KR101527359B1 - standing and seating type desk - Google Patents

Abstract

The present invention relates to a standing and sitting desk and, more specifically, to a standing and sitting desk capable of being used while freely converting a standing type and a sitting type with one desk. According to the present invention, the standing and sitting desk comprises: a main upper plate having an upper surface and a lower surface; a support part to support upward the main upper plate; a sub upper plate coupled to be independently and vertically lifted with respect to the main upper plate; and a lifting part having one end coupled to the main upper plate and the other end coupled to the sub upper plate to vertically lift the sub upper plate with respect to the main upper plate. A mounting groove in which the sub upper plate is inserted when the sub upper plate is lifted down is formed on the main upper plate to be opened. The upper surface of the sub upper plate has the same height as the upper surface of the main upper plate when the sub upper plate is lifted down. The upper surface of the sub upper plate is arranged at a higher position than the upper surface of the main upper plate when the sub upper plate is lifted up.

Description

Standing and sitting table {STANDING AND SEATING TYPE DESK}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a stand-up type and a stand-type shared desk, and more particularly, to a stand-type and desk-type desk which can be freely converted into a stand-

In general, a wardrobe is currently used in various occupational groups in various fields, and it is widely used in offices as well as at home.

Standing or studying is the most recommended posture if you have back pain or back problems because it can reduce the burden on the back to a minimum and it also helps to improve your concentration.

Despite these advantages, stand-up desks are generally not widely used.

It is because the general working environment consists of the left-handed structure, but it is attributed to some conflicting characteristics of the standing-in desk itself.

In other words, the standing table is longer than the sitting table used by the legs of the desk because of the structural characteristics used by the workers.

In order to work long hours on such a table, the worker must always stand and think about the fatigue accumulation.

In addition, the legs with long legs aligned to the height of the standing table are too taller than the surrounding structures (eg, a normal desk) to perform their independent functions, and they also increase their concentration by working as standstill, It does not meet the intention.

In addition, in a workshop where many articles to be stored are stored, it is necessary to secure a separate space for storing the standing chairs.

As a result, the development of a desk capable of utilizing a dining table function, that is, a dining table, based on a left-handed desk and a left-handed chair is further demanded.

Korean Patent Publication No. 10-2013-0107730

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a desk and a sitting console which can use both a sitting table and a standing table.

In order to achieve the above object, according to the present invention, there is provided a stand and a dining table having a main upper plate having an upper surface and a lower surface; A support for supporting the main upper plate in an upward direction; A sub top plate independently vertically coupled to the main top plate so as to be movable up and down; And an elevating part having one end coupled to the main upper plate and the other end coupled to the sub top plate to vertically elevate the sub top plate with respect to the main top plate, Wherein the top surface of the sub top plate and the top surface of the main top plate have the same height when the top surface of the sub top plate is lowered when the top surface of the sub top plate is lifted, And the upper surface is disposed at a position higher than the upper surface of the main upper plate.

And two or more side surfaces of the side surface of the sub top plate face an inner surface of the seating groove in a state where the sub top plate is inserted into the seating groove.

At this time, the sub top plate is formed in a rectangular flat plate shape, and the seating groove is formed in a square shape corresponding to the sub top plate, wherein one of the four inner side surfaces is horizontally opened to form an opening, Three of the four side faces of the sub top plate face three inner side faces of the seating groove and the other one side face of the sub top plate is exposed to the outside through the open portion.

The main upper plate is provided with a receiving part for covering a lower portion of the seating groove. When the sub top plate is lowered, the receiving part is disposed below the sub top plate.

And a cover plate covering the upper portion of the seating groove at a lower portion of the sub top plate when the sub top plate is lifted.

At this time, it is preferable that the cover plate is drawn out from the main upper plate to cover the upper part of the seating groove.

When the cover plate covers the upper portion of the seating groove, the upper surface of the cover plate is made to have the same height as the upper surface of the main upper plate.

The area of the upper surface of the sub top plate can be varied in a state where the sub top plate is raised.

The sub top plate includes a lift plate to which the other end of the lift portion is coupled; And a wing plate coupled to the lifting plate to be rotatable or slidably pullable to vary an area of the sub top plate.

