiece 4 shows a clamping device 6 for a cutting tool 3, which is provided with fins corresponding to an integrated irrigation channel 61 for supplying physiological fluid to a surgically treated area 61 to minimize heating of this area. Solutions for connecting the cutting tool to a transmission mechanism, for example as described in the applicant's European Patent No. 2316356, may be very suitable for mounting the cutting tool 3 within the scope of the present invention, and for this reason, no further details are provided below with respect to these embodiments for mounting the cutting tool 3 to the transmission module 2 of the handpiece 4.

[0043] The modular structure thus proposed includes a handpiece 4 supporting a cutting tool 3 for forming a detachable microsaw for a micromotor 10, and thus, on the one hand, it provides the possibility of using the same surgical micromotor 10 in combination with the handpiece 4, as well as in combination with other mechanical handpieces available in hospitals or medical practices (e.g., contra-angles for implants), and on the other hand, it makes it possible to ensure a more efficient cleaning, decontamination, and sterilization process for all elements of the handpiece 4 (especially the components that come into contact with irrigation fluid and thus indirectly with the patient). In fact, the possibility of disconnecting the handpiece 4 from the motor allows for better manual cleaning of the handpiece 4, or the use of dedicated instruments when cleaning with a washer or heat sterilizer.

[0044] Figure 3 shows in more detail a transmission mechanism according to a preferred embodiment of the present invention, wherein the counter mass 5 used is a short counter mass 5B, and therefore its purpose is to minimize the generation of friction and excess heat in order to achieve automatic equilibrium. It consists of a three-dimensional perspective view of the complete assembly comprising a micromotor 10 mounted on a handpiece 4, with the casing of the handpiece 4 removed to see the interior (in particular the transmission module 2 enclosed by a dotted line), which is intended to transmit the motion of the motor to the cutting tool 3 according to a first reciprocating motion M1 with a predetermined travel length D.

[0045] The cutting tool 3, which operates in translational reciprocating motion, is driven by a blade holder 27 and is attached to the blade holder via a clamping device 6 equipped with an integrated irrigation channel 61 that supplies physiological fluid to the surgical treatment area. The conversion of the motor's rotational motion to the translational motion of the blade holder 27 is performed via a first finger 241, the structure of which is described in detail with reference to Figures 7a and 7b, and which is inserted into a first insertion hole 272 of a connecting shoe 271 provided for this purpose. The connection portion of the blade holder 27 between the connecting shoe 271 and the clamping device is then formed by a cylindrical body 270.

[0046] As can be seen in Figure 3, the transmission module comprises a frame 20 formed by a first part 201 for connecting to the micromotor 10 and a second part 202 that is U-shaped and constitutes support for the blade holder 27. The first part 201 and the second part 202 are connected to each other by two cylindrical rods, respectively, forming a first axial guide rail 261 and a second axial guide rail 262 in parallel, and constituting an axial guide element 26 for the counter mass 5 (here, a short counter mass 5B). In this way, the frame 20 can perform the guiding function for the counter mass 5 without requiring the addition of dedicated parts. The short counter mass 5B is driven by a second reciprocating motion M2 opposite to the first reciprocating motion M1 of the cutting tool via a second finger 242 inserted into a second hole 51 of the counter mass 5.

[0047] Therefore, compared to the technology of the prior art, automatic balancing was achieved simply by doubling the number of fingers, without the need to substantially modify the frame structure, drive mechanism, and especially the eccentric body 23 shown in Figures 6 and 7a / 7b. This eccentric body, which rotates around the same axis as the axis of the transmission shaft 22, generates reciprocating translational motion of the finger ends, while the non-constant distance along the axis of rotation along the entire eccentric body causes motion toward and away from the lower end of the finger, respectively.

[0048] Figure 4 shows an enlarged view of a transmission module 2 according to another preferred embodiment of the present invention, this time using a long countermass 5A instead of the short countermass 5B shown in the previous Figure 3. The other parts shown in this figure are identical in all respects to those in Figure 3 and will not be described again in detail. The transmission and balancing mechanism remains identical to that of the previous embodiment by enabling the generation of a first reciprocating motion M1 of the blade holder 27 from a rotational motion R supplied as input via the micromotor 10 and the generation of a second reciprocating motion M2 of the long countermass 5A in parallel. The second reciprocating motion M2 of the countermass is synchronized in opposite phase to the first reciprocating motion M1, and these two motions M1 and M2 are always generated via a first finger 241 and a second finger 242, respectively, only their ends visible, with the rest hidden beneath the long countermass 5A. The direction of motion of the first finger S1 is always opposite to the direction of motion of the second finger S2.

