Electronic powder spraying device and control method for a web-fed offset press

Abstract

The application discloses a kind of electronic powder spraying devices and control methods of web self-adaptive offset press, belong to printing equipment technical field.The device includes powder spraying device, paper web detection sensor, electrostatic generator and control unit.One row of powder spraying head of powder spraying device is divided into middle powder spraying head and side powder spraying head, paper web detection sensor detects paper web size in real time, and control unit selectively closes part of side powder spraying head according to detection result by driving switch valve shaft, so that powder spraying web and printing web are automatically synchronized.At the same time, negative ion generator makes ink or paper with negative charge, positive ion generator makes powder sprayed with positive charge, and the principle of opposite charges is used to significantly improve the adsorption of powder on ink pattern and the adhesion of powder.The application solves the problem of manual adjustment of traditional powder spraying device and easy spatter of powder, realizes automatic adaptation of powder spraying web and efficient adsorption of powder.

Description

Technical Field

[0001] This invention relates to printing presses, and more specifically to an electronic powder spraying device and control method for a width-adaptive offset printing press. Background Technology

[0002] In offset printing, to prevent back-side smudging before the ink dries, an anti-smudging powder is usually sprayed onto the surface of the printed material. Traditional powder spraying devices mainly have the following two problems:

[0003] First, the powder spraying system is independently controlled and cannot communicate with the printing host. When the printing area or ink zone is adjusted, the powder spraying area cannot automatically adjust accordingly and still needs to be manually adjusted by the operator through the powder spraying control cabinet. Due to the possibility of negligence in manual intervention, adjustments may be forgotten. If the powder spraying area is larger than the printing area, it will lead to a large amount of powder waste and fill the workshop air with dust, seriously reducing the quality of the printing environment; if the powder spraying area is smaller than the printing area, powder cannot be sprayed on both sides of the printed product, which can easily cause quality defects such as edge smudging.

[0004] Secondly, the powder adhesion is poor. In existing technologies, the powder mainly relies on the spraying speed and its own gravity to naturally scatter onto the surface of the printed material, resulting in weak bonding with the ink and slow adsorption. This not only leads to some powder splattering and loss, causing material waste and environmental pollution, but also easily results in poor powder adsorption, ultimately affecting the quality of the printed product.

[0005] Therefore, developing an electronic powder spraying device that can automatically adapt to changes in printing width and significantly improve the adhesion of powder and ink through electrostatic action has become a technical problem that the printing industry urgently needs to solve. Summary of the Invention

[0006] This invention provides an electronic powder spraying device for a format-adaptive offset printing machine. The offset printing machine includes an ink transfer device and a roller. Ink with a pattern on it is transferred from the ink transfer device to the roller and then from the roller to the paper. The electronic powder spraying device for the adaptive offset printing machine includes:

[0007] The powder spraying device includes a row of powder spraying heads for spraying powder onto the surface of paper. The row of powder spraying heads includes a central powder spraying head and side powder spraying heads located on both sides of the central powder spraying head in the paper width direction.

[0008] Paper size detection sensor, used to detect the size of printing paper;

[0009] An electrostatic generator, connected to a control unit, includes a negative ion generator and a positive ion generator. The negative ion generator emits negative ions towards the roller and / or paper, causing the ink particles to carry a negative charge and / or the paper to carry a negative charge. The positive ion generator emits positive ions towards the powder outlet of a row of powder spraying heads, causing the sprayed powder to carry a positive charge. The powder is adsorbed onto the paper or the ink pattern on the paper by utilizing the principle of attraction between opposite charges.

[0010] The control unit is connected to the powder spraying device, the paper width detection sensor, and the electrostatic generator. The control unit controls whether the side powder spraying head sprays powder according to the paper width detection sensor to keep the powder spraying width synchronized with the printing width, and controls the operation of the electrostatic generator.

[0011] Furthermore, the powder spraying device also includes a powder supply device for conveying powder to the powder spraying device. The powder supply device includes a powder spraying tank, a stirring motor, a quantitative powder dispensing mechanism, a pressure powder spraying mechanism, and a powder spraying base.

[0012] The powder spraying tank contains powder and is equipped with a stirring shaft.

[0013] The stirring motor is connected to the stirring shaft inside the powder spraying tank, and is used to drive the stirring shaft to rotate and stir the powder;

[0014] The quantitative powder dispensing mechanism is connected to the powder outlet at the bottom of the powder spraying tank and is used to quantitatively convey powder to the pressure powder spraying mechanism;

[0015] The pressure powder spraying mechanism delivers powder to the powder spraying station at a constant pressure;

[0016] The powder spraying base has a first cavity and a second cavity inside. Both the first cavity and the second cavity are connected to the pressure powder spraying mechanism. The bottom outlet of the first cavity is connected to a number of first powder outlets, and the bottom outlet of the second cavity is connected to a number of second powder outlets. The first powder outlets and the second powder outlets are respectively connected to the middle powder spraying head and the side powder spraying head through pipes.

