Cleaning nozzle and cleaning device

Abstract

The utility model discloses a cleaning nozzle and cleaning device, the cleaning nozzle includes: the main body structure is equipped with the air blowing channel and the air suction channel in it, and the main body structure is equipped with the cleaning face to the product to be cleaned, a plurality of air blowing holes are all arranged in the middle part of the cleaning face, and the air blowing hole is connected with the air blowing channel, and a plurality of air blowing holes include center air blowing hole and edge air blowing hole, and the through-flow area of center air blowing hole is greater than the through-flow area of edge air blowing hole, a plurality of air suction holes are all arranged on the cleaning face, and the air suction hole is arranged on the periphery of air blowing hole, and the air suction hole is connected with the air suction channel, and the vertical projection of a plurality of air suction holes on the cleaning face and the vertical projection of the product to be cleaned on the cleaning face keep interval arrangement. In the case where the same air blowing height and air blowing flow, increase the through-flow area of center air blowing hole more favorably bring greater cleaning coverage area, and the exhaust gas flow is just located the suction path of air suction hole when flowing out the product to be cleaned, can bring more smooth exhaust path.

Description

Technical Field

[0001] This utility model relates to the technical field of photosensitive sensor packaging, and particularly to cleaning nozzles and cleaning devices. Background Technology

[0002] Before packaging, the photosensitive sensor is picked up by an automatic feeding robot and placed in a buffer tray. The buffer tray is a transfer platform for the photosensitive sensor before testing. The buffer tray has multiple stations arranged in a ring, each station is used to place a photosensitive sensor. The photosensitive sensor completes the feeding, cleaning and unloading processes in sequence through the rotation of the buffer tray.

[0003] The cleaning process is achieved through blowing and sucking air, such as... Figure 1 As shown, multiple air holes blow air into the photosensitive sensor. The airflow impacts the product surface and carries away dust and other foreign objects. The cleaned exhaust air is sucked into the air intake and discharged through the air intake channel.

[0004] In existing technology, the suction port surrounds the blowing port, resulting in a much larger flow area for the suction port compared to the blowing port. Consequently, the air pressure and flow rate at the suction port are lower than those at the blowing port, leading to turbulent airflow in the cleaned exhaust gas (see appendix for details). Figure 2 (Simulation diagram) The cleaning exhaust gas cannot be effectively discharged, resulting in a reduction in the cleaning effect. Utility Model Content

[0005] The present invention aims to provide a cleaning nozzle that can efficiently clean a photosensitive sensor.

[0006] A cleaning nozzle according to a first aspect embodiment of the present invention comprises:

[0007] The main structure has an air blowing channel and an air suction channel inside, and the main structure has a cleaning surface facing the product to be cleaned.

[0008] The device has multiple air holes, all of which are located in the middle of the cleaning surface and are connected to the air blowing channel. The air hole closest to the center of the cleaning surface is defined as the central air hole, and the remaining air holes are defined as edge air holes. The flow area of ​​the central air hole is greater than the flow area of ​​any one of the edge air holes.

[0009] The device has multiple air intake holes, all of which are located on the cleaning surface and are positioned around the air blowing holes. The air intake holes are connected to the air intake channel. The vertical projections of the multiple air intake holes on the cleaning surface are spaced apart from the vertical projections of the product to be cleaned on the cleaning surface.

[0010] The cleaning nozzle according to the embodiments of this utility model has at least the following beneficial effects: Compared with the prior art, under the same blowing height and blowing flow rate, increasing the flow area of ​​the central blowing hole is more conducive to bringing a larger cleaning coverage area. The blowing airflow flows from the center of the product to be cleaned to the edge of the product to be cleaned, smoothly carrying away the dust on the surface of the product to be cleaned. When the exhaust airflow flows out of the product to be cleaned, it is exactly in the suction path of the suction hole. The high pressure area of ​​the exhaust changes, making the exhaust path clearer and more controllable. Figure 3 As can be seen from the simulation diagram, optimizing the exhaust path can result in a smoother exhaust path, with no turbulent exhaust gas flow above the product to be cleaned, thereby preventing the exhaust gas from re-contaminating the product after cleaning and thus improving the cleaning effect of the entire system.

