JP2000247586A - Elevating method for heavy article and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an elevating method and device for heavy articles with a good stability, by using a jack of low cost and short length and reducing the number of processes. SOLUTION: In this elevating method, vertically stackable first to third loading tables 11 to 13 and a jack 19 which can be housed in the first and the second loading tables 11 and 12 are used. A process to install or to remove the third loading table 13 on the second loading table 12 is included in the condition that a heavy article supporting part at the upper part above the ceiling plate 14 of the second loading table 12 placed on the first loading table, is placed at the upper position above the ceiling plate 14 of the third loading table 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for lifting a heavy object, and more particularly, to a method and an apparatus for lifting a heavy object using a jack and a mounting table supporting the jack.

[0002]

2. Description of the Related Art Conventionally, when lifting or lowering heavy objects, a crane device provided on a tow truck, a ceiling, or the like has been used. However, since the crane device has a large weight and a large shape, it often cannot be accommodated in a factory or a construction site, and in some cases, cannot be introduced because it is expensive. As described above, when the crane device cannot be used, a heavy object can be lifted and lowered using a jack such as a hydraulic jack. Hereinafter, a method of lifting and lowering a heavy object will be described with reference to FIG. First, with reference to FIGS. 5A to 5D, a case in which the heavy object 71 is lifted to a height equal to or greater than the stroke of the short hydraulic jack 70 using the short hydraulic jack 70 will be described. FIG. 5A shows the first step. Heavy goods 7
A support bracket 72 is fixed to one side. A short hydraulic jack 7 is provided below the support bracket 72.
0 is erected so that the receiving metal 73 provided at the tip of the short hydraulic jack 70 is located immediately below the support bracket 72.

FIG. 5B shows a second step. When the hydraulic jack 70 is operated and the ram 74 is extended, the hydraulic jack 70 lifts the heavy object 71 via the receiving metal 73 and the support bracket 72. An installation table 75 is installed in a space formed between the heavy object 71 and the floor. Then ram 7
4 is lowered, and the heavy object 71 is supported by the installation table 75. FIG.
In the third step shown in (C), the ram 7 of the hydraulic jack 70 is
4 is further reduced, and a support base 76 is installed between the hydraulic jack 70 and the floor. Then, in the fourth step shown in FIG. 5D, the hydraulic jack 70 is operated again to extend the ram 74, and the installation table 77 is installed between the heavy object 71 and the installation table 75. The mounting table 77 may have the same shape as the mounting table 75. A plurality of the mounting table 75 and the supporting table 76 are prepared, and the mounting table 75 and the supporting table 76 are stacked while repeating expansion and contraction of the hydraulic jack 70 with reference to the third step and the fourth step, so that the heavy object 71 is stacked. It could be lifted to a height higher than the stroke of the short hydraulic jack 70. Also, referring to these steps, the heavy object 71 could be lowered from a high position by a substantially reverse procedure.

Referring to FIGS. 5E and 5F, a case in which a heavy object 79 is lifted by using a long hydraulic jack 78 will be described. FIG. 5E shows the first step.
The support bracket 80 is fixed to the heavy object 79. A gap is provided between the contact portion 81 at the tip of the support bracket 80 and the floor, which is larger than the entire length when the long hydraulic jack 78 is reduced. A long hydraulic jack 78 is erected below the contact portion 81. FIG. 5F shows the second step. The heavy load 79 was raised to a predetermined height by extending the ram 82 of the long hydraulic jack 78, and an installation table (not shown) was installed at the lower portion of the heavy load 79 to hold the load. Further, the heavy object 79 could be lowered from a high position.

[0005]

However, the above-described conventional method of lifting and lowering heavy objects and its apparatus have the following problems. (1) When a short jack is used, an installation table for supporting a heavy object and a support table for supporting the jack are required, and the equipment cost is high, and the number of steps in each process is large. (2) On the other hand, when a long jack is used, it is necessary to mount the support bracket at a high position, so that the shape becomes complicated, the manufacturing cost of the support bracket increases, and the long jack is expensive. As a result, the cost was further increased. (3) In both cases of short and long jacks, the stability when lifting heavy objects is poor, and the jack may fall over. As described above, each of the long and short jacks has a problem of man-hour and cost, and there is a problem of stability in using either of them. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of lifting and lowering a heavy object with good stability by using a cheap short jack and reducing man-hours.

