Overload prevention device for wind power separator

Abstract

To provide a technology to detect the stagnation of a flow of waste plastics or lightweight plastics at an early stage in a wind force sorter for executing sorting of waste plastics.SOLUTION: There is provided a monitoring device (30) for a wind force sorter for monitoring waste plastics (11) or lightweight plastics (15) flowing in a duct (12), which is attached to a wind force sorter (10) for sorting the waste plastics (11) into the lightweight plastics (15) and others (16). The monitoring device (30) consists of a first window (31) provided on the side face of the duct (12), a second window (32) provided on the side face of the duct (12) so as to be coaxial with the first window (31), and light projecting means (34) disposed outside the first window (31) in which projected light passes through the first window (31), traverses the inside of the duct (12), and passes through the second window (32).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a monitoring device and an overload prevention device attached to a wind power separator.

Background Art

[0002] FIG. 13 is a schematic diagram of a conventional wind power separator. By the fan 101, air (wind) is flowing upward in the duct 102. The flow velocity of this wind is V1. By the feeder 103, waste plastic 104 is introduced into the middle of the duct 102. The waste plastic 104 is a mixture of various plastics. In addition, although in trace amounts, metal scraps and small stones are mixed in the waste plastic 104.

[0003] The falling speed (floating speed) of the lightweight plastic 105 is smaller than V1. Therefore, the lightweight plastic 105 flows upward. On the other hand, the falling speed (floating speed) of the heavy plastic 106, metal scraps, and small stones is larger than V1. Therefore, the heavy plastic 106 together with the metal scraps and small stones falls. As described above, the lightweight plastic 105 and the others (heavy plastic 106 together with metal scraps and small stones) are separated.

[0004] Specific structures of wind power separators that separate waste plastics by the force of wind have been variously proposed (see, for example, Patent Document 1 (FIG. 3)).

[0005] Patent Document 1 will be described based on the following figures. FIG. 14 is a diagram for explaining the specific structure of a conventional wind power separator. The wind power separator 110 mainly includes a fan 101, a zigzag-shaped duct 102, a feeder 103 such as a screw conveyor, and a cyclone separator 111. The fan 101 is driven by a fan motor 112, and the feeder 103 is driven by a feeder motor 113.

[0006] The waste plastic 104 is fed into the duct 102 by the feeder 103. The selected lightweight plastic 105 is sent to the cyclone separator 111 by the wind sent by the fan 101. The remainder (heavy plastic 106 together with metal scraps and stones) is discharged downward.

[0007] Incidentally, the waste plastic 104 is a mixture of various plastics and its surface is inevitably dirty. Although rare, the dirt may exert an adhesive effect and some of the mixture may form lumps. In particular, when the duct 102 has a zigzag shape, the lightweight plastic 105 collides with the inner wall of the duct 102, and since this collision is repeated, the frequency of lump appearance increases. When this lump grows large, the flow of the waste plastic 104 or the lightweight plastic 105 is blocked.

[0008] When the flow is blocked, the load on the fan motor 112 increases. When the flow is significantly blocked, the fan motor 112 is in an overload state. When the flow is significantly blocked, in addition to the fan motor 112, the load on the feeder motor 113 increases and the feeder motor 113 is also in an overload state.

[0009] Generally, the fan motor 112 is equipped with a thermal relay 112A as a motor protection mechanism, and the feeder motor 113 is also equipped with a thermal relay 113A. The thermal relays 112A and 113A are safety switches mainly composed of bimetal. They are switched on below the set temperature and switched off when the set temperature is exceeded. Switching off is equivalent to the breaker tripping or the fuse blowing.

[0010] When in an overload state, the motors 112 and 113 generate heat, and the thermal relays 112A and 113A are switched off, cutting off the power supply. By cutting off the power supply, the motors 112 and 113 are protected. Thus, damage to the air classifier 110 is avoided.

[0011] However, since the motor cases (motor housings), which are the main components of the motors 112 and 113, are made of sturdy castings, they have a large heat capacity and the temperature change is slow. Therefore, it takes a considerable amount of time from the occurrence of an abnormal state until the thermal relays 112A and 113A cut off the power supply. During this period, the damage becomes severe. That is, when the thermal relay 112A and / or the thermal relay 113A detects an abnormality, it becomes a so-called "serious fault", and the time and cost for recovery measures increase.

[0012] Therefore, a technology that can detect the stagnation of the flow of waste plastic 104 or lightweight plastic 105 at an early stage is required.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0014] An object of the present invention is to provide a technology capable of detecting the stagnation of the flow of waste plastic or lightweight plastic at an early stage in a wind power separator for sorting waste plastic.