[0011] According to some embodiments of the present invention, the plurality of air intake holes are all waist-shaped holes, and the plurality of waist-shaped holes are arranged at an angle close to two adjacent side strips of the product to be cleaned.

[0012] According to some embodiments of the present invention, the vertical projection of the plurality of air holes on the cleaning surface does not exceed the vertical projection of the product to be cleaned on the cleaning surface.

[0013] According to some embodiments of the present invention, the ratio of the flow area of ​​the central air blowing hole to that of any one of the edge air blowing holes is less than 1.5 times.

[0014] According to some embodiments of this utility model, the central air blowing hole is a strip-shaped hole, and the edge air blowing hole is a round hole or a strip-shaped hole.

[0015] According to some embodiments of the present invention, the strip-shaped hole extends along the width direction of the product to be cleaned.

[0016] According to some embodiments of the present invention, the total flow area of ​​the plurality of air intake holes is 1.5 to 2 times the total flow area of ​​the plurality of air blowing holes.

[0017] According to some embodiments of the present invention, the distance from the air intake hole to the product to be cleaned is greater than the distance from the air blowing hole to the product to be cleaned.

[0018] According to some embodiments of the present invention, the cleaning surface is provided with a groove, a plurality of air intake holes are provided in the groove, and a plurality of air blowing holes are provided outside the groove.

[0019] The cleaning device according to a second aspect embodiment of the present invention includes:

[0020] The cleaning nozzle of the first aspect embodiment of this utility model;

[0021] The carrier tray is provided with multiple positioning slots for placing the product to be cleaned. Each positioning slot has a moving path directly opposite the cleaning surface under the rotation drive of the carrier tray. A clamping gap is provided between the positioning slot and the product to be cleaned. The vertical projections of the multiple air holes on the cleaning surface and the vertical projections of the clamping gaps on the cleaning surface overlap with each other.

[0022] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0023] Figure 1 This is a 3D structural diagram of an existing cleaning nozzle;

[0024] Figure 2 This is a simulation diagram of the airflow when an existing cleaning nozzle is in operation;

[0025] Figure 3 This is a simulation diagram of the airflow of the cleaning nozzle provided in this embodiment of the utility model during operation;

[0026] Figure 4 This is a three-dimensional structural diagram of the cleaning nozzle provided in an embodiment of the present utility model;

[0027] Figure 5 This is another three-dimensional structural diagram of the cleaning nozzle provided in this embodiment of the utility model;

[0028] Figure 6 yes Figure 5 A bottom view of the cleaning nozzle shown;

[0029] Figure 7 yes Figure 6 The image shows a bottom view of the cleaning nozzle and the product to be cleaned.

[0030] Figure 8 This is a three-dimensional structural diagram of the cleaning device provided in an embodiment of the present utility model;

[0031] Figure 9 yes Figure 7 The image shows a bottom view of the cleaning nozzle, the product to be cleaned, and the carrier tray.

[0032] In the attached diagram: 100-Main structure, 210-Blowing nozzle, 310-Suction nozzle, 200-Blowing channel, 300-Suction channel, 320-Suction hole, 230-Through hole, 231-Plug, 110-Cleaning surface, 400-Product to be cleaned, 221-Central blowing hole, 222-Edge blowing hole, 120-Groove, 10-Frame, 20-Carrier tray, 30-Cleaning nozzle, 21-Positioning groove, 22-Feeding station, 23-Cleaning station, 24-Unloading station, 410-Clamping position, 401-Maximum clamping gap. Detailed Implementation

