Screwdriver tool and assembly method using the screwdriver tool

Abstract

The present disclosure relates to a driving tool (1) for driving a screw (2) having a first tool shank (4) with an end thread engagement portion (8) arranged and designed for transmitting torque to the screw (2) and a second tool shank (5) arranged and designed for transmitting a compressive force axially to the screw (2) in a direction towards the first tool shank (4), the second tool shank (5) being oriented or oriented axially opposite the first tool shank (4) such that its end thread engagement portion (9) is axially opposite the end thread engagement portion (8) of the first tool shank (4). The present disclosure further relates to an assembly method for driving a screw (2) using the driving tool (1).

Description

[Technical field]

[0001] The present disclosure relates to a driving tool for transmitting torque to a screw. Furthermore, the present disclosure relates to a driving tool and preferably an assembly method including the driving tool. [Background technology]

[0002] In order to screw a screw into an internal thread, for example to rigidly connect two branches of a medical instrument to one another or, in particular, to allow them to move relative to one another, for example pivotally, it is necessary to apply a torque to the screw. This torque can be transmitted to the screw in a form-fit and / or a force-fit (i.e. frictional engagement), in particular by a screwdriver tool. The torque transmitted to the screw by the screwdriver tool must overcome the thread friction forces acting between the screw and the internal thread.

[0003] Such a screwing tool is known, for example, from US 2009 / 0 229 846 A1. Furthermore, an assembly method for screwing in screws is known, for example, from EP 2 873 381 A1.

[0004] For press fit torque transmission, the thread is subjected to an axial pressure / compression force by the screwdriver tool to generate a surface friction force between the screwdriver tool and the thread, and when the screwdriver tool is rotated, the friction torque resulting from the surface friction force is transmitted to the thread. If the friction torque between the screwdriver tool and the thread is smaller than the torque resulting from the thread friction force, the screwdriver tool will slip and the thread will not be screwed in. This may cause the screwdriver tool to slip and damage the surface of the thread or the part with the female thread.

[0005] The higher the axial pressure applied to the thread by the driving tool, the greater the surface friction force and resulting friction torque that can be transferred from the driving tool to the thread. However, since the axial pressure applied to the thread also acts on the female thread, the thread friction force increases as the axial pressure increases, and it is not possible to simply increase the axial pressure to increase the friction torque that can be transferred from the driving tool to the thread in frictional engagement. Summary of the Invention

[0006] It is therefore an object of the present disclosure to provide a screwdriver tool with which screws can be particularly easily and reliably driven in. In addition, a suitable assembly method using the screwdriver tool, and preferably this screwdriver tool, is provided.

[0007] The object of the disclosure is solved by a screwdriver tool having the features of claim 1 and by an assembly method having the features of the independent claims. Advantageous further developments are the subject matter of the dependent claims.

[0008] More precisely, the screwdriving tool has a first tool shank, preferably with a larger shank diameter, and a second tool shank, preferably with a smaller shank diameter. Larger or smaller shank diameter is here understood to mean that the shank diameter of the first tool shank is larger than the shank diameter of the second tool shank. Preferably, the larger shank diameter corresponds approximately to the diameter of the screw head, whereas the smaller shank diameter preferably corresponds approximately to the diameter of the screw shank or the diameter of the screw core, or is smaller than the screw core diameter.

[0009] The first tool shaft has an end thread / head engaging portion arranged and configured to transmit torque to the screw, in particular to the screw head of the screw. Preferably, the end thread / head engaging portion of the first tool shaft may be rotatable and arranged and configured to transmit a compressive force in an axial direction to the screw, in particular to the screw head. Thus, a friction torque (between the first tool shaft and the screw) resulting from a compressive force during rotation of the first tool shaft can be transmitted from the first tool shaft to the screw.

[0010] The second tool shank has an end thread / shaft engagement portion that is configured to transmit an axial compressive force to the thread, particularly to the thread / shaft end of the thread opposite the head of the thread, and is axially orientable or oriented with respect to the first tool shank in a direction opposite the first tool shank such that the end thread engagement portion of the second tool shank is axially opposite the end thread engagement portion of the first tool shank, and is configured to transmit a compressive force axially to the thread in a direction toward the first tool shank.

