JPH08143296A - Fork height detector of forklift - Google Patents

Abstract

PURPOSE: To provide a fork height detector which can detect a fork height not gradually but continuously and does not requires a motive power source for detector drive. CONSTITUTION: A grooved wheel 8 and a detector 7 are fitted to the top and the bottom of the side of an outer mast 1, and between both, through a tension regulating member 9, a wire rope 10 is hung windingly and in a loop shape. As for the tension regulating member 9, it is integrally fitted to the tip portion of a support member 2c fixed at the proper place of an inner mast 2, and its side is of a U shape, and one end of the wise rope 10 is connected to the upper side and the other end is elastically connected to the lower side through a spring 9a. When the outer mast 2 ascends/descends, the wire rope 10 is moved, and a movement quantity is detected by means of the detector 7, and the height of a fork can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the height of a fork of an unmanned forklift capable of unmanned loading and unloading of goods in forklifts, particularly warehouses and factories.

[0002]

2. Description of the Related Art When carrying out a cargo handling operation with an unmanned forklift such as a forklift, for example, when carrying a load to a shelf having a predetermined height, or for discharging a load from a shelf having a predetermined height. Has a technical requirement that the fork must be stopped at a predetermined height during the lifting and lowering operation of the fork, and a device for detecting the height position of the fork is required.

Conventionally, as a device for detecting the fork height of a forklift, a plurality of limit switches are provided on the outer mast as disclosed in, for example, Japanese Utility Model Laid-Open No. 4-121997 and Japanese Utility Model Laid-Open No. 5-49793. Or a detector such as a proximity switch is provided, while a detection piece is attached to the fork or lift bracket, and a signal is output from the detector when the fork reaches an arbitrary height,
It is known that the fork height is detected.

According to this detecting means, however, the height of the fork can be detected corresponding to the installation position of the detector, but it is impossible to detect the height continuously,
When the position where the fork is stopped can be changed only by detecting in stages, the detector installation position must be changed, and when increasing the detection density, the number of detectors installed must be increased. There was a problem inevitably.

Further, as another detecting means, for example, as disclosed in Japanese Utility Model Publication No. 62-25520, Japanese Utility Model Publication No. 5-43034, etc., either the outer mast or the inner mast is lengthwise. It is also known that a rack or a chain is attached, and the other one is provided with a detection device including an encoder that emits a signal driven by a small gear such as a pinion or a chain wheel that meshes with the rack or the chain.

According to this detecting means, there is an advantage that the height of the fork can be continuously detected, but since there is always play between the rack or the chain and the gear that meshes with the rack, the positioning accuracy is deteriorated. Points remain.

Further, in order to prevent rattling due to transmission of a rack and pinion or a chain / chain wheel, one end of the wire wound around the rotary drum is connected to the elevating member and the other end of the wire is rotated along with the rotation of the rotary drum. It is also known that a position detecting device driven by a motor is provided.
No. 24699), as a power source for rewinding the wire, in other words, as a drive source of the detection device, it is necessary to incorporate a spiral spring in the rotating drum, which not only complicates the structure but also Since the tension in the unwinding direction is constantly applied, there is a problem that the durability of the wire is impaired.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to enable continuous detection instead of stepwise detection like a detection means such as a limit switch, and An object of the present invention is to provide a fork height detecting device which does not cause rattling like rack and pinion or chain and chain drive transmission, and which has a simple structure and does not require a power source for driving the detecting device.

[0009]

SUMMARY OF THE INVENTION The present invention provides means for solving the above-mentioned problems, in which a fork 6a is mounted on an inner mast 2 which is guided by an outer mast 1 and moves up and down via a lift bracket 5 which is vertically movable. , 6b are mounted on the forklift, the grooved wheel 8 and the detector 7 are mounted on the upper and lower sides of the outer mast 1, and the detector 7
Is an encoder 7a and a housing 7 that houses the encoder 7a
b, a wire drum 7c mounted coaxially with the encoder 7a, and a wire rope 10 is looped between the wire drum 7c and the grooved wheel 8 via a tension adjusting member 9 to adjust the tension. The member 9 has a base end portion fixed to a proper lower portion of the inner mast 2 and integrally attached to a tip end portion of a support member 2c protruding laterally of the outer mast 1, and has a shape having two upper and lower sides (side U-shape). Or one end of the wire rope 10 is connected to one of the upper and lower sides, and the other end of the wire rope 10 is elastically connected to the other through a spring 9a. The present invention provides a fork height detecting device characterized in that

[0010]