The elevating portion includes a pair of first rail members coupled to the inner surface of the seating groove; A pair of second rail members coupled to side surfaces of the sub top plate; And a pair of link members slidable along the first rail member and the second rail member when the sub top plate is lifted or lowered, the height of the link members being adjustable, wherein when the sub top plate is lowered, And the height of the sub top plate is varied by adjusting the height of the link member.

Wherein the first rail member is formed with a first guide groove having a long hole in the front and rear direction and the second rail member is formed with a long second guide groove having a long hole in the front and rear direction, A first link slidably coupled to the first guide groove and the other end rotatably coupled to the side surface of the sub top plate or the second rail member; And a second link having one end rotatably coupled to the inner surface of the seating groove or the first rail member and the other end slidably coupled to the second guide groove, And intersect with each other in an " X " shape.

The first link and the second link are restrained in such a manner that their central portions are mutually rotatable.

Wherein the first guide groove is located forward of one end of the second link and the second guide groove is located forward of the other end of the first link, Is positioned forward of the other end of the second link inserted in the second guide groove to prevent the sub top plate from descending.

The first and second guide grooves may have hooks formed on at least one of the first guide grooves and the second guide grooves, and one end of the first link or the other end of the second link may be hooked by the hooks when the sub- So that the member and the sub top plate are prevented from being lowered.

The elevating unit may further include a latching shaft connecting one ends of the pair of first links or connecting the other ends of the pair of second links with each other, Or the pair of second guide grooves. When the sub top plate is lifted or lowered, the latch shaft may be caught by the engaging jaws to prevent the link member and the sub top plate from descending.

The length of the first link or the second link may be variable.

According to the shelves of the present invention as described above, the following effects can be obtained.

One desk can be used for both sitting and standing depending on the user's intention. In particular, it can be used as a standing table by raising the sub top plate while keeping the left desk (main top plate) intact.

1 is a perspective view of a desk according to a first embodiment of the present invention,
2 is an exploded perspective view of a desk according to a first embodiment of the present invention,
Fig. 3 is a side sectional structural view in the state shown in Fig. 1,
FIG. 4 is a perspective view of a desk according to a first embodiment of the present invention, in which a sub-
Fig. 5 is a side sectional structural view in the state shown in Fig. 4,
6 is a perspective view and a side sectional structural view in a state in which the seating groove is opened and closed by the cover plate in the state shown in FIG. 4;
FIG. 7 is a perspective view illustrating a state in which the sub-upper plate is expanded to increase the area in the state shown in FIG. 4,
FIG. 8 is a perspective view of a desk according to a second embodiment of the present invention, in which a sub-
FIG. 9 is a side cross-sectional view illustrating a process of lifting and lowering a sub top plate by a lifting unit in a desk according to a second embodiment of the present invention; FIG.
10 is a perspective view of a desk according to a second embodiment of the present invention,
11 is a structural view illustrating a structure in which a length of a link member is variable in a desk according to a third embodiment of the present invention.

First Embodiment

FIG. 1 is a perspective view of a desk according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view of a desk according to a first embodiment of the present invention, FIG. 3 is a side sectional structural view in the state shown in FIG. 1 FIG. 4 is a perspective view of the desk according to the first embodiment of the present invention, in which the sub top plate is lifted, FIG. 5 is a side sectional view in the state shown in FIG. 4, FIG. 7 is a perspective view showing a state in which the sub-upper plate is expanded and the area is increased in the state shown in FIG. 4, in a state in which the seating groove is opened and closed by the cover plate.

1 to 7, the standing and standing table of the present invention includes a main upper plate 10, a supporting portion 20, a sub top plate 30, a lift portion 40, and the like .

The main upper plate 10 has a flat plate shape having an upper surface and a lower surface.

The supporting portion 20 is composed of three or more, preferably four, and supports the main upper plate 10 in an upward direction with respect to the ground.

The sub top plate 30 is coupled to the elevating portion 40 so as to be vertically movable independently of the main top plate 10.

One end of the elevating part 40 is coupled to the main upper plate 10 and the other end is coupled to the sub top plate 30 so that the sub top plate 30 is vertically moved up and down with respect to the main top plate 10 .

On the top surface of the main upper plate 10, a seating groove 11 into which the sub top plate 30 is inserted when the sub top plate 30 is lowered is formed upward.

The seating groove 11 may be formed in various shapes, but it is preferably formed in a rectangular shape as in the present embodiment.