[0011] In other words, the substantially punch-shaped first tool shaft and the substantially punch-shaped second tool shaft have a common longitudinal axis and are axially spaced from each other such that the threaded engagement portion of the first tool shaft faces the threaded engagement portion of the second tool shaft. Thus, the thread can be arranged in longitudinal alignment between the first tool shaft and the second tool shaft. Furthermore, since the second tool shaft is displaceable along its longitudinal axis towards the first tool shaft, a compressive force acting axially towards the first tool shaft can be transferred to the thread and thus from the thread to the first tool shaft. As a result, the force acting between the threaded engagement portion of the first tool shaft and the thread corresponds to the sum of the compressive forces that can be applied by the first tool shaft and the second tool shaft, respectively, directed towards the opposite / opposing tool shaft.

[0012] Thus, the essence of the present disclosure is that a screwdriving tool is provided and configured such that the screw can be axially clamped between a first tool axis and a second tool axis. This has the advantage that the axial pressure acting between the screwdriving tool and the screw can be increased while bypassing the female thread (and thus avoiding increased thread friction torque). In simple terms, the normal force acting on the surface of the screw, and in particular on the screw head, increases, while the axial force acting on the screw (as a whole) in the direction of the second tool axis remains unchanged or is compensated by the compressive force of the second tool axis.

[0013] In further words, a screwdriving tool according to the present disclosure has two separate tool shafts (coaxial) extending axially (on a common axis) from each other, and a common tool shaft support frame on which the tool shafts are (preferably rotatably) held and are axially movable towards each other to axially clamp a screw between them (closed force flow via the tool shaft support frame, the two tool shafts and the screw clamped between them). The clamping force that can be axially applied to the tool shafts via the tool shaft support frame (via a compression force device of the tool shaft support frame) is preferably adjustable (manually or automatically) (e.g. via a pretension spring, hydraulic / pneumatic ram or clamping screw) such that a frictional force is generated between at least one screw head tool shaft (or a thread-engaging portion thereof) and the screw, allowing a certain screwing torque to be transmitted to the screw (from the screw head tool shaft or both tool shafts).

[0014] This has the advantage of giving freedom with regard to the design of the screw, in particular the shape of the screw head, since the screw can be screwed in only or at least mainly by force transmission by frictional engagement with the screw-driving tool according to the present application. In particular, the screw head can preferably be formed with a flat / unprofiled surface, so that essentially only frictional forces can act between the screw head and the (likewise preferably unprofiled / no form-fitting) thread-engaging part of the screw head tool shaft, which in particular makes it possible to avoid disadvantages resulting from the often angular outer or inner profile-sinking of the screw head, which is necessary for force transmission by form-fitting. Preferably, the screw head can be configured essentially rotationally symmetrical, thus making it possible to avoid the formation of gaps, slits, pockets, etc., which cannot reliably and completely remove tissue residues, dirt and body fluids during reprocessing of the instrument.

[0015] According to a preferred embodiment, the thread-engaging portion of the first tool shaft may have a substantially concavely curved, in particular spherical (smooth / no die-sinking) surface or a frusto-conical surface. The thread-engaging portion of the first tool shaft may preferably be provided and configured such that the shape of the thread-engaging portion substantially corresponds to the shape of the screw head. That is to say, the screw head preferably has a substantially convexly curved, in particular spherical (no die-sinking) surface. Alternatively or additionally, according to a preferred embodiment, the thread-engaging portion of the second tool shaft may have a substantially flat or concavely curved, in particular spherical (no die-sinking) surface. The thread-engaging portion of the second tool shaft may preferably be provided and configured such that the shape of the thread-engaging portion corresponds to the shape of the screw head. This means that the threaded end preferably has a substantially flat or convexly curved, in particular spherical surface. This allows advantageous guiding and centering of the first tool shaft and / or the second tool shaft. This means that self-centering takes place during the assembly or clamping process of the screw between the tool shafts preferably spaced apart in the axial direction. A further advantage of the soft edges / curved surfaces of the first and / or second tool shaft is that damage can be avoided when the screwdriver tool slips off and therefore remachining of the threads required to ensure the surface quality required for medical, especially surgical, instruments / devices can be avoided.

