CN213591066U - Fine coal screening device - Google Patents

Abstract

A fine coal screening device comprises a vibrating screen body, and is also provided with a detection device, a blockage removal device and a vibrating feeding device; the vibration feeding equipment comprises a feeding bin and a vibration motor, wherein the feeding bin is arranged at the high position of the frame of the vibration screen body, and the vibration motor is arranged at the lateral outer end of the feeding bin; the blockage removing equipment comprises a motor reducing mechanism and a movable plate, wherein the motor reducing mechanism is arranged at the lower end of a screen mesh of the vibrating screen body, and the movable plate is arranged at the upper end of a power output shaft of the motor reducing mechanism; the detection equipment comprises three photoelectric switches, a stabilized voltage power supply and a control sub-circuit, wherein the three photoelectric switches are respectively arranged at the upper ends of the two sides of the frame of the vibrating screen body, and the stabilized voltage power supply and the control sub-circuit are arranged in the element box and are electrically connected with the photoelectric switches and the motor speed reducing mechanism. This is novel need not manual operation, outside pushing down the shale shaker body both sides end automatically, after releasing the plug, the fly leaf can resume by preceding to the back be close a rectilinear state. This is novel to have guaranteed production and normally gone on.

Description

Fine coal screening device

Technical Field

The utility model relates to a production facility technical field that coal processing was used, especially a meticulous coal screening plant.

Background

In places where coal combustion is needed, such as chemical industry, power plants, cement plants and the like, the coal is often required to be screened in a grading manner, and the screened fine coal and the coal briquettes are separately used, so that the requirements of different combustion equipment on different forms of coal are met (for example, a boiler coal injection burner is used for screening fine coal which is as good as possible for processing into powder, or a screen with small screen meshes is directly adopted for screening pulverized coal for use after being crushed).

At present, a vibrating screen is used for screening fine coal mostly, and in the application, coal needing to be screened finely is continuously input to the vibrating screen by a conveying belt or a coal storage bin of the previous procedure for vibrating screening. The existing vibrating screen has the following problems due to the structure limitation. Firstly, the coal is directly input to the high position at the rear end of the vibrating screen in the previous process, the coal is easy to accumulate together, and good screening effect cannot be achieved correspondingly due to the fact that the coal is not effectively scattered and is high in thickness. Second, the coal cinder that inevitably has great external diameter in the coal of carrying out the screening, do not move to the front end from the screen cloth rear end when more coal cinder and fall on ground etc. (the coal cinder blocks up the back, wherein little coal cinder can be with gap filling between the coal cinder, can lead to the jam degree further to increase), can block up on the screen cloth, the screening effect variation that not only leads to the fine coal like this, when blockking up seriously, can lead to the unable normal work of shale shaker, only can put into production again after shutting down the manual cleaning.

SUMMERY OF THE UTILITY MODEL

In order to overcome the shale shaker that current fine coal used, because of the structure limit, can not reach good screening effect, and the plug on the unable automatic clear screen cloth, can bring the drawback of influence to screening work, the utility model provides an install vibration feeding equipment on the rear end high level of shale shaker, make the coal that gets into on the screen cloth be in the state of spreading out as far as possible, follow-up shale shaker body can reach better fine coal screening effect, it has detection equipment and arranges stifled equipment, in operation, after the screen cloth of shake shale shaker body goes up the coal jam to certain thickness, do not need the manual operation, arrange the rotor plate of stifled equipment and can push down the plug to shale shaker body both sides end automatically, brought the facility for the staff from this, and guaranteed the production normal clear coal sieving mechanism who goes on.

The utility model provides a technical scheme that its technical problem adopted is:

a fine coal screening device comprises a vibrating screen body and is characterized by also comprising a detection device, a blockage removal device and a vibrating feeding device; the vibrating feeding equipment comprises a feeding bin and a vibrating motor, wherein the feeding bin is arranged at the high position of the frame of the vibrating screen body, and the vibrating motor is arranged at the lateral outer end of the feeding bin; the blockage removing equipment comprises a motor reducing mechanism and a movable plate, wherein the motor reducing mechanism is arranged at the lower end of a screen of the vibrating screen body, a power output shaft of the motor reducing mechanism is positioned at the upper end of the screen, and the movable plate is arranged at the upper end of the power output shaft of the motor reducing mechanism; the detection equipment comprises three photoelectric switches, a voltage-stabilized power supply and a control sub-circuit, wherein the three photoelectric switches are respectively arranged at the upper ends of two sides of the frame of the vibrating screen body, and the length of the movable plate is smaller than the width of the upper end of the vibrating screen; the stabilized voltage power supply and the control sub-circuit are arranged in the element box; the power output end of the stabilized voltage power supply is electrically connected with the first photoelectric switch at the rear part of the upper side end of the rack and the two ends of the power input of the control sub-circuit respectively, and the power output end of the first photoelectric switch is electrically connected with the input end of the trigger power supply of the control sub-circuit; the power supply output end of the control sub-circuit is electrically connected with the power supply input ends of the second photoelectric switch and the third photoelectric switch on two sides of the front part of the upper side end of the rack respectively; the signal output ends of the second and third photoelectric switches are electrically connected with the control signal input end of the control sub-circuit, and the power supply output end of the control sub-circuit is electrically connected with the power supply input end of the motor speed reducing mechanism.