[0049] Figure 5 is an exploded perspective view of a transmission module 2 for a surgical or dental cutting tool, according to a preferred embodiment of the previous Figure 4, i.e., having a long counter mass 5B. Here, we can see the bodies of the drive fingers (i.e., the first drive finger 241 of the blade holder 27 and the second drive finger 242 of the counter mass 5A), each having two longitudinal guide holes 52 that allow for the insertion of each of the axial guide rails oriented parallel to the displacement axis of the blade holder 27, from which the cylindrical body 270 and the connecting shoe 271 can be seen. In this figure, only the first axial guide rail 261 is visible. This figure further highlights the grooved connecting hole 21 of the transmission module 2, which is intended to cooperate with the motor connecting nose 11 to impart rotational motion to the transmission shaft, as shown in the following figure, and thus constitutes a preferred structural modification for the implementation of the motor connecting portion of the transmission module 2.

[0050] Figure 6, a sagittal cross-sectional view of a transmission module that can be used in a preferred embodiment of the transmission module shown in Figures 3 and 4, shows the first longitudinal axis AA of the motion of the cutting tool 3 via the blade holder 27. The rotational motion R of the micromotor 10 is transmitted to a rotary drive shaft 22 that extends along a second longitudinal axis BB parallel to the first longitudinal axis AA. This second longitudinal axis is not shown in this figure for readability but can be seen in Figures 7a and 7b, which are described below in particular. The transmission shaft 22 is rotatably mounted between an input bearing 28 and an output bearing 29, which are integral to the first and second parts 201 and 202 of the frame 20 of the transmission module 2, respectively. An eccentric body 23, configured symmetrically in a V-shape, is also attached to this rotary transmission shaft 22. The eccentric body 23 comprises a first portion 231 to which the first finger 241 is attached, the reciprocating motion of which drives the blade holder 27 and, as a result, the cutting tool 3; and a second portion 232 to which the second finger 242 is attached, the second portion 232 provided to drive the counter mass 5 in order to achieve automatic balance of the system. In this figure, a second insertion hole 51 located in the counter mass 5 for the second finger 242 is clearly visible. In order to convert the rotational motion of the eccentric body 23 into the reciprocating motion of the fingers, each body of these fingers is also provided with a set of bearings (i.e., a first set of bearings 251 for the first finger 241, and correspondingly a second set of bearings 252 for the second finger).

[0051] The transmission mechanism, or more precisely, the conversion of rotational motion applied to the input into reciprocating translational motion, will be described in detail with reference to Figures 7a and 7b, which show a sagittal view and a top view, respectively, of the transmission shaft 22, which has an eccentric body and fingers attached thereto.

[0052] As can be seen in Figure 7a, the transmission shaft 22 rotates about its axis (i.e., the second longitudinal axis BB). It is rotatably mounted to the frame 20 via an input bearing 28 to the first part of the frame 201 and via an output bearing 29 to the second part 202 of the frame 20 of the transmission module 2. During its rotation, it drives the eccentric body 23, and the first part 231, to which the first finger 241 is mounted via a first series of bearings 251, generates a first reciprocating motion M1 in a first direction S1, while the second part, to which the second finger 242 is mounted via a second series of bearings 252, generates a second reciprocating motion M2 having the same amplitude but simply in the opposite direction (i.e., along the second direction S2). Figure 7b shows the fingers viewed from above, and all the elements shown are the same as those in Figure 7a, except for the bearings which are no longer visible inside. This diagram facilitates the visualization of the translational motion of each of these fingers along the second longitudinal axis BB, and makes it possible to explain why it is more interesting to connect the cutting tool 3 via the blade holder 27 by the first finger 241 and to perform balancing by the counter mass 5 via the second finger 242. In fact, since the cutting tool 3 is located at the end of the cutting tool, it is more natural to place the connecting shoe at this same end, i.e., as far to the right as possible in these diagrams.

