Linear actuator

Abstract

The linear actuator includes upper and lower frame portions movable relative to each other in a vertical direction along a central axis, and a first band and a second band coupled to each other to form a telescopic column, the second band forming a wall of the vertical column, and it is the second band that is supported by a rotor that is rotatably supported by the lower frame portion to relieve mechanical stress on the first band.

Description

Technical Field

[0001] The present invention relates to a linear actuator that forms a retractable column using a pair of bands coupled to each other.

Background Art

[0002] In order to displace a load, it is known to use a linear actuator having a retractable telescopic column formed by a pair of helical bands connected to each other. This type of device is mainly, but not necessarily, used for raising and lowering a load, and in such a case, the telescopic column is formed vertically.

[0003] One form of such a conventional linear actuator 20 is shown in FIGS. 6 to 8. The linear actuator 20 includes a hollow cylindrical rotor 22 rotatably supported on a base 24 by ball bearings 45a, 45b. The base 24 is configured to be fixed to the ground (e.g., bolted). The output shaft of a motor 26 is drivingly coupled to the rotor 22 via a gear wheel 28 to selectively rotate the rotor 22.

[0004] The linear actuator 20 includes a first horizontal band 30 having a housed state portion 30a spirally and vertically stacked in a first band magazine 32 disposed around the lower part of the rotor 22, and a second vertical band 34 having a housed state portion 34a spirally and horizontally stacked in a second band magazine 36 coaxially disposed around the rotor. (As shown in the figure,) the casing is attached around the gear wheel 28, the rotor 22, and the second band magazine 36, and a vertical column 38 and a hole extending through the vertical column 38 are provided at the upper part of the casing. The vertical column 38 is formed from a column state portion 30b of the first band 30 and a column state portion 34b of the second band 34. The lower ends of the respective bands 30, 34 are always disposed in their respective magazines 32, 36, and the upper ends of the respective bands 30, 34 are attached so as to be fixed to a load support platform 40 that engages with the lower part of a load that is displaced in the vertical direction.

[0005] When the rotor 22 is rotated in a first direction together with the motor 26 to pull out the vertical column 38 so that the platform 40 is lifted, an insertion pad 42 supported by the outer portion of the column 38 by the rotor 22 gradually biases the turn of the vertical band 34 spirally inward in the radial direction toward the space between two consecutive turns in the vertical direction of the horizontal band 30. At the same time, the spiral groove 44 of the rotor 22 disposed inside the vertical band 34 gradually lifts the turns of the horizontal band 30 so that the column state portion 30b of the horizontal band 30 abuts radially against the respective upper and lower edges where two consecutive turns of the column state portion 34b of the vertical band 34 overlap. Further, teeth 46 provided on the outer periphery of the column state portion 30b of the horizontal band 30 engage with the overlapping edge or the hole 48 in the edge of the vertical band 34 to detachably couple each set of consecutive turns of the column state portion 34b of the vertical band 34. As a result, as the turns of the horizontal band 30 and the vertical band 34 shift from the housed state portion to the column state portion, the telescopic vertical column 38 is gradually pulled out.

[0006] The telescopic column 38 is received when the motor 26 rotates the rotor 22 in the opposite direction, and as a result, the platform 40 descends. The turns of the vertical band 30 and the horizontal band 34 are then gradually disengaged from each other and guided separately to their respective magazines 32, 36.