[0033] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0034] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0035] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0036] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0037] like Figures 4 to 6As shown, this embodiment of the utility model provides a cleaning nozzle 30, which includes a main structure 100, an air blowing nozzle 210, and an air suction nozzle 310. The main structure 100 has an air blowing channel 200 and an air suction channel 300. The air blowing channel 200 penetrates the upper surface and lower bottom surface of the main structure 100, and is located in the middle of the main structure 100. It is divided into a main air blowing channel and auxiliary air blowing channels. Multiple auxiliary air blowing channels are provided, all of which are connected to the lower side of the main air blowing channel. Each auxiliary air blowing channel forms an air blowing hole on the lower bottom surface of the main structure 100, while the air blowing nozzle 210 is connected to the upper side of the main air blowing channel. When compressed gas enters the air blowing channel 200 through the air blowing nozzle 210, the compressed gas first passes through the main air blowing channel, and then, under the diversion of the auxiliary air blowing channels, is discharged from each air blowing hole to achieve the blowing action.

[0038] On the other side, the intake channel 300 runs through the upper and lower surfaces of the main structure 100. The intake channel 300 is divided into a main intake channel and multiple auxiliary intake channels. The upper side of the main intake channel is connected to an intake nozzle 310, and the multiple auxiliary intake channels are all connected to the lower side of the main intake channel. The multiple auxiliary intake channels extend horizontally through crossbeams and then extend downwards to the lower surface of the main structure 100. Each auxiliary intake channel forms an intake hole 320 on the lower surface of the main structure 100. At this time, the multiple intake holes 320 are all located around all the blowing holes. When the negative pressure suction acts on the intake channel 300 through the intake nozzle 310, the main intake channel presents a negative pressure, causing each auxiliary intake channel to also present a negative pressure. External airflow is drawn from each intake hole 320 into the auxiliary intake channel and merges into the main intake channel, and finally exits from the intake nozzle 310 to achieve the intake action.

[0039] In this embodiment, the blowing channel 200 and the suction channel 300 share the same air source. Since the air source forms positive and negative pressures through a vacuum generator, the positive and negative air pressures remain consistent. If the flow area of ​​the suction port 320 is much larger than the flow area of ​​the blowing port, the exhaust pressure and flow rate will be lower than those under the blowing condition, resulting in turbulent airflow of the cleaned exhaust gas (see Appendix for details). Figure 2 (Simulation diagram), the cleaning exhaust gas cannot be effectively discharged, resulting in a reduction in cleaning effect. Compared with the prior art, the suction port 320 of this utility model is designed independently as an individual unit, rather than being enclosed in a large area of ​​suction ring holes. The advantage of this design is that it can enhance the exhaust pressure and flow rate, so that the exhaust pressure and flow rate of the suction port 320 can approach the working conditions of the blowing port. The high-pressure area of ​​the exhaust is changed, making the exhaust path clearer and more controllable.

[0040] like Figure 4As shown, furthermore, to meet the processing requirements of the secondary intake channel, multiple through holes 230 need to be machined on the side of the main structure 100. All through holes 230 are located on the same horizontal plane and distributed in a "well" pattern, so that all through holes 230 can be interconnected. Furthermore, the main intake channel needs to be connected to one of the through holes 230. After machining the multiple through holes 230, plugs 231 are used to seal the openings of each through hole 230, thus forming the horizontal channel of the secondary intake channel. Finally, according to the designed number of intake holes 320, multiple vertical channels connected to any horizontal channel are machined from the bottom surface of the main structure 100, so that the secondary intake channel can form multiple intake holes 320 on the bottom surface of the main structure 100.

[0041] It should be noted that the appendix Figure 4 The internal structure of the blowing channel 200, the suction channel 300 and the through hole 230 is shown, while the internal structure of the auxiliary blowing channel, the vertical channel, the blowing hole and the suction hole 320 are omitted.

[0042] It is understood that, for ease of description, this embodiment defines the bottom surface of the main structure 100 as the cleaning surface 110, which faces the surface of the product 400 to be cleaned during operation. When air is expelled from the air outlet, the high-pressure airflow can carry away the dust on the surface of the product 400 to be cleaned. Then the airflow flows towards the edge of the product 400 to be cleaned and is eventually drawn in by the multiple air intakes 320 to form an airflow circulation, preventing the exhaust airflow from re-contaminating the product.

