CN213558512U

CN213558512U - Screening system

Info

Publication number: CN213558512U
Application number: CN202022033971.XU
Authority: CN
Inventors: 贾英杰; 李亮; 彭扬平
Original assignee: SHANGHAI GUANSHENGYUAN BEE PRODUCT CO Ltd
Current assignee: SHANGHAI GUANSHENGYUAN BEE PRODUCT CO Ltd
Priority date: 2020-09-16
Filing date: 2020-09-16
Publication date: 2021-06-29
Anticipated expiration: 2030-09-16

Abstract

The utility model relates to a screening system, it includes screening plant and the weighing device who has data display, screening plant includes screening platform and the first driving piece of drive screening platform pivoted, the drive shaft of first driving piece passes through connecting piece fixed connection in one side of screening platform, one side that the screening platform kept away from first driving piece is located to the weighing device, first driving piece electricity is connected with three control interface that is used for controlling the left slope of screening platform, resets and the right bank. This application has the effect that can sieve in order to improve production quality to the product.

Description

Screening system

Technical Field

The application relates to the field of product packaging quality detection, in particular to a screening system.

Background

In industrial production, it is often necessary to quantitatively pack the product to ensure that each package of product is of consistent weight to meet the needs of the customer. For example, in the production process of the honey bags, honey is filled in an injection mode, and the quality of each honey bag has errors, so that the quality of the filled honey needs to be detected to screen out unqualified honey bags, and the product quality is improved.

The existing operation mode adopts a manual mode to directly pack and weigh the honey bags, the quality of a single bag cannot be detected in consideration of the working efficiency, and therefore the quality of the honey bag of the single bag cannot be accurately detected, the quality of a product cannot be guaranteed, and improvement is needed.

SUMMERY OF THE UTILITY MODEL

In order to improve production quality, the present application provides a screening system.

In a first aspect, the application provides a screening system, which adopts the following technical scheme:

the utility model provides a screening system, includes screening plant and the weighing device who has data display, screening plant includes screening platform and drive screening platform pivoted first driving piece, the drive shaft of first driving piece passes through connecting piece fixed connection and is in one side of screening platform, weighing device locates the screening platform is kept away from one side of first driving piece, first driving piece electricity is connected with and is used for control screening platform's left side slope, the control interface that resets and right slope state, and the reset state does the screening platform level.

By adopting the technical scheme, the weighing device weighs the mass of the product and displays mass data, and the mass data weighed by the weighing device controls three different control interfaces, so that the left inclination, the reset and the right inclination of the screening platform are controlled, and the classification of the products with different masses is realized; when the quality of the product meets the requirement, controlling the corresponding control interface to enable the screening platform to rotate towards one of the material receiving devices in an inclined mode, and accordingly enabling the qualified product to be collected into the material receiving device; when the quality of the product does not meet the requirement, the corresponding control interface is controlled, so that the unqualified product is collected into another material receiving device, and the qualified product is distinguished from the unqualified product.

Preferably, the weighing device is configured as an electronic scale.

By adopting the technical scheme, the electronic scale can be used for measuring the quality of products and displaying specific data.

Preferably, the control interface is controlled to be connected with buttons, and the buttons respectively control the left inclination, the reset and the right inclination of the screening platform correspondingly.

Through adopting above-mentioned technical scheme, the button can be by remote control, and corresponds the turned angle of control first driving piece respectively to the realization is to the left side slope of screening platform, is reset and right slope, sieves with the quality to the product.

Preferably, the weighing device and the first driving piece are electrically connected with an MCU, the control interface is electrically connected with the MCU, the first driving piece is a stepping motor, and the stepping motor is provided with three working modes which respectively correspond to the left inclination, the reset and the right inclination of the screening platform.

Through adopting above-mentioned technical scheme, carry out the electricity with weighing device and first driving piece and connect in MCU for MCU can judge the data that show weighing device according to setting up built-in procedure, and the mode of the first driving piece of control that corresponds, thereby will sieve according to the quality of product, is favorable to improving the degree of automation of system.

Preferably, the two inclined ends of the screening platform are respectively and correspondingly provided with a material receiving device.

By adopting the technical scheme, the material receiving devices positioned at the two ends of the screening platform are used for receiving screened products.

