JP2024000564A - Electric elevating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric elevating device capable of reducing lateral load generated during elevating operations.

SOLUTION: An electric elevating device 1 comprises an electric motor 6, a rotating arm 30 that rotates around the axis of a rotational driving shaft 9 of the electric motor 6, an elevating member 5 that is supported by a guide rod 26 extending vertically and goes up and down, and a link member 35 that has one end rotatably connected to the rotating arm 30 and the other end rotatably connected to the elevating member 5, and elevates the elevating member 5 with a predetermined stroke. The center 9a of the rotational driving shaft 9 is disposed at a position on the opposite side across a virtual vertical line 41 passing through the connection center 38a between the elevating member 5 and the link member 35 when seen from a tip 32 of the rotating arm 30 when the rotating arm 30 is rotated to a horizontal position.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to an electric lifting device that moves objects to be transported in the vertical direction.

As an electric lifting device using an electric motor, one is known that uses a crank mechanism to move an lifting member in the vertical direction with a constant stroke (for example, see Patent Document 1 below). Such a lifting device aligns the center of gravity of the lifting member with the center position of the rotational drive shaft of the electric motor, and also rotates the rotating arm that rotates in one direction around the axis of the rotational drive shaft of the electric motor to reach the rising end. Generally, it stops at the top dead center (top dead center) and the bottom dead center (bottom dead center). In addition, the height of the elevating member can be maintained even when the elevating member is stopped at an intermediate position between the ascending end and the descending end, and the rotary arm is prevented from rotating due to external force at the ascending end position. Generally, electric motors are equipped with a brake device.

In such a lifting device, when the lifting member is at the rising end, the rotating arm stands vertically with the center of rotation facing downward, and even if the weight of the lifting member is applied at the top dead center position, the rotating arm does not move. This is an excellent method that allows accurate height positioning without applying a large load to the brake device attached to the drive motor as no rotational force is applied.

JP2020-37482A

However, in a lifting device using a crank mechanism, when the rotating arm is rotated during lifting and lowering operations, the rod-shaped link interposed between the lifting member and the rotating arm extends vertically as the rotating arm turns sideways. This state changes to an obliquely inclined state, and a lateral load is generated due to this inclination. For example, when this lateral load acts on a guide portion for preventing rolling, the guide portion is required to have strength that takes the lateral load into consideration. Further, if the lifting device has a structure in which the lifting member is supported by a guide rod extending in the vertical direction, the lateral load acts on the guide rod extending upward, so that a bending moment is applied to the guide rod. For this reason, guide rods are required to have strength and wear countermeasures that take into account bending moments.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide an electric lifting device that can reduce the lateral load generated during lifting and lowering operations.

The present inventors have made extensive studies to solve the above problems, and as a result, have come up with the present invention as described below.
The electric lifting device according to the first aspect of the present invention is defined as follows. That is,
electric motor and
a rotating arm that rotates around the axis of a rotational drive shaft of the electric motor;
an elevating member that is supported by a guide rod extending in the vertical direction and moves up and down;
a link member having one end rotatably connected to the rotary arm and the other end rotatably connected to the elevating member;
An electric lifting device that lifts and lowers the lifting member at a predetermined stroke,
The center of the rotational drive shaft is located on the opposite side across an imaginary vertical line passing through the center of connection between the elevating member and the link member, when viewed from the tip of the rotary arm when the rotary arm is rotated to a horizontal position. placed in position.

According to the electric lifting device of the first aspect defined in this way, the inclination of the link member when the rotating arm is horizontal is suppressed, so that the lateral load generated due to the inclination of the link member is suppressed. can be made smaller. This makes it possible to reduce the strength of the parts that receive lateral loads, thereby reducing costs.

The second aspect of the invention is defined as follows. That is,
In the electric lifting device specified in the first aspect, the guide rod is fitted onto a portion of the guide rod below the upper end connected to the lifting member, and the inner circumferential surface thereof is extended over a predetermined length in the vertical direction. The apparatus further includes a guide rod holding member that faces the outer circumferential surface of the guide rod.

According to the second aspect of the electric lifting device stipulated in this way, the guide rod holding member reduces the lateral load that acts on the guide rod during lifting and at the end of the lifting when the guide rod is extended. The bending moment applied to the can be reduced. This reduces the strength of the guide rod, reduces wear on the sliding parts, and reduces costs.

