Medical instrument having a plain bearing

Abstract

The invention relates to a medical instrument (1) having an instrument housing (2) with a first housing component (3) and a second housing component (4) which are rotatable relative to each other by means of a bearing arrangement (5) for a plain bearing (6), wherein the bearing arrangement (5) has a plain bearing bush (7) with an inner running surface (8) and an outer running surface (9), and also a running surface (10) which is formed on the first housing component (3) and which is operatively connected to the inner running surface (8) of the plain bearing bush (7), and a running surface (11) which is formed on the second housing component (4) and which is operatively connected to the outer running surface (9) of the plain bearing bush (7). In order to provide a medical instrument (1) having a bearing arrangement (5) for a plain bearing (6) which ensures compensation of manufacturing tolerances and a sufficient and variably adjustable contact pressure, it is proposed according to the invention that, viewed about the circumference of the outer running surface (9) of the plain bearing bush (7), the running surface (11) of the second housing component (4), which is operatively connected to the outer running surface (9) of the plain bearing bush (7), has a first region (I) in which this running surface (11) is in direct contact with the outer running surface (9) of the plain bearing bush (7), and a second region (II) in which this running surface (11) is spaced from the outer running surface (9) of the plain bearing bush (7), and that clamping elements (12) can be placed in the second region (II), by means of which clamping elements the outer running surface (9) of the plain bearing bush (7) is force-lockingly connectable to the running surface (11) of the second housing component (4).

Description

[0001] MEDICAL INSTRUMENT WITH A SLIDING BEARING

[0002] The invention relates to a medical instrument with an instrument housing, a first housing component and a second housing component, which are rotatable relative to each other by means of a bearing arrangement for a sliding bearing, wherein the bearing arrangement comprises a sliding bearing bushing with an inner running surface and an outer running surface, as well as a running surface formed on the first housing component which is in operative contact with the inner running surface of the sliding bearing bushing and a running surface formed on the second housing component which is in operative contact with the outer running surface of the sliding bearing bushing.

[0003] Plain bearings are machine elements designed to reduce friction between two moving surfaces. They often support and guide a shaft or axle that rotates or moves relative to the bearing housing.

[0004] The rotation of two components relative to each other is usually made possible by mounting one component in a rotationally fixed manner on the sliding bearing bushing, while the other component is rotatable along the inner or outer running surface of the sliding bearing bushing relative to the first component.

[0005] To achieve this rotationally fixed bearing arrangement on the plain bearing bushing, it is necessary to apply sufficient contact pressure between the component and the plain bearing bushing, or vice versa. In practice, however, it has proven difficult to adjust the required contact pressure, especially when considering manufacturing tolerances.

[0006] A medical instrument with a bearing arrangement for a sliding bearing is known, for example, from DE 102021 119528 B4.

[0007] Furthermore, a sliding bearing arrangement with a slotted sliding bearing bushing is known from DE 102012216481 B4.

[0008] Based on this, the invention aims to create a medical instrument with a bearing arrangement for a plain bearing that ensures compensation for manufacturing tolerances and sufficient and variably adjustable contact pressure. The solution to this problem is characterized according to the invention in that the running surface of the second housing component, which is in operative connection with the outer running surface of the plain bearing bushing, has, viewed over the circumference of the outer running surface of the plain bearing bushing, a first region in which this running surface is in direct contact with the outer running surface of the plain bearing bushing, and a second region in which this running surface is spaced apart from the outer running surface of the plain bearing bushing, and that clamping elements can be placed in the second region by means of which the outer running surface of the plain bearing bushing can be force-fitted to the running surface of the second housing component.

[0009] The use of the clamping elements according to the invention makes it possible to connect the second housing component to the sliding bearing bushing in a rotationally fixed manner, even if the outer running surface of the sliding bearing bushing is only partially enclosed by the running surface of the second housing component, so that the sliding bearing can only be rotated via the inner running surface of the sliding bearing bushing and the running surface of the first housing component, compensating for manufacturing tolerances.

