Bendable shafts for medical handheld instruments

Abstract

A shaft (1) of or for a medical handheld instrument (3), comprising a distal shaft portion (4) and a proximal shaft portion (2), wherein the end faces (6, 8) of the distal shaft portion (4) and the proximal shaft portion (2) face each other and at least one is set at an angle of incidence not equal to 90° with respect to the respective longitudinal axis of the shaft, such that different shaft shapes are obtained depending on the relative rotational position of the two shaft portions (2, 4).

Description

[Technical field]

[0001] The present disclosure relates to shafts of or for use in medical hand-held instruments.

[0002] In surgical techniques, it is advantageous to bend the distal shaft portion of the shaft of a medical hand-held instrument, so that surgery can be performed in tight spaces, such as spinal surgery. [Background technology]

[0003] Instruments with bendable distal tips have been known for some time in surgical robotics, allowing precise movement of the instruments in tight spaces. However, these instruments do not involve bending of the rotary tool. One example of this is the Da Vinci surgical robot from Intuitive Surgical.

[0004] There are many different types of bendable medical instruments on the market. For example, Human Xtensions has developed a bendable forceps. Using a handheld robotic instrument, the surgeon can convert "rough" hand movements into fine movements at the tip of the instrument. In this instrument, the tip of the instrument can be bent in a flexible area that is about 20 mm long. The flexible area is supported by a kind of plastic stent. The adjustment is made by a wire strand that is guided through the outside of the stent. The disadvantages here are the length of the bend and the highly flexible tip. This flexibility is due to the plastic stent and the wire strand.

[0005] Furthermore, there are already manufacturers of bendable milling handpieces / medical hand instruments. These are mainly used in endoscopic spinal procedures, allowing for minimally invasive techniques as well as easier treatment of structures that are difficult to access in this area. The joint structure of these milling handpieces is a fairly open design, allowing some flexibility in angulation. This means that when pressure is applied to the tip of the milling cutter, the angle changes slightly. Furthermore, the possible angles for these milling handpieces are up to 36°. An example of this is the milling handpiece from Joimax.

[0006] There are cordless screwdrivers with inclined faces. In the field of DIY tools, there are cordless screwdrivers with bendable heads. These have pivot joints similar to the disclosure described below, and the force absorption of the angulation is very good (rigid joint). Depending on the angulation of the rotation plane, angles up to 90° are possible. However, the cordless screwdriver must be adjusted from the outside. Therefore, there is no internal control.

[0007] There are also high-speed milling handpieces / medical hand instruments with curved shafts. Thanks to the interchangeable shafts, the handpieces can be chosen in three variations: 0°, 7.5° and 15° angles. The biggest drawback is the large bending radius to achieve the bend. This takes up a lot of space and limits the options for action in the surgical field. In addition, the angle cannot be adjusted intraoperatively. As the angle is fixed, endoscopic surgery with a curved shaft is not possible, since it cannot be inserted into the straight working channel of the endoscope. Moreover, the maximum angle of 15° cannot be called particularly large.

[0008] Milling cutters with a bendable head are known from the disclosures of DE 102017010033 A1 and US 10178998. Both solutions are realized via a fork joint. Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, the objective of the present disclosure is to overcome the shortcomings of the prior art and provide a shaft for a medical handheld instrument in which the distal shaft portion is bendable during operation and the angle between the distal and proximal shaft portions does not change even under load.

[0010] According to the present disclosure, this problem is solved by a shaft of or for a medical hand-held instrument having the features of claim 1. Advantageous further embodiments of the present disclosure are the subject matter of the attached dependent claims. [Means for solving the problem]

[0011] The present disclosure thus relates to a shaft of or for a medical handheld instrument, comprising a distal shaft portion and a proximal shaft portion, the respective end faces of which are opposed to one another, at least one end face being set at an angle of incidence not equal to 90° with respect to the respective longitudinal axis of the shaft, resulting in different shaft geometries depending on the relative rotational position of the two shaft portions.

[0012] In other words, the shaft has a bendable distal shaft section. Both the distal and proximal shaft sections have inclined ends / end faces relative to the axis of the respective shaft sections. In other words, one end / end part / end face of the distal and proximal shaft sections is chamfered / beveled rather than straight. The chamfered / beveled ends / end faces each have substantially the same angle of incidence. Thus, the chamfers match each other such that the proximal and distal shaft sections form a straight shaft / tube at a certain relative rotational position. If the distal shaft section rotates about its longitudinal axis relative to the proximal shaft section and the proximal shaft section remains stationary, the distal shaft section will necessarily be bent due to the beveled end face / end.

[0013] The above solution has the following advantages: - The distal shaft portion of the shaft is continuously adjustable. - The control of the rotation mechanism is fully integrated into the shaft and can be adjusted via a rotating sleeve at the proximal end of the shaft, which will not be described in detail. - The specially designed pivot joint is extremely stable, operates smoothly and is totally insensitive to external bending forces. This allows very precise positioning of the distal part of the shaft, which is not altered by any cutting forces - a decisive advantage when using robotic control techniques. - High accuracy and low risk of error are the most important issues here.