[0017] The switching valve shaft is rotatably disposed inside the powder spraying base. A through hole is provided on the switching valve shaft corresponding to the position of the second cavity. The switching valve shaft has a conducting position and a blocking position. When it is in the conducting position, the through hole is connected to the second cavity, and the second powder outlet normally conveys powder to the side powder spraying head. When rotated to the blocking position, the through hole is misaligned with the second cavity, and the second powder outlet stops conveying powder to the side powder spraying head.

[0018] The drive mechanism is mechanically connected to the switching valve shaft and communicatively connected to the control unit. The drive mechanism receives signals from the control unit and switches the on and off states of the switching valve shaft.

[0019] Furthermore, the drive mechanism includes a drive motor and a gear transmission mechanism. The drive motor is communicatively connected to the control unit and is connected to the switching valve shaft via the gear transmission mechanism, driving the switching valve shaft to rotate; or

[0020] The drive mechanism includes a cylinder and a connecting rod. The cylinder is communicatively connected to the control unit. The two ends of the connecting rod are rotatably connected to the piston rod of the cylinder and the switching valve shaft. The forward and backward movement of the cylinder drives the switching valve shaft to rotate through the connecting rod.

[0021] Furthermore, the rotation angle of the switch valve shaft is 90°, and the 90° rotation enables the through hole to be fully connected or completely blocked from the second cavity.

[0022] Furthermore, a row of powder spraying heads is arranged at equal intervals along the width of the paper, with the middle powder spraying head corresponding to the central area of ​​the printing area, and at least two sets of side powder spraying heads. The control unit selectively closes some of the side powder spraying heads by controlling the rotation position of the switch valve shaft, thereby realizing the segmented adjustment of the powder spraying area.

[0023] Furthermore, it also includes a sealing structure disposed on the contact surface between the switch valve shaft and the powder spraying seat to prevent powder from leaking from the shaft gap. The sealing structure includes a sealing groove disposed on the inner side of the switch valve shaft and a sealing ring installed in the sealing groove.

[0024] Furthermore, the paper size detection sensor is one or more combinations of photoelectric edge detection sensors, ultrasonic edge sensors, laser distance sensors, contact sensors, and CCD machine vision sensors.

[0025] Furthermore, the negative ion generator is located near the roller, the positive ion generator is located near the powder outlet of the powder spraying device, and the electrostatic generator is electrically connected to the control unit, which controls its start / stop or working intensity.

[0026] A powder spraying control method based on the above-mentioned adaptive offset printing machine electronic powder spraying device, the control method comprising:

[0027] Printing area adaptive adjustment:

[0028] The paper size detection sensor detects the paper size in real time and sends the detection signal to the control unit.

[0029] The control unit determines which side powder spraying heads need to be turned on or off based on the detected paper size, so that the powder spraying width is synchronized with the printing width.

[0030] Electrostatic charging and powder adsorption:

[0031] During the ink transfer process, the negative ion generator is controlled to emit negative ions towards the roller and / or paper, so that the ink particles and / or the ink pattern on the paper are negatively charged.

[0032] During the powder spraying process, the positive ion generator is controlled to emit positive ions at the powder outlet of the powder spraying head, so that the sprayed powder is positively charged.

[0033] Utilizing the principle of attraction between opposite charges between ink patterns and powder, powder is adsorbed onto paper or ink patterns on paper.

[0034] The advantages of the adaptive offset printing machine electronic powder spraying device and control method of the present invention are summarized as follows:

[0035] 1) This invention uses a paper size detection sensor to detect the size of the printing paper in real time. The control unit automatically drives the switching valve shaft to rotate according to the detection results, selectively closing some side powder spraying heads, so that the powder spraying width is kept synchronized with the printing width in real time. This solves the problem that traditional powder spraying devices require manual adjustment and are prone to adjustment negligence.

[0036] 2) This invention uses a negative ion generator to emit negative ions at the roller and / or paper, so that the ink particles or paper are negatively charged. At the same time, a positive ion generator is used to emit positive ions at the powder outlet of the powder spraying head, so that the sprayed powder is positively charged. Through the principle of attraction between opposite charges, the adsorption force and adhesion of the powder on the ink pattern are significantly improved.

[0037] 3) The present invention provides an independent first cavity and a second cavity in the powder spraying base. The middle powder spraying head is fixed and supplied with powder by the first cavity, and the side powder spraying head is controlled by the second cavity through the switch valve shaft to achieve completely independent control of the middle and side powder spraying, avoid mutual interference, and ensure stable and reliable powder supply.

[0038] 4) This invention is equipped with a quantitative powder dispensing mechanism and a pressure powder spraying mechanism, which can accurately control the powder delivery amount and spraying pressure, and adjust the powder spraying amount in real time according to the printing speed, so as to meet the needs of different working conditions and avoid uneven powder output or powder interruption.

[0039] 5) This invention supports multiple detection methods such as photoelectric edge detection sensors, ultrasonic edge sensors, laser distance sensors or CCD machine vision sensors to detect the size of the paper. The method can be flexibly selected according to the workshop environment to ensure accurate and reliable paper size detection.

