Method and system for controllable adjustment of the removal rate of cutting edges of effectors of manually-guided material- and tissue-sectioning tools and a corresponding effector

Abstract

Methods, systems and tools are provided for controllable adjustment of a removal rate of cutting edges of rapidly rotating effectors of manually-guided material- and tissue-separating tools without significantly changing the rotation speed of the effectors or the position, orientation or the geometry of the effectors, and in particular, for precisely maintaining work space boundaries during material and tissue removal with effectors in rapidly rotating machine tools in surgery and freehand manufacturing to produce free-form surfaces. The manually-guided material-separating and tissue-separating tools and effectors allow controllable adjustment of the removal rate of the material-separating cutting edges of the effector by mechanically adjusting a position or orientation of at least one cutting edge cover at a constant rotation speed of the effector without appreciable change of the removal movement.

Claims

1. A method for signal-based or position-based control of a removal rate of material-separating cutting edges of a manually-positioned or manually-guided material separating tool, the manually-positioned or manually-guided material separating tool including an effector and a shaft, the effector including the material-separating cutting edges and at least one cutting edge cover disposed on the material-separating cutting edges, the method comprising: controlling the removal rate of the material-separating cutting edges of the effector by: (a) mechanically adjusting at least two positions of at least one of the material-separating cutting edges or the at least one cutting edge cover disposed on the material-separating cutting edges in a radial direction relative to the shaft, the at least two positions including locations and orientations of the material-separating cutting edges or of the at least one cutting edge cover; or (b) retracting and deploying at least one of the material-separating cutting edges in the radial direction relative to the shaft; and maintaining or only insignificantly changing a rotation speed of the effector: (i) when the at least two positions of the at least one of the material-separating cutting edges or the at least one cutting edge cover are adjusted, or (ii) when the at least one of the material-separating cutting edges are retracted and deployed; the method further comprising least one of: maintaining a position and an orientation of the effector or changing the position and the orientation of the effector only in an order of a magnitude of a cutting length of the material-separating cutting edges when the material-separating cutting edges or the at least one cutting edge cover are mechanically adjusted, and maintaining a spatial extent of the effector or changing the spatial extend of the effector only in the order of the magnitude of the cutting length of the material-separating cutting edges or in an order of a magnitude of a length of the at least one cutting edge cover when the material-separating cutting edges or the at least one cutting edge cover are mechanically adjusted.

2. The method according to claim 1, further comprising: continuously measuring a position of the manually-positioned or manually-guided tool; and controlling the removal rate of the material-separating cutting edges based on the continuously measured position of the manually-positioned or manually-guided tool.

3. The method according to claim 1, wherein energy required to maintain a signal connection for the signal-based control of the removal rate and to control an actuator is obtained directly from kinetic energy or from a drive of a movement of the manually-positioned or manually-guided material separating tool.

4. The method according to claim 1, further comprising: pressing the material-separating cutting edges and the at least one cutting edge cover that rotate with a removal speed outwardly by an internal stator by way of at least one adjustable actuating lamella, so as to only release a subset of the material-separating cutting edges for removal and to limit a movement of the manually-positioned or manually-guided material separating tool to a movement in a removal direction relative to a location of the internal stator or of the tool measuring marker, determining a position of the internal stator relative to the tool measuring marker, and controlling the removal rate of the material-separating cutting edges of the effector as a function of the removal direction by the mechanically adjusting of the at least two positions of the at least one of the material-separating cutting edges and the at least one cutting edge cover.

5. The method according to claim 1, further comprising: visually, acoustically or graphically signaling a setting of a removal direction of the effector on the manually-positioned or manually-guided material separating tool.

6. The method according to claim 1, further comprising: calculating an optimal removal direction for a material processing to be performed by a calculation rule, and automatically setting the optimal removal direction for the material processing.

7. The method according to claim 1, further comprising: calculating a disturbance by an electromagnetic coordinate measuring system based on data obtained from a rotation speed sensor and including the disturbance in a position measurement.