[0014] The distal shaft of the medical handheld instrument can be bent during operation, i.e., the distal shaft can be bent during surgery, and is securely attached by abutting the angled / slanted end surface of the proximal shaft.

[0015] The medical hand-held instrument preferably comprises a setting dial, a (tilted) proximal shaft part, a distal shaft part which is bendable relative thereto, a flexible milling cutter and a bearing. The proximal shaft part comprises a fixed outer tube, a ring gear (with internal teeth), an eccentric locking bush and a pinion (with external teeth which mesh with the internal teeth of the ring gear) which meshes with the ring gear. The relatively bendable distal shaft part further preferably comprises a flexible transmission element, an adjusting bush with a drive pin and a distal shaft tip part. The distal shaft part is preferably mounted with a bearing in the proximal part. The flexible milling cutter is preferably guided by the proximal and distal shaft parts and is bendable together with the distal shaft part. The adjusting bush is preferably joined to the pinion by a flexible transmission element such that the rotational movement of the pinion is transmitted to the adjusting bush. The adjusting bush transmits rotation to the distal shaft tip part preferably via the drive pin. Rotation of the distal shaft relative to the angled proximal shaft causes the distal shaft to bend.

[0016] According to another preferred feature of the present disclosure, the proximal shaft portion has a ring gear with internal teeth that mesh with the external teeth of the pinion. The proximal shaft portion preferably has a stationary outer tube with an inclined end face. The ring gear is rotatably mounted to the stationary outer tube about its longitudinal axis. The ring gear is preferably operable from the proximal end of the shaft and has internal teeth. The internal teeth mesh with the external teeth of the pinion. In other words, the internal teeth are operatively meshed with the external teeth. As a result, rotation of the ring gear is transmitted to the pinion.

[0017] According to a further preferred feature of the disclosure, the pinion is rotationally connected to an adjusting bush of the distal shaft section by a flexible transmission element. This flexible transmission element is preferably a rotating shaft or a sheet metal (strip) that rotates concentrically about its longitudinal axis or also orbitally (i.e. orbitally). The pinion is joined to the flexible transmission element. This joining can be performed, for example, by welding and / or gluing or other removable or non-removable joining techniques. The adjusting bush is preferably attached to the side of the flexible transmission element that faces away from the pinion. This connection can also be performed by welding or gluing. The flexible transmission element transmits the rotation of the pinion to the adjusting bush.

[0018] According to a further preferred feature of the present disclosure, the adjusting bushing has a drive pin that is positively coupled to the distal shaft tip and transmits rotation of the adjusting bushing to the distal shaft tip. The adjusting bushing is preferably coupled to the distal shaft tip by the drive pin, which transmits rotation of the adjusting bushing to the distal shaft tip, causing the distal shaft tip to rotate. Finally, the distal shaft tip preferably rotates together with the ring gear. Rotation of the distal shaft tip causes the angled end faces of the distal and proximal shaft portions to position relative to one another such that the distal shaft portion is bent.

[0019] According to a further preferred feature of the present disclosure, the proximal shaft portion has an eccentric locking bushing. The eccentric locking bushing is preferably attached to the outer tube. The eccentric locking bushing presses the pinion against a side of the outer tube opposite the eccentric locking bushing. The pinion is preferably on a side of the shaft opposite the direction in which the distal shaft portion bends. The pinion is driven by a ring gear and rotates within the eccentric locking bushing, i.e. the pinion is always located on the outer tube side. The pinion is preferably located on a side opposite the direction in which the distal shaft portion bends, so that the flexible transmission element is away from the flexible milling cutter.

[0020] According to a further preferred feature of the present disclosure, the flexible transmission element is a flexible spring plate, preferably with laterally mounted balls. The flexible transmission element can be configured as a sheet metal / sheet metal moving on a track and rotating irregularly. When the spring plate rotates with the pinion, it does not rotate about its own longitudinal axis, but rotates irregularly about the longitudinal axis of the pinion. As a result, the spring plate is furthest from the flexible milling cutter in the 45° bent position. As a result, the risk of collision is minimized and the shaft construction can be made smaller.

[0021] According to a further preferred feature of the present disclosure, the ball of a flexible spring leaf is received in a spherical receiving groove in the pinion, and a side of the spring leaf opposite the ball is connected to an adjustment bushing.

[0022] According to a further preferred feature of the present disclosure, the ball of the flexible spring leaf is received in a spherical receiving groove of the pinion, and a side of the flexible spring leaf opposite the ball is coupled to the pinion.