[0043] like Figures 5 to 7 As shown, there are multiple air holes, which are generally arranged along the length of the product 400 to be cleaned. If the product 400 is square, the air holes are arranged in a conventional direction. However, regardless of the arrangement of the air holes, the vertical projection of all air holes onto the cleaning surface 110 does not exceed the vertical projection of the product 400 onto the cleaning surface 110. In other words, all air holes blow air directly onto the product 400 to be cleaned.

[0044] Since the air blowing channel 200 is located in the middle of the main structure 100, the air blowing holes are also distributed in the middle of the cleaning surface 110. In this embodiment, the air blowing hole closest to the center of the cleaning surface 110 is defined as the central air blowing hole 221, and the remaining air blowing holes are defined as edge air blowing holes 222. There is one central air blowing hole 221 and two edge air blowing holes 222, which are distributed on both sides of the central air blowing hole 221. Through simulation, if the flow area of ​​the central air blowing hole 221 is greater than the flow area of ​​any one of the edge air blowing holes 222, under the same blowing height and blowing flow rate, increasing the flow area of ​​the central air blowing hole 221 is more conducive to bringing a larger cleaning coverage area. The airflow flows from the center of the product 400 to the edge of the product 400 to be cleaned, successfully carrying away the dust on the surface of the product 400 to be cleaned.

[0045] Even so, the flow area of ​​the central air outlet 221 should not be set too large, and it is recommended to maintain it within 1.5 times the flow area of ​​any one of the edge air outlets 222. If the flow area of ​​the central air outlet 221 is set too large, the air pressure and flow velocity of the central air outlet 221 will be significantly lower than those of the edge air outlets 222, causing the clean airflow to converge towards the center. Therefore, maintaining the flow area of ​​the central air outlet 221 within 1.5 times the flow area of ​​any one of the edge air outlets 222 can prevent foreign objects from being blown towards the center. Of course, this utility model does not limit the number of edge air outlets 222; it can also be one, three, four, etc., and is not limited to the above embodiment.

[0046] Although the flow area of ​​the central air hole 221 is larger than that of any one of the edge air holes 222, due to the limitations of the machining size of the air blowing area, if the central air hole 221 is a circular hole, the interval between the central air hole 221 and the adjacent edge air holes 222 will be smaller within the limited air blowing area, which is not conducive to machining. Therefore, the central air hole 221 can be set as a strip-shaped hole that extends along the width direction of the product 400 to be cleaned.

[0047] With the above configuration, a larger cleaning coverage area can be achieved without increasing the length of the central air hole 221. Similarly, if the product 400 to be cleaned has a large width, the edge air holes 222 can be changed to strip-shaped holes to increase the cleaning surface area 110, which also extends along the width of the product 400 to be cleaned.

[0048] In this embodiment, if the product 400 to be cleaned is rectangular, then there are four suction holes 320. These four suction holes 320 are distributed around the four corners of the rectangular product, and the vertical projections of the suction holes 320 onto the cleaning surface 110 are spaced apart from the vertical projections of the product 400 to be cleaned onto the cleaning surface 110. That is, none of the suction holes 320 are directly facing the product 400 to be cleaned. This is because when the airflow moves outward from the center of the product 400, if the suction holes 320 are positioned directly on the product 400, the airflow will be drawn in before leaving the product 400, resulting in the edges of the product 400 not being properly cleaned. However, the suction holes 320 cannot be too far from the product 400 to be cleaned; the specific reasons for this need to be analyzed in conjunction with the structure of the carrier tray 20.

