CN115265379B

CN115265379B - Laser rangefinder who moves volume detection under fork is exclusively used in

Info

Publication number: CN115265379B
Application number: CN202211194654.3A
Authority: CN
Inventors: 田敏; 程俊; 廖爱军; 杨阳; 王俊彤; 王彦涛
Original assignee: Tianjin Institute Of Special Equipment Supervision And Inspection Technology (tianjin Special Equipment Accident Emergency Investigation And Treatment Center)
Current assignee: Tianjin Institute Of Special Equipment Supervision And Inspection Technology (tianjin Special Equipment Accident Emergency Investigation And Treatment Center)
Priority date: 2022-09-29
Filing date: 2022-09-29
Publication date: 2022-11-29
Anticipated expiration: 2042-09-29
Also published as: CN115265379A

Abstract

The invention discloses a special laser distance measuring device for detecting the downward movement amount of a pallet fork, which comprises a distance measuring component, wherein the distance measuring component comprises a laser distance measuring part, a horizontal detector and a shell; the shell comprises a top shell, a conical shell and a soft shell; the top shell is a hard shell; the soft shell is in a flexible bag shape, the top opening is communicated with the bottom opening of the conical shell in a sealing way, and the mixture is filled in the soft shell; the mixture is sand and paraffin mixture; the inner wall of the conical shell is fixed with an electric heating wire, and the electric heating wire extends into the mixture and is used for heating the mixture; the laser transmitter is ball-jointed with the top shell through the ball-joint seat; the fixed rod is fixed at the lower part of the laser emitter; a fixed rod extends into the mixture. This laser rangefinder, the measuring fork that can be accurate move down the volume, reduce or avoid random error.

Description

Laser rangefinder who moves volume detection under fork is exclusively used in

Technical Field

The invention relates to a laser ranging device, in particular to a laser ranging device for detecting the downward displacement of a pallet fork of a truck.

Background

Whether the sealing performance of a hydraulic system of the forklift is good or not is judged according to whether the pallet fork moves downwards or not and the moving quantity of the pallet fork moves downwards or not in a static state of the forklift. The hydraulic system has good state and no leakage or little leakage if the downward movement amount is small or not. If the downward movement amount is large, the sealing is poor, and adjustment and maintenance are needed.

The error of manual detection is too large, the proficiency of personnel, the selection of detection reference and the like are different, and the numerical value difference of detection of different personnel is larger for the same forklift. For equipment maintenance, the referential of detection data is poor, and the detection work is forced to flow in a form.

The laser ranging device has the advantages of high precision of the tool and small random error. However, during detection, it is found that the detection position of the laser ranging device is different, and a large random error is also brought. If the laser ranging device is placed on the ground, the bottom surface of the fork is used as a reflecting surface to detect the downward movement amount of the fork. At this time, if the laser distance measuring device is inclined, and the light is not perpendicular to the ground, the detected value will increase with the increase of the inclination angle, and random errors occur due to different inclination angles, as shown in fig. 2. In field work, when a forklift driver or ordinary workers carry out daily detection, the referential performance of detection data is difficult to control. Therefore, how to adapt the laser detection device to different ground conditions quickly and reduce or avoid the occurrence of random errors is a core problem to be solved for improving the referential performance of the detection value of the downward shifting amount of the pallet fork.

As shown in fig. 3-4 (the leveling manner in the distance measuring assembly 200 of the conventional laser distance measuring device is a telescopic rod or a bolt for adjusting the length of the leg, and the positional relationship between the laser distance measuring part 210 and the level detector 220 is shown in the figure), the conventional laser distance measuring device is a mechanical structure, and the telescopic rod or the bolt is used for adjusting the length of the leg. This approach has two drawbacks: 1. the stability of the supporting legs is poor, after leveling, the equipment cannot be touched or operated basically when the equipment is moved, particularly when the ground is uneven, the original leveling position is easy to change, further the detection light is inclined, the detection result is inaccurate, and uncontrollable random factors are introduced; 2. the detection process lasts for 10 minutes, the approach of surrounding vehicles can cause ground vibration, the supporting legs are in rigid point contact with the ground, the position or the length of the supporting legs can be easily changed due to the ground vibration, uncontrollable random errors can also occur in detection, and the data referability is reduced.