[0023] Preferably, the ball is movably accommodated in the receiving groove. The ball is preferably positively fixed in the receiving groove. However, the ball can move in the longitudinal direction of the receiving groove. The receiving groove can be fixed to a pinion or an adjusting bush. On the side of the spring plate opposite the ball, the spring plate is preferably welded or glued to a corresponding part.

[0024] According to a further preferred feature of the present disclosure, the flexible transmission element is a silicon hose. Preferably, the silicon hose is likewise connected to the adjusting bush and the pinion. Preferably, the silicon hose is fixed to the adjusting bush and the pinion by gluing.

[0025] In accordance with another preferred feature of the present disclosure, the flexible transmission element is a flexible metal gaiter having pleats similar to the pleats of an accordion or foot pump, which makes the metal gaiter flexible and expandable.

[0026] According to another preferred feature of the present disclosure, the flexible transmission element is a flexible metal tube, preferably having a recess or gap shape that makes the metal tube flexible.

[0027] Any solution based on metal tubes has the following advantages: - The metal tube has high torsional rigidity and at the same time good bending properties, which allows very precise adjustment and / or stable positioning of the distal shaft. - The torsional rigidity of the gap geometry is achieved by a special arrangement of the gaps. - No backlash as the contour is continuous in the direction of rotation. - Both solutions based on metal tubes can be welded or glued to the adjusting bush or pinion.

[0028] According to another preferred feature of the present disclosure, the bend angle between the proximal and distal shaft portions is twice as large as the incidence angle of the beveled end faces. In the bent state, the beveled end faces are in contact with one another such that the incidence angles are additive. Because the incidence angles of both end faces are the same, the bend angle is twice as large as the incidence angle. This doubling provides a large bend angle without requiring a large incidence angle.

[0029] In accordance with a further preferred feature of the present disclosure, when the bend angle between the proximal and distal shaft portions is at a maximum and the distal shaft portion is rotated further, the angle of incidence decreases again such that the angled end faces are no longer directly perpendicular to one another and the bend angle decreases again as rotation proceeds.

[0030] According to a further preferred feature of the present disclosure, the adjusting bush is made of a plain bearing material, preferably PTFE or POM, and / or is coated with PTFE. The adjusting bush preferably rotates in a receiving hole in the outer tube. Preferably, no other bearings are arranged in the receiving hole. The adjusting bush must therefore slide. Being manufactured from a plain bearing material, the adjusting bush has less friction with respect to the receiving hole.

[0031] According to a further preferred feature of the present disclosure, the distal shaft tip is made of a plastic with good sliding properties, preferably PTFE or POM. If no bearing is fixed between the outer tube and the distal shaft tip, the distal shaft tip must be able to rotate relative to the outer tube. This is ensured by the material selection of the distal shaft tip.

[0032] According to a further preferred feature of the present disclosure, the distal shaft tip is made of a flexible plastic. The distal shaft tip is manufactured to be bendable, which allows the distal shaft tip to form an undercut with the outer tube, which secures the distal shaft tip to the proximal shaft section. During assembly, the distal shaft tip is folded open and secured in place with the outer tube.

[0033] According to a further preferred feature of the present disclosure, the desired angular position is set manually or motorized via a setting dial, preferably located at the proximal end of the hand-held instrument, allowing the user to set the desired angle. For example, the user can turn a small wheel representing the adjustment element, or the user can use a lever, joystick, etc. to set the desired angle.

[0034] According to a further preferred feature of the present disclosure, the bearing is a solid ball bearing. A solid ball bearing reduces friction within the bearing, resulting in less loss when adjusting the angle. Similarly, the play required for smooth adjustment can be minimized, resulting in greater precision of the distal tip.

[0035] According to a further preferred feature of the present disclosure, the roller bearing is a ball bearing having at least three balls, preferably exactly three. Using more than two balls increases the friction of the roller bearing. However, it has the advantage that the roller bearing can be assembled more quickly and is less expensive, since fewer balls need to be filled. [Brief description of the drawings]

