A paper staple-free perfect binding machine

Abstract

This utility model proposes a staple-free perfect binding machine for paper, including a paper feeding table, a conveyor table, a folding and gluing unit, a three-sided cutting unit, and a collection unit arranged sequentially. The first clamping plate is a V-shaped plate composed of a horizontal plate and a diagonal fixing plate, which is fixedly connected to the frame. A second clamping plate is attached to the first fixing plate. A connecting column connects the first and second clamping plates, stabilizing the first clamping plate. A glue sprayer is fixed to the diagonal fixing plate, with the spray nozzle facing the end of the conveyor table. Through the internal structure of the cold glue applicator assembly, perfect binding can be achieved without vibration, achieving 1mm glue application without increasing the thickness of the binding. The design of the gluing section and the cold glue applicator assembly, along with their integration with the entire machine, eliminates the need for a separate perfect binding module, enabling staple-free perfect binding of books and significantly reducing equipment costs.

Description

Technical Field

[0001] This utility model relates to the field of printing technology, and in particular to a nail-free glue brush device. Background Technology

[0002] Existing books and other printed materials need to be folded, so folds are made in the middle of the paper. Staples are usually used to bind them at the folds. Figure 1-2 As shown, the iron staple 103 is placed between the first sheet 101 and the second sheet 102. When folded, the staple protrudes from the left side of the book. While this achieves binding, it presents several problems. For example:

[0003] 1. Staples have volume, and when folded, they make the folded part thicker, which increases the thickness of the edges of the book after it is folded.

[0004] 2. For some confidential documents used in meetings, there is a risk that the bindings may be disassembled, printed, and then the bindings restored to form the original document.

[0005] 3. The use of staples not only wastes resources, but also requires removing the staples before the paper can be shredded, which is a cumbersome process.

[0006] 4. During long-term storage, iron staples will rust, increasing storage costs.

[0007] To address this issue, existing equipment includes a small number of post-press binding machines that use direct perfect binding, and these machines mainly fall into two categories:

[0008] 1. Folding first and then binding uniformly is a cumbersome process with poor results.

[0009] 2. Setting up a separate glue binding module would be extremely costly.

[0010] Therefore, there is an urgent need for a low-cost post-press binding device that can achieve perfect binding. Utility Model Content

[0011] The purpose of this invention is to at least solve one of the aforementioned technical defects.

[0012] Therefore, one objective of this utility model is to propose a paper binding machine that eliminates the need for staples during printing, in order to solve the problems mentioned in the background art and overcome the shortcomings of the existing technology.

[0013] A paper staple-free perfect binding machine includes a paper feeding table, a conveyor table, a three-sided cutting unit, and a collection unit arranged in sequence. The machine is characterized by further including a folding and gluing unit, which is located in front of the three-sided cutting unit and includes a folding part and a gluing part arranged vertically. The folding part includes folding wheels, a conveyor belt, and a guide plate arranged horizontally. The gap between the two conveyor belts can clamp the paper and fold it. The gluing part includes a cold glue applicator assembly.

[0014] The cold glue applicator assembly includes a glue sprayer, a first clamping plate, a second clamping plate, a connecting column, and a first fixing plate. The first clamping plate is a V-shaped plate, consisting of a horizontal plate and an inclined fixing plate. The first fixing plate is fixedly connected to the frame. The second clamping plate is based on the first fixing plate. The connecting column connects the first clamping plate and the second clamping plate. The first clamping plate is stably fixed by the second clamping plate and the connecting column. The glue sprayer is fixed on the inclined fixing plate, and the glue spraying head at the end of the glue sprayer faces the end of the transfer table.

[0015] Preferably, in any of the above solutions, the first fixing plate is a plate-shaped structure, the second clamping plate is a plate-shaped structure, the upper surface of the second clamping plate is attached to the lower surface of the first fixing plate, and the lower surface of the second clamping plate is attached to the upper plate surface of the frame.

