JPS6211919Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement of a so-called full-free mast that prevents the mast from rising while the fork rises to the mast height, and in particular, to one that prevents shock during descent. .

In places where there are height restrictions, such as onboard ships or in warehouses,
Instead of a standard mast in which the fork and mast rise gradually, a full-free mast in which only the fork rises to the mast height is often used.

Full-free masts usually come in two-stage or three-stage mast types, and often have two lift cylinders, one for the mast and one for the fork.

6 to 9 illustrate a full-free two-stage mast 20' which is a full-free mast 20. In each figure, 21 is a fixed mast, and 22 is a movable mast that can be raised and lowered. The mast, 23 is an elevating body (lift bracket and finger bar) that can move along the movable mast 22, 24 is a left and right fork suspended from the elevating body 23, and 25 is a fixed mast 21
and a mast lift cylinder interposed between the moving mast 22, 26 a fork lift cylinder attached to the moving mast 22, 27 a sheave shafted at the tip of the piston rod of the fork lift cylinder 26, and 28 a fork lift cylinder 26. Alternatively, a lift chain having one end fixed to the moving mast 22 and the other end wrapped around the sheave 27 and fixed to the elevating body 23, P is a pump, V is a switching valve, T is a tank, and F and V are flowcharts. Each control valve is shown.

The mast lift cylinder 25 and the fork lift cylinder 26 each have their own tail chambers 2.
9 and 30 are connected to the flow control valves F and V through conduits, that is, oil pipes 31 and 32, and the stroke of the fork lift cylinder 26 is approximately half that of the mast lift cylinder, and its piston pressure receiving area is larger than that of the mast lift cylinder. The fork lift cylinder 26 is first extended, and when it is fully extended, the mast lift cylinder 25 is extended.

Conversely, when shortening, the fork lift cylinder 26 is shortened after the mast lift cylinder 25 is shortened.

FIG. 10 illustrates a full-free three-stage mast 20'' which is a full-free mast 20, which has two moving masts, a first moving mast 22a
A mast lift cylinder 25 is interposed between the fixed mast 21 and the second movable mast 22.
A fork lift cylinder 26 is attached to b.

A sheave 33 is installed in the upper part of the first moving mast 22a, and after the other end of another lift chain 34 whose one end is fixed to the fixed mast 21 is hung around the sheave 33, the second moving mast 22a is attached. It is fastened to the lower part of 22b.

The three-stage full-free mast 20'' functions in the same manner as the two-stage full-free mast 20', except that there are two movable masts that move up and down in conjunction with each other.

However, such a full-free two-stage mast 2
In the case of a so-called full-free mast 20 such as a full-free three-stage mast 20'' or a full-free three-stage mast 20'', when the fork is lowered from the maximum lifting height position, the mast lift cylinder 25 first shortens and reaches the stroke end, as described above. Since the lift cylinder 26 for the fork begins to shorten only after reaching the fork 24, the fork 24 will have to temporarily stop in the middle of its descent.

However, this temporary stop is accompanied by a so-called shock, and when a load is placed on the fork 24, the load is likely to collapse due to this shock, causing the load to fall and cause damage to the load itself. It was very dangerous because it could get damaged or fall onto other objects, causing damage.

This invention was devised in view of the problems mentioned above and to solve them.The purpose of this invention is to eliminate the shock when the fork descends, thereby preventing cargo collapse and accidents caused by this. To provide a shock prevention device when a full free mast is lowered, which allows cargo handling work to be carried out safely.

The basic structure of the present invention is a fixed mast, a movable mast that can be raised and lowered with respect to the fixed mast, an elevating body that can move along the movable mast, a fork suspended from the elevating body, and a movable mast that can be moved up and down with respect to the fixed mast. Each includes a mast lift cylinder for driving the moving mast up and down, and a fork lift cylinder for driving the lifting body and fork up and down with respect to the moving mast, and each tail chamber of the mast lift cylinder and the fork lift cylinder is In a fully free mast connected to a pump via a flow control valve and a switching valve, only the descending movement of the mast lift cylinder is suppressed in the passage between the tail chamber of the mast lift cylinder and the flow control valve. The feature lies in that a control valve is provided to allow the lift cylinder for the fork and the fork cylinder for the mast to shorten almost simultaneously.

