Design method for staggered rake teeth assembly of rotary screen cleaner to prevent overload

Abstract

This invention provides a design method for an interlaced rake assembly of a rotary cleaning machine to prevent overload. The rake assembly consists of a blade rake followed by two end-mounted and two middle-mounted rakes. The end-mounted rakes have teeth arranged only on the two ends for 1 / 4 of their length, while the middle-mounted rakes have teeth arranged only on the middle 1 / 2 of their length. Cutting blades are installed at four locations on the blade rake, at both ends and 1 / 4 of its inward length. The projected length of the blades is greater than the length of the rake teeth. The blade installation angle that minimizes the sliding cutting force is determined through experimentation. The end-mounted and middle-mounted rakes, located behind the blade rake, lift and remove the water plants cut by the blade rake in two stages. This method reduces the weight of the lifted water plants, eliminates drag, and decreases the working load of the cleaning machine when large amounts of water plants accumulate, thus reducing cleaning power and ensuring that the cleaning process does not overload. This invention is applicable to both newly designed cleaning machines and the retrofitting of existing cleaning machines, offering good economic efficiency and strong practicality.

Description

Technical Field

[0001] This invention belongs to the technical field of pump stations and hydropower stations, and relates to a design method for a trash rack cleaning device for pump stations and hydropower stations, specifically a design method for a rotary trash rack with staggered rake teeth to prevent overload. Background Technology

[0002] For large pumping stations and hydropower stations, trash racks must be installed at the inlet to prevent contaminants from entering the pumps or turbines. However, the accumulation of large amounts of contaminants in front of the racks can create significant water level differences, resulting in severe hydraulic losses. For pumping stations, this increases pump head, reduces flow rate, and increases power output; for hydropower stations, it reduces turbine head and power output, and in severe cases, can even collapse the trash racks, affecting the safe operation of the pumps or turbines. Therefore, it is essential to install trash rack cleaning machines in front of the racks to promptly remove and salvage the contaminants, ensuring the safe and economical operation of both the pumping station and the trash racks.

[0003] Rotary trash rack cleaners consist of multiple rake tubes with evenly distributed rake teeth, a traction chain, chain track, transmission gears, a gearbox, and a traction motor. They offer advantages such as continuous operation, high cleaning efficiency, and large cleaning capacity. The cleaners are typically designed to lift the weight of debris above the water surface on the front of the trash rack. In the Yangtze River basin and areas south of it in my country, aquatic plants grow vigorously in summer and autumn. Floating plants and some submerged plants move with the water flow, easily forming large, difficult-to-separate clumps of aquatic plants. During actual cleaning, in addition to the weight of the aquatic plants being lifted, the cleaner also experiences the dragging force from the entanglement between the plants in the water and the lifted plants. The actual cleaning load of the cleaner is much greater than the traditional design load, often resulting in malfunctions such as bending and deformation of the rake tubes and teeth, chain derailment caused by rake tube deformation, and overload of the motor causing breakage of the safety transmission pin. Currently, the peak load calculation of aquatic plants only considers their own weight and does not take into account the drag force of the plants. Aquatic plants designed based on this approach have a low load capacity but high actual cleaning power, which easily leads to machine malfunctions and traction motor overload. Therefore, there is an urgent need for a design method for the rake teeth of a aquatic plant cleaning machine that has a low cleaning load and ensures safe and reliable cleaning. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a design method for staggered rake teeth and rake assemblies of a rotary trash cleaner to prevent overload, so as to solve the technical problems of rake teeth and rake tube bending and deformation, chain derailment and jamming, and motor overload in existing rotary trash cleaners due to large trash loads.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A design method for an alternating rake assembly of a rotary screen cleaner to prevent overload, wherein the rake assembly includes a blade rake, two end rakes, and a middle rake. The two ends of the blade rake, the two ends of the two end rakes, and the two ends of the middle rake are sequentially fixed to the traction chains on both sides of the screen cleaner in the rotation direction of the screen cleaner. On the front of the screen, the blade rake is positioned above the two end rakes, and the two end rakes are positioned above the middle rake. The blade rake, the two end rakes, and the middle rake are kept horizontal and parallel. At least two sets of the rake assembly are installed on the traction chain of the screen cleaner according to the required rotation length of the traction chain.