[0006]

According to the present invention, there is provided a method for elevating and lowering a heavy object according to the present invention, wherein the first to third mounting tables capable of being vertically stacked and the first and second mounting tables are provided. Using a jack that can be stored in the mounting table, the heavy object supporting portion above the ceiling plate of the second mounting table mounted on the first mounting table is connected to the jack supporting portion of the first mounting table. The third mounting table is moved to the third mounting table in a state in which the first mounting table is stacked above the height of the ceiling plate of the third mounting table in a state where the first mounting table is stacked on the third mounting table. And a step of attaching or detaching the mounting table on the second mounting table. The first to third mounting tables refer to a mounting table into which a jack is inserted and a mounting table continuously mounted thereon. For example, when the mounting tables are stacked in four stages, When inserting the lower row and the second row from the bottom, insert the lower row first.
, The second stage from the bottom is regarded as the second stage, and the third stage from the bottom is regarded as the third stage. When the jacks are inserted in the second and third stages from the bottom, the second to fourth stages from the bottom are regarded as the first to third mounting tables.

[0007] With the jacks that can be stored in the first and second mounting tables, the third mounting table can be mounted or removed with the heavy object supporting portion positioned above the height of the ceiling plate of the third mounting table. Perform removal. By repeating this, the heavy object can be raised or lowered by the height of the mounting table. Here, the first and second mounting tables arranged at the lowermost part may have an integral structure. Thereby, the connection strength of the first and second mounting tables can be increased. Further, the first to third mounting tables have the same height, the stroke of the jack is S, and the total height when the jack is contracted is C, and the first to third mounting tables are If each height is H and the distance from the bottom surface of the mounting table to the jack supporting surface is t, the following expression can be satisfied. S> H (1) C <2Ht (2) Since the stroke S of the jack is larger than the height H of the mounting table, the jack is placed in an extended state. Mounting or removal of the table can be performed. In addition, the minimum height C of the jack
Is lower than the height obtained by subtracting the distance t from the bottom surface of the mounting table to the jack support surface from the height of the two mounting tables, so that the tip of the jack protrudes from the second mounting table in a state where the jack is reduced. Never.

According to the present invention, there is provided a heavy object lifting / lowering apparatus comprising a jack and a plurality of mounting tables which can be stacked vertically.
When at least one side surface is open, a cutout is formed in the ceiling plate and the bottom plate so that the middle part of the jack is inserted from the open side, and the stroke of the jack is S, and the jack shrinks. When the total height of the table is C, each height of the table is H, and the distance from the bottom surface of the table to the jack supporting surface is t, the following expression is satisfied. S> H (3) C <2H-t (4) Here, each height H of the mounting table is obtained by using the above formulas (3) and (4). If satisfied, each mounting table may have a different height.
Further, the bottom plate of the mounting table used at the lowermost stage may not be provided with a notch. Thereby, the mounting table can be attached or detached from the side of the jack, and the jack can be attached or detached from the side of the mounting table.
Further, the jack may be formed of a hydraulic cylinder, and a pedestal straddling the notch may be provided at the bottom of the jack. The pedestal prevents the jack from falling and falling, and can stably hold the jack.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

As shown in FIG. 1, a lifting / lowering apparatus 10 for a heavy object according to an embodiment of the present invention has a mounting table 11 which can be vertically stacked and a mounting table 11 which can be stacked on the mounting table. Mounting table 12 and mounting table 1 having the same shape as 11
Three. In FIG. 1, the mounting tables 11, 12,
Reference numerals 13 denote first, second, and third mounting tables, respectively. The mounting table 11 is a block made of metal such as iron, and has a ceiling plate 14 and a bottom plate 15 having a certain thickness and being parallel to each other. Horizontal plates 16 and 17 are provided on the left and right sides of the block, and a back plate 18 is provided on the rear side of the block, but the front surface is open. The bottom plate 15 sandwiched between the horizontal plates 16 and 17
The upper part will be described as a jack support in this embodiment. The ceiling plate 14 is formed with a notch 20 into which an intermediate portion of a hydraulic jack 19, which is an example of a jack and composed of a hydraulic cylinder, can be inserted, and the bottom plate 15 is also formed with a notch 21 of the same shape. If the front is not open, any side other than the front is open,
Notches are formed in the ceiling plate 14 and the bottom plate 15 so that the hydraulic jack 19 can be inserted from the opened surface. The shapes of the ceiling plate 14 and the bottom plate 15 can be substantially the same. In this case, since the same operation can be performed even if it is turned upside down, workability is good.