[0040] 6) The control unit of this invention can be linked with the offset printing machine host for control. When the offset printing machine starts or stops, the powder spraying device automatically starts and stops synchronously. At the same time, through the delayed shutdown function of the electrostatic generator, it is ensured that the residual powder can also be fully adsorbed, realizing highly intelligent unmanned operation. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 As shown in one embodiment, the present invention employs a linkage mechanism to drive the switching valve shaft of a powder supply device.

[0043] Figure 2 This is a structural diagram of the switching valve shaft;

[0044] Figure 3 In another embodiment, the present invention employs a gear mechanism to drive the switching valve shaft of the powder supply device.

[0045] Figure 4 This is a structural diagram of the powder spraying base and its first and second powder outlet nozzles at the bottom.

[0046] Figure 5 for Figure 4 A stereoscopic view viewed from below;

[0047] Figure 6 This is a schematic diagram of the powder spraying process for wide-format paper.

[0048] Figure 7 This is a schematic diagram of the powder spraying process for medium-sized paper.

[0049] Figure 8 A schematic diagram of powder spraying operation for narrow-format paper;

[0050] Figure 9 This is a control principle diagram of the control unit of the present invention;

[0051] Figure 10 A schematic diagram showing the negative ion generator spraying negative ions onto the roller;

[0052] Figure 11 A schematic diagram showing the positive ion generator spraying positive ions into the central powder spray head and the side powder spray heads (not shown);

[0053] Figure 12 This is a schematic diagram illustrating the principle of enhancing powder adsorption through electrostatics.

[0054] Explanation of reference numerals in the attached figures:

[0055] Explanation of reference numerals in the attached figures:

[0056] 1-Roller;

[0057] 110 - Powder spray head assembly; 111 - Center powder spray head; 112 - Side powder spray head;

[0058] 120-Powder supply device; 121-Powder spraying barrel; 122-Stirring motor; 123-Quantitative powder dispensing mechanism; 123-1-Feeding motor; 124-Pressure powder spraying mechanism; 125-Powder spraying base; 125-1-First powder outlet; 125-2-Second powder outlet; 125-3-Driving gear; 125-4-Driven gear; 125-5-Drive motor; 125-6-Second cavity; 126-Switch valve shaft; 126-1-Through hole; 126-2-Sealing groove; 127-Drive mechanism; 127-1-Cylinder; 127-2-Connecting rod;

[0059] 200-Paper width detection sensor;

[0060] 300 - Static electricity generator; 310 - Negative ion generator; 320 - Positive ion generator;

[0061] 400 - Control Unit. Detailed Implementation

[0062] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0063] To fully understand this invention, detailed steps and structures will be presented in the following description to illustrate the technical solution of this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0064] The adaptive offset printing machine electronic powder spraying device of the present invention is compatible with various offset printing machines. The basic structure of the offset printing machine includes an ink transfer device and a roller 1. The ink transfer device transfers ink with a printing pattern to the surface of the roller 1, and then the roller 1 transfers the ink pattern to the conveyed paper under the pressure of the printing press. The powder spraying device is set on the paper output side of the offset printing machine roller 1. After the ink transfer is completed, the paper surface is treated with powder spraying to achieve the anti-sticking effect.

[0065] The paper width adaptive offset printing machine electronic powder spraying device of the present invention mainly consists of four core parts: a powder spraying device, a paper width detection sensor 200, an electrostatic generator 300, and a control unit 400. The structure, installation method, and working principle of each part are described in detail below:

[0066] I. Structure and Operation of the Powder Spraying Device

[0067] The powder spraying device includes a powder spraying head assembly 110 and a powder supply device 120. The powder supply device 120 provides powder to the powder spraying head assembly 110, and the powder spraying head assembly 110 completes the final paper powder spraying operation.

[0068] (a) Powder spray head assembly 110

[0069] The powder spraying head assembly 110 consists of a row of powder spraying heads arranged at equal intervals along the width of the paper, forming a linear distribution. The assembly includes a central powder spraying head 111 and several sets of side powder spraying heads 112. The central powder spraying head 111 corresponds to the fixed central area of ​​the printing area and is in a constant spraying state, not starting or stopping with changes in the paper size. The side powder spraying heads 112 are symmetrically arranged on the left and right sides of the central powder spraying head 111. Each set of side powder spraying heads 112 corresponds to a section of the printing area adjustment area, and there are at least two sets (which can be added according to the maximum printing area requirement of the offset printing machine, such as two sets, four sets, etc.). The control unit 400 controls the start and stop of one or more sets to achieve segmented and precise adjustment of the powder spraying area.

[0070] All powder nozzles face the paper feed surface and are narrowed to ensure concentrated powder spraying. The vertical distance between the powder nozzle and the paper surface can be adjusted according to the offset printing machine model to avoid paper scratching due to excessive distance or powder splashing due to excessive distance.