[0016] Preferably, in any of the above solutions, the angle between the horizontal plate and the inclined fixing plate of the first clamping plate is 100-135°, and the inclined fixing plate is inclined in the paper conveying direction.

[0017] Preferably, of any of the above solutions, the guide plate is in the shape of an "eight" and is located directly below the conveyor belt with its opening facing downwards. The shoulder formed is used to unfold the paper, and the opening angle is 60-160°.

[0018] Preferably, in any of the above embodiments, the cold glue applicator assembly also includes an air nozzle, which is tilted upwards and located at the rear end of the glue spray head, i.e., the flap wheel, the glue spray head, and the air nozzle are arranged in sequence.

[0019] Preferably, any of the above solutions includes a guide rod, which is arranged along the direction of the conveyor belt and extends beyond the vertical projection of the conveyor belt into the paper conveying direction. The guide rod is located below the conveyor belt and is connected to a power device so that it can extend and retract along the conveying direction.

[0020] Preferably, in any of the above solutions, the paper feeding chain is located below the guide rod, the paper feeding chain moves in a circumferential direction, and a paper feeding clamp is provided on the paper feeding chain to carry the paper.

[0021] Preferably, in any of the above solutions, the glue sprayer is connected to an electrical wire, and the electrical wire is connected to a controller; the glue sprayer is connected to a glue delivery pipe, and the other end of the glue delivery pipe is connected to a glue tank.

[0022] Preferably, among the above solutions, the glue spray head is capable of continuously spraying a small amount of glue, with a spray volume of 1 ml / µs.

[0023] Preferably, of the above solutions, the air nozzle can continuously provide air pressure, and the air outlet size is 1.5mm. 2 The wind speed is 0.25-0.3 MPa.

[0024] Compared with the prior art, the advantages and beneficial effects of this utility model are as follows:

[0025] 1. A brand-new perfect binding method has been designed. Through the setting of the glue dispensing part and the cold glue applicator component, and its cooperation with the whole machine, this overall structural layout eliminates the need for a separate perfect binding module, realizing staple-free perfect binding of books and greatly reducing equipment costs.

[0026] 2. The internal structure of the cold glue applicator assembly enables glue binding without vibration, achieves 1mm printing without increasing the thickness of the binding area, and features simple steps and good overall results.

[0027] 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

[0028] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0029] Figure 1 A binding diagram for existing iron nails;

[0030] Figure 2 A folding diagram of existing technology using iron nails after binding;

[0031] Figure 3 This is an overall structural diagram of the paper staple-free offset printing machine of this utility model;

[0032] Figure 4 This is an overall structural diagram of the paper staple-free offset printing machine of this utility model;

[0033] Figure 5 The structural diagram of the folding and dispensing unit according to this utility model (guide paper not shown);

[0034] Figure 6 The diagram below shows the structure of the folding glue dispensing unit according to this utility model.

[0035] Figure 7 The diagram below shows the structure of the folding glue dispensing unit according to this utility model.

[0036] Figure 8The diagram below shows the structure of the folding glue dispensing unit according to this utility model.

[0037] Figure 9 The diagram below shows the structure of the folding glue dispensing unit according to this utility model.

[0038] Figure 10 This is a structural diagram of the folding glue dispensing unit according to the present invention.

[0039] in:

[0040] 101. First sheet of paper; 102. Second sheet of paper; 103. Bookbinding;

[0041] 1. Paper feeding table; 2. Conveyor table; 3. Three-sided cutting unit; 4. Collection unit; 5. Folding and gluing unit; 6. Folding section; 7. Gluing section;

[0042] 1011. Glue sprayer; 1012. First clamping plate; 1013. Connecting column; 1014. Second clamping plate; 1015. Inclined plate; 1016. Air supply pipe; 1017. Glue spray head; 1018. First wire; 1019. Glue supply pipe; 1020. First fixing plate; 1021. Air nozzle; 1022. Folding wheel; 1023. Conveyor belt; 1024. Paper feeding chain; 1025. Guide plate; 1026. Paper feeding clamp; 1027. Upper plate of the frame. Detailed Implementation

[0043] 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 intended to explain this utility model, and should not be construed as limiting this utility model.