The third aspect of the invention is defined as follows. That is,
In the electric lifting device specified in the first aspect or the second aspect, the guide rod occurs when a line segment connecting the center of connection of the rotary arm with the link member and the center of the rotary drive shaft is horizontal. The distance between the virtual vertical line and the center of the rotational drive shaft is determined so that the bending moment of the guide rod is approximately equal to the bending moment of the guide rod that occurs when the line segment is vertical.

As the distance between the virtual vertical line and the center of the rotary drive shaft increases, the bending moment of the guide rod that occurs when the line segment connecting the center of connection with the link member in the rotary arm and the center of the rotary drive shaft is horizontal becomes smaller. However, when the line segment is vertical, the bending moment of the guide rod becomes large. According to the electric lifting device of the third aspect, the bending moment of the guide rod is averaged by determining the distance between the virtual vertical line and the center of the rotational drive shaft so that these two types of bending moments are approximately equal. The thickness of the guide rod can be set with minimal strength.

The fourth aspect of the invention is defined as follows. That is,
In the electric lifting device specified in the first aspect or the second aspect, in the lowering end position and the rising end position of the lifting member, the center of connection between the lifting member and the link member, the center of the rotational drive shaft, and , the rotary arm and the link member are configured so that their connection centers are on the same line.

According to the electric lifting device of the fourth aspect defined in this way, the external force that acts to rotate the rotating arm is not applied to the rotating arm or the rotational drive shaft at the lowering end position and the rising end position of the lifting member. can be prevented. This reduces the load on the brake attached to the electric motor and extends the life of the brake lining.

FIG. 1 is a longitudinal cross-sectional view of an electric lifting device according to an embodiment of the present invention. FIG. 2 is a longitudinal cross-sectional view of the electric lifting device shown from a different direction from FIG. 1; FIG. 2 is a sectional view taken along arrow III-III in FIG. 1; FIG. 2 is a diagram showing a state in which the rotary arm of the electric lifting device of FIG. 1 is rotated until it becomes horizontal. FIG. 2 is a diagram showing a state in which the rotary arm of the electric lifting device of FIG. 1 is further rotated until it is directed upward. FIG. 3 is a diagram illustrating the lateral load and bending moment generated in the electric lifting device of the same embodiment in comparison with the electric lifting device of the comparative example. This is a modification example in which the stopping position of the rotary arm at the descending end position is different. This is a modification example in which the stopping position of the rotary arm at the rising end position is different. FIG. 3 is a longitudinal cross-sectional view of an electric lifting device according to another embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings.

First, an electric lifting device 1 according to an embodiment of the present invention will be explained using FIGS. 1 to 6. The electric lifting device 1 includes a pedestal frame 4, a lifting member 5, an electric motor 6, a driving force transmission means 7, and a rolling prevention means 8, and is configured to move between a predetermined lowering end position and a rising end position. An elevating member 5 is configured to be movable up and down between the two.

The gantry frame 4 has a substantially rectangular shape and includes a lower frame 10, four columns 11 each extending upward from the lower frame 10, and an upper frame 12 coupled to the upper ends of the columns 11. Main constituent members of the electric lifting device 1 described below are attached to and supported by the lower frame 10 and the upper frame 12 of the gantry frame 4.

The elevating member 5 is a member that moves up and down above the upper frame 12 of the gantry frame 4 . A conveyed object W can be held on the elevating member 5, and the conveyed object W can be delivered to and from an adjacent conveyor device 15 as needed.
The elevating member 5 includes a base member 20, a pair of roller support members 21 that protrude upward from the upper surface of the base member 20, and a plurality of guide rollers 22 that are provided inside the pair of roller support members 21 to face each other. As shown in FIGS. 1 and 2, the conveyed object W is held by guide rollers 22.

The base member 20 of the elevating member 5 has a substantially rectangular plate shape in plan view, and as shown in FIG. The member 5 is configured to be vertically movable together with the guide rod 26.

In this embodiment, as shown in FIG. 1, a two-stage conveyor device 15 is provided adjacent to the electric lifting device 1, and the lifting member 5 is located at its lowering end position (the lifting member shown in FIG. 1). 5), the height of the pass line is the same as the lower conveyor 16B of the conveyor device 15, and at the rising end position (the position of the lifting member 5 shown in FIG. 5), the height of the pass line is the same as the upper conveyor 16A. It will be the same. This makes it possible to transfer the conveyed object W to and from the conveyor 16A or 16B.