Further, when the movable plate is located on a nearly straight line from front to back on the screen, the movable plate and the detecting heads of the first photoelectric switch are not transversely located on the same straight line, and the movable plate and the detecting heads of the second photoelectric switch and the third photoelectric switch are transversely located on the same straight line.

Furthermore, the height of the detection heads of the second photoelectric switch and the third photoelectric switch is lower than that of the movable plate, and the height of the detection head of the first photoelectric switch is the highest limit coal seam height on the screen set by a user.

Furthermore, both sides end of shale shaker respectively has the swash plate.

Further, the lower extreme of fly leaf and the screen cloth upper end separation distance of shale shaker body.

Further, the stabilized voltage power supply of the detection device is an alternating current to direct current switching power supply module.

Furthermore, the control sub-circuit of the detection device comprises a time control switch, relays and diodes, wherein the positive power output end of the time control switch is connected with the positive power input end of the first relay and the positive electrode of the first diode, the negative electrodes of the first, second and third diodes are connected with the positive power input end of the second relay, and the negative power output end of the time control switch is connected with the negative power input ends of the two relays; the time control switch is a full-automatic microcomputer time control switch.

Furthermore, the first photoelectric switch is provided with a relay which is electrically connected with the first photoelectric switch, the power output end, the negative power input end and the relay power input end of the first photoelectric switch are respectively connected, and the relay control power input end is connected with the positive power input end of the photoelectric switch.

The utility model has the advantages that: this new type installs vibration feeding equipment on the rear end high level of shale shaker, and the coal that gets into in the feeding storehouse falls on the screen cloth back from the lower extreme of discharge gate under vibrating motor's vibration effect, enables to get into the coal on the screen cloth and is in the state of spreading out as far as possible, because the corresponding step-down of coal seam height, follow-up shale shaker body can reach better fine coal screening effect. This is novel to have detection equipment and arrange stifled equipment, and the during operation, after the coal blocking up certain thickness on the screen cloth of shale shaker body, do not need the manual operation, arrange the motor reduction gears of stifled equipment and can drive the fly leaf and rotate a period, outside pushing down the shale shaker body both sides end automatically, after releasing the plug, the fly leaf can resume by preceding to the back be close a linear state, can not bring any influence to subsequent fine coal screening. This is novel to have brought the facility for the staff, and has guaranteed production normal clear.

Drawings

The present invention will be further explained with reference to the drawings and examples.

Fig. 1 is a schematic view of the structure and a part of the present invention.

Fig. 2 is a circuit diagram of the present invention.