In a second aspect, the present application provides a screening system, which adopts the following technical solutions:

a screening system comprises a screening device and a weighing device, wherein the screening device comprises a screening support, a screening platform rotationally connected to the screening support and a driving assembly used for driving the screening platform to rotate in an inclined mode, the driving assembly is arranged at one end of the screening platform, the weighing device is arranged on one side face, receiving a product to be detected, of the screening platform, and material receiving devices are arranged at two inclined ends of the screening platform respectively; the driving assembly and the weighing device are electrically connected with a control circuit used for controlling the left inclination, the reset and the right inclination of the screening platform according to the mass signal of the weighing device.

By adopting the technical scheme, the product falls on the weighing device to be weighed, the action of the driving assembly is controlled by the control circuit according to the product quality signal weighed on the weighing device, so that the left inclination and the right inclination of the screening platform are controlled, the product falls into the material receiving devices at the two ends of the screening platform respectively, the different qualities of the product are screened, and after the screening is completed, the control circuit controls the resetting of the screening platform.

Preferably, the drive assembly includes second driving piece and third driving piece, and second driving piece and third driving piece set up to the cylinder, the one end of second driving piece is rotated and is connected on the screening support, the driving shaft tip fixed connection of second driving piece is in the one end of third driving piece, the driving shaft tip of third driving piece is rotated and is connected on the screening platform, the initial condition of second driving piece is the extension state, the initial condition of third driving piece is the contraction state, the initial condition of screening platform is the horizontality.

By adopting the technical scheme, when the second driving piece and the third driving piece do not act, the second driving piece keeps an extension state, and the third driving piece keeps a contraction state; when the second driving part acts and the third driving part does not act, the second driving part contracts, and the third driving part holds the contracted state, namely the screening platform inclines towards one end; when the second driving part does not act and the third driving part acts, the second driving part keeps an extending state, the third driving part is in the extending state, and the screening platform inclines towards the other end.

Preferably, the control circuit comprises a detection circuit electrically connected with the drive assembly for detecting the product quality range and a judgment circuit for controlling the drive assembly to act.

By adopting the technical scheme, the detection circuit is used for detecting the product quality range and sending the detection result to the judgment circuit, and the judgment circuit is used for controlling the driving component to act according to the detection result of the detection circuit.

Preferably, the detection circuit comprises a first comparator OA1 and a second comparator OA2, a non-inverting input end of the first comparator OA1 is electrically connected with one end of a switch S1, the other end of the switch S1 is electrically connected with one end of a resistor R1, the other end of the resistor R1 is electrically connected with a direct current power supply DC, one end of the switch S1 far away from the first comparator OA1 is electrically connected with one end of a resistor R2, and the other end of the resistor R2 is grounded; the switch S1 is used for judging whether a product falls on the weighing device and is positioned on the surface of the weighing device, the negative phase input end of the first comparator OA1 is electrically connected to the output end of the weighing device, the output end of the weighing device is electrically connected to the positive phase input end of the second comparator OA2, the negative phase input end of the second comparator OA2 is electrically connected with one end of a resistor R3, the other end of the resistor R3 is electrically connected with a direct current power supply DC, the negative phase input end of the second comparator OA2 is electrically connected with one end of a resistor R4, and the other end of the resistor R4 is grounded.

By adopting the technical scheme, when no product exists on the weighing device, the switch S1 is turned on, the detection circuit is not powered, the driving assembly does not act, and the screening platform is in a horizontal state; when a product falls on the weighing device, the switch S1 is closed, the detection circuit is energized, the output voltage signal U0 of the output terminal of the weighing device is set, and U0 is compared with the preset voltage at the positive input terminal of the first comparator OA1 and with the preset voltage at the negative input terminal of the second comparator OA 2; setting the input voltage of the positive phase input end of the first comparator OA1 as a voltage value U1 corresponding to the maximum value of the product in the qualified quality range, and setting the input forging voltage of the negative phase input end of the second comparator OA2 as a voltage value U2 corresponding to the minimum value of the product in the qualified quality range; when U2< U0< U1, the output end of the first comparator OA1 and the output end of the second comparator OA2 both output high level, and the quality of the product is in a qualified range; in other cases, one of the outputs of the first comparator OA1 and the output of the second comparator OA2 must be low.

Preferably, the judging circuit includes a first and gate and a second not gate, two input terminals of the first and gate are electrically connected to an output terminal of the first comparator OA1 and an output terminal of the second comparator OA2, respectively, an output terminal of the first and gate is electrically connected to an anode of a first electromagnetic valve K1, a cathode of the first electromagnetic valve K1 is grounded, the first electromagnetic valve K1 is a switch of the second driving member, an output terminal of the first and gate is electrically connected to an input terminal of the second not gate, an output terminal of the second not gate is electrically connected to an anode of the second electromagnetic valve K2, a cathode of the second electromagnetic valve K2 is grounded, and the second electromagnetic valve K2 is a switch of the third driving member.