[0036] [Figure 1] FIG. 2 shows a shaft according to a first embodiment in the form of a straight shaft. [Diagram 2] FIG. 2 shows a shaft according to a first embodiment, in which the distal shaft portion is angled at 22.5° compared to the proximal shaft portion. [Diagram 3] FIG. 2 shows a shaft according to a first embodiment, in which the distal shaft portion is angled at 45° compared to the proximal shaft portion. [Figure 4] FIG. 2 is a longitudinal cross-sectional view of a straight shaft. [Diagram 5] FIG. 1 shows a longitudinal cross-section of a shaft inclined at 22.5°. [Figure 6] FIG. 2 shows a longitudinal cross-section of a shaft inclined at 45°. [Figure 7] FIG. 13 shows a cross-sectional view of the proximal shaft. [Figure 8] FIG. 13 shows a cross section of a roller bearing disposed between the proximal and distal shaft portions. [Figure 9] FIG. 2 shows an isometric view of a spring plate with balls. [Figure 10] FIG. 2 shows a side view of a spring plate. [Figure 11]FIG. 13 shows a spring plate in a straight shaft. [Figure 12] FIG. 1 shows a spring plate with a shaft tilted at 45 degrees. [Figure 13] FIG. 13 shows a top view of a spring plate in a shaft tilted at 22.5°. [Figure 14] FIG. 13 shows a twisted spring leaf in a 22.5° inclined shaft. [Figure 15] FIG. 13 shows a cross-sectional view of the proximal shaft. [Figure 16] FIG. 1 shows an isometric view of a flexible silicone hose according to a first embodiment. [Figure 17] FIG. 1 shows a side view of a flexible silicone hose according to a first embodiment. [Figure 18] FIG. 13 illustrates an isometric view of a flexible metal gaiter according to a third embodiment. [Figure 19] FIG. 13 illustrates a side view of a flexible metal gaiter according to a third embodiment. [Figure 20] FIG. 13 shows an isometric view of a flexible metal tube according to a fourth embodiment. [Figure 21] FIG. 13 shows a side view of a flexible metal tube according to a fourth embodiment. [Figure 22] FIG. 13 is a longitudinal sectional view of a straight shaft with roller bearings according to a fifth embodiment. [Diagram 23] FIG. 10 is a cross-sectional view of a roller bearing according to a fifth embodiment. [Figure 24] FIG. 13 is a longitudinal cross-sectional view of a straight shaft according to a sixth embodiment. [Diagram 25] FIG. 13 shows a cross-sectional view of a distal shaft portion according to a sixth embodiment. [Figure 26] FIG. 13 shows a shaft according to a seventh embodiment. [Figure 27] 1 illustrates a handheld instrument with a bendable shaft according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Next, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0038] (First embodiment) FIG. 1 shows a shaft 1 of a medical hand-held instrument in the form of a straight shaft. That is, the proximal shaft section 2 of the shaft 1 and the distal shaft section 4 of the shaft 1 are arranged in a straight line or have an angle of 0° with respect to each other. The proximal shaft section 2 is essentially a tube and has at its distal end an end face 6 that is inclined with respect to the longitudinal axis of the shaft. The distal shaft section 4 is likewise approximately tubular. The tube converges towards the distal end to form a tip. At its proximal end, the distal shaft section 4 has an end face 8 that is inclined with respect to the longitudinal axis of the shaft 1. A flexible milling cutter 10 projects from the distal end of the shaft 1. The flexible milling cutter 10 moves along the longitudinal axis of the shaft. It is clear that instead of the flexible milling cutter 10, a drill or other medical tool can project from the shaft 1.

[0039] Each of the inclined end faces 6, 8 has an angle of incidence, preferably 22.5°, relative to a plane perpendicular to the longitudinal axis of the shaft. If the shaft 1 is in the form of a straight shaft or is elongated, the two inclined end faces 6, 8 are offset from one another such that the long sides of the inclined end faces 6, 8 are opposite each other relative to the longitudinal axis. The inclined end faces are in contact with one another. The inclined end faces do not necessarily have to have an angle of incidence of 22.5°. For example, angles of incidence of 10°, 18°, 30°, 45° or other angles of incidence are also possible.

[0040] FIG. 2 shows a shaft 1, in which the distal shaft portion 4 is inclined at 22.5° relative to the proximal shaft portion 2. Compared to the position in FIG. 1, the distal shaft portion 4 is rotated 90° about its longitudinal axis relative to the proximal shaft portion 2. The inclined end faces 6, 8 are not perfect / flat relative to each other. The inclined end face 8 together with the distal shaft portion 4 is rotated 90° relative to the inclined end face 6 of the proximal shaft portion 2, so that the long side of the inclined end face 8 protrudes beyond the inclined end face 6. Due to the angle of incidence of the inclined end face 6, the distal shaft portion 4 protrudes upwards relative to the proximal shaft portion 2. The flexible milling cutter 10 is bent together with the distal shaft portion 4.

[0041] FIG. 3 shows a shaft 1, in which the distal shaft section 4 has an incidence angle of 22.5° for each of the two end faces, and is therefore inclined at 45° relative to the proximal shaft section 2. Compared to the position in FIG. 1, the distal shaft section 4 has been rotated 180° about its longitudinal axis. In this position, the inclined end faces 6, 8 again lie completely / flat against each other. However, due to the rotation of the distal shaft section 4, the long sides of the inclined end faces 6, 8 are now positioned adjacent to each other. The incidence angles of the inclined end faces 6, 8 are therefore additive. As a result, the distal shaft section 4 is inclined by an angle that is twice the incidence angle of the inclined end faces 6, 8 compared to the proximal shaft section 2.