In other words, the control valve installed on the mast lift cylinder side suppresses the shortening of the mast lift cylinder so that it shortens almost simultaneously with the fork lift cylinder, eliminating the conventional switching shortening operation. This prevents shocks caused by

Of course, when expanding, it functions in the same manner as before.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of embodiments of the present invention will be explained below based on the drawings.

FIG. 1 is a schematic side view showing a state in which the descending shock prevention device according to the present invention is applied to a full-free two-stage mast at the maximum lifting height. FIG. 2 is a similar view showing the fork and the moving mast in the process of being lowered together. FIG. 3 is a similar view of the same device at minimum lift.

FIG. 4 is a longitudinal sectional side view of the main parts showing the specific structure and hydraulic circuit of the control valve. FIG. 5 is a longitudinal sectional side view of only the main parts showing the operating state of the control valve when the mast lift cylinder is shortened.

In each of the above figures, parts and parts that are the same as those of the conventional device (FIGS. 6 to 9) are given the same reference numerals, and their details are omitted.

The descending shock prevention device 1 according to the present invention is applied to, for example, a full-free two-stage mast 20', and the control valve 2 is installed in the conduit 31 between the tail chamber 29 of the mast lift cylinder 25 and the flow control valves F and V. In this embodiment, a case is illustrated in which the mast lift cylinder 25 is disposed adjacent to the lower part of the tail chamber 29 of the mast lift cylinder 25.

As shown in FIGS. 4 and 5, the main parts of the control valve 2 include a valve body 3, a valve body 4, and a spring 5.

The valve box 3 is provided with a lumen 6 that is open at one end, and the open portion of the lumen 6 is closed by a nipple 7. In this embodiment, since the control valve 2 is provided in the tail portion of the mast lift cylinder 25, it also serves as the cylinder tube of this, and the inner cavity 6 and the tail chamber 29 communicate with each other through the communication hole 8. In addition, a through hole 9 that reaches the inner cavity 6 is bored inside the nipple 7.

The valve body 3 has a cup shape consisting of a cylindrical wall 10 and a side wall 11, and is slidably fitted into the inner cavity 6, and an appropriate number of first through holes 12 are bored in the cylindrical wall 10. In addition, a single second through hole 13 is bored in the side wall 11.

A spring 4 is interposed between the valve body 4 and the nipple 5, and is biased so that the valve body 4 is separated from the nipple 5.

Note that the communication hole 8, the conduction hole 9, the first communication hole 12 of the control valve 2, and the tail communication hole 35 of the fork lift cylinder 26 have the same diameter (the first communication hole 12 may have a larger diameter), and the second The through hole 13 is set to have a smaller diameter than each of the holes.

In such a configuration, the operation will be explained next.

When raising the fork 24 from the minimum elevation position shown in FIG. 3, the switching valve V is switched from the neutral position shown in FIG. 4 to the left-hand position.

Then, the oil discharged from the pump P is divided into two parts through the switching valve V and the flow control valves F and V, one of which reaches the tail chamber 30 of the fork lift cylinder 26 through the conduit 32, and the other which is controlled. The tail chamber 29 of the mast lift cylinder 25 is reached via a conduit 31 with a valve 2 .

In this case, the control valve 2 is operated to the left as shown in FIG. 4, and only the first passage hole 12 of the valve body 4 communicates with the tail chamber 29.

The first passage hole 12, the communication hole 8, the conduction hole 9, and the tail passage hole 35 have the same diameter (the first passage hole 12 may have a larger diameter), so the piston pressure receiving area is the same as before. The fork lift cylinder 26, which has a larger size, begins to extend first.

When the lift cylinder 26 finishes extending, the pressure oil in the tail chamber 29 of the mast lift cylinder 25 increases, causing it to extend and reach the maximum lift position shown in FIG.

