JP2002302388A - Motor-driven table lift device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability of a table lift device by uniformly applying a load to a plurality of screw shafts even when an unbalanced load is applied to a table because of deteriorating the durability of the table lift device as a result of shortening the service life due to the application of a large load to a large load side screw shaft in a motor-driven table lift device using a motor-driven cylinder though there is no problem when using a hydraulic cylinder for a driving source for extending and contracting a lift arm when the unbalanced load is applied to the table in a table lift for lifting the table in parallel to a base by vertically extending and contracting the X-shaped lift arm. SOLUTION: The motor-driven cylinder 30 is interposed between a second rotary member 35 rotatable via the second rotary axis 37 in a first rotary member 21 for connecting a pair of left and right inner arms 10Ui and 20Ui and a third rotary member 36 rotatable via the fifth rotary axis in a fourth rotary member 38 arranged between inner arms 10Di and 20Di.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric table lift device for moving a table up and down in parallel using an electric motor and an electric cylinder mainly comprising a screw shaft device as a drive source.

[0002]

2. Description of the Related Art Conventionally, an X-shaped lift arm in which an inner arm and an outer arm are rotatably connected to each other is interposed between a table and a base, and a lift arm between the inner arm and the outer arm (or one of them) is provided. A table lift device that interposes a hydraulic cylinder between an arm and a base) and expands and contracts the hydraulic cylinder to vertically expand and contract a lift arm, thereby moving the table up and down in parallel with the base. When a heavy load is applied to the table, a table lift device for heavy load using two hydraulic cylinders as driving sources is provided. Further, as disclosed in, for example, Japanese Patent No. 2591598, an electric cylinder mainly including a screw shaft device having an electric motor, a screw shaft and a nut meshing with the screw shaft is used as a drive source instead of the hydraulic cylinder. An electric table lift device is provided.

[0003]

However, in the conventional electric table lift apparatus, only a low load apparatus using an electric cylinder having a single screw shaft as a drive source has been provided. Therefore, this electric table lift device can also be used for heavy loads by using, for example, an electric cylinder having two screw shafts as a drive source like the hydraulic cylinder type table lift device. However, when an electric cylinder having a plurality of screw shafts is used as a drive source, there are the following problems. That is, if the load is not equally applied to the two left and right screw shafts due to, for example, an unbalanced load applied to the table, the fatigue life of the left and right screw shafts will not be uniform, and as a result, the durability of the table lift device will be reduced. There was a problem that the property was reduced. Further, when a bending moment is applied to the screw shaft due to the uneven load or the like, the screw shaft and nuts meshing with the screw shaft (balls interposed between the screw shaft) are unevenly worn. And the durability of the table lift device is reduced.

[0004] When two hydraulic cylinders are used as driving sources, the two hydraulic cylinders are bent independently of each other because they operate independently of each other in accordance with the unbalanced load applied to the table. Although no moment is applied, the electric cylinder is configured to use the movement of the nut on the screw shaft as a stroke, and this stroke is obtained only when the electric motor is started and the screw shaft is rotating. Due to the configuration, they do not operate independently of each other according to the offset load of the table as in the case of the hydraulic cylinder, and as a result, when the offset load is applied to the table, the two screw shafts are different from each other A large compressive load is applied, which results in a bending moment being applied to both screw shafts. The present invention has been made in order to solve these problems, and is a table lift device that uses an electric cylinder having a plurality of screw shafts as a drive source, in which an eccentric load or the like is applied to a table. It is therefore an object of the present invention to provide an electric table lift device in which a load is evenly applied to each screw shaft and a bending moment is not applied to each screw shaft, and as a result, it has high durability. .

[0005]

Therefore, the present invention provides an electric table lift apparatus having the structure described in each of the above claims. According to the electric table lift device of the first aspect, the nut moves on the screw shaft by the operation of the electric cylinder, whereby the lift arm expands and contracts up and down, and the table moves up and down. The plurality of nuts engaged with each of the plurality of screw shafts move at the same speed in the same direction, whereby the table moves up and down in parallel with the base. When the table is loaded with an eccentric load, one of the left and right lift arms is loaded with a greater load than the other, and thus one end of the first rotating member is loaded with a greater vertical external force than the other end. You. However, the second rotating member connected to the first rotating member is rotatably connected around a second rotation axis passing through an intermediate fulcrum of the first rotating member.
Since the plurality of nuts are rotatably connected via the third rotation axis at positions symmetrical with respect to the second rotation axis of the second rotation member, the unbalanced load applied to the first rotation member is equal to the second rotation axis. It is evenly and vertically added to the plurality of nuts via the second rotation axis and the third rotation axis. The plurality of screw shafts meshed with the respective nuts are supported in parallel with each other along the vertical direction.

