Linear actuator with anti-rotation mechanism

Abstract

The linear actuator includes elongated first and second bands that cooperate to form a column that can be extended and retracted. Rotatable first and second band guide members guide the first and second bands, respectively, to couple and engage the circumferential turns of the bands. A power actuator rotates the first and second band guide members to extend and retract the retractable column. A base supports the power actuator, the first and second bands, and the first and second band guide members. The anti-rotation mechanism includes a first anti-rotation member attached to the base and a complementary second anti-rotation member attached to the first band and / or the second band, the first and second anti-rotation members engaging with each other to prevent rotation of the column portion relative to the base. The engagement of the anti-rotation members is achieved at a non-point contact area along the outer periphery of the column.

Description

Technical Field

[0001] Cross-reference data This application claims priority based on U.S. Provisional Patent Application No. 63 / 136,310.

[0002] The present invention relates to a linear actuator including a column (columnar part) that can project and retract (appear and disappear), formed by engaging one band with another band, and particularly relates to an anti-rotation mechanism used in the linear actuator.

Background Art

[0003] As a machine for moving the position of a loaded object, there is a linear actuator that forms a column (columnar part) that can project and retract in the vertical direction, that is, can appear and disappear, by bending a flat band in a spiral shape, and a load is engaged with one end of the column. This type of machine is mainly used for raising and lowering a load, but the application is not limited thereto.

[0004] Such a linear actuator includes a hollow generally cylindrical rotor rotatably mounted on a base fixed to the ground. A motor selectively operates the rotor. The first horizontal band is stacked vertically in a spiral shape and stored in the first band magazine, and the second vertical band is stacked horizontally in a spiral shape and stored in the second band magazine located coaxially around the rotor. The lower end of each band is always located in its respective magazine, and the upper end of each band is fixedly attached to a load-bearing platform that engages under the load to be lifted. When the rotor rotates, each turn, that is, each turn, of the vertically extending spiral band is guided between two consecutive turns of the horizontal band in the vertical direction and arranged in a spiral shape, gradually forming a column that can project in the vertical direction. More specifically, the load of the load supported by the column is transmitted to the rotor supporting the horizontal band through consecutive turns of the vertically and horizontally arranged bands, and finally transmitted to the base part and the ground that generally support the whole through ball bearings.

[0005] Such devices have been improved by providing an interconnection mechanism that interconnects horizontal and vertical bands. Specifically, the first band includes teeth and the second band includes an opening, and the teeth of the first band engage with the opening of the second band to interconnect the first and second bands. This configuration helps prevent disengagement of the bands forming the column in a series of turns, and also allows the linear actuator to be used with its longitudinally extending axis not being perpendicular, for example, by extending the linear actuator horizontally to the ground.

[0006] In either of the two linear actuator configurations described above, a rotor rotates around first and second bands and is provided with a guide that carries guides that force the consecutive turns of the first and second bands to interconnect in a discrete (spaced) arrangement to form a vertical column shape. The guide carried by the rotor of the linear actuator comprises a first guide member and a second guide member, the first guide member being, for example, a helical groove on the rotor that guides the turns of the first band from the first band magazine to form a vertical column, and the second guide member being, for example, an insertion pad that slidably contacts the outer surface of the second band and guides the turns of the second band from the second band magazine to form a vertical column.

[0007] While the rotor rotates together with the first and second guide members supported on it, the vertical column itself does not rotate. If the vertical column were rotatable, the first and second bands would not be forced to engage with each other, so the vertical column would not be formed, and the load would not be lifted.

[0008] To prevent the rotation of the first and second bands forming the vertical column, a load support base for the linear actuator is known, in which the upper ends of the first and second bands are fixed, and the load being lifted is also fixed to the load support base, thereby preventing the load from rotating. For example, if the load being lifted by the linear actuator is a theater stage, the theater stage can be positioned to be guided along a vertical rail, allowing for vertical movement but preventing rotation.

[0009] In other words, conventional linear actuators with interlocking bands require the attachment of a lifting load, which must be used as a means of preventing the column from rotating.