The sub top plate (30) lowered by the elevating portion (40) is inserted into the seating groove (11).

The top surface of the sub top plate 30 and the top surface of the main top plate 10 have the same height when the sub top plate 30 is lowered and the upper surface of the sub top plate 30 So that the upper surface is positioned higher than the upper surface of the main upper plate 10. [

1 and 3, the top surface of the sub top plate 30 and the top surface of the main top plate 10 have the same height when the sub top plate 30 is lowered, 10 and the upper surface of the sub top plate 30 without a step and the user can sit on the chair and use the desk in a sitting state.

4 and 5, the upper surface of the sub top plate 30 is positioned higher than the upper surface of the main top plate 10 when the sub top plate 30 is lifted by the lifting unit 40 So that the user can place the book or the like on the upper surface of the raised upper plate 30 and use the desk in a standing state.

Two or more side surfaces of the side surface of the sub top plate 30 face the inside surface of the seating groove 11 in a state where the sub top plate 30 is inserted into the seating groove 11.

In the present embodiment, the sub top plate 30 is formed in a rectangular plate shape, and the seating grooves 11 are formed in a rectangular shape corresponding to the sub top plate 30.

One of the four inner side surfaces of the seating groove 11 is opened horizontally to form an opening 12. Three of the four side surfaces of the sub top plate 30 are connected to the seating groove 11, And the other one side surface of the sub top plate 30 is exposed to the outside through the opening 12. [

When the seating groove 11 is formed at a corner portion of the sub top plate 30, the opening portion 12 is formed in two places, and the side surface of the sub top plate 30 Two facing the two inner surfaces of the seating groove 11. [

The seating groove 11 may be opened downward in the downward direction, but is preferably closed by the receiving portion 14 as in the present embodiment.

The housing part 14 is integrally formed with the main top plate 10 to close the bottom of the seating groove 11. When the sub top plate 30 is lowered, .

When the sub top plate 30 is lifted up, the storage unit 14 can be used to place objects or the like on the storage unit 14.

The elevating portion 40 for elevating and lowering the sub top plate 30 includes a first rail member 41, a second rail member 43, a link member 46, and the like.

The first rail member 41 is formed in a long bar shape and is configured as a pair, and is coupled to the inner surface of the seating groove 11. [

The second rail member 43 is formed in a long bar shape and is configured as a pair, and is coupled to the side surface of the sub top plate 30.

The first rail member 41 is formed with a long first guide groove 42 in the front and rear direction and the second rail member 43 is provided with a second guide groove 44 in the shape of a long hole, As shown in FIG.

The link members 46 are disposed on both sides of the sub top plate 30 and are slidable along the first and second rail members 41 and 43 when the sub top plate 30 is lifted or lowered. The height is adjusted.

The link member 46 includes a first link 47 and a second link 48.

One end of the first link 47 is slidably coupled to the first guide groove 42 and the other end of the first link 47 is connected to the side surface of the sub top plate 30 or the second rail member 43 As shown in Fig.

The second link 48 is formed in a long rod shape and has one end rotatably coupled to the inner side surface of the seating groove 11 or the first rail member 41 and the other end connected to the second guide groove 44 As shown in Fig.

The first link 47 and the second link 48 are arranged such that the central portions thereof intersect with each other in the shape of an 'X', and the first link 47 and the second link 48 are arranged such that the center portion So that they are rotatably restrained.

The first guide groove 42 is located forward of one end of the second link 48 and the second guide groove 44 is located forward of the other end of the first link 47.

The lifting unit 40 is accommodated in the seating groove 11 between the main upper plate 10 and the sub upper plate 30 when the sub top plate 30 is lowered, The height of the sub top plate 30 is varied by adjusting the height.

In order to prevent the sub top plate 30 from being lowered arbitrarily in a state where the sub top plate 30 is raised by the elevating portion 40, And the center of gravity acting on the sub top plate 30 is located forward of the other end of the second link 48 inserted in the second guide groove 44. [

A center of gravity acting on the sub top plate 30 may be generated by the weight of the sub top plate 30 itself or a book may be placed on the top surface of the sub top plate 30, Or may be generated by an external force F.

