KR200273828Y1 - Ascent and Descent Device of Blackboard - Google Patents

Abstract

The present invention relates to a lift device of the blackboard, and more particularly to a precise position control to stop the blackboard accurately in the desired position and the lift device of the blackboard does not descend after stopping.

Lifting means in the lifting device of the blackboard according to the present invention, the hydraulic pump for supplying oil by pumping, the oil supply means for operating the hydraulic pump to pump, and the hydraulic pump of the hydraulic pump is raised and returning A piston in which the lowering position is controlled by opening and closing of a solenoid valve installed in the cylinder; a connecting pipe communicating between the hydraulic pump and the cylinder with the piston extrapolated to supply oil to the cylinder; A connecting rod which is lifted up and down, a bearing which is extrapolated to the left and right sides of the connecting rod, a pulley which is extrapolated and rotated by the bearing, and a rope wound around the pulley, one end of which is fixed to the main board and the other end of which is fixed to a wall .

Description

Ascent and Descent Device of Blackboard}

The present invention relates to a device for lifting a blackboard, and more particularly, to a device for lifting a blackboard that can be manufactured at a simple structure and at a low cost without stopping downward after stopping the blackboard at a desired position. .

Blackboards are mainly used for writing in education. Most blackboards have a certain size, and a large curved blackboard is fixed in a rectangular frame.

The short lecturer can use only the lower part, which puts a considerable burden on the trainees who sit behind. Even the taller lecturers need to lower their back so that they can write on the lower part of the chalkboard. Since the situation is rarely used, the entire board of the blackboard cannot be used evenly, and the lecturer uses only the blackboard that is convenient for writing.

In addition, if there is written information at the bottom of the board, the trainee sitting in the back seat will be hidden from the person sitting in the front seat, so he will have to stand up and repeat the writing of the board. The lecturer had to wait until all the trainees used it.

In order to solve this problem, a height-adjustable blackboard has been proposed. In Korean Patent Publication No. 93-4314, the blackboard is installed to be moved up and down between guide posts erected on both sides, and the weight of the blackboard is balanced. By connecting the counterweight with a rope is configured to ascend the board with a small force.

However, the patent is uncomfortable because the lifting operation is performed by manual labor one by one, there is a case where the flow is caused by the impact, etc. in a state set to a specific height to interfere with the lesson.

In order to solve this problem, the motor is rotated forward and backward by the connection of the electric power, the screw rotated by the power of the motor and the upper and lower ends are rotated by the bearing, screwed to the screw and moved up and down according to the rotation. The configuration of the nut member was previously filed (Application No. 1995-004404), which allowed the blackboard to be automatically raised and lowered.

However, the patent requires a separate anti-descent means, because the screw is positioned up and down to fall by the weight of the blackboard, the capacity of the electric motor must be large, and the screw must be heat treated to apply a large force.

The present invention has been made to achieve the above object, and provided with a hydraulic pump and a cylinder as a lifting means for precise position control to stop the blackboard at the desired position accurately and does not descend after stopping, simple structure and low cost The purpose is to provide a lifting device of the blackboard that can be produced by.

In order to achieve the above object, the present invention, the main blackboard is installed on the front wall surface, such as the lecture room, the auxiliary means for balancing the left and right when the mail blackboard moves up and down, and the main blackboard a predetermined height In the elevating device of the blackboard consisting of the lifting means for lifting up and down with;

The elevating means includes a hydraulic pump for supplying oil by pumping, an oil supply means operable to pump the hydraulic pump, and an opening and closing of a solenoid valve installed in a return pipe by being raised by the hydraulic pressure of the hydraulic pump. A connecting pipe which communicates between the piston whose lowering position is controlled by the piston, the hydraulic pump and the cylinder extrapolated to supply oil to the cylinder, and a connecting rod which is rolled up and down by the piston, Provides a board lifting device characterized in that consisting of a bearing extrapolated to the left and right sides of the connecting rod, a pulley that is extrapolated and rotated to the bearing, and wound around the pulley, one end is fixed to the main blackboard and the other end is fixed to the wall I would like to.

1 is a rear view of the lifting device of the blackboard according to an embodiment of the present invention.

2 is a side view illustrating main parts of FIG. 1.

3 is a side view of the motor portion of FIG. 1.

Figure 4 is a rear view of the lifting device of the blackboard according to another embodiment of the present invention.