Means for Solving the Problems

[0015] As shown in FIG. 1, the inventors provided an opening in the duct 102 and fitted a transparent acrylic plate 115 thereinto. Since the other reference numerals are the same as those in FIG. 13, the reference numerals in FIG. 13 are used and the detailed description is omitted.

[0016] The inside of the duct 102 was observed through the acrylic plate 115. Initially, the lightweight plastic 105 was visible. However, as time passed, dirt adhered to the inner surface of the acrylic plate 115, making it difficult to see. Furthermore, as time passed, the dirt accumulated and became increasingly difficult to see.

[0017] As a countermeasure, the acrylic plate 115 was removed, cleaned, and reinstalled. However, the fan 101 had to be stopped during cleaning. Stopping the fan 101 caused a decrease in productivity. In addition, the attachment, detachment, and cleaning of the acrylic plate 115 also burdened the workers.

[0018] In considering further countermeasures, the inventors focused on the principle of "shadow painting". As shown in FIG. 2, when an object 123 is placed between the shoji paper 121 and the light 122, bright part 125 and shadow part 126 are formed on the shoji paper 121 by the light rays 124 of the light 122.

[0019] The shoji paper 121 corresponds to the soiled acrylic plate. The soiled acrylic plate corresponds to a semi-transparent acrylic plate. Therefore, it was noticed that regardless of the degree of dirt on the acrylic plate, the shadow part 126, that is, the shadow of the lightweight plastic, could be detected by the acrylic plate.

[0020] As shown in FIG. 3, the air classifier 10 includes a duct 12, a waste plastic feeder 13 for introducing waste plastic 11 into the middle of the duct 12, and a fan 14 for sending air into the duct 12, sorting the lightweight plastic 15 upward and sorting the heavy plastic 16 downward together with metal chips and small stones.

[0021] Based on the findings described in FIG. 2, a monitoring device 30 for air classifier (hereinafter referred to as monitoring device 30) was attached to the air classifier 10. The details of the monitoring device 30 will be described based on FIG. 4.

[0022] As shown in Fig. 4, the monitoring device 30 includes a first window 31 provided in the duct 12, a second window 32 provided in the duct 12 so as to be coaxial with and face the first window 31, and a light projecting means 34 disposed outside the first window 31 through which the light projection 33 passes through the first window 31, crosses the inside of the duct 12, and passes through the second window 32. Note that being coaxial means that the first window 31 and the second window 32 are arranged on one axis with a predetermined interval therebetween.

[0023] The first window 31 and the second window 32 are preferably made of an inexpensive and transparent acrylic plate, but may also be made of polycarbonate or glass. The type and form of the light projecting means 34 are arbitrary, and it may be a reflector (with a mirror) projector used at a construction site. The reflector projector is easily available and inexpensive. The bulb of the reflector projector may be an LED bulb (light emitting diode bulb) in addition to a filament bulb.

[0024] Preferably, the light projecting means 34 is supported by the duct 12 with a conical stay 35 that also serves as a dust cover. A plurality of air inlets 36 and air outlets 37 are provided in the stay 35 so that heat does not accumulate. When the light projecting means 34 is placed in an environment without dust or with little dust, the stay 35 may be simply a leg (four legs). Also, when vibration from the duct 12 is to be avoided, the light projecting means 34 may be supported by a structure (such as a building or a corridor) placed separately from the duct 12.

[0025] Figs. 5(a) and (b) are views taken in the direction of arrow 5 in Fig. 4. As shown in Fig. 5(a), when looking at the second window 32, normally, there were a bright portion 38 and a shadow portion 39 existing in a certain ratio. The area of the visual field with a vertical side of a and a horizontal side of a is a×a. The sum of the areas of the shadow portions 39 in this visual field is defined as the shadow area. The shadow area can be obtained by an image analysis method. By using the area of the visual field (a×a) as the denominator and the area of the shadow (sum of areas) as the numerator, the shadow area ratio can be easily calculated.

[0026] As shown in FIG. 5(b), when looking at the second window 32, in the case of an abnormality, there were fewer bright portions 38 and more shadow portions 39. Since the brightness difference between the bright portion 38 and the shadow portion 39 is sufficiently large, in FIGS. 5(a) and 5(b), even if the inner surface of the second window 32 is dirty, the shadow area ratio can be accurately calculated. A threshold value is set between FIGS. 5(a) and 5(b). By comparing this threshold value with the shadow area ratio, it becomes possible to distinguish between normal and abnormal.