The driving force transmission means 7 includes a rotary arm 30, a first shaft pin 33, a link member 35, and a second shaft pin 38, and is configured to connect the electric motor 6 and the elevating member 5. The driving force of the electric motor 6 is transmitted to the elevating member 5 by being interposed therebetween.

The rotating arm 30 is a member in which two plate members 30a each having a generally elliptical shape in a plan view are joined together at a distance in the thickness direction. The rotary arm 30 is coupled to a rotary drive shaft 9, which is an output shaft of the electric motor 6, near one end in the longitudinal direction, and rotates integrally around the axis of the rotary drive shaft 9. Near the other end of the rotary arm 30 and at a distance R (see FIG. 4) from the rotation center 9a of the rotary arm 30, there is a first cylindrical column that straddles the two plates 30a, 30a. A shaft pin 33 is attached, and one end side of the link member 35 is rotatably connected via the first shaft pin 33.
Moreover, this has a structure of a both-end support beam in which both ends of the first shaft pin 33 are supported by two plate members 30a.

The link member 35 is a rod-shaped member having a rectangular cross section and extending in the vertical direction, and is bent into a dogleg shape at a predetermined length at the upper and lower parts. These doglegged bends are bent along the virtual plane in which the rotating arm 30 rotates.
These dogleg-shaped bends prevent the link member 35 from coming into contact with the rotary drive shaft 9 when the rotary arm 30 is suspended in the vertical direction.
In this embodiment, as described above, the structure has a support beam at both ends, and the rotating arm 30 and the link member 35 are configured to relatively rotate in forward and reverse directions within the same virtual plane. (See Figure 2). Therefore, the generation of bending moment at the first shaft pin 33 is suppressed compared to a cantilever structure in which one end of the connecting shaft is fixed to the rotary arm, as in the conventional rotary arm.
The other end of the link member 35 extends upward and is rotatably connected to the connecting piece 23 of the elevating member 5 via a cylindrical second shaft pin 38. Here, the connecting piece 23 of the elevating member 5 extends downward from the lower surface of the base member 20 at or near the center of gravity of the elevating member 5 .

In this embodiment, an electric motor with a brake is used as the electric motor 6. It is desirable that the brake torque here be about 1.5 times larger than the drive rotational torque generated by the electric motor during the lifting and lowering operations. The electric motor 6 rotates the rotary drive shaft 9 by 180° in a clockwise direction when raising the elevating member 5 from the lowering end position shown in FIG. 1 . Further, when lowering the elevating member 5 from the ascending end position shown in FIG. 5, the rotary drive shaft 9 is rotated 180° counterclockwise. Therefore, the operation of the electric motor 6 is controlled based on the rotation angle of the rotary drive shaft 9. The rotation angle can be detected, for example, by providing a rotation angle detector on the rotation drive shaft 9. It is also possible to provide a projection (detection section) at the tip of the rotary arm 30 and detect this using a proximity switch, a limit switch, or the like.

Here, in this embodiment, as shown in FIG. 1, when viewed from the direction along the axial direction of the rotary drive shaft 9, the center 9a of the rotary drive shaft 9 is located at the center 9a when the rotary arm 30 is rotated to the horizontal position. When viewed from the tip 32 of the rotary arm 30, it is disposed at a position on the opposite side across an imaginary vertical line 41 passing through the connection center 38a between the elevating member 5 and the link member 35. Specifically, the rotational drive shaft center 9a is located at a horizontal distance δ from the virtual vertical line 41 to the right in the figure. By doing this, the state in which the rotary arm 30 shown in FIG. In the horizontal state), the horizontal distance α between the two connection centers 33a and 38a provided at both ends of the link member 35 is shortened (by the amount by which the rotary drive shaft 9 is shifted by a distance δ to the right in the figure), Since the inclination θ of the link member 35 is suppressed, the lateral load generated due to the inclination of the link member 35 can be reduced.

However, when the horizontal distance δ is increased, the rotating arm 30 is vertically upward as shown in FIG. The bending moment of the guide rod 26 becomes large in a state in which the line segment connecting the two points is vertically upward. Therefore, in this embodiment, the horizontal distance δ is determined so that these two types of bending moments are approximately equal.
Here, the term "bending moment being approximately equal" refers to the bending moment of the guide rod 26 that occurs when the rotating arm 30 is rotated to a horizontal position, and the bending moment of the guide rod 26 that occurs when the rotating arm 30 is vertically upward. This means that the bending moment is within a range of, for example, 90% to 110% of the bending moment in the horizontal state.