5A and 5B are enlarged cross-sectional views during suction and compression of the hydraulic pump shown in FIG. 4.

<Description of the symbols for the main parts of the drawings>

2: wall surface 6b: wall bracket

10: pulley 12: connecting rod

14 rope 16 cylinder

16a: piston 18: hydraulic pump

32: Bolt 36: Solenoid Valve

40a,: bearing 42: motor

46a: Blackboard Bracket 48: Connector

50: return pipe 60: oil tank

62: lower housing 63: upper housing

64: oil piston 100: the main blackboard

200: auxiliary means 300: lifting means

350: oil supply means

Hereinafter, the present invention will be described with reference to the accompanying drawings.

First, looking at the basic configuration of the present invention, the main blackboard 100 is installed on the front wall surface, such as the lecture room, and the auxiliary means 200 for balancing the left and right when the mail blackboard 100 moves up and down, and In the elevating device of the blackboard consisting of elevating means 300 for elevating the main blackboard 100 up and down to a predetermined height;

The elevating means 300, the hydraulic pump 18 for supplying oil by pumping, the oil supply means 350 which operates so that the hydraulic pump 18, and the hydraulic pump 18 A piston 16a which is lifted by hydraulic pressure and whose lowering position is controlled by opening and closing of the solenoid valve 35 provided in the return pipe 50, and a cylinder which extrapolates the hydraulic pump 18 and the piston 16a ( 16 is connected between the connecting pipe 48 for supplying oil to the cylinder 16, the connecting rod 12 which is rolled up and down by the piston 16a, and horizontally rolled up on the piston 16a, and the connecting rod ( 12) the bearing 40a which is extrapolated on both left and right sides, the pulley 10 which is extrapolated and rotated by the bearing 40a, and is wound around the pulley 10, one end of which is fixed to the main board 100 and the other end of the bearing 40a. It is characterized by consisting of a rope 14 fixed to the wall surface (2).

1 is a rear view of the lift device of the blackboard according to an embodiment of the present invention, an example of the case where the oil supply means is automatic.

The main blackboard 100 is a writing board that is located on the wall (2) to the front of the classroom, such that writing is made with writing instruments such as chalk on the front.

Auxiliary means 200 is positioned on both left and right sides of the back of the main blackboard 100, and the auxiliary means 200 holds the left and right balance (balance) so that the main blackboard 100 does not move to tilt left and right when moving up and down. .

In the present invention, the auxiliary means 200 includes a guide post 8 for guiding the main blackboard 100 to move up and down, and a wall bracket 6a for fixing the guide post 8 to the wall surface 2. It is composed of a bush (4) is extrapolated to the guide post (8) and fixed up and down on the back of the main blackboard (2).

When the main blackboard 100 is lifted by the lifting means 300, the bush 4 is also lifted up and down. At this time, the bush 4 is guided (guide) to the guide post 8 fixed to the wall surface 2. It moves up and down.

Looking at the elevating means 300, a hydraulic pump 18 for supplying oil by pumping, and the oil supply means 350 that operates so that the hydraulic pump 18 can be pumped.

3 is a side view of the motor portion of FIG. 1.

The oil supply means 350, the motor 42 is rotated by the connection of the electric power, the chain 44 for transmitting the power of the motor 42, and the power of the motor 42 is rotated and bearing ( A rotating shaft 22 supported by 40b), a rotating plate 52 pivotally inserted into the rotating shaft 22, a connecting rod 24 connected to one side of the rotating plate 52, and the connecting rod 24 It is composed of a rod 26 for pumping the hydraulic pump 18 by being connected to and lifted up and down.

At the end of the rod 26, a roller 28 or a bearing is installed, and two pressurizing portions 26a of the rod 26 are formed around the rotational shaft 30 to pump the hydraulic pump 18 at an intersection. Therefore, it is preferable to provide two rollers 28 and bearings to the pressurizing part 26a.

In addition, the connecting rod 24 may be used by connecting to an unshown cam which rotates with an eccentricity.

That is, the oil supply means 350 converts the rotational motion into a reciprocating motion so that the hydraulic pump 18 is pumped.

The piston 16a of the elevating means 300 is lifted by the hydraulic pressure of the oil supplied to the cylinder 16 by the pumping of the hydraulic pump 18 and opens and closes the solenoid valve 35 installed in the return pipe 50. It descends and the height position is controlled.