[0042] FIG. 4 shows a cross section of an elongated (straight) shaft 1 through its longitudinal axis. The proximal shaft section 2 has a stationary outer tube 12, a ring gear 14 with internal teeth 16, a pinion 18 with external teeth 20, and an eccentric locking bushing 22. The ring gear 14 is disposed within the outer tube 12, the longitudinal axis of which corresponds to the longitudinal axis of the ring gear 14. Thus, the outer tube 12 and the ring gear 14 are disposed concentrically. The ring gear 14 is coupled to a proximal setting dial (not shown) and rotates together with the setting dial. The user can set the desired angular position on the setting dial. The angular position can be set manually or with the assistance of a motor. The proximal setting dial can also have a locking device (not shown) (e.g. ball pressure element, clamp screw or locking ring) that prevents adjustment of the distal shaft section 4. This ensures that adjustments are only made by active, deliberate action. The outer tube 12 is immobile. The distal end of the outer tube 12 has a beveled end face 6. The distal end of the outer tube 12 further has a receiving hole 24 and a receiving pin for a roller bearing 26. The outer tube has grooves for the balls of the roller bearing 26. The distal shaft portion 4 is attached to the roller bearing 26.

[0043] The internal teeth 16 mesh with the external teeth 20 of the pinion 18. As a result, the rotation of the ring gear 14, which is controlled by the setting dial, is transmitted to the pinion 18. The direction of rotation of the pinion 18 is opposite to that of the ring gear 14. The pinion 18 is driven by the ring gear 14, but the pinion rotates in an eccentric lock bush 22. The lock bush 22 is arranged eccentrically with respect to the ring gear 14. In other words, the longitudinal axis of the eccentric lock bush 22 is parallel to the longitudinal axis of the ring gear 14, but the longitudinal axes of the two do not touch each other.

[0044] The distal shaft section 4 has an adjusting bushing 28 with a drive pin 30 and a distal shaft tip 32. The distal shaft tip 32 is mounted in a roller bearing 26. The adjusting bushing 28 is mounted in a receiving hole 24 of the proximal shaft section 2. The drive pin 30 of the adjusting bushing 28 positively engages the distal shaft tip 32. The adjusting bushing 28 is connected to the pinion 18 via a flexible silicone hose 34 so that the rotation of the pinion 18 is transmitted to the adjusting bushing 28. The flexible silicone hose 34 is a flexible transmission element according to the claims. The flexible silicone hose 34 is fixed to the adjusting bushing 28 and the pinion 18, for example by welding or gluing. Since the adjusting bushing 28 is positively connected to the distal shaft tip 32 via the drive pin 30, the rotation of the adjusting bushing 28 is transmitted to the distal shaft tip 32.

[0045] A flexible milling cutter 10 extends through both the proximal shaft portion 2 and the distal shaft portion 4. The flexible milling cutter 10 is attached to the proximal shaft portion 2 and the distal shaft portion 4 via roller bearings 35, 36. The flexible milling cutter 10 is bendable along with the distal shaft portion 4.

[0046] This arrangement allows for continuous adjustment of the distal shaft portion 4 between 0 and 45 degrees. The full roller bearings 26 allow for smooth, rattle-free adjustment (no stick / slip effect) even when the tip of the instrument is under load.

[0047] To install the shaft 1, first the lock bushing 16 is inserted into the outer tube 12. Then the ring gear 14 with the pinion 18 is inserted into the outer tube. Next, the bearing 34 for the flexible milling cutter 10 is installed and secured with a lock ring. The adjusting bushing 28 with the flexible transmission element 34 is inserted into the receiving hole 24. The roller bearing 26 is placed into the outer tube 12. The distal shaft tip 32 is placed on the roller bearing 26. The drive pin 30 of the adjusting bushing 28 positively engages the distal shaft tip 32.

[0048] FIG. 5 shows a cross-sectional view of a 22.5° inclined shaft 1, with the distal shaft section 4 inclined at 22.5° relative to the proximal shaft section 2. It should be noted that the drive pin 30 is not visible in this cross-sectional view because it rotates with the adjusting bushing 28 and is hidden by the adjusting bushing 28 in this view. The flexible milling cutter 10 twists with the proximal shaft section 2. The distal shaft section 4 moves in a circular orbit to the 22.5° position. The ring gear 14 and pinion 18 rotate in opposite directions.

[0049] It is advantageous for the receiving bore 24, which supports the adjusting bushing 28, to have low friction. This can be achieved by using a plain bearing material (PTFE, POM, etc.) or a coating (PTFE, etc.) for the adjusting bushing 28.

[0050] Figure 6 shows a cross-section of the shaft 1 bent at an angle of 45°. In this position, the drive pin 30 is located opposite the locking bush 22. This means that the adjusting bush 28 with the drive pin 30 has rotated 180° from the extended position to the maximum tilt position.

[0051] The 45° position represents the reversal point of the structure. The adjusting bushing 28 has rotated 180° in this position. Further rotation of the ring gear 14 rotates the distal shaft portion 4 back to the starting position (0° position). Depending on the application, this may be advantageous or unnecessary. In the second case, the result is a reversal of the direction of rotation, returning to the starting position. Since the instrument can rotate 360° about its axis in the working channel of the endoscope, any position can be reached.

