Linear actuator and telescopic column with double threaded spindle

Abstract

A linear actuator (1) for a height-adjustable column, comprising a threaded spindle (2) having a longitudinal extension along a longitudinal axis, the spindle being adapted to be rotated by a drive shaft (3), characterized in that the spindle is provided with a right-hand thread (21) in a first portion of the longitudinal extension and with a left-hand thread (22) in a second portion of the longitudinal extension. The linear actuator further comprises a right-hand threaded nut member (4) and a left-hand threaded nut member (5). At least one of the nut members (21, 22) comprises a first portion (41, 51) and a second portion (42, 52) configured to be in threaded connection with the spindle (2) on opposite sides of the spindle (2). The threaded connection of the right-hand threaded nut member (4) and the left-hand threaded nut member (5) with the spindle (2) provides opposite linear movement of the right-hand threaded nut member (4) relative to the left-hand threaded nut member (5) along the longitudinal axis.

Description

Technical Field

[0001] The present disclosure relates to a linear actuator for a height adjustable column and a telescoping column. Background Art

[0002] Linear actuators are used together with telescopic tubes in applications like height-adjustable furniture. In order to achieve the desired degree of height adjustment, for example, two or three telescopic tubes can be used, which are driven by a drive arrangement with an externally threaded spindle, an internally and externally threaded spindle and a nut member. However, with such solutions, problems may arise in terms of stability, cost-efficiency and length travel limitations. There are arrangements with fewer components, but these arrangements may also have stability problems.

[0003] Therefore, there is a need for a linear actuator having improved stability and cost efficiency while providing a desired stroke length. Summary of the invention

[0004] The object of the present invention is to provide a linear actuator for a height adjustable column which alleviates the mentioned disadvantages of existing devices. This is achieved by a linear actuator according to the attached independent claim. Embodiments of the invention are presented in the dependent claims and in the following description and drawings.

[0005] According to one aspect of the invention, there is provided a linear actuator for a height adjustable column, the linear actuator comprising a threaded spindle having a longitudinal extension along a longitudinal axis, the spindle being adapted to be rotated by a drive shaft. The spindle is provided with a right-hand thread at a first portion of the longitudinal extension and a left-hand thread at a second portion of the longitudinal extension.

[0006] The linear actuator further includes a right-hand threaded nut member threadedly connected to the right-hand thread of the spindle, and a left-hand threaded nut member threadedly connected to the left-hand thread of the spindle. At least one of the right-hand threaded nut member and the left-hand threaded nut member includes a first portion and a second portion configured to be threadedly connected to the spindle on opposite sides of the spindle.

[0007] The threaded connections of the right-handed nut member and the left-handed threaded nut member with the spindle may provide opposite linear movement of the right-handed threaded nut member relative to the left-handed threaded nut member along the longitudinal axis when the spindle rotates.

[0008] The right-handed thread and the left-handed thread of the main shaft can be threadedly connected with the right-handed thread nut member and the left-handed thread nut member respectively, so that they can be driven in opposite longitudinal directions relative to each other by the rotation of the main shaft. The right-handed thread nut member and the left-handed thread nut member can each be connected to the telescopic tube. By the rotation of the main shaft, linear movement of the two telescopic tubes in opposite longitudinal directions can be provided. The two nut members move relative to the main shaft between two end positions along the longitudinal axis by the rotation of the main shaft. One of the end positions can correspond to the maximum extension state of the linear actuator, and the other end position corresponds to the maximum contraction state of the linear actuator.

[0009] At least one of the left-handed threaded nut member and the right-handed threaded nut member having two parts on opposite sides of the main shaft can contribute to the high stability of the arrangement, and the low risk of the nut member bending to the extent that the operation of the linear actuator is disturbed or damaged. The opposite side of the main shaft can refer to the opposite radial side along the circumference of the main shaft. The first part and the second part of the nut member are located on opposite sides, meaning that at least a part of one part of the nut member should be displaced 180 degrees relative to at least a part of the other part of the two parts of the nut member along the circumference of the main shaft. In some embodiments, substantially the entire first part of the nut member is arranged to be opposite to the entire second part of the nut member. Such a symmetrical nut member can provide great stability for the linear actuator.

