Joining methods for medical technology devices

Abstract

The invention relates to a method for joining a medical device (1), in particular a surgical instrument or an implant, having a shaft (2) and a connecting piece (3) to be fastened thereto, comprising the following steps: heating (S1) the connecting piece (3) or cooling the shaft (2) so that the inner diameter (d d ) of an opening (4) of the heated connecting piece (3) is reduced. H ) is larger than the outer diameter (D) of the shaft (2); the shaft (2) is then inserted (S2) into the opening (4) of the connecting piece (3); and the connecting piece (3) is then cooled (S3) to heat the connecting piece onto the shaft (2) substantially without gap, or the shaft (2) is heated so that the shaft (2) and the opening (4) are connected to each other via an interference fit. The invention also relates to a corresponding medical device (1) and to the use of a joining method for producing such a medical device.

Description

Technical Field

[0001] Medical technology devices must meet high requirements with regard to functional reliability, tolerances and, in particular, sterility / maintaining sterility. This applies in particular to the connection points of such devices at which two components are firmly connected to one another. The following, for example, deals with the connection point of a surgical instrument having a handle and a working head, such as a surgical hammer. However, it should be noted that the same problem can be applied to many other medical technology devices and their different connection points. Background Art

[0002] According to the prior art, the handle is connected to the operating head (actuator) in the following manner, that is, these components are manually pressed together and prevented from sliding axially and radially by a cross pin or a stop pin. At the same time, the cross pin is pressed into a hole extending through the handle and the operating head and then must be matched by friction and the surface is brushed clean. These operating processes are costly and time-consuming. In addition, gaps are generated or left in such a pressurized connection, and deposits are formed in these gaps and blood, bacteria, dirt and chemical processing aids that cannot be removed during cleaning penetrate into these gaps. This disadvantageously leads to contamination and corrosion of the connection position. In order to avoid this situation, the connection position is subsequently protected by welding or bonding according to the specific situation, which additionally complicates the manufacturing method and increases the cost. Other joining methods that connect two components of medical equipment to each other under thermal load / action have been basically neglected in the past because the thermal deformation of at least one component of the components that need to be joined exceeds the above tolerance according to statistics. Summary of the invention

[0003] The object of the present invention is to reduce or avoid the disadvantages of the prior art and to provide an economical joining method for the stable and permanent connection of two components of a medical device, which connection meets high sterility requirements.

[0004] This object is achieved by a joining method according to the invention, a medical technology device according to the invention (eg a medical / surgical instrument) and the use of a corresponding joining method for producing a medical technology device according to the invention (eg a medical / surgical instrument).

[0005] The core of the invention is therefore to connect two components of a medical device, in particular a medical (surgical) instrument, which are to be joined together, by shrink fit. Here, it should be noted according to the invention that preferably only that component is substantially heat-processed, for which, for example, lower requirements are imposed on dimensional tolerances and / or material properties than on the other component. As an alternative or supplement, preferably only that component should be substantially heat-processed, which has a greater heat capacity than the other component (for example due to a greater mass). As an alternative or supplement, preferably only that component should be substantially heat-processed, which, due to its structure and / or its spatial dimensions / shape, shows a smaller tendency to deformation caused by heat input than the other component. As an alternative or supplement, preferably only that component should be substantially heat-processed, which consists of a material that has a thermal advantage over the material of the other component, for example, deforms sufficiently at a lower temperature than the other component to make a shrink fit process possible.

[0006] For example, a medical technical device (medical instrument) of this type can consist essentially of an (elongated / slender) instrument shaft and an instrument handle connected thereto / to be connected thereto and / or an actuator connected thereto / to be connected thereto (e.g. a hammer, a clamp, etc.). In such an example, according to the invention, the actuator, which is more rigidly constructed than the instrument shaft (shorter, thicker, more compact), should be the component that shows a smaller tendency to deformation caused by heat than the instrument shaft and is therefore subjected to heat treatment (only) for the subsequent shrink fit.

[0007] The object of the invention is achieved in particular by a joining method for medical technology devices, in particular surgical instruments or implants, having a shaft, for example made of titanium, and an attachment part (handle, actuator, etc.) to be fastened thereto, for example made of steel, wherein the joining method comprises the following steps:

[0008] Firstly, the adapter is heated or the shank is cooled so that it expands or contracts due to thermal expansion or contraction according to the material-specific expansion coefficient, so that the inner diameter of the (receiving) opening of the adapter is / becomes larger than the outer diameter of the shank (to be inserted).