The roll prevention means 8 is composed of a guide rod 26 and a guide rod holding member 50 that is fitted onto the guide rod 26.
The guide rod 26 is a cylindrical member extending in the vertical direction, and one end (upper end) thereof is coupled to the elevating member 5, so that the guide rod 26 is movable in the vertical direction together with the elevating member 5. When the elevating member 5 is at the lower end position, the lower end of the guide rod 26 is accommodated in the relief hole 27 formed in the lower frame 10, as shown in FIG. Interference with is avoided.

The guide rod holding member 50 is a substantially cylindrical member having a flange 51, and is attached to the upper frame 12 with the lower surface of the flange 51 in contact with the upper surface of the upper frame 12. The guide rod 26 is inserted through the inside of the holding member 50.

The guide rod holding member 50 is attached to the upper frame 12 and extends above the upper surface of the upper frame 12 and extends below the lower surface of the upper frame 12. The guide rod holding member 50 is configured such that the inner circumferential surface of the guide rod holding member 50 has a predetermined length in the vertical direction regardless of whether the guide rod 26 is at the lower end (see FIG. 1) or the upper end (see FIG. 5). The guide rod 26 faces the outer peripheral surface of the guide rod 26, and allows the guide rod 26 to move in the vertical direction, while restricting the lateral movement of the guide rod 26. In addition, the guide rod holding member 50 can reduce the lateral load that acts on the guide rod 26 during the ascent and descent and at the end of the ascent and descent, thereby reducing the bending moment applied to the guide rod 26, thereby reducing the strength of the guide rod 26. In addition to reducing wear on the sliding parts, it is possible to reduce costs.

Next, the elevating operation of the electric elevating device 1 will be explained.
As shown in FIG. 1, when the elevating member 5 is at the lower end position, the shaft pin 33 is located substantially directly below the rotational drive shaft 9 of the electric motor 6. From this state, when the electric motor 6 rotates the rotary arm in a clockwise rotation direction (normal rotation direction), the elevating member 5 rises via the driving force transmission means 7. The rotating arm 30 rotates from the sideways (horizontal) state shown in FIG. 4 to the upward state shown in FIG. The position of the elevating member 5 shown in FIG. 5 at this time is the ascending end position. The stroke from the lower end position to the upper end position is twice the distance R between the axes of the rotary arm 30 (see FIG. 4). After reaching the ascending end position, that position is maintained by applying the braking force of the electric motor 6, and the conveyed object W is transferred to and from the upper conveyor 16A.
Thereafter, by rotating the rotating arm 30 counterclockwise (reverse direction) from this ascending end position, the elevating member 5 can be lowered to the initial descending end position.

FIG. 6 is a diagram showing the lateral load and bending moment generated in the electric lifting device 1 of this embodiment in comparison with the case of an electric lifting device of a comparative example. In the figure, (a) shows the electric lifting device 1 of this embodiment, and (b) shows the electric lifting device 100 as a comparative example.

The electric lifting device 100 as a comparative example has the following features: the connection center 38a between the lifting member 5 and the link member 35 and the rotary drive shaft center 9a are arranged on the same vertical line, and the rotating arm during the lifting operation. The difference from the electric lifting device 1 is that the rotation direction of the electric lifting device 30 is only one direction (normal rotation direction).

Furthermore, in the case of the electric lifting device 100 of the comparative example, since the rotary arm 30 is rotated in one direction, the rotary arm 30 and the link member 35 are not located on the same plane, but on the connecting axis (the axis of the first shaft pin 33). It shall be constructed as an offset cantilever structure. Further, in the comparative example, although not shown, a rotary drive shaft 9 is attached to the distal end side of the output shaft of the electric motor 6, and a rotary arm 30 is attached to an end portion of the rotary drive shaft 9 on the distal end side. The position where this rotary arm 30 is assembled is located further away from the tip end of the output shaft of the electric motor 6 compared to the electric lifting device 1 of the present invention. Therefore, in the comparative example, a large bending moment is applied to the output shaft of the electric motor 6. As a result, the connecting shaft and the output shaft of the electric motor 6 need to have high rigidity, which increases the size of the device and the manufacturing cost.
In addition, in each example of FIG. 6, the downward load acting on the link member 35 is 15 kN.