[0010] Since the nut members do not need to contact the same portion of the spindle, the linear actuator can provide a large stroke length. Relative to many prior art linear actuators, the linear actuator of the present invention can be simple and have few components, while still being able to support a telescoping column with three telescoping tubes. The simplicity and low number of components can contribute to the cost efficiency of the linear actuator. Further still, since at least one of the nut members has two portions on opposite sides of the spindle, the linear actuator can have a high level of stability in the extended state.

[0011] In one embodiment, the right-hand threaded nut member may include a first portion and a second portion configured to be threadedly connected to the spindle on opposite sides along the circumference of the spindle, and the left-hand threaded nut member may include a first portion and a second portion configured to be threadedly connected to the spindle on opposite sides along the circumference of the spindle.

[0012] Having the two nut members comprise a first portion and a second portion on opposite radial sides of the main shaft may further contribute to the stability of the arrangement. Thereby, the risk of the two nut members deflecting from the longitudinal direction and bending may be reduced. Such an embodiment, in which the two nut members are arranged symmetrically around the main shaft, may provide yet further increased stability of the linear actuator.

[0013] In one embodiment, the right-hand threaded nut member and the left-hand threaded nut member may extend along the same portion of the longitudinal extension of the spindle. This may be the case at least in a retracted state of the linear actuator. The retracted state may be a maximum retracted state of the linear actuator. This may further be the case in an intermediate state of the linear actuator (an intermediate state between the maximum retracted state and the maximum extended state).

[0014] In one embodiment, the first part of the right-hand threaded nut member and the first part of the left-hand threaded nut member can be displaced 85 to 95 degrees, preferably 90 degrees along the circumference of the main shaft. In addition, the second part of the right-hand threaded nut member and the second part of the left-hand threaded nut member can be displaced 85 to 95 degrees, preferably 90 degrees along the circumference of the main shaft.

[0015] The displacement between the first portion of the right-hand threaded nut member and the first portion of the left-hand threaded nut member can contribute to the stability of the linear actuator, because the right-hand threaded nut member and the left-hand threaded nut member can provide stability in two different, substantially perpendicular directions. Since the nut member can have these portions on two opposite radial sides of the spindle, the risk of bending the nut member can be lower.

[0016] In one embodiment, the right-hand and left-hand threads of the spindle may be separated along the longitudinal extension of the spindle.

[0017] In one embodiment, the right-hand thread and the left-hand thread may be provided at opposite ends of the longitudinal extension of the spindle.

[0018] The separation between the first and second parts of the spindle (respectively provided with right-hand and left-hand threads) can imply that the left-hand thread is in threaded contact with the left-hand threaded nut member, but not in contact with the threaded portion of the right-hand threaded nut member, and vice versa. Interference with the operation of the linear actuator due to undesired contact with the opposite threaded portion can thereby be avoided.

[0019] In some embodiments, the left-hand and right-hand threads of the spindle may be separated by a non-threaded portion.

[0020] In one embodiment, the non-threaded portion may extend along at least 50% of the longitudinal extension of the main shaft. In one embodiment, the non-threaded portion may extend along at least 70%, or at least 80% of the longitudinal extension of the main shaft.

[0021] In one embodiment, the right-hand thread and the left-hand thread may be provided at opposite ends of the longitudinal extension of the spindle.

[0022] The right-hand and left-hand threads being located at opposite ends of the spindle can contribute to a large stroke length of the linear actuator because the right-hand and left-hand threads are in threaded contact with different nut members. The displacement between the nut members can thus be greater than if the threaded portion of the spindle were closer to the middle of the spindle.

[0023] In one embodiment, the right-hand threaded nut member may support first and second portions of the circumference of the spindle, and the left-hand threaded nut member may support third and fourth portions of the circumference of the spindle.

[0024] Right-handed and left-handed threaded nut members supporting different portions of the circumference of the spindle can further contribute to the stability of the linear actuator, as these portions of the nut member can provide stability along different portions of the circumference. These nut members can support most of the circumference of the spindle equally or differently.

[0025] In one embodiment, the right-hand threaded nut member and the left-hand threaded nut member may bear together against substantially the entire circumference of the spindle.

