Linear units and systems

Abstract

The present invention relates to a linear unit (10) and a system (100) comprising the linear unit (10). The linear unit (10) comprises: i) a housing (12), ii) a screw (14) rotatably mounted within the housing (12), iii) a nut (16) cooperating with the screw (14), and iv) two mounting assemblies (30) for mounting the housing (12) onto an external structure (E). Each mounting assembly (30) comprises at least two trunnions (32) arranged laterally relative to the screw (14). The trunnions (32) are preferably movably mounted in bearing housings (34) arranged on opposite sides of the screw (14).

Description

Technical Field

[0001] The present invention relates to a linear unit and a system comprising the linear unit. Background Technology

[0002] Linear units are known in the art for moving and positioning components such as machine parts. Such linear units convert rotary motion (e.g., the rotation of a motor) into linear motion. For this purpose, a rotatable screw and a mating nut are provided. When the screw is rotated by a motor, the nut moves linearly along the screw. The movement of the nut can be transmitted to the machine part, for example, via a push rod.

[0003] The durability of such linear units largely depends on the loads applied to the screw. Radial loads, in particular, which increase friction or even cause slight deformation of the screw, significantly shorten the service life of the screw and / or nut. These loads can stem not only from insufficient radial guidance of machine components but also from the thermal expansion of the linear unit's own components. Furthermore, when the linear unit is fixedly mounted to an external structure, deformation of the external structure can cause deformation of the linear unit (i.e., its components), which can also lead to the aforementioned loads. Summary of the Invention

[0004] One object of the present invention is to improve the service life of linear units, and in particular to reduce the loads acting on the linear units due to deformation of the external structure on which the linear units are mounted or thermal expansion of the linear units themselves.

[0005] This objective is achieved by the linear unit as defined in the independent claim and the system comprising the linear unit.

[0006] Preferred embodiments are given by the dependent claims and the following description.

[0007] According to a first aspect of the invention, a linear unit for converting rotational motion into linear motion comprises: i) a housing, ii) a screw rotatably mounted within the housing, iii) a nut cooperating with the screw, and iv) two mounting assemblies for mounting the housing to an external structure. Each mounting assembly comprises at least two trunnions arranged laterally relative to the screw, particularly laterally relative to the axis of rotation of the screw. The trunnions are preferably movably mounted in a bearing housing, preferably annular, and arranged on opposite sides of the screw, particularly on opposite sides of the axis of rotation of the screw.

[0008] One aspect of the invention is based on the idea of ​​flexibly, particularly articulatedly, mounting linear units to an external structure so that deformation of the external structure is not transmitted to the linear unit, particularly not to the housing and / or the screws themselves. To this end, preferably, the linear unit includes a mounting system for mounting the linear unit to the external structure such that even if the external components deform, the linear unit (especially the screws and / or housing) retains its original shape and / or orientation. The original shape preferably corresponds to the shape under no-load conditions. For example, when the mounting point of the linear unit to the external structure shifts due to deformation of the external structure, the mounting system can be configured to self-align the linear unit. In this way, the linear unit (especially the mounting system) can at least partially compensate for the misalignment between the linear unit and the external structure caused by deformation during operation. Furthermore, the linear unit (especially the mounting system) can also at least partially compensate for changes in the distance between mounting points of the linear unit due to thermal expansion of the linear unit itself.

[0009] Preferably, the linear unit includes two mounting assemblies for mounting the housing of the linear unit to an external structure (e.g., at four mounting points). The mounting assemblies are advantageously configured to hold the linear unit (especially the nut and / or housing) in an unloaded state, particularly regardless of the position of the four mounting points relative to the linear unit. In other words, the four mounting points can move relative to the linear unit within a certain range, taking into account deformation of the external structure due to thermal expansion or external loads, without exerting any force on the linear unit.

[0010] For example, each of the two mounting components may include two trunnions movably mounted in its respective bearing housing. In this way, the bearing housing or trunnion can move independently with the deformation of the external structure or the thermal expansion of the linear unit, without transmitting or only partially transmitting that movement to the corresponding mating component. In other words, by movably mounting the trunnions in the bearing housing, the trunnions and the bearing housing—and consequently the linear unit and the external structure—are preferably movably decoupled to a certain extent. For example, the trunnions movably mounted in the bearing housing may be rotatable, pivotable, and / or translational (i.e., linearly movable) relative to the bearing housing. This means that the trunnions can rotate, oscillate, and / or move linearly relative to the bearing housing. For this purpose, the trunnions may be accommodated in a corresponding seat within the bearing housing. The seat may, for example, be arranged in a rotatable and / or rotatable manner within the bearing housing. Alternatively or concurrently, the seat may allow the trunnions to make translational (linear) movements relative to the bearing housing.