[0009] - Then the shank is inserted into the opening of the adapter. That is, due to the thermal expansion of the adapter or the thermal contraction of the shank, the opening has / will be enlarged relative to the cross section of the shank and the shank and the adapter can freely move relative to each other in the axial direction of the shank in this state.

[0010] - Then, that is to say, after the shank has been inserted into the corresponding connecting piece opening, the connecting piece is cooled (actively or passively) in order to heat-fit the connecting piece onto the shank essentially without play, or the shank is heated (actively or passively) in order to expand the shank in the connecting piece so that the shank forms an interference fit or a press fit (i.e. a press connection) with the opening, preferably at the maximum ambient temperature to be expected during operation, further preferably at room temperature.

[0011] This joining method, which is used for the first time in medical equipment, can be at least semi-automated, and can also be fully automated depending on the specific situation and does not require or only requires a small number of undemanding, manual steps (work processes) by the user. That is, manual operations are reduced and some costly manual work processes and cross pins are omitted in assembly. It is thus possible to connect two components of a medical device simply, quickly and economically as well as reliably and permanently, and the connection also meets the strict requirements for sterility / easy cleanability. In addition, the appearance, quality and load-bearing capacity of the connection and the device are improved, so that higher (holding and / or torsion) forces can be transmitted than previous solutions. In addition, the repeatability / repeatability and process reliability of the joining method are also improved. Therefore, the process is suitable for being used as a basis for unifying various medical technology connection locations or interfaces and reducing the cost of overall production in this way. It is also particularly important that this method ensures that the gap between the shaft and the connecting piece is essentially completely closed during the cooling period due to the high pressure in the interference fit and that contamination and corrosion in the connection point are virtually eliminated during the intended operation of the medical device, in particular in the surgical field, and during subsequent chemical / heat (sterilization) treatment.

[0012] The shank can have a round or polygonal cross section without an undercut, for example a quadrangular or hexagonal cross section. In addition, the attachment can taper on a side where the shank projects from the attachment (a proximal end in the case of a surgical instrument) fastened thereto, so that an angle of more than 90° is formed at a transition point between the shank and the attachment, whereby the transition point is more accessible for cleaning and sterilization and / or deposits are less likely to form at this transition point. It should also be noted that the shank and the attachment can be made of different materials. In the above example, in which the shank is made of titanium and the attachment is made of steel, the two components can optionally be heated together, since steel has a higher thermal expansion or higher linear expansion coefficient and therefore even in the case of joint heating, the necessary enlargement of the attachment opening can be achieved without the excessive tendency to deformation that occurs in the case of the (titanium) shank.

[0013] It should be noted that due to the special requirements and materials of medical technology products, the geometric design of such connection points and the selection of the usable temperature range are important aspects, which will be discussed in detail below.

[0014] According to one aspect, for a control system, preferably a control system, for controlling or regulating the joining method, the parameters are freely programmable or adjustable, so as to adapt the joining method to different environmental conditions or to make it possible to join together different devices with different sizes and / or materials. The adjustable parameters in this case are, for example, heating power or cooling power, heating time or cooling time and heating power curve or cooling power curve. The method according to the invention can thus be applied to a single device or workstation for carrying out this method for producing different medical technology devices.

[0015] Preferably, during the joining process, the temperature of the butt joint and / or the rod is also monitored, and preferably the heating time and / or the cooling time is further monitored. For this purpose, for example, at least one pyrometer can be used as a temperature sensor. It is therefore possible to ensure that the rod can be easily inserted into the opening at the correct time point and the joining process is not terminated prematurely, so that the butt joint and the rod can slide or even separate from each other when necessary. In addition, it is possible to prevent the butt joint or, as the case may be, the rod from being excessively heated or cooled when in contact with the butt joint, so as to avoid defects in the mechanical properties of the corresponding components during or after heating or cooling. The pyrometer can be manually or automatically aligned, for example, with the aid of a mark, before the measurement is about to begin and / or during the measurement. As an alternative, for example, a contact thermometer or similar device can also be provided to replace one or more pyrometers.