[0016] According to a preferred embodiment, the present disclosure relates to a screw driving tool including a screw configured to receive a torque from a threaded engagement portion of a first tool shank and a compression force from a threaded engagement portion of a second tool shank. In particular, the screw may have a substantially spherical (or rounded) head.

[0017] According to a preferred embodiment, the screw driving tool may have a clamping device (a part that clamps the screw between the axially spaced tool shafts of the tool shaft support frame / tool ​​shaft holding device). The clamping device may preferably be provided and configured to set the rotation angle and / or torque of the thread-engaging part of the first tool shaft. Alternatively or additionally, the clamping device may preferably be provided and configured to measure the rotation angle and / or torque of the thread-engaging part of the second tool shaft. It is thus possible to adjust how far and / or how tightly the screw is screwed (into the medical instrument), i.e. which turns of the thread of the screw are in threaded engagement and / or in particular how large the section modulus resulting from the threaded connection of two components of the surgical instrument that are movably / pivotably connected via the threaded connection is. That is, the clamping device may be used in the manner of a slip clamp to prevent over-tightening of the screw being screwed.

[0018] According to a preferred embodiment, the screwdriving tool may have a compression force device (a further part of the tool shaft support frame / tool ​​shaft holding device) (as shown above). The compression force device is preferably arranged and configured to set, calculate and / or measure a compression force (axially from the second tool shaft towards the first tool shaft on the screw and / or axially from the first tool shaft towards the second tool shaft on the screw). In other words, the compression force device is preferably arranged and configured to set, calculate and / or measure an axial clamping force of the screwdriving tool acting on the screw. In particular, the compression force device may be configured such that the axial distance between the first tool shaft and the second tool shaft is changeable / adjustable, for example via a screw drive against the restoring force of a spring. The axial clamping force / axial compression force can thus be determined depending on the length of the screw clamped in the screwdriving tool. The compression force device may be operated manually or, preferably, automatically.

[0019] According to a preferred embodiment, the first and second tool shafts can be held axially movable relative to one another, preferably pivotally or axially displaceable, so that the threaded engagement parts can be moved towards and away from one another in a simple manner, for example like a press or pliers.

[0020] According to a preferred embodiment, the threaded engagement part of the first tool shaft may be spring pre-tensioned in the axial direction towards the second tool shaft. Alternatively or additionally, according to a preferred embodiment, the threaded engagement part of the second tool shaft may be spring pre-tensioned in the axial direction towards the first tool shaft. This has the advantage that with the spring pre-tension a predefined compression force that can be transmitted by the threaded engagement part and therefore also a predefined tightening torque can be set. Furthermore, damage to the thread due to excessive compression forces can be avoided.

[0021] According to a preferred embodiment, the first tool shaft can be integrally connected to the second tool shaft so as to be rotatable about its longitudinal axis, meaning that the second tool shaft rotates simultaneously with the rotation of the first tool shaft, in this way the torque for threading the screw can also be transmitted to the screw from the thread-engaging part of the second tool shaft.

[0022] According to a preferred alternative embodiment, the first tool axis may be rotatable relative to the second tool axis about its longitudinal axis. This means that when the first tool axis rotates, the second tool axis is stationary / does not rotate. The second tool axis therefore serves only as a counterholder for applying the axial compression force. Alternatively, the second tool axis may rotate about its longitudinal axis independently of the first tool axis. In this way, torque can also be applied to the screw via the second tool axis.

