Damping system and linear actuator

Abstract

Linear actuator, comprising a push tube (50), a joint head (51) and a damping system (10), which comprises: - a first assembly (20) with a first axial stop surface (20a) and a second axial stop surface (20b), - a resilient spring arrangement (30) which, in an initial position, abuts axially against the first and second stop surfaces (20a, 20b) under a predetermined preload, and - a second assembly (40) which is mounted so as to be axially displaceable relative to the first assembly (20) and is designed to lift the spring arrangement (30) from the first stop surface (20a) or from the second stop surface (20b) during an axial movement relative to the first assembly (20), characterized in that the damping system (10) has a housing (21) which is rigidly connected to the push tube (50) and forms at least part of the first assembly (20), and the joint head (51) forms at least part of the second assembly (40) or is at least rigidly connected to the second assembly (40).

Description

[0001] The present invention relates to a linear actuator.

[0002] Linear actuators, which convert a drive's rotational movement into a translational movement, are often used to move machine elements or system components. Forces acting on a linear actuator can, under certain circumstances, cause load peaks that can damage the linear actuator. Vibrations or impacts, in particular, can permanently damage the linear actuator mechanism and shorten its service life. Therefore, damping systems have been developed that can cushion the acting forces and thus reduce the load on the linear actuator.

[0003] For example, from DE 10 2016 009 037 A1 an overload protection device is known in which a conversion arrangement for converting a rotational movement into a linear movement is displaceably mounted in a housing along the linear movement.

[0004] GB 1 346 990 relates to shock-absorbing devices for use in conjunction with threaded spindles. In such a device, a nut housing is constructed in two parts, with disc springs arranged in a cavity formed between the two parts.

[0005] US 4 727 762 A discloses a linear actuator in which preloaded Belleville compression springs are arranged between spring seats on bearing supports.

[0006] It is an object of the present invention to further improve the cushioning of forces in a linear actuator, in particular to provide a reliable reduction of forces acting on the linear actuator without impairing the control operation of the actuator.

[0007] This object is achieved by a linear actuator according to claim 1.

[0008] Preferred embodiments are the subject of the dependent claims and the following description.

[0009] A damping system for a linear actuator comprises a first assembly with a first axial stop surface and a second axial stop surface. A resilient spring arrangement is provided which, in an initial position, axially abuts the first and second stop surfaces under a predetermined preload, in particular simultaneously. Furthermore, a second assembly is provided which is mounted axially displaceably relative to the first assembly and is configured to lift the spring arrangement from the first stop surface or from the second stop surface during an axial movement relative to the first assembly.

[0010] An assembly within the meaning of the invention preferably comprises at least one component. Preferably, an assembly is formed by multiple components. During normal operation of the actuator, the components are expediently fixed relative to one another, e.g., rigidly connected, and can only be moved relative to one another by the use of a tool (e.g., by screwing them into a thread and / or the like). However, it is also conceivable for an assembly to comprise only a single component.

[0011] Lifting off, in the sense of the invention, is preferably understood as interrupting or removing a contact. In other words, when one component is lifted off another, one component is spaced apart from the other, creating a gap between the components.

[0012] An axial stop surface within the meaning of the invention is preferably a surface with a surface normal aligned parallel to a longitudinal axis and / or direction of movement, against which a component, in particular the spring assembly, can axially abut. Such an axial stop surface can be formed, for example, by a radial step or a radial projection that extends into a spring travel of the spring assembly.

[0013] One aspect of the invention is based on the approach of applying a predetermined preload to a resilient spring arrangement in a damping system for a linear actuator. Preferably, a first assembly is provided for this purpose, having a first stop surface and a second stop surface against which the spring arrangement is supported in a home position, for example, during normal operation of a linear actuator. For this purpose, the spring arrangement can be arranged, for example, such that it is subjected to the preload in the home position and contacts the first and second stop surfaces. A second assembly, mounted axially displaceably relative to the first assembly, is also expediently provided in order to actuate the spring arrangement at least in sections, for example, to compress it.The damping system is advantageously configured in such a way that a movement of the first assembly relative to the second assembly is only possible if the predetermined preload is overcome.