[0049] In summary, the vertical projections of the multiple air intakes 320 on the cleaning surface 110 and the vertical projections of the product 400 to be cleaned on the cleaning surface 110 must be set at a certain interval. Based on this, all the air intakes 320 are configured as oblong holes, and these oblong holes are arranged at an angle close to two adjacent edge strips of the product 400 to be cleaned. The structure at this point can be referenced in the appendix. Figure 7 The waist-shaped suction hole 320 is inclined at an angle of 40° to 50°, preferably 45°, relative to the strip-shaped central blowing hole 221. This inclined waist-shaped hole creates a slanted airflow channel, allowing the suction range to cover the area between two adjacent side strips, reducing dead zones in traditional single-side suction and expanding the airflow coverage. Furthermore, compared to a round hole design, the waist-shaped hole concentrates the airflow path to reduce turbulence.

[0050] Since the blowing channel 200 and the inhalation channel 300 share the same air source, and the positive and negative air pressures remain consistent, it is necessary to control the total flow area of ​​the multiple inhalation holes 320. In this embodiment, the total flow area of ​​the multiple inhalation holes 320 is maintained at 1.5 to 2 times the total flow area of ​​the multiple blowing holes. Maintaining this ratio can maintain the dynamic balance between the blowing and inhalation actions, resulting in a generally stable airflow and reduced turbulence.

[0051] It should be further explained that, precisely because the total flow area of ​​the air intake 320 is limited, it is positioned at an angle close to the two adjacent side strips of the product 400 to be cleaned. This not only meets the need to expand the air intake range, but also further controls the total flow area of ​​the air intake 320.

[0052] In some embodiments of this invention, the cleaning surface 110 is provided with a groove 120, and multiple suction holes 320 are disposed within the groove 120, while multiple blowing holes are disposed outside the groove 120. This results in the distance from the suction holes 320 to the product 400 to be cleaned being greater than the distance from the blowing holes to the product 400 to be cleaned. The near end of the blowing holes can form a directional high-pressure airflow, effectively stripping dust from the surface of the product 400 to be cleaned, while the far end of the suction holes 320 can form a stable negative pressure zone, preventing the blowing airflow from being drawn away prematurely. Furthermore, the high pressure near the blowing holes and the low pressure far from the suction holes 320 can form a gradient pressure difference, thereby enhancing the shearing and transporting ability of the airflow on dust.

[0053] With the above structure, the exhaust gas flow is positioned precisely in the intake path of the suction port 320 when it exits the product to be cleaned 400. This alters the high-pressure zone of the exhaust, making the exhaust path clearer and more controllable. Figure 3 As can be seen from the simulation diagram, the optimization of the exhaust air path can bring a smoother exhaust path, and there is no turbulent exhaust airflow above the product to be cleaned 400, thereby avoiding the exhaust gas from re-contaminating the product after cleaning, and thus improving the cleaning effect of the entire system.

[0054] like Figure 8 and Figure 9 As shown in the figure, this utility model embodiment also provides a cleaning device, including a frame 10, a carrier tray 20, a drive device (not shown in the figure), and the aforementioned cleaning nozzle 30. The drive device is installed inside the frame 10 and is used to drive the carrier tray 20 to rotate horizontally. The carrier tray 20 is provided with a plurality of positioning grooves 21 for placing the product 400 to be cleaned. The carrier tray 20 can be called a buffer tray, which has a feeding station 22, a cleaning station 23, and a discharging station 24. The material is moved sequentially from the feeding station 22 to the cleaning station 23 and the discharging station 24 by the rotation of the carrier tray 20.

[0055] Meanwhile, each positioning slot 21 has a moving path facing the cleaning surface 110 of the main structure 100 under the rotational drive of the carrier plate 20. That is to say, each product 400 to be cleaned can move to the cleaning surface 110 facing the main structure 100 under the drive of the carrier plate 20, so that the cleaning nozzle 30 can clean all passing products 400.

[0056] To simplify control, multiple positioning slots 21 are arranged around the central circumference of the carrier disk 20, so that any two adjacent positioning slots 21 maintain the same angular displacement. The driving device can be a cam gap divider, which rotates at a fixed angular velocity each time, which is very suitable for the above-mentioned positioning slot 21 setting.