8. A system for signal-based or position-based control of a removal rate of material-separating cutting edges of a manually-positioned or manually-guided material separating tool, the system comprising: an effector including the material-separating cutting edges and a shaft, the material-separating cutting edges being configured to be mechanically adjustable in at least two positions in a radial direction relative to the shaft of the effector to control the removal rate of the material-separating cutting edges, the at least two positions including locations and orientations of the material-separating cutting edges, wherein the effector is configured to at least one of: maintain a position and an orientation of the effector or change the position and the orientation of the effector only in an order of a magnitude of a cutting length of the material-separating cutting edges when the material-separating cutting edges are mechanically adjusted, and maintain a spatial extent of the effector or change the spatial extend of the effector only in the order of the magnitude of the cutting length of the material-separating cutting edges when the material-separating cutting edges are mechanically adjusted.

9. The system according to claim 8, wherein the effector includes at least one of a deployment mechanism, a retraction mechanism, and at least one cutting edge cover arranged on the material-separating cutting edges, and the at least one cutting edge cover being configured to be mechanically adjustable in the at least two positions relative to the effector to change the removal rate of the material-separating cutting edges.

10. The system according to claim 8, further comprising: a cutting edge control attachment; a control computer; a rotation speed sensor; and measuring markers.

11. An effector for a manually-guided tool, comprising: a shaft; and material-separating cutting edges, wherein the cutting edges are deployable and retractable by a cutting edge deployment mechanism and a cutting edge retraction mechanism in a radial direction relative to the shaft, wherein the cutting edge deployment mechanism includes a two-piece wedge structure directly connected with the cutting edges or swivel joints by which the material-separating cutting edges are mounted on an outer surface of the effector, and wherein the cutting edge deployment mechanism is operated by the two-piece wedge structure or by twisting the cutting edge deployment mechanism.

12. The effector according to claim 11, wherein the cutting edge retraction mechanism is operated by spring elements connected to the cutting edges.

13. The effector according to claim 11, further comprising: cutting edge covers, wherein the shaft is a hollow shaft and the cutting edges are immovably affixed to the hollow shaft, and the cutting edge covers are configured to be adjustable in the radial direction relative to the material-separating cutting edges.

14. The effector according to claim 11, further comprising cutting edge covers and actuating lamellae, wherein: the material-separating cutting edges are connected with the cutting edge covers by cutting edge cover joints, and the actuating lamellae are configured to adjust positions of the cutting edge covers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments will now be described with reference to the drawings.

(2) FIG. 1 is a schematic view illustrating a handheld tool with a rotating material-separating effector according to an exemplary embodiment,

(3) FIG. 2 is a schematic view illustrating a dimensionally stable and positionally accurate cavity to be milled in an object with a sensitive structure hidden underneath according to an exemplary embodiment,

(4) FIG. 3 is a block diagram of a material-separating effector with tool edges that can be retracted and deployed at a high rotation speed according to an exemplary embodiment,

(5) FIG. 4 is a block diagram view of a cross section through a material-separating effector, illustrating how the cutting edges can be adjusted via articulated joints according to an exemplary embodiment,

(6) FIG. 5 is a block diagram illustrating a transfer of the actuating forces for adjustment of the cutting edges while the tool rotates with the removal rate according to an exemplary embodiment,

(7) FIG. 6 is a schematic view illustrating a signal-, position-, orientation- and distance-dependent control of the tool cutting edges in relation to the machined material or tissue according to an exemplary embodiment, and

(8) FIG. 7 is a block diagram of a cross section through a material-separating effector illustrating how the removal rate of the cutting edges can be reduced by cutting edge covers according to an exemplary embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

(9) FIG. 1 shows a manually-guided power tool 1 of a type used for material separation and/or chip-removing machining such as drilling, milling, sawing, separating and so on. Pneumatic or electric drives are frequently used when high rotation speeds must be achieved for attaining the necessary removal rate according to an exemplary embodiment. The tool 1 transfers the torque for material separation typically by way of a rigid or flexible shaft 3 by which the material separating tool 1 is connected to the actual tool effector 4 by way of a chuck 2. The rotating effector 4 which is matched to the cutting speed is placed on the material 5 or the tissue 5. The cutting edges 6 on the effector 4 hereby cut the material 5 open and remove part of the material 5.