Therefore, the mast lift cylinder 25 does not extend until the fork lift cylinder 26 finishes extending, and during that time only the fork 24 rises, resulting in a so-called full free lift state.

Conversely, when lowering the fork 24 from the maximum height position shown in FIG. 1, the switching valve V is switched to the right position in FIG. 4.

In this case, the valve body 4 of the control valve 2 moves to the right as shown in FIG. 5 simultaneously with switching of the switching valve V, and the tail chamber 29
The return oil is squeezed out through the small diameter second through hole 13.

For this reason, normally the fork lift cylinder 26, which has a large piston pressure receiving area, would not shorten, but the mast lift cylinder 25 starts to shorten almost at the same time by the amount that its return oil is throttled by the control valve 2.

In other words, the mast and fork lift cylinders 25 and 26 begin to shorten almost simultaneously, and synchronously shorten as shown in FIG. 2 until they reach the minimum lift position shown in FIG. 3.

Therefore, as in the past, the mast lift cylinder 2
5 and fork lift cylinder 26 do not operate selectively, but operate simultaneously, so there is no shock during switching.

In this embodiment, the control valve 2 is provided integrally with the tail portion of the mast lift cylinder 25, but it is provided separately and in the conduit 31 between the tail chamber 29 and the flow control valves F and V. It is also possible to intervene.

Further, the shock prevention device 1 at the time of descent according to the present invention can be applied to a full-free three-stage mast using lift cylinders 25 and 26 for a single mast and fork, and a full-free multi-stage mast with more than that. Needless to say.

As described above, according to the present invention, a control valve that throttles only the return oil is provided on the mast lift cylinder side, and this and the fork lift cylinder are lowered almost at the same time. This eliminates the need for the lift cylinders for the fork and the fork to operate alternately, and the shock that occurs when switching can be completely eliminated.

Therefore, the cargo on the fork does not collapse during the descent, and accidents such as falling due to this can be prevented, and cargo handling work can be carried out extremely safely.

The configuration is simple as only a control valve is provided on the mast lift cylinder side, and
Since the structure of the control valve itself is simple, it does not require much cost and can be implemented immediately.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the state at maximum lifting height when the descending shock prevention device according to the present invention is applied to a full-free two-stage mast. FIG. 2 is a similar diagram showing the state during descent. FIG. 3 is a similar diagram showing the state at the minimum lifting height. FIG. 4 is a longitudinal sectional side view of the main parts showing the structure and hydraulic circuit of the control valve. FIG. 5 is a longitudinal sectional side view of only the main parts showing the operating state of the control valve. 6 to 9 are schematic side views showing the structure and operation sequence of a conventional full-free two-stage mast. FIG. 10 is a schematic side view showing the structure of a conventional full-free three-stage mast. 1... Shock prevention device during descent, 2... Control valve, 20... Full free mast, 21... Fixed mast, 22... Moving mast, 23... Elevating body, 2
4... Fork, 25... Lift cylinder for mast, 26... Lift cylinder for fork, 29...
...Tail chamber, 31...Conduit, P...Pump, V...
...Switching valve, F/V...Flow control valve.

Claims (1)

[Scope of utility model registration request] A fixed mast 21 , a movable mast 22 that can be raised and lowered relative to the fixed mast 21 , an elevating body 23 that can move along the movable mast 22 , a fork 24 suspended from the elevating body 23 , and a movable mast 22 that is movable with respect to the fixed mast 21 22, and a fork lift cylinder 26 that drives the elevating body 23 and fork 24 up and down relative to the moving mast 22. In a full free mast in which each of the 26 tail chambers 29 and 30 is connected to the pump P via the flow control valves F and V and the switching valve V, the tail chamber 29 of the mast lift cylinder 25 and the flow control valve F are connected to each other. - A control valve 2 that suppresses only the descending movement of the mast lift cylinder 25 is interposed in the conduit 31 with the fork lift cylinder 26.
A shock prevention device when a full-free mast is lowered, characterized in that the mast lift cylinder 25 and the mast lift cylinder 25 are shortened substantially simultaneously.