First, let's compare the lateral load and bending moment when the rotating arm 30 is horizontal.
As shown in (b) of FIG. 6A, the inclination of the link member 35 in the electric lifting device 100 of the comparative example is 17°, and the lateral load caused by this inclination is 4.46 kN. Further, the bending moment acting on the guide rod 26 extending upward is 124.9 kN·cm. In the case of the electric lifting device 100 of the comparative example, opposite lateral loads (both 4.46 kN) are generated when ascending and descending.

On the other hand, as shown in (a) of FIG. 6(A), the inclination of the link member 35 in the electric lifting device 1 of this embodiment is 11 degrees. The inclination is kept small compared to the comparative example, and the lateral load caused by this inclination is 2.96 kN. Further, the bending moment acting on the guide rod 26 is 82.9 kN·cm. That is, it can be seen that the lateral load caused by the inclination of the link member 35 is suppressed to 66% of that of the comparative example.

Next, a comparison will be made of the lateral load and bending moment when the rotating arm 30 is oriented vertically upward.
As shown in (b) of FIG. 6(B), in the case of the electric lifting device 100 of the comparative example, the rotary drive shaft center 9a and the connection centers 33a, 38a at both ends of the link member are located on the same vertical line. No lateral loads occur.

On the other hand, as shown in (a) of FIG. 6(B), the inclination of the link member 35 in the electric lifting device 1 of this embodiment is 6°, and the lateral load caused by this inclination is 1.5 kN. . At this time, the bending moment acting on the guide rod 26 is 81 kN·cm.
In the example of (a) in FIG. 6(B), since the elevating member 5 is at the ascending end position, the length of the guide rod 26 extending from the upper end of the guide rod holding member 50 is the maximum. Therefore, when a lateral load occurs, the bending moment tends to increase, but the bending moment in the electric lifting device 1 of this embodiment is 81 kN·cm, and the bending moment when the rotating arm 30 is horizontal is 82 kN·cm. This is approximately the same level as .9kN·cm.

From these results shown in FIG. 6, it can be seen that according to the electric lifting device 1 of this embodiment, compared to the electric lifting device 100 of the comparative example, the maximum lateral load caused by the inclination of the link member and the effect on the guide rod are lower. It can be seen that the maximum bending moment caused by the bending is kept low in all cases.

As described above, according to the electric lifting device 1 of this embodiment, the inclination of the link member 35 when the rotary arm 30 becomes horizontal is suppressed, so that the inclination of the link member 35 that occurs due to the inclination of the link member 35 is suppressed. The load can be reduced. This makes it possible to reduce the strength of the portions that receive lateral loads, thereby reducing costs.

According to the electric lifting device 1 of this embodiment, the outer circumferential surface of the guide rod 26 is is supported over a predetermined length in the vertical direction, the length L of the portion of the guide rod 26 on which the bending moment acts is shortened, and the bending moment applied to the guide rod 26 can be reduced. This makes it possible to reduce wear on the sliding parts, and to reduce costs by reducing the strength of the guide rod 26 and measures against wear.

According to the electric lifting device 1 of this embodiment, the bending moment of the guide rod 26 that occurs when the line segment connecting the connection center 33a of the rotary arm 30 and the rotary drive shaft center 9a is horizontal, and the line segment The horizontal distance δ is determined so that the bending moment of the guide rod 26 that occurs when the guide rod 26 is vertical is approximately equal to the bending moment. Thereby, the bending moment of the guide rod 26 is averaged, and the thickness of the guide rod 26 can be set with minimum strength.

In this embodiment, the state in which the connection center 33a between the rotary arm 30 and the link member 35 is located directly below is defined as the lowering end position, and the state in which the connection center 33a is located directly above is defined as the ascending end position. The stopping position of the rotating arm 30 at the rising end position (that is, the position of the connection center 33a in the circumferential direction) can be changed.
For example, as shown in FIG. 7, when the lifting member 5 is at a predetermined lowering end position, the connection center 38a between the lifting member 5 and the link member 35, the rotation drive shaft center 9a, and the rotation arm 30 and the link member It is also possible to configure so that the connection center 33a with 35 is on the same line.

