Linear drive device for converting a rotational movement into a linear movement and medical device, in particular a patient support table or an imaging device, comprising a linear drive device

Abstract

Linear drive device for converting a rotational movement into a linear movement, - comprising an outer housing (3) and an inner housing (8) mounted in the outer housing (3) by means of at least one main bearing (10) such that the inner housing (8) is rotatably movable about a main axis (11) fixed relative to the outer housing (3) and is mounted in a linear manner along the main axis (11), - wherein a ring (9) is mounted in the inner housing (8) by means of at least one ring bearing (12) such that the ring (9) is rotatably movable about a ring axis (13) fixed relative to the inner housing (8) and is mounted in a linear manner along the ring axis (13), - wherein a spindle (4) is provided which extends along the main axis (11) and passes through the outer housing (3), the inner housing (8) and the ring (9), - wherein an inner contour (14) is provided on an inner surface of the ring (9) and an outer contour (15) is provided on an outer surface of the spindle (4), - wherein the main axis (11) and the ring axis (13) are arranged relative to one another in such a way that the inner housing (8) and the ring (9) are mounted eccentrically relative to one another and the outer contour (15) and the inner contour (14) are locally in engagement with one another along a circumferential direction (16) extending around the main axis (11), - wherein the interacting inner contour (14) and outer contour (15) bring about a linear movement of the spindle (4) along the main axis (11) upon rotation of the ring (9) about the ring axis (13), characterized by at least one securing element (30), wherein an element engagement contour (31) of the securing element (30) engages with a ring engagement contour (33) of the ring (9) locally along the circumferential direction (16) such that sliding of the outer contour (15) relative to the inner contour (14) is blocked, wherein the securing element (30) is a securing ring or a securing sleeve with an external toothed ring as the element engagement contour (31), wherein the ring (9) has a sleeve section (32), in particular on the end face, with an internal toothed ring as the ring engagement contour (33).

Description

[0001] The present invention relates to a linear drive device for converting a rotational movement into a linear movement. The present invention also relates to a medical device, in particular a patient support table or an imaging device, comprising a first component and a second component movable relative to the first component.

[0002] A linear drive device serves the purpose of mechanically coupling at least two components in such a way that a rotational or rotary movement of one of the components is converted into a linear or feed movement of the other component, and vice versa. Rolling screw drives, for example, are known for this purpose from the prior art. These can be implemented as a ball screw or as a planetary roller screw drive.

[0003] In a screw drive with a recirculating ball screw, balls are guided in a helical guideway formed on the outside of the spindle. A guide carriage is arranged along the longitudinal direction of the spindle, which is mounted on the spindle via the balls. A rotary motion between the spindle and the guide carriage results in a feed motion between these components.

[0004] In a planetary roller screw drive, planetary rollers are mounted in a revolving nut in such a way that rotation of the revolving nut around a threaded spindle causes an axial relative movement between the revolving nut and the threaded spindle. The advantage of a planetary roller screw drive is that, due to the rolling movements involved, very little wear occurs. Furthermore, a targeted selection of the diameters of the threaded spindle and the planetary rollers makes it possible to implement a gear function with a specific gear ratio. The use of a planetary roller screw drive therefore allows it to be used in the form of a so-called direct drive, so that the planetary roller screw drive, which acts as the drive machine, and the component to be driven are directly connected without the need for a separate gear unit in between. The disadvantage of the planetary roller screw drive is that it is complex to manufacture.

[0005] The relevant prior art includes the documents DE 101 48 970 A1, DE 10 2020 105 928 A1, DE 40 02 151 A1, DE 10 2016 209 161 A1, DE 36 16 905 A1 and DE 23 58 882 A1.

[0006] The present invention has for its object to provide an improved concept for a linear drive device, in particular so that on the one hand the advantages of a planetary roller screw drive are realized and on the other hand a simpler manufacture and realization is provided.

[0007] According to the invention, the object is achieved in a linear drive device of the type mentioned at the outset in that - it comprises an outer housing and an inner housing mounted in the outer housing by means of at least one main bearing such that the inner housing is rotatably movable about a main axis fixed with respect to the outer housing and is mounted linearly fixed along the main axis, - wherein a ring is mounted in the inner housing by means of at least one ring bearing such that the ring is rotatably movable about a ring axis fixed with respect to the inner housing and is mounted linearly fixed along the ring axis, - wherein a spindle is provided which extends along the main axis and passes through the outer housing, the inner housing and the ring, - an inner contour is provided on an inner surface of the ring and an outer contour is provided on an outer surface of the spindle, - wherein the main axis and the ring axis are arranged relative to each other in such a way that the inner housing and the ring are mounted eccentrically to each other and the outer contour and the inner contour are locally in engagement with each other along a circumferential direction extending around the main axis, - whereby the interacting contours cause a linear movement of the spindle along the main axis when the ring rotates around the ring axis.