(10) FIG. 2 shows a surface structure into which a precisely fitting cavity 7 is to be milled, without inadvertently damaging a sensitive structure 8 located in the material 5 with the effector 4 embodied as a milling effector according to an exemplary embodiment. The removal rate of the tool 1 and of the effector 4 may be reduced at the planned boundary of the cavity 7 and proximate to the structure 8 to be protected by adjusting the cutting edges 6, without the need to reduce the rotation speed of the tool 1. At most, the rotation speed is slightly reduced. In this way, the change in the rotation speed of the rotating masses of motor and tool 1 does not impart a jerk or shock on the hand holding the tool 1.

(11) FIG. 3 is a side view and a view from below of the material-separating tool 1 with the shaft 3, the effector head of the effector 4 and the adjustable cutting edges 6 according to an exemplary embodiment. The figure shows four cutting edges 6, which can be pushed out and retracted through openings 9 of the effector head of the effector 4. The openings 9 for deploying the cutting edges 6 are designed, so that the cutting edges 6when retractedare unable to remove any material or only an insignificant amount of material even at high rotation speed and with direct contact between the effector 4 and the surface of the material or tissue 5 to be removed. FIG. 3 shows the openings 9 with rounded edges. A retraction mechanism 10 ensures that the cutting edges 6 themselves do not unintentionally cause a material separating effect even at high rotation speed and upon contact, but retract behind the openings 9 for protection. The retraction mechanism 10 in FIG. 3 is embodied by spring elements connecting the cutting edges.

(12) To push the cutting edges 6 from the protective position, a deployment mechanism 11 is required. This deployment mechanism 11 is designed in FIG. 3 as a wedge mechanism, which when depressed exerts a radially acting force on the cutting edges 6, pressing them outwardly into engagement with the material. All elements shown in FIG. 3 rotate as part of the effector head of the effector 4.

(13) FIG. 4 shows another exemplary embodiment of the tool 1 in which the cutting edges 6 are not retracted, but are instead mounted on the outer surface of the effector 4 with swivel joints 12. They can be deployed by applying pressure from the inside to the outside. Preferably, a stop 13 suitably prevents the cutting edges 6 from breaking out. The swivel joints 12 are preferably implemented as flexure joints which can be generated by suitable weakening and/or shaping of the material. The mechanism of the cutting edges 6 is shown here in cross section; however, all elements may extend around a cylindrical core in form of a stretched spiral (helix) similar to a drill bit.

(14) The deployment mechanism 11 in FIG. 4 is not implemented as a wedge, but instead as an articulated joint, and twisting of the deployment mechanism 11 with respect to the shaft 3 causes the cutting edges 6 to be pulled out beyond the cutting edge protection 14. The deployment mechanism may also be twisted by a helical linear movement.

(15) FIG. 5 shows an exemplary embodiment in which actuating forces are transferred for adjusting the cutting edges 6 by way of a cutting edge control attachment 15. The cutting edge control attachment 15 is connected for this purpose either directly with the hand piece of the tool 1 or it is clamped together with the shaft 3 and the cutting edge deployment mechanism 11 with the chuck 2 during the clamping process. A bearing or support 17 is advantageously arranged to decouple the movement of the cutting edge control attachment 15 from the movement of the tool. A bearing or support 18 is also advantageous for decoupling the cutting edge actuating movement from the tool movement and the cutting edge deployment mechanism 11. The actual adjusting movement is achieved with an actuator 16 which is designed in FIG. 5 as a linear motor, for example a piezoelectric motor, but which may also be designed for pneumatic, hydraulic or electrodynamic operation.

(16) The cutting edge deployment mechanism 11 could also be pulled by another bearing, which is not illustrated in FIG. 5. The actuator 16 would then also be able to adjust the cutting edge position in both directions without requiring a separately constructed passive retraction mechanism 10.