[0010] The partial enclosure of the sliding bearing bushing by the second housing component is due to the simpler assembly of the two housing components, which can be rotated relative to each other.

[0011] To form the clamping elements, a preferred embodiment of the invention proposes that two clamping elements be provided which, viewed in the circumferential direction of the running surface of the second housing component, are wedge-shaped. The wedge-shaped design of the clamping elements allows for the simple bridging of the spaced-apart running surfaces of the second housing component and the sliding bearing bushing. According to a practical embodiment of the invention, the two wedge-shaped clamping elements are spaced apart from each other in the circumferential direction of the running surface of the second housing component, such that the wide ends of the wedge-shaped clamping elements face each other.

[0012] To secure and clamp the clamping elements, the invention proposes a design in which each clamping element has a threaded bushing with an internal thread, and in the second housing component, a bore extending radially to the sliding bearing bushing is formed for each clamping element. A setscrew can be screwed into the threaded bushing of the corresponding clamping element through this bore. The outer diameter of the threaded bushing is larger than the inner diameter of the radial bores in the second component. The larger outer diameter of the threaded bushings causes them to move radially outwards when the setscrews are screwed in, bearing against the second housing component. With the second housing component acting as a counter-bearing for the threaded bushings, screwing the setscrews into the threaded bushing presses the clamping elements against the outer running surface of the sliding bearing bushing.

[0013] To facilitate the screwing of the threaded pins into the threaded bushings arranged in the clamping elements, the invention proposes that the radial bores in the second housing component are designed as elongated holes extending transversely to the running surface of the second housing component, so that even in the event of small positional deviations between the second housing component and the clamping elements, the threaded pins can be screwed into the corresponding threaded bushings.

[0014] According to an alternative embodiment of the invention, it is proposed that the wide ends of the wedge-shaped clamping elements are designed in a fork-like shape, consisting of two radially spaced webs.

[0015] To generate the clamping effect between the running surface of the second housing component and the outer running surface of the sliding bearing bushing, this alternative embodiment proposes that a threaded bushing with an internal thread be arranged in the radially outer webs of each clamping element, and that a bore extending radially to the sliding bearing bushing be formed in the second housing component for each clamping element, through which a setscrew can be screwed into the threaded bushing of the respective clamping element. Alternatively, instead of using the threaded bushing, the internal thread for receiving the setscrew can also be cut directly into the material of the radially outer webs of each clamping element.

[0016] According to the invention, the clamping force between the two running surfaces is achieved by the radially outer webs of the clamping elements being pressed radially outwards against the running surface of the second housing component via the threaded studs screwed into the threaded bushings, with the radially inner webs of the clamping elements acting as abutments for the threaded studs. This design makes it possible to set a variably adjustable contact pressure on the sliding bearing bushing.

[0017] To achieve optimal load distribution of the contact pressure on the sliding bearing, it is further proposed that a three-point load distribution of the contact pressure, viewed circumferentially on the running surface formed on the second housing component, be adjustable via the clamping elements. According to a practical embodiment of the invention, it is further proposed that a continuous longitudinal slot extending transversely to the running surfaces of the sliding bearing bushing be formed in the sliding bearing bushing.

[0018] In order to fix the sliding bearing bushing with the longitudinal slot relative to the second housing component, the invention proposes that a fixing element, which can be fixed to the second housing component, can be inserted into the longitudinal slot, wherein the fixing element fills the longitudinal slot in the circumferential direction of the outer running surface of the sliding bearing bushing.

[0019] Furthermore, the invention proposes that, in the design of the clamping elements with the two radially spaced webs at the wide end of the clamping elements, the radially inner webs of each clamping element can be fixed to the fixing element with their free ends in order to secure the clamping elements against rotation and to maintain the set clamping pressure. Advantageously, each clamping element is fixed by means of a pin molded onto the wide end of each radially inner web, projecting outwards from the sliding bearing bushing, which engages in a corresponding groove in the fixing element.

[0020] Finally, the invention proposes that the medical instrument is an exoscope mounted on a holding arm.