[0071] (ii) Powder supply device 120

[0072] like Figure 1 The powder supply device 120 integrates functions such as powder storage, stirring, quantitative powder dispensing, pressure conveying, and on / off control. It includes a powder spraying tank 121, a stirring motor 122, a quantitative powder dispensing mechanism 123, a pressure powder spraying mechanism 124, a powder spraying base 125, a switch valve shaft 126, a drive mechanism 127, and a sealing structure. Specific implementation details are as follows:

[0073] 1. Powder spraying tank 121 and stirring motor 122: The powder spraying tank 121 stores anti-sticking powder for offset printing. A stirring shaft is vertically installed inside the powder spraying tank 121, and a spiral stirring blade is provided on the stirring shaft. The stirring motor 122 is installed on one side of the powder spraying tank 121, and its output shaft is connected to the stirring shaft. The stirring motor 122 continuously drives the stirring shaft to rotate, stirring the powder in the tank to prevent the powder from getting damp and clumping, and to ensure the flowability of the powder. The stirring motor 122 is electrically connected to the control unit 400 and starts and stops with the powder spraying device as a whole, or it can be manually controlled independently.

[0074] 2. Quantitative powder dispensing mechanism 123: The quantitative powder dispensing mechanism 123 is installed at the powder outlet at the bottom of the powder spraying tank 121. It adopts a spiral feeding structure, including a feeding screw and a feeding motor 123-1. The feeding screw extends into the conical bottom of the powder spraying tank 121. The feeding motor drives the feeding screw to rotate. The amount of powder dispensed per unit time is precisely controlled by the screw pitch. The amount of powder dispensed can be adjusted by the control unit 400 to adjust the speed of the feeding motor, so as to meet the powder spraying requirements of different printing speeds and different ink volumes. The discharge end of the quantitative powder dispensing mechanism 123 is connected to the pressure powder spraying mechanism 124 to realize continuous quantitative powder delivery.

[0075] 3. Pressure powder spraying mechanism 124: The pressure powder spraying mechanism 124 is a pneumatic pressure conveying structure, including an external air pump (not shown in the figure), air pipe, and powder mixing chamber. The micro air pump provides compressed air at a constant pressure and delivers the high-pressure air to the powder mixing chamber through the air pipe. The powder mixing chamber is connected to the discharge end of the quantitative powder dispensing mechanism 123. The powder is fully mixed with the compressed air in the powder mixing chamber to form an air-powder mixed flow, which is then conveyed to the powder spraying base 125 through the discharge pipe of the pressure powder spraying mechanism 124. The compressed air provides power for powder conveying, ensuring that the powder can be stably conveyed to each powder spraying head, and the discharge pressure is constant, avoiding uneven powder dispensing and powder interruption.

[0076] 4. Powder spraying base 125: The powder spraying base 125 is hollow inside, with a first cavity and a second cavity 125-6 inside. Both cavities are connected to the discharge pipe of the pressure powder spraying mechanism 124 to realize the diversion of the air-powder mixed flow.

[0077] like Figure 4-5 As shown, a plurality of first powder outlet nozzles 125-1 are opened at the bottom of the first cavity. The first powder outlet nozzles 125-1 are connected one-to-one with the middle powder spraying head 111 through flexible powder conveying pipes to supply powder to the middle powder spraying head 111. A plurality of second powder outlet nozzles 125-2 are opened at the bottom of the second cavity 125-6. The second powder outlet nozzles 125-2 are also connected one-to-one with the side powder spraying head 112 through flexible powder conveying pipes to supply powder to the side powder spraying head 112. The independent design of the two cavities ensures that the powder supply of the middle powder spraying head and the side powder spraying head does not interfere with each other.

[0078] 5. Switch valve shaft 126 and drive mechanism 127: The switch valve shaft 126 is a metal round shaft that rotatably passes through the powder spraying seat 125. A through hole 126-1 matching the inner diameter of the second cavity is opened on the switch valve shaft 126 at the position corresponding to the second cavity. The through hole 126-1 is a through structure to ensure the smooth passage of the gas-powder mixture. The switch valve shaft 126 has two working states: a conducting position and a blocking position. When it is in the conducting position, the through hole 126-1 is completely aligned with the second cavity, and the gas-powder mixture can smoothly pass through the through hole 126-1 into the second powder outlet 125-2, and the side powder spraying head 112 sprays powder normally. When the switch valve shaft 126 rotates to the blocking position, the through hole 126-1 is misaligned with the second cavity, and the solid part of the switch valve shaft 126 blocks the second cavity, preventing the gas-powder mixture from passing through, and the side powder spraying head 112 stops spraying powder.

[0079] The drive mechanism 127 is mechanically connected to the end of the switching valve shaft 126 and communicatively connected to the control unit 400. It receives electrical signals from the control unit 400 and drives the switching valve shaft 126 to rotate, thereby switching the on / off state of the second powder nozzle 125-2. This invention provides two implementations of the drive mechanism 127, which can be selected according to the installation space and control requirements of the offset printing machine:

[0080] Implementation method one: such as Figure 1-2 As shown, the drive mechanism 127 includes a cylinder 127-1 and a connecting rod 127-2. The cylinder 127-1 is a pneumatic telescopic cylinder connected to the compressed air source of the offset printing machine. The telescopic movement of its piston rod is controlled by the control unit 400 through an electromagnetic reversing valve. One end of the connecting rod 127-2 is hinged to the end of the piston rod of the cylinder 127-1, and the other end is eccentrically hinged to the end of the switching valve shaft 126. The linear telescopic movement of the cylinder 127-1 is converted into the rotational movement of the switching valve shaft 126 through the connecting rod 127-2, thereby realizing the state switching.