[0027] As described above, the inventors have found that a translucent acrylic plate imitating shoji paper is more suitable than a completely transparent acrylic plate for the second window 32. That is, it has been found that a translucent acrylic plate that weakens light is less affected by dirt than a completely transparent acrylic plate. A specific example of the translucent acrylic plate will be described with reference to FIG. 6.

[0028] In FIGS. 6(a) to (c), "inside" is the duct Inside the hopper , and "outside" is the duct Outside the hopper is shown. As shown in FIG. 6(a), the outer surface of the second window 32 is a transparent plastic plate 42 is the rough surface 41. The rough surface 41 can be formed by embossing, satin finishing, blasting, etc. Embossing means a fine uneven pattern that appears on the surface of a fabric or leather. Satin finish means a fine uneven pattern on the surface of a Japanese pear (nashi), which is a kind of fruit. Blasting means a fine uneven pattern that appears by spraying sand grains. As described above, the transparent acrylic plate 42 becomes translucent.

[0029] Further, as shown in FIG. 6(b), the second window 32 may be formed by attaching a film that weakens light, specifically a translucent film 43, to the outer surface of a transparent plastic plate 42. The film 43 may be a coating film. Further, the film 43 may be a colored film that weakens light.

[0030] Further, as shown in FIG. 6(c), the second window 32 may be composed of a transparent plastic plate 42 and a filter that weakens light, specifically a translucent filter 44, disposed outside the transparent plastic plate 42. Further, although not shown in the drawings, the second window 32 may be a colored plastic that exhibits a light-weakening effect compared to the transparent plastic 42.

[0031] That is, by making the second window translucent, the light projection by the light projection means can be uniformly diffused, and the waste plastic or lightweight plastic flowing through the duct can be projected more sharply.

[0032] Based on the above findings, the invention described below has been completed. The invention according to claim 1 is A duct, a waste plastic feeder for feeding waste plastic into the middle of this duct, a feeder motor for driving this waste plastic feeder, a fan for sending air into the duct, and a fan motor for driving this fan, and the waste plastic is attached to a wind power separator for sorting it into lightweight plastic and others. At least one of the feeder motor and the fan motor is an overload prevention device for a wind power separator that prevents an overload state. This overload prevention device includes a first window provided in the duct, a second window provided in the duct so as to be coaxial with the first window, and a light projecting means provided outside the first window for the light projection to pass through the first window, cross the inside of the duct, and pass through the second window, and at least one of a fan motor rotation control means for controlling the rotation speed of the fan motor and a feeder motor rotation control means for controlling the rotation speed of the feeder motor. The overload prevention device further includes an imaging means disposed outside the second window for imaging the shadow of the waste plastic or the shadow of the lightweight plastic reflected in the second window. An area calculation unit for obtaining the area of the visual field and the area of the shadow based on the imaging information of the imaging means, a shadow area ratio calculation unit for calculating the shadow area ratio with the area of the visual field as the denominator and the area of the shadow as the numerator, a comparison unit for comparing the shadow area ratio calculated by this shadow area ratio calculation unit with a threshold value, and a fan strengthening unit for controlling the fan motor rotation control means to increase the rotation speed of the fan motor when the shadow area ratio exceeds the threshold value. characterized by the following.

[0033] The invention according to claim 2 is A duct, a waste plastic feeder for feeding waste plastic into the middle of this duct, a feeder motor for driving this waste plastic feeder, a fan for sending air into the duct, and a fan motor for driving this fan, and the waste plastic is attached to a wind power separator for sorting it into lightweight plastic and others. At least one of the feeder motor and the fan motor is an overload prevention device for a wind power separator that prevents an overload state. This overload prevention device includes a first window provided in the duct, a second window provided in the duct so as to be coaxial with the first window, a light projecting means provided outside the first window through which light projection passes through the first window, crosses inside the duct, and passes through the second window, and at least one of a fan motor rotation control means for controlling the rotation speed of the fan motor and a feeder motor rotation control means for controlling the rotation speed of the feeder motor. The overload prevention device further includes an imaging means disposed outside the second window for imaging the shadow of the waste plastic or the shadow of the lightweight plastic reflected on the second window. An area calculation unit for obtaining the area of the visual field and the area of the shadow based on the imaging information of the imaging means, and a shadow area ratio calculation unit for calculating with the area of the visual field as the denominator and the area of the shadow as the numerator. When the shadow area ratio calculated by this shadow area ratio calculation unit exceeds the threshold value, it further includes a feeder weakening unit for controlling the feeder motor rotation control means to reduce the rotation speed of the feeder motor. characterized by the following.