Disclosure of Invention

The embodiment of the application is through providing a be exclusively used in laser rangefinder that fork displacement detected, has solved and has detected numerical value random error among the prior art great, and the problem that numerical value referential is low has realized that numerical value testing result random error is little, the effect that the referential of result is big.

The embodiment of the application provides a special laser distance measuring device for detecting the downward movement amount of a pallet fork, which comprises a distance measuring component, wherein the distance measuring component comprises a laser distance measuring part, the laser distance measuring part is used for detecting the downward movement distance of the pallet fork,

the ranging assembly comprises a horizontal detector and a shell;

the shell is used for positioning and leveling the laser ranging part;

the shell comprises a top shell, a conical shell and a soft shell; the top shell is a hard shell;

the top opening of the conical shell is communicated with the bottom opening of the top shell;

the area of the bottom opening of the conical shell is larger than that of the top opening;

the soft shell is in a flexible bag shape, the top opening is hermetically communicated with the bottom opening of the conical shell, and the soft shell is filled with a mixture; the mixture is a mixture of sand and paraffin, and the volume ratio of the sand to the paraffin is 1/2-1/1; the inner wall of the conical shell is fixed with an electric heating wire, and the electric heating wire extends into the mixture and is used for heating the mixture;

the laser ranging part comprises a ball joint seat, a fixed rod and a laser emitter;

the laser transmitter is used for transmitting laser and detecting distance; the laser transmitter is ball-jointed with the top shell through the ball-joint seat;

the fixed rod is fixed at the lower part of the laser emitter; the fixing rod extends into the mixture;

the horizontal detector is fixed on the laser emitter and comprises a transparent shell, water is filled in the transparent shell, and bubbles are contained in the transparent shell; when the bubble of the horizontal detector is positioned at the center of the transparent shell, the laser emitter emits laser light in a vertical upward direction.

Further, the preparation process of the mixture is as follows:

firstly, putting paraffin into a container, and heating to melt the paraffin;

and step two, pouring sand grains into the melted paraffin, and uniformly stirring to obtain a mixture.

Furthermore, a semiconductor refrigerating sheet is fixed on the inner wall of the conical shell.

Further, a second level detector is fixed on the top surface of the housing.

Furthermore, the device also comprises a reflection assembly, wherein the reflection assembly comprises a positioning plate and a reflection plate;

the positioning plate is detachably and fixedly connected with the pallet fork close to the portal;

the top surface of the reflecting plate is in ball joint with the bottom surface of the positioning plate, and the bottom surface of the reflecting plate is always in a horizontal state under the action of gravity.

Further, the reflective assembly is made of lightweight plastic.

Furthermore, one of a buckle, a bolt and a ribbon is selected for the detachable fixing mode.

The device further comprises an inclination angle detection assembly, wherein the inclination angle detection assembly comprises a positioning rod, a second ball joint seat, a supporting rod, a first distance measurement part and a second distance measurement part;

the positioning rod is in ball joint with the top surface of the top shell through a second ball joint seat; the bottom end of the positioning rod is inserted into the mixture;

the positioning rod is provided with a level detection device for detecting whether the top surface of the positioning rod is level or not;

when the bottom surface of the supporting rod is positioned on the top surface of the positioning rod under the condition that the top surface of the positioning rod is kept in a horizontal state, the supporting rod is in a vertical state;

the first distance measuring part is fixed at the lower part of the supporting rod, and the second distance measuring part is fixed at the top of the supporting rod; the longitudinal distance between the first distance measuring part and the second distance measuring part is fixed; the first distance measuring part and the second distance measuring part are used for detecting the distance between one side face of the portal frame and the measuring point.