[0011] By providing such a mounting system for the linear unit, and in particular the two mounting components mentioned above, the functionality and reliability of the linear unit over the long term can be ensured.

[0012] The nut and screw are preferably engaged by a plurality of planetary rollers arranged radially therebetween, thus forming a planetary roller screw drive mechanism. Alternatively, the nut and screw can also be engaged by a plurality of balls, thus forming a ball screw drive mechanism.

[0013] Preferred embodiments and further aspects of the present invention are described below. Unless explicitly excluded, they can be combined with each other and with the various aspects of the invention described below as needed.

[0014] The two mounting components are preferably arranged at opposite ends of the linear unit (especially the housing). Therefore, the screw (especially its external thread) is axially arranged between the two mounting components such that the sum of the axial distances between the nut and each mounting component is constant. This allows for a secure and reliable mounting of the linear unit to the external structure.

[0015] Unless otherwise expressly stated herein, “axial” or “along the axial direction” means the direction parallel to the longitudinal axis of the linear element, i.e., the direction parallel to the screw or its axis of rotation.

[0016] To decouple the linear unit from external structural deformation that affects the orientation of the mounting point (i.e., the orientation of the components of the mounting assembly that are fixedly connected to the external structure), at least one mounting assembly has its trunnion rotatably mounted relative to its respective bearing housing. The orientation of the mounting point can be affected, for example, by external structural bending in a plane perpendicular to the trunnion. Therefore, it is preferable to allow the trunnion to rotate relative to the bearing housing about its longitudinal axis.

[0017] To decouple external structural bending in a plane parallel to the trunnion, preferably, the trunnion of at least one mounting assembly is axially translatable relative to its respective bearing housing. For this purpose, the trunnion may have an axial clearance relative to its seat in its respective bearing housing. Here, "axial" or "along the axial direction" refers to the longitudinal axis of the trunnion. Therefore, the trunnion can preferably extend further into and / or retract from its respective seat.

[0018] In another preferred embodiment, one of the mounting components is arranged on an end cap of the linear unit, the end cap being mounted on a front end plate of the housing. The front end plate can close the housing at its front end, for example, in the region near the free end of the screw. Mounting the end cap on the front end plate provides additional degrees of freedom for the movement of the mounting components arranged at the end cap, particularly to adapt to their orientation and / or axial position.

[0019] For example, the end cap may be pivotally mounted on the front end plate of the housing and / or axially movable relative to the front end plate of the housing. In this way, the orientation and / or position of the corresponding mounting assembly can be changed without affecting the orientation and / or position of the housing.

[0020] This adaptive connection between the front end plate and the end cap can be achieved by providing an end cap comprising a cylindrical bore in which an axial protrusion of the front end plate is received. In some embodiments, the protrusion has a side surface with an annular flange. The protrusion may, for example, be formed by a cylindrical trunnion with a spherical front end. The flange of the protrusion preferably contacts the inner wall of the central bore and can slide axially along the inner wall and / or pivot relative to the inner wall.

[0021] Alternatively, the axial protrusion may be cylindrical, i.e., its side surface is completely planar. In this case, the end cap preferably includes a cavity whose inner wall portion is complementary to the spherical portion of the central bearing disk. Therefore, the central bearing disk can pivot within the cavity. The central bearing disk preferably includes a central bore in which the axial cylindrical protrusion of the front end plate can move axially. Thus, the end cap and the central bearing disk can form a central spherical bearing, and can move axially on the axial cylindrical protrusion of the front end plate.

[0022] Preferably, at least one mounting component has a trunnion with a mounting base for securing the trunnion to an external structure. In this case, advantageously, the bearing housing of one of the mounting components is arranged in an end cap. The bearing housing is preferably formed at least partially by a groove in the end cap to receive the trunnion. A bushing may also be provided in the groove to facilitate rotation of the received trunnion relative to the end cap.