[0044] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0045] like Figure 3As shown, an embodiment of the present invention provides a paper staple-free perfect binding machine, comprising a paper feeding table 1, a conveyor table 2, a three-sided cutting unit 3, and a collecting unit 4 arranged sequentially. It also includes a folding and gluing unit 5, which is located in front of the cutting unit 3. The folding and gluing unit 5 includes a folding section 6 and a gluing section 7 arranged vertically. The folding section 6 includes folding wheels 1022 arranged horizontally, a conveyor belt 1023, and a guide plate 1025. The gap between the two conveyor belts 1023 can clamp and fold the paper. The gluing section 7 includes a cold glue applicator assembly.

[0046] The cold glue applicator assembly includes a glue sprayer 1011, a first clamping plate 1012, a second clamping plate 1014, a connecting column 1013, and a first fixing plate 1020. The first clamping plate 1012 is a V-shaped plate, consisting of a horizontal plate and an inclined fixing plate. The first fixing plate 1020 is fixedly connected to the frame. The second clamping plate 1014 is based on the first fixing plate 1020. The connecting column 1013 connects the first clamping plate 1012 and the second clamping plate 1014. The first clamping plate 1012 is stably fixed by the second clamping plate 1014 and the connecting column 1013. The glue sprayer 1011 is fixed on the inclined fixing plate, and the glue spraying head 1017 at the end of the glue sprayer 1011 faces the end of the transfer table 2.

[0047] Furthermore, the glue sprayer 1011 is located below the conveyor belt 1023 and the folding wheel 1022.

[0048] Among them, the paper feeding table 1, the conveying table 2, the trimming unit 3 and the collecting unit 4 all adopt existing technologies. For those skilled in the art, the above structures are all conventional technologies. Any structure that can achieve the above functions can be used as a structural component in this embodiment. Furthermore, the above structures are not the protection points of this utility model. Therefore, the specific structure of the above structures will not be described in detail, but only their functions will be explained.

[0049] The paper feeder 1 holds the printed paper.

[0050] The transfer station 2 transfers the paper forward one sheet at a time.

[0051] The three-sided cutting unit 3 trims and aligns the glued book, leaving the folded side untrimmed while trimming the other three sides with an edge trimmer.

[0052] Collection unit 4 collects and outputs the finished product.

[0053] It is understandable that existing technologies also have folding units, and these folding units are also located at the rear end of the transmission station 2. However, existing folding units only perform folding and do not have a glue dispensing function. Instead, after folding, the binding device performs the binding work, followed by trimming and other subsequent work.

[0054] This invention adds a glue dispensing device to the folding unit, thereby achieving glue binding during the folding process, reducing the need for a separate binding device. This not only improves the product quality of the book but also eliminates the need for an entire binding assembly.

[0055] Books bound using perfect binding have the following advantages: 1. They do not take up space at the fold, and the thickness of the folded section is the same as the rest of the book. 2. They avoid the risk of removing the staples and then restoring the binding for confidential documents. 3. They avoid the waste of metal staples, and the shredding process is simplified as the staples do not need to be removed before shredding the paper.

[0056] Meanwhile, the binding equipment has more than 10,000 parts in its internal binding claws, making it a precision instrument, and it usually has at least 4 binding claws.

[0057] Therefore, reducing the amount of binding equipment can both enhance the product quality of the book and reduce the cost of the equipment.

[0058] As one possible implementation method, such as Figure 5 As shown, the folding and gluing unit 5 includes a folding part 6 and a gluing part 7, which are arranged vertically, i.e., the folding is done first, and then the gluing is done during the paper feeding process.

[0059] The folding section 6 includes folding wheels 1022 arranged on the left and right, a conveyor belt 1023, and a guide plate 1025. The folding wheels 1022 drive the conveyor belt 1023 to rotate. The two conveyor belts 1023 rotate horizontally and have a gap in the middle, thus forming a fold mark on the paper through the gap. The guide plate 1025 is located below the conveyor belt 1023 and is shaped like an "8". Due to the support of the guide plate 1025, the folded paper also forms an "8" shape, thus being conveyed forward.