[0053] Figure 8 shows a particularly preferred embodiment of the transmission module 2 for carrying out the present invention, the frame 20 of which is provided with an integrated cooling mechanism 7 for the counter mass 5. According to this illustrated embodiment using a long counter mass 5B, it is intended to achieve the most effective balance adjustment possible during the operation of the proposed cutting device and to best ensure connection to the handpiece 4 via the micromotor connection hole 21, the rotational motion R of which is shown on the right side of Figure 8, although not shown in this figure. According to the preferred modified form shown, the integrated cooling device 7 advantageously uses the longitudinal connecting element between the first frame portion 201 and the second frame portion 202 (i.e., cylindrical beams forming parallel axial guide elements 26) by incorporating an integrated cooling duct. Thus, as can be seen by the dotted line in Figure 8, the first axial guide rail 261 is provided with a first integrated cooling duct 2610, and similarly, the second axial guide rail 262 is provided with a second integrated cooling duct 2620. Therefore, the fluid supply duct 71 can be positioned directly at the end of the frame near the micromotor and can be used directly for the supply of physiological fluids, for example, replacing the irrigation channel 61 shown in Figure 3. According to the preferred embodiment in this figure, two channels are used for the cooling duct, but it will be understood that such a configuration is merely sufficient and not essential for the implementation of the present invention, and that it is also conceivable to use only a single cooling duct integrated with an axial guide element 26 which includes only a single guide rail.

[0054] If one or more supply channels are realized inside the guide rail of the counter mass 5, these become irrigation tubes, which have two particularly interesting advantages at the operational level. The irrigation fluid allows for localized cooling of the friction zone of the countermass 5, thus enabling the use of heavier countermasses, such as the longer countermass shown in Figure 8, and thus enabling the use of longer and heavier surgical blades. Typically, connecting an irrigation line is close to the surgeon's fingers and work area, and carries the risk of accidentally disconnecting the line. However, irrigation of cutting tools via an internal mechanism eliminates the need to connect the irrigation line to the blade holder.

[0055] Therefore, this solution significantly improves the surgeon's ergonomics and patient safety, while also increasing flexibility in adjusting tools as needed.

[0056] Furthermore, according to a preferred embodiment for carrying out the present invention, the weight of the counter mass 5 is between a minimum value, which depends on the disengagement force between the motor, workpiece, and hand, the maximum reciprocating frequency of the cutting tool 3, the travel length D of the cutting tool as shown in Figure 3, and the mass of the cutting tool 3-blade holder 27, and a maximum value, which depends on the cooling capacity of the microsaw / handpiece 4 and the gripping diameter of the cutting tool. Thus, the weight of the counter mass is not necessarily equal to the weight of the assembly driven to reciprocate motion together with the cutting tool.

[0057] These constraints are formulated in equation (1), which takes the fundamental equations of mechanics according to a model based on a system embodied in the physical laws of point mechanics. In particular, the mass Mc of countermass 5 must be greater than the limit value defined by equation (1).

number

number

number

number

[0058] Equation (1) above ensures that the cutting tool 3 is not accidentally disconnected from the motor module (i.e., the workpiece corresponding to the micromotor 10) during various working conditions. For this purpose, the maximum acceleration of the system is calculated and estimated from an equation that shows that the sum of the forces applied to the system is equal to the mass multiplied by the acceleration.

[0059] Modeling the blade holder 27 and cutting tool 3 on the one hand, and the counter mass 5 on the other, as a point mass, is justified by the assumption that the solid components are subjected to high-frequency vibrations with very small amplitudes, and therefore the low-frequency dynamic behavior is essentially given by the movement of the center of mass. Since the only active degree of freedom consists of longitudinal movement along the axial guide member 26 (preferably formed by the two axial guide rails 261, 262), there is no rotational driving effect that requires considering the position of the center of mass relative to the possible pivot center.