[0014] The specified preload is expediently set such that the spring assembly can only be compressed by the second assembly—and thus lifted off the first or second stop surface—when a nominal force, for example, a permissible maximum force, of the linear actuator is exceeded. The spring assembly can, for example, be compressible by the second assembly such that an axial end of the spring assembly loses contact with the first stop surface or the second stop surface when an external force acts on the first assembly or the second assembly.

[0015] The preloaded spring arrangement prevents unnecessary and potentially damaging oscillation of the damping system. Sensitive components of the linear actuator, such as the support bearing, ball screw, ball nut, and / or similar, can thus be protected from excessive impacts or shocks. At the same time, however, it is also possible to maintain the rigidity of the linear actuator during normal operation, i.e., preferably up to the rated force. This allows, for example, machine elements or system components to be precisely positioned despite the integration of damping in the linear actuator.

[0016] In a preferred embodiment, the damping system, in particular the first assembly and / or the spring arrangement and / or the second assembly, is designed such that the second assembly lifts the spring arrangement from the first stop surface upon axial movement relative to the first assembly in a first direction and from the second stop surface upon axial movement relative to the first assembly in a second direction opposite to the first direction. For example, the first assembly and / or the spring arrangement and / or the second assembly can be arranged relative to one another such that, depending on the direction of movement, the spring arrangement is lifted from either the first or the second stop surface.

[0017] In a further preferred embodiment, the second assembly has a third axial stop surface and a fourth axial stop surface. In the initial position, the spring assembly advantageously abuts axially against the third stop surface and the fourth stop surface under the predetermined preload. The second assembly is preferably designed such that the third or fourth stop surface enables the spring assembly to be lifted off the first or second stop surface, thereby enabling, for example, at least partial compression of the spring assembly. The third and fourth axial stop surfaces enable reliable actuation of the spring assembly.

[0018] In a further preferred embodiment, the first stop surface is radially aligned with the third stop surface, and the second stop surface is radially aligned with the fourth stop surface in the initial position. In particular, the first and third, as well as the second and fourth, stop surfaces can each define a stop plane in the initial position. The spring arrangement can thus be supported on four stop surfaces. As a result, a uniform load can be achieved across all stop surfaces.

[0019] In a further preferred embodiment, the first assembly has a fifth stop surface and a sixth stop surface. The spring arrangement is expediently supported on the fifth and sixth stop surfaces at least with the predetermined preload. The second assembly is preferably designed and / or arranged such that the contact between the spring arrangement and the fifth and sixth stop surfaces cannot be interrupted by a movement of the second assembly. Rather, the second assembly can be designed and / or arranged to compress the spring arrangement at least in sections against the fifth and sixth stop surfaces. The fifth and sixth stop surfaces can thus serve to adjust the predetermined spring force. The provision of a fifth and sixth stop surface also enables a compact design of the damping system.

[0020] In a further preferred embodiment, the spring arrangement is spaced from the first or second stop surface in a loaded position, for example, when a force acts on the first or second assembly. The distance between the spring arrangement, in particular an axial end of the spring arrangement, and the first or second stop surface, adjusted using the second assembly, expediently corresponds to a spring travel of the spring arrangement. The spring arrangement can thus reliably absorb a load acting on the damping system that, for example, exceeds the nominal force of the linear actuator.

[0021] In a further preferred embodiment, the spring arrangement comprises at least one, in particular rigid, support means and at least one elastic spring means. The elastic spring means is expediently supported on the at least one support means at least under the predetermined preload. The at least one support means is preferably designed to abut against the first or second stop surface, in particular arranged accordingly. This allows for reliable axial fixation of the spring means. With a flat surface, the at least one support means can ensure well-defined abutment against the stop surfaces and, consequently, good force transmission without force peaks.

[0022] In a further preferred embodiment, the spring arrangement comprises at least one spring element configured as a disc spring assembly. The spring arrangement may, for example, comprise four disc springs stacked together to form two assemblies. The spring arrangement preferably comprises at least two, preferably four, such assemblies, which in turn may be combined to form one or two disc spring groups. Such disc spring assemblies allow high preloads to be achieved even with a compact spring arrangement design.