[0016] It is particularly advantageous to monitor the temperature of the connecting piece or the shank at at least two points (positions): close to the opening, preferably directly at the opening (ie, on its inner circumference or directly at an opening outlet); The temperature of the connecting piece or the connecting piece is preferably measured at different points in the process, such as at or near the edge of the connecting piece (beside or on the edge of the connecting piece) or at the outer circumference of an end of the shank to be inserted into the connecting piece and at an edge region of the connecting piece spaced therefrom (that is, as far away from the opening as possible) or at a shank region spaced therefrom. This makes it possible to monitor and compare the temperature at different important points when adjusting the process parameters and thus also to monitor the thermal conductivity in the connecting piece or the shank during heating and, if appropriate, cooling in order to adjust or set the optimal process sequence.

[0017] Temperature measurement on the shank (e.g. at a stationary point or a point whose position can be changed during the joining process) is useful, for example, when cooling this shank. As an alternative or in addition, this is useful for determining or predetermining a required minimum temperature of the connecting piece relative to the shank temperature or room temperature, which correspond to one another as the case may be (especially when the shank is not heated or cooled), and / or for determining or predetermining a minimum temperature difference between the connecting piece and / or the shank and / or room temperature. It is also useful to monitor the temperature in the axial extension of the opening and / or of the shank, in particular the shank tip (of the shank section received in the opening), in order to avoid or reduce axial stresses after cooling. In other words, the temperature distribution is preferably determined (positionally resolved and / or time resolved) axially along the rod or the tip of the rod body (along the axial extent / axial extension of the rod / rod body tip) and / or axially along the inner circumference of the opening (along the axial extension in the opening), for which purpose, for example, two or more points or measuring points for measuring the temperature can be arranged axially distributed on the rod and / or in the opening.

[0018] Preferably, induction heat is used to heat the attachment, or nitrogen is used to cool the shank. In particular, heating by induction heat is a simple, reliable, fast-acting and well-controlled heating method, in which open heat sources are avoided and the risk of injury is thus reduced. As an alternative, a heating plate or a resistance heater or the like can also be used.

[0019] According to one aspect of the invention, within the scope of the joining method, the heat input during heating can also be adjusted as a function of the component parameters of the attachment and, if applicable, the shaft. For example, the geometry, surface properties, dimensions, heat treatment state, expansion coefficient and / or corrosion resistance of the attachment and / or the shaft can be taken into account as component parameters. In particular, the consideration of the expansion coefficient and the heat treatment state, i.e., the properties of the material used specifically in medical technology, is important in order not to negatively influence the corrosion resistance.

[0020] The interference fit of the shank and the adapter is preferably dimensioned in such a way that the shank and the adapter are inseparably (permanently) connected to each other in the axial and radial directions during operation. This is important for ensuring the functional reliability of the device. It is taken into account that the shank and the adapter are made of different materials with different thermal expansion coefficients as appropriate and the interference fit is designed in such a way that a pressurized connection is ensured at least in a temperature range provided for the operation of the device. It is further preferred that the corresponding connection can be reversibly separated by reheating, so that, for example, a quick and simple repair or replacement of the shank and / or the adapter is possible in maintenance situations. An interference fit with an interference of between 20 and 55 μm has proven to be suitable. Depending on the application of the medical technology device, different requirements may be placed on the connection strength, so that the interference can be designed differently. For example, a low interference, for example 20 to 25 μm, can be specified in a first application with low loads; a medium interference, for example 35 to 40 μm, can be specified in a second application with medium loads; or a large interference, for example 50 to 55 μm, can be specified in a third application with high loads. That is, the geometric design of the stem and the adapter, in particular the adapter opening, depends on the application of the product.

[0021] The heating temperature of the connection piece is preferably between 50 and 350° C., preferably between 300 and 350° C. This makes it possible to substantially enlarge the opening without adversely affecting the mechanical properties of the shank or the connection piece.