[0060] Therefore, the mass of counter mass 5 must be lower than the limit defined by the thermal balance of the microsaw, but it is not necessary to configure an automatic equilibrium system in which equation (2) is strictly observed.

number

[0061] The thermal output generated by the reciprocating motion of the counter mass 5 on the guide elements 26 (e.g., the first guide rail 261 and the second guide rail 262 parallel to the transmission axis (i.e., the second longitudinal axis BB)) is particularly related to the following factors: (i) The outer surface and material of the microsaw cap (cooling which is essentially dependent on convection around the handpiece 4). (ii) The diameter of the handle of the microsaw, which determines the maximum diameter of the counter mass 5, and therefore the maximum diameter of the lever arm between the center of gravity of the counter mass 5 and the first transmission finger 241 of the reciprocating motion. (iii) Frequency f and travel length D of the reciprocating motion. (iv) The distance between the axes of the guide rails 261 and 262 of the counter mass 5 and the transmission axis of the reciprocating motion, such as the second longitudinal axis BB of the transmission shaft 22.

[0062] Therefore, a heavier counterweight, such as a longer countermass 5A, allows for more secure retention of the micromotor module 10 by the handpiece 4 equipped with the transmission module 2. However, this increases the lever arm between the center of gravity of the lever arm and the second transmission finger 242, and therefore, in order to minimize the length of the handpiece 4, it is preferable that the countermass 5 occupies all of the free space inside the handle (i.e., its outer casing that the dentist grips). This illustrates the specific shape of the short countermass 5B in Figure 3 and the specific shape of the long countermass 5A in Figure 4, whose cross-section substantially corresponds to a truncated cylindrical ring, if guide holes are ignored. Therefore, the longer the countermass 5, the closer its center of gravity is to the central axis of the handle, while the end of the second transmission finger 242 that drives the countermass 5 is preferably as far away from the center of the handpiece 4 as possible in order to maximize the travel length of the reciprocating motion applied to the countermass 5.

[0063] International standards specify the maximum temperature that the microsaw can reach (currently 55°C under normal use), which allows us to estimate the maximum thermal output that can be generated by the presence of the counter mass 5. The counter mass 5 is preferably made of a metallic material such as bronze, copper, steel, or precious and heavy metals, and has a density exceeding 7,000 kg / m3, thus allowing us to obtain sufficient mass without requiring a volume that is too large and cumbersome for the rest of the transmission module (especially the motion chain for driving the cutting tool 3 itself).

[0064] According to the preferred embodiment described using the previous figure, the fact that there is a counter mass guided by at least two guide rails makes it possible to reduce friction and heating.

[0065] In one particularly advantageous embodiment, the mass of the counter mass 5 according to the present invention is 25% to 50% of the total mass of the cutting tool 3 / blade holder 27 assembly, further minimizing additional heating due to automatic balancing. More preferably, the mass of the counter mass 5 according to the present invention is 2.5g to 6g, and the mass of the cutting tool is 1 to 3 grams.

[0066] Therefore, according to the present invention, an effective means is proposed for offsetting the displacement of the center of mass of the cutting tool with a countermass, which is, It is unrelated to operating speed, Minimizing dependence on the mass and shape of the microsaw components being balanced, Minimizing the impact on the average efficiency of the handpiece (conversion from rotational motion to reciprocating motion), Minimize the impact on bearing wear rate, Without causing the handpiece to overheat, As shown in Figure 1, modular physical separation is possible between the mechanical handpiece 4 (a module that forms a microsaw that does not require a power supply) and the output motor, such as the micromotor 10 also shown in Figure 1, and thanks to a cutting force of approximately 30N (3kg), it is ensured that connecting and disconnecting the surgical cutting tool and the motor is easy and quick.

[0067] According to the preferred embodiment described, the presence of a countermass and a "symmetrical" transmission system of rotational motion to the countermass and blade makes it possible to reduce vibration. Since the countermass moves in perfect phase with the blade, vibration reduction is guaranteed regardless of the motor's rotational speed. Guiding the countermass also avoids the heat and wear that could occur by adding heavy components to the transmission chain. Wear can be reduced by doubling the number of ball bearings for each transmission finger. Furthermore, the inverse dependence of efficiency on motor power input (in unbalanced systems, efficiency decreases with increasing power) can be reduced, and thus cutting efficiency can be increased.

[0068] While only a few embodiments have been described above as examples, it will be understood that these are not intended to be an exhaustive description of all possible embodiments. Those skilled in the art will understand that it is possible to replace the described means with equivalent means without departing from the scope of the present invention.