[0026] Having these parts of the nut members supporting substantially the entire circumference may be more stable than supporting only a portion of the circumference and reduces the risk of the spindle becoming unthreaded from any of the nut members.

[0027] In some embodiments, portions of the nut member may be distributed symmetrically along the circumference of the main shaft.

[0028] In one embodiment, the spindle can be hollow and include a longitudinal hole extending through the spindle, and the linear actuator can further include a drive shaft configured to rotate the spindle, wherein the size and shape of the longitudinal hole and the drive shaft can be designed such that rotation of the drive shaft provides rotation of the spindle while the drive shaft is able to move axially relative to the spindle along the longitudinal extension of the spindle.

[0029] The drive shaft can thus be used to rotate the spindle and thereby drive the linear actuator between its retracted and extended states. The drive shaft is shaped to hold the drive shaft rotationally fixed relative to the spindle by engaging with the bore of the spindle, while the drive shaft is axially movable along the longitudinal extension of the spindle.

[0030] In one embodiment, the first portion and the second portion of the right-handed threaded nut member can be configured to be attached to each other at one end, and the first portion and the second portion can include opening portions, which are configured to form an opening for the drive shaft together, and the first portion and the second portion of the left-handed threaded nut member can be configured to be attached to each other at one end, and wherein the first portion and the second portion can include opening portions, which are configured to form an opening for the drive shaft together.

[0031] The attachment between the first and second parts of the left-handed threaded nut member and the right-handed threaded nut member, respectively, can keep these parts aligned relative to each other and prevent operational damage that may be caused if these parts are allowed to move relative to each other. The opening formed by the opening portion of the nut member part can allow the drive shaft to extend through the opening. The end of each nut member forming the opening can be the end away from the main shaft when the linear actuator is in an extended state.

[0032] In one embodiment, the first and second portions of the right-handed threaded nut member may have non-threaded portions that are at least as long as the left-handed threaded portion of the spindle. Further, in one embodiment, the first and second portions of the left-handed threaded nut member may also have non-threaded portions at one end of the left-handed threaded nut member along its longitudinal extension, which are at least as long as the right-handed threaded portion of the spindle. The non-threaded portions of the first and second portions of one or both of the right-handed threaded nut member and the left-handed threaded nut member may extend along less than 30%, less than 20%, or less than 10% of the longitudinal extension of the corresponding nut member.

[0033] In one embodiment, the linear actuator may further include a retaining device, wherein an internal shape of the retaining device may match an external shape of the right-handed threaded nut member and the left-handed threaded nut member, and wherein the retaining device may be arranged to retain the right-handed threaded nut member and the left-handed threaded nut member.

[0034] The retaining device may be designed to align the nut member so that the nut member moves linearly along the longitudinal extension of the main shaft. The retaining device may further press the nut member toward the main shaft and keep the nut member threadedly connected to the main shaft throughout the movement between the extended state and the retracted state. If the nut member moves with a slight directional offset, these nut members can be aligned to the appropriate direction by contacting the retaining device. The retaining device may further protect the main shaft and the nut member from external forces that may damage the linear actuator and its operation.

[0035] The retaining device may axially surround the nut member. In the maximum contracted state of the spindle surround, the nut member may be fully extended within the retaining device, while the nut member may partially extend longitudinally outside the retaining device to obtain a greater extended state of the linear actuator.

[0036] According to a second aspect of the present invention, a telescopic column is provided, which comprises three telescopic tubes, the telescopic column comprising a linear actuator according to any of the embodiments described above, an inner tube attached to a left-handed threaded nut member, an intermediate tube attached to a retaining device, and an outer tube attached to a right-handed nut member.

[0037] Telescopic columns can provide height adjustment for furniture (e.g., tables). The telescopic column of the present invention can provide a more cost-effective and stable solution than prior art solutions. The telescopic column can further provide the above-mentioned advantages of the linear actuator it includes. The inner tube and the outer tube can be driven by the movement of the corresponding nut members by attaching to the left-handed threaded nut member and the right-handed threaded nut member. Thus, the inner tube and the outer tube are driven by the movement of the same main shaft and the drive shaft. Two nut members including parts on opposite sides can enable the tube to be attached to the nut member parts on two opposite sides of the main shaft. Each of the outer tube and the inner tube is attached to the nut member parts on two opposite sides of the main shaft can contribute to a stable arrangement, wherein the risk of tube bending is lower than the prior art solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A perspective view of a linear actuator in an extended state is shown according to one embodiment of the present invention.