[0021] Further features and advantages of the invention will become apparent from the accompanying drawings, in which two exemplary embodiments of a medical instrument according to the invention are shown, without limiting the invention to these embodiments. The drawings show:

[0022] Fig. 1 shows a partial perspective view of a medical instrument according to the invention;

[0023] Fig. 2 shows an enlarged perspective view of detail II according to Fig. 1, representing a first embodiment of a bearing arrangement for a sliding bearing;

[0024] Fig. 3 is a partial exploded view of the representation according to Fig. 2;

[0025] Fig. 4 shows a front view of the representation according to Fig. 2, showing the bearing arrangement before clamping;

[0026] Fig. 5 shows a view according to Fig. 4, but showing the bearing arrangement in the preloaded state, and Fig. 6 shows a view of detail VI according to Fig. 4, but showing a second embodiment of a bearing arrangement for a sliding bearing.

[0027] Figure 1 shows a partial view of a medical instrument 1, such as an exoscope, with an instrument housing 2, which has a first housing component 3 and a second housing component 4 that can be rotated relative to each other.

[0028] The rotation of the first housing component 3 relative to the second housing component 4 is effected by means of a bearing arrangement 5 for a sliding bearing 6, the construction of which can be seen in particular in Figures 2 to 5. While the instrument housing 2 is preferably made of metal, preferably aluminum, the sliding bearing is made of a plastic material.

[0029] The bearing arrangement 5 has a sliding bearing bushing 7 with an inner running surface 8 and an outer running surface 9, as well as a running surface 10 formed on the first housing component 3, which is in operative contact with the inner running surface 8 of the sliding bearing bushing 7, and a running surface 11 formed on the second housing component 4, which is in operative contact with the outer running surface 9 of the sliding bearing bushing 7.

[0030] As can be seen in particular from Figures 4 and 5, in the medical instrument 1 shown, the running surface 11 of the second housing component 4, which is in operative contact with the outer running surface 9 of the sliding bearing bushing 7, has, viewed over the circumference of the outer running surface 9 of the sliding bearing bushing 7, a first region I in which this running surface 11 is in direct contact with the outer running surface 9 of the sliding bearing bushing 7 and a second region II in which this running surface 11 is spaced apart from the outer running surface 9 of the sliding bearing bushing 7.

[0031] The fact that the outer running surface 9 of the sliding bearing bushing 7 is not fully enclosed by the running surface 11 of the second housing component 4 in the second area II is due to a simpler assembly of the two housing components 3 and 4 which can be rotated relative to each other.

[0032] To ensure that sufficient contact pressure can be generated between the second housing component 4 and the sliding bearing bushing 7 even with this design of the bearing arrangement 5, two clamping elements 12 are arranged in the second area II. These clamping elements allow the outer running surface 9 of the sliding bearing bushing 7 to be positively connected to the running surface 11 of the second housing component 4. As can be seen particularly in Figures 3 to 5, two clamping elements 12 are provided. Viewed in the circumferential direction of the running surface 11 of the second housing component 4, they are wedge-shaped and spaced apart from each other in the circumferential direction of the running surface 11 of the second housing component 4. They are positioned between the outer running surface 9 of the sliding bearing bushing 7 and the running surface 11 of the second housing component 4 such that the wide ends 13 of both wedge-shaped clamping elements 12 face each other.

[0033] In order to fix the clamping elements 12 in place in the second area II between the outer running surface 9 of the sliding bearing bushing 7 and the running surface 11 of the second housing component 4, a threaded bushing 15 with an internal thread 14 is arranged in each clamping element 12, and a bore 16 extending radially to the sliding bearing bushing 7 is formed in the second housing component 4 for each clamping element 12, through which a threaded pin 17 can be screwed into the threaded bushing 15 of the respective clamping element 12, wherein the outer diameter of the threaded bushings 15 is larger than the inner diameter of the radial bores 16 in the second housing component 4.

[0034] Of course, it is also possible to design the threaded bushings 15 with a non-circular outer geometry. In this case, the outer geometry of the threaded bushings 15 must be larger than the inner diameter of the radial bores 16 in the second housing component 4.