[0035] The invention according to claim 3 is an overload prevention device for a wind power sorting machine according to claim 1 or Claim 2 described, and The second window is one of the following: one with dimples formed on the outer surface of a transparent plastic plate to uniformly diffuse the light projection by the light projection means and sharply project the waste plastic or the lightweight plastic flowing through the duct; one with a translucent film attached to the outer surface of a transparent plastic plate; one with a translucent filter provided outside a transparent plastic plate; one with a light-reducing coating film applied to the outer surface of a transparent plastic plate; or a transparent but colored plastic plate, and is characterized in being any of these.

Advantages of the Invention

[0043] Claim 1 or Claim 2 In the invention according to claim, the overload prevention device for the air classifier is composed of a first window, a second window, a light projection means arranged outside the first window through which the light projection passes through the first window, crosses the inside of the duct, and passes through the second window, and at least one of a fan motor rotation control means and a feeder motor rotation control means. No. The two windows are regarded as the shoji paper for shadow play. The waste plastic or lightweight plastic flowing through the duct is displayed as a shadow on the second window. Even if the second window is soiled by the dirt of the waste plastic, it has little effect on the formation of the shadow. When there are many shadow parts, it can be identified as abnormal.

[0044] When it is identified as abnormal, the fan motor rotation control means is controlled to increase the speed to promote the flow and forcibly eliminate the stagnation of the flow. By this elimination, it is possible to prevent the fan motor from being in an overload state. Alternatively, when it is identified as abnormal, the feeder motor rotation control means is controlled to decelerate to reduce the input amount of the waste plastic and correct the stagnation of the flow. By this correction, it is possible to prevent the feeder motor from being in an overload state. Therefore, according to the present invention, in an air classifier for sorting waste plastics, it is possible to quickly eliminate the stagnation of the flow of waste plastics or lightweight plastics and prevent overload.

[0045] In addition, inexpensive and easily available acrylic plates can be adopted for the first window and the second window. As the light projecting means, a reflector projector for construction sites, which is inexpensive and easily available, can be adopted. Therefore, the present invention provides an overload prevention device for a wind power sorter, which has an extremely simple structure and is inexpensive.

[0047] Claim 1 or Claim 2 In the invention according to the claim, the overload prevention device further includes imaging means for imaging the shadow reflected on the second window. The imaging can be visually monitored with a monitor. The monitor can be placed in a room (operation room or management room) where the environmental conditions are much better than at the site. Remote monitoring is possible, which is preferable compared to the situation where an operator directly monitors the second window.

[0048] Claim 1 In the invention according to the claim, the area ratio of the shadow is calculated based on the imaging information. If this calculated value exceeds the threshold value, the rotational speed of the fan motor is increased to eliminate the stagnation of the flow in the duct, and after the elimination, the rotational speed of the fan motor is returned to normal. Overload prevention can be achieved without human intervention.

[0049] Claim 2 In the invention according to the claim, the area ratio of the shadow is calculated based on the imaging information. If this calculated value exceeds the threshold value, the rotational speed of the feeder motor is decreased to reduce the amount of waste plastic input into the duct and eliminate the stagnation of the flow in the duct. After the elimination, the rotational speed of the feeder motor is returned to normal. Overload prevention can be achieved without human intervention. In the invention according to Claim 3, the second window is made semi-transparent in order to uniformly diffuse the light projection by the light projecting means and project the waste plastic or lightweight plastic flowing through the duct sharply. Semi-transparent can form the shadow of the shadow picture sharper than transparent. Also, semi-transparent is less affected by dirt than transparent.

Brief Description of the Drawings

[0050]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0051] Embodiments of the present invention will be described below based on the accompanying drawings.

Examples

[0052] As shown in Fig. 7, the wind separator 10 is disposed between a crusher 17 that crushes waste plastic into an appropriate size and a metering feeder 18 that supplies a determined amount of lightweight plastic to the next process. The metering feeder 18 is provided with a dust collector 19 at the upper part. The dust collector 19 serves to remove dust from the circulating air supplied to the fan 14.

[0053] The air classifier 10 includes a duct 12 through which waste plastic 11 or lightweight plastic 15 flows, a waste plastic feeder 13 that feeds waste plastic 11 into an inlet 12a provided in the middle of the duct 12, a feeder motor 13A that drives the waste plastic feeder 13, a fan 14 that sends air into the duct 12, and a fan motor 14A that drives the fan 14.

[0054] In addition, the air classifier 10 is provided with an overload prevention device 50 for an air classifier (hereinafter referred to as the overload prevention device 50) that prevents at least one of the feeder motor 13A and the fan motor 14A from entering an overload state.

[0055] The overload prevention device 50 includes a first window 31 provided in the duct 12, a second window 32 provided in the duct 12 so as to be coaxial with the first window 31, a light projecting means 34 provided outside the first window 31 through which light projection passes through the first window 31, crosses inside the duct 12, and passes through the second window 32, and a fan motor rotation control means 51 that controls the rotation speed of the fan motor 14A.