(17) FIG. 6 shows machine drive 20, which can be controlled via a power amplifier and/or a motor controller 21 by signals from a control computer 22 according to an exemplary embodiment. The speed settings of the control computer 22 are received via an external signal line 23 or a signal radio link 24, in order to be able to control for example the rotation speed of the machine with a foot pedal (not shown). Likewise, a cutting edge adjusting control 25 of the actuator serves to adjust the cutting edge via the control signal line 19. It is also possible to signal via the signal line 23 or the signal radio link 24 the immediate adjustment of the cutting edges 6, for example when the effector 4 leaves the boundaries of the work space. For measuring the position and orientation of the tool 1, it is known to affix relative to the tool 1 or the machine a measuring marker 27 for a coordinate measuring system (not shown). A second measuring marker 28 is affixed on the material or tissue 5 to be removed of the object to be processed. The resulting information about the relative movement and the boundary of the work space is either processed externally or transmitted to the control computer 22, from where the rotation speed or the position of the cutting edge is then controlled. The measuring markers 27, 28, 30 are in FIG. 6 designed as reflectors for an optical coordinate measuring systems. However, these could also be measuring markers for an electromagnetic coordinate measuring system. In this case, a rotation speed sensor 26 is preferably mounted on the tool 1 in order to receive the frequency of the electromagnetic interference fields at the place of origin and to forward these to the control computer 22 and the coordinate measuring system, where they are filtered out by a band stop filter. Instead of a position-based adjustment of the cutting edges 6 relative to work space boundaries, direct image signal processing of a signaling or imaging system for generating the cutting edge adjustment is also possible. For this purpose, a signaling or imaging system 29, for example a nerve monitor or a multidimensional imaging device is used to capture the signals. It can then be directly recognized in the signal or image whether the cutting edges 6 need to be switched.

(18) FIG. 7 shows another exemplary embodiment in whichin the context of material removalnot the cutting edge 6, but a cutting edge protection 14 with a cutting edge cover region 14a is adjusted by way of an articulated cutting edge cover joint 31 constructed as a swivel joint or flexure joint is adjusted with respect to the cutting edge 6. If needed, the opening between the cutting edge protection 14 and the cutting edge 6 closed. When using otherunillustratedflexure joints between the cutting edge protection 14 and the cutting edge 6, the surface of the effector 4 may be designed to be completely closed in order to prevent particles from entering the effector 4. In FIG. 7 the cutting edges 6 are fixedly and non-adjustably attached on a hollow shaft 32 which rotates with the cutting speed about a centered stator 33 and is preferably supported at two locations in an annular manner. The orientation of the stator 33 relative to the tool 1 or to the tool measuring marker 27 is known. The cutting edge protection 14 is attached directly to the rear of the cutting edge 6 by way of its cutting edge cover joint 31. In the deployed state, the cutting edge cover region 14a covers the cutting edge 6 and also presses during the deployment movement material residues disposed in front of the cutting edge 6 outward. Without inside pressure, the radius-following shaping causes the cover to be pressed into the effector 4, thereby exposing the cutting edges 6. At least one adjustable actuating lamella 34 is disposed in a recess in the stator 33, which can be deployed and retracted from the rotationally symmetric shape of the stator 33 in at least one direction. Other variants for changing the radius of the stator 33 in at least one location are feasible. By deploying the actuating lamellae 34 on the stator 33, the tool 1 loses its removal effect in this direction. When the lamellae 34 are adjusted in all directions, the entire effector 4 will lose its removal rate. When the lamellae 34 are retracted in a deliberate manner, then the effector 4 assumes relative to the tool 1 or the tool measuring marker 27 an adjustable removal rate limited by the orientation. The removal rate of the effector 4 can then be limited to specific angular segments by suitable control with the control computer 22. The actuating lamellae 34 can not only be moved electrically, but also hydraulically or pneumatically. The latter is particularly advantageous for pneumatic drives.

(19) The method allows reducing the removal rate of at least one of the material-removing cutting edges 6 of a manually-guided tool 1 by an adjustment movement of the cutting edges 6 or of a cutting edge protection 14. In this manner, the removal rate of the material-removing effector 4 on the object can be adjusted and reduced with a uniform tool movement. By maintaining the uniform tool movement and a constant rotation speed, only minimal forces or torques are imparted on the hand guiding the tool. The removal rates can be changed very quickly due to the short adjustment paths.

(20) A distinction is made, on the one hand, between signal-based control and, on the other hand, control of the removal rate in dependence of the tool pose (position and orientation).