[0010] Some conventional linear actuators offer solutions that eliminate the need to use a load to prevent column rotation. In these conventional linear actuators, a ring of anti-rotation rollers is mounted on a fixed base of the linear actuator and spaced longitudinally, working in cooperation with teeth on a first band to prevent rotation of the vertical column. The teeth extend through openings in a second band, interconnecting the continuous turns of the second band and protruding beyond the outer wall surface of the column. When the teeth of the column move up and down during the extension or retraction of the vertical column, the teeth slide within the space between the anti-rotation rollers. Thus, the teeth are able to move freely in the vertical direction while making point contact with the corresponding rollers. As a result, even in configurations where the rotation of the load lifted by the linear actuator is not prevented, or where the linear actuator is not fixed to the load at its upper end, the anti-rotation device associated with this protruding column can prevent the column from rotating and allow the column to be formed as intended.

[0011] One problem with such a system is that the anti-rotation roller ring is positioned in a plane perpendicular to the axis extending longitudinally along the column, and the contact between the teeth and the anti-rotation roller is point-contact; that is, one tooth contacts one roller at one point on the outer circumference of the column, or a very small number of teeth contact a very small number of rollers at substantially one point on the outer circumference of the column. When forming the column, the position of the point-contact portion between the teeth and rollers moves along the outer circumference of the vertical column, and each roller continuously acts as an anti-rotation means. When the teeth and rollers contact tangentially, there is no uniform spread of the contact area along the circumferential direction of the column, and it is always essentially point-contact, which is not an ideal form. Because there is no uniform spread of the point-contact portion along the circumferential direction of the vertical column, there is a disadvantage in that undesirable tangential and radial mechanical stress is generated on the column. [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] Therefore, the object of the present invention is to provide a rotation prevention system for a linear actuator that eliminates the disadvantages of the prior art system. [Means for solving the problem]

[0013] According to the present invention, a linear actuator is provided, The first band is long and narrow, A long, slender, substantially flat second band, wherein the first band and the second band each have a receiving portion and a column portion, the respective receiving portions of the first band and the second band are separated from each other, the respective column portions of the first band and the second band engage with each other to form a column that can protrude and retract, i.e., can move in and out, and the column portion of the second band forms a spiral about its longitudinal axis, the second band and A rotatable first band guide member that guides each turn, which is a spiral extension of the first band, from the housing portion to the column portion, A rotatable second band guide member that guides the turn of the second band from its housing portion to its column portion, A power actuator that causes the first band guide member and the second band guide member to rotate, thereby enabling the retractable column to protrude or retract, The power actuator, the first band, the second band, the first band guide member, and the base portion supporting the second band guide member, A rotation prevention mechanism comprising a first rotation prevention member attached to the base portion, and a second rotation prevention member attached to at least one of the first band and the second band, which is complementary to the first rotation prevention member, wherein the first rotation prevention member and the second rotation prevention member engage with each other in the column portion of the first band and the column portion of the second band, thereby preventing the retractable column from rotating relative to the base portion. A linear actuator is provided in which the engagement between the first anti-rotation member and the second anti-rotation member is achieved in a non-point contact area along the outer circumference of the retractable column.

[0014] In one embodiment, the engagement between the first anti-rotation member and the second anti-rotation member includes engagement between the first anti-rotation member and the second anti-rotation member over a portion of at least one full turn of the retractable column.

[0015] In one embodiment, the first anti-rotation member and the second anti-rotation member each include a first and second abutment member that abut each other in the tangential direction of the retractable column at each circumferential position of the retractable column.

[0016] In one embodiment, the first anti-rotation member and the second anti-rotation member have teeth and grooves, the teeth are provided on the base portion or at least one of the first band and the second band, the grooves are provided on the base portion or the other of the first band and the second band, the grooves extend parallel to the longitudinal axis, and when the retractable column is extended or retracted, the teeth are slidable relative to the groove in a direction parallel to the longitudinal axis within the groove, but the teeth are biased toward the wall of the groove to prevent the retractable column from rotating about the longitudinal axis.

[0017] In one embodiment, the teeth are provided on one of the first band and the second band, and the grooves are provided on the base portion.

[0018] In one embodiment, the groove is provided on an anti-rotation ring that surrounds a portion of the retractable column in the circumferential direction.