[0007] The rake tube has four blades arranged at both ends and in the middle. The two blades at both ends are arranged on the inner side of the end plate, close to the end plate. The two blades in the middle are arranged on both sides of the center section of the rake tube at 1 / 4 of the length of the rake tube. The toothed rake tube with toothed rakes at both ends has symmetrical rake teeth arranged from both ends inwards within each 1 / 4 length corresponding to the two blades at both ends of the rake tube. There are no rake teeth in the middle 1 / 2 length of the toothed rake tube corresponding to the two blades in the middle section of the rake tube. The toothed rake tube with toothed rakes in the middle section has rake teeth in the middle section within the 1 / 2 length of the toothed rake tube corresponding to the two blades in the middle section of the rake tube. There are no rake teeth in the left and right sections of the toothed rake tube within each 1 / 4 length.

[0008] The four blades are vertically welded to the rake tube with the blade edges facing upwards. The blade grinding angle α and installation angle β are determined experimentally, using the values ​​of the minimum sliding tensile force of aquatic plants on the blades. The maximum cutting force of the blades at both ends and the bending stress of the root section are calculated to verify their strength.

[0009] Furthermore, the blade installation angle β was determined experimentally. An experimental setup was constructed, and the blade was installed with the blade edge facing upwards. Experimental aquatic plants were selected. At the start of the experiment, the blade installation angle β = 0°, and the aquatic plants were placed on the blade edge. Force gauges were connected to both ends, and the force gauges were moved downwards along the experimental debris barrier. The force gauge values ​​were recorded when the aquatic plants were cut by the blade. Then, the blade installation angle was gradually increased at 2° intervals to determine the installation angle at which the cutting force was the smallest under each blade installation angle. Multiple sets of cutting experiments were conducted on the aquatic plants at the determined blade installation angle β with the smallest breaking force. The average value of the cutting force of the aquatic plants in the multiple sets of experiments was taken as the breaking force when the aquatic plants were cut, which was used for the design and calibration of the blade.

[0010] Furthermore, the blade length is L d Requires L d The projection along the length of the rake teeth is greater than the length of the rake teeth, L d The value is:

[0011]

[0012] In the formula: Lc β is the length of the rake teeth; c β is the rake tooth installation angle, which is the angle between the upper surface of the upturned rake tooth and the horizontal plane; α is the blade cutting edge installation angle; d This is the blade length coefficient, ranging from 1.5 to 2.0;

[0013] The cross-section of the blade has a triangular blade at the top with the cutting edge facing upwards, and a rectangular blade at the bottom. The blade is taller at the root and shorter at the tip, with a straight line change in the middle.

[0014] Furthermore, the blade's strength is checked, specifically the force q exerted by the blade as it rises and cuts the bottom layer of aquatic plants at its upper end, perpendicular to the blade's edge. cut q cut The magnitude is the component of the force F that breaks a waterweed along the plane of the debris barrier during the experiment, perpendicular to the blade. The blade is subjected to a uniformly distributed load along its effective cutting length for strength verification. Specifically, the waterweed slides a distance e along the blade under the force before being cut. Experiments show that when β = 30°, the diameter D of a single plant... grass aquatic plant cutting force q cut The blade slides the shortest distance e on the blade, and the blade is subjected to a perpendicular force q from a seaweed. cut for:

[0015] q cut =F·sin(β) grid -β) (2) where β grid The installation angle of the trash rack is the angle between the trash rack surface and the horizontal plane; the entire length of a blade is subjected to the vertical force of the aquatic plants.

[0016]

[0017] The root of the blade experiences the greatest bending moment, which is:

[0018]

[0019] The blade root cross-section is rectangular, with a bending section modulus W. d z and the maximum stress σ of the cross section d max They are respectively:

[0020]

[0021]

[0022] Where h is the height of the blade root section and b is the width of the blade root section, i.e., the blade thickness.