[0022] According to another viewpoint of the present invention, the rod can be inserted into the opening of the connecting piece via a linear unit. This makes it possible to automate or at least simplify the insertion of the rod into the opening of the connecting piece in addition to heating and cooling, and thus further reduce production costs. In addition, the insertion depth of the rod can be accurately controlled and replicated in this way and the user's operation can be further reduced, thereby reducing the risk of injury to the user on the hot connecting piece and reducing human errors. The linear unit can take over the connecting piece already on the heating device or cooling unit or keep the connecting piece already during heating or cooling. When the connecting piece is removed from the heating device or cooling unit or transported to the connecting piece on the rod after heating or cooling, the heating device or cooling unit is ready to heat the next connecting piece and can increase the production cycle. In this case, the linear unit is particularly beneficial because the rod must be inserted into the connecting piece very accurately and very quickly according to the specific situation-because the size and tolerance are very small and the components cool down or heat up quickly-in view of the partial high miniaturization of medical technology equipment. If this operation is performed manually by the user, the probability of error may be very high. As an alternative, the rod can be held by a linear unit and inserted / embedded into the opening of a fixed connecting piece. In this case, it is not necessary to move the connecting piece or the rod in the heated or cooled state at all, and it is sufficient to cool or warm the connecting piece or the rod by turning off the heating device or the cooling unit.

[0023] The object of the invention is also achieved by a medical device, in particular a surgical instrument or an implant, which has an adapter with an opening and a shaft inserted into the opening, wherein the outer diameter of the shaft and the inner diameter of the opening of the (cooled) adapter are dimensioned to form an interference fit or a press fit, and the adapter is connected to the shaft by the above-mentioned joining method. Preferably, the shaft is a handle or a handle, and the adapter is a working head or a tool head of the medical instrument. For advantages and further details of this device, reference is made to the above description of the associated joining method.

[0024] Furthermore, the object is achieved by using the above-described joining method for producing a medical device, in particular a medical instrument or an implant, preferably as described above, which has a connection piece and a shaft that is inserted into an opening in the connection piece. Reference is made to the above description for advantages and design configurations of the joining method and the medical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic diagram of an embodiment of the bonding method of the present invention, wherein Figure 1A 1 to 2 C show the sequential steps of the joining method;

[0026] Figure 2An exemplary production layout of a joining method is shown;

[0027] Figure 3 An example of a further embodiment of a tipping piece is shown. DETAILED DESCRIPTION

[0028] FIG1 shows an embodiment of the joining method according to the invention for a medical device 1, which for illustration purposes is shown here as a surgical instrument with a shaft or handle 2 and a simple, cylindrical or cuboid adapter or working head 3, for example in the form of a surgical hammer. However, any different shape of the working head 3 can be selected depending on the application.

[0029] Figure 1A A heating step S1 is shown. A working head 3 having an opening 4, in this example a hole or a blind hole, is arranged on an induction heating device 5 and heated by induction heat. At the same time, the temperature of the connecting part or the working head 3 is preferably measured at a point P1 close to the edge of the opening and / or at a point P2 of the connecting part spaced therefrom (depending on the specific situation, a temporal and / or local (axial) temperature distribution). As an alternative or supplement, the temperature of the shaft or shank 2 can be measured at a point P3 close to the end of the shank / rod to be inserted into the opening 4 and at a point P4 on another shank area / rod area spaced therefrom. Due to the thermal expansion of the material of the working head 3, the working head 3 expands and thus also enlarges the opening 4. That is, the opening 4 has a first "cold" inner diameter d at room temperature. K and has a second "hot" inner diameter d in the heated state H , the inner diameter is larger than the cold inner diameter d K .

[0030] After the working head 3 has been heated to a certain temperature and / or for a certain heating time (wherein the temperature can be measured, for example, at points P1 and / or P2), the shank 2 is inserted into the opening 4 along the longitudinal direction of the shank 2 (S2), and the "cold" outer diameter D of the shank (that is, preferably at room temperature or the maximum ambient temperature to be expected during operation, wherein the shank temperature or the shaft temperature can be measured / monitored, for example, at points P3 and / or P4 on the shank 2) corresponds to the cold inner diameter d of the working head 3. K There is a certain amount of interference, but it is smaller than the hot inner diameter d at this point in time. H .