[0035] The larger outer diameter of the threaded bushings 15 causes the threaded bushings 15 to move radially outwards when the threaded pins 17 are screwed into the threaded bushings 15 and to rub against the second housing component 4.

[0036] The screwing in of the threaded pins 17 into the threaded bushings 15 arranged in the clamping elements 12 can be simplified by the fact that the radial bores 16 in the second housing component 4 are designed as elongated holes 18 extending transversely to the running surface 11 of the second housing component 4, so that even in the event of any small positional deviations between the second housing component 4 and the clamping elements 12 the threaded pins 17 can be screwed into the corresponding threaded bushings 15 of the clamping elements 12.

[0037] Furthermore, the elongated holes 18 serve to position the clamping elements 12 so that they are always mounted in the same position and are always held in position by the resulting rotational forces. As can also be seen in Figures 2 to 5, a continuous longitudinal slot 19 extending transversely to the running surfaces 8 and 9 of the sliding bearing bushing 7 is formed in the sliding bearing bushing 7 to facilitate its assembly.

[0038] To fix the sliding bearing bushing 7, which has a longitudinal slot 19, relative to the second housing component 4, a fixing element 20, which can be attached to the second housing component 4, can be inserted into the longitudinal slot 19. The fixing element 20 essentially fills the longitudinal slot 19 in the circumferential direction of the outer running surface 9 of the sliding bearing bushing 7. The fixing element 20 serves as a rotary driver between the sliding bearing 6 and the first housing component 3.

[0039] The clamping of the bearing arrangement 5, constructed as described above, is described below with reference to Figures 3 to 5:

[0040] The illustration shown in part as an exploded view according to Fig. 3 shows in particular area II, in which the running surface 11 of the second housing component 4 is spaced apart from the outer running surface 9 of the sliding bearing bushing 7.

[0041] In a first step, the threaded bushings 15, which are provided with an internal thread 14, are inserted into the wedge-shaped clamping elements 12, which are still located outside the bearing arrangement 5. Subsequently, as can be seen in Figs. 4 and 5, the two wedge-shaped clamping elements 12 are inserted into area II, in which the running surface 11 of the second housing component 4 is spaced apart from the outer running surface 9 of the sliding bearing bushing 7, such that the wide ends 13 of both wedge-shaped clamping elements 12 face each other.

[0042] After placing the clamping elements 12 between the running surface 11 of the second housing component 4 and the outer running surface 9 of the sliding bearing bushing 7, the threaded pins 17 are inserted into the bores 16 in the second housing component 4 and screwed into the threaded bushings 15 arranged in the associated clamping elements 12.

[0043] Before the threaded pins 17 are screwed further into the threaded bushings 15, the fixing element 20 is screwed to the second housing component 4 such that the fixing element engages in the longitudinal slot 19 formed in the sliding bearing bushing 7. The fixing element 20 serves as a torque wrench for the sliding bearing 6. Figure 4 shows the bearing arrangement 5 in this previously described configuration before the threaded pins 17 are tightened. Tightening the threaded pins 17 pulls the threaded bushings 15 out of their inserts in the respective clamping element 12. Since the outer diameter of the threaded bushings 15 is larger than the inner diameter of the radial bores 16 in the second housing component 4, pulling the threaded bushings 15 out of the clamping elements 12 causes the radially outwardly displacing threaded bushings 15 to run against the running surface 11 of the second housing component 4.The threaded bushing 15 clamps the clamping elements 12 to the second housing component 4. This results in a contact pressure on the sliding bearing 6 that depends on the tightening torque of the threaded pin 17.

[0044] The arrangement of the two clamping elements 12 within the bearing arrangement 5 creates a three-point load with three areas of increased contact pressure D when the threaded pins 17 are tightened, as shown schematically in Fig. 5. This three-point load distribution ensures very good load distribution on the sliding bearing 6.

[0045] The further the threaded pins 17 are screwed into the threaded bushings 15, the higher the contact pressure D of the clamping elements 12 on the sliding bearing. This allows the sliding bearing run to be variably adjusted to compensate for manufacturing tolerances.