[0023] Alternatively, the trunnion of one of the mounting components extends from the end cap to opposite sides. In this case, the trunnion is preferably integral with the end cap, i.e., integrally formed with the end cap. To improve the adaptability of the end cap orientation to external structural deformation and / or linear unit thermal expansion, it is preferable that the trunnion is pivotally mounted in the bearing housing relative to the central axis of the bearing housing. In particular, the bearing housing can form a spherical bearing for the trunnion.

[0024] The central axis of the bearing housing is preferably parallel to the surface normal of the bearing housing opening, that is, parallel to the normal of the area enclosed by the bearing housing. When the bearing housing is mounted to an external structure on a mounting surface, the central axis of the bearing housing is preferably perpendicular to the mounting surface.

[0025] Another way to provide at least one additional degree of freedom in orientation and / or positioning of the trunnion of the mounting assembly disposed at the end cap relative to the external structure and / or housing is to provide an end cap including an aperture in which a central spherical bearing is disposed. In some embodiments, the central spherical bearing may be formed of a bushing having a spherical contact surface.

[0026] Preferably, the trunnions extend from the central spherical bearing along both sides of the orifice. In this case, the trunnions on both sides of the end cap can be formed by a single rod, which is accommodated by a central spherical bearing (especially an inner bushing) disposed within the orifice of the end cap. Here, the end cap is preferably integrally formed with the front end plate of the housing.

[0027] To allow the trunnion to translate axially relative to the housing, it is preferable that the trunnion extends eccentrically from the central spherical bearing. For this purpose, the inner bushing may have a seat (e.g., a cylindrical bore) to receive the trunnion (especially the single rod), which is eccentrically arranged relative to the central longitudinal axis of the bushing. With the aid of this eccentric design of the central spherical bearing, the rotational movement of the trunnion about the central axis of the bore will have a translational component in the axial direction.

[0028] Since the motion of the external structure relative to the linear unit (caused by deformation of the external structure and / or thermal expansion of the linear unit or at least some of its components) is very small compared to the size of the linear unit, for example, within a few millimeters, the central spherical bearing can be a deformable spherical bearing. This deformable spherical bearing preferably comprises an elastic material surrounding an inner bushing in which the trunnion is mounted. In particular, the elastic material is arranged between the inner bushing and an outer bushing coaxial with it. The bushing may have opposing spherical portions with the elastic material arranged therebetween. Using a deformable central spherical bearing, vibration can be absorbed. Furthermore, a certain degree of stiffness can be provided in a predefined direction, which is advantageous for the normal operation of the linear unit.

[0029] As described above, in order to enable the trunnion to pivot within the bearing housing, thereby further increasing the degrees of freedom of the linear unit in terms of motion and / or orientation relative to the external structure, the bearing housing may be formed as a spherical bearing. For this purpose, at least one mounting assembly preferably includes a bearing disc rotatably mounted within the bearing housing of the mounting assembly. Preferably, each bearing disc has a socket for receiving the corresponding trunnion. Each bearing housing has a spherical inner surface portion that complements the spherical surface of the corresponding bearing disc. Thus, the bearing disc can pivot within a cavity formed by the spherical inner surface of the bearing housing. When the bearing housing is fixedly connected to the external structure, the trunnion received by the socket of the bearing disc can therefore pivot relative to the external structure.

[0030] Alternatively, to compensate for compression or elongation of the external structure and / or linear unit, preferably, the trunnion of at least one mounting component can be translated within the bearing housing in a direction perpendicular to the longitudinal axis of the trunnion (especially in a direction parallel to the screw).

[0031] For example, at least one mounting assembly may include bearing discs rotatably mounted in a bearing housing, each bearing disc having a socket for receiving a trunnion. Preferably, the trunnion has two parallel planes contacting the opposing inner surfaces of the socket. The socket is advantageously configured as an elongated structure, allowing the trunnion to translate within the socket. For example, the socket may be formed by an elongated hole in the bearing disc. Thus, the trunnion can be independently translated within its respective bearing housing in a direction perpendicular to its longitudinal axis.

