JPS5933754Y2 - Fixing device for marine portal cranes, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that allows a marine gantry crane to be advantageously secured.

In general, in marine gantry cranes, even if the main body of the crane, such as the girder and legs, is able to withstand its own weight and handling cargo, it is not possible to sufficiently withstand the bending moment caused by the horizontal force caused by rolling, etc. Not exclusively.

In other words, for girders, the dimensions of the members are generally determined by their own weight and the weight of cargo (hereinafter referred to as long-term vertical loads), but for legs, the dimensions of the members are not determined by long-term vertical loads, but by rolling. It is no exaggeration to say that it is determined by horizontal force (hereinafter referred to as short-term horizontal load).

This is because the bending moment acting on the girder is the largest due to long-term vertical loads, and girder members and dimensions can be determined based on this moment, but the bending moment acting on the legs is This is because the bending moment caused by a short-term horizontal force due to rolling or the like is larger than the bending moment caused by a horizontal force that is 10% of the load and long-term vertical load.

It is assumed that during normal work, in addition to the long-term vertical load, a horizontal force of 10% of the long-term vertical load is applied to the legs, but this is determined by the calculation standards for steel structures. This is stated in reference books for structural calculations.

Next, we will briefly explain why even if the crane body can sufficiently withstand a heavy load, it cannot necessarily withstand the horizontal force during rolling.

However, in actual design, various conditions must be considered and cannot be explained easily, so the following explanation will be made in a very simplified manner for convenience.

In general, during normal operations, a long-term vertical load P, which is the sum of its own weight g and the load W due to cargo, acts on the crane, as shown in Figure 5A, and on the traveling wheel C on one side, A long-term horizontal car of 110% of the wheel load is assumed to be in effect.

The bending moment generated in girder e and leg d due to long-term vertical load P is as shown in Figure 5, and the bending moment generated in girder e and leg d due to horizontal force is as shown in Figure 5. become.

In Figure 5, if the span of the girder is l, then the girder is
The bending moment MA of da e is as follows.

Here K is stiffening, For stiffening It is expressed as

However, (1) is the moment of inertia of the leg d, (2) is the moment of inertia of the girder e, and h is the height of the leg d.

Further, the bending moment at the center point C of the girder e is expressed by , and the maximum bending moment occurring at the leg d is expressed by .

Incidentally, formulas (i) to (IV) are described in general works on structural mechanics.

l On the other hand, since the bending moment due to the horizontal car is At girder e and leg d parts respectively becomes.

Further, assuming that K=1, the above equations (1), (iii), and (IV) become as follows.

Therefore, the girder e is determined by the larger one of MA=MA1+MA2.

If we now assume z=h, then lMo1>IMAI, so in this case girder e is M.

The cross-sectional dimensions can be determined by

Also, the maximum bending moment of leg d is Therefore, based on this, the cross-sectional dimension of leg d is determined.

Next, a case where the ship rolls due to strong winds or the like will be explained.

However, when designing the crane, it is assumed that no work will be carried out during storms.

Therefore, during a storm, only the dead weight g acts as a vertical load.

Now, if the ship is tilted by an angle θ due to rolling, as shown in FIG. 6A, the force due to its own weight g is divided into a vertical load gCosθ on the girder e and a horizontal load gsinθ on the leg d.

Based on this load, the bending moments shown in Figure 6, Figure 6, are calculated as follows.

And, (vii) 2~(x1) formula is becomes.

Therefore, the maximum bending moment of girder e during rolling is Moment of time M.

The cross-sectional dimension may be determined by =0.175Pl.

On the other hand, the maximum bending moment during rolling of leg d is (bending moment during long-term load) MA'--0,1
It becomes larger than 25P#.

Therefore, the cross-sectional dimension of the leg d must be determined by the bending moment MA' during rolling.

Also, although not shown for the sake of brevity, in reality, when rolling, wind acts on the side of leg d, and inertia due to left and right sway acts, so the maximum moment MA' due to horizontal force during rolling is is actually much larger than 0.158Pl.

Therefore, even a member that can withstand its own weight and the weight of the cargo may not necessarily be able to withstand the rolling.

This applies not only to rolling but also to pitching.

The following explanation is based on the above.

By the way, in a ship equipped with a gantry crane a having a shape as shown in FIG. 1, the oscillation of the ship during navigation has a very large effect on the weight of the gantry crane a.

In other words, a large horizontal force acts on the shipboard structure of portal crane a due to pitching, rolling, etc. of the ship.
There is a risk that the shipboard structure will move.

Therefore, during the voyage, it is necessary to securely secure the ship's structures.