[0023] The object of the present disclosure is also solved by an assembly method for screwing a screw into an internal thread of a medical instrument having two branches, preferably by means of a screwdriver tool as described, for connecting the two branches to each other by means of a screw, such that the two branches are pivotable relative to each other about the screw as a hinge. The assembly method according to the invention comprises the steps of axially moving the first and second tool shafts of the screwdriver tool towards each other in order to clamp between the screw head and the screw shaft of the screw in the screwdriver tool, such that a compressive force is axially transmitted from the second tool shaft to the screw in a direction towards the first tool shaft, rotating the screwdriver tool, in particular the first tool shaft and possibly the second tool shaft, about a longitudinal screw axis relative to the instrument in order to transmit a torque (in particular for setting the tightening torque or the threading depth of the screw) to the screw clamped in the screwdriver tool and to screw the screw into the internal thread, and axially moving the first and second tool shafts apart and unscrewing the screw from the screwdriver tool.

[0024] Furthermore, a first of the two branches comprises a first through hole and a second of the two branches comprises a second through hole in which an internal thread is arranged. According to a preferred embodiment of the assembly method, the method comprises the steps of: moving the second tool shaft axially towards the first tool shaft and passing it through the second through hole, after which the screw is clamped by a screw-driving tool and inserted into the internal thread, or moving the second tool shaft axially towards the first tool shaft through the second through hole and after which the screw is inserted into the internal thread, moving the second tool shaft axially towards the first tool shaft through the second through hole and clamping the screw with a screw-driving tool.

[0025] Thus, the screw can first be clamped in the driving tool and then it is inserted into the female thread and screwed in, or the screw can first be inserted into the female thread and then it is clamped in the driving tool and screwed in.

[0026] Preferably, the screw may be fixed in its screwed position, for example by laser welding and / or adhesive, which may be applied prior to clamping with the driving tool.

[0027] In summary, it can be added that a connecting element for surgical instruments optimized for cleaning is provided, which solves the problem that tissue residues, dirt and body fluids collect and adhere to the slits of the screw and are not completely removed during the reprocessing process. The disadvantages of conventional connecting elements include the inability to reliably clean the slit bases and slits with sharp angles and the fact that assembly errors that are unavoidable in mass production, such as slippage of the screwdriver, have to be reworked manually, for example by grinding. The aim is therefore to enable the combination of a design of a connecting element head, free of deep pockets, slits etc. with sharp angles at the base, and a suitable assembly method, in which the tightening torque / assembly force applied can be finely adjusted / given. The screw head and the threaded end can be spherical, so that during the assembly process, when the screw is clamped between its head and the threaded end, the spherical support guides and self-centers the system. The force is transmitted by a friction force applied via the tool. In this process, the tightening torque or the action or section modulus of the moving parts can be finely adjusted and / or measured and / or recorded by a sensor system. If necessary, the threaded connection can be fixed in this threaded position via adhesive, laser weld spots, etc. The screw head is formed without slits or similar force transmission elements (form-fit means), so there is no need to rework the connection element to achieve the surface quality required for the surgical instrument / device. This results in reliable / reproducible machinability of the process, simplified assembly due to a high degree of mechanization during manufacturing, and excellent cleanability. [Brief description of the drawings]

[0028] [Figure 1] 1 shows perspective views of certain sections of a driving tool according to the present application at different points in an assembly method carried out with the driving tool; [Diagram 2] 1 shows perspective views of certain sections of a driving tool according to the present application at different points in an assembly method carried out with the driving tool; [Diagram 3]1 shows perspective views of certain sections of a driving tool according to the present application at different points in an assembly method carried out with the driving tool; [Figure 4] 1 shows perspective views of certain sections of a driving tool according to the present application at different points in an assembly method carried out with the driving tool; [Diagram 5] 4A-4D show further perspective views of the driving tool at different points in the assembly method carried out with the driving tool; [Figure 6] 4A-4D show further perspective views of the driving tool at different points in the assembly method carried out with the driving tool; [Figure 7] 4A-4D show further perspective views of the driving tool at different points in the assembly method carried out with the driving tool; [Figure 8] 1 shows a perspective view of a screw that can be screwed in with a screwdriver tool and an instrument into which the screw is screwed. [Figure 9] 1 shows a perspective view of a screw that can be screwed in with a screwdriver tool and an instrument into which the screw is screwed. [Figure 10] FIG. 1 shows a perspective view of a screw driving tool with two axially extending tool shafts and a tool shaft support / holding frame (in the form of a screw clamp). [Figure 11] FIG. 1 shows a perspective view of a screw driving tool with two axially extending tool shafts and a tool shaft support / holding frame (in the form of a screw clamp). [Figure 12] FIG. 1 shows a perspective view of a screw driving tool with two axially extending tool shafts and a tool shaft support / holding frame (in the form of a screw clamp). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Preferred embodiments of the present disclosure will now be described with reference to the accompanying drawings.