[0023] In a further preferred embodiment, the first stop surface and the second stop surface are arranged opposite one another, i.e., facing one another. The spring arrangement is expediently arranged between the first stop surface and the second stop surface. Preferably, the third and fourth stop surfaces are also arranged opposite one another, and the spring arrangement can be arranged between the third and fourth stop surfaces. This allows the spring arrangement to be particularly compact axially. Consequently, the damping system can be used, for example, at the end of a torque tube, in particular between the torque tube and a rod end.

[0024] In a further preferred embodiment, the first stop surface and the second stop surface are oriented facing away from one another. The first and second stop surfaces are expediently arranged, in particular axially, between a first section of the spring arrangement and a second section of the spring arrangement. Preferably, the third and fourth stop surfaces are also oriented facing away from one another and arranged between the first and second sections of the spring arrangement. In other words, the first and second stop surfaces - and optionally also the third and fourth stop surfaces - are (axially) surrounded by the spring arrangement. The first and second sections can each have at least one elastic spring means, for example a disc spring assembly. With this orientation of the first and second stop surfaces, the adjustment of the preload of the spring arrangement can be facilitated, for example by dedicated preloading means.Furthermore, this allows the first and / or second assembly to be constructed axially compactly. As a result, the damping system can be used, for example, in the area of ​​the linear actuator mechanism for converting a rotational movement into a translational movement, particularly on a spindle or ball screw nut.

[0025] In a further preferred embodiment, a preload assembly is provided that is configured to adjust the predetermined preload. For this purpose, the preload assembly can comprise at least one preload element, for example, a safety nut or a grooved nut. This allows for a flexibly adjustable preload. In particular, application-dependent adjustment or readjustment of the preload is possible.

[0026] In a further preferred embodiment, the preload assembly comprises a threaded mechanism, the actuation of which allows the spring assembly to be compressed or decompressed at least in sections. In particular, the at least one preload element can be "screwed in" or "unscrewed." This allows for uncomplicated and quick, yet particularly precise, adjustment of the preload.

[0027] In a further preferred embodiment, the distance between the first stop surface and the second stop surface can be varied, for example, by means of the threaded mechanism. The predetermined preload can thus be adjusted particularly easily.

[0028] In a further preferred embodiment, the second assembly and the spring arrangement are arranged radially within the first assembly. In other words, the first assembly can radially enclose the second assembly and the spring arrangement. This allows a particularly protected arrangement of the spring arrangement and the second assembly to be achieved.

[0029] A linear actuator according to a first aspect of the invention comprises a damping system as described above. The damping system is expediently integrated into a power train of the linear actuator. In other words, the damping system is expediently integrated into the linear actuator in such a way that a force flow occurring during operation passes through the damping system. This prevents the linear actuator from oscillating and protects the linear actuator's mechanism for converting a rotational movement into a translational movement from strong impacts or shocks. At the same time, the linear actuator offers high rigidity, enabling precise positioning even of heavy loads by the actuator.

[0030] In a preferred embodiment, the predetermined preload is less than or equal to a nominal force of the linear actuator. A nominal force is preferably understood to be the maximum force for which the linear actuator is designed. This prevents the creation of spring deflection in the force train of the linear actuator until the nominal force is reached. In other words, a high rigidity of the linear actuator can be ensured up to the nominal force.

[0031] In one possible embodiment, the linear actuator comprises a ball screw, a ball nut operatively connected to the ball screw, and a safety nut coupled to the ball nut, in particular via the spring arrangement. The spring arrangement is expediently arranged at least partially between the ball nut and the safety nut. This ensures that the safety nut only engages the ball screw when a force greater than the specified preload is applied.

[0032] In a further embodiment, the linear actuator comprises a ball screw, a ball nut operatively connected to the ball screw, and a nut housing in which the ball nut is arranged for axial displacement. The nut housing expediently forms at least part of the first assembly. The ball nut expediently forms at least part of the second assembly. The ball nut, in particular the ball rollers mediating the operative connection between the ball screw and the ball nut, can thereby be effectively protected from overload.

