JPS6219359B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to automation of fork positioning in a forklift, and more particularly to an apparatus for detecting pallet gaps and positioning fork insertion.

Conventionally, when automating cargo handling work in warehouses, etc., a rack system was used to load and unload cargo into racks at a predetermined height according to a predetermined program. In addition to being expensive, the utilization rate (occupancy rate) of the warehouse is low.
Moreover, there was the inconvenience that a height detection device had to be attached to the rack, or a height signal had to be given to the program in advance.

The above-mentioned disadvantages do not occur in the method of directly stacking cargo on pallets without using racks, but the height changes depending on the size and shape of the cargo, and the height of the cargo changes due to the weight of the cargo and pallets being stacked. Therefore, when performing automatic cargo handling using a forklift, it is necessary to accurately detect the insertion position of the fork.

An object of the present invention is to provide an automatic fork positioning device for a forklift that can efficiently carry out cargo handling operations in the latter case without being affected by the above-mentioned deformation of the cargo height.

Therefore, in the present invention, an optical sensor is provided at the tip of the fork to detect light reflected by an object in front, and the height of the fork is adjusted to reach the upper and lower edges of the gap between the pallets based on the detection signal of the optical sensor. At the same time, the height position of the fork at each detection time is memorized, and the average of both stored values is calculated, and the average value is set as the target value, and the height of the fork is determined as an abbreviation of the gap between the pallets. A control circuit that operates to adjust the center position is provided.

Hereinafter, the present invention will be explained in detail with reference to the illustrated embodiments.

In Fig. 1, a light emitting element 3 and a light receiving element 3' are provided at the tip of a fork 2 of a forklift 1, and a position sensor that converts the height of the fork into an electrical signal is installed near the top of the mast. A device, for example a potentiometer 4, is attached.
An actuator 6 is attached to the lift lever 5 of the forklift.
moves the lift up and down according to a control signal given from the outside. Reference numeral 7 indicates a pallet, and 8 indicates a load placed on the pallet.

The forklift 1 is guided by a signal from a guide cable (not shown), moves forward along a predetermined lane, and stops once the tip of the fork 2 is located 20 to 40 cm in front of the load. Therefore, if light is emitted from the light emitting element 3 and reflected light generated when it hits the upper or lower edge of the pallet 7 or the cargo is detected by the light receiving element 3', it can be determined that something is present. When the light enters the gap 7' in the pallet 7, there is no reflected light, so by detecting this with the light receiving element 3', the gap 7' in the pallet can be known. Further, the height position of the fork 2 at that time can be taken out as an electric signal using the potentiometer 4.

The positioning device of the present invention is configured to determine the insertion position of the fork based on this electrical signal and perform positioning, and the details thereof will be explained below with reference to FIG. 2.

In the figure, the output of an oscillation circuit 10 is modulated by a modulation circuit 11 and then inputted to the light emitting element 3 attached to the tip of the fork.
transmits modulated light toward the package 8 or pallet 7. The light reflected by the object is received by the light receiving element 3', amplified and waveform-shaped by the amplifier circuit 12 and filter 13, and then compared with a reference level by the comparison circuit 14. Now, control signal UON is applied to actuator 6.
When the fork 2 is raised, the fork position is converted into an electrical signal by the potentiometer 4 and guided to the sample and hold circuits 21 and 22 and the comparison circuit 23.

When the fork 2 gradually rises and reaches the lower edge of the gap between the pallets 7, the reflected light to the light receiving element 3' disappears, and the comparison circuit 14 generates a gap detection output. This detection output is sample pulse SP ₁
As a result, the potentiometer output voltage V L at that moment is input to the sample and hold circuit 21 , and thereby the potentiometer output voltage V _L at that moment is held in the hold circuit 21 . When the fork 2 further ascends and reaches the upper edge of the gap (the upper end surface of the pallet 7), the reflected light is again given to the light receiving element 3', so the comparator circuit 14 detects this and outputs a sample pulse _SP2 , A hold circuit 22 holds the potentiometer output voltage (V _H ) at that moment. The holding voltages (V _{L ) and (V H )} of these sample and hold circuits 21 and 22, which represent the height positions of the lower end surface and the upper end surface of the pallet 7, are input to the average value circuit 24 and are calculated by the average value circuit 24. Then their average value (V _L +V
_H )/2 is calculated. The average value representing the center height position of the pallet gap 7' is then applied to the comparison circuit 23 as a target value for fork positioning and compared with the output of the potentiometer 4.
Then, a control signal A is given to the actuator 6 so that the difference becomes zero, and the fork is thereby positioned.

In addition, in the above explanation, an example was described in which a combination of a light-emitting element and a light-receiving element is used as a detection device.
This may be configured with an ultrasonic switch, a non-contact type proximity switch, or the like. Further, the potentiometer may also be replaced with a differential transformer or the like.

As described above, the present invention attaches a sensor for detecting the presence or absence of an object in front of the fork of a forklift that performs cargo handling work, and thereby automatically detects the gap between pallets and determines the insertion position of the fork. The height or shape of the cargo may change,
Even if the load is deformed due to the weight of the pallet itself, the forks can be positioned accurately.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the implementation state of a fork positioning device according to the present invention, and FIG. 2 is a main part block diagram showing an embodiment of the present invention. 1...forklift, 2...fork, 3,
3'... Light emitting element, light receiving element, 4... Potentiometer, 5... Lift lever, 6... Actuator, 7... Pallet, 8... Baggage, 10... Oscillation circuit, 11... Modulation circuit, 14, 23... Comparison circuit, 21, 22... Sample hold circuit, 2
4...Average value circuit.

Claims (1)

[Claims] 1. In a forklift that performs cargo handling work by inserting a fork into a gap between pallets loaded with cargo, a sensor is provided at the tip of the fork to detect the presence or absence of an object in front, and the current height of the fork is a device for detecting a position, and detects, based on the output of the sensor, when the height of the fork reaches the upper edge and the lower edge of the gap between the pallets, and determines the height of the fork at each detection time. A fork characterized by comprising a circuit that stores each position, calculates an average of both stored values, and uses the average value as a target value to control the height of the fork to match approximately the center position of the gap between the pallets. Lift fork automatic positioning device.