The connecting pipe 48 communicates between the hydraulic pump 18 and the cylinder 16 to supply oil to the cylinder 16, and the connecting rod 12 is rolled over the piston 16a to be connected by the piston 16a. Lift up and down.

Bearings 40a are extrapolated to the left and right sides of the connecting rod 12, the pulley 10 is rotatably extrapolated to the bearing 40a, and the rope 14 is wound around the pulley 10.

At this time, when one end of the rope 10 is released, the other side is wound, so that one end of the rope 10 is fixed to the main blackboard 100 and the other end is fixed to the wall surface 2.

The oil supplied by the hydraulic pump 18 is supplied to the cylinder 16 through the connecting pipe 48, thereby raising the piston 16a in the cylinder 16.

The lowering of the piston 16a is automatically adjusted by opening and closing of the solenoid valve 35 installed at a proper position of the return pipe 50.

When the piston 16a rises, the connecting rod 12 installed on the upper side of the piston 16a is also lifted.

Figure 2 is a side view of the connecting rod portion, showing how the main blackboard 100 is elevated.

Both ends of the connecting rod 12 are extrapolated to the bearing 40a, the bearing 40a is extrapolated by the pulley 10 again, and the rope 14 is wound around the pulley 10, and one end of the rope 14 is main It is fixed to the board 100 and the other end is fixed to the wall (2).

In this configuration, when the connecting rod 12 is raised by the piston 16a, the bearing 40a is rotated while being rotated, and at this time, the rope 14 fixed to the main blackboard 100 among the ropes 14 wound on the pulley 10 is rotated. One end of the) is wound on the pulley 10, the main blackboard 100 is raised and the other end of the rope 14 is released from the pulley 10 while being fixed to the wall (2).

On the contrary, when the connecting rod 12 is lowered by opening the solenoid valve 35, the bearing 40a is rotated while being lowered. At this time, the rope 14 fixed to the main blackboard 100 of the rope 14 wound on the pulley 10 is rotated. One end of the pulley 10 is released while the main blackboard 100 is lowered and the other end of the rope 14 is wound on the pulley 10 while being fixed to the wall (2).

Instead of the rope 14 and the pulley 10, the chain may be fixed to the wall surface 2 and the main board 100, and the sprocket on which the chain is wound may be extrapolated to the bearing 40a to transmit power by the chain and the sprocket. have.

In the above-described configuration, the switch connected to the motor 42, the solenoid valve 35, and the like should be in a position where the lecturer can easily operate, and the remaining components should be located so as not to be visible on the back of the main blackboard 100.

When the bottom surface of the main blackboard 100 is hinged to the above configuration and further configured, the cylinder 16 is tilted forward or backward by lifting and lowering the tilt of the main blackboard 100.

In addition, when the oil supply means 350 for driving the motor 42 by the electric power is automatic, the lamp is installed in the upper front of the main blackboard 100 and connected to the switch to the main blackboard ( 100) may be brightened, and a limit switch or a sensor is attached to the wall 2 of a suitable height so that the driving of the motor 42 is automatically stopped when the main blackboard 100 is raised or lowered to a certain height. It may be.

Figure 4 is a rear view of the lift device of the blackboard according to another embodiment of the present invention, an example of the case where the oil supply means is manual.

Auxiliary means 200 is positioned on both left and right sides of the back of the main blackboard 100, and the auxiliary means 200 holds the left and right balance (balance) so that the main blackboard 100 does not move to tilt left and right when moving up and down. .

In the present invention, the auxiliary means 200 is a guide post 8 installed on both sides so that the main blackboard 100 can move up and down, and a bracket for fixing the guide post 8 up and down so as not to move ( 7), the bearing 40c which is extrapolated to the guide post 8 and moves up and down, the lifting pipe 90 to which the bearing 40c is press-fitted and fixed therein, and the lifting pipe 90 It is fixed to the blackboard bracket 46a fixed to the back of the main blackboard (100).

When the blackboard bracket 46a is elevated by the elevating means 300, the elevating pipe 90 and the bearing 40c are also guided (guided) to the fixed guide post 8, thereby moving up and down, whereby the main blackboard ( 100) also moves up and down.