[0052] FIG. 7 shows a cross-sectional view of the proximal shaft portion 2. FIG. 7 shows the ring gear 14 with internal teeth 16 in the outer tube 12. A pinion 18 with external teeth 20 meshes with the internal teeth 16. An eccentric lock bushing 22 is fixed to the upper side of the outer tube 12 and is in contact with the pinion 18. As a result, the pinion 18 remains on the lower side of the outer tube 12 even when the ring gear 14 rotates. The lower surface of the outer tube 12 is the surface opposite the eccentric lock bushing 22. That is, the eccentric lock bushing 22 pushes the pinion 18 towards the lower side of the outer tube 12.

[0053] FIG. 8 shows a cross section of the distal shaft section 4 and the roller bearing 26. The roller bearing 26 is preferably a solid ball bearing. By designing the roller bearing 26 as a solid ball bearing, friction in the roller bearing 26 can be minimized. To mount the roller bearing 26, balls 38 are inserted into the groove raceway through the filling opening 40. In order for the rolling elements to roll smoothly, a calculated clearance of one to two balls is advantageous. The filling opening 40 can be closed with a dowel pin, which can be welded permanently.

[0054] Second Embodiment In a second embodiment, the flexible transmission element is realized by a spring leaf 42 with a laterally mounted ball 44. Figure 9 shows the spring leaf 42 in an isometric view. The spring leaf 42 is flexible and has a lateral pin 46 on which the ball 44 is mounted. The pin 46 is either rigidly welded to the leaf 42 or is otherwise connected to the leaf 42 so that it can rotate about its own longitudinal axis.

[0055] In the preferred embodiment, a flexible transmission element is shown. It can be implemented in various forms. A preferred variant is a spring plate 42 with a laterally mounted ball 44, which is particularly stable in position and has a high repeatability. Furthermore, the spring plate 42 requires little space for its laterally mounting and therefore provides more space for the flexible milling cutter 10 to pass through. The flexible transmission element is a flexible spring plate 42 with a laterally mounted pin 46 with a ball end. FIG. 10 is a side view of the spring plate 42. The spring plate 42 is flexible. The spring plate 42 is capable of bending both about an axis perpendicular to the longitudinal axis of the spring plate 42 and about the longitudinal axis of the spring plate 42.

[0056] FIG. 11 shows a spring plate 42 in a straight shaft 1. The ball 44 of the spring plate 42 is shown inserted into an elongated receiving groove 48 in the pinion 18. The receiving groove 48 extends in the longitudinal direction of the shaft 1, and the ball 44 is positively connected to the receiving groove 48. The ball 44 therefore moves with the rotation of the pinion 18 and also moves in the longitudinal direction of the receiving groove 48. The side of the spring plate 42 opposite the ball 44 is fixed to the adjusting bush 28. The rotation of the pinion 18 is therefore transmitted from the spring plate 42 to the adjusting bush 28. The adjusting bush 28 rotates together with the spring plate 42. The spring plate 42 is connected to the adjusting bush 28, for example, by welding or gluing. It should be noted that the receiving groove 48 can also be provided in the adjusting bush 28. In this case, the ball 44 is connected to the adjusting bush 28 and the spring plate 42 is welded or glued to the pinion 18.

[0057] The ball 44 moves in a spherical receiving groove 48 of the pinion 18 in the longitudinal direction of the receiving groove 48. The distal fixation in the adjusting bushing 28 is performed by gluing or welding. The proximal fixation is omitted. Due to the positive fit of the ball 44 in the receiving groove 48, the rotational movement is transmitted to the adjusting bushing 28 via the spring plate 42.

[0058] 12 shows the spring plate 42 in a 45° tilted shaft 1 compared to a straight shaft 1 with the pinion 18 rotated 180° about its longitudinal axis. Naturally, the receiving groove 48 containing the ball 44 has also rotated 180°. The adjusting bush 28 is also rotated via the spring plate 42. The drive pin 30 carries with it the distal shaft tip 32, which also rotates 180°. This clearly shows that the spring plate 42 has a greater distance to the flexible milling cutter 10 in the tilted state than in the extended state.

[0059] 11 and 12 show the position of the ball 44 and the bending of the spring plate 42 in the two end positions. At the 45° position, the spring plate 42 is at the bottom. Together with the eccentric hole in the adjusting bush 28 and the eccentric chamfer of the pinion 18, the clearance for the flexible milling cutter 10 is maximum here. This is the main difference with the variants listed below and can be decisive when miniaturizing the structure.