Furthermore, the top end of the positioning rod is provided with a containing hopper, and paraffin is filled in the containing hopper; a floating plate is placed in the containing hopper, the density of the floating plate is smaller than that of paraffin, and the floating plate horizontally floats on the top of the paraffin after the paraffin is melted and is exposed out of the paraffin liquid surface; a magnet is fixed at the bottom of the accommodating bucket; the bottom end of the supporting rod is provided with the ferromagnetic block, and the magnet can attract the ferromagnetic block at the bottom end of the supporting rod.

Furthermore, the bottom surface of the floating plate is a spherical surface, and a connecting line between the center of the top surface of the spherical surface and the center of the top surface of the floating plate passes through the center of the sphere where the spherical surface is located.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: the effect of mixture makes the software shell can adapt to ground slope or hollow, makes whole location that can stabilize of range finding subassembly subaerial, and it is stable to detect basic position, can not receive external disturbance basically. In addition, the dead lever is fixed a position after the mixture hardens, makes laser emitter's light angle stable, and light direction remains stable throughout like this among the testing process. The detection result is stable in numerical value, the random error is small, and interference factors are discharged as far as possible.

Drawings

FIG. 1 is a schematic view of a vertical direction of detecting the distance between a fork and a measuring device;

FIG. 2 is a schematic view of a measurement state when the distance measuring assembly is tilted;

fig. 3 is a top view of a conventional laser ranging device;

FIG. 4 is a front view of a conventional laser ranging device;

FIG. 5 is a schematic view of a ranging assembly according to the present invention;

FIG. 6 is a schematic view of a laser ranging portion after being leveled after adapting to a depression on the ground;

FIG. 7 is a schematic diagram of laser ranging resulting errors with a large tilt angle of the gantry;

FIG. 8 is a schematic structural view of a reflector plate mounted on or plugged into the reflector plate;

FIG. 9 is a schematic view of a tilt angle detection assembly;

FIG. 10 is a schematic view of a tilt angle detection assembly;

FIG. 11 is a schematic view of an initial distance between a side of a transverse inspection gantry and an inspection position;

FIG. 12 is a schematic view of the final distance between one side of the transverse inspection portal and the inspection station;

in the figure, a forklift 100, a mast 110, a pallet fork 120;

the range finder comprises a range finder assembly 200, a laser range finder 210, a ball joint 211, a fixing rod 212, a laser emitter 213, a level detector 220, a shell 230, a top shell 231, a conical shell 232, a soft shell 233, a mixture 234, a heating wire 235, a second level detector 236 and a semiconductor refrigeration piece 240;

a reflection assembly 300, a positioning plate 310, a reflection plate 320;

the tilt angle detecting assembly 400, the positioning rod 410, the second ball socket 420, the accommodating bucket 430, the floating plate 431, the magnet 432, the supporting rod 440, the ferromagnetic block 441, the first distance measuring unit 450, and the second distance measuring unit 460.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present, or they may be removably secured. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not represent the only embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example one

As shown in fig. 1 to 6, a laser ranging apparatus dedicated to fork downward movement detection includes a ranging assembly 200, the ranging assembly 200 includes a laser ranging portion 210, the ranging assembly 200 detects a fork downward movement distance through the laser ranging portion 210,

the ranging assembly 200 further comprises a level detector 220 and a housing 230;

the housing 230 is used for positioning and leveling the laser ranging part 210;

the shell 230 comprises a top shell 231, a conical shell 232 and a soft shell 233; the top case 231 is a hard case;

the top opening of the conical shell 232 is communicated with the bottom opening of the top shell 231;

the area of the bottom opening of the conical shell 232 is larger than that of the top opening;

the soft shell 233 is in a flexible bag shape, the top opening of the soft shell 233 is communicated with the bottom opening of the conical shell 232 in a sealing way, and the soft shell 233 is filled with a mixture 234; the mixture 234 is a mixture of sand and paraffin, and the volume ratio of the sand to the paraffin is 1/2-1/1; the heating wire 235 is fixed on the inner wall of the conical shell 232, and the heating wire 235 extends into the mixture for heating the mixture;