By adopting the technical scheme, when the input ends of the first NAND gates are all 1, the output end of the first NAND gate is 1, otherwise, the output end of the first NAND gate is 0, namely, when the product quality is in a qualified range, the first NAND gate outputs 1, otherwise, the output end of the first NAND gate is 0; when the output end of the first nand gate is 1, the first electromagnetic valve K1 is closed, the second driving piece acts, namely, contracts, the second electromagnetic valve K2 is not closed due to the existence of the reverser, the third driving piece does not act, the contraction state is kept, and at the moment, the screening platform inclines towards one side where the driving assembly is located, so that the product falls into the receiving device; when first NAND gate output is 0, first solenoid valve K1 is not closed, and second solenoid valve K2 is closed, and the second driving piece keeps the extension state this moment, and the third driving piece is in the extension state, and screening platform inclines towards the other end this moment, and the product falls into in another receiving device, consequently when the quality of product is in qualified range, the product falls into in the receiving device who is close to drive assembly one end, otherwise falls into in the receiving device of the other end.

In summary, the present application includes at least one of the following beneficial technical effects:

1.1. the product is transferred to the weighing device from the last production node to be weighed, the weighing device displays the quality data of the product, different control interfaces are controlled according to the data displayed by the weighing device to regulate and control the rotation of the first driving part, and when the quality of the product meets the requirement, the corresponding control interfaces are controlled to enable the screening platform to obliquely rotate towards one of the material receiving devices, so that the qualified product is collected into the material receiving device; when the quality of the product does not meet the requirement, controlling the corresponding control interface to collect the unqualified product into another receiving device, so that the qualified product is distinguished from the unqualified product;

2. the button controls the rotation of the first driving part, so that the rotation of the screening platform is controlled, namely left inclination, reset and right inclination are respectively realized, and the screening of the product quality is realized;

3. carry out the electricity with weighing device and first driving piece and connect in MCU for MCU can judge the data that show weighing device according to setting up built-in procedure, and the rotation state of the first driving piece of control that corresponds, thereby will sieve according to the quality of product, is favorable to improving the degree of automation of system.

Drawings

FIG. 1 is a block diagram of a system according to a first embodiment;

FIG. 2 is a schematic overall structure diagram of the first embodiment;

FIG. 3 is a schematic view of the overall structure of the second embodiment, which is in a reset state;

FIG. 4 is a schematic view of the overall structure of the second embodiment, which is in a left inclined state;

FIG. 5 is a schematic view of the overall structure of the second embodiment, which is in a right-inclined state;

fig. 6 is a circuit diagram of the second embodiment.

Reference numerals: 1. a screening device; 2. a weighing device; 3. screening the platform; 4. a first driving member; 5. a material receiving device; 6. a connecting member; 7. a guide member; 8. screening the bracket; 9. a drive assembly; 91. a second driving member; 92. a third driving member; 10. a control circuit; 11. a detection circuit; 12. a judgment circuit; 13. and a limiting member.

Detailed Description

The present application is described in further detail below with reference to figures 1-6.

The embodiment of the application discloses screening system.

The first embodiment is as follows:

referring to figure 1, a screening system comprises a screening device 1 and a weighing device 2 with data display. Screening plant 1 includes screening platform 3 and the first driving piece 4 of drive screening platform 3 pivoted, and weighing device 2 sets up to the electronic scale, and first driving piece 4 sets up to step motor or servo motor, and preferred is step motor. The drive shaft of first driving piece 4 passes through connecting piece 6 to be established in one side of screening platform 3, and weighing device 2 locates the one side that screening platform 3 kept away from first driving piece 4. The first drive member 4 is electrically connected with a control interface for controlling the left tilt, reset and right tilt states of the screening deck 3, wherein the reset state is that the screening deck 3 is horizontal. The two inclined ends of the screening platform 3 are respectively provided with a material receiving device 5. The material receiving device 5 can also be set as a conveyor belt, and the screened product is conveyed to the next node to be packaged.