[0033] According to the invention, the linear actuator comprises a push tube and a rod end. The damping system has a housing rigidly connected to the push tube, which forms at least part of the first assembly. The rod end forms at least part of the second assembly or is at least rigidly connected to the second assembly. An overload acting on the rod end can be at least partially absorbed by the spring arrangement before it acts on the mechanism of the linear actuator via the push tube.

[0034] The invention is explained in more detail below with reference to figures. Where appropriate, elements with the same function are provided with the same reference numerals. The invention is not limited to the exemplary embodiments illustrated in the figures - not even with regard to functional features. The previous description as well as the following description of the figures contain numerous features, some of which are summarized in the dependent claims. However, a person skilled in the art will also consider these features, as well as all other features disclosed above and in the following description of the figures, individually and combine them to form further useful combinations. In particular, all of the features mentioned can be combined individually and in any suitable combination with the linear actuator according to the first aspect of the invention.

[0035] They show: Fig. 1 shows an example of a damping system for a linear actuator, comprising a first assembly with two mutually facing stop surfaces for a spring arrangement, in an initial position; Fig. 2 an example of the damping system from Fig. 1 in a first loading position; Fig. 3 an example of the damping system from Fig. 1 in a second loading position; Fig. 4 shows an example of a damping system for a linear actuator, which has a first assembly with two mutually facing stop surfaces for a spring arrangement, in an initial position; Fig. 5 shows an example of a damping system for a linear actuator having a second assembly rigidly connected to a spring assembly; Fig. 6 shows an example of a damping system for a linear actuator, comprising a first assembly including a safety nut of the linear actuator; Fig. 7 an example of the damping system from Fig. 6 in a first loading position; and Fig. 8 an example of the damping system from Fig. 6 in a second loading position.

[0036] Fig. 1 shows an example of a damping system 10 for a linear actuator, comprising a first assembly 20 with two mutually facing stop surfaces 20a, 20b for a preloaded, resilient spring arrangement 30, in an initial position. The damping system 10 further comprises a second assembly 40, which is mounted axially displaceably relative to the first assembly 20 and is configured to lift the spring arrangement 30 from the first stop surface 20a or the second stop surface 20b during an axial movement relative to the first assembly 20. For this purpose, the second assembly 40 has two mutually facing stop surfaces 40a, 40b.

[0037] In the example shown, the first assembly 20 is rigidly connected to a push tube 50 of the linear actuator, for example, screwed onto it. The second assembly 40 is rigidly connected to a rod end 51 of the linear actuator. This allows a force flow from the rod end 51 to the push tube 50 or vice versa via the spring assembly 30, and sensitive components of the linear actuator, such as the support bearing, ball screw, and / or ball nut, to be protected from force peaks.

[0038] To enable precise positioning of the rod end 51 through a linear movement of the push tube 50 despite the damping system 10, the spring assembly 30 is expediently subjected to a predetermined preload, which advantageously essentially corresponds to a nominal force of the linear actuator. Further compression of the spring assembly 30 between the first stop surface 20a and the fourth stop surface 40b when tension is applied to the rod end 51, or between the second stop surface 20b and the third stop surface 40a when pressure is applied to the rod end 51, can therefore only occur if the applied force is greater than the nominal force—and thus potentially damaging to the components of the linear actuator.

[0039] For example, the spring arrangement 30 can have at least one elastic spring means 31 and two support means 32, via which the spring means 31 can be supported on the first, second, third and / or fourth stop surface 20a, 20b, 40a, 40b. The spring means 31 expediently has at least one, in the example shown four, disc spring assemblies 33 each consisting of two layered disc springs, whereby for reasons of clarity, only one of the disc spring assemblies 33 is provided with a reference numeral. Using such disc spring assemblies 33, spring forces in the range of, for example, 70 kN to 90 kN can be realized with a spring travel of 8 mm. If the spring means 31 is clamped between the first and second stop surfaces 20a, 20b under a preload of, for example, 50 kN, force impacts between 50 kN and 70 to 90 kN can be cushioned by a relative movement of up to 3 mm between the first and second assemblies 20, 40.