The center of gravity acting on the sub upper plate 30 due to its own weight or an external force in the state where the sub top plate 30 is lifted up to the maximum is lower than the center of gravity of the second link 48 inserted into the second guide groove 44 The one end of the first link 47 is not moved forward along the first guide groove 42 due to the upward force acting on the other end of the first link 47 The other end of the second link 48 is not moved forward along the second guide groove 44 because of a center of gravity acting on the upper side plate 30 located at the front and frictional force.

Therefore, the sub top plate 30 can be prevented from descending arbitrarily at a center of gravity acting on the sub top plate 30 without a separate stopper structure in a maximally raised state.

At this time, if a book or the like is placed on the front of the sub top plate 30, the center of gravity acting on the sub top plate 30 is positioned further forward, so that the elevating portion 40 can be prevented from descending .

The desk of the present invention may further include a cover plate 13 covering an upper portion of the seating groove 11 at a lower portion of the sub top plate 30 when the sub top plate 30 rises.

The cover plate 13 can cover the upper portion of the seating groove 11 in various positions and various structures.

In the present embodiment, the cover plate 13 is slidably drawn out from the main upper plate 10 to cover the upper portion of the seating groove 11, as shown in FIG.

The upper surface of the main upper plate 10 and the upper surface of the cover plate 13 can be substantially equal in height even when the sub upper plate 30 is raised by the cover plate 13 as described above.

In addition, the upper surface of the sub top plate 30 can be varied in an elevated state.

The auxiliary upper plate 30 includes a lifting plate 31 to which the other end of the lifting unit 40 is coupled and a lower plate 30 coupled to the lifting plate 31 so as to be rotatable or slidable, And a wing plate 32 for varying the area of the wing plate 32.

7, the wing plate 32 may be slid on the side surface of the lifting plate 31. However, when the wing plate 32 is rotated on the side surface of the lifting plate 31, So that the area of the sub top plate 30 can be varied by rotating the blade plate 32 to rotate.

Hereinafter, an operation process of the present invention having the above-described configuration will be described.

When the user desires to use the tabletop as a left-hand style, the sub top plate 30 is seated in the seating groove 11 as shown in FIGS.

At this time, since the upper surface of the sub upper plate 30 and the upper surface of the main upper plate 10 have the same height, they can be used as a general desk.

Meanwhile, when the user intends to use the desk in a standing position, that is, when the user wishes to use the desk while he is at home, the user lifts up the sub top plate 30 upward.

As a result, the other upper end of the link member 46 coupled to the sub upper plate 30 is raised.

4 and 5, one end of the first link 47 is moved rearward along the first guide groove 42, and the other end of the second link 48 is moved rearward along the first guide groove 42, 2 guide groove 44, the height of the link member 46 is increased.

In this state, that is, in a state where the upper surface of the sub top plate 30 is maximally raised, the center of gravity acting on the sub top plate 30 is adjusted by the self weight of the sub top plate 30 or the weight of the book One end of the first link 47 and one end of the second link 48 are not moved forward because they are located forward of the other end of the second link 48.

Accordingly, the sub top plate 30 can be maintained in a raised state, and the user can stand the book placed on the sub top plate 30.

As described above, in the state where the auxiliary upper plate 30 is elevated, the user can place objects or the like on the main upper plate 10 and can utilize the standing type and the sitting type at the same time using one desk.

6, when the cover plate 13 covers the upper portion of the seating groove 11, the cover plate 13 may be placed on the receiving portion 14, The height of the upper surface of the main upper plate 10 and the height of the upper surface of the main upper plate 10 may be substantially the same,

7, the wing plate 32 is drawn out to increase the upper surface area of the sub top plate 30 so that a large book or object can be easily placed on the sub top plate 30 .

As described above, the present invention can be used for sitting and standing applications by using one desk. Further, since the auxiliary upper plate 30 is independently lifted and lowered from the main upper plate 10, it is possible to utilize both the left type and the standing type at the same time.

Second Embodiment

FIG. 8 is a perspective view of a desk according to a second embodiment of the present invention, and FIG. 9 is a view illustrating a process of elevating and lowering a sub top plate in a desk according to a second embodiment of the present invention FIG. 10 is a perspective view of a desk according to a second embodiment of the present invention, in which a latching axis is added. FIG.

8 to 9, the second embodiment includes a main upper plate 10, a support portion 20, a sub top plate 30, a lift portion 40, and the like.

The second embodiment differs from the first embodiment in the elevation part 40 and will be mainly described.