For example, as shown in FIG. 2, the center of gravity G of the portal crane a is located at a considerably high location, and a lateral horizontal force H acts on the center of gravity G due to the rolling of the vessel.

This horizontal force H is usually applied by bringing the flange of the running wheel C shown in FIG. The lower part of the leg d was fixed with wire ropes, pins, screws, etc.

However, in any case with the above method, the leg d of the gantry crane a
This method supports the lower part of the leg d by horizontal force.
The bending moment acting on the girder e1 and the girder e1, especially the leg d, acts as a dog (refer to the explanation for A2 in Figure 6), and the crane body has to be made that much stronger, which increases the weight of the crane body. The hull structure also had to be large and heavy, which was a drawback.

To explain this mechanical relationship with reference to Figure 2, a horizontal force H acts on the center of gravity G due to the pendulum movement of radius r due to the rolling of the ship's chair, and this horizontal force H is supported by - on one side of the lower part of the leg d. be done.

Then, a bending moment is generated in the leg d and the girder e due to the support reaction force at the lower part of the leg d, and at the joint between the leg d and the girder e, the bending moment is expressed as follows, where h is the height of the leg d. M1=-Xh.

The purpose of this invention is to reduce the above-mentioned bending moment caused by horizontal force, thereby reducing the weight of the gantry crane itself and the hull structure. It is characterized by providing a fixing means that can engage with a bracket erected on the deck at a portion near the height of the center of gravity.

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

In Figures 3 and 4, 1 is a portal crane, 2 is a leg,
3 is a fixing device attached to the arbitrary height position X of the leg 2, 4 is the girder, 5 is a bracket provided on the deck 6 of the ship S, h is the height of the leg 2, and y is the connection between the leg 2 and the girder 4. G indicates the center of gravity position.

With such a configuration, a lateral horizontal force H acts on the center of gravity position G due to rolling of the ship S, but the horizontal force H is supported by the fixing device 3 by -.

Therefore, the maximum bending moment generated in the leg 2 and the girder 4 due to the horizontal reaction force in the support device 3 is M2-1×
y (see Figure 4).

However, since h = x + y and h>y,
The bending moment M2 in the present invention and the bending moment M1 in the conventional device are obviously M2<Ml, and it can be seen that the bending moment generated in the legs 2 and the girder 4 is small in the case of the fixing device of the present invention.

According to the above considerations, as long as only the bending moment is considered, if the crane is fixed with a bracket at the same height as the girder, the bending moment will be zero, but in this case the bracket would be too large and would not be suitable for placement. In some cases, it is practical to fix the crane at a height near the center of gravity of the crane or near the center of the height of the legs.

It goes without saying that suitable means such as wire ropes, screws, pins, etc. may be used as the fixing device of the present invention, and that various other changes may be made without departing from the gist of the vehicle invention.

Since the fixing device for a marine gantry crane of the present invention has the above-described configuration, the strength of the crane body, particularly the strength of the legs, can be reduced, and the weight can be reduced.

Furthermore, since the weight of the crane body can be reduced, the output of the travel motor of the gantry crane can also be reduced, making it more economical.

Furthermore, from the perspective of the ship, a bracket is required to secure the fixing device on the ship, but since it is only necessary to install the securing device, it is not necessary to install a structure such as a portal crane on the deck. This reduction in weight also reduces the weight of the reinforcing material under the rail, which is very advantageous when considering the entire ship.

[Brief explanation of drawings]

Figure 1 is an overall view of the marine gantry crane, Figure 2 is an explanatory diagram of the bending moment generated in the legs and girder when the lower part of the marine gantry crane is fixed and supported, and Figure 3 is the marine gate of the present invention. An explanatory diagram of the fixing device of the type crane, Figure 4 is the third
When the gantry crane is fixed using the fixing device shown in the figure,
Figures 5 and 6, explanatory diagrams of the bending moment generated in the legs and girder, show that even if the crane body is strong enough to handle heavy loads, it cannot withstand the bending moment caused by rolling, etc. Figure 5 A2 and C are explanatory diagrams of the bending moment generated in the crane body during normal cargo handling work, and Figure 6 A2 and C are rolling moments when no cargo handling work is being carried out. It is an explanatory view of the bending moment which occurs in a crane main body at times. 1 is a portal crane, 2 is a leg, 3 is a fixing device, and 4 is a girder.

Claims (1)

[Scope of utility model registration request] A fixing device for a marine gantry crane, characterized in that a fixing means capable of engaging with a bracket erected on a deck is provided at a portion of the leg of the gantry crane near the height of the center of gravity of the crane. .