[0008] One of the features of the linear drive device according to the invention is that the main axis and the ring axis are arranged relative to one another in such a way that the inner housing and the ring are mounted eccentrically to one another. This is achieved, for example, by having the main axis and the ring axis run parallel and spaced apart from one another. Preferably, the main axis and the ring axis run approximately parallel or exactly parallel.

[0009] The present invention is based in particular on the idea that the spindle and the ring are mounted eccentrically, in particular axially parallel and slightly offset, to one another, so that the contours of these components engage laterally. A rotary movement of the inner housing about the main axis leads, due to a drag effect, to a co-directional rotary movement of the ring about the ring axis and vice versa. The rotary movement of the ring about the ring axis, in turn, occurs in such a way that it rolls around the spindle. This rolling movement can be compared to the movement of a hula hoop around the dancer. One of the advantages of the present invention is that the advantages explained at the beginning in connection with the planetary roller screw drive are also realized in the linear drive device according to the invention.For example, to implement the gear function and consequently to enable a direct drive, the outer diameter of the spindle and the inner diameter of the ring can differ from one another in such a way that a speed transmission takes place between the inner housing and the ring during the rotation of the inner housing and the coupled rotation of the ring around the spindle. Consequently, the quotient or the size ratio of the diameter of the ring and the diameter of the spindle determines the transmission ratio of the gear function in the linear drive device according to the invention. By appropriately selecting these diameters, the feed rate, i.e. the distance covered per rotational revolution with regard to the linear movement, can be specifically adjusted. Consequently, an embodiment of the linear drive device according to the invention can be realized in which only a small feed is generated at high speeds.On the other hand, an embodiment can be realized in which a comparatively larger feed rate is generated even at low speeds.

[0010] In addition to this advantage, the linear drive device according to the invention represents a simplification of the known planetary roller screw drive. Thus, in the linear drive device according to the invention, all components rotate in the same direction, which reduces the relative movements that occur and thus the resulting friction losses and wear. Furthermore, the present invention realizes a robust design, since delicate components such as gears are not required.

[0011] The linear drive device according to the invention comprises the outer housing and the inner housing mounted in the outer housing by means of the at least one main bearing such that the inner housing is rotatably movable about a main axis that is stationary with respect to the outer housing and is mounted linearly along the main axis. The outer housing can be made of a plastic and / or a metal. The main axis can be a central or symmetrical axis of the inner housing. Further components of the linear drive device are housed in the outer housing, such as the inner housing, the ring, and a section of the spindle. The spindle, which can also be referred to as a rod or shaft, extends according to the invention along the main axis such that a longitudinal axis of the spindle and the main axis coincide. The main bearing enables a rotary movement of the inner housing around the spindle.The main bearing is designed in such a way, for example by means of appropriate stops, that it is not possible to move the inner housing along the main axis and thus along the spindle.

[0012] Furthermore, the invention provides that the ring is mounted in the inner housing by means of the at least one ring bearing in such a way that it is rotatably movable about a ring axis that is fixed with respect to the inner housing and linearly fixed along the ring axis. The inner housing and / or the ring can be made of a plastic and / or a metal. The ring axis can be a central or symmetrical axis of the ring. Further components of the linear drive device, such as the ring and a section of the spindle, are housed in the inner housing. A rotary movement of the ring about the ring axis is made possible by means of the ring bearing. The main axis and the ring axis run in particular parallel to one another, but are not identical.As the system rotates, an eccentricity occurs between the inner housing and the ring, and thus between the spindle and the ring. The main axis is stationary relative to the outer housing and the spindle, and the ring axis rotates around the main axis. The ring bearing is designed in such a way, for example by means of appropriate stops, that displacement of the ring along the ring axis and thus along the spindle is impossible.