[0039] Figure 2 A cross-sectional view of a linear actuator in an extended state is shown according to one embodiment of the present invention.

[0040] Figure 3 A cross-sectional view of a linear actuator in an extended state is shown according to one embodiment of the present invention.

[0041] Figure 4 A perspective view of a linear actuator in a retracted state is shown according to one embodiment of the present invention.

[0042] Figure 5 A cross-sectional view of a linear actuator in a retracted state is shown according to one embodiment of the present invention.

[0043] Figure 6 A cross-sectional view of a linear actuator in a retracted state is shown according to one embodiment of the present invention.

[0044] Figure 7 A folded view of a linear actuator according to one embodiment of the present invention is shown.

[0045] Figure 8 A folded view of a linear actuator according to one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0046] The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. However, the present invention may be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be comprehensive and complete and will fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the same reference numerals refer to the same elements.

[0047] exist Figure 1 , Figure 2 and Figure 3 In FIG. 1 , the linear actuator 1 is shown in its maximum extended state. Figure 1 A perspective view is shown. Figure 2 and Figure 3 Two different views of two mutually perpendicular sections along the extension of the linear actuator 1 are shown. The linear actuator 1 is movable between the extended state and the retracted state. During the extension of the linear actuator 1, the right-handed threaded nut member 4 and the left-handed threaded nut member 5 are moved in opposite directions D1 and D2, respectively, by the rotation of the main shaft 2 (further explained below). The main shaft 2 is driven by the rotation of the drive shaft 3. The circumference of the main shaft 2 is surrounded by a retaining device 6. At one end of the linear actuator there is a plate, which can be used to attach a drive unit for driving the drive shaft 3. The drive shaft 3 can extend through the plate 7.

[0048] exist Figure 4 , Figure 5 and Figure 6 In FIG, the linear actuator 1 is shown in its maximum retracted state. Figure 4 A stereogram is shown in FIG. Figure 5 and Figure 6 Shown with Figure 2 and Figure 3 In the maximum retracted state, the right-handed threaded nut member 4 and the left-handed threaded nut member 5 extend at least largely along the same portion of the longitudinal extension of the linear actuator 1 and extend within the retaining device 6. For some intermediate states between the retracted state and the extended state, the left-handed threaded nut member 5 and the right-handed threaded nut member 4 extend partially within the clamping device and partially along the same portion of the extension of the linear actuator 1.

[0049] Several parts of the linear actuator 1 are Figure 7 and Figure 82 is shown in more detailed views at two different parts of its longitudinal extension. The spindle 2 is hollow and provided with an opening extending through the longitudinal extension of the spindle. The spindle 2 is driven by the rotation of the drive shaft 3. The drive shaft 3 is inserted into the opening. The drive shaft 3 can move axially relative to the spindle 2 along its longitudinal extension, but is rotationally fixed relative to the spindle 2 because the cross-sectional shape of the drive shaft 3 matches the shape and size of the opening. For example, when the linear actuator 1 is in a more contracted state compared to a more extended state, a larger part of the drive shaft 3 can extend within the hole. The spindle 2 includes a right-handed threaded portion 21 at one end of the spindle 2 (e.g., the end into which the drive shaft 3 is inserted). The right-handed threaded portion 21 is configured to be in threaded contact with a right-handed threaded nut member 4 and thus drive the right-handed threaded nut member 4 in the longitudinal direction according to the rotation direction. Similarly, the spindle 2 has a left-handed threaded portion 22 at the other end of the spindle 2. The left-handed threaded portion 22 is configured to threadably contact the left-handed threaded nut member 5 and thus drive the left-handed threaded nut member 5 in a longitudinal direction opposite to that of the right-handed threaded nut member 4. When the spindle 2 rotates, the right-handed threaded nut member 4 and the left-handed threaded nut member 5 thereby move in opposite linear directions. During extension, the right-handed threaded nut member 4 moves in the direction D1 and the left-handed threaded nut member 5 moves in the direction D2, and vice versa during contraction.