[0019] In one embodiment, the present invention further includes a rotor supporting the first band guide member and the second band guide member, the rotor being operably coupled to the power actuator so as to be rotatable by the power actuator, and the rotor supporting the first band and the second band together with the first band guide member and the second band guide member.

[0020] Furthermore, according to the present invention, a rotation prevention ring for use in a linear actuator, The linear actuator is an elongated, substantially flat band, The aforementioned band has a column portion and a housing portion, The band is configured such that turns engage with each other in the column portion, forming a spiral around the longitudinal axis of the linear actuator, thereby creating a column that can extend and retract, i.e., a retractable column, and the retractable column is adapted to pass through the anti-rotation ring. The band is arranged such that each turn does not engage with each other and is separated in the accommodating portion, and the band, a rotatable band guide member that guides turns, which are each circumferences of the helical extension of the band, from the accommodating portion to the column portion, an interconnecting member that interconnects the turns of the band in the column portion with another turn, a power actuator that rotates the band guide member to project or accommodate the retractable column, a base portion that supports the power actuator, the band, and the band guide member, and teeth protruding from the retractable column, The anti-rotation ring further includes an attachment for fixing the anti-rotation ring to the base portion, and a groove provided coaxially with the anti-rotation ring on the inner surface of the anti-rotation ring, The groove is configured to cooperate with the teeth of the linear actuator such that the teeth are movable relative to the base portion in a direction parallel to the longitudinal axis within the groove, but prevent rotation about the longitudinal axis of the retractable column, There is provided an anti-rotation ring in which the engagement between the teeth and the groove is achieved in a non-point contact area along the outer periphery of the retractable column.

[0021] Furthermore, according to the present invention, there is provided a linear actuator, which is an elongated and substantially flat band, the band having a column portion and an accommodating portion, in the column portion of the band, turns, which are each circumferences of the helical extension, engage with another turn to form a helix about the longitudinal axis of the linear actuator, thereby enabling protrusion and retraction, that is, forming a retractable column, the band is arranged such that each turn does not engage with each other and is separated in the accommodating portion, and the band, A rotatable band guide member that guides each turn of the band from the housing portion to the column portion, An interconnecting member that interconnects the turns of the band in the column portion with other turns, A power actuator that rotates the band guide member to extend or retract the retractable column, The power actuator, the band, and the base portion supporting the band guide member, A rotation prevention mechanism comprising a first rotation prevention member attached to the base portion and a second rotation prevention member attached to the band, which is complementary to the first rotation prevention member, wherein the first rotation prevention member and the second rotation prevention member engage with each other in the column portion of the band, thereby preventing the retractable column from rotating relative to the base portion. A linear actuator is provided in which the engagement between the first anti-rotation member and the second anti-rotation member is achieved in a non-point contact area along the outer circumference of the retractable column. [Brief explanation of the drawing]

[0022] [Figure 1] Figure 1 is a front view of a linear actuator equipped with a rotation prevention device according to the present invention. [Figure 2] Figure 2 is a partially cutaway perspective view showing the linear actuator shown in Figure 1, with the base, rotor, second band, and part of the anti-rotation device partially cut away to show internal elements, and represents the case where most of the vertical column is in the first position where it is housed. [Figure 3] Figure 3 is a partially cutaway perspective view showing the linear actuator shown in Figure 1. The base, rotor, second band, and part of the anti-rotation device are partially cut away to show internal elements, and the figure shows the case where the vertical column is in a protruding state, partially extending from the position shown in Figure 2. [Figure 4]Figure 4 is a partially cutaway upper perspective view showing an enlarged view of the linear actuator casing from Figure 1, along with the anti-rotation ring and the mounting plate for attaching the anti-rotation ring to the casing. [Figure 5] Figure 5 is a lower perspective view showing the elements of Figure 4 as exploded views. [Figure 6] Figure 6 is a partially cutaway perspective view showing an enlarged view of the anti-rotation ring of the linear actuator in Figure 1, along with one to two turns of the extended form of the first and second bands forming the protruding column. [Figure 7] Figure 7 is a partially cutaway perspective view showing the anti-rotation device of the linear actuator in Figure 1, magnified with one to two turns of the first band forming the protruding column (together with Figure 8, it shows the vertical movement of the first band relative to the anti-rotation device). [Figure 8] Figure 8 is a partially cutaway perspective view showing the anti-rotation device of the linear actuator in Figure 1, magnified with one to two turns of the first band forming the protruding column (together with Figure 7, it shows the vertical movement of the first band relative to the anti-rotation device). [Modes for carrying out the invention]