Furthermore, as shown in FIG. 8, even when the elevating member 5 is at the predetermined ascending end position, the connection center 38a between the elevating member 5 and the link member 35, the rotational drive shaft center 9a, and the rotating arm 30 It is also possible to configure the connection center 33a between the link member 35 and the link member 35 to be on the same line.

By doing so, it is possible to prevent an external force acting to rotate the rotary arm 30 from reaching the rotary arm 30 or the rotary drive shaft 9 at the lower end position and the upper end position of the elevating member 5. Thereby, the load on the brake attached to the electric motor 6 can be reduced, and the life of the brake lining can be extended.

Next, FIG. 9 is a longitudinal sectional view of an electric lifting device according to another embodiment of the present invention.
The electric lifting device 1B shown in the figure includes a gantry frame 4B, a lifting member 5B, an electric motor 6, a driving force transmission means 7B, and a rolling prevention means 8. Among these components, components that are common to the configuration of the electric lifting device 1 according to the above embodiment are indicated using the same reference numerals, and the explanation thereof will be omitted.

In the electric lifting device 1B of this embodiment, the lifting member 5B that holds the transported object W and transfers the transported object W to and from the adjacent conveyor device 15 is provided below the gantry frame 4B. . Main components such as the electric motor 6, the driving force transmission means 7B, and the rolling prevention means 8 are attached to and supported by a gantry frame 4B provided on the base 13.

FIG. 9 shows a state in which the elevating member 5B is at the lower end position. The driving force of the electric motor 6 is transmitted to the elevating member 5B via a driving force transmitting means 7B, and the rotary arm 30, which constitutes a part of the driving force transmitting means 7B, is rotated clockwise in the figure. By rotating in the direction, the elevating member 5B can be moved to the rising end position.

Here, in this embodiment, as shown in FIG. 9, when viewed from a direction along the axial direction of the rotary drive shaft 9, the center 9a of the rotary drive shaft 9 is the center 9a of the rotary drive shaft 9 when the rotary arm 30 is rotated to the horizontal position. When viewed from the tip end 32 of the rotary arm 30, it is disposed at a position on the opposite side across a virtual vertical line 41 passing through the connection center 38a between the elevating member 5B and the link member 35. Specifically, the rotational drive shaft center 9a is located at a horizontal distance δ from the virtual vertical line 41 to the right in the figure. Therefore, also in this embodiment, the inclination of the link member 35 when the rotating arm 30 is horizontal is suppressed, and the lateral load generated due to the inclination of the link member 35 can be reduced.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these descriptions. This invention includes various modifications that can be easily conceived by those skilled in the art without departing from the scope of the claims.

1, 1B... Electric lifting device 5... Lifting member 6... Electric motor 9... Rotation drive shaft 9a... Rotation drive shaft center 26... Guide rod 30... Rotation arm 32... Tip part (when the rotation arm rotates to the horizontal position) )
33a... Connection center 35... Link member 38a... Connection center 41... Virtual vertical line 50... Guide rod holding member

Claims (4)

electric motor and
a rotating arm that rotates around the axis of a rotational drive shaft of the electric motor;
an elevating member that is supported by a guide rod extending in the vertical direction and moves up and down;
a link member having one end rotatably connected to the rotary arm and the other end rotatably connected to the elevating member;
An electric lifting device that lifts and lowers the lifting member at a predetermined stroke,
The center of the rotational drive shaft is located on the opposite side across an imaginary vertical line passing through the center of connection between the elevating member and the link member, when viewed from the tip of the rotary arm when the rotary arm is rotated to a horizontal position. Electric lifting device located in position. A guide rod that is fitted onto a portion of the guide rod below the upper end connected to the elevating member, and whose inner circumferential surface faces the outer circumferential surface of the guide rod over a predetermined length in the vertical direction. The electric lifting device according to claim 1, further comprising a holding member. A bending moment of the guide rod that occurs when the line segment connecting the center of connection of the rotary arm with the link member and the center of the rotational drive shaft is horizontal, and a bending moment of the guide rod that occurs when the line segment is vertical. 3. The electric lifting device according to claim 1, wherein a distance between the virtual vertical line and the center of the rotational drive shaft is determined so that the bending moment of and are approximately equal. At the descending end position and the ascending end position of the elevating member, a center of connection between the elevating member and the link member, a center of the rotational drive shaft, and a center of connection between the rotary arm and the link member are on the same line. An electric lifting system according to any one of claims 1 and 2, configured as follows.