[0081] Implementation Method Two: (e.g.) Figure 3 As shown, the drive mechanism 127 includes a drive motor 125-5 and a gear transmission mechanism. The drive motor 125-5 is a stepper motor and is communicatively connected to the control unit 400. The gear transmission mechanism includes a driving gear 125-3 and a driven gear 125-4 that mesh with each other. The driving gear 125-3 is mounted on the output shaft of the drive motor, and the driven gear 125-4 is mounted on the end of the switch valve shaft 126. The drive motor 125-5 receives pulse signals from the control unit 400 and drives the switch valve shaft 126 to rotate through the gear transmission mechanism.

[0082] In this embodiment, the rotation angle of the switch valve shaft 126 is fixed at 90°. By rotating 90°, the through hole 126-1 and the second cavity 125-6 can be fully connected or completely blocked, avoiding the problem of uneven powder output caused by the semi-conductive state. The control unit 400 can control the rotation position of the switch valve shaft 126 according to the paper size, selectively closing some side powder spraying heads 112, and realizing segmented adjustment of the powder spraying area.

[0083] 6. Sealing Structure: Since the powder spraying seat 125 contains a pressurized air-powder mixture, a sealing structure is provided on the contact surface between the two to prevent powder leakage from the mating gap between the switch valve shaft 126 and the powder spraying seat 125. This structure includes an annular sealing groove 126-2 opened on the outer wall of the switch valve shaft 126. A wear-resistant and powder corrosion-resistant rubber sealing ring (such as a fluororubber sealing ring) is installed in the sealing groove. The outer diameter of the sealing ring is slightly larger than the inner diameter of the shaft hole of the powder spraying seat 125 to achieve an interference fit and effectively prevent powder leakage from the gap.

[0084] II. Selection and Installation of Paper Width Detection Sensor 200

[0085] The paper width detection sensor 200 is used to detect the width of the printing paper in real time, providing a width detection signal to the control unit 400. The paper width detection sensor 200 can be one or a combination of photoelectric edge detection sensors, ultrasonic edge sensors, laser distance sensors, and CCD machine vision sensors. The selection can be based on the printing workshop environment (such as dust, light) and detection accuracy requirements. The specific implementation and installation methods for each sensor are as follows:

[0086] (a) Photoelectric edge detection sensor, installed on the horizontal scanning bracket on both sides or above the paper conveying path at the paper feed end or paper output end of the printing press. Its detection principle is: the emitter (LED or laser) emits a light beam to illuminate the edge of the paper, and the receiver (photodiode or CCD) detects the change in light intensity caused by the paper edge blocking or reflecting the light, calculates the position difference between the two edges of the paper, and thus obtains the width of the paper.

[0087] (b) Ultrasonic edge sensor, installed on both sides of the paper conveying path at the paper feed end or paper output end of the printing press, forming a fork-type or through-beam structure. Its detection principle is: the transmitting probe emits ultrasonic pulses, the paper edge reflects or attenuates the ultrasonic waves, the receiving probe measures the echo time or intensity difference, and calculates the edge position and paper width.

[0088] (c) Laser distance sensor, installed on a fixed bracket at the paper feed end or paper output end of the printing press, adopts single-sided or double-sided measurement method. Its detection principle is: laser triangulation measurement method, the laser beam is projected onto the edge surface of the paper, the reflected light is imaged to the position sensitive detector through the lens, the distance is calculated according to the image position offset, and the paper width is obtained by the distance difference between the two sides or by transverse scanning.

[0089] (d) CCD machine vision sensor, installed above the paper at the paper feed end or paper output end of the printing press, combined with a horizontal guide rail or fixed bracket. Its detection principle is: the camera captures the image of the paper edge, performs edge extraction and pixel counting through image processing algorithm, identifies the position of the two sides of the paper edge and calculates the pixel distance, and converts it into the actual paper width.

[0090] If multiple sensors are used in combination for detection, the control unit 400 will fuse the detection signals from each sensor, remove abnormal signals, and output accurate area size data, further improving the reliability of the detection.

[0091] like Figure 6-8 As shown, when printing wide-format paper ( Figure 6 When the paper width detection sensor 200 detects that the paper width is wide, the control unit controls all switch valve shafts to be in the conducting position, and all second powder nozzles 125-2 and their corresponding side powder spraying heads 112 are opened normally, and the powder spraying area covers the entire width of the paper, achieving uniform powder spraying across the entire width.

[0092] When printing medium-sized paper ( Figure 7 The control unit drives the switch valve shaft to rotate to the middle blocking position, closing the two outer side powder spraying heads 112, leaving only the inner side powder spraying head 112 and the middle powder spraying head 111 to work together, so that the powder spraying area is accurately matched with the middle paper size, and the powder is prevented from flying outward to the edges of the paper.