[0023] Figures 1 to 3 show a linear actuator 10 according to the present invention used to displace a load (not shown) along a longitudinally extending axis A. In most applications, axis A is vertical, and the linear actuator 10 is used to raise and lower a load vertically; however, as described below, axis A may be non-vertical because multiple bands forming the linear actuator 10 are interconnected. For simplicity, the following description may assume that axis A is vertical, but it should be understood that the direction of this axis is not limited.

[0024] The linear actuator 10 is placed on the ground and includes a hollow rotor 12 rotatably supported on a fixed base 14. The base 14 includes a flat base plate 16 and a central post 18 that rises upright from the base plate 16. The rotor 12 is rotatably supported by the central post 18 by high load-bearing bearings 20, 22.

[0025] The base portion 14 is fixed to the base plate 16 and includes a casing 32 extending upright therefrom. Specifically, as shown in Figures 4 and 5, the casing 32 includes four spaced side walls 32a, 32b, 32c, and 32d, which support an upper wall 32e, the upper wall 32e having a central circular opening 32f of the casing. The casing 32 extends spaced above the base plate 16 from the rotor 12 and partially encloses the rotor 12. The casing 32 may have a different configuration than that shown in the figures, for example, it may have a continuous, complete peripheral wall instead of the spaced side walls 32a, 32b, 32c, and 32d, and may include various other modifications as will be apparent to those skilled in the art.

[0026] The linear actuator 10 includes a power actuator. The power actuator includes a motor 24 with a control panel 26, and selectively rotates the rotor 12 by a pair of interconnected gear wheels 28, 30, which are mounted on the motor 24 and the rotor 12, respectively. The base portion 14 includes a motor support 31 supported by a casing 32, which supports the motor 24.

[0027] The linear actuator 10 forms a column (columnar section), i.e., a retractable column 33, by means of a first band 34 and a second band 38, which can extend upward by connecting the bands and retract by retracting the bands. In the column, the first band 34 is used to interconnect the consecutive turns of the second band 38 and to transmit the load from one turn of the second band 38 to the next.

[0028] More specifically, the first band 34 has a housing portion 34a that is stacked in a spiral and housed in a first band magazine 36, which is an annular space formed inside the lower part 12a of the rotor 12. The housing portion 34a of the first band rests on the bottom wall 12d of the rotor 12 (sliding over it as the rotor 12 rotates) or is suspended above the bottom wall 12d of the rotor 12, as shown in Figures 2-3. The second band 38 has a housing portion 38a that is stacked in a horizontal spiral and housed in a second band magazine 40, which is an annular space formed between the rotor 12 and the casing 32, radially outward from the annular upper wall portion 12b of the rotor 12. The housing portion 38a of the second band rests on the horizontal support wall portion 12c of the rotor 12 and slides over it as the rotor 12 rotates. An opening 12e is formed in the upper wall portion 12b of the rotor 12, and the second band 38 extends through this opening 12e into a space radially inward of the upper wall portion 12b.

[0029] The first band 34 and the second band 38 have column portions 34b and 38b that form a retractable column 33, as detailed below. As the column 33 gradually protrudes or retracts, the lengths of the respective column portions 34b and 38b of the first and second bands change inversely proportional to the change in the lengths of their respective containment portions 34a and 38a.

[0030] The upper ends of the first and second bands 34 and 38 are fixedly attached to a load engaging member 42 that engages with the load to be displaced. When the linear actuator 10 is positioned on the ground with axis A vertical (typically), the load to be displaced is raised and lowered by the linear actuator 10, and as a result the load engaging member 42 supports the weight of this load. A platform or other intermediate structure (not shown) may be fixed to the load engaging member 42 between the load and the load.