[0050] There is a non-threaded portion 23 of the spindle 2 between the right-hand threaded portion 21 and the left-hand threaded portion 22. The non-threaded portion 23 enables the linear actuator 1 to reach its maximum retracted state without the threads 21,22 of the spindle 2 coming into contact with the oppositely threaded nut members 4,5.

[0051] The right-handed threaded nut member 4 has a first portion 41 and a second portion 42 on two opposite radial sides of the spindle 2 (i.e., on opposite sides along the circumference of the spindle 2). The left-handed threaded nut member 5 also has a first portion 51 and a second portion 52 on opposite sides of the spindle 2. At one end of the right-handed threaded nut member 4, the first portion 41 and the second portion 42 of the right-handed threaded nut member 4 include non-threaded portions 44, 45, which are located adjacent to the left-handed threaded portion 22 of the spindle on two opposite (radial) sides of the spindle in the maximum contraction state of the linear actuator 1. Similarly, the left-handed nut member portion includes non-threaded portions 54, 55, which are adjacent to the right-handed thread 21 of the spindle 2 on two opposite (radial) sides in the maximum contraction state of the linear actuator 1. In the more extended state of the linear actuator 1, the non-threaded portions 44, 45, 54, 55 of the right-handed threaded nut member 4 and the left-handed threaded nut member 5 are at least partially located on the longitudinal sides thereof in the directions D1 and D2, respectively. The non-threaded portions 44 , 45 , 54 , 55 prevent movement of the threads 21 , 22 of the spindle 2 from being interfered with by the oppositely threaded nut members 4 , 5 .

[0052] The first portion 41 and the second portion 42 of the right-handed nut member 4 are attached to each other at one end of the right-handed nut member, which is located on the longitudinal side in the direction D1 of the spindle 2. Likewise, the first portion 51 and the second portion 52 of the left-handed nut member 5 are attached to one end of the left-handed nut member 5, which is located on the longitudinal side in the direction D2 of the spindle 2. The first portion and the second portion of the nut member are thus attached to each other on the opposite sides relative to the non-threaded portion thereof.

[0053] The first and second portions 41 , 42 of the right-hand threaded nut member 4 comprise opening portions which together form an opening for the drive shaft 3 where they are attached to each other.

[0054] Likewise, the first portion 51 and the second portion 52 of the left-hand threaded nut member 5 comprise opening portions which together form an opening for the drive shaft 3, where the first and second portions are attached to each other. The drive shaft 3 can freely rotate relative to the nut members 4, 5. In one embodiment, at least one of the openings in the nut members 4, 5 for the drive shaft 3 can be used as a bearing portion for the drive shaft 3.

[0055] In the drawings and specification, preferred embodiments and examples of the invention have been disclosed, and although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

1. A linear actuator (1) for a height-adjustable column, the linear actuator comprising a threaded spindle (2) having a longitudinal extension along a longitudinal axis, the spindle being adapted to be rotated by a drive shaft (3), wherein: The spindle is provided with a right-hand thread (21) at a first portion of the longitudinal extension and a left-hand thread (22) at a second portion of the longitudinal extension, the linear actuator further comprising: a right-hand threaded nut member (4) threadably connected to the right-hand thread (21) of the spindle (2); and a left-handed threaded nut member (5), the left-handed threaded nut member being threadedly connected to the left-handed thread (22) of the main shaft (2); The right-hand threaded nut member (5) comprises a first portion (41) and a second portion (42) configured to be threadedly connected to the main shaft (2) on opposite sides along the circumference of the main shaft (2); The left-hand threaded nut member (5) comprises a first portion (51) and a second portion (52) configured to be threadedly connected to the main shaft (2) on opposite sides along the circumference of the main shaft (2); wherein, at least in the retracted state of the linear actuator (1), the right-handed threaded nut member (4) and the left-handed threaded nut member (5) extend along the same portion of the longitudinal extension of the spindle (2); and Wherein, when the main shaft (2) rotates, the threaded connection between the right-handed threaded nut member (4) and the left-handed threaded nut member (5) and the main shaft (2) provides the right-handed threaded nut member (4) with respect to the left-handed threaded nut member (5) in opposite linear movements along the longitudinal axis.

