JPH061598Y2 - Weight automatic setting type load balancer - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a load balancer capable of transporting a heavy object such as an engine with a small force and holding it at a predetermined place, and particularly, a load balancer having a different weight. Load balancer automatic weight setting device capable of automatically setting the initial balance of heavy goods.

[Conventional technology]

Conventionally, a load balancer is used to carry heavy objects such as an engine to a work place (airframe, etc.) or to carry it from another place (ground, etc.) to another place (ground, etc.) when manufacturing or repairing an aircraft. There is.

This load balancer supports a heavy object in a state of almost zero gravity, moves it by a slight force applied by an operator, and holds it at an arbitrary position. By the way, the load balancer is provided with a balance cylinder for balancing the weight of the heavy load, and a fluid pressure corresponding to the weight of the heavy load acts on the balance cylinder. That is, the initial balance of the load balancer is performed by manually adjusting the set pressure of the pressure reducing valve that adjusts the pressure of the fluid supplied to the balance cylinder.

Therefore, in the conventional device, it is necessary to adjust the pressure reducing valve setting pressure before placing a heavy object on the mounting table.

[Problems to be solved by the device]

However, the conventional load balancer predicts the weight of the heavy object in advance and manually sets the set pressure of the pressure reducing valve before placing the heavy object on the mounting table so that the fluid pressure corresponding to the weight acts on the balance cylinder. Since it had to be dipped and adjusted, there was a problem that the work efficiency decreased.

The purpose of the present invention is to automatically detect an instruction load that fluctuates depending on a heavy load only by giving an instruction as to whether it is a detection period of a support load including a heavy load or an operation period, and supply it to the arm support cylinder. (EN) Provided is a high-performance load balancer equipped with a compact and inexpensive automatic weight setting device, which makes it possible to easily and manually carry heavy objects by controlling the balancing pressurized fluid.

[Means for Solving the Problems]

The load balancer of the present invention includes a carriage, a main arm pivotally mounted on the carriage and operated by a lift cylinder, an intermediate arm pivotally connected to the main arm, and a support connected to the intermediate arm. A mounting table on which a heavy object is placed; and an arm supporting cylinder that receives a supply of a pressurized fluid pivotally attached to both the main arm and the intermediate arm to secure a supporting load including the heavy object and a balance, The arm support cylinder is provided in each of the single cylinder housing having a uniform inner diameter, a separator plate which is arranged in a direction orthogonal to the cylinder axis and divides the inner space of the cylinder housing into upper and lower parts, and the half space. A cylinder shaft extending from the piston in a direction opposite to the separating plate position direction, and a piston rod concentric with the cylinder shaft, and configured in an upper space of the arm supporting cylinder. The cylinder portion is provided with an air brake that restrains the piston rod during the detection period of the heavy load containing load, and the weight sensing cylinder portion is configured as a compressible pressurized fluid source via a pressure reducing valve. Is connected to the pressure reducing valve via a switching valve that is communicated only during the detection period of the heavy load containing load, and transmits the pressure value of the fluid to the pressure reducing valve. A fluid pressure value from the weight sensing cylinder portion transmitted during communication of the valve is stored in a built-in storage means, and a compressive pressurized fluid having a pressure value equal to the stored pressure value is supplied to the balance cylinder portion. It is a load balancer with automatic weight setting.

[Action]