(21) The following is an exemplary embodiment of the signal-based control: when drilling a hole with an electric drill in a wall of a room, it may be detected by a signaling sensor that an electrical line or a water pipe is located in the direction of the drilling channel which should not be damaged by the drill. In this situation, the removal rate of the drilling tool is immediately reduced, so that the lines are not damaged.

(22) According to another aspect of an exemplary embodiment: when drilling a cavity in the mastoid region of the cranial bone, it is detected by a signaling sensor that a neural pathway or a blood vessel extends through the bone in the direction or in close proximity of the drilling channel which should not be damaged by the drill. In this situation, the removal rate of the drilling tool is immediately reduced, so that the pathway and blood vessel, respectively, are not damaged.

(23) Both embodiments are intended to serve as safety measures which do not require spatial preplanning by the operator/doctor, but where a switching signal is transmitted by an integrated sensor or an external sensor. Under these circumstances, it may in principle be useful to manually increase the removal rate in order to realize a cost-effective tool 1, while a shutdown is then signal-based.

(24) In other situations, it is advantageous to allow a startup operation by way of a signal. In this case, the tool 1 would already be located at exactly the correct position with the correct rotation speed when the removal rate is switched in. The known problem associated with torque transmission via static friction and the resulting change in position with insufficient manual holding force is then eliminated.

(25) An exemplary embodiment of the pose-based control of the tool similar to the performance control from (U.S. Pat. No. 7,346,417) is the following: For introducing an implant support in form of a cavity into a femur for an artificial knee joint, it is necessary to mill a free-form surface into the bone at a specific position and orientation on the bone. Both the access opening and the working angle are hereby severely limited. As soon as the effector 4 of the manually-guided freehand tool 1 is located at the boundary of the allowed work space, the removal rate of the effector 4 is reduced by adjusting the cutting edges 6 or the cutting edge cover 14 without reducing the machine tool power. Because of the largely constant mass inertia due to the constant rotation speed of the machine tool and of the effector 4 of the tool 1, the removal rate can be abruptly changed at the boundary of the allowed work space, without imparting significant force or torque impulses (jerk) on the guiding or positioning hand. As an alternative to an abrupt change in the removal rate, it may be advantageous to adjust the removal rate relative to the distance to the work space boundary in several steps or continuously, in order to achieve a high surface finish at the boundary surfaces.

(26) The following is another exemplary embodiment of the tool-position-based control in conjunction with a direction-controlled removal rate: when drilling a hole with an electric drill in a wall of a room, it may be detected by a continuous position measurement (position/orientation) that the drill is located close to the planned drilling position. In this situation, the removal rate is reduced depending on the direction, so that material is removed only in the direction of the planned drilling position. The drill then slides automatically to the planned drilling position.

(27) The advantages of power control manually-guided freehand machine tools based on position, orientation and distance data has been extensively disclosed in U.S. Pat. No. 7,346,417, so that the applications will not be cited here again. Likewise, coupling of the power control with direct measurement data from nerve monitoring, i.e. the reduction of the removal rate based on effects measured directly on the object with sensors (here a patient's body), which are based on processing of the object, is known.

(28) The adjustment of the removal rate, limited to a reduced number of the cutting edges 6, is advantageous employed when material 5 needs to be removed in narrow working channels in only one direction, for example to produce grooves. The tool 1 then separates the material only in the preset direction.

(29) It is not always obvious to the operator or the surgeon where and in which direction material 5 must still be removed. It is here advantageous when the effective removal rate as a function of the direction can be visually perceived. This can be achieved, for example, by a clearly recognizable coloring of the cutting surfaces the cutting edges 6. The user then sees the coloring always in those directions where a removal rate can be achieved, even when the effector 4 of the tool 1 rotates very fast. It may be useful to install a similar mechanism on the shank of the tool 1 in order to render visible blunt or rounded surfaces instead of the cutting edges 6, which are preferably released by the same mechanism, in order to emphasize the working direction.

(30) It is also known that the position information can not only be calculated based on the evaluation of markers (U.S. Pat. No. 5,389,101), but also directly based on the evaluation of object geometries (U.S. Pat. No. 7,079,885).

(31) It can be advantageous, not only with pneumatic drives, to produce the energy for adjusting the removal rate and for controlling the removal rate directly from the drive power of the tool 1 by electrodynamic means.