[0056] The fan motor rotation control means 51 can change (increase or decrease) the rotation speed of the fan motor 14A by turning a first volume 52. If the fan motor 14A is an AC motor, the fan motor rotation control means 51 is preferably a VVVF (variable voltage and variable frequency) inverter.

[0057] Preferably, a feeder motor rotation control means 53 that controls the rotation speed of the feeder motor 13A is added to the overload prevention device 50. The feeder motor rotation control means 53 can change (increase or decrease) the rotation speed of the feeder motor 13A by turning a second volume 54. If the feeder motor 13A is an AC motor, the feeder motor rotation control means 53 is also preferably a VVVF (variable voltage and variable frequency) inverter.

[0058] Preferably, an imaging means 55 disposed outside the second window 32 for imaging the shadow of the lightweight plastic 15 reflected on the second window 32 and a monitor 56 for displaying imaging information are provided. As the imaging means 55, a CCD camera is suitable. In addition, the first window 31 and the second window 32 may be provided at a portion where the waste plastic 11 flows in the duct 12. In this case, the imaging means 55 images the shadow of the waste plastic 11 reflected on the second window 32.

[0059] The operator monitors the monitor 56 regularly or at any time. When the image shown in Fig. 5(b) is displayed on the monitor 56, the operator operates the first volume 52 to increase the rotation speed of the fan motor 14A. When the image of Fig. 5(a) cannot be restored by this operation, the operator operates the second volume 54 to decrease the rotation speed of the feeder motor 13A. By this operation, the amount of waste plastic 11 introduced into the duct 12 decreases, so that the image of Fig. 5(a) can be restored.

[0060] When the imaging means 55 and the monitor 56 are omitted, the operator directly views the second window 32 and operates the first volume 52 and the second volume 54 as appropriate.

[0061] In order to reduce the burden on the operator described above, a modified embodiment with further automation will be described below. As shown in Fig. 8, the overload prevention device 50 further includes a control unit 60 that controls the fan motor rotation control means 51 and / or the feeder motor rotation control means 53 based on the imaging information of the imaging means 55. Since the other components are the same as those in Fig. 7, the reference numerals in Fig. 7 are used and the detailed description is omitted.

[0062] As elements for displaying the operating state of the fan motor 14A, a "fan normal" lamp 61 and a "fan boost" lamp 62 may be provided. When the fan motor 14A is at the normal rotation speed, the "fan normal" lamp 61 is lit and the "fan boost" lamp 62 is turned off. In case of an abnormality, turn on the "Fan Reinforcement" lamp 62 and turn off the "Normal Fan" lamp 61.

[0063] Also, as elements for displaying the operating state of the feeder motor 13A, a "Normal Feeder" lamp 63 and a "Weak Feeder" lamp 64 may be provided. When the feeder motor 13A is rotating at a normal speed, turn on the "Normal Feeder" lamp 63, and when there is an abnormality, turn on the "Weak Feeder" lamp 64.

[0064] Note that by displaying these operation displays on the monitor 56, the lamps 61 to 64 may be omitted. Also, when the fan is reinforced or the feeder is weak, a buzzer may be sounded to alert the operator.

[0065] As shown in FIG. 9, the control unit 60 includes an area calculation unit 65 that obtains the area of the visual field (a×a shown in FIG. 5(a)) and the area (sum of areas) of the shadow (reference numeral 39 in FIG. 5(a)) based on the imaging information, a shadow area ratio calculation unit 66 that obtains the shadow area ratio with the area of the visual field (a×a) as the denominator and the area of the shadow as the numerator, a comparison unit 67 that compares the shadow area ratio calculated by the shadow area ratio calculation unit 66 with a threshold value, a fan reinforcement unit 68 that controls the fan motor rotation control means 51 to increase the rotation speed of the fan motor 14A when the shadow area ratio exceeds the threshold value, a feeder weakening unit 69 that controls the feeder motor rotation control means 53 to decrease the rotation speed of the feeder motor 13A when the shadow area ratio exceeds the threshold value, and a switch unit 71 that sends information to both or one of the fan reinforcement unit 68 and the feeder weakening unit 69.

[0066] That is, based on a command from the outside, the switch unit 71 selects only the fan reinforcement unit 68, or only the feeder weakening unit 69, or both the fan reinforcement unit 68 and the feeder weakening unit 69.