[0093] When printing narrow-width paper ( Figure 8 The control unit further drives the switching valve shaft to rotate, closing all side powder spraying heads 112 and opening only the middle powder spraying head 111. The powder spraying width is completely synchronized with the narrow width, effectively preventing powder waste and dust pollution in the workshop. Through segmented control of the switching valve shaft, the device can automatically adapt to various paper widths such as wide, medium, and narrow, significantly improving the intelligence level and environmental friendliness of the powder spraying operation.

[0094] III. Arrangement and Operation of the Static Electricity Generator 300

[0095] The electrostatic generator 300 is used to infuse ink / paper and powder with opposite charges through electrostatic induction, thereby enhancing the powder's adsorption force by utilizing the principle of attraction between opposite charges. It includes a negative ion generator 310 and a positive ion generator 320, both of which are high-voltage electrostatic generating structures with adjustable output voltage. They are electrically connected to the control unit 400, which controls their start / stop and operating intensity (output voltage) to adapt to the needs of different printing speeds and powder types.

[0096] (a) Negative ion generator 310

[0097] like Figure 10 The negative ion generator 310 is installed near the offset printing machine roller 1, specifically on the paper transfer side of roller 1. Its emission port is aimed at the surface of roller 1 or the surface of paper that has just completed ink transfer. When working, the negative ion generator 310 generates and emits a high-voltage negative ion flow, which makes the surface of roller 1 and the ink particles on the surface carry a negative charge.

[0098] (II) Positive ion generator 320

[0099] like Figure 11 The positive ion generator 320 is installed on one side of the powder spraying head assembly 110 of the powder spraying device, and its emission port is aligned with the powder outlet of all powder spraying heads. Figure 11 Only the intermediate powder spraying head 111 is shown in the diagram. During operation, the positive ion generator 320 generates and emits a high-voltage positive ion stream. The positive ion stream comes into full contact with the gas-powder mixture stream ejected from the powder spraying head, causing the powder particles to carry a positive charge.

[0100] The electrostatic generator 300 operates in sync with the powder spraying device. When the powder spraying device starts, the electrostatic generator automatically turns on; when the powder spraying device stops, the electrostatic generator turns off after a 5-second delay to ensure that the powder remaining in the pipeline can also be charged.

[0101] IV. Control Implementation of Control Unit 400

[0102] The control unit 400 adopts a PLC programmable controller (a single-chip microcomputer or industrial control board can also be selected) and is installed in the electrical control cabinet of the offset printing machine. It is electrically and communicatively connected to the powder spraying device (stirring motor 122, quantitative powder dispensing mechanism 123, pressure powder spraying mechanism 124, drive mechanism 127), paper width detection sensor 200, and electrostatic generator 300 through data lines and control lines. It receives signals from each detection sensor and outputs control commands to each actuator.

[0103] The control unit 400's operation panel integrates a touch screen, start / stop buttons, speed control knob, parameter setting keys, etc. Operators can set parameters such as powder spraying volume, electrostatic voltage, and printing speed through the touch screen, and can also view the equipment's working status and fault information. At the same time, the control unit 400 has a reserved communication interface with the offset printing machine host, which can realize linkage control with the offset printing machine. That is, when the offset printing machine starts printing, the powder spraying device starts automatically; when the offset printing machine stops or stops, the powder spraying device stops synchronously, realizing unmanned operation.

[0104] The control unit 400 has a pre-stored table of correspondence between paper size and the start / stop of the side powder spray head 112. This table can be modified and saved according to actual printing needs. When the detected paper size changes, the control unit 400 will quickly switch the start / stop of the side powder spray head 112 to ensure real-time synchronization between the powder spraying area and the printing area.

[0105] V. Implementation of the Overall Device Workflow

[0106] The electronic powder spraying device for the offset printing machine with adaptive printing width of the present invention works in conjunction with the offset printing machine. The overall workflow is divided into a start-up preparation stage, a printing width adaptive adjustment stage, an electrostatic charging and powder adsorption stage, and a shutdown and finishing stage. The specific implementation steps of each stage are as follows:

[0107] (a) Start-up preparation stage

[0108] 1. Add sufficient amount of offset printing anti-sticking powder to the powder spraying tank 121, tighten the lid, and start the stirring motor 122 through the control unit 400 to pre-stir the powder to ensure that the powder is free of lumps;

[0109] 2. The operator sets printing-related parameters through the control unit 400, including preset printing speed, target powder amount, output voltage of electrostatic generator, etc., and at the same time completes the calibration of paper width detection sensor 200 to ensure detection accuracy;

[0110] 3. Start the micro air pump of the pressure powder spraying mechanism 124 to ventilate under no-load conditions, and expel air and residual impurities from the powder conveying pipeline. After the air pressure stabilizes, start the quantitative powder feeding mechanism 123 to deliver powder under no-load conditions for a short period of time to ensure that the powder conveying pipeline is full of powder and to avoid powder interruption during normal operation.

[0111] 4. Check the working status of each actuator, confirm that the switch valve shaft 126 is in the initial conduction position, the electrostatic generator 300 is in standby mode, and all sensors have no fault alarms.

[0112] (II) Printing area adaptive adjustment stage

[0113] 1. When the offset printing machine starts feeding paper, the paper is conveyed to the detection area of ​​the paper width detection sensor 200 via the paper feed roller. The sensor detects the width of the paper in real time and transmits the detection signal to the control unit 400 in real time.