[0013] The diameters and rotation radii of the components involved, in particular the spindle, the ring, and the inner housing, are such that the outer contour of the spindle and the inner contour of the ring engage locally with each other along the circumferential direction extending around the main axis. The term "local" here means that this engagement does not occur over the entire circumference, as would be the case if the eccentricity were absent and the diameters of the spindle and the ring were the same, but only over a partial section of the circumference. Within this partial section, the contours, in particular, merge into and out of each other.

[0014] The inner contour and the outer contour can be adapted to each other in terms of their geometric shape. Preferably, one of the contours represents a negative of the other contour. The outer contour and / or the inner contour can have an oblique shape relative to the main axis, so that the relative movement between the contours occurring during the rotation of the ring around the spindle causes the feed movement of the spindle. The contours can have elongated, interlocking structures that roll against each other along their longitudinal direction as the ring rotates around the spindle, in particular to achieve the lowest possible friction.

[0015] Preferably, the outer contour of the spindle and the inner contour of the ring are in frictional engagement. This means that the forces occurring during rotation and the rolling of the ring around the spindle are transmitted by frictional forces, more precisely by static frictional forces, since the surfaces involved are pressed against each other. During normal operation of the linear drive device, the frictional forces that occur are usually small enough that sliding of the surfaces, or in other words, slippage between the inner contour and the outer contour, does not occur.

[0016] The outer contour is preferably an external thread. Thus, the spindle can be a threaded rod. The external thread can have an outer diameter between 0.5 mm and 20 mm. Additionally or alternatively, the inner contour can be an internal thread. Thus, the ring can be a nut or screw nut, and the inner housing can be referred to as a nut housing. The internal thread can have an inner diameter between 1 mm and 30 mm. The external thread and the internal thread preferably have the same pitch.

[0017] Regarding the threads, it can be provided that the external thread and / or the internal thread is a trapezoidal thread. With a trapezoidal thread, the thread turns have a trapezoidal contour relative to a section along the main axis. Compared to other thread geometries, trapezoidal threads are easy and cost-effective to produce, especially as mass products. Due in particular to the trapezoidal shape of the threads, the ring and the spindle can be mounted with zero play relative to each other with respect to linear movement along the main axis.

[0018] As already noted above, it is intended that the main axis and the ring axis can run approximately parallel to one another. In particular, in the exemplary embodiment in which threads are provided as contours, the term “approximately parallel” can mean that a corresponding deviation is not greater than 5°, in particular not greater than 1°. With regard to the parallel course of these axes, the angular deviation in the presence of threads arises from the fact that, although the threaded rod and the nut basically have the same thread pitch, these differ slightly from one another locally due to the different diameters, i.e. also at the point of engagement of the contours. In other words, the path covered along the main axis during one revolution of the thread is the same for both threads, although the lengths along the circumferential direction differ due to the different diameters.If the threads are unwound, the thread pitch would be triangles of equal height but different lengths.

[0019] According to another possible embodiment of the linear drive device according to the invention, the inner contour is a circumferential projection. The projection can be slopeless, i.e., extend only along the circumferential direction, but not diagonally along the main axis. In a simple case, the ring having the circumferential projection is a perforated disc. Its extent along the main axis is small enough that the disc edge, as the inner contour, engages the outer contour, in particular, into a thread of the external thread.

[0020] Regarding the feature that the main axis and the ring axis can run approximately parallel to each other, in this embodiment, this can mean a corresponding deviation greater than 5°. For example, the circumferential projection can engage the thread so that the angular position of the ring axis corresponds to the thread pitch of the spindle. This angle may also be greater than 5°.

[0021] The at least one main bearing and / or the at least one ring bearing can be a ball bearing or a roller bearing. Balls or rollers are provided between two concentric bearing surfaces. The bearing surfaces can be formed on bearing rings of the respective bearing, which are attached to the components to be connected by the bearing. The bearing surfaces can be outer surfaces of the respective components to be connected by the bearing.

[0022] It can be provided that the inner housing has an outer surface that is at least partially rotationally symmetrical about the main axis and an inner surface that is at least partially rotationally symmetrical about the ring axis and eccentric with respect to the outer surface, wherein the main bearing couples the outer surface to the outer housing and the ring bearing couples the inner surface to the ring. In other words, the hollow inner housing has an interior whose geometric shape is arranged eccentrically to the geometric outer shape of the inner housing. The deviation between the main axis and the ring axis is realized in this embodiment by the specific geometric design of the inner housing. A central axis of symmetry of the outer shape of the inner housing coincides with the main axis. A central axis of symmetry of the interior space of the inner housing coincides with the ring axis.At least a part of the rotationally symmetrical outer surface and / or the rotationally symmetrical inner surface can be connected to one of the bearing rings or form one of the bearing surfaces.