[0007] As shown in FIG. 8, the two lowermost turns 30''' and 30'''' of the horizontal band 30 forming the column 38 engage with the two lowermost turns 44'' and 44''' of the vertically wide groove 44 such that the horizontal band 30 is not yet supported by the groove 44 at that point. The purpose of the two lowermost turns 44'' and 44''' of the groove 44 is to guide the horizontal band 30 from its received state portion towards its column state portion, i.e., to align and connect the horizontal and vertical bands 30, 34 to form the column 38 by supporting relatively less load (objects) compared to the upper turn 30'' that still supports no load (objects) or engages with the rotor 22. This alignment and connection mode of the bands 30, 34 is further achieved by the lowermost turn 34'''' of the vertical band 34 being horizontally guided by the insertion pad 42 such that the horizontal and vertical bands 30, 34 are sandwiched between the insertion pad 42 and the rotor 22. More specifically, the insertion pad 42 applies a first horizontal force H1 to the lowermost turn 34'''' of the vertical band 34 forming the column 38, but this horizontal force is counteracted by two opposing forces H2 and H3 on the inner wall 44c of the groove 44 with respect to the two lowermost turns 30''' and 30'''' of the horizontal band 30 that is part of the column 38 ((H2 + H3)=H1). Thereby, not only can the bands 30, 34 engage with each other, but the column 38 can be horizontally stabilized against the force of the insertion pad 42 itself, and also against possible lateral or transverse loads (objects) applied to the column 38, including loads (objects) that may be off - center with respect to the vertical axis of the column 38.

[0008] As further shown in FIG. 8, the load of column 38 itself, and more importantly, the load of any article (not shown) including any article or structure supported by column 38 and arranged vertically is transmitted vertically by the continuous rotation of the column-like portions 30b, 34b of bands 30, 34. More specifically, in each turn of the horizontal band 30 not supported by the rotor 22, as shown as force F1, the load of column 38 is transmitted to turn 30' of the horizontal band 30 through a certain turn 34' of the vertical band 34, and is offset by the reaction force F2 from the lower turn 34'' of the vertical band 34 that is vertically adjacent to the turn 34' of the vertical band 34 where the reaction force F2 is transmitted.

[0009] The two turns 34', 34'' of the vertical band 34 on each turn 30' of the horizontal band 30 not supported by the rotor 22 apply a shearing force to the horizontal band 30. This is the first mechanical stress induced laterally in the horizontal first band 30, which is approximately equal in each turn of the column-like portion 30a of the first band 30.

[0010] The load on column 38 is transmitted to rotor 22 from the uppermost turn 30'' that engages with groove 44 of rotor 22. More specifically, the load supported by vertical column 38 is transmitted to the uppermost turn 30'' of horizontal band 30, as shown as force F3. Since this turn 30'' of horizontal band 30 forms a cantilever beam within groove 44, two main resultant reaction forces R1 and R2 will concentrate over time. The first resultant force R1 is generated at the lower wall 44a of groove 44 near the outer edge, and the second resultant force R2 is generated at the upper wall 44b near end wall 44c. As a result, a torsional force with slight local deformation is effectively induced at the rotor support turn 30'' of horizontal band 30. This is the second mechanical stress induced in the first band 30. However, the turns of horizontal band 30 that form the columnar state portion 30b move up and down. In this case, since only the turns supported by rotor 22 are affected, this torsional stress on the horizontal first band 30 will not be the same along the entire length of the columnar state portion 30b of the first band 30 and will vary. This fluctuating torsion causes fatigue in horizontal band 30, and it is necessary to mechanically overdesign (i.e., mechanically enhance the resistance) horizontal band 30 to counteract this fatigue.

[0011] The load on column 38 may also be partially transmitted to rotor 22 through the other two turns 30''' and 30'''', but to a lesser extent than that transmitted through the uppermost turn 30'' that engages with rotor 22.