Detailed Description

As shown in fig. 1, the fine coal screening device comprises a vibrating screen body 1, and is further provided with a detection device 2, a blockage removal device 3 and a vibrating feeding device 4; the vibration feeding equipment 4 comprises a feeding bin 41 and a vibration motor 42 (working voltage is 380V and power is 1.5KW), the upper end and the lower end of the rectangular feeding bin 41 are of an open structure, a conical feeding hole 411 with a large upper part and a small lower part is welded at the upper end of the feeding bin 41 (a coal outlet of a conveying belt or a coal storage bin of the previous process is positioned at the upper end of the feeding hole 411), the outer diameters of the lower end of the feeding hole 411 and the upper end of the feeding bin 41 are consistent, a rectangular discharging hole 412 which is distributed left and right is arranged at the lower end of the feeding bin 41, the lower parts of the left and right outer side ends of the feeding bin 41 are respectively installed at the left and right parts of the rear side end of a frame 101 of the vibration screen body through screw nuts, the lower end of the left and right outer side of the feeding bin 41 is; the blockage removing equipment comprises a motor reducing mechanism 31 and a rectangular movable plate 32, wherein a rectangular supporting plate 103 is longitudinally welded on a rack 101 at the middle part of the lower end of a screen mesh 102 of a vibrating screen body, an opening is formed in the middle part of the supporting plate 103, a bearing sleeve is installed at the lower end of the opening, a dustproof cover is installed between an inner ring and an outer ring of a bearing of the bearing sleeve, the motor reducing mechanism 31 is installed at the lower side end of the supporting plate 103 through a screw nut, a power output shaft of the motor reducing mechanism 31 is vertically and tightly sleeved in the inner ring of the bearing, the upper part of the power output shaft of the motor reducing mechanism 31 is positioned at the upper end of the screen mesh 102 of the vibrating; the detection device comprises three sets of photoelectric switches, a stabilized voltage power supply 22 and a control sub-circuit 23, wherein two support plates 24 which are vertically distributed are welded at the rear end of a power output shaft of a motor speed reducing mechanism 31 and on the left side of the middle part of a frame 101 of a vibrating screen body from front to back, the support plate 24 which is vertically distributed is welded at the front end of the power output shaft of the motor speed reducing mechanism 31 and on the right side of the middle part of the frame 101 of the vibrating screen body, the shells of the three sets of photoelectric switches 211, 212 and 213 are arranged at the upper ends of the inner sides of the three support plates 24 through screw nuts (the detecting heads of the photoelectric switches 211, 212 and 213 are arranged on the inner side of the frame), the heights of the three photoelectric switches 211, 212 and 213 are slightly lower than the height of a movable plate 32, the length of the movable plate 32 is slightly smaller than the left and right width of the upper, the fine coal which is normally screened is blocked, and the fine coal in the screening is prevented from falling to the ground); the stabilized voltage power supply and the control sub-circuit are arranged on a circuit board in the element box, and the element box is arranged in an electrical control box of the vibrating screen body.

As shown in fig. 1, the height of the movable plate 32 is higher than the height of the coal seam on the screen mesh 102 when the vibrating screen body normally works, when the movable plate 32 is in a straight line from front to back, the left end of the rear side of the movable plate 32 and the detecting head of the first photoelectric switch 211 are not in a straight line from left to right (no matter how the movable plate 32 rotates, the infrared light beam emitted by the emitting head of the first photoelectric switch a2 is not blocked), the left end of the rear side of the movable plate and the detecting head of the second photoelectric switch 212 are in a straight line from left to right, and the right end of the front side of the movable plate 32 and the detecting head of the third photoelectric switch 213 are in a straight line from left to. The height of the detection heads of the second photoelectric switch 212 and the third photoelectric switch 213 is slightly lower than that of the movable plate 32, and the height of the detection head of the first photoelectric switch 211 is the highest limit coal seam height on the screen mesh 102 set by a user. Both side ends of the vibrating screen are respectively provided with an inclined plate 105 with the front and back length being consistent with the front and back length of the vibrating screen body through a screw nut, and the upper end of the inclined plate 105 is high, the lower end of the inclined plate is low and is contacted with the ground. The lower end of the movable plate 32 is spaced from the upper end of the screen mesh 102 of the vibrating screen body by a certain distance (3 cm).