[0060] It is understandable that, such as Figure 8 As shown, the guide plate 1025 can be two pieces or one piece, as long as it can spread the paper into a figure-eight shape. The highest point of the guide plate 1025 coincides with the gap between the two conveyor belts 1023 in the vertical direction to ensure the smooth transport of the paper.

[0061] The glue spray head 1017 at the end of the glue sprayer 1011 faces the end of the conveyor table 2. During the paper feeding process, glue is sprayed onto the folds, ensuring that each sheet of paper has a small amount of glue at the fold, thus bonding multiple sheets together. The glue spray head 1017 can continuously spray a small amount of glue, at a rate of 1 ml / µs. Excessive spray volume will result in an overly thick fold, while insufficient spray volume will lead to insufficient adhesion and poor bonding. Accurate spraying position and a stable glue volume must be ensured.

[0062] It is understood that the glue sprayer 1011 and glue spray head 1017 adopt existing technology, that is, any existing glue sprayer 1011 and glue spray head 1017 that can achieve the above-mentioned glue spraying effect can be used as the device in this embodiment.

[0063] In this embodiment, to fix the glue sprayer 1011, a fixing component including a first clamping plate 1012, a second clamping plate 1014, a connecting post 1013, and a first fixing plate 1020 is provided to ensure the glue sprayer 1011 operates stably. The first clamping plate 1012, the second clamping plate 1014, and the connecting post 1013 form a clamping plate assembly. The glue sprayer 1011 is fixed on the clamping assembly. The clamping plate assembly fixes the glue sprayer 1011 by clamping it with the upper plate surface 1027 of the frame and the first fixing plate 1020.

[0064] The first clamping plate 1012 consists of a horizontal plate and an inclined fixing plate. The angle between the two is set according to the optimal angle of the spray head to ensure efficient operation of the spray head. As one possible implementation, the angle is between 100° and 150°, and as a most common implementation, 125° is preferred. The sprayer is fixed to the inclined fixing plate by a locking device at its bottom. As one possible implementation, the locking device consists of several screws.

[0065] The connecting post 1013 locks the first clamping plate 1012 and the second clamping plate 1014, and allows adjustment of the height of the first clamping plate 1012 to adjust the height of the injector. The connecting post 1013 can employ any existing technology; as one possible implementation, it uses a combination of bolts and nuts. Alternatively, a spring can be provided between the first clamping plate 1012 and the second clamping plate 1014, with the spring sleeved around the bolt to provide preload.

[0066] The glue sprayer 1011 is fixed to the inclined fixing plate, so that the glue spraying head 1017 at the end of the glue sprayer 1011 faces the end of the conveyor table 2. An appropriate amount of glue is sprayed onto the paper passing through the end. The glue sprayer 1011 is oriented upwards, spraying onto the paper conveying channel, thus achieving glue spraying during the original paper conveying process without adding any additional structural components.

[0067] In another possible implementation, the glue sprayer 1011 is located below the conveyor belt 1023 and the folding wheel 1022, with the glue spray head 1017 tilted upwards in the same direction as the paper conveying direction. In this way, the spraying force of the glue spray head 1017 has a component force in the paper conveying direction, thereby accelerating the paper conveying speed and reducing unnecessary negative effects.

[0068] Furthermore, the first fixing plate 1020 is a plate-shaped structure, the second clamping plate 1014 is a plate-shaped structure, the upper surface of the second clamping plate 1014 is attached to the lower surface of the first fixing plate 1020, and the lower surface of the second clamping plate 1014 is attached to the upper plate surface 1027 of the frame.

[0069] Understandably, the plate-like bonding method increases the contact area, enhances the stability of the fixation, and better prevents the clamp from shaking, thereby ensuring the stable spraying of glue by the glue sprayer 1011, and stably spraying the glue into the folds of the paper.