[0114] 2. After receiving the detection signal, the control unit 400 extracts the paper width data and matches it with the internally stored paper width-powder head correspondence table to determine the number of side powder heads 112 that need to be turned on / off.

[0115] 3. The control unit 400 sends a control command to the drive mechanism 127. The drive mechanism 127 drives the switch valve shaft 126 to rotate 90° to the specified position, selectively blocking the second cavity part of the channel of the powder spraying seat 125, so that the corresponding side powder spraying head 112 stops supplying powder, thereby achieving the matching of the powder spraying width and the printing width.

[0116] 4. When the paper size changes (such as when changing to a different size of paper), the paper size detection sensor 200 detects the change in size in real time and transmits the change signal to the control unit 400. The control unit 400 quickly completes the action control of the drive mechanism 127, realizes the rapid start and stop switching of the side powder spraying head 112, and ensures the real-time adaptive adjustment of the powder spraying size.

[0117] (III) Electrostatic charging and powder adsorption stage

[0118] 1. The ink transfer device of the offset printing machine transfers ink to the surface of roller 1. Roller 1 rotates and transfers the ink pattern to the paper surface. At this time, the control unit 400 controls the negative ion generator 310 to turn on and emit a negative ion stream to the surface of roller 1, so that the ink particles are negatively charged.

[0119] 2. The quantitative powder dispensing mechanism 123 quantitatively delivers the powder in the powder spraying tank 121 to the pressure powder spraying mechanism 124. The powder mixes with compressed air to form an air-powder mixture flow. After being divided by the powder spraying seat 125, it is delivered to the middle powder spraying head 111 and the opened side powder spraying head 112 respectively.

[0120] 3. When the air-powder mixture is ejected from the powder outlet of the powder nozzle, the control unit 400 controls the positive ion generator 320 to turn on, and emits a positive ion stream into the air-powder mixture at the powder outlet, so that the powder particles are positively charged.

[0121] 4. Positively charged powder particles are sprayed onto the negatively charged ink pattern surface of paper. Under the electrostatic attraction of opposite charges, the powder particles quickly and tightly adhere to the ink pattern surface, such as... Figure 12 As shown. At the same time, the power of compressed air ensures that the powder is evenly covered, achieving powder spraying without dead angles. Electrostatic attraction effectively avoids powder splashing and loss, improving the powder adsorption efficiency and adhesion.

[0122] 5. The control unit 400 adjusts the powder feeding speed of the quantitative powder dispensing mechanism 123 and the air pressure of the pressure powder spraying mechanism 124 in real time according to the actual printing speed of the offset printing machine to ensure that the amount of powder sprayed matches the printing speed. At the same time, it adjusts the output voltage of the electrostatic generator 300 to ensure that the electrostatic adsorption effect is always in the best state.

[0123] (iv) Shutdown and Finalization Phase

[0124] 1. After the offset printing machine finishes printing and stops feeding paper, the control unit 400 controls the quantitative powder feeding mechanism 123 to immediately stop feeding powder, and the pressure powder spraying mechanism 124 continues to ventilate for 3-5 seconds to spray out all the residual powder in the powder conveying pipe to prevent the powder from clumping in the pipe.

[0125] 2. The electrostatic generator 300 shuts off after a 5-second delay to ensure the charged adsorption of residual powder in the pipeline, and then the stirring motor 122 stops working;

[0126] 3. In case of long-term shutdown, the operator can turn off the air pump of the pressure powder spraying mechanism 124, clean the powder outlet of the powder spraying head to prevent powder blockage, and at the same time check the powder level in the powder spraying tank 121 and replenish it in time.

[0127] The paper width adaptive electronic powder spraying device and control method of this invention completely solves the problems of traditional powder spraying devices that require manual adjustment, are prone to powder waste or printing smudges, by real-time detection of the paper width and automatic adjustment of the powder spraying width. By using an electrostatic generator to make the ink / paper and powder carry opposite charges, the electrostatic attraction is used to enhance the powder adsorption force, effectively reducing powder splashing and loss, reducing environmental pollution, and improving the powder spraying quality of the printed products. The overall device has a compact structure, strong compatibility with offset printing machines, simple operation, and convenient maintenance. It can be widely used in powder spraying operations of various offset printing machines and has significant economic and practical value.

[0128] The preferred embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and the devices and structures not described in detail should be understood as being implemented in a conventional manner in the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention's technical solutions still fall within the protection scope of the present invention.