[0023] Alternatively, the outer surface of the inner housing and the inner surface of the inner housing can be arranged concentrically with each other. According to this embodiment, the deviation between the main axis and the ring axis can be realized by means of an elastic spring element. This can press the ring laterally onto the spindle, thus causing the contours to engage. The elastic spring element can be supported on the inner surface of the inner housing on one side and on an outer surface of the ring on the other.

[0024] The linear drive device according to the invention has at least one securing element, wherein an element engagement contour of the securing element engages with a ring engagement contour of the ring locally along the circumferential direction, so that sliding of the outer contour relative to the inner contour is blocked. The securing element can be arranged stationary with respect to the outer housing, in particular fastened thereto. As already mentioned, the frictional forces occurring between the inner contour and the outer contour are usually small enough that slippage between the inner contour and the outer contour does not occur. However, in practice, particularly when the components are subject to high stress, it cannot be ruled out that the static friction between the inner contour and the outer contour is overcome and slippage occurs. This is disadvantageous with regard to smooth motion control.This is also disadvantageous when a stepper motor is used as the drive for the linear drive device. Individually pulsed current or control signals cause the rotor of the stepper motor to rotate step by step, which is then transmitted to the inner housing of the linear drive device. These signals can be used to draw conclusions about the linear movement traveled. This is only possible if the outer contour does not slip relative to the inner contour, which can be ensured by the engagement contours.

[0025] The securing element is a securing ring or a securing sleeve with an external gear ring as the element engagement contour. The ring can have a sleeve section with an internal gear ring as the ring engagement contour. According to this embodiment, the gear rings have different diameters to enable engagement at one point or locally along the circumferential direction. The sleeve section can be attached or formed on the end face of the ring. The sleeve section can form a section of the ring with an enlarged diameter, into which the securing ring or securing sleeve is axially inserted. According to one conceivable embodiment, the ring has a sleeve section with an internal gear ring at each of its end faces. Accordingly, in this embodiment, two securing rings or securing sleeves with an external gear ring are provided.

[0026] With regard to the outer housing, it is preferably provided that it has two openings, each with a connecting piece arranged thereon, wherein the spindle passes through the connecting pieces. The longitudinal directions of the connecting pieces extend along the main axis, so that each of the connecting pieces encompasses a part of the spindle. An inner diameter of the connecting pieces preferably corresponds approximately to the outer diameter of the spindle or is slightly larger. Consequently, the connecting pieces implement linear guide bearings for the spindle. The connecting pieces, which can also be referred to as pipe pieces, can be made of a plastic and / or a metal. The connecting pieces can be welded to the outer housing. The connecting pieces preferably protrude into the interior of the outer housing, in particular in order to implement a flush shape of the outer surface of the outer housing.

[0027] If the securing element explained above and designed as the securing ring or the securing sleeve is provided, the securing element is preferably the nozzle.

[0028] Furthermore, the inner housing can be mounted on the outer housing via the connecting piece. Accordingly, one of the bearing rings of the respective bearing can be attached to the connecting piece. It is also conceivable that one of the bearing surfaces of the respective bearing is provided as the outer surface of the connecting piece.

[0029] In principle, it is conceivable for the spindle to be mounted or capable of being mounted so that it can rotate relative to the main axis. Preferably, the spindle is mounted or capable of being mounted so that it can rotate relative to the main axis. This creates the disadvantageous possibility that the spindle will start to vibrate during longitudinal displacement, if it is also rotating at the same time. This is avoided by the rotationally fixed mounting of the spindle. With regard to the rotationally fixed mounting of the spindle, it can be provided that it is mounted in corresponding guides that allow its longitudinal displacement and block any rotational movement. The rotationally fixed mounting of the spindle can be realized in that it is fixedly or rotationally fixedly connected to a component of a device that comprises the linear drive device according to the invention, wherein this component is guided by means of corresponding guide components such as guide rails or the like.

[0030] The linear drive device according to the invention is preferably provided with or forms an electric machine by means of which a rotatably mounted component of the linear drive device, in particular the inner housing and / or the spindle, can be set in rotation. The electric machine can thus be arranged in the outer housing, wherein the electric machine and the rotatably mounted component can be connected to one another via a drive belt. The rotatably mounted component, for example the inner housing, can form a pulley that is connected to the electric machine via the drive belt. The geometric outer shape of this component, for example the inner housing, can have a circumferential guide groove for guiding the drive belt.