[0040] In the example shown, the preload can be adjusted by varying the distance between the first and second stop surfaces 20a, 20b. For this purpose, the first assembly 20 can comprise a length-adjustable housing 21 which has a housing sleeve 22 with an internal thread and a preload element 23 with an external thread. The preload element 23 is expediently designed as a locking nut which at least partially closes the housing sleeve 22 at one axial end, i.e. on one side. The housing sleeve 22 has the first stop surface 20a and the preload element 23 has the second stop surface 20b. The first stop surface 20a can be formed, for example, by an axial side surface of a radially inner projection or collar of the housing sleeve 22. The second stop surface 20b is expediently formed by an axial end face of the preload element 23.The internal thread of the housing sleeve 22 and the external thread of the preloading element 23 can interact with each other and thereby form a threaded mechanism of a preloading arrangement 11.

[0041] The damping system 10 is advantageously connected to the push tube 50 via the preloading element 23, in particular the locking nut, for example screwed onto the push tube 50.

[0042] In order to adapt the second assembly 40 to a change in the preload—and any associated compression or relaxation of the spring means 31—the second assembly 40 comprises a cantilevered bolt 41 and a securing means 42, for example in the form of a grooved nut, that can be variably positioned on the bolt 41 in the axial direction. While an axial side surface of the bolt collar can form the third stop surface 40a, an axial end surface of the securing means 42 expediently forms the fourth stop surface 40b. The distance between the third and fourth stop surfaces 40a, 40b can thus be adjusted analogously to the preload arrangement 11 on the first assembly 20. In particular, the distance between the third and fourth stop surfaces 40a, 40b can be adjusted such that, in the starting position shown, the first and third stop surfaces 20a, 40a and the second and fourth stop surfaces 20b, 40b are each aligned with one another.This makes it possible to avoid axial play of the second assembly 40 and / or the spring arrangement 30 in the initial position.

[0043] Fig. 2 shows an example of the damping system 10 from Fig. 1 in a first load position, in which a compressive force exceeding the predetermined preload acts on the joint head 51 (only partially shown). The third stop surface 40a of the second assembly 40 lifts the spring arrangement 30 from the first stop surface 20a of the first assembly 20. This allows a flow of force from the joint head 51 via the third stop surface 40a through the spring arrangement 30 and further via the second stop surface 20b to the first assembly 20 and thus to the torque tube 50. Due to the deflection of the second assembly 40 relative to the first assembly 20, the fourth stop surface 40b also lifts off the spring arrangement 30. A gap is created between the first stop surface 20a and the spring arrangement 30 and between the fourth stop surface 40b and the spring arrangement 30, the size of which expediently corresponds to the spring travel of the spring arrangement 30.

[0044] Fig. 3 shows an example of the damping system 10 from Fig. 1 in a second load position, in which a tensile force exceeding the specified preload acts on the joint head 51 (only partially shown). The fourth stop surface 40b of the second assembly 40 lifts the spring arrangement 30 from the second stop surface 20b of the first assembly 20. This allows a flow of force from the push tube 50 via the first stop surface 20a through the spring arrangement 30 and further via the fourth stop surface 40b to the second assembly 40 and thus to the joint head 51. Due to the deflection of the second assembly 40 relative to the first assembly 20, the third stop surface 40a also lifts off the spring arrangement 30. A gap is created between the second stop surface 20b and the spring arrangement 30 and between the third stop surface 40a and the spring arrangement 30, the size of which expediently corresponds to the spring travel of the spring arrangement 30.

[0045] Fig. 4 shows an example of a damping system 10 for a linear actuator, comprising a first assembly 20 with two mutually opposite stop surfaces 20a, 20b for a spring arrangement 30, in an initial position. The damping system 10 further comprises a second assembly 40, which is mounted axially displaceably relative to the first assembly 20 and is configured to lift the spring arrangement 30 from the first stop surface 20a or the second stop surface 20b during an axial movement relative to the first assembly 20. For this purpose, the second assembly 40 has two mutually opposite stop surfaces 40a, 40b.

[0046] In the example shown, the first assembly 20 comprises a rotor 52, which is part of a drive of the linear actuator, and a nut housing 53 rigidly connected thereto, for example by screwing. The nut housing 53 is rotatably mounted in a housing of the linear actuator (not shown) via bearings 54 and is simultaneously axially fixed.