[0067] An example of the control flow when only the fan reinforcement unit 68 is selected by the switch unit 71 will be described with reference to FIG. 10. In ST01 (step number 01 in FIG. 10, the same applies hereinafter) of FIG. 10, a threshold value B1 related to the shadow area ratio is set in advance. The shadow area ratio B2 is read (ST02) and accumulated (ST03) every certain period (e.g., 0.1 second or 1.0 second). This accumulation continues until a predetermined period (e.g., 10 seconds or 100 seconds) has elapsed (ST04).

[0068] When it is determined in ST04 that the predetermined time has elapsed, for example, 100 shadow area ratios B2 are accumulated. By adding the 100 shadow area ratios B2 and dividing by the total number (100), the arithmetic mean value B2m of the shadow area ratio B2 is obtained (ST05).

[0069] The reason for using the average value is as follows. The lightweight plastic flowing through the duct varies in quantity moment by moment. This variation includes a shadow area ratio B2 that exceeds the threshold value. If the fan motor is shifted in speed every time the shadow area ratio B2 exceeds the threshold value, the shifting frequency increases, and so-called chattering (repeating normal → speed increase → normal → speed increase → ··· in a short time) occurs, which places a strain on the fan motor. To prevent this chattering, for example, 100 shadow area ratios B2 are averaged. With the average value, the influence of the variation is almost eliminated.

[0070] In ST06, it is examined whether the average value B2m exceeds the threshold value B1. If not, the normal rotation speed of the fan motor is maintained, or the speed increase is cancelled and the normal rotation speed is set (ST07), the accumulated shadow area ratio B2 and the calculated B2m are reset (cancelled) (ST08), the "Fan Normal" lamp is lit and the "Fan Reinforcement" lamp is turned off (ST09), and the process returns to ST02.

[0071] When it is determined in ST06 that the average value B2m exceeds the threshold value B1, the shadow area ratio B2 and the calculated B2m are reset (cancelled) (ST10), the fan motor is speeded up (ST11), the "Fan Normal" lamp is turned off and the "Fan Reinforcement" lamp is lit (ST12), and the process returns to ST02.

[0072] When the fan motor is speeded up (the rotational speed is increased), the lightweight plastic that tends to stay is forcibly washed away. The speed increase of the fan motor continues until it becomes NO in ST06. It is expected that the state approximated to Fig. 5(b) will return to the state of Fig. 5(a) due to this continuation. When it becomes NO (the average value B2m is less than or equal to the threshold value B1) in ST06, the rotational speed of the fan motor is returned from the speed increase to normal in ST07.

[0073] Next, an example of the control flow when only the feeder weakening part 69 is selected by the switch part 71 in Fig. 9 will be described with reference to Fig. 11. Since ST21 to ST26 shown in Fig. 11 are the same as ST01 to ST06 shown in Fig. 10, the description in Fig. 10 is incorporated by reference.

[0074] In ST26, it is checked whether the average value B2m exceeds the threshold value B1. If NO, the normal rotational speed of the feeder motor is maintained, or the deceleration is canceled and it becomes the normal rotational speed (ST27), the accumulated shadow area ratio B2 and the calculated B2m are reset (cancelled) (ST28), the "feeder normal" lamp is lit and the "feeder weak" lamp is turned off (ST29), and the process returns to ST02.

[0075] When it is determined in ST26 that the average value B2m exceeds the threshold value B1, the shadow area ratio B2 and the calculated B2m are reset (cancelled) (ST30), the feeder motor is decelerated (ST31), the "feeder normal" lamp is turned off and the "feeder weak" lamp is lit (ST32), and the process returns to ST02.

[0076] When the feeder motor is decelerated (the rotational speed is decreased), the input amount of the lightweight plastic decreases. This decrease continues until it becomes NO in ST26. It is expected that the state approximated to Fig. 5(b) will return to the state of Fig. 5(a) due to this continuation. When it becomes NO (the average value B2m is less than or equal to the threshold value B1) in ST26, the rotational speed of the feeder motor is returned from the deceleration to normal in ST27.

[0077] When both the fan strengthening section 68 and the feeder weakening section 69 are selected by the switch section 71 in Fig. 9, the control flow is a combination of Figs. 10 and 11, so the illustration and description are omitted.

[0078] Note that the operation method (control method) of the air classifier 10 shown in Fig. 8 is not limited to Figs. 10 and 11, and Figs. 10 and / or 11 can be appropriately changed. The key is that any control flow that enables the unmanned operation (automatic operation) of the air classifier 10 is acceptable.

[0079] The monitoring device 30 or the overload prevention device 50 described above is suitable for the air classifier 10, but can be attached to a general-purpose air conveyance pipe. A specific example will be described with reference to Fig. 12.