[0031] Particularly preferably, the linear drive device forms an electric machine with a rotor and a stator, wherein the inner housing represents the rotor of the electric machine. The linear drive device functions synergistically, firstly, as a motion converter relating to the rotational and feed movements, secondly, as a transmission gear, and thirdly, as a drive means or energy converter, by means of which electrical energy can be converted into kinetic energy. Thus, the inner housing forming the rotor can have permanent magnets or windings made of an electrically conductive wire. These interact with corresponding winding coils or permanent magnets of the stator in such a way that electrical currents are converted into a rotary movement of the rotor. The stator is a separate component from the rotor, which, like the rotor, extends rotationally symmetrically around the main axis.The stator and rotor are arranged in the outer housing. The stator surrounds the rotor along its circumference.

[0032] According to the invention, the object is further achieved by a medical device of the type mentioned above, which comprises a linear drive device as described above, wherein the first component is coupled to the spindle and the second component is coupled to the outer housing, wherein an electric machine, which is in particular a stepper motor, is provided, by means of which the inner housing or the spindle can be set in rotation. All advantages, features, and aspects explained in connection with the linear drive device according to the invention are equally applicable to the medical device according to the invention and vice versa.

[0033] In the medical device according to the invention, it is conceivable that the first component, which is coupled to the spindle, is immobile with respect to the earth- or stationary inertial system. In this case, the conversion of rotation into feed motion leads to a movement of the outer housing along the spindle, with the spindle remaining stationary in its position. It is also conceivable that the second component, which is coupled to the outer housing, is immobile with respect to the earth- or stationary inertial system. In this case, the conversion of rotation into feed motion leads to a movement of the spindle along the main axis, with the outer housing remaining stationary in its position.

[0034] The medical device according to the invention can be a patient support table. This typically comprises a support column or base as a stationary component and a tabletop forming a support surface as a movable component. Preferably, the outer housing is connected to the support column, and the spindle is connected to the tabletop. The linear drive device can thus be used to adjust the height of the tabletop.

[0035] The medical device according to the invention can also be an imaging device. In this case, too, stationary components such as stands or the like are coupled to relatively movable components such as radiation sources and / or patient support plates.

[0036] In principle, the linear drive device according to the invention can be provided as a component of any device in which components are provided that are movable relative to one another. Examples of this include machine tools such as metalworking machines, such as lathes or milling machines.

[0037] With regard to the relative movements explained in this description, it should be noted that the formulation according to the concept "a first object moves relative to a second object" equally means that the second object moves relative to the first object. In the case of a corresponding relative movement, the reference system can therefore be defined as fixed with respect to the other object. With respect to an earth- or stationary inertial system, in particular either the outer housing or the spindle is stationary. In other words, the linear or feed movement occurring within the scope of the linear drive device according to the invention, relative to the stationary inertial system, can occur either on the part of the outer housing or on the part of the spindle.

[0038] Further advantages and details of the present invention will become apparent from the following exemplary embodiments and from the figures, which schematically show: Fig. 1 a schematic diagram of a medical device according to the invention according to an embodiment, wherein the medical device represents a patient support table, Fig. 2 a sectional view of a linear drive device according to the invention according to a first embodiment, which can be used as a component of the medical device of the Fig. 1 may be provided, Fig. 3 a further sectional view of the linear drive device of the Fig. 2, where the section plane is defined by the line III - III in Fig. 2 is indicated, and Fig. 4 a sectional view of a linear drive device according to the invention according to a second embodiment, which can be used as a component of the medical device of the Fig. 1 may be provided.

[0039] Fig. Figure 1 shows an embodiment of a medical device 1 according to the invention, which is a patient support table. The medical device 1 comprises a linear drive device 2 according to the invention, by means of which a rotational or rotary movement can be converted into a linear or feed movement. The linear drive device 2 comprises an outer housing 3 and a spindle 4 guided through it. The spindle 4 is rotatable along its longitudinal axis, which is in the Fig. 1 shown situation stands vertically in space, linearly movable.