The ceiling plate 14 and the bottom plate 15 extend outward to form an upper flange portion 22 and a lower flange portion 23,
These are provided with a plurality of connecting holes 24 for inserting bolts 25 and fastening to nuts (not shown) on the back side. The number of the connection holes 24 is four in this embodiment, but three
There may be no more than five locations, or five or more locations. When the number of the connection holes 24 is small, bolt fastening can be easily performed, and when the number is large, the fastening strength can be increased. Further, the upper flange portion 22 and the lower flange portion 23 can be omitted. If omitted, weight is reduced, handling becomes easy, and bolt fastening can be omitted, so that man-hour can be omitted.
Since the mounting table 12 and the mounting table 13 have the same shape as the mounting table 11, the description is omitted.

A hydraulic jack 19 is housed in the mounting table 11 and the mounting table 12. As the jack, in addition to the hydraulic jack, a pneumatic jack, a screw jack, a hydraulic jack, or the like can be used. At the bottom of the hydraulic jack 19, a pedestal 2 large enough to straddle the notch 21
6 are provided. The thickness of the pedestal 26 is
(See FIG. 2) may be determined in consideration of the shear stress generated by the load applied to the pedestal 26. Further, the size of the pedestal 26 may be larger than the notch 21,
17, the size can be adjusted to the shape inside the bottom plate 15 surrounded by the back plate 18. A step (not shown) that fits into the notch 21 can be provided on the back side of the pedestal 26. By defining the shape of the pedestal 26, the mounting position of the hydraulic jack 19 can be defined. The pedestal may not be provided integrally with the hydraulic jack, especially when the hydraulic jack is for high pressure, but in this case, the pedestal must be manufactured as a separate part and contact the lower part of the hydraulic jack. Can be used. In this case, although not shown, a hole that does not penetrate is provided in a contact portion of the hydraulic jack with the pedestal, and the hydraulic jack can be positioned by fitting a lower portion of the hydraulic jack into the hole.

Next, with reference to FIG. 2, the lifting method of the lifting / lowering method of the heavy object will be described. FIG. 2A shows the first step. A bracket 28, which is an example of a heavy load supporting portion, is attached to the heavy load 27 placed on the floor. When the side of the heavy load 27 can be used as a contact portion of the hydraulic jack 19, The weight 27 can be directly lifted without the bracket 28. The mounting tables 11 and 12 are installed on the floor below the bracket 28, and the hydraulic jack 19 is inserted from the side of the mounting tables 11 and 12.
Here (the same applies to the second step), the hydraulic jack 1
The mounting tables 11 and 12 in which 9 has been inserted are first and second mounting tables, and the mounting table 13 continuously mounted thereon is the third mounting table.
Will be described as a mounting table. The first mounting table can be fastened by bolts 25 to screw holes (not shown) formed in advance on the floor below the bracket 28. Thereby, the first mounting table can be firmly fixed, and the fall can be prevented. Further, the first mounting table and the second mounting table mounted on the first mounting table can be fastened with bolts 25 and nuts 29 in advance, and further, the second mounting table is mounted on the first mounting table. It is also possible to use a mounting table (not shown) on which the mounting table is mounted to form an integrated structure. By performing the fastening operation of the bolt 25 and the nut 29 in advance, or by using an integrated mounting table, the lifting operation of the heavy object can be performed quickly.

FIG. 2B shows the second step. When the ram 30 of the hydraulic jack 19 mounted on the bottom plate 15 of the first mounting table is extended, the heavy object 27 is lifted via the bracket 28 above the ceiling plate 14 of the second mounting table. In a state where the heavy object 27 is lifted above the height of the ceiling plate 14 of the third mounting table, the ceiling plate 14 of the second mounting table is
And the third mounting table can be fitted between the brackets 28 from the side and mounted. After the third mounting table is fitted, the positions of the connection holes 24 of the second and third mounting tables are adjusted, and the third mounting table is fastened with bolts 25 and nuts 29.

FIG. 2C shows a third step. here,
First, the ram 30 of the hydraulic jack 19 is connected to the hydraulic jack 19.
Of the hydraulic jack 19
Is laterally removed from the first to third mounting tables. When the ram 30 is reduced, the heavy object 27 is mounted on the third mounting table via the bracket 28. Then, the hydraulic jack 19 having the minimum height and removed is inserted from the side of the second and third mounting tables. Here, since the insertion position of the hydraulic jack 19 has changed, the description will be made with the name of the mounting table changed.
That is, the mounting table 12 in which the lower part of the hydraulic jack 19 is inserted is used as the first mounting table, and the mounting table 13 in which the upper part is inserted is used.
Is the second mounting table (the same applies to the fourth step).