[0070] Furthermore, the angle between the horizontal plate and the inclined fixing plate of the first clamping plate 1012 is 100-135°, and the inclined fixing plate is tilted in the paper conveying direction to ensure the glue spraying effect of the glue sprayer 1011.

[0071] As one possible implementation, the angle is preferably 125°.

[0072] Furthermore, the guide plate 1025 is in the shape of an "eight" and is located directly below the conveyor belt 1023. Its opening faces downward, and the shoulder formed is used to unfold the paper. The opening angle is 60-160°.

[0073] As one possible implementation, paper without creases, such as A3 paper, tends to be completely folded to 0° after being pressed and conveyed by conveyor belt 1023. However, the paper is unfolded to a suitable angle by the action of guide plate 1025. In this way, it is convenient for glue spraying after folding and printing, as well as for subsequent operations such as conveying.

[0074] Understandably, the guide plate 1025 can be a single plate or composed of two plates, as long as the overall shape resembles the number "8".

[0075] Understandably, the opening angle only needs to meet the transmission requirements, with 135° and 120° being preferred.

[0076] Furthermore, the cold glue applicator assembly also includes a nozzle 1021, which is tilted upwards and located at the rear end of the glue spray head 1017, i.e., the hinge wheel 1022, the glue spray head 1017 and the nozzle 1021 are arranged in sequence.

[0077] The front end of the air nozzle 1021 also has structural components such as an air pump, all of which are complete sets of equipment using existing technology. Any complete set of equipment that can ensure the operation of the air nozzle 1021 is acceptable, and will not be elaborated here.

[0078] The folding roller 1022, glue spray head 1017, and air nozzle 1021 are sequentially configured to ensure the paper falls smoothly and accurately. Because the angle of the paper's travel direction changes after the glue spray head 1017 is installed, the blowing action of the air nozzle 1021 is to counteract this change and control the paper's landing point to ensure that it does not affect subsequent work.

[0079] Furthermore, a guide rod is also provided, which is set along the direction of the conveyor belt 1023 and extends beyond the vertical projection of the conveyor belt 1023 into the paper conveying direction. The guide rod is located below the conveyor belt 1023 and is connected to the power device so that the guide rod can extend and retract along the conveying direction.

[0080] Understandably, the sheets of paper, after being coated with adhesive, fall sequentially onto the guide rod. Once a predetermined number of sheets have accumulated, the guide rod retracts, and the sheets fall to the next workstation, thus forming a booklet. For example, when printing an 18-page meeting manual, the guide rod retracts when nine sheets have accumulated, and the nine sheets fall to the next transport station. The guide rod immediately returns to its original position after retracting, and after the next nine sheets have accumulated, the guide rod retracts again, and this process repeats.

[0081] Understandably, in order to prevent the paper from falling, the length of the guide rod should extend beyond the end point of the conveyor belt 1023.

[0082] Furthermore, the paper feeding chain 1024 is located below the guide rod. The paper feeding chain 1024 moves in a circumferential direction and is equipped with a paper feeding clamp 1026, which carries the paper. This enables the paper to be conveyed to the next process.

[0083] The positional connection relationship of the above-mentioned structures is the innovation of this implementation method. As for the specific structure of the paper feeding chain 1024 and the internal structure of each structural component such as the paper feeding board, conventional technology can be used.

[0084] Furthermore, the glue sprayer 1011 is connected to an electrical wire, which in turn is connected to a controller; the glue sprayer 1011 is also connected to a glue delivery hose 1019, the other end of which is connected to a glue container. This ensures proper operation.

[0085] Furthermore, the 1017 glue spray head can continuously spray a small amount of glue, with a spray volume of 1 ml / s.

[0086] Furthermore, the air nozzle 1021 can continuously provide air pressure, and the air outlet size is 1.5mm. 2 The wind speed is 0.25-0.3 MPa.