Summary of the Invention

Means for Solving the Problems

[0012] The present invention relates to a linear actuator comprising the following. Upper and lower frame portions configured to be movable relative to each other in a direction perpendicular to the central axis along the central axis, An elongated first band wound in a helical stack around the central axis, It has turns wound in a roll so as to overlap each other, and the turns are wound around an axis substantially parallel to the central axis in a lateral direction, including a bamboo spring-shaped elongated and substantially flat second band. The first band includes a housed state portion separated from the second band and a column state portion engaged with the second band. The second band includes a housed state portion in which the turns are nested with each other and separated from the first band, and a column state portion in which the turns form a helix around the central axis and are arranged at substantially equal radial distances therefrom, and by engaging with the column state portion of the first band, a wall of a vertical column is formed. Each column state portion of the first and second bands has an end attached to one of the upper and lower frame portions. The linear actuator further includes a horizontal guide member that is supported by the other of the first and second frame portions to which the ends of each column state portion of the first and second bands are attached, and horizontally guides the turns of the second band between the housed state portion and the column state portion. a second band support that is supported by the lower frame portion and vertically supports the column state portion of the second band to support the load of the column, and a power source that is supported by one of the upper and lower frame portions and selectively causes the column to protrude and retract by causing rotation between the horizontal guide member and the first and second bands.

[0013] In an embodiment, the ends of the column state portions of the first and second bands are attached to the upper frame portion, the first and second bands do not rotate with respect to the upper and lower frame portions, the horizontal guide member is rotatably supported by the lower frame portion, and the power source is supported by the lower frame portion and rotates the horizontal guide member.

[0014] In one embodiment, the second band support is also rotatably supported by the lower frame portion.

[0015] In one embodiment, what engages with the second band support is a turn below the columnar state portion of the second band.

[0016] In one embodiment, the horizontal guide member includes an insertion member for changing the second band from the housed state portion to the columnar state portion when the column is pulled out, and a reaction force member for countering the horizontal force of the insertion member against the column.

[0017] In one embodiment, the insertion member, the reaction force member, and the second band support are supported by a rotor that is rotatably supported by the lower frame portion.

[0018] In one embodiment, the insertion member is an insertion pad supported at a distance outside the reaction force member by the rotor, and the first band abuts horizontally against the reaction force member in order to counter the horizontal force of the insertion pad against the second band.

[0019] In one embodiment, the second band support is a flange provided on a rotor that protrudes radially from the central axis.

[0020] In one embodiment, the rotor includes a helical groove that engages with the first band in order to stabilize the column by preventing the first band from separating from the lower frame portion.

[0021] In one embodiment, the first band includes a number of teeth that extend radially away from the central axis, and these teeth engage with openings provided at the overlapping upper and lower edges of the second band in the columnar state portions of the first and second bands, and are detachably meshed with the columnar state portion of the first band in consecutive turns of the columnar state portion of the second band.

Brief Description of the Drawings

[0022]

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Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0023] FIGS. 1 to 5 show a linear actuator 110 according to the present invention used to displace a load (not shown) along a vertical axis A. The linear actuator 110 includes a hollow rotor 112 rotatably supported above a base 114 that is placed on the ground and intended to be fixed to the ground. The base 114 includes a flat base plate 116 and a central post 118 that stands upright from the base plate 116. High load-bearing bearings 120, 122 enable the rotor 112 to be rotatably supported by the post 118. A generally tubular casing (not shown in the drawings to show the internal components of the linear actuator 110) is attached to the base 114 and generally covers most of the outer periphery of the rotor 112.

[0024] The rotor 112 includes inner and outer lower portions 112a, 112b that are attached to the horizontal portion 112c and project downward from the horizontal portion 112c and are arranged at radial intervals. The rotor 112 also includes inner and outer upper portions 112d, 112e that are attached to the horizontal portion 112c and project upward from the horizontal portion 112c and are radially spaced apart. A column support portion 112f that forms a helical flange is attached to the inner upper portion 112d and extends outward. The column support portion 112f of the rotor 112 will be described in more detail below.

[0025] A power source including a suitable control panel 126 and forming a motor 124 selectively rotates the rotor 112 via a pair of interconnected gear wheels 128, 130 that are respectively attached to the outer lower portion 112b of the motor 124 and the rotor 112. The motor 124 is supported by a bracket 132 fixed to the base plate 116.

[0026] The linear actuator 110 includes a retractable column 133 formed of a first band 134 that detachably connects consecutive turns of a second band 138 and is used to transmit a load (object) from one turn of the second band 138 to the next turn, and the second band forms the wall of the column 133.