[0040] The medical device 1 comprises a first component 5 designed as a table top, which is coupled to the spindle 4. The table top is connected to the spindle 4 by means of further Fig. 1, guide components of the medical device 1, such as guide rails, are mounted for linear movement to ensure stable and secure movement of the tabletop. Furthermore, the spindle 4 is connected to the tabletop in a rotationally fixed manner, so that the spindle 4 is mounted in a rotationally fixed manner. Likewise, the spindle 4 can be mounted in a non-rotatable manner, although not provided here. The medical device 1 further comprises a second component 6 designed as a pillar or base, which is fixedly arranged on a floor or subsurface 7 and which supports the first component 5. The outer housing 3 is connected to the second component 6. Thus, the height of the medical device 1 or the tabletop is adjusted by means of the linear drive device 2.

[0041] Fig. Fig. 2 shows a sectional view with a vertical section plane through the linear drive device 2 according to the invention according to a first embodiment, as it is used in the medical device 1 of the Fig. 1. A further sectional view through the linear drive device 2 is shown in Fig. 3, where the cutting plane of the Fig. 3 by the line III - III in Fig. 2 is indicated. In addition to the outer housing 3 and the spindle 4, the linear drive device 2 comprises an inner housing 8 and a ring 9, through which, like the outer housing 3, the spindle 4 passes.

[0042] The inner housing 8 is mounted in the outer housing via two main bearings 10 such that the inner housing 8 is mounted for rotation about a main axis 11 that is fixed relative to the outer housing 3. The main axis 11 coincides with the longitudinal direction of the spindle 4. The inner housing 8 is mounted in a fixed position linearly along the main axis 11. The ring 9 is mounted in the inner housing 8 via a ring bearing 12 such that the ring 9 is mounted for rotation about a ring axis 13 that is fixed relative to the inner housing 8. The main axis 11 and the ring axis 13 run, in particular approximately, parallel to one another and diverge from one another or are spaced from one another, so that the inner housing 8 and the ring 9 are mounted eccentrically to one another. This eccentricity is particularly well suited to Fig. 3. The two main bearings 10 and the ring bearing 12 are each designed as a ball bearing, but can equally be, for example, a roller bearing or another suitable bearing.

[0043] An inner contour 14 representing an internal thread is provided on an inner surface of the ring 9, and an outer contour 15 representing an external thread is provided on an outer surface of the spindle 4. The spindle 4 is a threaded rod with a circular cross-section, and the ring 9 is a screw nut. Alternatively, instead of the internal thread, the ring 9 can have a circumferential projection, in particular one with a smooth pitch, as the inner contour 14, in which case the ring 9 can be a perforated disc. In the present case, however, the inner contour 14 and the outer contour 15 each represent a thread, namely a trapezoidal thread.

[0044] The inner contour 14 and outer contour 15 are locally engaged with one another in a force-locking manner along a circumferential direction 16 extending around the main axis 11. In particular, the thread pitches of the inner contour 14 and outer contour 15 are, in particular approximately, identical, so that the engaging sections of the inner contour 14 and outer contour 15 are identical images or negatives of each other.

[0045] As mentioned, the main axis 11 and the ring axis 13 do not necessarily run exactly parallel to each other, but can also run approximately parallel. This results from the fact that the threads of the spindle 4 and the ring 9, although they generally have the same pitch, differ slightly locally or in the area of ​​engagement due to the different diameters. The engagement therefore results in a slight tilt of the two axes 11, 13 relative to each other.

[0046] The following explains the concept implemented in the present invention for converting rotational movement into linear movement and vice versa. The initial situation is assumed to be a rotary movement of the inner housing 8 about the main axis 11, which results in the ring 9 being driven along due to the existing eccentricity. The rotary movement of the inner housing 8 leads to a rotary movement of the ring 9 about the ring axis 13. Due to the engagement of the inner contour 14 and outer contour 15 and their formation as a thread, the rotation of the ring 9 about the ring axis 13 leads to the inner contour 14 and outer contour 15 rolling against each other and, due to the inclined position of the threads, a linear feed of the spindle 4 along the main axis 11 is caused.

[0047] This highlights one of the central advantages of the present invention, namely the implementation of a gear function in the linear drive device 2 and thus the enabling of a direct drive in the medical device 1. Thus, the outer diameter 17 of the spindle 4 and the inner diameter 18 of the ring 9 differ from one another in such a way that upon rotation of the inner housing 8 and the associated rotation of the ring 9, a speed transmission occurs between the inner housing 8 and the ring 9. The ratio of the outer diameter 17 and the inner diameter 18 determines the transmission ratio of the gear function.