[0030] 1 to 7 show perspective views of certain sections of a driving tool 1 according to the present application at different points in an assembly method carried out with the aid of the driving tool. The driving tool 1 is used to screw a screw 2 having an external thread into an internal thread, which in the embodiment shown is constituted by a surgical instrument 3. In the embodiment shown, the screw 2 here fixes two components of the instrument 3 in such a way that they are movable, in particular pivotable, relative to one another.

[0031] The screw driving tool 1 has a first tool shank 4 with a larger shank diameter and a second tool shank 5 with a smaller shank diameter. The shank diameter of the first tool shank 4 is therefore larger than the shank diameter of the second tool shank 5. Preferably, the larger shank diameter corresponds approximately to the diameter of the screw head 6 of the screw 2, while the smaller shank diameter preferably corresponds approximately to (or slightly smaller than) the diameter of the screw shank 7 or core of the screw 2.

[0032] The first tool shaft 4 has an end thread engaging portion 8 arranged and configured to transmit torque to the screw 2, in particular to the screw head 6. The thread engaging portion 8 preferably corresponds to the shape of the screw head 6 and may in particular have a concavely curved surface. The concavely curved surface may preferably be spherical, even if not explicitly shown in the drawings. The second tool shaft 5 is aligned in an axially opposite direction to the first tool shaft 4. The first tool shaft 4 and the second tool shaft 5 therefore have a common longitudinal axis and are axially spaced apart. The second tool shaft 5 is oriented such that its end thread engaging portion 9 is axially opposite to the end thread engaging portion 8 of the first tool shaft 4 and arranged and configured to axially transmit a compressive force to the screw 2 in a direction towards the first tool shaft 4. That is, the screw 2 can be or is arranged axially between the first tool shaft 4 and the second tool shaft 5. The screw 2 can be axially clamped between the first tool shaft 4 and the second tool shaft 5. In the clamped state (see FIGS. 1 to 4), the screw head 6 contacts the screw engagement portion 8 , and the screw shaft / thread end portion 7 contacts the screw engagement portion 9 of the screwing tool 1 .

[0033] The first tool shaft 4 and the second tool shaft 5 may be axially movable, preferably pivotable or axially displaceable, relative to one another. For example, the first tool shaft 4 and the second tool shaft 5 may be configured like a press or like pliers.

[0034] Preferably, the threaded engagement portion 8 of the first tool shaft 4 may be spring pretensioned in the axial direction towards the second tool shaft 5, even if not shown. Preferably, the threaded engagement portion 9 of the second tool shaft 5 may be spring pretensioned in the axial direction towards the first tool shaft 4, even if not shown. For example, the first tool shaft may be integrally connected to the second tool shaft so as to be rotatable about its longitudinal axis, i.e. rotatably coupled. Alternatively, the first tool shaft 4 may be rotatable relative to the second tool shaft 5 about its longitudinal axis.

[0035] Figure 5 shows the described cutting tool 1 with the screw 2 clamped between two tool shafts 4, 5, without showing the instrument 3 into which the screw 2 is / is to be screwed. Figure 6 corresponds essentially to figure 2, showing the state during screwing of the screw 2, and figure 7 corresponds essentially to figure 4, showing the state in which the screw 2 has been screwed.

[0036] 8 shows a perspective view of the screw 2 in a first preferred embodiment. The screw head 6 of the screw 2 or its surface is convexly curved. In particular, the screw head 6 may be substantially rotationally symmetric, for example configured spherically. In this embodiment, the screw head 6 does not have a form-fit engagement surface.