[0027] The first band 134 has a housed state portion 134a that is helically laminated and housed in a first band magazine 136 formed in the rotor 112. More specifically, the first band magazine 136 is a space located above the base plate 116, below the rotor horizontal portion 112c, and between the two rotor lower portions 112a, 112b.

[0028] Similarly, the second band 138 also has a housed state portion 138a that is spirally stacked and housed in a second band magazine 140 formed within the rotor 112. More specifically, the second band magazine 140 is disposed radially outward of the upper portion 112e on the outer side of the rotor and above the horizontal portion 112c of the rotor. The second band magazine 140 is further provided inside the above-described casing (not shown).

[0029] Both the first band magazine 136 and the second band magazine 140 are formed in a ring shape, and the second band magazine 140 is formed wider in the radial direction than the first band magazine 136.

[0030] As will be described in detail below, the first band 134 and the second band 138 each have respective column state portions 134b and 138b that are arranged to form a column 133. When the column 133 is gradually withdrawn or housed, the lengths of the first and second band column state portions 134b, 138b change in inverse proportion to the change in the lengths of their housed state portions 134a, 138a.

[0031] The upper ends of the respective bands 134, 138 are attached so as to be fixed to a load support member 142 that engages a load (not shown) that is raised and lowered by the linear actuator 110. A suitable attachment member (not shown) will attach the load support member 142 to the load.

[0032] The rotor 112 includes a second band guide member in the form of an insertion pad 148 for the second band that is supported radially inward by the upper portion 112e on the outer side of the rotor.

[0033] When the rotor 112 rotates to pull out or accommodate the column 133, each turn of the second band 138 is guided between the second band magazine 140 and the column 133 by the insertion pad 148 and is arranged in a spiral such that the upper edge of each successive turn overlaps the lower edge of the adjacent upper turn. At the same time, when the rotor 112 rotates, each turn of the first band 134 is guided between the first band magazine 136 and the column 133, where the teeth 150 arranged on the outer periphery of the first band 134 are connected to the openings 152, 154 (FIG. 5) arranged on the overlapping upper and lower edges of the second band 138, respectively, and detachably interlock two successive turns of each of the column state portions 138b of the second band 138. As a result, the wall of the column 133 is formed by the column state portion 138b of the second band 138, while the teeth 150 of the first band 134 cooperate with the openings 152, 154 of the second band 138 to interlock successive turns of the column state portion 138b of the second band 138 and transmit the load (object) between each of the successive turns of the second band 138. When the column 133 is pulled out, the first band 134 is guided from the magazine 136 to the column 133 by the engagement of its teeth 150 and the second band 138. That is, it is the second band 138 that pulls the first band 134.

[0034] The load displaced and supported by the linear actuator 110 is transmitted in order in a direction parallel to the vertical axis A to the load engagement member 142, then through each successive turn of the first and second band column state portions 134b, 138b of the first and second bands, and then to the rotor 112 (details will be described later). And finally, it is transmitted to the ground base 114 and the ground via the bearings 120, 122.

[0035] More specifically, as can be seen from FIG. 5, according to the present invention, the load (object) of the column, and importantly, the article (not shown) supported by column 133 and vertically displaced, is finally transmitted to rotor 112 by vertical band 138, as opposed to being transmitted to rotor 112 by the first band as in the case of the prior art apparatus shown in FIGS. 6-8. In fact, the vertical force F representing the load (object) of the column is transmitted from a certain turn of the second band 138' to the next 138'' via the corresponding turn of the first band 134', but the lowermost turn 138'' of the second band is directly disposed on the horizontal column support portion 112f of rotor 112, where the load of column 133 and the article supported thereby is transmitted to rotor 112.

[0036] There is a shear force induced at the turn of the column state portion 134b of the first band 134 caused by the transmission of the vertical force F from a certain turn to the next turn of the column state portion 138b of the second band 138, as in the prior art apparatus. However, this shear force is substantially equal at all turns of the column state portion 134b of the horizontal band 134.