As shown in fig. 2, the motor reduction mechanism M3 is a three-phase coaxial motor gear reducer with 380V working current, and the power is 2.5KW, and the power output by the motor of the motor reduction mechanism is reduced by the multi-stage reduction gears in the motor reduction mechanism during operation, and is output from the power output shaft after the torque is increased (12 rpm). The voltage-stabilized power supply A1 of the detection device is a switch power supply module finished product with the model of 220V/12V/200W, which is converted from alternating current 220V to direct current 12V and is provided with two power input ends 1 and 2 pins and two power output ends 3 and 4 pins. The control sub-circuit of the detection device comprises a time control switch A3, relays K1 and K2, diodes VD, VD1 and VD2 which are connected through a lead, wherein the 3 pins of the positive pole power output end of the time control switch A3 are connected with the positive pole power input end of a first relay K1 and the positive pole of the first diode VD, the negative poles of the first diode VD, a second diode VD1 and a third diode VD2 are connected with the positive pole power input end of a second relay K2, and the 4 pins of the negative pole power output end of the time control switch A3 are connected with the negative pole power input ends of two relays K1 and K2; the time control switch A3 is a full-automatic microcomputer time control switch with model KG316T, the upper end of the front side of the casing of the microcomputer time control switch A3 is provided with a liquid crystal display, the front lower end of the casing is provided with seven keys of cancel/recovery, time correction, week correction, automatic/manual, timing and clock, the microcomputer time control switch also is provided with two power input ends 1 and 2 pins, and two power output ends 3 and 4 pins. Three photoelectric switches A2, A4 and A5 are finished products of a reflective photoelectric switch sensor of a model DS10C4, the photoelectric switches A2, A4 and A5 are provided with two power supply input ends 1 and 2 pins and a high level output end 3 pin, infrared beams emitted by a straight line of an emitting head of a front end detecting head are blocked by an article when the sensor works, a receiving head of the front end of the detecting head receives the high level output end 3 pin, and the high level is not output when no article blocks; the farthest detection distance of the photoelectric switch is 200cm, an adjusting knob is arranged in the rear side end of the shell, the detection distance of the adjusting knob is shortened when the adjusting knob is adjusted leftwards, and the detection distance of the adjusting knob is lengthened when the adjusting knob is adjusted rightwards; the first photoelectric switch A2 (detection distance 1.2 m, width 1.3 m of the screen 102) is provided with a relay K which is arranged in the element box and is connected with the relay K through a lead, the power output end pin 3, the negative power input end pin 2 and the two ends of the power input end of the relay K of the first photoelectric switch A2 are respectively connected, and the control power input end of the relay K is connected with the positive power input end pin 1 of the photoelectric switch A2 (the detection distance of the second photoelectric switch A4 and the second photoelectric switch A5 is 60 cm).

As shown in fig. 2, power input terminals 1 and 2 of regulated power supply a1 and two poles of an alternating current 220V power supply are connected through leads respectively. The power output end 3 and the pin 4 of the voltage-stabilized power supply A1 and the first photoelectric switch A2(211) at the rear left end of the vibrating screen body are respectively connected with the power input ends 1 and 2 of the power input ends, and the power input ends of the control sub circuit and the relay K1 at the power input ends are respectively connected with the negative power input end through leads (the negative power input end of the relay K1 is connected with the pin 2 of the time control switch A3 through leads). The normally open contact end of the power output end relay K of the first photoelectric switch is connected with the pin 1 of the time control switch A3 of the trigger power input end of the control sub-circuit through a lead. And a power output end relay K1 normally-closed contact end and a negative power input end of the control sub circuit are respectively connected with power input ends 1 and 2 of a second photoelectric switch A4(212) at the front left end of the vibrating screen body and a third photoelectric switch A5(213) at the front right end of the vibrating screen body through leads. The pin 3 of the second photoelectric switch A4 and the pin 3 of the third photoelectric switch A5 are respectively connected with the positive electrodes of the control signal input end diodes VD1 and VD2 of the control sub-circuit through leads. Three control power supply input ends of a 380V three-phase power supply and a relay K2 of the control sub-circuit are respectively connected through leads. The three normally open contact ends of a power output end relay K2 of the control sub-circuit are connected with the three power input ends of a motor reducing mechanism M3 through leads. M1 and M2 are respectively two vibrating motors arranged at the outer ends of the left side and the right side of the feeding bin 41 and a vibrating motor on the vibrating screen body.

As shown in fig. 1 and 2, other using processes and principles of the novel vibrating screen body 1 are completely consistent with those of the existing vibrating screen. When the novel coal bin works, the conveying belt or the coal storage bin of the previous procedure continuously inputs coal needing fine screening into the feeding bin 41 (the input speed is close to the speed for screening the fine coal by the screen mesh), and because the vibrating motor M1 at the left and right outer side ends of the feeding bin 41 is powered on at the moment and is in a working state, the vibrating motor M1 generates a vibrating action, the coal entering the raw material bin 41 can uniformly fall out from the discharge port 412 at the lower end of the raw material bin 41 and is laid on the screen mesh 102 left and right; at this point, the vibrating motor M2 on the vibrating screen body itself is powered on to vibrate the screen 102 with the lower end mounted on the spring 106, so that the coal fed into the screen 102 through the feeding bin 41 can be continuously screened. After screening, fine coal falls on the ground at the lower end of the screen mesh 102, and coal blocks with a slightly larger particle size fall on the ground at the front end of the screen mesh 102. Through the aforesaid, this is novel just constantly to screening coal.

