JPH0419073Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The invention is for use in a lifting device used, for example, to raise an offshore work platform to a predetermined position on the sea during work, and then lower it back to the sea surface after work. Regarding hydraulic jack.

[Prior Art] As is well known, lifting and lowering of heavy objects, such as work on offshore work platforms, climbing cranes, and work on lowering submerged boxes, requires
First and second tightening jacks are provided that are movable relative to the vertically extending fixed legs, and lifting and lowering operations are performed by moving the first and second tightening jacks relative to each other in a so-called inchworm manner. (For example, see Japanese Patent Laid-Open No. 63-268899).

2 and 3 show the prior art of offshore work platforms, in FIG. 2, vertically extending fixed legs 1
(for example, four) have their lower ends buried below the seabed surface E, and a workbench 2 is attached to this fixed leg 1 via a lifting device 3, which will be described later. L in the figure is the water surface. This lifting device 3 is the third
As shown in the figure, the fixed leg 1 is surrounded by the fixed leg 1.
a first tightening jack 4 that is tightened to There is. These first and second
For example, the tightening jacks 4 and 5 are disclosed in Japanese Patent Application Laid-Open No. 62-291313.
The structure disclosed in the above publication can be used.

A reaction force girder 7 is fixed to the upper part of the second tightening jack 4 via a bolt 6, and a workbench 2 is connected to the reaction force girder 7 via a hanging rod 8. , the tips of a piston rod 9 constituting a lifting jack are connected. The cylinder 10 of the lifting jack is fixed to the second tightening jack 5 via a bracket 11.

Therefore, in order to operate, it is assumed that the workbench 2 is now raised, and in the state shown in FIG. Loosen the piston rod 9 of the lifting jack and tighten the second tightening jack 5.
Move it to just below the first tightening jack 4,
Therefore, by fixing the second tightening jack 5 to the fixed leg 1, loosening the first tightening jack 4, and extending the piston rod 9 to move the reaction force girder 7 upward, the workbench 2 can be raised. move. Once the workbench 2 has moved up, the first tightening jack 4 is fixed and the operation is repeated.

However, according to the prior art, in the above-mentioned work, for example, the piston rod 9 is extended, the first tightening jack 4 is tightened, and the cylinder 10 is
When the hydraulic pressure is released, the free movement and deflection that occur when the piston rod 9 extends, that is, the play that occurs between the first tightening jack 4 and the reaction force beam 7, and the looseness of the connection between the piston rod 9 and the reaction force beam 7, are eliminated. As the gap and the deflection of the piston rod 9 and other parts are released at the same time, a shock is generated, causing a sense of anxiety to the worker, and
It is a danger.

[Problems to be Solved] Therefore, an object of the present invention is to provide a hydraulic jack for a lifting device that does not generate a shock when the pressure is released.

[Means for Solving the Problems] According to the present invention, first and second tightening jacks are provided surrounding a fixed leg extending in a vertical direction, and the first tightening jack supports a reaction force girder and supports the reaction force girder. A workbench is connected to the force girder, and in a hydraulic jack for an elevating device for relatively moving the reaction force girder and the second tightening jack, the second tightening jack and the reaction force girder are connected to each other. A jack with a relatively long stroke that performs lifting and lowering operations by relative movement and a jack with a relatively short stroke that absorbs free movement are combined in one cylinder.

[Explanation of effects] Therefore, when a jack with a long stroke is used for normal lifting and lowering work, and when the hydraulic pressure of the jack with a long stroke is released, hydraulic pressure is applied to the jack with a short stroke to prevent it from floating. absorb,
By releasing the hydraulic pressure relatively slowly, the shock can be eliminated.

Therefore, according to the present invention, the jack with a long stroke only needs to be operated in a normal state, and the jack with a short stroke only needs to be operated at a slow speed without impact, making it suitable for automatic driving.

In particular, in conventional single-acting cylinder devices, the entire stroke is not operated, leaving a stroke for absorbing idleness, and the operation for absorbing idleness requires skill and time. However, in the present invention, by combining a long-stroke jack and a short-stroke jack, both can be controlled separately, so the working time can be shortened, and the entire stroke of the long-stroke jack can be used for lifting work. As a result, lifting and lowering operations can be performed automatically, resulting in labor savings.

[Example] An example of the present invention will be described below with reference to FIG.

In FIG. 1, a hydraulic jack embodying the present invention has a generally cylindrical cylinder 20, both ends of which are closed by walls 21, 22, and relatively relatively closed by an intermediate wall 23. It is divided into a long first chamber 24 and a relatively short second chamber 25. A relatively long first piston rod 27 is attached to a first piston 26 that is slidably provided in the first chamber 24, and the piston rod 27 extends through the wall 21 and has a first piston rod 27 at its end. A connecting member such as an eye 28 is attached to the portion. The first chamber, the first piston and the first piston rod form a relatively long stroke jack. On the other hand, a relatively short second piston rod 30 is attached to a second piston 29 slidably provided in the second chamber 25.
The second piston rod 30 extends through the wall 22 and has a connecting member such as an eye 31 attached to its end. The second chamber, the second piston and the second piston rod constitute a relatively short stroke jack.

The portions where the first and second pistons 26, 29 engage with the inner surface of the cylinder 20 and the portions where the first and second piston rods 27, 30 engage with the wall portions 21, 2
Hydraulic seals 32 are provided at the portions penetrating through the cylinders 20, and the cylinders 20 are provided with first and second hydraulic seals 32, respectively.
Hydraulic port 33 for supplying and discharging oil to the chambers 24 and 25
Holes a, 33b, 33c, and 33d are open.

Although the connecting member 28 is connected to the bracket 11 (FIG. 3) and the connecting member 31 is connected to the reaction force beam 7 (FIG. 3), this connection relationship may be reversed. Therefore, the hydraulic port 33
If pressure oil is applied from the hydraulic port 33b and is discharged from the hydraulic port 33b, the first piston rod 27 will contract.On the other hand, if pressure oil is applied from the hydraulic port 33b and discharged from the hydraulic port 33a, the first piston rod 27 will contract. Stretch. Similarly, if pressure oil is applied from the hydraulic port 33c and discharged from the hydraulic port 33d,
The second piston rod 30 extends, applies pressure oil from the hydraulic port 33d, and
If the piston rod is discharged from c, the second piston rod will contract.

[Effects of the invention] As described above, according to the invention, a jack with a relatively long stroke and a jack with a relatively short stroke are combined in one cylinder, so that lifting work and absorption of free movement can be performed easily. This can be done with separate jacks, and by controlling them individually, it is possible to automate the work and save labor.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a side view of a conventional offshore work platform to which the present invention is applied, and Fig. 3 is a side view showing the manner in which a conventional lifting jack is installed. . 20... Cylinder, 21, 22... Wall, 23
... intermediate wall, 24 ... first chamber, 25 ... second chamber, 26 ... first piston, 27 ... first piston rod, 29 ... second piston, 30 ...
...Second piston rod.

Claims (1)

[Scope of utility model registration request] first and second surrounding a vertically extending fixed leg;
a tightening jack, the first tightening jack supports a reaction force girder, a work platform is connected to the reaction force girder, and the reaction force girder and the second tightening jack are moved relative to each other. In a hydraulic jack for a lifting device, a jack with a relatively long stroke performs lifting operation by relatively moving the second tightening jack and the reaction girder, and a jack with a relatively long stroke to absorb free movement. A hydraulic jack for a lifting device, characterized in that a short jack is combined into one cylinder.