[0037] 9 shows a perspective view of the instrument 3 into which the screw 2 is screwed in the first preferred embodiment. Due to the convex curvature and circular design of the screw head 6, there are no gaps or pockets where dirt, tissue residue or fluids can accumulate.

[0038] 10-12 show perspective views of the screwdriver tool 1. The screwdriver tool 1 may further comprise a compression force device 10. The compression force device 10 is arranged and configured to set, calculate and / or measure a compression force (axially from the second tool axis 5 towards the first tool axis 4 on the screw 2 or axially from the first tool axis 4 towards the second tool axis 5 on the screw 2). In other words, the compression force device 10 is arranged and configured to set, calculate and / or measure an axial clamping force of the screwdriver tool 1 acting on the screw 2. In particular, the compression force device 10 is arranged such that the axial distance between the first tool axis 4 and the second tool axis 5 is changeable / adjustable via the screw drive. The axial clamping force / axial compression force can thus be determined depending on the length of the screw 2 clamped by the screwdriver tool 1. Preferably, the compression force device 10 may have a tension spring 11 against the restoring force of which the axial distance between the first tool axis 4 and the second tool axis 5 can be varied, and in the embodiment shown can be shortened. The compression force device 10 can be operated manually or, preferably, automatically.

[0039] The screwdriving tool 1 may further comprise a tightening device 12. The tightening device 12 is provided and configured to set and / or measure the rotation angle and / or the torque of the thread-engaging portion 8 of the first tool shaft 4 and / or the thread-engaging portion 9 of the second tool shaft 5. The tightening device 12 can be manually or preferably automatically operable. The torque transmitted to the screw 2 by the screwing tool 1, e.g. a torque wrench, and / or the rotation angle transmitted to the screw 2 by the screwing tool 1, e.g. a rotation angle gauge, can be set and measured by the tightening device 12 in order to set a predetermined screw-in depth of the screw 2 (also called setting the turns of the thread) and / or to set a predetermined tightening torque with which the screw 2 is screwed in. In this way it is possible to set how far the screw 2 is screwed in, i.e. which turns of the thread of the screw 2 are engaged.

[0040] In the illustrated embodiment, the clamping device 12 has a first clamping wheel 13 rotatably fixedly connected to the first tool shaft 4. When the screw 2 is clamped in the screwdriver tool 1 and the first clamping wheel 13 is rotated relative to the instrument 3, the screw 2 is screwed into the instrument 3 with a friction torque resulting from an axial compression force. In the illustrated embodiment, the clamping device 12 has a second clamping wheel 14 rotatably fixedly connected to the second tool shaft 5. When the screw 2 is clamped in the screwdriver tool 1 and the second clamping wheel 14 is rotated relative to the instrument 3, the screw 2 is screwed into the instrument 3 with a friction torque resulting from an axial compression force. The maximum transmittable friction torque can be increased by rotating the two clamping wheels 13, 14. The two clamping wheels 13, 14 can be rotated / driven together or can be rotated / driven separately / individually from each other. Alternatively, only one clamping wheel may be provided, which when the first tool axis 4 is rotated relative to the instrument, also rotates relative to the second tool axis 5 (which acts only as a counter holder for applying an axial compression force).

[0041] The screwdriving tool 1 may have a holder 15 in which the first tool shaft 4 and / or the second tool shaft 5 are mounted. In the illustrated embodiment, the holder 15 has a first receptacle 16 in which the first tool shaft 4 is rotatably mounted and a second receptacle 17 in which the second tool shaft 5 is rotatably mounted. The axial distance between the two receptacles 16, 17 is adjustable via the compression force device 10. The holder 15 has axial guides 18 in the form of two rods aligned parallel to the axis of rotation, which guide the adjustment of the axial distance parallel to the axis of rotation. A scale 19 is arranged on the holder 15, which indicates the clockwise or counterclockwise direction (close or open) of the screwdriving tool 1.