FIG. 2D shows a fourth step. When the ram 30 of the hydraulic jack 19 is extended, the heavy object 27 is lifted via the bracket 28. In a state where the heavy object 27 is lifted, a mounting table 31 serving as a third mounting table having the same shape as the mounting table 11 may be inserted between the ceiling plate 14 of the second mounting table and the bracket 28 from the side. it can. After the third mounting table is fitted, the positions of the respective connection holes 24 are adjusted, and the third mounting table is fastened with bolts 25 and nuts 29. Hereinafter, a plurality of mounting tables are prepared, and the weight 27 is raised to a height equal to or greater than the stroke of the short jack 19 by repeatedly expanding and contracting the hydraulic jack 19 with reference to the third and fourth steps. Can be.

Next, a method of lifting and lowering a heavy object will be described. Since the descending method is substantially the reverse of the first to fourth steps of the above-described ascent method, the descending method will be described with reference to FIG. 2 and the description of the same parts will be omitted.

In the first step (see FIG. 2D), the mounting table 11 is fixed to the floor with bolts 25, the mounting tables 11 to 13 and 31 are connected by bolts 25 and nuts 29, and the heavy object 27 is It is mounted on a mounting table 31 via a bracket 28. In a state where the height of the hydraulic jack 19 is minimized, the hydraulic jack 19 is inserted into the first and second mounting tables (mounting tables 12 and 13), the ram 30 of the hydraulic jack 19 is extended, and the third mounting table (mounting table) Lift the heavy object 27 above 31).
With the heavy object 27 lifted, the bolt 25 and the nut 29 connecting the second and third mounting tables are removed, and the third
Remove the mounting table from the side. In the second step (see FIG. 2C), the hydraulic jack 19 is removed from the first and second mounting tables so that the ram 30 is reduced and the height of the hydraulic jack 19 is minimized. At this time, the heavy object supported by the hydraulic jack 19 descends in accordance with the operation of the ram, and is placed on the second mounting table.

In the third step (see FIG. 2B), the hydraulic jacks 19 are inserted into the mounting tables 11 and 12, so that the mounting tables 11 to 13 will be described as first to third mounting tables ( The same applies to the fourth step). When the hydraulic jack 19 is inserted and mounted on the first and second mounting tables and the ram 30 is extended, the heavy object 27 mounted on the third mounting table via the bracket 28 is lifted. With the heavy object 27 lifted, the bolts 25 and nuts 29 connecting the second and third mounting tables are removed, and the third mounting table is removed from the side.

In a fourth step (see FIG. 2A), the ram 3
0 is reduced so that the height of the hydraulic jack 19 is minimized. Heavy object 27 supported by hydraulic jack 19
Is lowered in accordance with the movement of the ram, and its bottom is placed on the floor. At this time, since a gap is opened between the bracket 28 attached to the heavy object 27 and the second mounting table, the load of the heavy object 27 is not applied to the first and second mounting tables. Then, the hydraulic jack 19 is taken out from the side, and the bolt 25 and the nut 2 connecting the first and second mounting tables are taken out.
9. The bolt 25 connecting the first mounting table and the floor is removed, and the first and second mounting tables are removed. In addition, the first and second mounting tables can be detached in a connected state and held as they are, and can be used as the first and second mounting tables having an integrated structure at the next use. Through these steps, the heavy object 27 can be lowered. Even when the number of mounting tables is four or more, the heavy object 27 can be lowered by repeating the lifting and lowering of the hydraulic jack 19 with reference to the first and second steps.

According to the method of lifting and lowering a heavy object described above, the installation table (a table on which the lifted heavy object is placed) used when a short jack is used in the conventional method of lifting and lowering a heavy object. ) Can be omitted, and the number of steps can be reduced. In addition, since the mounting hole is provided in the mounting table, stability can be improved by fixing the mounting table with fixing means such as bolts and nuts. The fixing means naturally includes not only bolts and nuts but also known fasteners such as bolts and cotters. When the height of the heavy object is low, the bolts and nuts may be omitted, and the stability is better than when the mounting table is not used because the wide mounting table holds the hydraulic jack. . In addition, it is also possible to omit the connection hole of the upper flange portion, provide a boss corresponding to the diameter of the connection hole, and have a structure in which the boss is fitted into the connection hole of the mounting table mounted on the boss. Can be omitted and the boss can be used for positioning.