For this reason, even when the table is loaded with an eccentric load, each screw shaft is subjected to only a compressive load that is even and mutually vertical, so that the fatigue life of each screw shaft is reduced. As a result, the durability (life) of the electric table lift device can be improved, and since no bending moment is applied to each screw shaft, uneven wear of the screw shaft and the nut can be suppressed. Also in this respect, the fatigue life of the screw shaft and the nut can be increased, and the durability of the table lift device can be increased. According to the table lift device of the second aspect, since both ends (the nut side and the screw shaft side) of the electric cylinder are rotatably supported, it is possible to more reliably prevent the bending moment from being applied to the screw shaft. .

[0007]

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows a table lift device 1 of the present embodiment. The table lift device 1 includes a base 2, a table 3 that moves up and down in parallel with the base 2, a pair of left and right lift arms 10 and 20 between the table 3 and the base 2, Lift arms 10, 2
There is provided an electric cylinder 30 for vertically extending and retracting the zero. Hereinafter, the left lift arm 10 in FIG.
Is referred to as “left lift arm 10”, the right lift arm 20 is referred to as “right lift arm 20”, and the two are distinguished as necessary. The left and right lift arms 10 and 20 are respectively an upper left lift arm 10U and an upper right lift arm 20
U, lower left lift arm 10D, lower right lift arm 20D
Are connected in two upper and lower stages. These four sets of lift arms 10U, 20U, 10D, 20D
Have an X-shape in which an inner arm and an outer arm are rotatably connected to each other. In the following description, the reference numerals of the lift arms 10U, 20U, 10D, and 20D are denoted by a suffix “i” to indicate the corresponding inner arm of the lift arm, and the suffix “o” is denoted by the outer arm of the corresponding lift arm. Is shown. Further, the support shaft that connects the inner arm and the outer arm so as to be rotatable with each other uses a reference numeral with a suffix “c” added to the reference numeral of the corresponding lift arm.

One end (left end in FIG. 1) of the inner arms 10Di, 20Di of the left and right lower lift arms 10D, 20D is turned up and down via support portions 11, 11 provided at the rear end of the base 2. Supported as possible. Note that the support portion 11 that pivotally supports one end of the inner arm 20Di is not visible in the drawing. Both inner arms 10Di, 20
The rotation supporting portion side of Di is integrally connected to each other via a connection shaft 13, and the rotation tip side is also integrally connected to each other via a connection bar 12, whereby both inner arms 10Di and 20Di are provided. Rotates up and down as a unit. The distal ends of the inner arms 10Di and 20Di are connected to the connecting shaft 1.
4, the upper link arms 10U and 20U are rotatably connected to one ends of inner arms 10Ui and 20Ui. The outer arms 10Do and 20Do of the lower lift arms 10D and 20D have their distal ends connected integrally via a single connection shaft 15. Connecting shaft 15
Rollers 15a, 15a are attached to both ends of the outer arm 10Do, and the outer arms 10Do, 20Do tilt up and down while rolling the rollers 15a, 15a onto the base 2. The rear ends of both outer arms 10Do, 20Do are connected to the upper lift arms 10U,
The outer arms 10Uo, 20Uo of 20U are rotatably connected to rear ends thereof.

The distal ends of the outer arms 10Uo, 20Uo of the upper lift arms 10U, 20U are mutually connected by a connecting shaft 17. Rollers 17a, 17a are rotatably attached to both ends of the connecting shaft 17, and the outer arms are rotated while rolling the rollers 17a, 17a along rails 3a, 3a provided on the lower surface of the table 3. 10Uo and 20Uo tilt up and down. Both inner arms 10U of upper lift arms 10U and 20U
The rear end side of i, 20Ui is supported so as to be able to tilt up and down via supporting portions 18 provided on the lower surface on the rear end side of the table 3. The inner arms 10Ui and 20Ui are integrally connected via a connecting bar 19.