[0037] The first band 134 also abuts against the inner side in the radial direction with respect to the outer surface of the rotor body 112d. In fact, when the insertion member 148 pulls out column 133, it is used as a horizontal guide member for pushing the second band 138 from its accommodation state portion 138a into column 133, and the upper vertical portion 112d of the rotor is used as a reaction member that counteracts the horizontal pressure H1 of the insertion member against column 133 with H2. Note that instead, a reaction force member is applied with a horizontal pressure against the second band 138.

[0038] The rotor 112 is shown to include a helical groove 160 that engages a first band. Since the support of the load of the column 133 is not achieved via the first band 134 disposed on the rotor 112 as in the prior art, this helical groove can be of any configuration. By providing the helical groove 160, it is possible to prevent the first band from accidentally detaching from the base 114, thereby stabilizing the column 133. In fact, when the load supported by the column 133 and vertically displaced is accidentally pulled, or when the load accidentally tilts laterally and forcibly bends the column 133, engaging the first band 134 in the groove 160 will help prevent undesirable situations such as the disassembly or crushing of the column 133.

[0039] One of the characteristic advantages of the present invention is that, as a result, by moving the load supported by the column 133 and vertically displaced directly from the second vertical band 138 to the rotor 112, the local cantilever force provided in the prior art devices (as shown in FIGS. 6 - 8, etc.) does not exist at all in the single rotor support turn of the columnar state portion 134b of the first band 134 in the embodiments of the present invention. Thereby, the first band 134 does not receive corresponding fatiguing forces when the column 133 repeatedly appears and disappears as in the prior art, and the column 133 can be designed and constructed with a first band 134 having low structural resistance, leading to cost reduction. Considering that the load supported by a linear actuator such as the linear actuator 110 of the present invention and vertically displaced can be thousands of kilograms in weight, it is important that many components including the horizontal band 134 need to be constructed with strict mechanical requirements. As improved in the present invention, significantly relaxing these requirements leads to significant cost reduction.

[0040] The second band 138, which is used to support the load (object) supported by the column 133 and displaced, does not experience the same fatigue as the horizontal first band in the prior art device. In fact, the load (object) is transmitted through the vertical band 138 as follows. a) It is in a substantially vertical direction, that is, a direction substantially along the cross-section of the second band. This direction, of course, provides a much greater resistance compared to the resistance applied laterally as in the case of the horizontal first band of the prior art. b) It is applied approximately evenly to all turns of the second band including the lowermost turn transmitted to the rotor 112.

[0041] This is different from the prior art where the load (object) is ultimately transmitted from the first band to the rotor, and the load (object) is transmitted from the turns (or a small number of turns) of the first band to the rotor (a) laterally with respect to the cross-section of the first band, and (b) the turns (or a small number of turns) arranged on the rotor receive a cantilever force as described with reference to FIG. 8, and thus are transmitted unevenly in all turns.

[0042] A further advantage of having the configuration according to the present invention shown in FIGS. 1 to 5 is that by supporting the load on the column 133 only on the lowermost turn of the column-like portion 138b of the second band 138, it is not necessary to engage three turns of the first band with the rotor as in the prior art. Only two turns of the first band 134 can engage with the rotor. Refer to FIGS. 8 and 5. In this way, the entire rotor 112 and base 114 can be made more compact, which is a great advantage because the clearance required for installing the linear actuator 110 below the load object that displaces vertically becomes smaller.

[0043] The present invention broadly relates to a linear actuator including upper and lower frame portions movable relative to each other perpendicular to a vertical central axis A. In the illustrated embodiment, the lower frame portion comprises a base 114 and the upper frame portion comprises a load support member 142. Any suitable actuating mechanism that enables relative movement of the two frame portions may be used, including a motor as shown in the figures.