Wherein, the connecting piece 6 is integrally in an inverted V shape and forms a closed triangular structure with the screening platform 3. The connecting piece 6 that is the type of falling V not only is favorable to prolonging the arm of force between drive shaft and the screening platform 3 on the first driving piece 4 to reduce the turned angle of first driving piece 4 when the slope, in order to improve the efficiency of product screening. And the connecting piece 6 in the form of an inverted V contributes to increasing the stability of the connection between the screening deck 3 and the drive shaft of the first driving member 4.

The whole screening platform 3 is cuboid, and the guide pieces 7 protruding out of the surface of the screening platform 3 are arranged on two sides of the screening platform in the length direction, so that when the screening platform 3 is inclined, a product cannot easily slide out of the side edges of the screening platform 3. Or the screening platform 3 is provided with a chute which is concave in an arc shape, and the concave direction of the arc shape is close to one side where the first driving piece 4 is located. In addition, the two inclined ends of the screening platform 3 are also provided with limiting parts 13 to limit the maximum rotating angle of the screening platform 3, so that the screening platform 3 is protected.

The control mode to control interface has two kinds, and under one kind condition, control interface is controlled to be connected with the button, and the button corresponds left slope, reset and the right slope of control screening platform 3 to the realization is to the screening of product quality. And the button can be manually and remotely controlled or the switch of the button can be controlled by an external button control device, such as an air cylinder and the like.

Referring to fig. 2, in another case, the weighing device 2 and the first driving member 4 are electrically connected to an MCU, and the control interface is electrically connected to the MCU. The first driving member 4 is provided with three working modes, which correspond to the left inclination, the reset and the right inclination of the screening platform 3, respectively. Carry out the electricity with weighing device 2 and first driving piece 4 and connect in MCU for MCU can judge the data that show weighing device 2 according to the procedure of inside write in, and the output corresponds PWM ripples in order to control the rotation state of first driving piece 4, thereby will sieve according to the quality of product, is favorable to improving the screening efficiency of product.

The implementation principle of the first embodiment is as follows: the weighing device 2 weighs the mass of the product and displays mass data, and the mass data weighed by the weighing device 2 controls different control interfaces so as to control the left inclination, the reset and the right inclination of the screening platform 3, so that the products with different masses can be classified; when the quality of the product meets the requirement, controlling the corresponding control interface to enable the screening platform 3 to rotate towards one of the material receiving devices 5 in an inclined mode, and accordingly enabling the qualified product to be collected into the material receiving device 5; when the quality of the product does not meet the requirement, the corresponding control interface is controlled, so that the unqualified product is collected into another material receiving device 5, and the qualified product is distinguished from the unqualified product.

Example two:

referring to figure 3, a screening system comprises a screening device 1 and a weighing device 2. Screening device 1 includes screening support 8, rotates the screening platform 3 of connecting on screening support 8 and is used for driving the inclined pivoted drive assembly 9 of screening platform 3. Drive assembly 9 locates the one end of screening platform 3, and weighing device 2 locates the side that screening platform 3 received the product of waiting to detect, and the both ends of screening platform 3 slope are equipped with receiving device 5 respectively. The drive assembly 9 and the weighing device 2 are electrically connected with a control circuit 10 for controlling the left tilt, the reset and the right tilt of the screening platform 3 in dependence of the mass signal of the weighing device 2.

Referring to fig. 4 and 5, the driving assembly 9 includes a second driving member 91 and a third driving member 92, and the second driving member 91 and the third driving member 92 are provided as air cylinders. One end of the second driving member 91 is rotatably connected to the screening bracket 8, the end of the driving shaft of the second driving member 91 is fixedly connected to one end of the third driving member 92, the end of the driving shaft of the third driving member 92 is rotatably connected to the screening platform 3, the initial state of the second driving member 91 is an extended state, the initial state of the third driving member 92 is a contracted state, and the initial state of the screening platform 3 is a horizontal state. When the second driving member 91 and the third driving member 92 are not operated, the second driving member 91 is kept in the extended state and the third driving member 92 is kept in the contracted state. When the second driving element 91 is activated and the third driving element 92 is deactivated, the second driving element 91 is retracted and the third driving element 92 holds the retracted state, i.e. the screening deck 3 is tilted towards one end. When the second driving member 91 is not operated and the third driving member 92 is operated, the second driving member 91 is kept in the extended state and the third driving member 92 is in the extended state, at which time the screening deck 3 is tilted towards the other end.

Referring to fig. 6, the control circuit 10 includes a detection circuit 11 for detecting a product quality range and a judgment circuit 12 for controlling the operation of the driving assembly 9, which are electrically connected. The detection circuit 11 is used for detecting the product quality range and sending the detection result to the judgment circuit 12, and the judgment circuit 12 is used for controlling the action of the driving component 9 according to the detection result of the detection circuit 11.