Here, the dimensions of the hydraulic jack and the mounting table used in the method of lifting and lowering a heavy object according to the present invention and the apparatus therefor will be described. FIG. 3 shows an explanatory diagram. First to third mounting tables 32 to 34 having the same shape are installed on the floor, and a hydraulic jack 36 is mounted on a bottom plate 35 of the first mounting table 32. The height when the ram 37 of the hydraulic jack 36 is reduced (the total height when the ram 37 is reduced) is C, and the hydraulic jack 3 is
The stroke of No. 6 is S, the height of each of the first to third mounting tables 32 to 34 is H, and the thickness of the bottom plate 35 representing the distance from the bottom surface of the mounting table to the jack supporting surface is t. (Condition 1) The heavy object placed on the second mounting table 33 is lifted, and the third mounting table is inserted from the side. For this purpose, the height of the tip of the ram 37 should be 3 from the position lower than 2H.
You must move to a position higher than H. When expressed in an equation, S> H (a).

(Condition 2) The hydraulic jack 36 is inserted into the first and second mounting tables 32 and 33 with a heavy object placed on the second mounting table 33. Therefore, the sum of the height C of the hydraulic jack 36 and the thickness t of the bottom plate 35 when contracted must be lower than 2H. When expressed in an expression, C <2Ht ... (b). (Condition 3) The ram 37 is housed in the main body of the hydraulic jack 36. Therefore, the stroke S of the ram 37 must be smaller than the height C of the hydraulic jack 36. In the expression, C> S (c). (Condition 4) The tip of the ram 37 when lifting a heavy object is at a position higher than the third mounting table 34. Therefore, the sum of the stroke S of the ram 37, the height C of the hydraulic jack 36, and the thickness t of the bottom plate 35 must be higher than 3H. In the expression, C> -S + 3H-t (d) When this is expressed in a graph, the range becomes the shaded area in FIG.
When selecting a hydraulic jack in accordance with the mounting table, a hydraulic jack having C and S that falls within the range of the oblique line may be selected and used. In addition, each straight line in FIG.
S = H (e) C = 2H-t (f) C where the inequality signs in equations (a) to (d) are equalized. = S (g) C = -S + 3H-t (h)

By transforming equations (a), (b) and (d), H <S (j) H> (C + t) / 2. (K) H <(C + S + t) / 3 (m) When manufacturing the first to third mounting tables 32 to 34 in accordance with the hydraulic jack 36, the above equation (j) is used.
The mounting table 32 (3) is set so as to satisfy the expressions (k) and (m).
The height H of (3, 34) may be set. It should be noted that, when the equation (k) is modified, 2H> C + t. Assuming that the first mounting table is at the lowermost stage and this height is A, 2
H can be replaced by H + A. Then A> C
+ T−H can be derived. That is, the height A of the lowermost first mounting table can be reduced in accordance with the height C of the hydraulic jack 36. This formula can also be applied to the case where the first and second mounting tables are of an integral structure, and can also be used for a block of an integrated structure in which the height of the first mounting table is lower than that of the second mounting table. Further, the present invention can be used for a block having an integral structure in which the height of the first mounting table is higher than that of the second mounting table. As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment. For example, in the present embodiment, the shape of the notch is circular in accordance with the outer diameter of the jack. However, any shape such as a triangle, a quadrangle, and a hexagon may be used. Further, the horizontal plate and the back plate may be omitted, and a cylinder having the same height as the back plate and having an opening in the front may be used. Although the shape is square, it may be circular. Although the method of supporting the jack on the upper surface of the bottom plate has been described as an example, a jack supporting portion may be separately provided with the bottom plate remaining. Further, the jack is supported by the pedestal provided at the bottom of the jack, but a jack support may be separately provided at the center or upper part of the jack. Further, in this embodiment, the case where the mounting table is erected and used for lifting and lowering a heavy object is described. However, when the mounting table of the present invention is horizontally laid and the heavy object is moved in a horizontal direction, Available.

