JPS6156156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mast arrangement for a forklift truck.

In particular, the present invention relates to a mast device with good forward visibility and a free lift function.

Conventionally, only when the lift cylinder has extended to a certain extent, one end contacts the lower end of the outer mast and the other end contacts the upper end of the inner mast, and then it extends while pushing up the inner mast, and when one end of the lift cylinder is free. teeth,
Forks that are provided with a free lift function are known (see Japanese Patent Application Laid-open No. 52-61057 and Japanese Utility Model Application No. 53-18774).

However, in cases where the lift cylinder is placed on the back of the mast frame in order to improve forward visibility, the upper end of the cylinder is fixed to the inner mast and the lower end of the cylinder is fixed to the outer mast. The mast was raised and had no free lift condition. The present invention has a structure in which the lower part of the lift cylinder is slidably locked to the outer mast and the lower chain wheel is interlocked, so that it has a free lift function. I will explain about it.

Fig. 1 shows a known mast device for a forklift equipped with a free lift function, in which 1 is an outer mast, 2 is an outer mast;
is the inner mast. 3 is a carriage, to which forks 4 and 4' are attached. Reference numeral 5 denotes a mast extension hydraulic cylinder, which is disposed approximately in front of the operator's position between both frames of the mast installed in front of the operator's position (not shown). Therefore, since the hydraulic cylinder 5 always blocks a portion of the operator's forward field of vision, it is difficult to see the tips of the forks 4, 4' when handling a load. This not only reduces cargo handling efficiency but also reduces safety during travel and cargo handling.

Figures 2 and 3 show a known example with good forward visibility, in which mast extension hydraulic cylinders 5 and 5' are arranged on the back of the mast frame, and the lower ends of these hydraulic cylinders 5 and 5' are connected to the outer mast. 1, and its upper end is connected to the inner mast 2. Furthermore, one end of the cable members 9, 9' is attached to the carriage 3.
The other end is connected to the cross member of the outer mast 1 via upper chain wheels 10, 10' fixed to the inner mast 2. Therefore, in terms of forward visibility, it is better than the case shown in Fig. 1, but due to its structure, when the hydraulic cylinders 5, 5' extend, the inner mast 2 immediately rises, so it does not have a free lift function, and the fork 4, 4' when traveling with the mast device slightly elevated above the ground surface, the total height of the mast device increases, making it unsuitable for work in locations with height restrictions.

As described above, in conventional forklifts having a free lift function, forward visibility is obstructed, and the free lift function has to be sacrificed in order to improve forward visibility.

The present invention has been devised to eliminate the drawbacks of the above-mentioned known structures, and will be described below with reference to FIG. 4 and subsequent figures. In the figure, 1 is an outer mast, and 2 is an inner mast, which is slidably inserted into the outer mast 1.

Reference numeral 3 designates a carriage slidably inserted into the inner mast 2, and 4 and 4' designate forks attached to the carriage 3. Reference numerals 5 and 5' denote hydraulic cylinders for mast extension, and one on each of the left and right sides is arranged on the back side of the frame consisting of the outer mast 1 and the inner mast 2. Telescopic rod 5a of hydraulic cylinder 5, 5',
The upper end of 5'a is connected to the inner mast 2 via a cross member 2a on which upper chain wheels 10, 10' are supported.

Further, the lower portions of the hydraulic cylinders 5, 5' are interconnected by a chain wheel support 7 on which lower chain wheels 6, 6' are supported. Further, the chain wheel support 7 is guided by guide bars 8, 8' vertically provided at the lower end cross member 1a of the outer mast 1, so that it can slide up and down. 1c is the upper cross member of the outer mast 1, and the inner mast 2 supports the upper chain wheels 10, 10'.
The lower end cross member 1a of the outer mast 1 serves as a stopper to limit the downward movement of the chain wheel support 7. That is, the lower end cross member 1a of the outer mast 1 engages with the chain wheel support 7 to limit its downward movement when the telescopic rods 5a, 5'a of the cylinders 5, 5' are extended, and the upper cross member 1c Telescopic rod 5a, 5'a
The cross member 2a of the inner mast 2 is engaged with the cross member 2a of the inner mast 2 to limit its downward movement when the inner mast 2 is shortened.

9 and 9' are cable bodies, one end of which is connected to the carriage 3.
The other end connects to the lower chain wheels 6, 6' provided at the bottom of the hydraulic cylinders 5, 5' via the upper chain wheels 10, 10' attached to the inner mast 2 midway and the chain wheel support 7. It is connected to the lower cross member 1b of the outer mast 1 via the outer mast 1.

The mast device constructed as described above operates as follows (see FIGS. 6 to 9).

(1) The hydraulic cylinders 5, 5' are connected to a hydraulic drive source via a hydraulic switching valve (not shown), but are in the state shown in FIG. 6 when no pressure oil is supplied.