Next, the distal ends of the inner arms 10Ui, 20Ui of the upper lift arms 10U, 20U are connected to the connecting bar 2A.
2 are integrally connected. In FIG. 1, the upper first rotating member 21 has a rectangular cross section, and support pin portions 21a, 21a having circular cross sections are provided at both ends. The first support pin portions 21a, 21a
The rotating member 21 is supported between the inner arms 10Ui and 20Ui so as to be rotatable around the axis (first rotation axis) of the support pin portions 21a and 21a. The first rotating member 21 corresponds to the first rotating member described in the claims. An electric cylinder 30 is mounted between the first rotating member 21 and the connection shaft 13.
The electric cylinder 30 has one electric motor 31 as a drive source, two screw shafts 32, 32 rotated by the electric motor 31, and both screw shafts 32, 32 via a number of steel balls. The nuts 33, 33 engaged with each other;
A second rotating member 35 supporting the nuts 33, 33,
A third rotating member 36 that rotatably supports both screw shafts 32, 32 is provided.

First, the second rotating member 35 is rotatably connected to the first rotating member 21 via a connecting shaft 37. The connection shaft 37 is located at an intermediate fulcrum of the first rotating member 21 (an intermediate position between the left inner arm 10Ui and the right inner arm 10Uo). The axis of the connection shaft 37 is orthogonal to the first rotation axis, which corresponds to the second rotation axis described in the claims. The second rotating member 35 is rotatably connected via the connecting shaft 37 so as to sandwich the first rotating member 21 from front and rear. On the other hand, a fourth rotating member 38 is attached to the center of the connecting shaft 13 so as to be rotatable around the connecting shaft 13 and not to move in the axial direction. This fourth rotating member 38 has a connecting shaft 3
The third rotation member 36 is rotatably connected to the third rotation member 36 via the first rotation member 9. The rotation axis of the connection shaft 13 corresponds to the fourth rotation axis described in the claims, and the axis of the connection shaft 39 corresponds to the fifth rotation axis. The rotation axis of the connection shaft 13 is
The fifth rotation axis is parallel to the rotation axis.
The axes of rotation are orthogonal. For this reason, the third rotating member 36
Is provided so as to be tiltable up and down around a fourth rotation axis, and also to be tiltable left and right around a fifth rotation axis.

Next, the electric motor 31 is connected to the third rotating member 36.
Attached to. The output shaft of the electric motor 31 and the lower ends of the two screw shafts 32, 32 are connected by a driving force transmission mechanism 34 mainly composed of a sprocket and a chain. The two screw shafts 32, 32 are respectively
It is rotatably supported at both ends of the third rotating member 36 via 0-40. The two screw shafts 32 are supported in parallel with each other along the vertical direction. The nuts 33, 33 meshed with the two screw shafts 32, 32
Each has a nut main body 33a and a sleeve 33b attached to the upper end thereof. The nut body 33a is engaged with the screw shaft 32. When the nut main body 33a moves by the rotation of the screw shaft 32, the sleeve 33b also moves integrally. The upper ends of both sleeves 33b, 33b are rotatably connected to both ends of the second rotating member 35 via connecting shafts 41, respectively. At both ends of the second rotation member 35, connection holes 35a, 35a in the shape of long slots are formed vertically, and the connection shaft 41 is inserted into the connection hole 35a so as to be rotatable and vertically movable. . When the connecting shaft 41 moves in the connecting hole 35a, the two screw shafts 32,
The rotation of the second rotating member 35 with respect to the first rotating member 21 is allowed while maintaining the state in which the second rotating member 32 extends along the vertical direction. The axis of both connecting shafts 41, 41 corresponds to the third rotation axis described in the claims. Both connecting shafts 41, 41
It is arranged at a position symmetrical with respect to the connecting shaft 37.
Bellows 42 are attached between the sleeves 33b, 33b of the nuts 33, 33 and the third rotating member 36, respectively.
The exposed portions 2 and 32 and the nut bodies 33a and 33a are shielded from the outside to prevent dust.

According to the table lift device 1 of the present embodiment constructed as described above, when the electric motor 31 is started, the two screw shafts 32 rotate at the same rotational speed in the same direction via the driving force transmitting mechanism 34. As a result, the nut 33 moves in the same direction at the same speed. Both nuts 33, 33
Is upward in the figure (in a direction away from the third rotating member 36).
, The distance between the first rotating member 21 and the connection shaft 13 becomes large, so that the left and right and up and down lift arms 10D,
20D, 10U, and 20U extend upward, respectively, whereby the table 3 is raised parallel to the base 2. In addition, the operation in which the inner arm and the outer arm of each of the lift arms 10D, 20D, 10U, and 20U are tilted in the rising direction and become longer vertically is performed by each of the lift arms 10D, 2U.
0D, 10U, and 20U extension operations. Conversely, the operation in which the inner arm and the outer arm are tilted in the falling direction and shortened up and down is defined as each of the lift arms 10D, 20D, 10U,
It is called a 20U reduction operation. When the electric motor 31 stops and the built-in brake operates, the left and right lift arms 1
The extension operation of 0, 20 is stopped, whereby the table 3 is locked at an arbitrary position. When the brake of the electric motor 31 is released from the stopped state of the table 3 at the raised position, the left and right lift arms 10 and 20 contract downward due to the weight of the table 3 and the person or luggage placed on the table 3. Thereby, the table 3 and the person or luggage placed on the table 3 descend.