[0080] As shown in Fig. 12(a), the air conveyance pipe 80 consists of a duct 12, a fan 14 that sends air into this duct 12, a hopper 81 provided in the middle of the duct 12, and a rotary valve 82 arranged between this hopper 81 and the duct 12.

[0081] The rotary valve 82 has blade-like partitions 84 provided at equal pitches (90° pitch in this example) on a valve shaft 83 that is rotated intermittently. In this example, four chambers 85 are partitioned by the partitions 84. The crushed waste plastic 11 falls from the hopper 81 and is stored in a certain chamber 85. When the valve shaft 83 is rotated 180°, the stored waste plastic 11 falls into the duct 12.

[0082] During the rotation of the valve shaft 83, since the plurality of partitions 84 exert a sealing effect, the air in the duct 12 does not leak to the hopper 81 side. As described above, the waste plastic 11 is transported in the duct 12 by air.

[0083] By the way, the waste plastic 11 may become dirty and act as an adhesive to form lumps. In addition, although the duct 12 is ideally straight, in reality, a bent portion 12b is provided midway. The mass is blocked by the bent portion 12b, stays there, and grows. When it stays, the load on the fan motor 14A increases, and countermeasures are desired.

[0084] As a countermeasure, the monitoring device 30 or the overload prevention device 50 of the present invention is attached to a necessary location of the air supply pipe 80 (for example, the primary side of the bent portion 12b). The primary side means the upstream side, and in this example, it means the fan 14 side of the bent portion 12b.

[0085] FIG. 12(b) is a cross-sectional view taken along line b-b of FIG. 12(a). The duct 12 is a rectangular tube having an upper surface, two side surfaces, and a bottom surface. A first window 31, which is a component of the monitoring device 30, is provided on one side surface, a light projecting means 34 is provided outside this first window 31, and a second window 32 is provided on the other side surface.

[0086] When a worker visually observes, the side surface is easier to see than the upper surface or the bottom surface. Also, when the duct 12 is arranged horizontally, the bottom surface gets the dirtiest. It is recommended to provide the first window 31 and the second window 32 on the side surface, which is less likely to get dirty than the bottom surface. On the other hand, when the duct 12 is arranged vertically or obliquely, the first window 31 and the second window 32 are provided on an arbitrary surface.

[0087] The above configuration can be summarized as follows. It is a device attached to an air supply pipe that transports waste plastic by air, It is a monitoring device for an air supply pipe that monitors the waste plastic flowing through the duct, This monitoring device is characterized by including a first window provided in the duct, a second window provided in the duct so as to be coaxial with the first window, and a light projecting means arranged outside the first window, through which light passes through the first window, crosses the inside of the duct, and passes through the second window.

[0088] FIG. 12(c) is a cross-sectional view when an overload prevention device 50 is provided instead of the monitoring device 30. When the duct 12 is placed horizontally, the bottom surface gets the dirtiest and the top surface gets the least dirty. In this overload prevention device 50, a second window 32 is provided on the bottom surface and a first window 31 is provided on the top surface. Since the first window 31 maintains relatively high transparency, relatively strong light projection 33 can be irradiated into the duct 12 from the light projection means 34 provided above the first window 31. On the other hand, since the second window 32 is preferably semi-transparent rather than transparent, it is arranged on the bottom surface. An imaging means 55 is arranged below the second window 32.

[0089] Other components of the overload prevention device 50 are applied mutatis mutandis with reference to FIGS. 7 to 9 and detailed description thereof is omitted. However, FIG. 7 is applied mutatis mutandis after excluding the feeder motor rotation control means 53 and the second volume 54 from the overload prevention device 50.

[0090] Also, FIG. 8 is applied mutatis mutandis after excluding the feeder motor rotation control means 53, the "feeder normal" lamp 63, and the "feeder weak" lamp 64 from the overload prevention device 50. Also, FIG. 9 is applied mutatis mutandis after excluding the switch section 71, the feeder weakening section 69, the feeder motor rotation control means 53 and Feeder motor 13A. Also, FIG. 10 is applied mutatis mutandis in its entirety.

[0091] The above configuration can be summarized as follows. An apparatus attached to a pneumatic conveying pipe including a duct, a hopper for feeding waste plastic into the middle of the duct, a fan for sending air to the duct, and a fan motor for driving the fan, wherein the fan motor is an overload prevention device for a pneumatic conveying pipe that prevents an overload state, This overload prevention device is characterized by including a first window provided in the duct, a second window provided in the duct coaxially with the first window, a light projecting means provided outside the first window through which light projection passes through the first window, traverses the inside of the duct, and passes through the second window, and a fan motor rotation control means for controlling the rotation speed of the fan motor.