According to the above configuration, when the air brake that restrains the piston rod of the balance cylinder portion of the arm support cylinder is first operated by giving an instruction for the detection period of the heavy load containing load, even if the heavy load is placed on the mounting table, It doesn't move. During this time, the weight-sensing cylinder part of the arm-supporting cylinder receives a total load applied to the arm-supporting cylinder including heavy objects, and a fluid pressure against the load is applied to the incompressible fluid filled in the weight-sensing cylinder part. The fluid pressure is transmitted to the pressure reducing valve that supplies the compressive fluid to the balance cylinder portion of the arm supporting cylinder by pressure control via the switching valve that is communicated only during the detection period of the heavy load supporting load. The pressure reducing valve to which the incompressible fluid pressure is transmitted stores the fluid pressure value and supplies the compressive fluid having a pressure value equal to the pressure value to the balance cylinder portion of the arm supporting cylinder. Alternatively, it is switched by a valve to supply a pressure fluid having a no-load pressure value. The arm supporting cylinder housing is a single cylinder housing having a uniform inner diameter so that the separator can provide the functions of two cylinders. The lower part of the arm supporting cylinder forms a closed circuit by inserting an incompressible fluid between the piston and the separator plate (there is no rod between them) and by forming the switching valve, the pressure reducing valve and the fluid circuit connecting them. A weight sensing cylinder part is formed. The pressure reducing valve is a compressible fluid having the same pressure value as the fluid pressure value stored between the piston of the balance cylinder formed on the upper part of the arm support cylinder and the separator (there is no rod between them). As a result, the pressure balance between both cylinders can be maintained even while the air brake is operating. Alternatively, in the method of supplying the unloaded pressurized fluid, the balance is taken immediately after the valve switching. Both the piston rod of the balance cylinder part and the weight sensing cylinder part and the piston rod are concentric with the cylinder axis, and the piston rod of the weight sensing cylinder part should be made as short as possible without the piston rod (3rd
If the piston is directly pivotally attached to the main arm, the piston rod of the balance cylinder portion is pivotally attached to the intermediate arm, so that the intermediate arm can be stably supported.

If the instruction is switched during the operation period, the pressure of the compressible fluid in the balance cylinder section has already become equal to the pressure of the incompressible fluid in the weight sensing cylinder section, or immediately after switching the valve in the no-load pressurized fluid supply method. Since they are equal to each other, even if the air brake is released by the switching instruction, the balance is maintained as it is, and the mounting table also maintains the normal position. Then, since the supply of the compressive fluid equal to the stored pressure value continues, the heavy object can be easily moved by hand. By making the fluid in the balance cylinder portion having a long stroke a compressible fluid, the force for moving a heavy object can be made as small as possible to provide a load balancer without impact. By making the fluid of the weight sensing cylinder part incompressible fluid and making the incompressible fluid filling thickness as thin as possible, the movement when loading and unloading heavy objects is made as small as possible. The dead length that is not related to the stroke can be made as small as possible.

Since it was made possible to directly carry heavy objects by manipulating them, by operating the operation valve only to instruct switching between the detection period of the heavy load containing supporting load and the operating period, and the balance cylinder unit and the weight sensing cylinder unit. The isolation of the switches greatly simplifies the switching control and simplifies the operating and protection circuits, which allows the number of valves to be extremely reduced.

〔Example〕

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

FIG. 3 shows a load balancer equipped with the automatic weight setting device of the present invention. One end of a main arm 2 is pivotally attached to the carriage 1, and the main arm 2 is tiltably supported by a lift cylinder 3 arranged between the main arm 2 and the carriage 1. One end of an intermediate arm 4 is pivotally attached to the other end of the main arm, and an arm support cylinder 5 is pivotally attached to each arm between the intermediate arm 4 and the main arm 2. The upper side of the arm supporting cylinder 5 is divided into a balance cylinder portion 6 and the lower side thereof is divided into a weight sensing cylinder portion 7. A base 9 is pivotally attached to the other end of the intermediate arm 4 via a base brake 8 and is provided with a temporary fixing means for holding and holding a heavy weight 10 such as an engine on the base 9. The mounting table 11 is supported. In addition, 12 is oil for operating each cylinder,
A supply source of a working fluid such as air, 13 is a leg that fixes the trolley 1 to a work place, and 14 is a main arm brake that keeps the support 2 from rotating.

Next, the first embodiment of the automatic weight setting system of the present invention will be described.
It will be described with reference to the drawings.