The person loaded on the table 3 or the loaded luggage is not located at the center of the table 3 but is loaded on the table 3 because it is loaded on the right side of the table 3 in FIG. When the load is an uneven load, as shown in FIG. 3, a load F1 applied to one end of the first rotating member 21 via one upper lift arm 20U.
Is connected to the first rotating member 2 via the other upper lift arm 10U.
1 becomes larger than the load F2 applied to the other end side. In FIG. 3, in order to clearly show a state in which a load F1 greater than the other end is applied to one end of the first rotating member 21, one end is lower than the other end so that the first rotating member 21 Is shown in an inclined state. However, the connecting shaft 37 for rotatably supporting the second rotating member 35 on the first rotating member 21 is located at an intermediate position L1 between the inner arms 10Ui of the left and right lift arms 10, 20 and the inner arm 20Ui. In addition, the connecting shaft 41 and the connecting shaft 41
41 is located. For this reason, the unbalanced load (F1 + F2) applied to the table 3 is applied to both nuts 33, 33 via both connecting shafts 41, 41, and a load F3 (= (F1 + F2) / 2) along the axial direction of the screw shaft 32. Are equally loaded.

An eccentric load (F) applied to the table 3
1 + F2) is also applied to the connecting shaft 13 via both inner arms 10Di and 20Di of the lower lift arms 10D and 20D. That is, a larger load F1 (> F2) is applied to one end of the connecting shaft 13 than to the other end. However, the connecting shaft 39 that rotatably supports the third rotating member 36 with respect to the fourth rotating member 38 has two inner arms 10Di,
It is located at a position equidistant L2 from 20Di. Also,
The two screw shafts 32 are arranged at positions symmetrical with respect to the connection shaft 39 (positions at equal intervals L4) in parallel with each other. For this reason, a load F3 (= (F1 + F2) / 2) along the axial direction is evenly applied to both screw shafts 32, 32, respectively. Thus, the eccentric load (F
1 + F2), the load (F1 + F2) / in the axial direction is applied to both screw shafts 32, 32 and both nuts 33, 33.
2 are evenly loaded, so that their fatigue life can be made uniform, whereby the durability of the electric cylinder 30 and thus the lift device 1 can be improved.

The transmission cylinder 30 of the present embodiment is
The first rotating member 21 is connected via a connecting shaft 37 (second rotating axis).
, And rotatably connected to the fourth rotating member 13 via the connecting shaft 39 (fifth rotating axis).
2, 32 and the nuts 33, 33 do not receive bending moments. For this reason, uneven wear of the screw shafts 32, 32 and the nuts 33, 33 and the like is suppressed, so that the durability of the electric cylinder 30 and thus the lift device 1 can be improved.

Here, the life of the screw shaft can be calculated by the following formula (JIS B1518 "Method of calculating dynamic load rating and rated life of rolling bearing"). L = (Ca / Fa) ³ × 10 ⁶ L: Rated fatigue life (rev) Ca: Basic dynamic load rating of screw shaft (N) Fa: Axial load (N) The life of the screw shaft when the load is applied is determined when the load is not evenly applied to the two screw shafts (i) and when the load is applied evenly (i
Think separately in i). For example, Ca = 5460 (N),
Assume that F1 = 4000 (N) and F2 = 1000 (N). (I) When one screw shaft is loaded with F1 and the other screw shaft is loaded with F2 For one screw shaft, L = (5460/4000) ³ × 10 ⁶ = 2.54 × 10
⁶ (rev) About the other screw shaft L = (5460/1000) ³ × 10 ⁶ = 1.63 × 10
⁸ (rev) In this case, if one of the screw shafts rotates 2.54 × 10 ⁶ , flaking or the like occurs and the screw shaft is broken. Therefore, the life of the electric cylinder is determined by the life of the one screw shaft. (Ii) When F1 and F2 are equally applied to two screw shafts (in the case of the present embodiment) Load F3 = (F1 + F2) / 2 = 2500 on each screw shaft
(N) are equally loaded. L = (5460/2500) ³ × 10 ⁶ = 1.04 × 10
⁷ (rev) Therefore, in this case, the life of both screw shafts is 1.04 × 10
^{This is seven} rotations, and the durability of the electric cylinder 1 can be greatly improved as compared with the case (i).