[0023] Furthermore, the design and strength verification method for the rake pipe is as follows: the rake pipe is made of round steel pipe with a length of L.g Four blades are installed on the rake tube. The two blades near the end plates at both ends exert no bending moment on the rake tube. The distance between each side of the rake tube's mid-section and the mid-section is L. g The two blades at point / 4 each have a cutting force F. cut The rake pipe experiences a bending moment, with the maximum bending moment occurring in the section between the two central blades, and the maximum bending moment value is M. p max for:

[0024] M p max =F cut ·L g / 4 (7)

[0025] The outer diameter D and inner diameter d of the circular rake tube, and its section modulus W p z With the maximum bending stress σ p max The calculation is as follows:

[0026]

[0027]

[0028] Where ε=d / D; the outer diameter and wall thickness of the round steel pipe are selected according to the load design to ensure the strength of the rake pipe (1-1);

[0029] The strength of the rake tube is checked by considering the forces on all the blades on the rake tube and the direct forces on the rake tube. Based on all the external forces on the rake tube, the bending moment is the largest in the middle of the length of the rake tube, which is the most unfavorable section. The maximum stress in this section is calculated and compared with the allowable stress of the material to check its strength.

[0030] Furthermore, the peak load F of the original single-tooth rake pipe of the cleaning machine... d Calculation method: The breaking force F in the drag force of the aquatic plants snap Extraction force F ext and the force of fall F fall The experimental method for determining the strength of the aquatic plants to be removed is as follows: the breaking force of the plants is tested experimentally, and the average breaking force F of a single plant is calculated statistically. * snap Average falling force F of a single aquatic plant * fall The pulling force F of a single aquatic plant * ext ; Statistical analysis of the proportion of aquatic plants that broke, were pulled out, or fell during actual cleanup; Weight of aquatic plants (G) and breaking force (F) on a single toothed rake pipe. snap Falling force F fall and extraction force F ext They are represented as follows:

[0031] G = ρ 水草 gSLg (10)

[0032]

[0033] In the formula: G is the weight of the aquatic plants; ρ 水草 ρ represents the density of aquatic plants; g is the acceleration due to gravity, 9.81 m / s². 2 S represents the cross-sectional area of ​​the aquatic plants accumulated on the teeth of a single rake tube; L g σ is the length of the rake tube; 水草 P represents the number of water-collecting grass roots per unit cross-section on the rake. snap P represents the percentage of broken aquatic plants among all the aquatic plants dragged on the rake tube. fall P represents the percentage of fallen aquatic plants among all the dragged aquatic plants on the rake tube. ext The percentage of aquatic plants pulled out from all the dragged aquatic plants on the toothed rake tube;

[0034] The peak load F during cleaning with a single rake tube of the original cleaning machine d Calculations show that the aquatic plants at both ends of the rake pipe are subject to external dragging, breaking, pulling out, and falling. The peak cleaning load F of a single rake pipe is calculated. d Represented as:

[0035] F d =G sinβ grid +2(F snap +F fall +F ext (12).

[0036] The beneficial effects of this invention are:

[0037] 1. This invention proposes to determine the optimal installation angle of the grass-cutting blade through experimental measurement. By installing grass-cutting blades of different lengths and installation angles on the rake tube, the cutting force when cutting typical aquatic plants is measured, and the installation angle with the minimum cutting force for a certain length of blade is determined. Under the premise of ensuring effective cutting of aquatic plants, the drag force of the blade when cutting aquatic plants is reduced, the stress on the rake tube and the blade is reduced; the drag force of aquatic plants when the toothed rake is used for cleaning is eliminated, the operating power of the cleaning machine for cutting and cleaning is reduced, and the safety and reliability are improved.

[0038] 2. The staggered rake tooth design method proposed in this invention arranges the rake teeth at both ends and in the middle of the staggered rake tubes behind the rake tube. The water plants cut by the rake tube blades are lifted and removed in two stages according to the segments. The self-weight of the water plants is small and there is no dragging force, which further reduces the working load of the cleaning machine when a large amount of water plants are gathered, reduces the power of the cleaning machine, and effectively solves the overload problem of rotary cleaning machines caused by the accumulation of water plants in the river.

[0039] 3. The optimal blade installation angle proposed in this invention, determined through experimental testing, not only ensures that the rake tube can slide and cut with a small cutting force during its upward movement, effectively cutting aquatic plants, but also ensures that when encountering thicker tree branches, woven fabrics, or other objects that cannot be cut, the uncut objects can automatically slide off the end of the blade as it moves upward, avoiding damage or entanglement to the blade and ensuring safety.