[0047] The second assembly 40 is formed at least partially by a ball-and-socket nut 56, which is arranged axially displaceably on the rotor 52 within the nut housing 53. The ball-and-socket nut 56 is operatively connected to a ball-and-socket spindle 57 of the linear actuator via ball rollers. This allows a force flow from the ball-and-socket spindle 57 to the nut housing 53—and via the bearings 54 to the housing of the linear actuator—or vice versa via the spring assembly 30, thus protecting sensitive components of the linear actuator, such as the bearings 54, the ball-and-socket spindle 57, and / or the ball-and-socket nut 56, from force peaks.

[0048] In the example shown, the spring arrangement 30 has two elastic spring means 31a, 31b each consisting of three disc spring assemblies 33, wherein each disc spring assemblies 33 comprises two layered disc springs. For reasons of clarity, only one of the disc spring assemblies 33 is provided with a reference number. A first spring means 31a can be supported axially with an end facing away from the first and third stop surfaces 20a, 40a on a fifth stop surface 20c of the first assembly 20. A second spring means 31b is expediently supported axially with an end facing away from the second and fourth stop surfaces 20b, 40b on a sixth stop surface 20d of the first assembly 20. The two spring means 31a, 31b are supported on the fifth and fourth stop surfaces 20a, 40a.sixth stop surface 20c, 20d not only in the starting position shown, but preferably also in a load position in which the second assembly 40 is deflected relative to the first assembly 20 and the first or second spring means 31a, 31b is compressed even more.

[0049] Fig. Figure 5 shows an example of a damping system 10 for a linear actuator, which includes a second assembly 40 rigidly connected to a spring assembly 30. The damping system 10 also includes a first assembly 20 with two stop surfaces 20a, 20b, relative to which the second assembly 40 is mounted for axial displacement. The second assembly 40 is formed at least partially by a push tube 50 of the linear actuator.

[0050] In the example shown, the first assembly 20 comprises a nut housing 53 for a ball-roller nut 56 of the linear actuator, which is operatively connected to a ball-roller spindle 57 via ball rollers. The nut housing 53 is radially projecting at one end. An axial side surface of the collar forms the first stop surface 20a.

[0051] The first assembly 20 preferably also comprises a preload element 23, in the present example in the form of a grooved nut, which is screwed into the nut housing 53 via an internal thread of the nut housing 53. The grooved nut can serve as a locking nut, which at least partially closes the nut housing 53 axially on one side. An axial side surface of the preload element 23 forms the second stop surface 20b. The nut housing 53, together with the preload element 23, forms a preload arrangement 11 with a threaded mechanism for adjusting a predetermined preload of the spring arrangement 30.

[0052] In addition to an elastic spring means 31 in the form of three disc spring assemblies 33 each comprising two disc springs, the spring arrangement 30 also includes a support means 32 against which the spring means 31 can be supported under the predetermined preload. The support means 32 is designed here as a safety nut 58, which can interact with the ball screw 57 in the event of an impairment of the interaction between the ball screw spindle 57 and the ball screw nut 56, for example, if the ball screws are destroyed, and thus prevent an uncontrolled axial movement of the ball screw spindle 57 relative to the ball screw nut 56 or the nut housing 53.

[0053] If a pressure load acts on the push tube 50 which is higher than the nominal force of the linear actuator, there is a risk of damage, for example, to the ball rollers or to bearings not shown in the nut housing 53 (see Fig. 4). Therefore, the preload is preferably set substantially equal to the nominal force. If the pressure applied to the push tube 50 exceeds the specified preload, the spring assembly 30 can now compress, causing the safety nut 58 to operatively engage the ball screw 57. Overloading, particularly of the ball screws, can thus be avoided.

[0054] Fig. 6 shows an example of a damping system 10 for a linear actuator, comprising a first assembly 20 comprising a safety nut 58 of the linear actuator and having four stop surfaces 20a, 20b, 20c, 20d. The damping system 10 also includes a spring arrangement 30 with two spring means 31a, 31b and a second assembly 40 with two stop surfaces 40a, 40b. In the present example, the damping system 10 is in an initial position in which the spring arrangement 30 abuts the first and third aligned stop surfaces 20a, 40a and the second and fourth aligned stop surfaces 20b, 40b.

