JP3304279B2 - Forklift lift control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for regulating the lift of a forklift at a set height.

[0002]

2. Description of the Related Art Conventionally, a lift control device mounted on a forklift used for loading and unloading work under an overhead wire is provided with an electromagnetic hydraulic switching valve for controlling the supply of hydraulic pressure to a hydraulic circuit of a lift cylinder, and a lift limit sensor is provided on an outer mast. In accordance with the signals of the provided service automatic stop proximity switch and emergency stop proximity switch, the electromagnetic hydraulic switching valve is operated to perform an electrical control for stopping the lift cylinder, and a mechanical stop when the electrical control does not operate. It is configured in combination with a fixed stopper. With respect to the control in the cargo handling work, the control according to the hydraulic circuit diagram shown in FIG. 6 and the flowcharts shown in FIGS. 7, 8, and 9 are general.

FIG. 6 shows a hydraulic circuit diagram relating to a lift cylinder. The hydraulic pressure sent from an oil tank 20 by a gear pump 17 passes through a control valve 16 to an electromagnetic hydraulic switching valve 8 which constitutes a hydraulic block 19. It is connected to a check valve 18.

When the electromagnetic hydraulic switching valve 8 is excited,
As operated by the control valve 16, hydraulic pressure is supplied to the lift cylinder 15, and the piston pushes up the lift bracket 22. Then, when approaching the range of the lift stop height, the limit switch 6 for return, the limit switch 5 for normal automatic stop, and the limit switch 4 for emergency stop which constitute the lift limit sensor 2 are engaged in this order.

[0005] When the electromagnetic hydraulic switching valve 8 is demagnetized, supply to the hydraulic lift cylinder 15 is stopped, the hydraulic circuit is blocked, and the lift cylinder 15 is stopped. Here, the operator performs a lowering operation with the control valve 16. That is, due to the weight applied to the piston, the hydraulic pressure is supplied from the lift cylinder 15 to the check valve 1.
8 and return to the oil tank 20.

FIGS. 7, 8 and 9 show flowcharts of control for loading and unloading operations of a forklift divided into three parts A, B and C, respectively, for explaining the operation of the lifting height regulating device.
FIG. 7 shows, as a control flowchart A, a control in a case where the lifting height regulating device is set as the overhead loading and unloading operation, and the overhead loading and unloading operation is performed in a normal state.

[0007] Switching between loading and unloading work under overhead lines and general work is set by a key switch in step S101. When the key switch is set to "OFF", in step S102, the changeover switch 6 is operated to confirm that the fixed stopper is set to the lifting stop position. From this state, the cargo work under the overhead wire is started. Start.

In step S103, when the operator is operating the control valve 16 to perform the ascent operation, step S1 is executed.
At 05, when the normal automatic stop proximity switch 4 is operated,
The electromagnetic hydraulic switching valve 8 is demagnetized, the hydraulic circuit is blocked, and the ascent / stop state is set in step S106. Then, when the operator performs the descending operation in step S107,
In step S109, the return limit switch 5 operates,
The control circuit returns.

FIG. 8 is a flowchart B of the control, in which the return limit switch 5 is not operated in step S109 in the unloading work under the overhead line, and in step S105.
This shows the control when the normal automatic stop proximity switch 4 does not operate and the emergency stop proximity switch 3 operates, and the abnormality processing.

If the return limit switch 5 does not operate in step S109, the return operation cannot be performed again even if the fork is lowered.
Inspection is required. In step S103, when the operator performs the raising operation with the control valve 16, in step S105, if the normal automatic stop proximity switch 4 does not operate, the process proceeds to step S301, and the raising continues.
When the emergency stop proximity switch 3 is operated in step S302, the ascending emergency stop is performed in step S303.
In step S104, the emergency lights up and the alarm buzzer operates. Then, when the operator performs a descending operation in step S305, the return limit switch 5 is operated and the control circuit is restored. In this case, in step S308, an inspection for restoring the abnormality of the normal automatic stop proximity switch 4 is necessary. Becomes

FIG. 9 shows, as a control flowchart C, a control in the abnormal state where the normal automatic stop proximity switch 4 does not operate in step S105 and the emergency stop proximity switch 3 does not operate in step S302. Things. In this case, the electrical stop does not operate, and during the ascent operation, the lift bracket 22 continues to ascend, and step S
At 402, the fixed stopper 1
The function of mechanically stopping the lift bracket 22 by bringing the lift bracket 22 into contact therewith is exhibited.
Then, the operator switches to the descending operation to stop the cargo handling work, and it is necessary to perform an inspection to recover the abnormality of the operation of the normal automatic stop proximity switch 4 and the operation of the emergency stop proximity switch 3.