[0032] Alternatively, translation of the trunnion within the bearing housing can be achieved by having at least one mounting assembly comprising bearing discs rotatably mounted within the bearing housing, each bearing disc having a socket for receiving a trunnion. Preferably, the sockets are eccentrically positioned on the bearing discs. Rotation of the trunnion about the central axis of the bearing discs or the bearing housing also has an axial component (i.e., parallel to the screw).

[0033] The system according to a second aspect of the invention includes a first component and a second component that is movable (especially pivotable) relative to the first component. Preferably, the linear unit according to the first aspect of the invention is mounted to the first component via the mounting system (especially two mounting components), and the second component is connected to a nut of the linear unit.

[0034] In this configuration, the linear element is preferably mounted to the first component in a free-floating manner. In particular, this configuration prevents or at least significantly reduces the loads acting on the linear element (especially its screw) due to deformation of the first component and / or thermal expansion of the linear element. In other words, deformations of the first component, such as bending, torsion, and / or compression / elongation, are not transmitted to the linear element. This can significantly improve the service life of the linear element (especially its screw).

[0035] The features, characteristics, advantages, and implementations of the present invention described above will be further illustrated in the following exemplary description in conjunction with the accompanying drawings. Where appropriate, the same reference numerals are used in the drawings for the same or corresponding elements of the invention. The examples are for illustrative purposes and do not limit the invention to the combinations of features shown therein (even for functional features). Furthermore, any feature disclosed in the foregoing description and the examples below can be considered alone and can be suitably combined with features of any of the above embodiments and their further aspects. In particular, each feature described above and below can be used alone or in combination with the other features for a linear unit according to the first aspect of the invention and a system according to the second aspect of the invention. Attached Figure Description

[0036] Shown (especially schematically): Figure 1. An example of a linear cell with two mounting components; Figure 2. A cross-sectional view of an example end cap; Figure 3. Cross-sectional view of another example of an end cap; Figure 4. A three-dimensional view of yet another example of an end cap; Figure 5. Side view of an example of two mounting components; Figure 6. Side view of another example of two mounting components; Figure 7 shows an example of a flexible spherical bearing; and Figure 8 shows an example of a system comprising two components and a linear unit for pivoting the two components relative to each other. Detailed Implementation

[0037] Figure 1 illustrates an example of a linear unit 10 for converting rotary motion (e.g., the rotary motion of motor 18) into linear motion. The linear unit 10 includes a housing 12, a screw 14 rotatably mounted within the housing 12, a nut 16 cooperating with the screw 14, and two mounting assemblies 30 for mounting the linear unit 10 (especially the housing 12) to an external structure (not shown). The two mounting assemblies 30 can constitute a mounting system.

[0038] The motor 18 is operatively connected to the screw 14 via gears disposed within a gearbox 20. The gearbox 20 is located at the distal end or rear end 12b of the housing 12. Rotation of the screw 14 causes the nut 16 to move linearly along the screw 14. The nut 16 is connected to a slide 22 disposed outside the housing 12 such that the slide 22 is actuated when the nut 16 moves. The movement of the slide 22 along the housing 12 is guided by a guide rail 24 disposed on the top side of the housing 12. The slide 22 includes a connection structure 26 for connecting components (e.g., machine parts) to the slide 22.

[0039] Each mounting assembly 30 includes two trunnions 32 movably mounted in a bearing housing (not visible in Figure 1). The two trunnions 32 of each mounting assembly 30 extend perpendicularly to the longitudinal axis L of the linear unit 10 (especially relative to the screw 14). Advantageously, the two trunnions 32 of each mounting assembly 30 are arranged on opposite sides of the linear unit 10 (especially the screw 14). Thus, the linear unit 10 can be mounted to an external structure at four mounting points.

[0040] Each trunnion 32 includes a mounting base 32a for securing the respective trunnion 32 to an external structure. For this purpose, the mounting base 32a may include a through hole 32c for screwing the trunnion 32 onto the external structure (for clarity, only one through hole 32c is labeled with reference numerals).

[0041] One mounting assembly 30 is disposed at the rear end 12b of the housing 12. The other mounting assembly 30 is disposed on the end cap 40 of the linear unit 10, which is mounted on the proximal end or front end 12a of the housing 12.