In the figure, the inside of a single cylinder housing 15 having a uniform inner diameter is divided into a balance cylinder portion 6 and a weight sensing cylinder portion 7 by a separator plate 16. A piston rod 18 connected to the balance cylinder portion 6 and the piston 17 is pivotally attached to the intermediate arm 4, and a piston rod 20 connected to the piston 19 of the other weight sensing cylinder portion 7 is pivotally attached to the main arm 2. . An air brake 21 for restraining the piston 17 is incorporated in the balance cylinder portion 6.
In No. 1, when air is cut off, the brake operates to restrain the piston rod 18, while when air is supplied, the brake is released to free the piston 17. A pressure reducing valve 2 is provided between the piston 17 of the balance cylinder portion 6 and the separator 16.
A compressible fluid source, that is, an air source 23 is connected via 2. The pressure reducing valve 22 stores a supply valve of pressurized air to the balance cylinder portion 6, a relief valve of the pressurized air from the balance cylinder portion 6, and a fluid pressure signal value transmitted from the weight sensing cylinder portion 7. And a detecting means for detecting the pressure from the balance cylinder portion 6 are incorporated. The supply valve of the pressure reducing valve 22 is closed when the detected value of the balance cylinder fluid pressure is equal to or higher than the weight sensing cylinder fluid pressure stored value, and is opened when the detected value is smaller than the stored value. On the other hand, the relief valve of the pressure reducing valve 22 opens when the detected value is greater than or equal to the stored value, and closes when the detected value is smaller than the stored value. Air having a pressure equal to the stored pressure P of the pressure reducing valve 22 is supplied to the balance cylinder portion 6 to generate an arm support cylinder output equal to the load applied via the intermediate arm 4, thereby balancing the heavy load 10 at an arbitrary position. I am letting you. The storage pressure P of the pressure reducing valve 22 is stored based on the fluid pressure signal from the weight sensing cylinder section 7. An incompressible fluid 24 such as oil is used for the weight sensing cylinder portion 7, and the fluid pressure generated by the relative displacement between the piston 19 and the cylinder housing 15, and thus the separator 16, is used as the memory pressure P of the pressure reducing valve 22. If the memory pressure P of the pressure reducing valve 22 suddenly fluctuates, the heavy load 1
Since 0 cannot be stopped at an arbitrary position in a balanced state, a switching valve 26 that switches the connection between the load detection period and the operation period is provided in a pipe line 25 that connects the weight sensing cylinder unit 7 and the pressure reducing valve 22. Has been done. The switching valve 26 is configured such that, after the fluid pressure corresponding to the load is stored in the pressure reducing valve 22, the first valve portion 27 to the second valve portion 28 are synchronized with the instruction to shift to the operation period.
And the pipe line 25 is closed. Therefore,
The pressure reducing valve 22 is maintained at a constant memory pressure while the heavy object 10 is placed on the mounting table 11, and the balance cylinder unit 6
In response to the change in pressure, the compressed air that is always equal to the stored pressure is supplied (details will be described later).

Further, the balance cylinder portion 6 is provided with an air brake 21 that restrains the piston rod 18 for holding an arbitrary position during a load detection period and in an emergency. The air brake 21 is a first operation period setting manual operation valve 29 for instructing an operation period and a load detection period from the air source 23.
Pressurized air is supplied through the valve section 30 to release the brake, and when the cargo monitoring detection period setting second valve section 31 is switched, the air supply is cut off to operate the brake. ing.

The switching valve 26 is provided at a position branched from a conduit 32 connecting the air brake 21 and the manually operated valve 29, and is switched in synchronization with the release or restraining operation of the air brake 21 by the operation of the manually operated valve 29.

Next, the operation of the above embodiment will be described.

A case will be described in which a heavy heavy object 10 such as an engine is lifted to a site at a predetermined height above the ground. When the mounting table 11 is empty, the manually operated valve 29 is switched to the second valve portion 31, so the air brake 21 is opened to the atmosphere and the brake operates to fix the piston rod 18 to the cylinder housing 15. , The operation of the balance cylinder section 6 is locked. Further, since the switching pressure of the switching valve 26 becomes atmospheric pressure, it is switched to the first valve portion 27, the weight sensing cylinder portion 7 and the pressure reducing valve 22 are connected, and the fluid pressure storing operation is continued.