[0087] With the above setup: 1. The size of the staples prevents the folded area from becoming too thick, allowing books to be aligned directly. 2. For confidential documents used in meetings, disassembly prevents them from being restored to their original state, avoiding the risk of leakage. 3. The elimination of staples avoids resource waste and reduces the need to remove staples when shredding paper, greatly improving shredding efficiency. 4. There is no issue of metal staples rusting during long-term storage.

[0088] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0089] It will be readily understood by those skilled in the art that this utility model includes any combination of the utility model content and specific embodiments described in the foregoing specification, as well as the various parts shown in the accompanying drawings. Due to space limitations and for the sake of brevity, not all of these combinations have been described in detail. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

[0090] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and alterations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A paper stapling-free gluing machine comprising a paper feeding table, a conveying table, a three-side cutting unit, and a collecting unit arranged in sequence, characterized in that, It also includes a folding and dispensing unit, which is located in front of the three-sided cutting unit. It includes a folding part and a dispensing part arranged vertically. The folding part includes folding wheels, conveyor belts and guide plates arranged horizontally. The gap between the two conveyor belts can clamp the paper and fold it. The dispensing part includes a cold glue applicator assembly. The cold glue applicator assembly includes a glue sprayer, a first clamping plate, a second clamping plate, a connecting column, and a first fixing plate. The first clamping plate is a V-shaped plate, consisting of a horizontal plate and an inclined fixing plate. The first fixing plate is fixedly connected to the frame. The second clamping plate is based on the first fixing plate. The connecting column connects the first clamping plate and the second clamping plate. The first clamping plate is stably fixed by the second clamping plate and the connecting column. The glue sprayer is fixed on the inclined fixing plate, and the glue spraying head at the end of the glue sprayer faces the end of the transfer table.

2. The paper stapling gluing machine according to claim 1, characterized in that, The first fixing plate is a plate-shaped structure, the second clamping plate is a plate-shaped structure, the upper surface of the second clamping plate is attached to the lower surface of the first fixing plate, and the lower surface of the second clamping plate is attached to the upper plate surface of the frame.

3. The paper stapling gluing machine according to claim 1, wherein The angle between the horizontal plate and the inclined fixing plate of the first clamping plate is 100-135°, and the inclined fixing plate is tilted in the direction of paper conveying.

4. The paper stapling gluing machine according to any one of claims 1 to 3, characterized in that, The guide plate is shaped like the number "8" and is located directly below the conveyor belt with its opening facing downwards. The resulting shoulder is used to unfold the paper, and the opening angle is 60-160°.

5. The paper staple-free perfect binding machine as described in any one of claims 1-3, characterized in that, The cold glue applicator assembly also includes an air nozzle, which is tilted upwards and located at the rear end of the glue spray head, i.e., the hinge wheel, glue spray head and air nozzle are arranged in sequence.

6. The paper staple-free perfect binding machine as described in any one of claims 1-3, characterized in that, It is also equipped with a guide rod, which is set along the direction of the conveyor belt and extends beyond the vertical projection of the conveyor belt into the paper conveying direction. The guide rod is located below the conveyor belt and is connected to the power unit so that the guide rod can extend and retract along the conveying direction.

7. The paper staple-free perfect binding machine as described in any one of claims 1-3, characterized in that, The paper feeding chain is located below the guide rod. The paper feeding chain moves in a circumferential direction and is equipped with a paper feeding clamp that carries the paper.

8. The paper staple-free perfect binding machine as described in any one of claims 1-3, characterized in that, The glue sprayer is connected to the power cord, which in turn is connected to the controller; the glue sprayer is connected to the glue delivery hose, and the other end of the hose is connected to the glue tank.

9. The paper stapling gluing machine according to any one of claims 1-3, characterized in that, The glue spray head can continuously spray a small amount of glue, with a spray volume of 1 ml / µs.

10. The paper staple-free perfect binding machine as described in any one of claims 1-3, characterized in that, The air nozzle can continuously provide air pressure, the air outlet size is 1.5 mm 2 , and the air speed is 0.25-0.3 Mpa.

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