[0042] Preferably, the trunnions 32 of the mounting assembly 30 located at the rear end 12b are rotatably mounted in their respective bearing housings. In other words, each component of the mounting assembly 30 is axially fixed. The trunnions 32 of the mounting assembly 30 located at the end cap 40 are preferably mounted in their respective bearing housings in a manner that allows the end cap 40 to move with additional degrees of freedom (i.e., not only rotation, but also axial and radial movement). Alternatively or additionally, the end cap 40 may also be mounted relative to the housing 12 in a manner that provides at least some of the aforementioned additional degrees of freedom.

[0043] Therefore, in the example of Figure 1, the trunnion 32 will follow any movement caused by deformation of the external structure. Since the trunnion 32 of the front mounting assembly 30 is movably mounted in its bearing housing and / or the end cap 40 is movably mounted on the front end 12a, the linear unit 10 is able to maintain its original orientation. In other words, the movement of the trunnion 32 within its respective bearing housing and / or the end cap 40 relative to the housing 12 can compensate for any deformation of the external structure, such as bending, torsion, and / or compression / elongation. Similarly, the movement of the trunnion 32 relative to its respective bearing housing can also compensate for the thermal expansion of the linear unit 10 or some of its components (especially its screw 14). Based on this, the linear unit 10 can be mounted to the external structure at its front end 12a in a free-floating manner via the mounting assembly 30. Since the components of the linear unit 10 (especially the housing 12) are inherently rigid, the mounting assembly 30 can be considered adaptive.

[0044] Figure 2 shows a cross-sectional view of an example of such end cap 40. Here, end cap 40 is movably mounted on front end plate 50 of housing 12. Front end plate 50 closes the front end of housing 12 in the region at its front end 12a, near the free end of screw 14.

[0045] The end cap 40 includes a cylindrical bore 42 in which an axial protrusion 52 of the front end plate 50 is received. Preferably, the axial protrusion 52, extending along the longitudinal axis L, is axially movable within the cylindrical bore 42. This can be used to compensate for, for example, the thermal expansion of the linear unit, or the elongation / compression of the external structure E due to external loads.

[0046] By giving the axial protrusion 52 a convex, preferably spherical, annular surface portion 54a, additional degrees of freedom for positioning and / or orientation relative to the linear unit can be achieved. The surface portion 54a can be formed by a flange 54 of the side surface 52a of the protrusion 52. Preferably, under load, the surface portion 54a contacts the inner wall of the cylindrical hole 42 in a point-contact manner. This point contact between the axial protrusion 52 and the end cap 40 allows the end cap 40 to pivot about the axial protrusion 52 and also facilitates translation along the screw axis.

[0047] In the example shown in Figure 2, the trunnion 32 is fixedly connected to the external structure E via a mounting base 32a. Specifically, the linear unit is arranged between two walls of the external structure E, and the trunnion 32 passes through an opening in said wall. The trunnion 32 is received in a recess 44 of the end cap 40. Here, the recess 44 forms a bearing housing 34 for the mounting assembly 30 arranged on the end cap 40. To facilitate the rotation of the trunnion 32 within the bearing housing 34, a bushing 36 may be optionally provided within the bearing housing 34 / recess 44.

[0048] Preferably, the trunnion 32 has an axial clearance D in the groove 44. In this way, the trunnion 32 can be linearly translated along its longitudinal axis A, so that the mounting assembly 30 arranged on the end cap 40 can self-align when the internal and external structure E in FIG2 is bent.

[0049] Figure 3 shows a cross-sectional view of another example of the end cap 40. Similar to the example shown in Figure 2, the end cap 40 is movably mounted on the front end plate 50 of the housing 12.

[0050] However, here, the end cap 40 includes a cavity 46, preferably spherical, which houses a central bearing disk 48. The inner surface portion 46a of the cavity 46 is complementary to the spherical portion 48a of the central bearing disk 48. Therefore, the central bearing disk 48 can pivot within the cavity 46. In other words, the end cap 40 and the central bearing disk 48 constitute a spherical bearing.

[0051] Preferably, the central bearing disc 48 includes a cylindrical bore 42 in which the axial protrusion 52 of the front end plate 50 is accommodated. Here, the axial protrusion 52 is cylindrical, that is, its side surface 52a is flat, so it can only make linear translation within the cylindrical bore 42.