As shown in fig. 1 and 2, after the 220V ac power enters the two terminals 1 and 2 of the power input of the switching power module a1, the switching power module a1 outputs a stable 12V power under the action of its internal circuit, and the power enters the two terminals of the first opto-electronic switch a2 and the power input of the control sub-circuit, so that the above circuits are in the power-on working state. When the vibrating screen body 1 normally works to screen fine coal and the upper end of the screen is not blocked, the height of the coal layer on the screen is lower than that of the transmitting head of the photoelectric switch A2, 3 pins of the photoelectric switch A2 do not output power, and the subsequent motor reducing mechanism M3 cannot work electrically. When because of various reasons, when 1 screen cloth upper end of shale shaker body blockked up (for example in the fine coal great external diameter coal cinder is more blockked up on the screen cloth, perhaps the coal volume of one process output is too much etc.), the coal seam height is higher than photoelectric switch A2's transmitting head height on the screen cloth, the infrared light beam of transmitting head straight line launch of photoelectric switch A2 (detection range 1.2 meters) is blockked, like this, photoelectric switch A2 can export high level under its internal circuit effect and get into relay K anodal power input end, then, relay K gets electric actuation its control power input end of actuation and normally open contact end closure. Since pin 1 of time switch A3 is connected to the normally open contact terminal of relay K, time switch A3 is now electrically activated. After the time control switch A3 is powered on to work, under the action of an internal circuit and 3 and 4 feet of output power time set by technicians, power supply (with adjustable output power time) of 8 seconds can be output to enter two ends of a power supply input of the relay K1 and enter two ends of a power supply input of the relay K2 through single conduction of a diode VD (vacuum degassing), then, the relay K1 is powered on to attract a control power supply input end and a normally closed contact end to be opened, and the relay K2 is powered on to attract three control power supply input ends and three normally open contact ends to be closed respectively. Since the 1 pin of the photoelectric switches a4, a5 and the normally closed contact end of the relay K1 are connected, the photoelectric switches a4, a5 do not get powered at this moment. Since the three power input terminals of the motor speed reducing mechanism M3 are connected to the three normally open contact terminals of the relay K3, the motor speed reducing mechanism M3 can now act as its rotating shaft to drive the movable plate 32 to rotate. Since the length of the movable plate 32 is only slightly less than the left-right width of the upper end of the vibrating screen 102 by 3cm, the rotating movable plate 32 (metal) can push out a large amount of coal blocks on the middle part of the screen from the left-right side ends of the screen 102 to the ground, and the pushed coal falls on the ground through the inclined plate 105 (the coal blocks are generally higher than the distance from the lower end of the movable plate to the two sides of the upper end of the screen 102 because the lower end of the movable plate is spaced from the upper end of the screen 102 by a certain distance). During the motor reducing mechanism pushes out coal, because the vibrating screen body 1 is still in a working state, the coal at the rear upper end of the screen can normally move forwards and downwards for screening (the coal layer on the screen does not block the infrared light beam emitted by the emitting head of the photoelectric switch A2 any more).

As shown in fig. 1 and 2, after the pins 3 and 4 of the time-controlled switch a3 stop outputting power, the relay K1 loses power and the control power input terminal and the normally closed contact terminal thereof are closed (the relay K2 loses power and the three control power input terminals and the three normally open contact terminals thereof are respectively opened). The photoelectric switches A4 and A5 are powered on to work. In practical situations, after the motor reduction mechanism M3 drives the movable plate to rotate and stop moving, when the upper ends of the movable plate and the screen are in a horizontal line from front to back, the detecting heads of the photoelectric switches a4 and a5 are respectively spaced from the rear left end and the front right end of the movable plate 32 by more than 60cm, so that no high level is output by the pins 3 of the photoelectric switches a4 and a 5. After the motor reducing mechanism M3 drives the movable plate to stop moving, when the movable plate rotates leftwards or rightwards for a larger angle, and the distance between the detection head of the photoelectric switch A4 or A5 and the rear left end or the front right end of the movable plate 32 is less than 60cm, the infrared beam emitted by the emission head of the photoelectric switch A4 or A5 is blocked, thus, the 3 feet of the photoelectric switch A4 or A5 can output high level and enter the anode power supply input end of the relay K2 through the unidirectional conduction of the diode VD1 or VD2 (the 3 feet of any photoelectric switch can output power to cause the relay K2 to be electrified and attracted), the relay K2 is electrified and attracted, the three control power supply input ends and the three normally open contact ends are respectively closed, because the three power input ends of the motor reducing mechanism M3 are connected with the three normally open contact ends of the relay K3, so at this moment, the motor speed reducing mechanism M3 can be operated by the electric motor to continue to rotate the movable plate 32. When the movable plate 62 rotates to be in a position which is transversely close to a straight line with the upper end of the screen again from front to back (with 10 cm movement allowance), the detecting head of the photoelectric switch A4 or A5 is spaced from the left end or the right end of the rear of the movable plate 32 again by more than 60cm, so that the 3 pins of the photoelectric switches A4 and A5 do not output power any more, the three control power input ends and the three normally open contact ends of the relay K2 are respectively opened when the relay K2 is powered off, and the motor speed reducing mechanism M3 does not work any more. This novel photoelectric switch A4, A5's function mainly guarantees that fly leaf 32 releases and stops up can not be in about horizontal state behind the coal cinder on the screen cloth, brings the influence to the screening work of follow-up shale shaker body 1. The models of the diodes VD, VD1 and VD2 are 1N 4007; the relays K, K1, K2 are DC12V direct current relays.