[0069] Furthermore, without departing from the scope of the present invention, it is also possible to modify the shape of the countermass via an electronic or electromagnetic device depending on the geometric shape of the cutting tool and blade holder used. A preferred embodiment for implementing such a solution is, for example, connecting the two parts of the countermass via an electromagnetic device (of the electromagnet type) placed in one of the two parts of the countermass and a magnet placed in the second part of the countermass. Thus, by changing the polarity of the electromagnet, it becomes possible to attract (magnetic attraction) or separate (magnetic repulsion) the two parts of the countermass. When using a heavier cutting tool, the user can force the two parts together into one ("heavy" countermass), while when using a lighter cutting tool, the user can exert a repulsive force between the two parts of the countermass, and therefore a lighter countermass can be used.

Claims

1. A surgical or dental cutting device (1) comprising a handpiece (4) equipped with a transmission module (2) for a cutting tool (3), and a motor (10) detachably connected to the handpiece (4), wherein the transmission module (2) is A motor coupling section configured so that the rotation is set by the motor (10), A motion chain that converts the rotational motion of the motor (10) into a first linear reciprocating motion (M1) of the blade holder (27) via a rotational transmission shaft (22) equipped with an eccentric body (23), In the cutting device (1) comprising, The transmission module (2) further comprises a counter mass (5) arranged to move in synchronization with the first linear reciprocating motion (M1) of the blade holder (27) and in accordance with a second linear reciprocating motion (M2) in the opposite direction to the first linear reciprocating motion (M1). The counter mass (5) is axially guided along a first transmission axis (A-A) that vectorially corresponds to the direction of longitudinal displacement of the blade holder (27) and the cutting tool (3) by at least one axial guide element (26) inserted into at least one guide hole (52) formed in the counter mass (5), The axial guide element (26) is formed by a first axial guide rail (261) and a second axial guide rail (262) connected parallel to a second portion (202) of the frame (20) that supports and axially guides the blade holder (27) of the transmission module (2) to the first portion (201) of the frame (20) connected to the motor (1), and the first axial guide rail (261) and the second axial guide rail (262) are inserted into the respective guide holes (52) of the counter mass (5), characterized in that the surgical or dental cutting device (1).

2. The surgical or dental cutting device (1) according to claim 1, wherein the geometric shape of the counter mass (5) is adapted to the geometric shapes of the cutting tool (3) and the blade holder (27).

3. The surgical or dental cutting device (1) according to claim 1 or 2, characterized in that the transmission module (2) further comprises a cooling device (7) for the counter mass (5).

4. The surgical or dental cutting device (1) according to claim 3, characterized in that the first axial guide rail (261) is provided with a first integrated cooling duct (2610), and / or the second axial guide rail (262) is provided with a second integrated cooling duct (2620).

5. The surgical or dental cutting apparatus (1) according to any one of claims 1 to 4, characterized in that the transmission module (2) is detachably connected to the motor (10), and the weight of the counter mass (5) is determined to be greater than a minimum value defined in relation to the total weight of the assembly formed by the blade holder (27) and the cutting tool (3), as a function of the disconnection force (Fd) of the transmission module (2) to the motor (10), the travel length (D) of the cutting tool (3), and the oscillation frequency (f) of the reciprocating motion of the cutting tool (3).

6. The surgical or dental cutting device (1) according to any one of claims 1 to 5, characterized in that the weight of the counter mass (5) is determined to be less than a predetermined value determined by the heat balance.

7. The surgical or dental cutting device (1) according to claim 5, or claim 6, which references claim 5, characterized in that the weight of the counter mass (5) is in the range of 25% to 50% of the total weight of the assembly formed by the blade holder (27) and the cutting tool (3).

8. The density of the counter mass (5) is 7000 kg / m³. ３ A surgical or dental cutting device (1) according to any one of claims 3 to 7, characterized in that it is larger than [a certain value].

9. The motor connecting portion of the transmission module (2) is characterized by comprising a grooved connecting hole (21) that cooperates with a standard connecting nose (11) of the motor (10), which has a series of grooves (110) into which an O-ring (111) is inserted, as described in any one of claims 1 to 8, for surgical or dental cutting device (1).

10. A handpiece (4) comprising a transmission module (2) for a surgical or dental cutting device (1) according to any one of claims 1 to 9.

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