When the heavy object 10 is placed on the mounting table 11 in this state, the cylinder housing 15 is slightly displaced in the direction of the arrow A in the figure by the weight of the object to be conveyed 10 via the piston rod 18. This is because the piston rod 20 of the weight sensing cylinder portion 7 is fixed to the main arm 2.
This is because the incompressible fluid is compressed until the pressure corresponding to the heavy load is reached, and this fluid pressure is sent to the pressure reducing valve 22. After that, the manually operated valve 29 is switched to the first valve portion 30 to supply pressurized air to the air brake 21 and the switching valve 26, and the switching valve 26 is switched to the second valve portion 28 at the same time when the operation of the air brake 21 is released. When the switching valve 26 is switched to the second valve portion 28, the pressure reducing valve 22 is separated from the weight sensing cylinder portion 7, and the memory pressure P is maintained at a constant value. When the memory pressure P is determined in this way, the internal pressure of the balance cylinder portion 6 is controlled so that it is always equal to the memory pressure value P. That is, when the internal pressure of the balance cylinder portion 6 becomes a value different from the stored pressure value P, the detection means built in the pressure reducing valve 22 detects the pressure and the built-in supply valve or the built-in relief valve operates. The internal pressure of the balance cylinder unit 6 is smaller than the stored value P (P-
When Δp) is reached, the built-in supply valve is opened with the built-in relief valve closed, and air corresponding to Δp is supplied into the balance cylinder portion 6. As a result, when the internal pressure of the balance cylinder portion 6 becomes equal to the stored value P, the built-in supply valve closes.
The internal pressure of the balance cylinder portion 6 is kept at the stored value P. On the other hand, the internal pressure of the balance cylinder portion 6 is the stored value P.
When the value becomes larger (P + Δp ′), the built-in release valve is opened while the built-in supply valve is closed, and the air corresponding to Δp ′ is discharged from the balance cylinder portion 6 to the outside. As a result, when the internal pressure of the balance cylinder portion 6 becomes equal to the stored value P, the internal relief valve closes, so that the internal pressure of the balance cylinder portion 6 is kept at the stored value P.

As described above, in the heavy object placing operation, the heavy object 10 is balanced at the predetermined height H by the internal pressure of the balance cylinder portion 6 (that is, the stored value P). At that time, in the balance cylinder portion 6, the piston 17 stands still at a position of a distance (hereinafter, simply referred to as a distance) L from the separator 16. A volume (hereinafter, simply referred to as volume) V formed by the balance cylinder portion 6 and the piston 17 is approximately V = SL, where S is a cross-sectional area of the balance cylinder portion 6. then,
When the height of the heavy object 10 is displaced by an operator or the like, the heavy object 10 is displaced at the height (H + Δh or H−Δh ′).
To stand still.

That is, referring to FIG. 3, when a worker or the like pulls up the heavy object 10 by Δh, the volume increases from V to V ′ = V + Δv (where the displacement of the piston 17 corresponding to Δh is Δl, the volume is approximately Δv = SΔl increases and V ′ = S (L
+ Δl)). The internal pressure of the balance cylinder portion 6 becomes a value (P-Δp) lower than the stored value P. Therefore, as described above, the built-in supply valve is opened, air is supplied, the internal pressure in the balance cylinder portion 6 quickly becomes the stored value P, and the internal pressure P and the volume V ′ = V + Δv = S in the cylinder portion 6. (L + Δ
It will be held in the state of l). Therefore piston 1
7 stands still at the position of (L + Δl), the height of Δh corresponding to Δl increases in the heavy load 10, and the height (H + Δl) increases.
It will be stationary in the state of h).

On the other hand, when the worker or the like pulls down the heavy load 10 by Δh ', the volume decreases from V to V' = V-Δv '(If the displacement of the piston 17 corresponding to Δh' is Δl ', the volume is approximately Δv'. = SΔl ′ decreases and V ″ = S (L−Δl ′)
become). The internal pressure of the balance cylinder portion 6 becomes a value (P + Δp ′) higher than the stored value P. As a result, the built-in relief valve is opened as described above, air is released to the outside, and the internal pressure of the balance cylinder portion 6 quickly becomes the stored value P. In the cylinder portion 6, the internal pressure P and the volume V ″ = V− Δv ′ = S (L
-Δl ') will be maintained. Therefore, the piston 17 stands still at the position of (L-Δl '), and the weight 1
At 0, the height of Δh ′ corresponding to Δl ′ decreases,
It stands still at the height (H-Δh ').

In this way, since the heavy object 10 is balanced with the internal pressure P of the balance cylinder portion 6 after the heavy object placing operation regardless of the height displacement thereof, the heavy object 10 is lifted by the slight external force from the worker or the like. It can be displaced and stopped at a desired height position.