[0031] The rotor 12 includes a first band guide member in the form of a helical groove 44 formed in the inner wall 46 of the rotor 12. The rotor 12 also includes a second band guide member in the form of an insertion pad 48 for a second band supported by the rotor 12. When the rotor 12 is rotated in a first direction by the motor 24 to project the column 33, each turn of the second band 38 is guided by the insertion pad 48 for the second band from the second band magazine 40 through the opening 12e of the rotor to form the column 33. In the column, the second band 38 is arranged helically such that the upper edge of each of its consecutive turns overlaps the lower edge of the upper adjacent turn. Simultaneously, each turn of the first band 34 is guided from the first band magazine 36 through a spiral groove 44 to form a column 33, where teeth 50 on the outer circumference of the first band 34 engage with openings 52 and 54 on the upper and lower edges of the second band 38, where two turns overlap, thereby interconnecting each of the two consecutive turns of the column portion 38b of the second band 38. In this way, the wall of the column 33 is formed by the second band 38 of the column portion 38b, and the teeth 50 of the first band 34 cooperate with the openings 52 and 54 of the second band 38 as interconnecting members, which are used to connect the consecutive turns of the column portion 38b of the second band 38 and to transmit the load to each of the consecutive turns of the second band 38 (see Figure 6).

[0032] The load of the load displaced by the linear actuator 10 (for example, an article supported on the upper side when axis A is vertical) is transmitted, more specifically, to the load engaging member 42, then through the successive turns of the column portions 34b and 38b of the first and second bands, then to the rotor 12 on which the first band 34 rests in the helical groove 44, then to the base portion 14 via the bearings 20 and 22, and finally to the ground on which the base plate 16 rests.

[0033] The motor 24 can also rotate the rotor 12 in a second direction opposite to the first direction, thereby retracting the column 33. At this time, the first and second band guide members (spiral groove 44, insertion pad 48) gradually move the turns of the first and second bands 34 and 38 away from the column 33 and guide them to the first and second band magazines 36 and 40, respectively.

[0034] The above explanation pertains to the standard operation of a linear actuator of a conventional structure.

[0035] According to the present invention, as shown in Figures 1 to 8, a rotation prevention mechanism is provided that prevents the rotation of the column 33 even if the load that displaces the column 33 is not used as part of the means to prevent this rotation, that is, even if the load engaging member 42 is not prevented from rotating.

[0036] The rotation prevention mechanism of the linear actuator 10 consists of a first rotation prevention member 60 attached to the base portion 14 (more specifically, the casing 32), and a second rotation prevention member in the form of a protruding end of the teeth 50 of a first band that cooperates with the first rotation prevention member as described later.

[0037] The first anti-rotation member 60 includes a ring 62 having an annular shoulder portion 80 at its lower end, the shoulder portion 80 being fitted into a circular opening 32f of the casing 32 and resting on the upper wall 32e of the casing 32. A recess 82 is formed on the periphery of the lower wall portion 83 of the ring 62 located below the shoulder portion 80, and this recess 82 engages with a tab 84 that protrudes radially inward from the upper wall 32e of the casing within the circular opening 32f.

[0038] An annular groove 86 is formed in the lower wall 83 of the ring 62 below the shoulder 80. The groove 86 is located below the upper wall 32e of the casing when the ring 62 is placed on the upper wall 32e together with the shoulder 80. A pair of mounting plates 88 and 90 engage with the groove 86 below the upper wall 32e of the casing, at which point the upper wall 32e of the casing is sandwiched between the shoulder 80 of the ring and the mounting plates 88 and 90, and the mounting plates 88 and 90 are fixed to the upper wall 32e of the casing by bolts 92.

[0039] The ring 62 is configured to have a diameter that allows the column 33 to fit snugly, and the inner wall 94 of the ring 62 has a number of linear grooves 70 that are parallel to axis A. The first band 34 is provided with teeth 50 that protrude from its outer edge beyond the overlapping edge of the second band 38, and each groove 70 is configured to have a depth and width such that one tooth 50, or several teeth 50 aligned parallel to axis A, fits snugly and engages in a longitudinally slidable manner.