[Operation] When the inner mast 2 is moved up and down, the supporting member 2
The tension adjusting member 9 fixed to the tip of c moves up and down. Since the tension adjusting member 9 forms a part of the loop of the wire rope 10, the wire drum 7c around which the wire rope 10 is wound also rotates, and the encoder 7a responds to the movement amount of the inner mast 2. Generate a signal. Since the moving amount of the inner mast 2 and the moving amount of the forks 6a and 6b have a fixed relationship, the heights of the forks 6a and 6b at that time can be obtained by performing conversion in the arithmetic unit. Since the range in which the tension adjusting member 9 moves is on the common tangent line of the wire drum 7c and the grooved wheel 8, the loop length of the wire rope 10 is always constant, and a constant tension is applied to the wire rope 10 by the spring 9a. Since it is applied, the fork height is always kept at a constant tension at any time, and the wire rope 10 is prevented from being loosened or overtightened.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a general lifting device for a forklift, in which (a) is a side view and (b) is a front view. FIG. 2 is a detailed view of the detection device of the present invention, in which (a) is a side view,
(B) is a front view.

Prior to the description of the detection device of the present invention, a general fork lifting device will be described with reference to FIG. There are two types of forklifts that allow the lifting device for the fork to move back and forth, and those that cannot move.
Whichever type is used, a pair of left and right outer masts 1 that does not move in the vertical direction and a pair of left and right inner masts 2 that are guided by the outer mast 1 and move up and down in the vertical direction.
And an upper end of the inner mast 2 has a cylinder rod 3 of a lifting cylinder 3 fixed to the outer mast 1.
It is connected to the tip of a and can be moved up and down by hydraulic pressure.

4a and 4b are chains for raising and lowering the lift bracket 5, one end of which is fixed to the outer mast 1 and the other end of which is a chain wheel 2a and 2 at the upper end of the inner mast 2.
It is connected to the lift bracket 5 via b. The lift bracket 5 is supported on the front surface of the inner mast 2 so as to be able to move up and down, and has a pair of left and right forks 6a and 6b attached thereto.

When pressure oil is supplied to and discharged from the lifting cylinder 3, the cylinder rod 3a expands and contracts, the inner mast 2 moves up and down, and the chain wheels 2a, 2 at the upper end of the inner mast 2 are accordingly moved.
The lift bracket 5 is moved up and down by the chains 4a and 4b via b. Since one ends of the chains 4a and 4b are fixed to the outer mast 1, the movement amount of the lift bracket 5, that is, the movement amount of the forks 6a and 6b is twice the movement amount of the inner mast 2. The above is known.

An example of implementation of the present invention will be described below. A pair of plates 1a and 1b are attached to the side surface of the outer mast 1 at predetermined intervals in the vertical direction, and one plate (upper plate in this embodiment) 1a.
A grooved wheel 8 is attached to the plate, and a detector 7 is attached to the other plate (the lower plate in this embodiment) 1b.
The predetermined interval is the lifting stroke of the inner mast 2, in other words, the cylinder rod 3a of the lifting cylinder 3.
It has been set to the dimensions that add a slight allowance to the elastic stroke of.

The detector 7 comprises an encoder 7a, a housing 7b for accommodating the encoder 7a, and a wire drum 7c coaxially attached to the encoder 7a.
A wire rope 10 is wound in a loop shape between the c and the grooved wheel 8 via a tension adjusting member 9, and
It is wound several times on c.

The tension adjusting member 9 has a base end fixed to a proper lower portion of the inner mast 2 and integrally attached to a front end of a support member 2c which projects laterally from the outer mast 1. It has a U shape (or a square shape), and one of the upper and lower sides (the upper side in this embodiment) is
One end of the wire rope 10 is connected, and the other end (lower side in this embodiment) is elastically connected to the other end of the wire rope 10 via a spring 9a.

When pressure oil is supplied to and discharged from the lifting cylinder 3 to move the inner mast 2 up and down, the tension adjusting member 9 attached to the support member 2c moves up and down. This tension adjusting member 9
Since it forms a part of the loop of the wire rope 10, the wire drum 7c around which the wire rope 10 is wound also rotates, and the encoder 7a housed in the housing 7b is fixed to the inner mast 2. Generates a signal according to the amount of movement. Since the movement amount of the inner mast 2 and the forks 6a and 6b has a relationship of "1: 2", the height of the fork at that time can be easily obtained by converting it in the arithmetic unit.

Since the range in which the tension adjusting member 9 moves is on the common tangent line of the wire drum 7c and the grooved wheel 8, the loop length of the wire rope 10 is always constant and the spring 9
Since a predetermined tension can be applied to the wire rope 10 by a, it is possible to prevent the wire rope 10 from loosening or overtightening.