[0025]

In the method of lifting and lowering a heavy object according to the first to third aspects, jacks that can be stored in the first and second mounting tables are used, and the heavy object supporting portion is moved from the ceiling plate of the third mounting table. Since the third mounting table is mounted or removed in the upper position, the weight can be raised or lowered by the height of the mounting table by repeating this, and using an inexpensive short jack In addition, a large ascending and descending distance can be safely obtained against falling. At this time, since the work can be performed with an open space between the heavy object and the floor, the work of stacking the installation table of the heavy object can be omitted, and the number of steps can be reduced. In particular, in the method of lifting and lowering a heavy object according to the second aspect, the first and second mounting tables disposed at the lowermost portion have an integral structure to increase the connection strength between the first and second mounting tables. As a result, the fall can be prevented, so that the work can be performed stably.
In the method for lifting and lowering a heavy object according to the third aspect, since the stroke S of the jack is larger than the height H of the mounting table, the mounting table can be attached or detached with the ram length maximized. Also, since the minimum height C of the jack is lower than the height 2H of the two mounting tables overlapped with the distance t from the bottom surface of the mounting table to the jack supporting surface, the length of the jack ram was minimized. In this state, the tip of the jack does not protrude from the mounting table, and the operation can be performed reliably.

In the apparatus for lifting a heavy object according to the fourth and fifth aspects, at least one of the side surfaces of the mounting table is open, and the ceiling plate and the bottom plate are formed with cutouts, so that the jack is positioned from the side of the jack. Since the mounting table can be attached or detached, and the jack can be attached or detached from the side of the mounting table, the work can be performed quickly. Further, the jack can be held by the notch, so that the stability is good. In the heavy lifting device according to the fifth aspect, since the jack is formed of a hydraulic cylinder, a large load can be applied to the heavy object. In addition, the jack can be provided with a pedestal that straddles the notch, and the pedestal can prevent the jack from falling and can stably hold the jack.

[Brief description of the drawings]

FIG. 1 is a perspective view of a lifting device used for a method of lifting a heavy object according to an embodiment of the present invention.

FIGS. 2A to 2D are explanatory diagrams of the lifting method.

FIG. 3 is an explanatory diagram showing a positional relationship between a mounting table and a jack.

FIG. 4 is a graph showing a positional relationship between a mounting table and a jack.

FIGS. 5A to 5F are explanatory diagrams of a method of lifting and lowering a heavy load according to a conventional example.

[Explanation of symbols]

10: lifting device, 11: mounting table, 12: mounting table, 13:
Mounting table, 14: ceiling plate, 15: bottom plate, 16: horizontal plate, 1
7: Horizontal plate, 18: Back plate, 19: Hydraulic jack, 20: Notch, 21: Notch, 22: Upper flange, 23: Lower flange, 24: Connection hole, 25: Bolt, 26: Pedestal,
27: heavy, 28: bracket, 29: nut, 3
0: ram, 31: mounting table, 32: mounting table, 33: mounting table, 34: mounting table, 35: bottom plate, 36: hydraulic jack,
37: Ram

Claims (5)

[Claims] 1. A first stackable in a vertical direction.
A third mounting table and jacks that can be stored in the first and second mounting tables, and are located above a ceiling plate of the second mounting table mounted on the first mounting table. The weight supporting portion is lifted from the height of the ceiling plate of the third mounting table in a state where the first to third mounting tables are stacked by the jack mounted on the jack supporting portion of the first mounting table. A method of lifting and lowering a heavy object, comprising a step of mounting or removing the third mounting table on or from the second mounting table in the upper position. 2. The method for lifting a heavy object according to claim 1, wherein said first and second mounting tables arranged at the lowermost portion have an integral structure. 3. The method according to claim 1, wherein the first to third mounting tables have the same height, the stroke of the jack is S, and the jack is contracted. When the total height is C, the height of each of the first to third mounting tables is H, and the distance from the bottom surface of the mounting table to the jack supporting surface is t, the following expression is satisfied. The method of lifting and lowering heavy objects. S> H (1) C <2Ht (2) 4. A lifting device for lifting a heavy object comprising a jack and a plurality of mounting tables that can be stacked in the vertical direction, wherein the mounting table has at least one side open and a ceiling plate and a bottom plate. A notch into which an intermediate portion of the jack is inserted from the open side is formed, and the stroke of the jack is S, the total height when the jack is contracted is C, and each height of the mounting table is defined as A weight lifting / lowering device, wherein H is a distance from the bottom surface of the mounting table to the jack supporting surface, and the following formula is satisfied. S> H (3) C <2H-t (4) 5. The lifting device according to claim 4, wherein the jack is formed of a hydraulic cylinder, and a pedestal is provided at the bottom of the lifting cylinder to straddle the notch. apparatus.