[0044] In one embodiment (not shown), the actuating mechanism may be provided on the upper frame portion rather than the lower frame portion (see, for example, the embodiments shown in FIGS. 9 and 9A of U.S. Patent No. 7,213,796 issued to the applicant).

[0045] The second band guide member may be provided on either the upper frame portion or the lower frame portion, i.e., the frame portion opposite the frame portion on which the actuating mechanism is disposed.

[0046] In one embodiment, the horizontal guide member that guides the vertical band between its housed state portion and its column state portion is fixed, and instead the first and second bands rotate to selectively extend and house the column. That is, it is the rotation of the horizontal guide member relative to the first and second bands that enables the telescoping of the column, although one or both of these elements may rotate relative to the base.

[0047] In one embodiment (not shown), teeth are not provided and the second band is disposed in the center of the first band.

Claims

1. A linear actuator, comprising: an upper frame portion and a lower frame portion configured to be movable relative to each other in a vertical direction along a central axis; an elongated first band wound in a helical manner around the central axis; an elongated substantially flat second band having turns wound so as to overlap each other, the turns being wound around an axis substantially parallel to the central axis in a substantially lateral direction with respect to the central axis; the first band including a housed state portion separated from the second band and a column state portion engaged with the second band; the second band including a housed state portion in which each turn is in a nested state with each other and the turns form a helix centered on the central axis at an equal distance from the central axis in a radial direction, and a column state portion that forms a wall of a vertical column by engaging with the column state portion of the first band; each column state portion of the first band and the second band having an end attached to one of the upper frame portion and the lower frame portion; the linear actuator further comprising: a horizontal guide member supported by the other of the upper frame portion and the lower frame portion, different from the one to which the ends of the column state portions of the first band and the second band are attached, and guiding the turns of the second band horizontally between the housed state portion and the column state portion; a second band load support member supported by one of the upper frame portion and the lower frame portion, vertically engaging with the column state portion of the second band to vertically displace a load applied to the column, and vertically supporting the load from the column state portion of the second band; a power source supported by one of the upper frame portion and the lower frame portion, causing relative rotation between the horizontal guide member, the first band, and the second band, and selectively causing the column to protrude and retract.

2. The linear actuator according to claim 1, wherein: The ends of the column-shaped portions of the first band and the second band are attached to the upper frame portion. The first band and the second band do not rotate with respect to the upper frame portion and the lower frame portion. The horizontal guide member is rotatably supported by the lower frame portion. The power source is a linear actuator supported by the lower frame portion for rotating the horizontal guide member about the central axis.

3. The linear actuator according to claim 2, wherein the second band load support member is a linear actuator rotatably supported by the lower frame portion.

4. The linear actuator according to claim 3, which is configured such that the turn of the column-shaped portion of the second band closest to the lower frame portion engages with the second band load support member.

5. The linear actuator according to claim 4, wherein the horizontal guide member includes an insertion member for forcibly inserting the second band from the housing state portion into the column when the column is pulled out, and a reaction force member for countering the horizontal pressing force of the insertion member against the column.

6. The linear actuator according to claim 5, wherein the insertion member, the reaction force member, and the second band load support member are supported by a rotor rotatably supported by the lower frame portion.

7. The linear actuator according to claim 6, wherein the insertion member is an insertion pad supported at a distance outside the reaction force member by the rotor, and the first band abuts horizontally against the reaction force member to counter the horizontal force of the insertion pad against the second band.

8. The linear actuator according to claim 6, wherein the second band load support member is a flange provided on the rotor protruding in a direction radially away from the central axis.

9. The linear actuator according to claim 6, The rotor is a linear actuator that includes a helical groove that engages with the first band to stabilize the column by preventing the first band from moving away from the lower frame portion. **Claim 10** The linear actuator according to claim 6, wherein the first band includes a number of teeth extending radially away from the central axis, and the teeth engage with openings provided at overlapping upper and lower edges of the second band in the columnar state portion of the first and second bands, and are detachably connected to the columnar state portion of the first band in successive turns of the columnar state portion of the second band.

Images