[0040] During use, the numerous teeth 50 slidably engage with a corresponding groove 70 as the column 33 extends and protrudes or retracts. More specifically, as shown in Figures 7 and 8, the teeth 50 slide within the groove 70 in a direction parallel to axis A, forcing the first band 34 to move parallel to axis A. In fact, while engaged in the groove 70 in this manner, the teeth 50 abut against the side wall of the groove 70 of the ring 62 in the tangential direction of the column, preventing rotation of the column 33. The ring 62 is attached to the casing 32 and rotation is prevented, in particular by the engagement of the tab 84 in the recess 82. Thus, in addition to enabling the interconnected engagement of the first band 34 and the second band 38, the teeth 50 also function as a second anti-rotation member that works in cooperation with the first anti-rotation member 60 to prevent rotation of the column 33 about axis A.

[0041] In one embodiment (not shown), the first band may be positioned outside the second band and configured to have teeth protruding inward. In such an embodiment, an anti-rotation device positioned inside the second band receives the inwardly protruding teeth in grooves provided on its outer surface.

[0042] In another embodiment (not shown), the column is formed of a single band similar to the second band of the first embodiment, but unlike the second band, teeth are provided on one of the upper or lower edges of the single band, and an opening corresponding to the teeth is provided on the other edge. In this embodiment, the interconnecting members that interconnect the turns of the band in the column portion may be, for example, teeth of the band that engage with the openings of the band itself. Furthermore, regardless of whether the teeth extend inward or outward from the column, an anti-rotation device having grooves into which the teeth engage may be used to prevent the column from rotating.

[0043] In another embodiment (not shown), one of the first and second bands is provided with a plurality of anti-rotation pins that are different from the interconnected teeth. These anti-rotation pins are configured to engage with an anti-rotation device.

[0044] Furthermore, it is also possible to provide a linear actuator (not shown) without teeth for interconnection between two bands. In this case, the two bands are mounted on each other. Each mounting is known in the prior art. In such embodiments, teeth or pins are provided on one of the bands solely for the purpose of preventing rotation and do not serve an interconnection function.

[0045] In all embodiments, according to the present invention, an anti-rotation device and teeth or pins cooperate to form an anti-rotation mechanism that achieves engagement in a non-point contact area. Unlike the prior art, which uses a set of planar ring-shaped anti-rotation rollers in which teeth engage in point contact between rollers along the circumferential direction of the roller rings, the present invention enables engagement by non-point contact, in which multiple teeth engage with multiple grooves in the anti-rotation device.

[0046] In the embodiment shown in the drawings, the length of the anti-rotation ring 62 is sufficient to engage the teeth 50 with the groove 70 for at least one entire turn of the first band 34, so that the tangential contact points of the teeth 50 for preventing rotation with the groove 70 are distributed around the entire circumference of the periphery of the column 33, thereby reducing the mechanical stress on the column 33. As shown in the drawings, it is also possible to have two or more turns of the band having teeth 50 that engage with the ring 62.

[0047] Furthermore, the longitudinal length of the ring 62 is such that the column 33 engages snugly within the ring 62, thereby helping to resist radial forces applied to the column, including the bending of the column 33.

Claims

1. A linear actuator, The first band is long and narrow, A second band that is elongated and substantially flat, wherein the first band and the second band each have a receiving portion and a column portion, the respective receiving portions of the first band and the second band are separated from each other, the respective column portions of the first band and the second band engage with each other to form a column that can protrude and retract, i.e., can move in and out, and the column portion of the second band forms a spiral about its longitudinal axis, the second band and A rotatable first band guide member that guides each turn, which is a spiral extension of the first band, from the housing portion to the column portion, A rotatable second band guide member that guides the turn of the second band from its housing portion to its column portion, A power actuator that causes the first band guide member and the second band guide member to rotate, thereby enabling the retractable column to protrude or retract, The power actuator, the first band, the second band, the first band guide member, and the base portion supporting the second band guide member, A rotation prevention mechanism comprising a first rotation prevention member attached to the base portion, and a second rotation prevention member attached to at least one of the first band and the second band, which is complementary to the first rotation prevention member, wherein the first rotation prevention member and the second rotation prevention member engage with each other in the column portion of the first band and the column portion of the second band, thereby preventing the retractable column from rotating relative to the base portion. A linear actuator in which the mutual engagement between the first anti-rotation member and the second anti-rotation member is always achieved in a contact area over at least one full turn along the outer circumference of the retractable column.