Claims

1. An electronic powder spraying device for a format-adaptive offset printing machine, the offset printing machine comprising an ink transfer device and a roller, wherein ink with a pattern on it is transferred from the ink transfer device to the roller and then from the roller to the paper, characterized in that, The adaptive offset printing machine electronic powder spraying device includes: The powder spraying device includes a row of powder spraying heads for spraying powder onto the surface of paper. The row of powder spraying heads includes a central powder spraying head and side powder spraying heads located on both sides of the central powder spraying head in the paper width direction. Paper size detection sensor, used to detect the size of printing paper; An electrostatic generator, connected to a control unit, includes a negative ion generator and a positive ion generator. The negative ion generator emits negative ions towards the roller and / or paper, causing the ink particles to carry a negative charge and / or the paper to carry a negative charge. The positive ion generator emits positive ions towards the powder outlet of a row of powder spraying heads, causing the sprayed powder to carry a positive charge. The powder is adsorbed onto the paper or the ink pattern on the paper by utilizing the principle of attraction between opposite charges. The control unit is connected to the powder spraying device, the paper width detection sensor, and the electrostatic generator. The control unit controls whether the side powder spraying head sprays powder according to the paper width detection sensor to keep the powder spraying width synchronized with the printing width, and controls the operation of the electrostatic generator.

2. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 1, characterized in that, The powder spraying device also includes a powder supply device for conveying powder to the powder spraying device. The powder supply device includes a powder spraying tank, a stirring motor, a quantitative powder dispensing mechanism, a pressure powder spraying mechanism, and a powder spraying base. The powder spraying tank contains powder and is equipped with a stirring shaft. The stirring motor is connected to the stirring shaft inside the powder spraying tank, and is used to drive the stirring shaft to rotate and stir the powder; The quantitative powder dispensing mechanism is connected to the powder outlet at the bottom of the powder spraying tank and is used to quantitatively convey powder to the pressure powder spraying mechanism; The pressure powder spraying mechanism delivers powder to the powder spraying station at a constant pressure; The powder spraying base has a first cavity and a second cavity inside. Both the first cavity and the second cavity are connected to the pressure powder spraying mechanism. The bottom outlet of the first cavity is connected to a number of first powder outlets, and the bottom outlet of the second cavity is connected to a number of second powder outlets. The first powder outlets and the second powder outlets are respectively connected to the middle powder spraying head and the side powder spraying head through pipes. The switching valve shaft is rotatably disposed inside the powder spraying base. A through hole is provided on the switching valve shaft corresponding to the position of the second cavity. The switching valve shaft has a conducting position and a blocking position. When it is in the conducting position, the through hole is connected to the second cavity, and the second powder outlet normally conveys powder to the side powder spraying head. When rotated to the blocking position, the through hole is misaligned with the second cavity, and the second powder outlet stops conveying powder to the side powder spraying head. The drive mechanism is mechanically connected to the switching valve shaft and communicatively connected to the control unit. The drive mechanism receives signals from the control unit and switches the on and off states of the switching valve shaft.

3. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 2, characterized in that, The drive mechanism includes a drive motor and a gear transmission mechanism. The drive motor is communicatively connected to the control unit and is connected to the switching valve shaft via the gear transmission mechanism, driving the switching valve shaft to rotate; or The drive mechanism includes a cylinder and a connecting rod. The cylinder is communicatively connected to the control unit. The two ends of the connecting rod are rotatably connected to the piston rod of the cylinder and the switching valve shaft. The forward and backward movement of the cylinder drives the switching valve shaft to rotate through the connecting rod.

4. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 3, characterized in that, The rotation angle of the switch valve shaft is 90°, and the 90° rotation enables the through hole to be fully connected or completely blocked from the second cavity.

5. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 1, characterized in that, A row of powder spraying heads is arranged at equal intervals along the width of the paper. The middle powder spraying head corresponds to the center area of ​​the printing area, and there are at least two sets of side powder spraying heads. The control unit selectively closes some of the side powder spraying heads by controlling the rotation position of the switch valve shaft, thereby realizing the segmented adjustment of the powder spraying area.

6. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 1, characterized in that, It also includes a sealing structure located at the contact surface between the switch valve shaft and the powder spraying seat to prevent powder from leaking from the shaft gap. The sealing structure includes a sealing groove located inside the switch valve shaft and a sealing ring installed in the sealing groove.

7. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 1, characterized in that, The paper size detection sensor is one or more of the following: photoelectric edge detection sensor, ultrasonic edge sensor, laser distance sensor, contact sensor, and CCD machine vision sensor.

8. The electronic powder spraying device for a width-adaptive offset printing machine according to claim 1, characterized in that, The negative ion generator is located near the roller, and the positive ion generator is located near the powder outlet of the powder spraying device. The electrostatic generator is electrically connected to the control unit, which controls its start / stop or working intensity.

9. A powder spraying control method based on the electronic powder spraying device of any one-page adaptive offset printing machine according to claims 1-8, characterized in that, Control methods include: Printing area adaptive adjustment: The paper size detection sensor detects the paper size in real time and sends the detection signal to the control unit. The control unit determines which side powder spraying heads need to be turned on or off based on the detected paper size, so that the powder spraying width is synchronized with the printing width. Electrostatic charging and powder adsorption: During the ink transfer process, the negative ion generator is controlled to emit negative ions towards the roller and / or paper, so that the ink particles and / or the ink pattern on the paper are negatively charged. During the powder spraying process, the positive ion generator is controlled to emit positive ions at the powder outlet of the powder spraying head, so that the sprayed powder is positively charged. Utilizing the principle of attraction between opposite charges between ink patterns and powder, powder is adsorbed onto paper or ink patterns on paper.

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