[0020]

According to the present invention, the grooved wheel 8 and the detector 7 are attached to the upper and lower side surfaces of the outer mast 1, and the wire rope 10 is wound in a loop shape via the tension adjusting member 9 between them. When the tension adjusting member 9 moves up and down in conjunction with the lifting movement of the inner mast 2, the wire rope 10 moves, and the detector 7 detects the amount of movement of the outer mast 2 and continuously detects the height of the forks 6a, 6b. You can

This detection means is capable of continuous detection, unlike the detection means such as a limit switch, in a stepwise manner, and is free from rattling such as rack and pinion or chain and chain drive power transmission. Wire rope 10
Since the fork 6a, 6b has a constant loop length, it is not necessary to wind the wire rope 10 like a reel, and the rotating body such as the detector 7 and the grooved wheel 8 is driven by the follower. Since only a simple movement is required, a power source such as a spiral spring is not required in the detection device, the structure is simple and the durability is improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a general lifting device for a forklift, (a) is a side view and (b) is a front view.

2A and 2B show details of the detection device of the present invention, FIG. 2A is a side view, and FIG. 2B is a front view.

[Explanation of symbols]

 1 Outer Mast 1a Plate 1b Plate 2 Inner Mast 2a Chain Car 2b Chain Car 2c Support Member 3 Lifting Cylinder 3a Cylinder Rod 4a Chain 4b Chain 5 Lift Bracket 6a Fork 6b Fork 7 Detector 7a Encoder 7b Housing 7c Wire Drum Car 9 Tension adjusting member 9a Spring 10 Wire rope

Claims (3)

[Claims] 1. A forklift in which forks 6a and 6b are attached to an inner mast 2 which is guided by the outer mast 1 and which moves up and down, via lift brackets 5, which are freely movable up and down. The grooved wheel 8 and the detector 7 are attached at intervals, and the detector 7 is composed of an encoder 7a, a housing 7b for accommodating the encoder 7a, and a wire drum 7c coaxially attached to the encoder 7a. 7c and the grooved wheel 8 with a tension adjusting member 9 interposed therebetween.
Is wound in a loop shape, and the tension adjusting member 9 is integrally attached to the tip end portion of the supporting member 2c which is fixed to the lower portion of the inner mast 2 at its base end portion and protrudes laterally of the outer mast 1. It has a shape with two sides,
One end of the wire rope 10 is connected to one of the upper and lower sides, and the other end of the wire rope 10 is elastically connected to the other through a spring 9a. . 2. A forklift in which forks 6a and 6b are attached to an inner mast 2 which is guided by the outer mast 1 and ascends and descends via a vertically movable lift bracket 5, and a predetermined vertical direction is provided on a side surface of the outer mast 1. The grooved wheel 8 and the detector 7 are attached at intervals, and the detector 7 is composed of an encoder 7a, a housing 7b for accommodating the encoder 7a, and a wire drum 7c coaxially attached to the encoder 7a. 7c and the grooved wheel 8 with a tension adjusting member 9 interposed therebetween.
In a loop shape, and the wire rope 10 is wound around the wire drum 7c a plurality of times in the middle of the loop,
The tension adjusting member 9 has a base end portion fixed to a proper lower portion of the inner mast 2 and integrally attached to a tip end portion of a supporting member 2c which is projected laterally of the outer mast 1. One end of the wire rope 10 is connected to one of the upper and lower sides, and the other end of the wire rope 10 is elastically connected to the other through a spring 9a. Characteristic fork height detection device. 3. An unmanned forklift in which forks 6a, 6b are attached to an inner mast 2 which is guided up and down by an outer mast 1 through a lift bracket 5 which is freely movable. , The grooved wheel 8 and the detector 7 are attached at an interval corresponding to the lifting stroke of the inner mast, and the detector 7 is attached coaxially with the encoder 7a, the housing 7b that houses the encoder 7a, and the encoder 7a. The wire rope 10 is wound around the wire drum 7c via the tension adjusting member 9 between the wire drum 7c and the grooved wheel 8 and the wire rope 10 is wound in the middle of the loop. 7c is wound a plurality of times, and the tension adjusting member 9 is fixed to the lower portion of the inner mast 2 at the base end thereof and is fixed to the outer portion. -It is integrally attached to the tip of the supporting member 2c that projects to the side of the mast 1 and has a side-U shape having two upper and lower sides, and one end of the wire rope 10 is connected to the upper side. A fork height detecting device for an unmanned forklift, wherein the other end of the wire rope 10 is elastically connected to a lower side via a spring 9a.