[0031] Then the working head 3 is cooled (S3), in which way the opening 4 also shrinks / becomes smaller and the working head 3 is heat-pressed onto the handle 2. Figure 1CAs shown in FIG. 1 , a press connection of the shank 2 and the working head 3 is produced due to an interference fit / press fit. Preferably, the temperature of the shaft / shank 2 and / or the working head 3 is measured at points P1 and / or P2 and / or P3 and / or P4, respectively. The inner circumference of the opening 4 is hereby press-fitted to the outer circumference of the shank 2 at room temperature (with respect to the forces occurring under the intended use) in an axially and radially immovable manner due to the interference fit of the shank 2.

[0032] Figure 2 An exemplary production layout for the above-described joining method is shown. A heating device 5 is provided, in this example an induction coil, which is used to heat the working head 3 in step S1. At the same time, a temperature monitoring unit 6 detects the temperature of the working head 3 at a plurality of locations, for example via a pyrometer (step S4) and determines the temperature deviation and, if applicable, the heat input therefrom. A control unit 7, which monitors the heating time and predetermines a setpoint temperature and, if necessary, a temperature distribution or heat input, receives the monitoring signals of the temperature monitoring unit and controls the heating device 5 as a function of these monitoring signals (step S5).

[0033] If a set temperature has been reached, a signal, such as an acoustic signal or a light signal, is emitted and the user hands over the work head 3 to a linear unit 8 or the work head 3 is fully automatically received by the linear unit 8. The linear unit 8 is used to reliably and evenly fit / attach the work head 3 to the handle 2 in step S2 so that the handle is accurately positioned therein after the work head 3 cools (S3). As an alternative, the attachment can also be performed manually by the user. If the user attaches or hands over the linear unit 8, the control unit 7 can also be configured to control the heating device 5 as follows, that is, to keep the work head 3 at the set temperature for a certain time. Then the control unit 7 can monitor the cooling time during cooling and monitor the temperature of the work head 3 via the temperature monitoring unit 6 to determine when the work head 3 and the handle 2 can be sufficiently firmly stacked on each other and handled according to the specific situation without risk of injury to the user. At this point in time, another signal can be emitted.

[0034] Figure 3An example of a further embodiment of the connection piece or working head 3 is shown. A number of mutually independent aspects are shown, which can be implemented in any combination or individually in the working head 3 of the invention. The first aspect relates to a substantially drop-shaped cross section of the working head 3, wherein the tip of the drop points in the direction of the shaft or handle 2. In other words, the cross section of the working head 3 tapers in the direction of the shaft or handle 2 (where this shaft or handle protrudes proximally from the working head). This improves the accessibility of the edge in the transition area between the working head 3 and the handle 2 for cleaning purposes and / or sterilization purposes.

[0035] The second aspect relates to a multi-part working head 3. Here, a first proximal connecting part 3a (i.e., closer to the proximal shank end to be treated) is already or can be shrink-fitted onto the shank 2, and a second distal connecting part 3b can be designed, for example, as a disposable part and can be inserted into the instrument (i.e., the proximal connecting part 3a already connected to the shank 2). As an alternative, the distal connecting part 3b can also be first connected to the proximal connecting part 3a and then shrink-fitted together with this connecting part onto the shank 2, wherein the provided interfaces and diameters must be precisely coordinated with each other in order to avoid mutual damage during thermal expansion and subsequent contraction. The distal connecting part can be closed or open in the longitudinal direction of the shank 2 toward the distal end.

[0036] A third aspect relates to the positioning of the shank 2 with respect to the working head 3 along the longitudinal direction of the shank 2. The shank 2 can form a step or shoulder 2a which is provided for abutment against a complementary shoulder or step of the working head 3 in the longitudinal direction.

[0037] The fourth aspect involves configuring the opening 4 of the adapter 3 as a through hole. In this way, it is possible to prevent air from being trapped in the cavity between an opening wall and the distal end of the shank 2, which could affect the accurate positioning in the axial direction. In this case, the shank 2 is positioned in the adapter 3 along the longitudinal direction of the shank 2 so that the distal shank end is tightly closed to the adapter 3, which helps to avoid additional edges that need to be cleaned.

[0038] It should be noted that the above embodiment can also be improved as follows, that is, a cooling device can be provided instead of the heating device, and it can also be provided that the rod part is cooled by this cooling device instead of heating the connecting part, wherein the rod part is heated after being inserted into the opening of the connecting part to form a press fit.