The detection circuit 11 comprises a first comparator OA1 and a second comparator OA2, the first comparator OA1 and the second comparator OA2 being operational amplifiers. The non-inverting input terminal of the first comparator OA1 is electrically connected to one end of the switch S1, the other end of the switch S1 is electrically connected to one end of the resistor R1, and the other end of the resistor R1 is electrically connected to the DC power supply DC. One end of the switch S1, which is far from the first comparator OA1, is electrically connected to one end of a resistor R2, and the other end of the resistor R2 is grounded. The switch S1 is used to determine whether there is a product on the weighing apparatus 2 and located on the surface of the weighing apparatus 2, the negative input terminal of the first comparator OA1 is electrically connected to the output terminal of the weighing apparatus 2, and the output terminal of the weighing apparatus 2 is used to output the voltage value corresponding to the mass of the product weighed by the weighing apparatus 2. The output of the weighing device 2 is electrically connected to the positive input of a second comparator OA2, the negative input of the second comparator OA2 is electrically connected to one end of a resistor R3, and the other end of the resistor R3 is electrically connected to a direct current power supply DC. The negative phase input terminal of the second comparator OA2 is electrically connected to one end of the resistor R4, and the other end of the resistor R4 is grounded.

The judgment circuit 12 comprises a first and gate and a second not gate, two input ends of the first and gate are electrically connected to an output end of the first comparator OA1 and an output end of the second comparator OA2 respectively, an output end of the first and gate is electrically connected to an anode of the first electromagnetic valve K1, a cathode of the first electromagnetic valve K1 is grounded, the first electromagnetic valve K1 is a switch of the second driving member 91, an output end of the first and gate is electrically connected to an input end of the second not gate, an output end of the second not gate is electrically connected to an anode of the second electromagnetic valve K2, a cathode of the second electromagnetic valve K2 is grounded, and the second electromagnetic valve K2 is a switch of the third driving member 92.

The implementation principle of the second embodiment is as follows: the product falls and weighs on weighing device 2, and control circuit 10 controls the action of drive assembly 9 according to the mass signal of the product of weighing on weighing device 2 to left side slope and the right-hand member slope of control screening platform 3 make the product fall respectively in the receiving device 5 at screening platform 3 both ends, thereby realize screening the different quality of product, and after the screening was accomplished, control circuit 10 controlled the reset of screening platform 3. Specifically, when no product is on the weighing device 2, the switch S1 is turned on, the detection circuit 11 is not powered, the driving assembly 9 is not operated, and the screening platform 3 is in a horizontal state. When a product falls on the weighing device 2, the switch S1 is closed, the detection circuit 11 is energized, the output voltage signal U0 at the output of the weighing device 2 is set, and U0 is compared with the preset voltage at the positive input of the first comparator OA1 and with the preset voltage at the negative input of the second comparator OA 2; the input voltage at the positive phase input terminal of the first comparator OA1 is set to the voltage value U1 corresponding to the maximum value of the product within the acceptable quality range, and the input voltage at the negative phase input terminal of the second comparator OA2 is set to the voltage value U2 corresponding to the minimum value of the product within the acceptable quality range. When U2< U0< U1, the output terminal of the first comparator OA1 and the output terminal of the second comparator OA2 both output a high level 1, and the quality of the product is within a qualified range at this time. In other cases, one of the outputs of the first comparator OA1 and the output of the second comparator OA2 must be low 0. When the input ends of the first nand gate are all 1, the output end of the first nand gate is 1, otherwise, the output end of the first nand gate is 0, at this time, the first electromagnetic valve K1 is closed, the second driving member 91 acts, namely, contracts, the second electromagnetic valve K2 does not close due to the existence of the reverser, the third driving member 92 does not act, and the contraction state is maintained. The screening deck 3 is now tilted towards the side on which the drive assembly 9 sits so that the product falls into the receiving device 5. When the output of the first nand gate is 0, the first solenoid valve K1 is not closed, the second solenoid valve K2 is closed, and the second driving element 91 is kept in the extended state and the third driving element 92 is in the extended state. At this time, the screening platform 3 is inclined towards the other end, and the product falls into the other receiving device 5. Therefore, when the quality of the product is in a qualified range, the product falls into the material receiving device 5 close to one end of the driving assembly 9, otherwise, the product falls into the material receiving device 5 at the other end.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims

1. A screening system, characterized by: including screening plant (1) and weighing device (2) that have data display, screening plant (1) is including screening platform (3) and drive screening platform (3) pivoted first driving piece (4), the drive shaft of first driving piece (4) passes through connecting piece (6) fixed connection and is in one side of screening platform (3), weighing device (2) are located screening platform (3) are kept away from one side of first driving piece (4), first driving piece (4) electricity is connected with and is used for control the control interface of left side slope, the reset and the right side slope state of screening platform (3), and the reset state does screening platform (3) level.