the laser ranging part 210 comprises a ball socket 211, a fixing rod 212 and a laser emitter 213;

the laser transmitter 213 is used for transmitting laser and detecting distance; the laser transmitter 213 is ball-jointed with the top case 231 through the ball joint seat 211;

the fixing rod 212 is fixed at the lower part of the laser emitter 213; securing rod 212 extends into mixture 234;

the level detector 220 is fixed on the laser emitter 213, and the level detector 220 comprises a transparent shell which is filled with water and is provided with bubbles; when the bubble of the level detector 220 is located at the center of the transparent case, the direction in which the laser emitter 213 emits laser light is directed vertically upward.

The detection process is as follows:

step one, the heating wire 235 is turned on, so that the soft shell 233 has plasticity due to the melting of paraffin;

step two, placing the shell 230 on the ground, standing for 30-90 seconds, and enabling the laser emitter 213 to be located right below the fork; during the period, the soft shell adapts to the shape of the ground, and the position of the hard part of the shell is manually adjusted, so that the hard part is basically vertically placed;

step three, the heating wire 235 is closed, the laser emitter 213 is rotated before the mixture is completely hardened, the position of the laser emitter 213 is adjusted by observing the horizontal detector 220, so that the bubble of the horizontal detector 220 is positioned at the center of the transparent shell, and the position is maintained, so that the bubble of the horizontal detector 220 is still positioned at the center of the transparent shell after the mixture is hardened, and the vertical upward direction of the light emitted by the laser detection is ensured;

and step four, adjusting the position of the pallet fork to enable the pallet fork to be located at the detection starting position, starting the laser ranging part 210, starting to output or display data, starting timing, recording the initial distance, recording the final distance after 10 minutes, and subtracting the final distance from the initial distance to obtain the downward moving distance of the pallet fork.

The mixture 234 functions to make the soft shell adapt to the slope of the ground or pothole, so that the whole ranging assembly 200 can be stably positioned on the ground, and the detection base is stable in position and basically free from external interference. In addition, the fixing rod 212 is positioned after the mixture is hardened, so that the light angle of the laser emitter 213 is stable, and the light direction is always stable in the detection process. The detection result is stable in numerical value, the random error is small, and interference factors are eliminated as far as possible.

The mixture 234 is prepared as follows:

firstly, putting paraffin into a container, and heating to melt the paraffin;

The purpose of adding sand grains is to ensure that the paraffin has better plasticity and does not flow randomly after being melted, the paraffin deforms slowly under the action of self gravity, but deforms rapidly when external force is applied to the fixing rod 212. And after sand grains are added, the cooling rate is accelerated, and the position of the laser emitter is convenient to adjust quickly.

To accelerate the cooling of the mixture, semiconductor chilling plates 240 are affixed to the inner wall of the conical shell. To provide a base location for the housing, a second level detector 236 is secured to the top surface of the housing.

The stability of the mixture was further examined. A commercially available tension gauge and a round gimbaled level vial were used as the detection tool. The universal level bubble selects a commercial product with at least two circles of graduation lines. The test site is a flat ground, so that uncertain factors of detection and evaluation are reduced. The tripod uses a common camera tripod on the market. The mixture is selected from three types of sand grains and paraffin wax with the volume ratio of 1/2, 1/1.5 and 1/1.

The tension borne by the fixed rod for positioning the paraffin mixture and the position of the laser emitter fixed on the fixed rod is compared with the tension borne by the positioning point of the laser detector on the tripod. The height of the detection point of the two devices from the ground is the same during detection. The actual test was chosen at 28cm from the ground.

And (3) taking the level detector (universal level bubble) as the initial position of the two devices in a leveling state (the bubble is positioned in the scale of the most central circle), then horizontally pulling the detection points of the two devices by using the tension meter, and observing the numerical value of the tension meter when the bubble in the level detector moves to the adjacent first circle outside the scale of the central circle.