Looking at the elevating means 300, a hydraulic pump 18 for supplying oil by pumping and the oil supply means 350 that operates so that the hydraulic pump 18 can be pumped.

5A and 5B are enlarged cross-sectional views of the suction and compression of the hydraulic pump shown in FIG. 4.

The hydraulic pump 18 includes an oil tank 60 containing oil, an oil piston 64 protruding upward from the oil tank 60, and elevating alternately by an oil supply means 350, and the oil tank ( 60 is composed of an upper housing 63 which surrounds the oil piston 64 therein and a lower housing 62 which is coupled to the upper housing 63 and sucks oil to supply the cylinder.

In the oil piston 64, a discharge hole 76 is formed in a cross shape, and a revolving hole 80 is formed outward in the upper housing.

Usually, the position of the discharge hole 76 is higher than the return hole 80, so that oil is not discharged through the discharge hole 76, but the oil piston 64 is lowered so that the position of the discharge hole 76 and the return hole ( If the 80 coincides with each other, the compressed oil of the lower housing 62 is returned to the oil tank 60 through the discharge hole 76 and the return hole 80.

A spring ring 77 is installed in the upper portion of the oil piston 64, and a plurality of sealing rings 78 are inserted in the piston groove in the lower portion to maintain airtightness.

The lower housing 62 is formed such that the upper accommodating part 70a and the lower accommodating part 70ba and 70bb communicate with each other.

The lower receiving parts 70ba and 70bb are formed at right and left sides so that oil is supplied to the lower receiving part 70ba on one side, and the lower receiving part 70bb on the other side is connected to the cylinder 16 through the cylinder 16. Communicating.

The lower accommodating part 70ba of one side is coupled by a plug 73 having a blocking ball 68 and a spring 74 embedded therein, and a suction hole 66 formed therein, and oil is accommodated in the lower part through the suction hole 66. It is sucked into the part 70ba.

The other side of the lower accommodating portion (70bb) is a stopper 75 is sealed down is coupled to the top of the spring 74 and the adjusting opening 72 is located, a portion of the adjusting opening 72 is the upper receiving portion (70a) Protrudes).

Sealing ring 78 is fitted to the adjusting device 72 is kept inclined and inclined downward toward the outside to correspond to the upper shape of the lower receiving portion (70bb).

In addition, the outer periphery of the portion protruding to the upper receiving portion (70a) of the adjusting device 72 is formed with an oil groove 82 so that the oil can be smoothly returned.

The oil supply unit 350 is gripped by a hand and is raised to intersect with respect to the rotational shaft 30. The pressure is formed at an end of the handle 92 and is positioned above the oil piston 64. A portion 77a, a roller 28 provided in the pressing portion 92a and contacting the oil piston 64, and a spring 77 which is extrapolated to the oil piston 64 to raise the oil piston 64. It consists of.

In FIG. 5A, when the right oil piston 64 of the cross-sectional area is raised by the spring 77 by raising the handle 92, the oil is transferred through the suction hole 66 of the one side (left) lower accommodating part 70ba. It is sucked and the blocking ball 68 floats in the lower receiving part 70ba, whereby the spring 74 is compressed upward and oil is supplied to the upper receiving part 70a through the lower receiving part 70ba. do.

At this time, the other side (right) lower receiving portion (70bb) is maintained airtight with the upper receiving portion (70a) by the control opening 72, the discharge hole 76 and the upper housing 63 formed in the oil piston (64) Since the position of the return hole 80 does not match, the oil supplied to the upper accommodating part 70a does not go out.

In this state, when the handle 92 is lowered and the right oil piston 64 of the cross section is lowered, the through ring 77 is compressed and the compressed spring 74 of one side (left) lower accommodation part 70ba is pressed. Returning to this original position, the blocking ball 68 blocks the suction hole 66.

At this time, while the other side (right) the lower receiving portion (70bb) while pressing the control member 72, the oil piston 64 protrudes, the spring 74 under the control device 72 is compressed to descend.

Therefore, the lower receiving part 70bb on the right side and the upper receiving part 70a communicate with each other, so that the oil in the upper receiving part 70a is supplied to the lower receiving part 70bb on the right side, and the oil is connected to the connecting pipe 48. Is supplied to the cylinder 16 through.

This is because the pressure of the upper receptacle 70a is in a state higher than the pressure of the cylinder 16.