[0040] 4. This invention is applicable to both newly designed cleaning machines and the modification of existing cleaning machines. It only requires that three consecutive rake tubes be grouped together, with the top rake tube replaced by a knife rake tube, and the last two rake tubes replaced by a rake tube with staggered teeth. The design is scientific, the method is reasonable, the modification is convenient, no additional equipment is required, and it is economical and practical. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the rake assembly with staggered tooth spacing and cutting function designed in this invention;

[0042] Figure 2 This is a detailed schematic diagram of the rake and blade designed in this invention;

[0043] Figure 3 This is a schematic diagram of a rake with teeth arranged at both ends and a rake with teeth arranged in the middle section, as designed in this invention.

[0044] Figure 4 This is a schematic diagram of the rake used to collect waste in this invention. Detailed Implementation

[0045] The invention will now be further described with reference to the accompanying drawings.

[0046] Please combine Figures 1 to 4 As shown, the present invention provides a design method for an interleaved rake tooth assembly of a rotary cleaning machine to prevent overload, which is used to design the structure and parameters of the rake assembly in the rotary cleaning machine.

[0047] This design method includes the following steps:

[0048] A. Calculation of the cleaning load of a single toothed rake considering the dragging force of aquatic plants;

[0049] B. Overall design of staggered-interval rake teeth with cutting function based on minimizing cleaning load;

[0050] C. Design verification of the rake tube and blades.

[0051] Specifically,

[0052] Step A. Calculation method for the cleaning load of the toothed rake considering the drag force of aquatic plants.

[0053] The method for calculating the cleaning load of the toothed rake pipe that considers the dragging force between aquatic plants includes: based on the cross-sectional area S of the cleaning machine's toothed rake pipe, considering the actual weight G of the aquatic plants and the breaking force F of the dragging aquatic plants during cleaning. snap Extraction force F ext and the force of fall F fall Determine the cleaning load of a single toothed rake pipe;

[0054] The breaking force F of the aquatic plants snap Extraction force F ext and the force of fall F fall The calculation method is as follows: The breaking force of the aquatic plants in the cleaned water is tested experimentally, and the average breaking force F of a single aquatic plant is calculated statistically. * snap The average falling force F of a single aquatic plant * fall and the pulling force F of a single aquatic plant * ext ; Statistical analysis of the proportion of aquatic plants that break, are pulled out, or fall during actual cleaning; Weight of aquatic plants (G) and breaking force (F) on a single toothed rake pipe. snap Falling force F fall and extraction force F ext They can be represented as:

[0055] G = ρ 水草 gSL g (1)

[0056]

[0057] In the formula: G is the weight of the aquatic plants; ρ 水草 ρ represents the density of aquatic plants; g is the acceleration due to gravity, 9.81 m / s². 2 S represents the cross-sectional area of ​​the aquatic plants accumulated on the teeth of a single rake tube; L g σ is the length of the rake tube; 水草 P represents the number of water-collecting grass roots per unit cross-section on the rake. snap P represents the percentage of broken aquatic plants among all the aquatic plants dragged on the rake tube. fall P represents the percentage of fallen aquatic plants among all the dragged aquatic plants on the rake tube. ext The percentage of aquatic plants pulled out from all the dragged aquatic plants on the toothed rake tube;

[0058] The peak cleaning load F of the single rake pipe of the cleaning machine d Calculations show that the aquatic plants at both ends of the rake pipe are subject to external dragging, breaking, pulling out, and falling. The peak cleaning load F of a single rake pipe is calculated. d Represented as:

[0059] F d =G sinβ grid +2(Fsnap +F fall +F ext In equation (3), β grid The installation angle of the trash rack is the angle between the trash rack surface and the horizontal plane.

[0060] Step B. Overall design of staggered-spaced rake teeth with cutting function based on minimizing cleaning and sludge load.

[0061] The overall design of the rake group with staggered spacing based on minimum cleaning load and cutting function includes: the rake group consists of three parts: rake (1), rakes at both ends (2), and rakes in the middle section (3). The three parts, rake (1), rake (2) and rake (3), are connected to the end plates of each part of the traction chain by pins in the front of the trash rack (4) from top to bottom and kept horizontal. That is, in the direction of upward movement, the top is rake (1), the bottom is rakes at both ends (2), and the bottom is rakes in the middle section (3).