Wherein the pulling force that the detection point department of this application bore is according to sand grain and paraffin volume ratio respectively: the pulling force is 30.5 newtons at 1/2; the pulling force is 31.6 cattle at 1/1.5; the pulling force at 1/1 time is 30.8N. Due to the distribution of the supporting legs, the pulling force of the tripod in different pulling directions is different when the tripod is pulled in the same horizontal plane, the borne pulling force is in a range of 2.1-8.9 newtons. Therefore, the laser detector is positioned by the mixture, and compared with a common tripod, the 10-minute distance measurement operation can be completed more stably, and interference factors are reduced or even avoided.

Example two

In the detection of the first embodiment, the vertical arrangement of the gantry is considered, or the inclination angle is relatively small, but if the gantry has an obvious inclination angle, the difference of the distance between the detection point and the gantry can cause a larger difference of the detection result. The portal has a large inclination angle, and after the fork moves downwards, the detection points can change under the condition that the light emitting position is not changed, as shown in fig. 7, the deviation can occur due to the selection of the detection points when the fork moves downwards, and thus, the random error of manual operation can be introduced. Therefore, the position of the detection point is further improved as shown in fig. 8.

The reflection assembly 300 is further included, and the reflection assembly 300 includes a positioning plate 310 and a reflection plate 320;

the positioning plate 310 is detachably and fixedly connected with the fork close to the door frame;

the top surface of the reflective plate 320 is ball-jointed with the bottom surface of the positioning plate 310, and the bottom surface of the reflective plate 320 is always in a horizontal state under the action of gravity.

During detection, the detection point is always positioned on the reflecting plate 320, and the inclination of the gantry does not influence the final detection value. Therefore, random errors caused by inclination of the gantry and uncertainty of the detection position can be eliminated.

Reflection component 300 uses the plastics of light to make, and the quality is lighter, moves down to the fork and influences little, and the quality is invariable basically, can not produce random error to the detected data, can dismantle fixed mode and select for use the fixed mode commonly used such as buckle, bolt, ribbon.

EXAMPLE III

In some forklift models, the door frame can rotate and is driven by a hydraulic system. This results in an increase in mast inclination if the hydraulic system is not sealed properly when detecting the downward movement of the forks. In order to accurately assess the condition of the hydraulic system, the mast inclination angle also needs to be detected. The single-point detection of the tilt angle cannot realize the tilt angle detection, so that the transverse double-point detection is performed on the gantry on the basis of the scheme, and the principle is as shown in fig. 12. Through detecting the transverse distance of the portal relative to the same vertical plane, the inclination angle of the portal relative to the vertical plane can be achieved. The calculation of the inclination angle depends on that two longitudinal detection points are required to be on the same vertical straight line, so that an accurate angle value can be obtained through calculation. This requires that the position is detected as well, as in the previous solutions, and that the stabilization of the position is fundamental.

An inclination angle detection assembly 400 is additionally arranged, wherein the inclination angle detection assembly 400 comprises a positioning rod 410, a second ball socket 420, a supporting rod 440, a first distance measurement part 450 and a second distance measurement part 460;

the positioning rod 410 is in ball joint with the top surface of the top shell 231 through a second ball joint seat 420; the bottom end of the positioning rod 410 extends into the mixture 234;

the positioning rod 410 is provided with a level detection device for detecting whether the top surface of the positioning rod 410 is level;

when the bottom surface of the support rod 440 is positioned on the top surface of the positioning rod 410 while the top surface of the positioning rod is kept horizontal, the support rod 440 is in a vertical state;

the first distance measuring part 450 is fixed at the lower part of the support rod 440, and the second distance measuring part 460 is fixed at the top of the support rod 440; the longitudinal interval between the first ranging part 450 and the second ranging part 460 is fixed; the first and second

distance measuring parts

450 and 460 are used for the lateral distance between them and one side of the door frame, respectively.