[0055] In addition to the safety nut 58, the first assembly 20 has a nut housing 53 and a preloading element 23, wherein the safety nut 58 and the preloading element 23 are screwed into the nut housing 53 at opposite ends thereof. An axial side surface of the preloading element 23 forms the fifth stop surface 20c, and an axial end surface of the safety nut 58 forms the sixth stop surface 20d. The spring arrangement 30 is arranged in sections between the fifth and first stop surfaces 20c, 20a and between the second and sixth stop surfaces 20b, 20d of the first assembly 20.

[0056] The safety nut 58 and the nut housing 53, as well as the preloading element 23 and the nut housing 53, each form a preload assembly 11, with which the spring assembly 30 can be subjected to a predetermined preload. By screwing the preloading element 23 into the nut housing 53, the preload of a first section 34a of the spring assembly 30, which comprises the first spring means 31a, can be increased or, by unscrewing it, reduced. Similarly, by screwing the safety nut 58 into the nut housing 53, the preload of a second section 34b of the spring assembly 30, which comprises the second spring means 31b, can be increased or, by unscrewing it, reduced.

[0057] The second assembly 40 has a ball-and-socket nut 56 mounted axially displaceably in the nut housing 53, which is operatively connected to a ball-and-socket spindle 57 of the linear actuator via ball rollers. Axial end or front surfaces of the ball-and-socket nut 56 form the third and fourth stop surfaces 40a, 40b. As a result, during operation of the linear actuator, in which the rotational movement of the ball-and-socket spindle 57 is converted into a translational movement of the ball-and-socket nut 56, a force corresponding to the movement, which does not exceed the predetermined preload, can be transmitted via the spring arrangement 30 to the first assembly 20 and further, for example, to a component rigidly connected to the first assembly 20, such as a push tube 50 screwed into the safety nut 58. This allows, for example, a machine element coupled to the push tube 50 to be precisely positioned.

[0058] The preload of the spring assembly 30 is preferably set substantially equal to or higher than a nominal force of the linear actuator. If a tensile or compressive load on the push tube 50 exceeds the specified preload, for example, due to a load peak such as an impact, the spring assembly 30 can compress in one of the sections 34a, 34b, thus operatively connecting the safety nut 58 with the ball screw 57. These cases are described in the Fig. 7 and Fig. 8 shown.

[0059] Fig. 7 shows an example of the damping system 10 from Fig. 6 in a first load position, in which a tensile force exceeding the predetermined preload of the spring assembly 30 acts on the push tube 50. The tensile force acts via the fifth stop surface 20c of the first assembly 20 onto the first section 34a of the spring assembly 30, which in this section 34a is supported on the third stop surface 40a of the second assembly 40 and is compressed accordingly. Thus, the second assembly 40 lifts the first section 34a of the spring assembly 30 from the first stop surface 20a.

[0060] The compression of the spring arrangement 30 in the first section 34a results in an axial deflection of the first assembly 20 relative to the second assembly 40. This allows the safety nut 58 to come into operative connection with the ball screw 57 and prevent an increase in the load on the operative connection between the ball screw nut 56 and the ball screw 57, in particular on the ball rollers, far beyond the specified preload.

[0061] Fig. 8 shows an example of the damping system 10 from Fig.6 in a second load position, in which a compressive force exceeding the predetermined preload of the spring assembly 30 acts on the push tube 50. The compressive force acts via the sixth stop surface 20d of the first assembly 20 onto the second section 34b of the spring assembly 30, which in this section 34b is supported on the fourth stop surface 40b of the second assembly 40 and is compressed accordingly. Thus, the second assembly 40 lifts the second section 34b of the spring assembly 30 from the second stop surface 20b.