[0052] Furthermore, unlike the example shown in Figure 2, in this example, the trunnion 32 of the mounting assembly 30 is fixedly connected to the end cap 40. In particular, the trunnion 32 is integral with the end cap 40, i.e., integrally formed with the end cap 40. The free end of the trunnion 32 is movably mounted in a bearing housing 34, which is fixedly connected to the external structure E.

[0053] In this example, the trunnion 32 is not only rotatable within the bearing housing 34, but also pivotable, particularly relative to the central axis X (indicated by the dashed line) of the bearing housing. For this purpose, the mounting assembly 30 includes a bearing disc 38 providing a seat for the free end of the trunnion 32. The bearing disc 38 includes spherical portions 38a. The inner surface portions 34a of the bearing housing 34 are formed in a complementary manner, thereby forming a spherical bearing together with the bearing disc 38.

[0054] The bearing housing 34 also includes a bore 38b for receiving the trunnion 32. The bore 38b thus forms a seat for the trunnion 32 within the bearing housing 34.

[0055] Preferably, the trunnion 32 (at least its free end) is axially movable within the bore 38b, i.e., along its longitudinal axis A (indicated by the dashed line)—thus, when the bearing housing 34 is attached to the mounting surface of the outer structure E, it moves in a direction perpendicular to the mounting surface.

[0056] Figure 4 shows a three-dimensional view of yet another example of the end cap 40. Here, the end cap 40 is fixedly connected to the front end plate 50 of the housing 12. The end cap 40 includes an eyelet 64 in which a central spherical bearing 56 is disposed. Preferably, a trunnion 32 extends from the central spherical bearing 56 along both sides of the eyelet 64. The spherical bearing 56 not only allows the trunnion 32 to rotate but also allows it to pivot about the central axis of the eyelet 64.

[0057] In this example, the trunnion 32 may be formed from a single rod 58 that passes through the eyelet 64 and the seat provided by the spherical bearing 56.

[0058] Figure 5 shows a side view of an example of two mounting components 30. The linear unit 10 is mounted to the external structure E via the mounting components 30.

[0059] One of the mounting components 30 is located at the rear end 12b of the housing 12 of the linear unit 10. This mounting component 30 includes two trunnions 32 (only one visible), which are rotatably mounted in a bearing housing 34 (again, only one visible). For ease of rotation, a bushing 36 is provided radially between each trunnion 32 and the corresponding bearing housing 34.

[0060] Another mounting assembly 30 is arranged on the end cap 40 of the linear unit 10. The end cap 40 is mounted on the front end 12a of the housing 12, particularly on its front end plate (not shown). The trunnion 32 of this mounting assembly 30 is also movably mounted in the bearing housing 34.

[0061] Compared to the mounting assembly 30 located at the rear end 12b, the trunnion 32 of the mounting assembly 30 located at the end cap 40 is not only rotatable relative to its respective bearing housing 34, but also pivotable. For this purpose, the trunnion 32 is mounted in a bearing disc 38. As described in conjunction with FIG3, the bearing disc 38 and the corresponding bearing housing 34 form a spherical bearing.

[0062] Furthermore, the trunnion 32 can also translate within its respective bearing housing 34 in a direction perpendicular to the longitudinal axis of the trunnion 32 (perpendicular to the plane of the drawing in Figure 5). In particular, the trunnion 32 can translate in a direction parallel to the longitudinal axis L of the linear unit 10.

[0063] For this purpose, the trunnion 32 of the mounting assembly 30 arranged on the end cap 40 has two parallel planes 32b that contact the inner surface 60a of the socket 60 of the bearing disc 38. Thus, the socket 60 defines the seat of the trunnion 32 within the bearing housing 34.

[0064] Advantageously, the socket 60 has an elongated structure, and the trunnion 32 has a gap within the elongated socket 60 in a direction spanning its longitudinal axis, thereby allowing for translation.

[0065] Figure 6 shows a side view of another example of the two mounting components 30. As shown in Figure 5, the linear unit 10 is mounted to the external structure E via the mounting components 30.

[0066] The mounting assembly 30 here corresponds to the mounting assembly shown in Figure 5. The only difference is that the translational capability of the trunnion 32 of the mounting assembly 30 arranged on the end cap 40 is not achieved by an elongated socket, but by setting the socket 60 eccentrically on the bearing disc 38. In other words, the socket 60 for receiving the trunnion 32 is arranged at a distance from the center of the bearing disc 38. Thus, when the bearing disc 38 rotates within the bearing housing 34, the trunnion 32 will move along a curved path and translate in a direction perpendicular to its longitudinal axis. The translation along this curved path also has a component parallel to the longitudinal axis L of the linear unit 10.