[0060] FIG. 13 shows a top view of the spring leaf 42, the shaft 1 being inclined at 22.5°. The rotation of the pinion 18 causes the spring leaf 42 to rotate, and with it the adjusting bush 28. This causes the spring leaf 42 to twist. It is shown that the ball 44 moves in the longitudinal direction of the receiving groove 48 when the pinion 18 rotates in the receiving groove 48. FIG. 14 shows the spring leaf 42 and clearly shows that during rotation or during the transmission of the rotary motion from the pinion 18 to the adjusting bush 28, the spring leaf 42 twists about its own longitudinal axis. In the 22.5° position, it becomes clear that the spring leaf 42 has rotated relative to the receiving groove 48 and also twisted about its longitudinal axis. The corresponding flexibility of the spring leaf 42 is a fundamental prerequisite for its functioning.

[0061] 15 is a cross-sectional view of the proximal shaft portion 2 with the eccentric lock bushing 22 and the pinion 18. The ball 44 positively engages with the receiving groove 48 and follows the rotation of the receiving groove 48. From this cross-section, it can be seen that the special receiving groove 48 with a spherical shape ensures that the ball 44 of the spring plate 42 is gripped by a positive fit and must follow the rotational movement of the pinion 18.

[0062] Fig. 16 shows a silicon hose 34 according to a first embodiment. The silicon hose 34 is one way of realizing a flexible transmission element. The ends of the silicon hose 34 are bonded to the pinion 18 and the adjusting bush 28, respectively. Fig. 17 is a side view of the silicon hose 34.

[0063] (Third embodiment) FIG. 18 shows a flexible transfer element according to a third embodiment. The transfer element is a flexible metal gaiter 50. Metal gaiter 50 is essentially a hollow elongated metal tube. In the center, the metal tube has pleats similar to the pleats of a bellows or accordion. The pleats allow metal gaiter 50 to bend or be flexible. Metal gaiter 50 can be attached to pinion 18 and adjustment bushing 28 by gluing or welding. FIG. 19 shows a side view of metal gaiter 50.

[0064] (Fourth embodiment) Fig. 20 shows a flexible transmission element according to a fourth embodiment. The transmission element is a flexible metal tube 52. The metal tube 52 is basically a thin and elongated metal tube. The metal tube 52 has slots / recesses extending in the radial direction of the metal tube 52. In other words, the metal tube 52 has a slit shape. The recesses give the metal tube 52 flexibility. The metal tube 52 can be fixed to the pinion 18 and the adjusting bush 28 by gluing or welding. Fig. 21 is a side view of the metal tube 52.

[0065] Fifth embodiment FIG. 22 shows an elongated shaft 1 according to a fifth embodiment. According to the fifth embodiment, the roller bearing 26 is not a solid ball bearing, but has only three or more than three balls 38. The receiving pin 25 of the outer tube 12 has three ball holes 54. The distal shaft tip 32 has a circumferential groove 56. During assembly, the balls 38 are inserted respectively through the filling openings 40 into the corresponding ball holes 54. Closing of the openings is performed similarly to the first embodiment. The balls 38 roll in their respective ball holes 54. This results in a slightly higher friction, since a rolling movement is only possible in the grooves 56 of the distal shaft tip 32. However, the number of balls 38 required is significantly less and assembly is faster. FIG. 23 shows a cross-sectional view of the distal shaft part 4 and the roller bearing 26. The ball holes 54 are equally spaced in the circumferential direction.

[0066] Sixth embodiment FIG. 24 shows the extension shaft 1 according to the sixth embodiment. In the sixth embodiment, there is no roller bearing between the outer tube 12 and the distal shaft tip 32. Rather, a sliding pair is formed between the outer tube 12 and the distal shaft tip 32. The distal shaft tip 32 is fixed to the outer tube 12 by a rear catch 58. To be able to realize the rear catch 58, the distal shaft tip 32 must be made of a flexible material, for example plastic. For assembly, the distal shaft tip 32 is folded and fits into a protrusion on the outer tube 12. The rotation is transmitted by a lateral drive pin 60, as space is created by the absence of balls. The drive pin 60 protrudes from the adjustment bush 28 and rotates together with the adjustment bush 28. The outer tube 12 has a recess 61 in which the drive pin 60 can move. The drive pin 60 extends through the recess 61 and is connected in a form-fitting manner to a bulge of the distal shaft tip 32.

[0067] If a plastic with good sliding properties (PTFE, POM, etc.) is used, smooth adjustment can be achieved without roller bearings. This variant is particularly suitable for low-cost, single-use instruments.

[0068] 25 shows a cross-sectional view of the distal shaft tip 32. The adjusting bushing 28 has a protruding drive pin 60 that engages the distal shaft tip 32. The drive pin 60 passes through the outer tube 12 through a recess 61. The recess 61 covers half the circumference of the outer tube 12. The drive pin 60 transfers rotation of the adjusting bushing 28 to the distal shaft tip 32.

[0069] Seventh embodiment 26 shows a curved shaft 1 according to a seventh embodiment, where the shaft 1 does not have a cutter but has jaws or scissor blades 62 protruding from the distal shaft portion. A user can grasp or clamp an object with the jaws 62.