When the oil piston 64 is further lowered and the discharge hole 76 and the return hole 80 coincide with each other as shown in FIG. 5B, the oil in the cylinder 16 is connected to the connection pipe 48, the lower receiving part 70bb, and the oil groove ( 82), the upper receptacle 70a, the discharge hole 76 and the return hole 80 is returned back to the inside of the oil tank 60.

This is because the pressure of the cylinder 16 is in a higher state than the pressure of the oil tank 60.

In this way, as soon as the handle 92 is raised and lowered, oil is supplied to the cylinder 16 through the connecting pipe 48, and the discharge hole 76 and the return hole 80 coincide with the handle 92 lowered. If left in the state, the oil in the cylinder 16 is returned to the oil tank (60).

By such a configuration and action it can be seen that the piston 16a can be lowered or the oil can be returned without configuring the return pipe 50 and the solenoid valve 30, etc., so that the structure becomes simple.

In FIG. 4, the piston 16a of the elevating means 300 is lifted by the hydraulic pressure of the oil supplied to the cylinder 16 by the pumping of the hydraulic pump 18 and lowered by the internal structure of the hydraulic pump 18 described above. The position is controlled.

The connecting pipe 48 communicates between the hydraulic pump 18 (more specifically, the lower housing portion 70bb of the lower housing) and the cylinder 16 to supply oil to the cylinder 16 and to supply the oil tank 60. The oil is returned to the), and the connecting rod 12 is rolled up and down by the piston 16a so as to be lifted up and down by the piston 16a.

Bearings 40a are extrapolated to the left and right sides of the connecting rod 12, the pulley 10 is rotatably extrapolated to the bearing 40a, and the rope 14 is wound around the pulley 10.

At this time, one end of the rope 14 is fixed to the end of the bolt 32 installed on the wall bracket 6b, and the other end is wound around the pulley 10 rotatably installed on the other bracket 6c of the wall and the lifting pipe ( 90 is connected to the blackboard fixture 94 through a pulley 10 rotatably installed on the blackboard bracket 46a for fixing the main blackboard 100.

The tension of the rope 14 and the left and right balance of the main blackboard 100 may be adjusted by rotating the bolt 32 and the nut 34 of the wall bracket 6b to which one end of the rope 14 is connected.

When the piston 16a is raised, the connecting rod 12 installed to be horizontally rolled on the piston 16a is also raised.

When the connecting rod 12 is raised by the piston 16a, the bearing 40a is rotated while being rotated. At this time, one end of the rope 14 fixed to the bolt 32 of the rope 14 wound on the pulley 10 is rotated. Is unwound at pulley 10.

At this time, the other end of the rope 14 is wound up and goes through several pulleys 10 to raise the blackboard fixture 94.

At this time, when the piston 16a rises by 1cm, the bolt 32 is pulled by 1cm and the board fixture 94 is raised by 2cm by pulling 1cm to the opposite side.

When the lifting pipe 90 rises along the guide post 8, the main blackboard 100 also rises.

On the contrary, when the piston 16a descends by returning oil from the cylinder 16 to the oil tank 60, the connecting rod 12 also descends.

When the connecting rod 12 is lowered by the piston 16a, the bearing 40a rotates while being lowered. At this time, one end of the rope 14 fixed to the bolt 32 of the rope 14 wound on the pulley 10 is It is wound on the pulley 10.

At this time, the other end of the rope 14 is released while passing through the various pulleys 10 and lowers the blackboard fixture 94.

When the lifting pipe 90 descends along the guide post 8, the main blackboard 100 also descends.

A chain may be used instead of the rope 14 and rollers or sprockets may be used instead of the pulley 10 to transmit power.

By the above-described manual and automatic configuration and operation, the instructor can raise the switch connected to the handle 92 or the motor 42 with a simple operation and can be lowered by the operation of the hydraulic pump 18 or the solenoid valve 35. Can be.

By stopping the operation of the handle 20 or the motor 42, the stop state is maintained as it is, and there is no need for a separate lowering prevention means.

In addition, since the lifting height of the piston 16a becomes the lifting height of the main blackboard 100, the lifting height of the piston 16a can be raised and lowered to a desired position with little force.

As described above, according to the present invention, a hydraulic pump and a cylinder are provided as lifting means to precisely stop the blackboard at a desired position and do not descend after stopping, and can be manufactured with a simple structure and low cost. Do.