The elevating portion 40 is composed of a first rail member 41, a second rail member 43 and a link member 46, which are the same as in the first embodiment.

A locking protrusion 45 is formed on at least one of the first guide groove 42 formed in the first rail member 41 or the second guide groove 44 formed in the second rail member 43.

In this embodiment, the engagement protrusions 45 are formed in both the first guide groove 42 and the second guide groove 44.

One end of the first link 47 and / or the other end of the second link 48 are hooked by the engaging protrusions 45 when the sub top plate 30 is lifted up and the link member 46 and the sub top plate 30 ) From falling.

In this case, unlike the first embodiment, the center of gravity acting on the sub top plate 30 need not be located forward of the other end of the second link 48. [

In the same structure as that of the second embodiment, the height of the sub top plate 30 can be variously adjusted by the engagement protrusions 45. [

As shown in FIG. 10, the elevating unit 40 may connect one end of the pair of first links 47 or the other end of the pair of second links 48 to each other And may further comprise a latching shaft 49.

The latching shaft 49 is disposed across a pair of the first guide grooves 42 or the pair of second guide grooves 44. When the auxiliary top plate 30 is lifted or lowered, Is caught by the engaging jaw 45 to prevent the link member 46 and the sub top plate 30 from descending.

Other details are the same as those of the first embodiment, and a detailed description thereof will be omitted.

Third Embodiment

FIG. 11 is a structural view illustrating a structure in which a length of a link member varies in a desk according to a third embodiment of the present invention.

11, the third embodiment includes a main upper plate 10, a support portion 20, a sub top plate 30, a lift portion 40, and the like.

The third embodiment differs from the first embodiment in the elevation part 40 and will be mainly described.

The elevating portion 40 is composed of a first rail member 41, a second rail member 43 and a link member 46, which are the same as in the first embodiment.

The length of the first link 47 and / or the second link 48 constituting the link member 46 may be variable.

That is, the first link 47 and / or the second link 48 are connected to each other by a plurality of pipes, and the length of the first link 47 and / or the second link 48 is changed by drawing, Can be adjusted.

The length of the first link 47 and / or the second link 48 is adjusted so that the angle of the raised upper plate 30 is inclined forward so that the book placed on the upper plate 30 is inclined So that the user can view the book placed on the sub top plate 30 more clearly.

In the present embodiment, the first link 47 and / or the second link 48 are connected to the plurality of pipes 47 and / or the second link 48 in such a manner that the length of the first link 47 and / The length of the first link 47 and / or the length of the second link 48 may be varied through various structures and methods known in the art. have.

The engagement protrusions 45 of the second embodiment may be applied to the first guide groove 42 and the second guide groove 44.

Other details are the same as those of the first embodiment or the second embodiment, and a detailed description thereof will be omitted.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea of the present invention.

10: main upper plate, 11: seating groove, 12: open part, 13: cover plate, 14:
20: support,
30: a sub top plate, 31: a steel plate, 32: a blade plate,
The present invention relates to an elevator for a railroad car which is provided with an elevating portion for elevating and lowering the elevating portion, : Second link, 49: latching axis,

Claims (15)