[0062] The compression of the spring arrangement 30 in the second section 34b results in an axial deflection of the first assembly 20 relative to the second assembly 40. This allows the safety nut 58 to come into operative connection with the ball screw 57 and prevent an increase in the load on the operative connection between the ball screw nut 56 and the ball screw 57, in particular on the ball rollers, far beyond the specified preload. List of reference symbols 10 Damping system 11 Preload arrangement 20 first assembly 20a first stop surface 20b second stop surface 20c fifth stop surface 20d sixth stop surface 21 housings 22 Housing sleeve 23 Preload element 30 spring arrangement 31 spring means 31a first spring means 31b second spring means 32 proppant 33 disc spring package 34a first section 34b second section 40 second assembly 40a third stop surface 40b fourth stop surface 41 bolts 42 securing devices 50 thrust tube 51 Rod end 52 Rotor 53 Nut housing 54 warehouses 56 Ball transfer nut 57 Ball screw 58 Safety nut

Claims

[1] Linear actuator comprising a thrust tube (50), a joint head (51) and a damping system (10), which comprises: - a first assembly (20) with a first axial stop surface (20a) and a second axial stop surface (20b), - a resilient spring arrangement (30) which, in an initial position, abuts axially against the first and second stop surfaces (20a, 20b) under a predetermined preload, and - a second assembly (40) which is mounted axially displaceably relative to the first assembly (20) and is adapted to lift the spring arrangement (30) from the first stop surface (20a) or from the second stop surface (20b) during an axial movement relative to the first assembly (20), characterized bythat the damping system (10) has a housing (21) which is rigidly connected to the torque tube (50) and forms at least part of the first assembly (20), and the joint head (51) forms at least part of the second assembly (40) or is at least rigidly connected to the second assembly (40). [2] Linear actuator according to claim 1 characterized by that the second assembly (40) has a third axial stop surface (40a) and a fourth axial stop surface (40b), wherein the spring arrangement (30) in the initial position abuts axially against the third stop surface (40a) and the fourth stop surface (40b) under the predetermined preload. [3] Linear actuator according to claim 2 characterized by that in the initial position the first stop surface (20a) is radially aligned with the third stop surface (40a) and the second stop surface (20b) is radially aligned with the fourth stop surface (40b). [4] Linear actuator according to one of the preceding claims, characterized by that the first assembly (20) has a fifth stop surface (20c) and a sixth stop surface (20d) on which the spring arrangement (30) is supported at least with the predetermined preload. [5] Linear actuator according to one of the preceding claims, characterized by that the spring arrangement (30) is spaced from the first or second stop surface (20a, 20b) in a loading position. [6] Linear actuator according to one of the preceding claims, characterized by that the spring arrangement (30) has at least one support means (32) and at least one elastic spring means (31; 31a, 31b), which is supported on the at least one support means (32) at least under the predetermined prestress, wherein the at least one support means (32) is designed to strike the first or second stop surface (20a, 20b). [7] Linear actuator according to one of the preceding claims, characterized bythat the spring arrangement (30) has at least one spring means (31; 31a, 31b) designed as a disc spring assembly (33). [8] Linear actuator according to one of the preceding claims, characterized by that the first stop surface (20a) and the second stop surface (20b) are arranged opposite one another and the spring arrangement (30) is arranged between the first stop surface (20a) and the second stop surface (20b). [9] Linear actuator according to one of claims 1 to 7, characterized by that the first stop surface (20a) and the second stop surface (20b) are oriented away from each other and are arranged between a first section (34a) of the spring arrangement (30) and a second section (34b) of the spring arrangement (30). [10] Linear actuator according to one of the preceding claims, characterized by a preload arrangement (11) arranged to set the predetermined preload. [11] Linear actuator according to one of the preceding claims, characterized by that the pretensioning arrangement (11) has a threaded mechanism, by the actuation of which the spring arrangement (30) can be compressed or decompressed at least in sections. [12] Linear actuator according to one of the preceding claims, characterized by that a distance between the first stop surface (20a) and the second stop surface (20b) is variable. [13] Linear actuator according to one of the preceding claims, characterized by that the second assembly (40) and the spring arrangement (30) are arranged radially inside the first assembly (20). [14] Linear actuator according to one of the preceding claims, characterized by that the specified preload is less than or equal to a nominal force of the linear actuator.

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