(2) Now, pressure oil is supplied to the hydraulic cylinder 5,
5' extends by a distance l, the upper ends of the hydraulic cylinders 5, 5' and the inner mast 2 to which the upper ends are connected do not change their positions, but the lower ends of the hydraulic cylinders move downward l (FIG. 7). At the same time, lower chain wheels 6, 6' are attached to the lower part of the hydraulic cylinders 5, 5' via a chain wheel support 7.
Press down by l. As a result, the cord bodies 9, 9'
The carriage 3 suspended by the 2 l
only rises.

(3) The hydraulic cylinders 5, 5' are further extended, and the lower end of the hydraulic cylinder or chain wheel support 7 is connected to the outer mast 1.
above until it comes into contact with the lower end cross member 1a.
Continuing the operation (2), that is, the free lift operation, raises the carriage 3 by twice as much (8th
figure).

(4) When the hydraulic cylinders 5 and 5' further extend,
The lower ends of the hydraulic cylinders 5, 5' and the lower chain wheels 6, 6' provided at the bottom of the hydraulic cylinders 5, 5' are restricted in their downward movement by the lower end cross member 1a of the outer mast 1, without changing their positions. The upper ends of the hydraulic cylinders 5, 5' push up the inner mast 2. At the same time, the upper chain wheels 10, 10' attached to the cross member 2a of the inner mast 2 are moved upward. As a result, the carriage 3 suspended by the cables 9 and 9' is moved by the hydraulic cylinders 5 and 9'.
5' continues to rise at a rate twice the amount of extension, and finally reaches the end of the stroke of the hydraulic cylinder (FIG. 9).

(5) When the hydraulic cylinders 5, 5' are retracted again, the inner mast 2 lowers, its cross member 2a engages with the upper cross member 1c of the outer mast 1, restricting its downward movement, and then the chain wheel support The body 7 rises and returns to the position shown in FIG.

As described above, according to the present invention, (1) Since the mast device is equipped with a free lift function, it is possible to travel and carry out transportation work while the overall height of the mast device remains at a minimum. This makes it extremely suitable for use indoors where height is restricted.

(2) In addition, in order to provide a free lift function, the lower chain wheel, chain wheel support, and guide bar are placed inside the mast frame, but they are all located at the bottom of the mast device at a position lower than the cockpit. Since the fork tip is located in the driver's seat, it does not obstruct the forward view even when checking the tip of the fork from the cockpit, and provides an extremely good forward view compared to known devices.
Therefore, it becomes easier to check the load and the tip of the fork during cargo handling operations, greatly improving work efficiency through smooth cargo handling, and reducing blind spots for the operator, greatly improving safety during driving and cargo handling. It has the advantage of

[Brief explanation of the drawing]

FIG. 1 is a plan view of a known mast device. FIG. 2 is a plan view of another known mast device. Figure 3 is also a front view. FIG. 4 is a front view of the mast device according to the present invention. FIG. 5 is a sectional view taken along the line V-V in FIG. 4. Figure 6~
Figure 9 is an explanatory diagram of the work of the present invention, Figure 6 is the state without pressure oil applied, Figure 7 is the state during free lift, Figure 8 is the end point state of free lift, and Figure 9 is the maximum lift of the fork. Indicates the condition. In the figure; 1...Outer mast, 1a...Lower end cross member, 1b...Lower cross member, 1
c... Upper cross member, 2... Inner mast, 2
a... Cross member (of the inner mast), 3... Carriage, 4, 4'... Fork, 5, 5'... Hydraulic cylinder, 5a, 5'a... Telescopic rod (of the hydraulic cylinder), 6, 6'...Lower chain wheel, 7,7
a... Chain wheel support, 8, 8'... Guide bar,
9, 9'... cable body, 10, 10'... upper chain wheel.

Claims (1)

[Claims] 1 Cross members 2a are arranged in pairs on the left and right on the back side of a mast frame body consisting of an outer mast 1 and an inner mast 2 that is slidable relative to the outer mast 1, and the upper part supports the upper chain wheels 10, 10'. Inner mast 2 through
Hydraulic cylinders 5, 5 are connected to each other by a chain wheel support 7 whose lower part is slidably attached to the lower end cross member 1a of the outer mast 1 and supports lower chain wheels 6, 6'. ', and a pair of left and right cable members 9, 9' connected at one end to the carriage 3 and at the other end to the lower cross member 1b of the outer mast 1 via the upper chain wheels 10, 10' and the lower chain wheels 6, 6'.
The lower end cross member 1a of the outer mast 1 consists of telescopic rods 5a,
The upper cross member 1c engages with the cross member 2a of the inner mast 2 when the telescopic rods 5a, 5'a are shortened, and engages with the chain wheel support 7 to limit its downward movement when the telescopic rods 5'a are extended. A mast device for a forklift truck, wherein the mast device is configured to limit downward movement of a forklift truck.