[0092] In addition, the second window 32 of the present invention may be a transparent plastic plate or a transparent glass plate in addition to the translucent plastic plate. This is because a transparent plate becomes translucent when it gets dirty.

[0093] The monitoring device or overload prevention device of the present invention is suitable for an air classifier that sorts crushed waste plastics.

Explanation of Reference Numerals

[0094] 10... Air classifier, 11... Waste plastic, 12... Duct, 13... Waste plastic feeder, 13A... Feeder motor, 14... Fan, 14A... Fan motor, 15... Lightweight plastic, 16... Others (heavy plastic including metal scraps and small stones), 30... Monitoring device for air classifier (monitoring device), 31... First window, 32... Second window, 33... Light projection, 34... Light projecting means, 39... Shadow part (shadow), 41... Rough surface, 42... Transparent plastic plate, 43... Translucent film, 44... Translucent filter, 50... Overload prevention device for air classifier (overload prevention device), 51... Fan motor rotation control means, 53... Feeder motor rotation control means, 55... Imaging means, 56... Monitor, 60... Control unit, 65... Area calculation unit, 66... Shadow area ratio calculation unit, 67... Comparison unit, 68... Fan strengthening unit, 69... Feeder weakening unit.

Claims

1. An apparatus attached to an air classifier that separates waste plastics into lightweight plastics and others, comprising a duct, a waste plastic feeder for feeding waste plastics into the middle of the duct, a feeder motor for driving the waste plastic feeder, a fan for sending air into the duct, and a fan motor for driving the fan, wherein at least one of the feeder motor and the fan motor is an overload prevention device for an air classifier that prevents an overload state, the overload prevention device comprising a first window provided in the duct, a second window provided in the duct coaxially with the first window, a light projecting means provided outside the first window for the light projection to pass through the first window, cross the inside of the duct, and pass through the second window, and at least one of a fan motor rotation control means for controlling the rotation speed of the fan motor and a feeder motor rotation control means for controlling the rotation speed of the feeder motor, the overload prevention device further comprising an imaging means disposed outside the second window for imaging the shadow of the waste plastics or the shadow of the lightweight plastics reflected on the second window, an area calculation unit for obtaining the area of the visual field and the area of the shadow based on the imaging information of the imaging means, a shadow area ratio calculation unit for calculating a shadow area ratio with the area of the visual field as the denominator and the area of the shadow as the numerator, a comparison unit for comparing the shadow area ratio calculated by the shadow area ratio calculation unit with a threshold value, and a fan strengthening unit for controlling the fan motor rotation control means to increase the rotation speed of the fan motor when the shadow area ratio exceeds the threshold value. The overload prevention device for an air classifier is characterized by further comprising the above components.

2. An apparatus attached to an air classifier that separates waste plastics into lightweight plastics and others, comprising a duct, a waste plastic feeder for feeding waste plastics into the middle of the duct, a feeder motor for driving the waste plastic feeder, a fan for sending air into the duct, and a fan motor for driving the fan, wherein at least one of the feeder motor and the fan motor is an overload prevention device for an air classifier that prevents an overload state, This overload prevention device includes a first window provided in the duct, a second window provided in the duct so as to be coaxial with the first window, a light projecting means provided outside the first window through which light projection passes through the first window, traverses the inside of the duct, and passes through the second window, and at least one of a fan motor rotation control means for controlling the rotation speed of the fan motor and a feeder motor rotation control means for controlling the rotation speed of the feeder motor. The overload prevention device further includes an imaging means disposed outside the second window for imaging the shadow of the waste plastic or the shadow of the lightweight plastic reflected on the second window. An area calculation unit for obtaining the area of the visual field and the area of the shadow based on the imaging information of the imaging means, and a shadow area ratio calculation unit having the area of the visual field as the denominator and the area of the shadow as the numerator. When the shadow area ratio calculated by this shadow area ratio calculation unit exceeds the threshold value, a feeder weakening unit for controlling the feeder motor rotation control means to reduce the rotation speed of the feeder motor. An overload prevention device for a pneumatic separator, characterized by further comprising the above.

3. An overload prevention device for a pneumatic separator according to claim 1 or claim 2, The second window is any one of a transparent plastic plate whose outer surface is corrugated to uniformly diffuse the light projection by the light projecting means and sharply project the waste plastic or the lightweight plastic flowing through the duct, a transparent plastic plate with a translucent film attached to its outer surface, a transparent plastic plate with a translucent filter provided outside, a transparent plastic plate with a light-weakening coating film on its outer surface, and a transparent but colored plastic plate. An overload prevention device for a pneumatic separator, characterized by the above.

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