[0062] Four grass-cutting blades (1-2) are installed on both ends of the rake tube (1-1) of the rake (1) and on both sides of the symmetrical middle 1 / 2 length of the rake tube; the toothed rake (2) has rake teeth (2-2) arranged in the middle 1 / 2 length of the toothed rake tube (2-1) at both ends, and no rake teeth are arranged in the middle 1 / 2 length; the toothed rake (3) is the opposite of the toothed rake (2), with no rake teeth arranged in the middle 1 / 4 length of the toothed rake tube (3-1) at both ends, and rake teeth (3-2) arranged in the middle 1 / 2 length; the entire cleaning machine is composed of multiple sets of staggered rake teeth with cutting function as needed.

[0063] During the cleaning process, a set of toothed rakes works in concert. First, the rake (1) moves from underwater to above water along the surface of the debris barrier. During this movement, as it approaches and reaches the vicinity above the water surface, the four blades (1-2) cut the aquatic plants focused on the front of the debris barrier into three sections along the length of the rake. Then, the toothed rake (2) moves upward to scoop up the two ends of the cut aquatic plants without dragging. Finally, the toothed rake (3) moves upward to scoop up the middle section of the cut aquatic plants without dragging. When the toothed rakes (2) and (3) clean the debris, the load is only half the weight of the aquatic plants scooped up by the original rakes arranged along the entire length. In particular, the dragging force of the aquatic plants at the ends of the toothed rakes is eliminated, which greatly reduces the cleaning load.

[0064] Step C. Design verification of the rake tube and blades.

[0065] The specific contents of the design and verification of the rake tube (1-1) and blade (1-2) of the rake (1) include: determination of the optimal installation angle β of the blade cutting edge line (1-3), blade length and cross-section design, rake tube design, and strength verification of the blade and rake tube;

[0066] The blade (1-2) has an installation angle of its cutting edge line (1-3) that is the angle between the blade's cutting edge line and the horizontal plane. The blade is installed with the cutting edge facing upwards and the cutting edge line tilting downwards, which facilitates the smooth cutting of aquatic plants and ensures that debris that cannot be cut, such as woven bags and tree trunks, can slide off on its own without tangling or damaging the blade. The forces exerted by the blade when cutting several typical aquatic plants at different cutting edge line installation angles were tested, and the cutting edge line installation angle with the minimum force was determined to be the optimal cutting edge line installation angle β.

[0067] The blade (1-2) has a length of L. d The projection of this projection along the length of the rake teeth must be greater than the length of the rake teeth, and its value is:

[0068]

[0069] In the formula: L c β is the length of the rake teeth; c β is the rake tooth installation angle, i.e., the angle between the upper surface of the upturned rake tooth and the horizontal plane; β is the optimal installation angle for the blade cutting edge line; α d This is the blade length coefficient, ranging from 1.5 to 2.0;

[0070] The cross-sectional design of the blade (1-2) is as follows: the upper part is a triangular blade (1-3) with the cutting edge facing upwards, and the lower part is rectangular. The blade has a large height at the root and a small height at the end, with a straight change in the middle. The blade is also required to have a certain thickness to prevent lateral instability during cutting.

[0071] The blade (1-2) is tested for strength, and the force q it withstands when the blade rises and cuts the bottom layer of aquatic plants at the top of the blade, perpendicular to the blade edge (1-3). cut The magnitude of this force is the component of the force F that breaks a waterweed in the direction perpendicular to the blade (1-3) when pulling it upwards along the plane of the debris rack during the experiment. This force is uniformly distributed along the effective cutting length of the blade (1-3) to verify the strength of the blade (1-2). Specifically, when the blade (1-2) on the rake moves upwards and contacts the waterweed, the waterweed slides a distance e on the blade (1-3) under the action of the force before being cut. The experiment measured that when the optimal installation angle β of the blade's cutting edge line is 30°, the single diameter D... grass aquatic plant cutting force q cut Its sliding distance e on the blade (1-3) is the smallest, and the blade (1-3) is subjected to a vertical force q from a water plant. cut for:

[0072] q cut =F·sin(β) grid -β) (5) The entire length of a blade is subjected to vertical force from the aquatic plants:

[0073]

[0074] The root of the blade (1-2) experiences the greatest bending moment, which is:

[0075]

[0076] The root cross-section of the blade (1-2) is rectangular, and the bending section modulus W d z and the maximum stress σ of the cross section d max They are respectively:

[0077]

[0078]

[0079] Where h is the height of the blade root section and b is the width of the blade root section, i.e., the blade thickness.