[0046] In order to be able to absorb the forces occurring when screwing the threaded pins 17 into the threaded bushing 15, the threaded bushings 15 are made of metal, preferably steel, in contrast to the clamping elements 12 which are made of a plastic material.

[0047] Figure 6 shows an alternative design for the clamping elements 12. Although Figure 6 shows the modified clamping element 12 only on one side of the bearing arrangement 5, in this embodiment, as previously described in Figures 2 to 5, two clamping elements 12 are of course provided, both of which are constructed as described below.

[0048] According to this alternative embodiment, the wide ends 13 of the wedge-shaped clamping elements 12 are fork-shaped and consist of two radially spaced webs 21 and 22.

[0049] To generate the contact pressure D between the running surface 11 of the second housing component 4 and the outer running surface 9 of the sliding bearing bushing 7, a threaded bushing 15 with an internal thread 14 is arranged in the radially outer webs 21 of each clamping element 12, into which a threaded stud 17 can be screwed. Alternatively, instead of the fork-shaped design of the wide ends 13 of the clamping elements 12, it is also possible to form the wide ends 13 in one piece such that the threaded bushings 15 are arranged in the radially outer region of the wide ends 13 and the threaded studs 17, which are screwed into the threaded bushings 15, deform the radially inner region when screwed into the threaded bushings 15 so that the desired contact pressure can be adjusted.

[0050] In order to secure the clamping elements 12 designed in this way against rotation when screwing the threaded pins 17 into the threaded bushings 15 which are only supported in the radially outer webs 21, and to ensure a constant contact pressure, a pin 23 pointing outwards away from the sliding bearing bushing 7 is formed at the wide end 13 of the radially inner web 22 of each clamping element 12, which engages in a corresponding groove 24 formed in the fixing element 20.

[0051] The threaded studs 17, screwed into the threaded bushings 15 of the radially outer webs 21 of the clamping elements 12, protrude from the threaded bushings 15 at their lower end and contact the radially inner webs 22 of the clamping elements 12. By further screwing the threaded studs 17 into the threaded bushing 15, the radially outer webs 21 of the clamping elements 12 are pressed radially outwards against the running surface 11 of the second housing component 4 by the threaded studs 17, which are contacting the radially inner webs 22, as shown by the double arrow 25 in Fig. 6. This clamping of the webs 21 and 22 creates the desired variably adjustable contact pressure on the sliding bearing 6.

[0052] With a bearing arrangement 5 for a plain bearing 6 constructed as described above, it is possible to compensate for manufacturing tolerances and ensure sufficient contact pressure. 1 medical instrument instrument housing

[0053] first housing component

[0054] second housing component bearing arrangement

[0055] Plain bearings

[0056] Plain bearing bushing

[0057] inner running surface (plain bearing bushing) outer running surface (plain bearing bushing) 10 Running surface (first housing component) 11 Running surface (second housing component) 12 Clamping element

[0058] 13 wide end (clamping element)

[0059] 14 internal threads

[0060] 15 threaded bushing

[0061] 16 bore

[0062] 17 Threaded pin

[0063] 18 elongated holes

[0064] 19 longitudinal slots

[0065] 20 fixing element

[0066] 21 Bridge (radial outer)

[0067] 22 Bridge (radial inside)