According to the configuration of the present embodiment, after the fluid pressure storage process of the pressure reducing valve 22, the connection with the weight sensing cylinder unit 7 is cut off by the switching valve 26, so that the built-in storage means of the pressure reducing valve 22 moves the heavy object 10. It is independent of the lineage. Therefore, the state change such as the displacement of the heavy object 10 after the fluid pressure memory processing does not affect the memory processing of the pressure reducing valve 22, and the memory value of the pressure reducing valve 22 is changed during the operation period. The changed value is not reflected in the displacement of the heavy object 10 or the like. In addition, the weight sensing cylinder portion 7 is fixed with the same cross-sectional area as the balance cylinder portion 6, and the weight sensing cylinder portion 7 is filled with the incompressible fluid 24, so that the fluid 2
Since the fluid pressure against the load applied to the load 4 is detected, moreover, the load of the heavy load 10 is not detected before the stroke operation of the balance cylinder portion 6 and the piston rod 18 is restrained by the air brake 21. Should be supplied to the balance cylinder section 6 having the same cross-sectional area by being uniformly weighted to the cross-sectional area of the weight sensing cylinder section 7 without being adversely affected by the motion state of the piston 17 and the like of the balance cylinder section 6. An accurate pressure value can be obtained, and the setting system of the pressure reducing valve 22 becomes sophisticated. Therefore, the responsiveness of displacement and rest of the heavy object 10 can be enhanced.

When performing work such as attachment or detachment of heavy objects, the manual operation valve 29 is switched to the second valve portion 31 and the air brake 2
1 is operated and the piston rod 18 is restrained. At this time, since the switching pressure of the switching valve 26 becomes the atmospheric pressure, the switching valve 26 is switched to the first valve portion 27, and the weight sensing cylinder portion 7 and the pressure reducing valve 2 are switched again.
2 is connected, but since the air pressure in the balance cylinder section 6 and the hydraulic pressure in the weight sensing cylinder section 7 are balanced,
It does not affect the mounting table 11.

Next, a second embodiment of the present invention will be described with reference to FIG. The elements having the same functions as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

A first pressure reducing valve 33 and a second pressure reducing valve 34 are inserted in parallel between the balance cylinder portion 6 and the air source 23, and these pressure reducing valves 23, 34 are switched by a second switching valve 35. One of them is always selectively connected to the balance cylinder section 6 to control the air pressure of the balance cylinder. The first pressure reducing valve 33 stores the pressure from the weight sensing cylinder unit 7 to control the air pressure of the balance cylinder unit 6, while the second pressure reducing valve 34 adjusts the balance pressure when there is no load. The second switching valve 35 is switched in synchronization with the operation of the air brake 21. That is, when the air brake 21 is released, the first pressure reducing valve 33 is selected by switching to the first valve portion 36 of the second switching valve 35, and the second pressure reducing valve 33 is selected when the brake is operated.
The second valve portion 37 of the switching valve 35 is switched to and the second pressure reducing valve 34 is selected.

When a heavy object having a load larger than the maximum supporting load of the mounting table 11 is placed during the operation of the air brake 21, the air brake 21 is released to cause the balance cylinder portion 6 to perform a stroke operation.
A safety device is added to prevent damage to this device and the aircraft. This safety device monitors a pressure change in the weight sensing cylinder unit 7, operates the safety valve 38 when the pressure becomes higher than a predetermined value, and releases the brake operation by the pressurized air from the air source 23.

Next, the operation of the second embodiment will be described.

Before the operation period, the manually operated valve 29 is switched to the second valve portion 31, so that the air brake 21 is in the operating state. At this time, in the switching valve 26 and the second switching valve 35, as shown in FIG. 2, the first pressure reducing valve 33 and the weight detection cylinder portion 7 are connected via the first valve portion 27 of the switching valve 26 and the air The source 23 and the balance cylinder 6 are second
It is in a state of being connected via the pressure reducing valve 34. In this state, the air pressure of the balance cylinder portion 6 is adjusted to the set pressure of the second pressure reducing valve 34 regardless of the supporting load acting on the arm supporting cylinder 5. Here, when the heavy object 10 is placed on the mounting table 11, a fluid pressure signal corresponding to the supporting load including the heavy object 10 is transmitted from the weight sensing cylinder portion 7, and the fluid pressure signal is stored in the first pressure reducing valve 33. It is stored as pressure P. Then, when the manually operated valve 29 is operated and switched to the first valve portion 30, pressurized air is supplied to the air brake 21 to release the brake, and at the same time, the switching valve 26 causes the second valve portion 28 to move to the second valve portion 28. The switching valve 35 is replaced with the first valve portion 36. Since the first pressure reducing valve 33 is disconnected from the weight sensing cylinder unit 7, the stored pressure P is kept constant. Therefore, the balance cylinder portion 6 is supplied with air having a pressure equal to the stored pressure value P of the first pressure reducing valve 33, the balance state is instantly achieved, and the heavy object 10 on the mounting table is held in a substantially weightless state. .