[0057] Furthermore, the product 400 to be cleaned uses the positioning groove 21 of the carrier 20 as a carrier, and sufficient clamping clearance needs to be reserved between the product 400 to be cleaned and the positioning groove 21 for the robot to load or unload. Specifically, clamping positions 410 are provided at the corners of the product 400 to be cleaned, and the clamping positions 410 and the positioning groove 21 maintain a maximum clamping clearance 401, which is used for the robot to load or unload.

[0058] like Figure 9 As shown, the vertical projections of the multiple suction holes 320 on the cleaning surface 110 overlap with the vertical projection of the maximum clamping gap 401 on the cleaning surface 110. The reason the suction holes 320 cannot be too far from the product 400 to be cleaned is that when the exhaust gas rises along the steps of the positioning groove 21, if the vertical projections of the multiple suction holes 320 on the cleaning surface 110 overlap with the vertical projection of the maximum clamping gap 401 on the cleaning surface 110, the airflow will be positioned precisely on the suction path of the suction holes 320 during its ascent, achieving a more efficient result. If the suction holes 320 are too far from the product 400 to be cleaned, causing the vertical projections of the multiple suction holes 320 on the cleaning surface 110 and the vertical projection of the maximum clamping gap 401 on the cleaning surface 110 to not overlap, then the airflow will be somewhat obstructed when drawn in by the suction holes 320.

[0059] Since the cleaning device adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0060] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.

Claims

1. A cleaning nozzle, characterized in that, include: The main structure has an air blowing channel and an air suction channel inside, and the main structure has a cleaning surface facing the product to be cleaned. The device has multiple air holes, all of which are located in the middle of the cleaning surface and are connected to the air blowing channel. The air hole closest to the center of the cleaning surface is defined as the central air hole, and the remaining air holes are defined as edge air holes. The flow area of ​​the central air hole is greater than the flow area of ​​any one of the edge air holes. The device has multiple air intake holes, all of which are located on the cleaning surface and are positioned around the air blowing holes. The air intake holes are connected to the air intake channel. The vertical projections of the multiple air intake holes on the cleaning surface are spaced apart from the vertical projections of the product to be cleaned on the cleaning surface.

2. The cleaning nozzle according to claim 1, characterized in that: All of the aforementioned air intake holes are waist-shaped holes, and the multiple waist-shaped holes are arranged at an angle close to two adjacent side strips of the product to be cleaned.

3. The cleaning nozzle according to claim 1, characterized in that: The vertical projection of each of the multiple air holes on the cleaning surface does not exceed the vertical projection of the product to be cleaned on the cleaning surface.

4. The cleaning nozzle according to claim 1 or 3, characterized in that: The ratio of the flow area of ​​the central air vent to that of any one of the edge air vents is less than 1.

5.

5. The cleaning nozzle according to claim 1, characterized in that: The central air inlet is a strip-shaped hole, and the edge air inlets are round holes or strip-shaped holes.

6. The cleaning nozzle according to claim 5, characterized in that: The strip-shaped hole extends along the width direction of the product to be cleaned.

7. The cleaning nozzle according to claim 1, characterized in that: The total flow area of ​​the plurality of air intake holes is 1.5 to 2 times the total flow area of ​​the plurality of air blowing holes.

8. The cleaning nozzle according to claim 1, characterized in that: The distance from the air intake to the product to be cleaned is greater than the distance from the air blower to the product to be cleaned.

9. The cleaning nozzle according to claim 8, characterized in that: The cleaning surface is provided with a groove, and a plurality of air intake holes are provided in the groove, while a plurality of air blowing holes are provided outside the groove.

10. A cleaning device, characterized in that, include: The cleaning nozzle as described in any one of claims 1 to 9; The carrier tray is provided with multiple positioning slots for placing the product to be cleaned. Each positioning slot has a moving path directly opposite the cleaning surface under the rotation drive of the carrier tray. A clamping gap is provided between the positioning slot and the product to be cleaned. The vertical projections of the multiple air holes on the cleaning surface and the vertical projections of the clamping gaps on the cleaning surface overlap with each other.

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