Various modifications can be made to the embodiment described above. For example, one electric motor 31 and 2
Although the electric cylinder 30 having the screw shafts 32, 32 has been exemplified, the present invention can be similarly applied to an electric cylinder having one electric motor for one screw shaft, thereby obtaining the same operation and effect as described above. Can be. Also, screw shaft 3
A third rotating member 36 for rotatably supporting the connecting shafts 2 and 32
Although the configuration in which the base 2 side of the electric cylinder 30 is rotatably supported by the fourth rotary member 38 via the rotary shaft 9 and the base 2 side of the electric cylinder 30 is rotatable, the connection shaft 39 is eliminated and the third rotation The member 36 may be fixed to the fourth rotating member 38 so as to be rotatable only around the fourth rotation axis, so that only the table 3 side of the electric cylinder 30 may be rotatable. Even in this case, when an eccentric load is applied to the table 3, the load F3 can be uniformly applied to the screw shaft, and only the axial force is applied to the screw shaft to apply the bending moment. Can be prevented from
It is possible to reduce uneven wear of the screw shaft and the nut as compared with the related art, and to improve the durability of the electric cylinder.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, and is a side view of a table lift device. This figure shows (1) in FIG.
It is the figure which looked at-(1) line cross section in the direction of an arrow.

FIG. 2 is a front view of the table lift device. This figure is
FIG. 2 is a diagram viewed from a direction of an arrow (2) in FIG. 1.

FIG. 3 is a diagram schematically showing a state where a load is transmitted to an electric cylinder when an unbalanced load is applied to a table.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Table lift apparatus 2 ... Base 3 ... Table 10 ... Left lift arm 10U ... Upper left lift arm 10Ui ... Inner arm, 10Uo ... Outer arm 10D ... Lower left lift arm 10Di ... Inner arm, 10Do ... Outer arm 13 ... Connecting member ( 20 ... Right lift arm 20U ... Upper right lift arm 20Ui ... Inner arm, 20Uo ... Outer arm 20D ... Lower right lift arm 20Di ... Inner arm, 20Do ... Outer arm 21 ... First rotating member, 21a ... First Rotation axis 30 ... Electric cylinder 31 ... Electric motor 32 ... Screw shaft 33 ... Nut 35 ... Second rotation member 36 ... Third rotation member 37 ... Connection shaft (second rotation axis) 38 ... Fourth rotation member 39 ... Connection shaft ( Fifth rotation axis) 41: Connecting shaft (third rotation axis) L1 Connecting shaft 37 (second rotation axis) and inner arm 1
0Ui and the distance between the inner arm 20Ui and L2: the connection shaft 37 (second rotation axis) and the connection shaft 41 (third rotation axis).
Interval L3: connecting shaft 39 (fifth rotation axis) and inner arm 2
0Di and the distance between the inner arm 20Di L4: the distance between the connecting shaft 39 (the fifth rotation axis) and the screw shaft F1, F2: the load applied to the table F3: the uniform load applied to the screw shaft

Claims (2)

[Claims] 1. An X-shaped lift arm in which a pair of inner arms and an outer arm are rotatably connected to each other between a base and a table, and a pair of left and right X-shaped lift arms is interposed between the inner arm and the outer arm. An electric motor and an electric cylinder having a plurality of screw shafts rotated by the electric motor and a plurality of nuts meshing with the respective screw shafts are interposed therebetween, and the lift arm is extended and contracted by the operation of the electric cylinder, so that the table is extended. A motor-driven table lift device for raising and lowering in parallel with respect to the base, wherein the electric cylinder is provided between one of the left and right lift arms so as to be rotatable around a first rotation axis. Via a rotating member and a second rotating member rotatably connected about a second rotation axis passing through an intermediate fulcrum of the first rotation member and orthogonal to the first rotation axis. Each nut of the electric cylinder is connected between the left and right lift arms, and each nut of the electric cylinder is parallel to the second rotation axis and passes through the third rotation axis passing through a symmetric position with respect to the second rotation axis. A third rotating member rotatably connected to a rotating member, wherein the plurality of screw shafts are rotatably provided between the other of the two lift arms around a fourth rotating axis parallel to the first rotating axis; An electric table lift device supported rotatably in parallel with each other. 2. The table lift device according to claim 1, wherein the third rotating member is provided on a fourth rotating member rotatably provided around a fourth rotating axis, the fifth rotating member being parallel to the second rotating axis. An electric table lift device rotatably connected via an axis.