[Effect of device]

As described above, according to the present invention, the single cylinder housing is provided with the separator, the lower portion is provided with the low-weight weight sensing cylinder portion using the incompressible fluid, and the upper portion is provided with the compressible fluid. The use of an arm support cylinder with a long balance stroke cylinder part has a structure that enables the support of the intermediate arm, and the height of the weight sensing cylinder part that cannot participate in the stroke is lowered to reduce the stroke. With the dead length suppressed, the force for moving heavy objects is made as small as possible, making it possible to provide a high-performance load balancer with no impact. In addition, equalizing the inner diameters of the cylinder housings of the weight-sensing cylinder portion and the balance cylinder portion of the arm supporting cylinder is to make the pressure value of the incompressible fluid transmitted from the weight-sensing cylinder portion to the pressure reducing valve,
It is possible to equalize the pressure value of the compressive flow supplied from the pressure reducing valve to the balance cylinder part, which eliminates the need for pressure value conversion operation and enables the use of a simple control circuit with a small number of valves. This has made it possible to provide a compact and inexpensive automatic weight setting device. Furthermore, using a non-compressible fluid for the weight sensing cylinder section to reduce the fluid thickness in the cylinder housing,
The installation of an air brake that restrains the piston rod of the balance cylinder part eliminates the need for an additional severe protection device against an emergency drop in fluid pressure, making it possible to provide a compact and inexpensive automatic weight setting device. Have contributed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an automatic weight setting device for a load balancer according to the present invention, FIG. 2 is a configuration diagram showing another embodiment of the present invention, and FIG. 3 is a front view of the load balancer. Is. DESCRIPTION OF SYMBOLS 1 ... Bogie, 2 ... Main arm, 3 ... Lifting cylinder, 4 ... Intermediate arm, 5 ... Arm supporting cylinder, 6 ... Balance cylinder part, 7 ... Weight sensing cylinder part, 10 ... Heavy object, 1 ... Mounting table, 15 ... Cylinder housing, 16 ... Separator, 17 ... Piston, 18 ... Piston rod, 19 ... Piston, 21 ... Air brake, 20 ... Piston rod, 22 ... Pressure reducing valve, 23 ... Compressible fluid source, 24 ... Incompressible fluid , 26 ... Switching valve.

Front page continuation (56) References JP-A-52-49314 (JP, A) JP-A-48-37857 (JP, A) JP-B-50-38859 (JP, B1) JP-B-52-19324 (JP) , Y1) Actual public 52-35826 (JP, Y1) Actual public 54-28770 (JP, Y2)

Claims (1)

[Scope of utility model registration request] 1. A trolley, a main arm pivotally mounted on the trolley and operated by a lift cylinder, an intermediate arm pivotally attached to the main arm, and a heavy load connected to and supported by the intermediate arm. A mounting table on which the vehicle is mounted, and an arm supporting cylinder pivotally mounted on both the main arm and the intermediate arm to receive a supply of a pressurized fluid and to secure a supporting load including the heavy object and a balance. Is a single cylinder housing having a uniform inner diameter, a separator plate which is arranged in a direction orthogonal to the cylinder axis to divide the internal space of the cylinder housing into two parts, and a piston arranged in each of the two divided spaces. A balance cylinder part that is provided with a piston rod concentric with a cylinder shaft extending in the direction opposite to the direction of the separator plate and is configured in an upper space of the arm support cylinder. A weight that is connected to a compressible pressurized fluid source via a pressure reducing valve and includes an air brake that restrains the piston rod during a detection period of the heavy load containing supporting load, and is configured in a lower space of the arm supporting cylinder. The sensing cylinder portion is filled with an incompressible fluid and is connected to the pressure reducing valve via a switching valve that is communicated only during the detection period of the heavy load containing supporting load, and transmits the pressure value of the fluid to the pressure reducing valve. However, the pressure reducing valve stores the fluid pressure value from the weight sensing cylinder portion transmitted during the communication of the switching valve in a built-in storage means, and stores a compressible pressurized fluid having a pressure value equal to the stored pressure value. An automatic weight setting type load balancer supplied to the balance cylinder section.