[0039] Reference numerals list

[0040] 1 Medical technology equipment

[0041] 2. Shaft (handle)

[0042] 2a Step / shoulder

[0043] 3. Adapter (operating head)

[0044] 3a Proximal connecting part

[0045] 3b Far end adapter

[0046] 4 Opening

[0047] 5 (Induction) heating device

[0048] 6 Temperature monitoring unit

[0049] 7 Control unit

[0050] 8 Linear Units

[0051] P1 (measurement) point close to the opening

[0052] P2 (measurement) point on the edge area of ​​the connecting piece spaced apart from point P1

[0053] P3 (Measurement) point on the outer circumference of the end of the rod to be inserted into the adapter

[0054] P4 (measurement) point on the shaft area spaced from point 3

Claims

1. A joining method for a medical device (1), the device (1) being a surgical instrument or an implant having a shaft (2) and a receiving part (3) to be fastened thereto, characterized by the following steps: The connecting piece and the stem are provided, wherein the connecting piece has an opening, the opening has an inner diameter, and the stem has an outer diameter. sizing the inner diameter of the opening and the outer diameter of the stem for an interference fit at room temperature; The connecting piece (3) is heated (S1) or the rod (2) is cooled, so that the inner diameter (d H ) is greater than the outer diameter (D) of the rod (2), Then, the rod (2) is inserted (S2) into the opening (4) of the connecting piece (3). If the connecting piece is heated in the previous step, the connecting piece (3) is then cooled (S3) to heat-fit the connecting piece (3) onto the shank (2) substantially without gap, or if the shank is cooled in the previous step, the shank (2) is heated to expand the shank (2) in the opening (4) of the connecting piece (3) so that the shank (2) and the opening (4) are connected to each other via an interference fit, and During the heating or cooling process, the temperature of the connecting piece (3) is monitored (S4) at a first point (P1) close to the opening (4) and at a second point (P2) on the edge of the connecting piece (3) or on the edge region of the connecting piece close to the edge of the connecting piece (3), and at a point (P3) close to the end of the rod (2) to be inserted into the connecting piece (3) and at a point (P4) on the rod region spaced apart from the point (P3). 2 . The joining method according to claim 1 , wherein in the step of providing the adapter and the stem, the inner diameter is smaller than the outer diameter at room temperature. 3 . The joining method according to claim 1 , further comprising the step of monitoring ( S4 ) the heating and / or cooling time.

4. The joining method according to claim 3, wherein the temperature of the connecting piece (3) is monitored in the vicinity of the opening (4) and at an edge region of the connecting piece spaced apart therefrom.

5. The bonding method according to claim 1, wherein: An inductive heating device (5) is used to heat (S1) the connecting piece (3).

6. The joining method according to claim 1 further comprises a step of adjusting (S5) the heat input during the heating (S1) according to at least one of the geometric shape, surface characteristics, dimensions, heat treatment state, expansion coefficient and corrosion resistance parameters of the shank (2) and the connecting piece (3).

7. The bonding method according to claim 1, wherein: The interference fit is dimensioned such that the shaft (2) and the adapter (3) are inseparably connected to one another in the axial and radial directions during operation of the medical device.

8. The bonding method according to claim 1, wherein: The interference fit has an interference between 20 and 55 μm.

9. The bonding method according to claim 1, wherein: The rod part (2) is made of titanium, and the connecting piece (3) is made of steel.

10. The bonding method according to claim 1, characterized in that: The maximum heating temperature of the connecting piece (3) is between 50 and 350°C.

11. The bonding method according to claim 1, wherein: The shaft (2) is automatically inserted (S2) into the opening (4) of the adapter (3) via a linear unit (8).

12. A medical technology device (1) having a connecting piece (3) with an opening (4), and The rod (2) is inserted into the opening (4), in, The outer diameter (D) of the rod (2) and the inner diameter (d K ) is sized to form an interference fit. It is characterized in that the connecting piece (3) is connected to the rod (2) by a joining method according to any one of claims 1 to 11.

13. The medical technology device (1) according to claim 12, wherein: The rod part (2) is a handle or a grip, and / or the connecting piece (3) is a working head or a tool head.

14. The medical technology device (1) according to claim 12, wherein: The rod part (2) is made of titanium, and / or the connecting piece (3) is made of steel.

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