2. The linear actuator (1) according to claim 1, wherein: The first portion (41) of the right-handed threaded nut member (4) and the first portion (51) of the left-handed threaded nut member (5) are displaced 85 to 95 degrees, preferably 90 degrees, along the circumference of the main shaft (2), and wherein the second portion (42) of the right-handed threaded nut member (4) and the second portion (52) of the left-handed threaded nut member (5) are displaced 85 to 95 degrees, preferably 90 degrees, along the circumference of the main shaft.

3. A linear actuator (1) according to any one of the preceding claims, wherein: The right-hand thread (21) and the left-hand thread (22) of the main shaft (2) are separated along the longitudinal extension of the main shaft.

4. A linear actuator (1) according to any one of the preceding claims, wherein: The right-hand thread (21) and the left-hand thread (22) are arranged at opposite ends of the longitudinal extension of the main shaft (2).

5. The linear actuator (1) according to any one of claims 1 to 4, wherein: The right-hand threaded nut member (4) supports a first portion and a second portion of the circumference of the spindle (2), and the left-hand threaded nut member (5) supports a third portion and a fourth portion of the circumference of the spindle (2).

6. The linear actuator (1) according to claim 5, wherein: The right-hand threaded nut member (4) and the left-hand threaded nut member (5) together bear against substantially the entire circumference of the spindle (2).

7. A linear actuator (1) according to any one of the preceding claims, wherein: The spindle (2) has a longitudinal hole extending through the spindle (2), and the linear actuator (1) further includes a drive shaft (3) configured to rotate the spindle, wherein the size and shape of the longitudinal hole and the drive shaft are designed so that rotation of the drive shaft provides rotation of the spindle, while the drive shaft is able to move axially relative to the spindle along the longitudinal extension of the spindle.

8. The linear actuator (1) according to any one of claims 1 to 7, wherein: The first and second portions of the right-hand threaded nut member (4) are configured to be attached to each other at one end, and wherein the first and second portions include opening portions that are configured to together form an opening for the drive shaft (3); and Wherein, the first part (51) and the second part (52) of the left-handed threaded nut member (5) are configured to be attached to each other at one end, and wherein the first part and the second part include opening parts, which are configured to form an opening for the drive shaft (3) together.

9. The linear actuator (1) according to any one of claims 1 to 8, wherein: The first portion (41) and the second portion (42) of the right-handed threaded nut member (4) have non-threaded portions (44, 45) which are at least as long as the left-handed threaded portion (22) of the main shaft in the longitudinal direction, and the first portion (51) and the second portion (52) of the left-handed threaded nut member (5) have non-threaded portions (54, 55) which are at least as long as the right-handed threaded portion (21) of the main shaft in the longitudinal direction.

10. The linear actuator (1) according to any one of the preceding claims, further comprising a retaining device (6), wherein: The inner shape of the retaining device (6) matches the outer shape of the right-handed threaded nut member and the left-handed threaded nut member (4, 5), and wherein the retaining device (6) is arranged to retain the right-handed threaded nut member (4) and the left-handed threaded nut member (5).

11. A linear actuator (1) according to any one of the preceding claims, wherein: The first parts (41, 51) and the second parts (42, 52) of the nut members (4, 5) are symmetrically distributed along the circumference of the main axis.

12. A linear actuator (1) according to any one of the preceding claims, wherein: The left-hand thread (22) and the right-hand thread (21) of the main shaft (2) are separated by a non-threaded portion (23), and the non-threaded portion extends along at least 50%, at least 70%, or at least 80% of the longitudinal extension of the main shaft (2).

13. A telescopic column, comprising at least two telescopic tubes, the telescopic column comprising: A linear actuator (1) according to any one of claims 1 to 12; an inner tube attached to the left-hand threaded nut member (5); and an outer tube attached to the right-handed nut member (4); Therein, the inner tube and the outer tube are telescopically movable relative to each other.

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