2. A screening system according to claim 1, wherein: the weighing device (2) is arranged as an electronic scale.

3. A screening system according to claim 2, wherein: the control interface is controlled to be connected with buttons which respectively control the left inclination, the reset and the right inclination of the screening platform (3) correspondingly.

4. A screening system according to claim 2, wherein: the weighing device (2) and the first driving piece (4) are electrically connected with an MCU, the control interface is electrically connected with the MCU, the first driving piece (4) is a stepping motor, and the stepping motor is provided with three working modes and respectively corresponds to the left inclination, the reset and the right inclination of the screening platform (3).

5. A screening system according to claim 1, wherein: and material receiving devices (5) are correspondingly arranged at two inclined ends of the screening platform (3) respectively.

6. A screening system, characterized by: the device comprises a screening device (1) and a weighing device (2), wherein the screening device (1) comprises a screening support (8), a screening platform (3) rotationally connected to the screening support (8) and a driving assembly (9) used for driving the screening platform (3) to rotate in an inclined manner, the driving assembly (9) is arranged at one end of the screening platform (3), the weighing device (2) is arranged at one side face of the screening platform (3) for receiving a product to be detected, and material receiving devices (5) are respectively arranged at two inclined ends of the screening platform (3); the drive assembly (9) and the weighing device (2) are electrically connected with a control circuit (10) for controlling the left tilt, the reset and the right tilt of the screening platform (3) according to the mass signal of the weighing device (2).

7. A screening system according to claim 6, wherein: drive assembly (9) includes second driving piece (91) and third driving piece (92), the one end of second driving piece (91) is rotated and is connected on screening support (8), the drive shaft end fixed connection of second driving piece (91) is in the one end of third driving piece (92), the drive shaft end of third driving piece (92) is rotated and is connected on screening platform (3), the initial condition of second driving piece (91) is extension state, the initial condition of third driving piece (92) is the shrink state, the initial condition of screening platform (3) is the horizontal condition.

8. A screening system according to claim 7, wherein: the control circuit (10) comprises a detection circuit (11) for detecting the quality range of the product and a judgment circuit (12) for controlling the action of the driving component (9).

9. A screening system according to claim 8, wherein: the detection circuit (11) comprises a first comparator OA1 and a second comparator OA2, wherein the non-inverting input end of the first comparator OA1 is electrically connected with one end of a switch S1, the other end of the switch S1 is electrically connected with one end of a resistor R1, the other end of the resistor R1 is electrically connected with a direct current power supply DC, one end of the switch S1 far away from the first comparator OA1 is electrically connected with one end of a resistor R2, and the other end of the resistor R2 is grounded; the switch S1 is used for judging whether a product falls on the weighing device (2) and is positioned on the surface of the weighing device (2), the negative phase input end of the first comparator OA1 is electrically connected to the output end of the weighing device (2), the output end of the weighing device (2) is electrically connected to the positive phase input end of the second comparator OA2, the negative phase input end of the second comparator OA2 is electrically connected with one end of a resistor R3, the other end of the resistor R3 is electrically connected with a direct current power supply DC, the negative phase input end of the second comparator OA2 is electrically connected with one end of a resistor R4, and the other end of the resistor R4 is grounded.

10. A screening system according to claim 9, wherein: the judging circuit (12) comprises a first AND gate and a second NOT gate, two input ends of the first AND gate are electrically connected to an output end of the first comparator OA1 and an output end of the second comparator OA2 respectively, an output end of the first AND gate is electrically connected with an anode of a first electromagnetic valve K1, a cathode of the first electromagnetic valve K1 is grounded, the first electromagnetic valve K1 is a switch of the second driving piece (91), an output end of the first AND gate is electrically connected to an input end of the second NOT gate, an output end of the second NOT gate is electrically connected to an anode of a second electromagnetic valve K2, a large cathode of the second electromagnetic valve K2 is grounded, and the second electromagnetic valve K2 is a switch of the third driving piece (92).