[0048] Specific details regarding the structure of the linear drive device 2 and its components are presented below. The eccentricity described above is achieved by the inner housing 8 having an outer surface 19 that is rotationally symmetrical about the main axis 11. Furthermore, the inner housing 8 has an inner surface 20 that is rotationally symmetrical about the ring axis 13, eccentric with respect to the outer surface 19, and delimits an interior space 21 of the hollow inner housing 8. The main bearings 10 couple the outer surface 19 to the outer housing 3, and the ring bearing 12 couples the inner surface 20 to the ring 9.

[0049] The eccentricity can alternatively be realized according to an embodiment not shown in the figures. Here, the outer surface 19 and the inner surface 20 of the inner housing 8 are arranged concentrically. The deviation between the main axis 11 and the ring axis 13 is realized by means of an elastic spring element that presses the ring 9 laterally onto the spindle 4, thus causing the inner contour 14 and outer contour 15 to engage. The elastic spring element is supported on the one hand on the inner surface 20 of the inner housing 8 and on the other hand on a radial outer surface of the ring 9.

[0050] With regard to the outer housing 3, it is provided that it has two openings diametrically opposed along the main axis 11, wherein at each of the openings a nozzle 23 protruding into the interior 22 of the outer housing 3 is provided. The nozzles 23 have an inner diameter that is slightly larger than the outer diameter 17 of the spindle 4, which extends through the nozzles 23. The nozzles 23 thus represent linear guide bearings for the spindle 4. Furthermore, with regard to the nozzles 23, it is provided that a radial outer surface thereof forms a bearing surface for one of the main bearings 10. Consequently, the inner housing 8 is mounted on the outer housing 3 via the two nozzles 23.

[0051] With further reference to Fig. 1, the linear drive device 2 has an electric motor 24, by means of which the inner housing 8 can be set in rotation. The two alternatives explained below are conceivable for this purpose.

[0052] Thus, with regard to the first alternative, the inner housing 8 and the electric motor 24 are separate components. The electric motor 24 is arranged in the outer housing 3. The inner housing 8 is a pulley with a circumferential belt groove 25 in which a belt (not shown in detail in the figures) is guided. The rotary motion generated by the electric motor 24 is transmitted to the inner housing 8 via the belt.

[0053] With regard to the second alternative, it is provided that the linear drive device 2 itself forms the electric machine 24, wherein said machine has a stator 26 and a rotor 27. The rotor 27 is realized here by the inner housing 8. The inner housing 8 forming the rotor 27 can have windings 28 made of an electrically conductive wire, which interact electromagnetically with permanent magnets 29 of the stator 26 in order to convert electrical energy into kinetic energy, i.e. into a rotational movement of the rotor 27. To clarify that the corresponding components, like the belt groove 25, are merely optional, the stator 26, the windings 28 and the permanent magnets 29 are shown in the Fig. 2 indicated by dashed lines.

[0054] The electric machine 24 is a stepper motor. Thus, the electric machine 24 generates a stepwise rotation of the rotor 27, which is generated by individually pulsed current or control signals. Based on these signals, conclusions can be drawn regarding the rotational movement of the inner housing 8 and thus the corresponding linear movement of the spindle 4. A potential problem is that, with sufficiently large force transmissions, the inner contour 14 and outer contour 15 could slip or slide away from each other, making the just-described use of the current or control signals for determining the linear movement impossible. Fig. 4 shows a sectional view through the linear drive device 2 according to the invention according to a second embodiment, which is also used in the medical device 1 of the Fig. 1 and by which this problem is overcome. Apart from the points explained below, the Fig. 4 shown linear drive device 2 of the Fig. 2 shown.

[0055] For example, the Fig. The linear drive device 2 shown in Figure 4 has a securing element 30 designed as a securing sleeve or as a securing ring. The securing element 30 is implemented by one of the connecting pieces 23. The securing element 30, which protrudes inwardly and outwardly in the illustrated embodiment, has an element engagement contour 31 at its front end, which is implemented as an external gear ring. The ring 9 has a front sleeve section 32, on which a ring engagement contour 33 designed as an internal gear ring is formed. The element engagement contour 31 and ring engagement contour 33 are arranged at the mutually facing front ends of the securing element 30 and the ring 9. The element engagement contour 31 and ring engagement contour 33 engage with each other locally along the circumferential direction 16.This overcomes the problem just mentioned regarding slippage of the inner contour 14 and outer contour 15 during large power transmissions. The use of a stepper motor as the electric machine 24 is therefore readily possible, particularly in this embodiment.