[0070] In endoscopic instruments with adjustable angle tips, high frequencies for the movement of the jaws or scissor blades 62 are generally not achieved (<100 actuations / min), so the role of friction in controlling flexibility is secondary.

[0071] In this case, larger angles can be achieved without unacceptably heating the shaft. By cutting at an angle of 45 degrees (instead of 22.5 degrees), angles up to 90 degrees can be achieved (not shown). However, the more elliptical shape of the cut surface leads to a greater lateral protrusion of the shaft edge in the area of ​​the pivot joint (especially in the intermediate position halfway through the adjustment range). This protrusion can be reduced by a specific curvature.

[0072] Theoretically, a retrograde instrument (angle greater than 90 degrees) is also possible, but this design is not useful due to the flat cutting angle and very large projections.

[0073] The special angled head concept allows for a particularly stiff instrument which maintains its position even under high loads.

[0074] The flexible milling cutter 10 can have a special section for the bending area, which on the one hand can withstand the movements of the instrument tip and on the other hand can transmit torque. This can be, for example, a thin wire, a braided strand, a universal joint or the like.

[0075] 27 shows a combination of the shaft 1 with a medical hand-held instrument 3. The shafts of all embodiments are suitable for and can be joined to the medical hand-held instrument 3. [Explanation of symbols]

[0076] 1 Shaft 2 Proximal Shaft 3 Medical handheld instruments 4 Distal shaft section 6, 8 Inclined Ends 10 Flexible Milling Cutter 12 Outer tube 14 Ring Gear 16 Inner teeth 18 Pinion 20 Outer teeth 22 Eccentric lock bush 26 Roller bearing 28 Adjustment bush 30, 60 Drive pin 32 Distal shaft tip 34 Flexible transmission element 38 Ball 42 Spring plate 48 Receiving groove

Claims

**Claim 1**: A shaft (1) for a medical handheld instrument (3), comprising a distal shaft portion (4) and a proximal shaft portion (2), wherein the end faces (6, 8) of the distal shaft portion (4) and the proximal shaft portion (2) face each other, at least one of the end faces (6, 8) is set at an incident angle not equal to 90° with respect to the longitudinal axis of each shaft, and different shaft shapes are obtained according to the relative rotational positions of the two shaft portions (2, 4). The shaft (1), characterized in that a pinion (18) of the proximal shaft portion (2) is connected by a flexible transmission element (34; 42; 50; 52) to an adjustment bush (28) of the distal shaft portion (4) so as to transmit rotation. **Claim 2** The shaft (1) according to claim 1, characterized in that the incident angles are equal, and a straight or bent shaft shape is obtained according to the relative rotational positions of the two shaft portions (2, 4). **Claim 3** The shaft (1) according to claim 1 or 2, characterized in that the proximal shaft portion (2) has a ring gear (14) having internal teeth (16) meshing with external teeth (20) of the pinion (18). **Claim 4** The shaft (1) according to claim 1, characterized in that the adjustment bush (28) is positively connected to the distal shaft tip (32) and has a drive pin (30; 60) for transmitting the rotation of the adjustment bush (28) to the distal shaft tip (32). **Claim 5** The shaft (1) according to claim 1, characterized in that the proximal shaft portion (2) has an eccentric locking bush (22). **Claim 6** The shaft (1) according to claim 1, characterized in that the flexible transmission element is a flexible spring plate (42) having a laterally mounted ball (44). **Claim 7** The shaft (1) according to claim 6, characterized in that the ball (44) of the flexible spring plate (42) is received in a spherical receiving groove (48) of the pinion (18), and the side surface of the flexible spring plate (42) opposite to the ball (44) is connected to the adjustment bush (28). **Claim 8** The ball (44) of the flexible spring plate (42) is received in the spherical receiving groove (48) of the adjustment bush (28), and a side surface of the flexible spring plate (42) on the side opposite to the ball (44) is connected to the pinion (18). The shaft (1) according to claim 6, characterized in that.

9. The shaft (1) according to claim 1, characterized in that the flexible transmission element is a silicone hose (34).

10. The shaft (1) according to claim 1, characterized in that the flexible transmission element is a flexible metal gaiter (50).

11. The shaft (1) according to claim 1, characterized in that the flexible transmission element is a flexible metal tube (52).

12. The shaft (1) according to claim 1, characterized in that the bending angle between the proximal shaft portion (2) and the distal shaft portion (4) is twice the size of the incident angle of the inclined end faces (6, 8).

13. The shaft (1) according to claim 1, characterized in that the bending angle between the proximal shaft portion (2) and the distal shaft portion (4) is maximum, and the incident angle becomes smaller again with further rotation of the distal shaft portion (4).

14. The shaft (1) according to claim 1, characterized in that the adjustment bush (28) is made of a sliding bearing material and / or is coated with PTFE.

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