[0042] As can be seen from Fig. 10, the screwdriving tool 1 according to the invention is used to screw a screw 2 into an internal thread of an instrument 3 having two branches 20, 21 in order to connect the two branches 20, 21 of the instrument 3 in such a way that the two branches 20, 21 are pivotable relative to one another. In this case, the set depth of the screw 2 or the turns of the thread of the screw 2 can be used to set the magnitude of the section modulus of the two branches 20, 21 of the instrument 3 which are thereby movably / pivotably connected to one another, i.e. the section modulus resulting from the threaded connection. Preferably, the first branch 20 of the two branches 20, 21 has a first through hole. Preferably, the second branch 21 of the two branches 20, 21 has a second through hole in which an internal thread is configured. In particular, the first through hole is smaller than the diameter of the screw head 6 so that the two branches 20, 21 can be pivotally fixed to one another by the screw head 6 abutting axially against the first through hole and the screw shaft 7 engaging through the first through hole into the internal thread of the second through hole.

[0043] The disclosure further relates to an assembly method for screwing a screw 2 into an internal thread of an instrument 3 with two branches 20, 21 for connecting the two branches 20, 21 of the instrument 3 so that they are pivotable relative to one another. In a step of the assembly method, the first tool shaft 4 and the second tool shaft 5 are moved axially towards one another and clamp between the screw head 6 and the screw shaft 7 of the screw 2 in the screwing tool 1, so that a compressive force is transmitted axially from the second tool shaft 5 towards the first tool shaft 4 to the screw 2 (from the first tool shaft 4 towards the second tool shaft to the screw 2). The thread engagement part 8 of the first tool shaft 4 is preferably moved so as to come into contact with the screw head over the entire surface of the screw head. The thread engagement part 9 of the second tool shaft 5 is preferably moved so as to come into contact with the screw shaft 7 over the entire (axial) surface.

[0044] In a downstream step of the assembly method, the screwdriving tool 1, in particular the first tool shaft 4 and preferably the second tool shaft 5, is rotated relative to the instrument 3 about the longitudinal thread axis of the screw 2 in order to transmit a torque to the screw 2 clamped in the screwdriving tool 1, in particular a torque for setting the tightening torque or the threading depth of the screw 2, and to screw the screw 2 into the internal thread. If the screw 2 is clamped between two thread-engaging portions 8, 9, a torque can be transmitted to the screw 2 by frictional engagement via the thread-engaging portion 8 of the first tool shaft 4 by rotating the thread-engaging portion 8 of the first tool shaft 4 about its longitudinal thread axis to generate a frictional torque. The thread-engaging portion 9 of the second tool shaft 5 can also be co-rotated / rotated to increase the frictional torque or can be stationary (relative to the instrument 3) to purely apply an axial (counter)compressive force. In particular, the screwdriving tool 1 is moved in a helical motion in order to screw the screw 2. Preferably, the screw 2 is screwed into the instrument 3 until the edges of the surfaces of the screw head 6 and / or the screw shaft 7 are preferably completely but at least partially flush with the surface of the instrument 3, depending on the surface of the instrument.

[0045] In the next step of the assembly method, the first tool shaft 4 and the second tool shaft 5 are moved axially apart and the screw 2 is unscrewed from the driving tool 1 .

[0046] Preferably, the second tool shaft 5 is moved towards the first tool shaft 4 and passed through the second through hole (of the second branch 21 with the female thread), after which the screw 2 is clamped by the screwing tool 1 and inserted into the female thread. Thus, the second tool shaft 5 is first passed through the instrument 3 ("from below", i.e. at the end of the instrument 3 opposite the screw head 6), the screw 2 is clamped by the screwing tool 1, then in the clamped state it is inserted into the female thread and screwed into the female thread by torque transmission. In particular, the second through hole is larger than the second tool shaft 5, so that the second tool shaft can be guided into the second through hole from below in order to clamp the screw 2.