[0056] Again referring to Fig. 4, it is also conceivable that the ring 9 also has a corresponding sleeve section 32 with a ring engagement contour 33 at the other end, which interacts with an element engagement contour 31 of the other nozzle 23 as described.

[0057] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0058] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

[1] Linear drive device for converting a rotational movement into a linear movement, - comprising an outer housing (3) and an inner housing (8) mounted in the outer housing (3) by means of at least one main bearing (10) such that the inner housing (8) is rotatably movable about a main axis (11) fixed relative to the outer housing (3) and is mounted in a linear manner along the main axis (11), - wherein a ring (9) is mounted in the inner housing (8) by means of at least one ring bearing (12) such that the ring (9) is rotatably movable about a ring axis (13) fixed relative to the inner housing (8) and is mounted in a linear manner along the ring axis (13), - wherein a spindle (4) is provided which extends along the main axis (11) and passes through the outer housing (3), the inner housing (8) and the ring (9), - wherein an inner contour (14) is provided on an inner surface of the ring (9) and an outer contour (15) is provided on an outer surface of the spindle (4), - wherein the main axis (11) and the ring axis (13) are arranged relative to one another in such a way that the inner housing (8) and the ring (9) are mounted eccentrically relative to one another and the outer contour (15) and the inner contour (14) are locally in engagement with one another along a circumferential direction (16) extending around the main axis (11), - wherein the interacting inner contour (14) and outer contour (15) cause a linear movement of the spindle (4) along the main axis (11) upon rotation of the ring (9) about the ring axis (13) characterized byat least one securing element (30), wherein an element engagement contour (31) of the securing element (30) engages with a ring engagement contour (33) of the ring (9) locally along the circumferential direction (16) such that sliding of the outer contour (15) relative to the inner contour (14) is blocked, wherein the securing element (30) is a securing ring or a securing sleeve with an external toothed ring as the element engagement contour (31), wherein the ring (9) has a sleeve section (32), in particular on the end face, with an internal toothed ring as the ring engagement contour (33). [2] Linear drive device according to claim 1, characterized by that the outer contour (15) and the inner contour (14) are in frictional engagement with each other. [3] Linear drive device according to claim 1 or 2, characterized by that the outer contour (15) is an external thread, and / or that the inner contour (14) is an internal thread or a circumferential projection. [4] Linear drive device according to claim 3, characterized by that the external thread and / or the internal thread is a trapezoidal thread. [5] Linear drive device according to one of the preceding claims, characterized by that the at least one main bearing (10) and / or the at least one ring bearing (12) is a ball bearing or a roller bearing. [6] Linear drive device according to one of the preceding claims, characterized by that the inner housing (8) has an outer surface (19) which is at least partially rotationally symmetrical about the main axis (11) and an inner surface (20) which is at least partially rotationally symmetrical about the ring axis (13) and eccentric with respect to the outer surface (19), wherein the main bearing (10) couples the outer surface (19) to the outer housing (3) and the ring bearing (12) couples the inner surface (20) to the ring (9). [7] Linear drive device according to one of the preceding claims, characterized bythat the outer housing (3) has two openings, each with a connecting piece (23) arranged thereon, wherein the spindle (4) passes through the connecting pieces (23). [8] Linear drive device according to one of the preceding claims, characterized by that the securing element (30) provided as the securing ring or the securing sleeve is the nozzle (23). [9] Linear drive device according to claim 7 or 8, characterized by that the inner housing (8) is mounted on the outer housing (3) via the nozzle (23). [10] Linear drive device according to one of the preceding claims, characterized by that the spindle (4) is mounted or can be mounted in a rotationally fixed or rotationally movable manner with respect to the main axis (11). [11] Linear drive device according to one of the preceding claims, characterized bythat it forms an electrical machine (24) with a rotor (27) and a stator (26), wherein the inner housing (8) represents the rotor (27) of the electrical machine (24). [12] Medical device comprising a first component (5) and a second component (6) movable relative to the first component (5), characterized by that the medical technology device (1) has a linear drive device (2) according to one of the preceding claims, wherein the first component (5) is coupled to the spindle (4) and the second component (6) is coupled to the outer housing (3), wherein an electric machine (24) is provided by means of which the inner housing (8) or the spindle (4) can be set in rotation. [13] Medical device according to claim 12, characterized by that the electrical machine (24) is a stepper motor.

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