JPS5849235Y2 - Anti-vibration structure for workbench legs - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a vibration isolation structure for the legs of a workbench.

For example, as shown in FIGS. 1 and 2, the legs 2 of the jack-up type drilling rig installed on the offshore work platform 1 land on the seabed by descending and raise the offshore work platform 1 from the sea surface 8. In this state, perform the intended work from the offshore work platform 1 side, avoiding the influence of waves.

The legs 2 used for supporting the offshore work platform 1 are made by connecting and reinforcing a set of three mutually parallel support legs 3 at a plurality of upper and lower locations with cross beams 4 and diagonal beams 5.

The support leg 3 needs to be provided with a lifting mechanism between it and the offshore workbench 1, and therefore a rack 6 extending in the axial direction is integrally attached to the outer periphery of the support leg 3.

7 is a pinion on the offshore work platform 1 side.

For such offshore work platforms 1, especially large ones,
The length of the submerged portion of the support leg 3 and the length of the portion above the sea surface vary depending on the depth of the water at the work site.

Therefore, when the water depth is relatively shallow, the portion above the sea surface becomes long.

In this state, the natural frequency of the portion above the sea surface becomes small, causing resonance in the low wind speed region.

This tendency is particularly strong in the case of the support leg 3, which has a large rack 6 protruding from its outer periphery, since its cross-sectional shape approximates a rectangle.

In other words, the resonance occurs because, in the case of the support leg 3, when wind hits the integral member consisting of the support leg 3 and the rack 6, which has an approximately rectangular cross-sectional shape, the ridges at the peaks and valleys of the rack 6 Separation of the airflow occurs from the front, and a large vortex is generated behind it, and the influence of mutual interference between the three sets of support legs 3 also aggravates this, exerting a large fluctuating aerodynamic force on the leg 2 itself. This is due to the fact that

As is well known, when a cylinder is hit by an air flow, the air flow separated from the cylinder surface forms a Karman vortex street behind it, which becomes the source of vibration.

Therefore, as a measure to prevent or reduce vibration, a method is often used in which a protrusion is provided on the cylindrical surface, and the protrusion disturbs the air flow separated from the cylindrical surface to prevent the formation of a Karman vortex street.

However, this method has little effect on objects having an approximate rectangular cross section as described above, and may increase the vibration in some cases.

This is because the vibration of the rectangular cross-sectional approximation becomes particularly significant depending on a certain wind direction angle.

The present invention has been made in view of the above points, and examples thereof will be described below.

In FIGS. 3 to 5, 10 is a cylindrical support leg;
As shown in FIG. 3, three of these are integrated by a beam 11 to form a leg 12.

This leg 12 is used to support the offshore work platform in the same manner as described in FIGS. 1 and 2.

Therefore, a pair of racks 13 are fixed to the outer periphery of the support leg 10 over almost its entire length.

The rack 13 is an example of a long member.

14A and 14B are band-shaped wire meshes, which are attached to the rack 1.
The left and right side surfaces 13A and 13B of 3 are spaced apart from each other by a certain distance and are disposed so as to cover them.

The wire meshes 14A and 14B are examples of mesh bodies.

The gaps between the rack side surfaces 13A, 13B and the wire meshes 14A, 14B are maintained by liners 15A, 15B provided on the rack 13 side at predetermined intervals in the longitudinal direction thereof.

The presence or absence of this gap is determined by the relationship with the pinion (see FIG. 1) provided on the offshore work platform side, and is essential when the pinion is thicker than the rack 13.

When the pinion thickness is equal to or smaller than the thickness of the rack 13, it does not interfere with the lifting and lowering of the offshore work platform.
The wire mesh 16A is in contact with the wire mesh 16A.

16B may be provided.

FIG. 7 shows an example in which a wire mesh 17 is provided so as to cover not only the left and right side surfaces 13A and 13B of the rack 13 but also the front surface 13C.

As shown in this example, the left and right sides 1 of the rack 13 are covered with wire mesh 17.
3A, 13B and the front surface 13C are used as support legs 1 when the covered parts do not contribute to the elevation of the offshore platform, that is, when the offshore platform is installed in a shallow place.
near the upper end of 0, etc.

In this way, the separation of airflow generated from the rack ridges can be rectified by the wire meshes 14A, 14B, 16A, 16B, and 17, so that the eddies formed behind them are minimized.

Therefore, vortex vibration can be prevented.

As is clear from the above description, according to the present invention, the complicated vortex formed behind the rack can be eliminated by the rectifying effect by the net-like bodies provided on both sides of the rack, and as a result, It is capable of reducing or preventing vibrations of the support legs.

[Brief explanation of drawings]

Figure 1 is a plan view of the offshore work platform device, Figure 2 is a side view of the same,
Figures 3 to 5 show examples of the present invention, in which Figure 3 is a plan view, Figure 4 is an enlarged cross-sectional view of the main parts, Figure 5 is a side view of the main parts enlarged, and Figure 6 is an enlarged side view of the main parts. is a cross-sectional view of a modified example of FIG.
The figure is a cross-sectional view of another modification. 10...Support leg, 13...Rack, 1
4 A, 14 B, 16 A, 16 B, 17...
・Wire mesh.

Claims (1)

[Scope of utility model registration request] In a workbench device in which a rack is provided on a support leg that penetrates the workbench, and a pinion for driving the support leg up and down that engages with the rack is provided on the workbench, a net-like body is provided to cover both sides of the rack. Features a vibration-proof structure for the legs of the workbench.