Having shown and described the basic principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, it should be understood that although the present description refers to embodiments, the embodiments do not include only one independent technical solution, and such description is only for clarity, and those skilled in the art should take the description as a whole, and the technical solutions in the embodiments may be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims (8)

1. A fine coal screening device comprises a vibrating screen body and is characterized by also comprising a detection device, a blockage removal device and a vibrating feeding device; the vibrating feeding equipment comprises a feeding bin and a vibrating motor, wherein the feeding bin is arranged at the high position of the frame of the vibrating screen body, and the vibrating motor is arranged at the lateral outer end of the feeding bin; the blockage removing equipment comprises a motor reducing mechanism and a movable plate, wherein the motor reducing mechanism is arranged at the lower end of a screen of the vibrating screen body, a power output shaft of the motor reducing mechanism is positioned at the upper end of the screen, and the movable plate is arranged at the upper end of the power output shaft of the motor reducing mechanism; the detection equipment comprises three photoelectric switches, a voltage-stabilized power supply and a control sub-circuit, wherein the three photoelectric switches are respectively arranged at the upper ends of two sides of the frame of the vibrating screen body, and the length of the movable plate is smaller than the width of the upper end of the vibrating screen; the stabilized voltage power supply and the control sub-circuit are arranged in the element box; the power output end of the stabilized voltage power supply is electrically connected with the first photoelectric switch at the rear part of the upper side end of the rack and the two ends of the power input of the control sub-circuit respectively, and the power output end of the first photoelectric switch is electrically connected with the input end of the trigger power supply of the control sub-circuit; the power supply output end of the control sub-circuit is electrically connected with the power supply input ends of the second photoelectric switch and the third photoelectric switch on two sides of the front part of the upper side end of the rack respectively; the signal output ends of the second and third photoelectric switches are electrically connected with the control signal input end of the control sub-circuit, and the power supply output end of the control sub-circuit is electrically connected with the power supply input end of the motor speed reducing mechanism.

2. The fine coal screening apparatus as claimed in claim 1, wherein when the movable plate is in close alignment from front to back on the screen, the movable plate and the probes of the first photoelectric switch are not in a horizontal alignment, and the movable plate and the probes of the second photoelectric switch and the third photoelectric switch are in a horizontal alignment.

3. The fine coal screening apparatus as claimed in claim 1, wherein the height of the probing heads of the second and third photoelectric switches is lower than the height of the movable plate, and the height of the probing head of the first photoelectric switch is the height of the highest limited coal seam on the screen set by the user.

4. The fine coal screening apparatus of claim 1, wherein the vibrating screen has inclined plates at both side ends thereof.

5. The fine coal screening apparatus of claim 1, wherein the lower end of the movable plate is spaced apart from the upper end of the screen cloth of the vibrating screen body.

6. The fine coal screening apparatus of claim 1, wherein the regulated power supply of the detection device is an ac to dc switching power supply module.

7. The fine coal screening device according to claim 1, wherein the control sub-circuit of the detection device comprises a time control switch, a relay and a diode, wherein the positive power output end of the time control switch is connected with the positive power input end of the first relay and the positive electrode of the first diode, the negative electrodes of the first, second and third diodes are connected with the positive power input end of the second relay, and the negative power output end of the time control switch is connected with the negative power input ends of the two relays; the time control switch is a full-automatic microcomputer time control switch.

8. The fine coal screening apparatus of claim 1, wherein the first photoelectric switch is provided with a relay electrically connected thereto, the power output terminal, the negative power input terminal and the relay power input terminal of the first photoelectric switch are connected to each other, and the relay control power input terminal is connected to the positive power input terminal of the photoelectric switch.

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