FIG. 9 also shows the control in the case of the general cargo handling work, not the cargo handling work under the overhead line. That is, under the condition that the key switch is turned on in step S101 and the fixed stopper is released in step S102, the electromagnetic hydraulic switching valve 8 is directly excited in step S502, and the cargo handling is performed as a conventional general forklift. The work is ready to be performed.

As a conventional technique related to the fixed stopper, Japanese Patent Application Laid-Open No. H8-109000 is cited as a reference. The technology disclosed in this publication is provided with a stopper using a hydraulic cylinder, which is operated by hydraulic pressure used in the cargo handling device, and mechanically engages with a lift bracket by rotating the stopper from the driver's seat of the forklift. It is designed to regulate the lift, and a new point is that the mechanical stopper manually set by the operator who was used before that was improved.

[0014]

However, the technique disclosed in the above publication constitutes a circuit in which a hydraulic cylinder for setting / releasing a stopper is operated by a hydraulic pressure used for a cargo handling device of a forklift. Parts that can withstand high hydraulic pressure must be used, and large-scale equipment such as hydraulic cylinders, piping, and mounting brackets are expensive. However, problems arise in terms of work safety.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and in a forklift used for loading and unloading work under overhead lines, abuts a lift bracket which has reached a limit height. The outer mast is provided with a fixed stopper that can be positioned by switching to a position that does not come into contact with the position, and the electric motor and the power switch to mechanically limit or cancel the lifting height by operating the switch of the automatic stop position from the driver's seat In addition to the combination with the driving means, the switching predetermined position of the fixed stopper is detected and controlled by the position detecting means, and a combination of a chain and a sprocket or a combination of a belt and a pulley is used as the power driving means. And a proximity switch or a limit switch is used as the position detecting means.

With the above configuration, since the electric control is performed by using an electric motor, a switch, or the like as the power driving means for driving the fixed stopper, the mounting position of the electric motor can be easily changed and a hydraulic device is used. As compared with the case, since the control circuit only needs to pass through the electric wire harness, it is possible to make the control circuit compact. Therefore, as an effect described above, there is an advantage that a good visibility can be maintained for the operator in the driver seat.

Further, a predetermined position of the fixed stopper is switched by using a combination of a chain and a sprocket or a combination of a belt and a pulley as the power driving means.
Therefore, even when the lift bracket collides with the fixed stopper and receives an impact as compared with a type in which the power source is directly connected to the power source using gears, the power driving means serves as a buffer, and the power source is There is no need to receive mechanical shock, which is effective for protection.

Further, as the position detecting means, a sensor such as a proximity switch or a limit switch is used. Since the fixed stopper does not need to be positioned with high precision, the use of these sensors makes it possible to freely detect and set the position of the fixed stopper, facilitate the adjustment, and implement it at low cost.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Hereinafter, the hydraulic circuit diagram and the flow chart of the control of the cargo handling work other than the structure related to the position switching of the fixed stopper and the changeover switch have the same configuration as the prior art in the previous term. The description will be made with reference numerals.

FIG. 1 is a side view showing an embodiment in which a lifting height control device is attached to a cargo handling device of a forklift. FIGS. 2, 3 and 4 are side and top views showing details of a fixed stopper portion, respectively. It is a bottom view. In FIG. 1, when a lift bracket 22 to which a fork (not shown) is attached rises and approaches a limit height, a return limit 5 constituting a lift limit sensor 2, a normal automatic stop proximity switch 4, The emergency stop proximity switch 3 is mounted on the outer mast 21 in such an arrangement as to operate in this order. Finally, at the stop height, lift bracket 2 is attached to fixed stopper 1
2 are configured to abut and mechanically stop.

However, the return limit switch 6 does not operate in the direction in which the lift bracket 22 rises, but uses a limit switch that operates only in the direction in which the lift bracket 22 descends.

The members such as the bracket 13 related to the attachment of the fixed stopper 1 are manufactured with sufficient strength against the impact of the lift bracket 22 colliding at the maximum speed.