Claims (11)

Elevation of the blackboard consisting of a main blackboard installed on the front wall surface of the lecture room, etc. facing the front, an auxiliary means for balancing left and right when the mail blackboard moves up and down, and elevating means for elevating the main blackboard up and down to a predetermined height. In an apparatus; The lifting means, The lowering position is opened by opening and closing of the hydraulic pump for supplying oil by pumping, the oil supply means operating so that the hydraulic pump can pump, and the solenoid valve provided by the hydraulic pressure of the hydraulic pump and installed in the return pipe. A connecting pipe communicating between the controlled piston, the hydraulic pump and the cylinder extrapolated to supply oil to the cylinder; An extrapolated bearing, a pulley that is extrapolated to the bearing to rotate, and a rope wound around the pulley, one end of which is fixed to the main blackboard and the other end of which is fixed to a wall, Lifting device of the board, characterized in that configured. The method of claim 1, wherein the oil supply means, A motor rotated by the connection of an electric power source, a chain for transmitting the power of the motor, a rotating shaft rotated by the power of the motor and supported by a bearing, a rotating plate inserted into the rotating shaft, and connected to one side of the rotating plate A connecting rod which is connected to the connecting rod and a rod which pumps a hydraulic pump by moving up and down, Lifting device of the board, characterized in that configured. The elevating device of the board according to claim 2, wherein the rod is provided with two pressurized parts around the rotation shaft to pump the hydraulic pump at an intersection. The method according to claim 1, wherein the auxiliary means, A guide post for guiding the main blackboard to move up and down, a wall bracket for fixing the guide post to a wall surface, and a bush which is extrapolated to the guide post and fixed up and down on the back of the main blackboard, Lifting device of the board, characterized in that configured. The method of claim 1, wherein the hydraulic pump is pumped by the oil supply means to supply oil to the cylinder through the connecting pipe or return the oil of the cylinder to the hydraulic pump through the connecting pipe, one end of the rope wound on the pulley It is fixed to the bolt installed on the wall bracket, the other end of the blackboard lifting device characterized in that connected to the blackboard fixture fixed to the blackboard through the pulley installed on the blackboard bracket for fixing the auxiliary means to the main blackboard. The method of claim 5, wherein the hydraulic pump, An oil tank containing oil, an oil piston protruding upward from the oil tank and alternately lifting up and down by an oil supply means, an upper housing surrounding the oil piston inside the oil tank, and coupled to the upper housing to suck in oil. Lower housing to supply to the cylinder, Lifting device of the board, characterized in that configured. The method of claim 6, wherein the oil piston is formed in the cross-shaped discharge hole in the cross shape (twist) and the upper housing is formed in a lower position than the discharge hole to the outside of the discharge hole, when the oil piston is lowered to a predetermined position and the position of the discharge hole Lifting device of the board, characterized in that the position of the return hole is in communication with each other. The lower housing has an upper accommodating portion and two lower accommodating portions formed in communication with each other, and the lower accommodating portion on one side is coupled by a stopper having a suction ball formed with a blocking ball and a spring, and the lower accommodating portion on the other side. The lift unit of the board, characterized in that the spring and the adjustment mechanism is inherently coupled to the sealed stopper and in communication with the connecting tube to the cylinder. The upper accommodation according to claim 8, wherein the control mechanism embedded in the lower accommodation portion of the other side protrudes into the upper accommodation portion, and the oil piston is lowered to press the control mechanism, thereby compressing the spring under the control and maintaining airtightness by the control. Lifting device of the board, characterized in that the lower and the other side receiving portion communicating with each other. The method of claim 6, wherein the oil supply means, A handle gripped by a hand and lifted up and down about the pivot shaft, a press portion formed at an end of the handle and positioned above the oil piston, a roller installed at the press portion in contact with the oil piston, and the oil A spring extrapolated to the piston to raise the oil piston, Lifting device of the board, characterized in that configured. The method according to claim 5, The auxiliary means, Guide posts installed on both sides so that the main blackboard can move up and down, brackets for fixing the guide posts up and down so as not to move, bearings extrapolated to the guide posts to move up and down, and the bearings therein With a lifting pipe that is press-fitted and fixed by force, and a blackboard bracket for fixing the lifting pipe to the back of the main blackboard, Lifting device of the board, characterized in that configured.