2. A linear actuator according to claim 1, A linear actuator in which the first anti-rotation member and the second anti-rotation member each include a first and second abutment member that abut each other in the tangential direction of the retractable column at each circumferential position of the retractable column.

3. A linear actuator according to claim 2, The first anti-rotation member and the second anti-rotation member have teeth and grooves, the teeth are provided on the base portion or on at least one of the first band and the second band, and the grooves are provided on the base portion or on at least one of the first band and the second band, A linear actuator wherein the groove extends parallel to the longitudinal axis, and when the retractable column is extended or retracted, the teeth are slidable relative to the groove in a direction parallel to the longitudinal axis within the groove, but the teeth are biased toward the wall of the groove to prevent rotation of the retractable column about the longitudinal axis.

4. A linear actuator according to claim 3, A linear actuator wherein the teeth are provided on one of the first band and the second band, and the grooves are provided on the base portion.

5. A linear actuator according to claim 4, The groove is provided on a linear actuator, which is provided on an anti-rotation ring that surrounds a portion of the retractable column in the circumferential direction.

6. A linear actuator according to claim 1, The system further includes a rotor that supports the first band guide member and the second band guide member, The rotor is operably coupled to the power actuator so that the rotor can be rotated by the power actuator. The rotor is a linear actuator that supports the first band and the second band together with the first band guide member and the second band guide member.

7. A rotation prevention ring for use in linear actuators, The linear actuator is an elongated, substantially flat band, The aforementioned band has a column portion and a housing portion, The band is configured such that turns engage with each other in the column portion, forming a spiral around the longitudinal axis of the linear actuator, thereby creating a column that can extend and retract, i.e., a retractable column, and the retractable column is adapted to pass through the anti-rotation ring. The band is arranged such that each turn in the receiving portion does not engage with each other and is separated, A rotatable band guide member that guides each turn, which is a spiral extension of the band, from the housing portion to the column portion, An interconnecting member that interconnects the turns of the band in the column portion with other turns, A power actuator that rotates the band guide member to extend or retract the retractable column, The power actuator, the band, and the base portion supporting the band guide member, The column comprises teeth protruding from the retractable column, The aforementioned anti-rotation ring further, An attachment for fixing the anti-rotation ring to the base portion, The inner surface of the anti-rotation ring includes a groove provided coaxially with the anti-rotation ring, The groove is configured to cooperate with the teeth so that the teeth can move within the groove relative to the base in a direction parallel to the longitudinal axis, but to prevent the retractable column from rotating about the longitudinal axis. An anti-rotation ring in which the engagement between the teeth and the groove is always achieved over a continuous contact area spanning at least one full turn along the outer circumference of the retractable column.

8. A linear actuator, It is a long, narrow, and essentially flat band. The aforementioned band has a column portion and a housing portion, In the column portion, the band has turns that engage with each other, forming a spiral around the longitudinal axis of the linear actuator, thereby creating a column that can extend and retract, i.e., a column that can move in and out. The band is arranged such that each turn in the receiving portion does not engage with each other and is separated, A rotatable band guide member that guides each turn of the band from the housing portion to the column portion, An interconnecting member that interconnects the turns of the band in the column portion with other turns, A power actuator that rotates the band guide member to extend or retract the retractable column, The power actuator, the band, and the base portion supporting the band guide member, A rotation prevention mechanism comprising a first rotation prevention member attached to the base portion and a second rotation prevention member attached to the band, which is complementary to the first rotation prevention member, wherein the first rotation prevention member and the second rotation prevention member engage with each other in the column portion of the band, thereby preventing the retractable column from rotating relative to the base portion. A linear actuator in which the mutual engagement between the first anti-rotation member and the second anti-rotation member is always achieved in a contact area over at least one full turn along the outer circumference of the retractable column.

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