The fixed stopper 1 is driven by the electric motor 11, and by operating the changeover switch 6 of the control plate 7 provided in the driver's seat 23 of the cabin 24, the lift limit is set by the fixed stopper 1. And release can be implemented.

2, 3, and 4, the fixed stopper 1
The rotation of the electric motor 11 is transmitted to the combination of the chain 9 and the sprocket 10 or the power driving means 26 such as a belt and a pulley, and the switching between the set position and the release position is performed by the proximity switch 12 or the limit switch. This is possible by controlling the stop of the electric motor 11 with a signal detected by the position detecting means 25 using a sensor such as a switch.

In order to switch the fixed stopper 1, electric control is performed using the electric motor 11 for driving, the chain 9 and the sprocket 10, and the proximity switch 12 for position detection and control. And the control circuit only needs to pass through the wire harness as compared with the case where a hydraulic device is used, so that the control circuit can be made compact. Therefore, as an effect,
There is an advantage that a good visibility can be maintained for the operator in the driver's seat.

The lift bracket collides with the fixed stopper and receives a shock even when the stopper is switched using a hydraulic cylinder or when the power of the electric motor 11 is driven directly by using gears. In such a case, the chain 9 and the like used as the power drive means serve as a buffer, so that the power source does not need to receive a mechanical shock, which is effective for protection.

Since the fixed stopper 1 does not need to be positioned with high accuracy, by using the proximity switch 12 as the position detecting means 25, the position of the fixed stopper 1 can be freely detected and set, and adjustment is easy. And can be implemented at low cost.

FIG. 5 shows a control panel 7 provided in the driver's seat 25.
This embodiment shows an example of the arrangement of the switch 6 and the indicator lamp 14 for confirming the operation. The switch 6 and the indicator lamp 14 do not necessarily have to be provided on the same control panel 7. The type 8 is not particularly limited, and can be easily confirmed by turning on the indicator lamp 4 on the indicator lamp 14.

Switching between the underloading work and the general work is set by a key switch in step S101.
In the case of the undercarriage loading operation, when the key switch is set to "OFF", the changeover switch 6 is operated to drive to the fixed stopper 1 setting side in step S102.

For example, the changeover switch 6 of the fixed stopper 1
If the electric motor 11 is of the automatic reset type, if the electric motor 11 is continuously operated, the "set" indicator lamp 14 is turned on while the electric motor 11 is operating. After about one second, the fixed stopper 1 is set to the elevation stop position, the fixed switch 1 is set to the predetermined position by the proximity switch 12, and the indicator lamp 14 is turned off when the electric motor 11 automatically stops. From this state, the unloading work under the overhead wire starts. The control of the loading and unloading work under the overhead line is exactly the same as that of the above-described conventional technique, and thus the description thereof is omitted.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment to which a lift regulating device is attached.

FIG. 2 is a side view showing details of a fixed stopper portion.

FIG. 3 is a top view of a fixed stopper portion.

FIG. 4 is a bottom view of a fixed stopper driving portion.

FIG. 5 is an explanatory diagram of a changeover switch of the automatic stop device.

FIG. 6 is a hydraulic circuit diagram of a conventional lift cylinder.

FIG. 7 shows a flowchart A of control of a conventional cargo handling device.

FIG. 8 shows a flowchart B of control of a conventional cargo handling device.

FIG. 9 shows a flowchart C of control of a conventional cargo handling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed stopper 6 Changeover switch 9 Chain 10 Sprocket 11 Electric motor 12 Proximity switch 21 Outer master 22 Lift bracket 23 Driver's seat 25 Position detecting means 26 Power drive means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B66F 9/24

Claims (1)

(57) [Claims] In a forklift used for cargo handling work under an overhead wire, a lift bracket (2) reaching a limit height is provided.
The outer mast (21) is provided with a fixed stopper (1) that can be switched to a position where it comes into contact with 2) and a position where it does not come into contact with the outer mast (21).
By operating the changeover switch (6) of the automatic stop position from the driver's seat (23), switching to mechanically limit or cancel the lift is performed by a combination of the electric motor (11) and the power drive means (26). At the same time, the switching predetermined position of the fixed stopper (1) is
So as to detect and control by (25), said power drive hands
Combine chain (9) and sprocket (10) as step (26)
Or use a combination of belt and pulley.
Next, as the position detecting means (25), a proximity switch (12) or
Alternatively, a lift control device for a forklift, which uses a limit switch .