During measurement, the tilt angle sensing assembly 400 is positioned on the side of the mast adjacent the truck body such that the first and second rangefinders horizontally sense the horizontal distance between a surface on the mast and the rangefinder. Before the timing starts, the values obtained by the two distance measuring parts are detected, and the longitudinal distance between the first distance measuring part and the second distance measuring part is constant and is L1. The distance between the first distance measuring unit 450 and the gantry is L3, the distance between the second distance measuring unit 460 and the gantry is L2, and the inclination angle is arctan (L2-L3)/L1, calculated by the similar triangle and the trigonometric function. After ten minutes, the transverse distances of the end positions are measured and obtained as L2 'and L3', the inclination angle of the end position is arctan (L2 '-L3')/L1, and the inclination angle of the gantry within 10 minutes can be obtained by using arctan (L2 '-L3')/L1-arctan (L2-L3)/L1.

In order to accurately measure the lateral distance between the lateral side of the gantry and the measuring point, i.e. to enable the two measuring points to be on the same vertical line in the longitudinal direction, the supporting rod 440 needs to be kept in a vertical state. It is not easy to adjust the angle of the supporting rod 440 quickly and precisely. Therefore, the fixing rod is further improved.

The top end of the positioning rod 410 is provided with a containing bucket 430, and paraffin is filled in the containing bucket 430; a floating plate 431 is placed in the containing hopper 430, the density of the floating plate 431 is smaller than that of paraffin, and after the paraffin is melted, the floating plate 431 horizontally floats on the top of the paraffin and is exposed out of the liquid surface of the paraffin; a bottom fixed magnet 432 of the receiving bucket 430; the bottom end of the support rod 440 is provided with a ferromagnetic block 441, and the magnet 432 can attract the ferromagnetic block 441 at the bottom end of the support rod 440. The bottom surface of the floating plate 431 is a spherical surface, and the connecting line of the top surface center of the spherical surface and the top surface center of the floating plate passes through the spherical center of a ball where the spherical surface is located, so that the positioning is convenient.

In actual operation, the position of the positioning rod 410 is adjusted, paraffin in the accommodating hopper 430 is melted after the positioning rod is basically leveled, the floating plate 431 naturally floats and is leveled, and when the paraffin is hardened or is still plastic soon, a horizontal ruler of the horizontal detector can be placed on the floating plate to detect whether the top surface is horizontal. If not flat, fine adjustments may be made when the paraffin is not fully hardened. After the paraffin is completely hardened, the support rod 440 is placed on the floating plate 431 and is positioned by magnetic attraction. And then starting the laser ranging equipment, and detecting the initial distance and the final distance. And (4) performing calculation.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made to the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A special laser distance measuring device for detecting the downward movement of a pallet fork comprises a distance measuring component (200), wherein the distance measuring component (200) comprises a laser distance measuring part (210) and detects the downward movement distance of the pallet fork through the laser distance measuring part (210),

the ranging assembly (200) further comprises a level detector (220) and a housing (230);

the shell (230) is used for positioning and leveling the laser ranging part (210);

the shell (230) comprises a top shell (231), a conical shell (232) and a soft shell (233); the top shell (231) is a hard shell;

the top opening of the conical shell (232) is communicated with the bottom opening of the top shell (231);

the area of the bottom opening of the conical shell (232) is larger than that of the top opening;

the soft shell (233) is in a flexible bag shape, the top opening is hermetically communicated with the bottom opening of the conical shell (232), and the soft shell (233) is filled with a mixture (234); the mixture (234) is a mixture of sand and paraffin, and the volume ratio of the sand to the paraffin is 1/2-1/1; an electric heating wire (235) is fixed on the inner wall of the conical shell (232), and the electric heating wire (235) extends into the mixture and is used for heating the mixture;

the laser ranging part (210) comprises a ball joint seat (211), a fixing rod (212) and a laser emitter (213);

the laser transmitter (213) is used for transmitting laser and detecting distance; the laser transmitter (213) is in ball joint with the top shell (231) through a ball joint seat (211);

the fixing rod (212) is fixed at the lower part of the laser emitter (213); the fixing rod (212) extends into the mixture (234);

the horizontal detector (220) is fixed on the laser emitter (213), the horizontal detector (220) comprises a transparent shell, water is filled in the transparent shell, and bubbles are contained in the transparent shell; when the bubble of the horizontal detector (220) is positioned at the center of the transparent shell, the laser emitter (213) emits laser light in a vertical upward direction.