A main upper plate provided with an upper surface and a lower surface; A support for supporting the main upper plate in an upward direction; A sub top plate independently vertically coupled to the main top plate so as to be movable up and down; And a lift part coupled to the main upper plate at one end and coupled to the sub top plate at the other end to elevate the sub top plate in the vertical direction with respect to the main top plate,
Wherein the main upper plate has an upwardly open seating groove in which the sub top plate is inserted when the sub top plate is lowered,
Wherein the top surface of the sub top plate and the top surface of the main top plate have the same height when the sub top plate is lowered and the top surface of the sub top plate is disposed at a higher position than the top surface of the main top plate,
The elevating unit includes:
A pair of first rail members coupled to an inner surface of the seating groove; A pair of second rail members coupled to side surfaces of the sub top plate; And a pair of link members slidable along the first rail member and the second rail member to adjust the height thereof when the sub top plate is lifted and lowered,
Wherein when the sub top plate is lowered, the elevating portion is accommodated in the seating groove between the main top plate and the sub top plate,
The height of the sub top plate is varied by adjusting the height of the link member,
Wherein the first rail member is formed with a first guide groove having a long hole shape in a longitudinal direction and a second guide groove having a long hole shape is formed long in the front and rear direction on the second rail member,
The link member
A first link having one end slidably engaged with the first guide groove and the other end rotatably coupled to the side surface of the sub top plate or the second rail member; A first link having one end rotatably coupled to the inner surface of the mounting groove or the first rail member and the other end slidably coupled to the second guide groove,
Wherein the first link and the second link are mutually crossed in an 'X'
Wherein the first guide groove is located forward of one end of the second link and the second guide groove is located forward of the other end of the first link,
Wherein a center of gravity acting on the sub top plate at a maximum rise of the sub top plate is located forward of the other end of the second link inserted in the second guide groove to prevent the sub top plate from being lowered, And a sitting table. A main upper plate provided with an upper surface and a lower surface; A support for supporting the main upper plate in an upward direction; A sub top plate independently vertically coupled to the main top plate so as to be movable up and down; And a lift part coupled to the main upper plate at one end and coupled to the sub top plate at the other end to elevate the sub top plate in the vertical direction with respect to the main top plate,
Wherein the main upper plate has an upwardly open seating groove in which the sub top plate is inserted when the sub top plate is lowered,
Wherein the top surface of the sub top plate and the top surface of the main top plate have the same height when the sub top plate is lowered and the top surface of the sub top plate is disposed at a higher position than the top surface of the main top plate,
The elevating unit includes:
A pair of first rail members coupled to an inner surface of the seating groove; A pair of second rail members coupled to side surfaces of the sub top plate; And a pair of link members slidable along the first rail member and the second rail member to adjust the height thereof when the sub top plate is lifted and lowered,
Wherein when the sub top plate is lowered, the elevating portion is accommodated in the seating groove between the main top plate and the sub top plate,
The height of the sub top plate is varied by adjusting the height of the link member,
Wherein the first rail member is formed with a first guide groove having a long hole shape in a longitudinal direction and a second guide groove having a long hole shape is formed long in the front and rear direction on the second rail member,
The link member
A first link having one end slidably engaged with the first guide groove and the other end rotatably coupled to the side surface of the sub top plate or the second rail member; A first link having one end rotatably coupled to the inner surface of the mounting groove or the first rail member and the other end slidably coupled to the second guide groove,
Wherein the first link and the second link are mutually crossed in an 'X'
Wherein the length of the first link or the length of the second link is variable. The method according to claim 1 or 2,
The sub top plate is formed in a rectangular flat plate shape,
Wherein the seating groove is formed in a rectangular shape corresponding to the sub top plate,
Wherein one of the four inner surfaces is horizontally opened to form an opening,
Wherein three of the four sides of the sub top plate face three inner side surfaces of the seating groove in a state where the sub top plate is inserted into the seating groove and the other one side of the sub top plate Wherein the door is exposed to the outside. The method according to claim 1 or 2,
The main upper plate is provided with a receiving part for closing a lower portion of the seating groove,
Wherein when the sub top plate is lowered, the receiving portion is disposed below the sub top plate. The method according to claim 1 or 2,
Further comprising a cover plate covering the upper portion of the seating groove at a lower portion of the sub top plate when the sub top plate is lifted up. The method of claim 5,
Wherein the cover plate is drawn out from the main upper plate to cover an upper portion of the seating groove. The method according to claim 1 or 2,
Wherein an area of the upper surface of the auxiliary upper plate is variable when the auxiliary upper plate is raised. The method of claim 7,
The sub-
A lifting plate to which the other end of the lifting unit is coupled;
And a wing plate coupled to the lifting plate so as to be rotatable or slidable to change an area of the sub top plate. delete delete The method according to claim 1 or 2,
Wherein the first link and the second link are restrained in such a manner that their central portions are mutually rotatable. delete The method according to claim 1 or 2,
Wherein at least one of the first guide groove and the second guide groove has a latching protrusion,
Wherein one end of the first link or the other end of the second link is hooked by the engaging jaw to prevent the link member and the sub top plate from being lowered when the sub top plate is lifted or lowered. 14. The method of claim 13,
The elevating unit includes:
Further comprising a latching shaft interconnecting one ends of the pair of first links or interconnecting the other ends of the pair of second links,
The holding axis is disposed across a pair of the first guide grooves or a pair of the second guide grooves,
Wherein the latching shaft is caught by the latching jaw to prevent the link member and the sub top plate from descending when the sub top plate is lifted or lowered. delete

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