[0068] 23 cones

[0069] 24 Nut

[0070] 25 Double Arrow

[0071] first area

[0072] II second area

[0073] D contact pressure

Claims

Patent claims 1. Medical instrument (1) with an instrument housing (2), with a first housing component (3) and a second housing component (4), which are rotatable relative to each other by means of a bearing arrangement (5) for a sliding bearing (6), wherein the bearing arrangement (5) comprises a sliding bearing bushing (7) with an inner running surface (8) and an outer running surface (9) as well as a running surface (10) formed on the first housing component (3), which is in operative contact with the inner running surface (8) of the sliding bearing bushing (7) and a running surface (11) formed on the second housing component (4), which is in operative contact with the outer running surface (9) of the sliding bearing bushing (7), characterized by this , that the running surface (11) of the second housing component (4), which is in operative contact with the outer running surface (9) of the sliding bearing bushing (7), has, when viewed over the circumference of the outer running surface (9) of the sliding bearing bushing (7), a first area (I) in which this running surface (11) is in direct contact with the outer running surface (9) of the sliding bearing bushing (7), and a second area (II) in which this running surface (11) is spaced apart from the outer running surface (9) of the sliding bearing bushing (7), and that clamping elements (12) can be placed in the second area (II) by means of which the outer running surface (9) of the sliding bearing bushing (7) can be force-fitted to the running surface (11) of the second housing component (4).

2. Medical instrument (1) according to claim 1, characterized in that two clamping elements (12) are provided which are wedge-shaped when viewed in the circumferential direction of the running surface (11) of the second housing component (4).

3. Medical instrument (1) according to claim 2, characterized in that the two wedge-shaped clamping elements (12) are spaced apart from each other in the circumferential direction of the running surface (11) of the second housing component (4) such that the wide ends (13) of the wedge-shaped clamping elements (12) face each other.

4. Medical instrument (1) according to one of claims 1 to 3, characterized in that a threaded bushing (15) provided with an internal thread (14) is arranged in each clamping element (12) and a bore (16) extending radially to the sliding bearing bushing (7) is formed in the second housing component (4) for each clamping element (12), through which a threaded pin (17) is inserted into the threaded bushing (15) of the respective clamping element (12) can be screwed in, wherein the outer geometry of the threaded bushings (15) is larger than the inner diameter of the radial bores (16) in the second housing component (4).

5. Medical instrument (1) according to claim 4, characterized in that the radial bores (16) in the second housing component (4) are designed as elongated holes (18) extending transversely to the running surface (11) of the second housing component (4).

6. Medical instrument (1) according to claim 3, characterized in that the wide ends (13) of the wedge-shaped clamping elements (12) are formed in a fork shape, consisting of two radially spaced webs (21, 22).

7. Medical instrument (1) according to claim 6, characterized in that a threaded bushing (15) provided with an internal thread (14) is arranged in the radially outer webs (21) of each clamping element (12) and a bore (16) extending radially to the sliding bearing bushing (7) is formed in the second housing component (4) for each clamping element (12), through which a threaded pin (17) can be screwed into the threaded bushing (15).

8. Medical instrument (1) according to claim 7, characterized in that the radially outer webs (21) of the clamping elements (12) can be pressed radially outwards against the running surface (11) of the second housing component (4) via the threaded studs (17) which can be screwed into the threaded bushings (15) with the radially inner webs (22) of the clamping elements (12) as abutments for the threaded studs (17).

9. Medical instrument (1) according to one of claims 1 to 8, characterized in that a three-point load distribution of the contact pressure on the sliding bearing (6) can be adjusted via the clamping elements (12) in the circumferential direction of the running surface (11) formed on the second housing component (4).

10. Medical instrument (1) according to one of claims 1 to 9, characterized in that a continuous longitudinal slot (19) extending transversely to the running surfaces (8 and 9) is formed in the sliding bearing bushing (7).

11. Medical instrument (1) according to claim 10, characterized in that a fixing element (20) which can be fixed to the second housing component (4) can be inserted into the longitudinal slot (19), wherein the fixing element (20) defines the longitudinal slot (19) circumferential direction of the outer running surface (9) of the sliding bearing bushing (7) is considered.

12. Medical instrument (1 ) according to one of claims 6 to 11 , characterized in that the radially inner webs (22) of each clamping element (12) can be fixed to the fixing element (20) with their wide ends (13).

13. Medical instrument (1) according to claim 12, characterized in that the fixing of each clamping element (12) is effected by means of a pin (23) formed on the wide end (13) of each radially inner web (22), which points outwards from the sliding bearing bushing (7) and engages in a corresponding groove (24) in the fixing element (20).

14. Medical instrument (1 ) with a bearing arrangement according to one of claims 1 to 13, characterized in that the medical instrument (1) is an exoscope mounted on a holding arm.

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