[0067] In the illustrated example, the center of the bearing housing 34 of the mounting assembly 30 arranged in the end cap 40—that is, the pivot point or pivot axis of the bearing disc 38 within the bearing housing 34—is radially offset by O relative to the longitudinal axis L. Preferably, the offset O is chosen such that when the linear unit 10 is in a neutral position relative to the external structure E (i.e., the external structure E is not deformed and the linear unit 10 is not thermally expanded), the trunnion 32 is at the same height, i.e., in the same plane parallel to the longitudinal axis. In particular, the longitudinal axis L is in the same plane as the center of the trunnion 32 (or at least its seat 60).

[0068] Figure 7 shows a cross-sectional example of a flexible spherical bearing. This type of bearing can be used, for example, as a central spherical bearing (reference numeral 56 in Figure 4). The flexible spherical bearing includes two coaxially aligned bushings 62a and 62b, with an elastic material 66 disposed between them. The inner bushing 62a has a circumferential surface that is convex, preferably spherical, in at least a portion of its area. The outer bushing 62b has a complementary inner surface that is concave, preferably spherical, in at least a portion of its area. However, in another embodiment, the bushings 62a and 62b may each have a flat circumferential surface or an inner surface. By utilizing this flexible spherical bearing, the radial stiffness required for normal operation can be provided, while the elastic material 66 allows for radial, torsional, axial, and tapered degrees of freedom in predefined directions.

[0069] As an alternative to or supplement to the central spherical bearing, this flexible spherical bearing can also be used to movably mount the trunnion onto an external structure. In particular, such a flexible spherical bearing can, in principle, replace, for example, the spherical bearing formed by a bearing disc and a bearing housing as shown in Figure 3. For example, an elastic material 66 can be provided between the bearing disc and the bearing housing as shown in Figure 3.

[0070] Figure 8 illustrates an example of a system 100, which includes a first component 102 and a second component 104 pivotally mounted on the first component 102. The system 100 also includes a linear unit 10, which is mounted to the first component 102 via two mounting assemblies 30. A nut (not shown) of the linear unit 10 is connected to the second component 104 such that the second component 104 pivots relative to the first component 102 about a joint 106 as the nut moves linearly. The connection between the nut and the second component 104 can be established via a slide (having a connection structure 26, see Figure 1) and a connector 108, one end of which is connected to the connection structure 26 and the other end to the second component 104.

[0071] Through the two mounting components 30, the linear element 10 can be decoupled from the deformation of the first component 102 (e.g., caused by a load applied by the second component 104). Similarly, during the thermal expansion of the linear element 10, one of the mounting components 30 can self-center, thereby not generating a load.

[0072] Explanation of reference numerals in the attached figures 10 Linear Units 12. Shell 12a Frontend 12b backend 14 Screw 16 nuts 18 motors 20 Gearbox 22 Slide 24 guide rails 26 Connection Structure 30 Installation Components 32 trunnions 32a Mounting Base 32b plane 32c through hole 34 Bearing Housing 34a Inner surface portion 36 Bushing 38 bearing disc 38a Spherical section 38b hole 40 end cap 42 holes 44 Grooves 46 cavities 46a Inner surface portion 48 Center bearing disc 48a Spherical section 50 front-end board 52 protrusions 52a side surface 54 Flange 54a Convex toroidal portion 56 Center Spherical Bearing 58 strokes 60 socket 60a inner surface 62a Inner Liner 62b outer bushing 64 holes 66 Elastic Materials 100 System 102 First Component 104 Second Component 106 connector 108 Connector E External Structure L longitudinal axis A. Longitudinal axis X Bearing housing center axis D gap O bias

Claims

1. A linear unit (10) for converting rotational motion into linear motion, comprising: A shell (12); A screw (14) is rotatably mounted inside the housing (12); A nut (16) engages with the screw (14); as well as Two mounting assemblies (30) are used to mount the housing (12) onto the external structure (E), wherein each mounting assembly (30) includes at least two trunnions (32) arranged laterally relative to the screw (14), the trunnions (32) being movably mounted in bearing housings (34) arranged on opposite sides of the screw (14).