[0047] Alternatively, the screw can first be passed through the first through hole of the first branch 20 and inserted into the internal thread of the second branch 21, after which the second tool shaft 5 is moved axially through the second through hole towards the first tool shaft 4 and the screw 2 is clamped in the screw-driving tool 1. The screw 2 is thus inserted into the internal thread "from above", i.e. from the end of the instrument 3 closer to the screw head 6, after which the first tool shaft 4 and the second tool shaft 5 are moved towards each other and clamp the screw 2. In particular, the second through hole is larger than the second tool shaft 5 and the second tool shaft can pass through the second through hole from below in order to clamp the screw 2. The screw 2 can preferably be rotated around the longitudinal screw-in direction before clamping the screw 2, i.e. screwed in only a few / few turns, for example manually.

[0048] Preferably, the screw 2 can be fixed in its screwed-in position by laser welding and / or adhesive and is then clamped by the screw-driving tool 1 .

Claims

1. A screwdriver tool, particularly for screwing a screw into a female thread of a medical instrument, a first tool shaft, preferably having a large shaft diameter, having an end thread engaging portion configured to transmit torque to the thread; a second tool shank, preferably having a smaller shank diameter, which is axially oriented with respect to the first tool shank and opposite to the first tool shank such that its end thread engagement portion axially faces the end thread engagement portion of the first tool shank, and which is adapted to transmit a compressive force axially to the thread in the direction of the first tool shank; a screw having a substantially spherical or frusto-conical surface, the screw being configured to receive a torque from the threaded engagement portion of the first tool shank and a compressive force from the threaded engagement portion of the second tool shank; A screwdriver tool comprising:

2. 2. A screwdriving tool according to claim 1, characterized in that the thread-engaging portion of the first tool shank and / or the thread-engaging portion of the second tool shank has a concavely curved surface, in particular a substantially spherical or frusto-conical surface.

3. 2. The screw driving tool according to claim 1, characterized by a tightening device provided and configured to set and / or measure a rotation angle and / or a torque of the thread-engaging portion of the first tool shank and / or the thread-engaging portion of the second tool shank.

4. The driving tool according to claim 1 , characterized by a compression force device provided and configured to set, calculate and / or measure the compression force.

5. 2. A driving tool according to claim 1, characterized in that the first tool shaft and the second tool shaft are held axially movable relative to each other, for example pivotable or axially displaceable relative to each other.

6. 2. A screwdriving tool according to claim 1, characterized in that the thread-engaging portion of the first tool shank is spring pretensioned axially towards the second tool shank and / or the thread-engaging portion of the second tool shank is spring pretensioned axially towards the first tool shank.

7. 2. A driving tool according to claim 1, wherein the first tool shank is integrally connected to the second tool shank such that the first tool shank is rotatably coupled about its longitudinal axis.

8. 2. A driving tool according to claim 1, wherein the first tool shank is rotatable about its longitudinal axis relative to the second tool shank.

9. 11. An assembly method for connecting two branches of a medical instrument to each other such that the two branches are pivotable relative to each other, comprising the steps of: threading a screw into an internal thread of the instrument using a screwdriver tool as claimed in claim 1 ; moving the first and second tool shafts of the screw driving tool axially toward each other to clamp a screw head and a screw shaft in the screw driving tool such that a compressive force is transmitted axially from the second tool shaft to the screw in a direction toward the first tool shaft; Rotating the screwdriver tool, in particular the first tool shaft, relative to the instrument about a longitudinal screw axis in order to transmit a torque to the screw held by the screwdriver tool, in particular to set the tightening torque or the penetration depth of the screw, and to drive the screw into the female thread. axially moving the first tool shaft and the second tool shaft apart to unscrew the screw from the driving tool; The assembly method comprises:

10. A first branch of the two branches includes a first through hole, and a second branch of the two branches includes a second through hole in which the female thread is formed, The second tool shaft is moved axially toward the first tool shaft, and the screw is then clamped by the screw driving tool and inserted into the female screw after passing through the second through hole; or passing the screw through the first through hole and inserting the screw into the female thread, and then axially moving the second tool shaft through the second through hole toward the first tool shaft and clamping the screw with the screw driving tool. The method of assembly of claim 9 comprising:

11. 11. A method according to claim 9 or 10, wherein the screw is fixed in its screwed-in position by laser welding and / or adhesive applied before being clamped by the screw driving tool.

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