2. Laser distance measuring device, dedicated to the detection of the fork fall according to claim 1, characterized in that the mixture (234) is prepared as follows:

firstly, putting paraffin into a container, and heating to melt the paraffin;

3. The laser distance measuring device special for detecting the downward movement amount of the pallet fork as claimed in claim 1, wherein a semiconductor refrigeration piece (240) is fixed on the inner wall of the conical shell.

4. The laser distance measuring device special for detecting the downward movement of the pallet fork as claimed in claim 1, wherein a second level detector (236) is fixed on the top surface of the housing.

5. The laser distance measuring device special for detecting the downward movement amount of the pallet fork as claimed in claim 1, further comprising a reflection assembly (300), wherein the reflection assembly (300) comprises a positioning plate (310) and a reflection plate (320);

the positioning plate (310) is detachably and fixedly connected with the fork close to the portal frame;

the top surface of the reflecting plate (320) is in ball joint with the bottom surface of the positioning plate (310), and the bottom surface of the reflecting plate (320) is always in a horizontal state under the action of gravity.

6. The laser distance measuring device special for fork downward movement detection as claimed in claim 5, wherein the reflection assembly (300) is made of light plastic.

7. The laser distance measuring device special for detecting the downward movement amount of the pallet fork as claimed in claim 6, wherein the detachable fixing mode is selected from one of a buckle, a bolt and a tie.

8. The laser distance measuring device special for detecting the downward movement of the pallet fork as claimed in claim 1, further comprising an inclination angle detecting assembly (400), wherein the inclination angle detecting assembly (400) comprises a positioning rod (410), a second ball socket (420), a supporting rod (440), a first distance measuring part (450) and a second distance measuring part (460);

the positioning rod (410) is in ball joint with the top surface of the top shell (231) through a second ball joint seat (420); the bottom end of the positioning rod (410) penetrates into the mixture (234);

the positioning rod (410) is provided with a horizontal detection device for detecting whether the top surface of the positioning rod (410) is horizontal or not;

when the top surface of the positioning rod (410) is positioned on the bottom surface of the supporting rod (440) in a horizontal state, the supporting rod (440) is in a vertical state;

the first distance measuring part (450) is fixed at the lower part of the support rod (440), and the second distance measuring part (460) is fixed at the top of the support rod (440); the longitudinal distance between the first distance measuring part (450) and the second distance measuring part (460) is fixed; the first distance measuring part (450) and the second distance measuring part (460) are used for detecting the distance between one side surface of the portal and the measuring point.

9. The laser distance measuring device special for detecting the downward movement amount of the pallet fork as claimed in claim 8, wherein the top end of the positioning rod (410) is provided with a containing bucket (430), and the containing bucket (430) is filled with paraffin; a floating plate (431) is placed in the containing hopper (430), the density of the floating plate (431) is smaller than that of paraffin, and after the paraffin is melted, the floating plate (431) horizontally floats on the top of the paraffin and is exposed out of the liquid surface of the paraffin; a magnet (432) is fixed at the bottom of the accommodating bucket (430); the bottom end of the supporting rod (440) is provided with a ferromagnetic block (441), and the magnet (432) can attract the ferromagnetic block (441) at the bottom end of the supporting rod (440).

10. The laser distance measuring device special for detecting the downward movement of the pallet fork as claimed in claim 9, wherein the bottom surface of the floating plate (431) is a spherical surface, and the connecting line of the top surface center of the spherical surface and the top surface center of the floating plate passes through the spherical center of the sphere where the spherical surface is located.