2. The linear unit (10) according to claim 1, wherein, The trunnion (32) of at least one of the mounting components (30) is rotatably mounted in its respective bearing housing (34).

3. The linear unit (10) according to claim 1 or 2, wherein, The trunnion (32) of at least one of the mounting components (30) is axially movable relative to its respective bearing housing (34).

4. The linear unit (10) according to any one of the preceding claims, wherein, One of the mounting components (30) is disposed on the end cap (40) of the linear unit (10), the end cap (40) being mounted on the front end plate (50) of the housing (12).

5. The linear unit (10) according to claim 4, wherein, The end cap (40) is pivotally mounted on the front end plate (50) of the housing (12) and / or is axially movable relative to the front end plate (50) of the housing (12).

6. The linear unit (10) according to claim 5, wherein, The end cap (40) includes a cylindrical hole (42) for receiving an axial protrusion (52) of the front end plate (50), the protrusion (52) having a side surface (52a) with an annular flange (54).

7. The linear unit (10) according to claim 5, wherein, The end cap (40) includes a cavity (46) whose inner surface portion (46a) is complementaryly formed with the spherical portion (48a) of the central bearing disk (48), such that the central bearing disk (48) is pivotable within the cavity (46), and the central bearing disk (48) includes a cylindrical hole (42) in which the axial cylindrical protrusion (52) of the front end plate (50) is axially movable.

8. The linear unit (10) according to any one of claims 4 to 7, wherein, At least one of the mounting components (30) has a trunnion (32) having a mounting base (32a) for fixing the trunnion (32) to the external structure (E), and a bearing housing (34) of one of the mounting components (30) is disposed in the end cap (40).

9. The linear unit (10) according to any one of claims 4 to 7, wherein, The trunnion (32) of the mounting assembly (30) extends from the end cap (40) to opposite sides and is pivotally mounted in the bearing housing (34) relative to the central axis (X) of the bearing housing.

10. The linear unit (10) according to claim 9, wherein, The end cap (40) includes an eyelet (64) in which a central spherical bearing (56) is disposed, and the trunnion (32) extends from the central spherical bearing (56) to both sides of the eyelet (64).

11. The linear unit (10) according to claim 10, wherein, The trunnion (32) extends eccentrically from the central spherical bearing (56).

12. The linear unit (10) according to any one of claims 10 or 11, wherein, The central spherical bearing (56) is a deformable spherical bearing, comprising an elastic material (66) surrounding an inner bushing (62a) in which the trunnion (32) is mounted.

13. The linear unit (10) according to any of the preceding claims, wherein, At least one of the mounting components (30) includes a bearing disc (38) rotatably mounted in a bearing housing (34) of the mounting component (30), each of the bearing discs (38) having a socket (60) for receiving a corresponding trunnion (32), and each of the bearing housings (34) having a spherical inner surface portion (34a) complementary to the spherical portion (38a) of the corresponding bearing disc (38), thereby forming a spherical bearing.

14. The linear unit (10) according to any of the preceding claims, wherein, At least one of the mounting components (30)’s trunnion (32) is movable within the bearing housing (34) in a direction perpendicular to the longitudinal axis (A) of the trunnion (32).

15. The linear unit (10) according to claim 14, wherein, At least one of the mounting components (30) includes a bearing disc (38) rotatably mounted in the bearing housing (34), each of the bearing discs (38) having a socket (60) for receiving one of the trunnions (32), the trunnion (32) having two parallel planes (32b) in contact with opposing inner surfaces (60a) of the socket (60), and the socket (60) being elongated such that the trunnion (32) can move within the socket (60).

16. The linear unit (10) according to claim 14, wherein, At least one of the mounting components (30) includes a bearing disc (38) rotatably mounted in the bearing housing (34), each of the bearing discs (38) having a socket (60) for receiving one of the trunnions (32), and the socket (60) being eccentrically disposed on the bearing disc (38).

17. A system (100) comprising a first component (102) and a second component (104) movable relative to the first component (102), wherein, The linear unit (10) according to any of the preceding claims is mounted on the first component (102) by two mounting components (30), and the second component (104) is connected to the nut (16) of the linear unit (10).

Images