[0080] The rake tube (1-1) is designed to be made of round steel pipe with a length of L. g Four blades (1-2) are installed on it. The two blades near the end plates at both ends exert no bending moment on the rake tube (1-1). The distance between the two sides of the rake tube's mid-section and the mid-section is L. g The two blades at point / 4 each have a cutting force F. cut The rake tube (1-1) experiences a bending moment, with the maximum bending moment occurring in the section between the two blades in the middle. Its value is:

[0081] M p max =F cut ·L g / 4 (10)

[0082] The outer diameter D and inner diameter d of the circular rake tube, and its section modulus W p z With the maximum bending stress σ p max The calculation is as follows:

[0083]

[0084]

[0085] Where ε=d / D. The outer diameter and wall thickness of the round steel pipe are selected according to the load design to ensure the strength of the rake pipe (1-1).

[0086] The strength of the rake tube (1-1) is checked by considering the forces on all the blades (1-2) on the rake tube and the direct forces on the rake tube (1-1). Based on all the external forces on the rake tube, the bending moment is the largest in the middle of the length of the rake tube, which is the most unfavorable section. The maximum stress of this section is calculated and compared with the allowable stress of the material to check its strength.

[0087] Based on the above design methods, the following is a preferred embodiment, which demonstrates a specific example of a cleaning machine rake assembly designed using this method.

[0088] In a preferred embodiment of the present invention, a certain model of rotary screen cleaner has a screen mounting angle of β. grid =75°, the original cleaning machine had 6 rake tubes N = 6, and the length of the rake tube L g =4000mm, number of rake teeth n per rake tube c =26 teeth, rake tooth length L c =185mm, spacing is d c =154mm, material is Q235-A steel, galvanized to a thickness of 160um for anti-corrosion treatment, when the thickness is 10mm, Q235-A steel plate [σ b =160MPa; the speed of the toothed rake tube movement V = 0.1m / s. The aquatic plant selected for the experiment in this embodiment of the invention is water hyacinth.

[0089] Step A: Calculation of the single-toothed rake cleaning load considering the drag force of aquatic plants:

[0090] In a preferred embodiment of the present invention, water hyacinth, which tends to aggregate and poses difficulties for intercepting and cleaning pollution in water conservancy projects, was selected as the experimental subject. The average tensile strength of a single water hyacinth was measured as follows:

[0091] Table 1. Statistical data of tensile strength test of water hyacinth

[0092]

[0093] According to statistics, the average breaking force F of a single water hyacinth stem is... * snap = 24.88N, the average falling force F of a single water hyacinth. * fall = 12.44N, the pulling force F of a single water hyacinth * ext =12.44N; In actual cleaning, the proportion of aquatic plants that are broken, pulled out, and fall is roughly the same, so take P. snap =P fall =P ext =1 / 3; The volume of sludge held by a single rake tube is based on the length L of the rake tube of the sludge cleaner. g Rake tooth length L c Installation angle β of the trash rack and cleaning machine grid It was jointly determined that the cross-sectional area of ​​the waste container is S = 0.1013 m². 2 Based on field research, the number of aquatic plant clusters σ per unit area was determined. 水草 = 6944 roots / m 2 The experiment measured the aquatic plant accumulation density as ρ. 水草 =800kg / m 3 At this time, the peak load F of the rake tube d The calculation is as follows:

[0094] G 水草 =ρ 水草 gSL g =3176.77N

[0095]

[0096] F d =G 水草 sinβ grid +2(F snap +F fall +F ext ) = 14856.04N

[0097] Step B. Overall design of staggered-spaced rake teeth with cutting function based on minimizing cleaning and sludge load.

[0098] In a preferred embodiment of the invention, based on the height of the trash rack and the rotation length of the cleaning machine, two sets of staggered rake teeth with cutting function are used. Each rake set, when rotated to the front of the trash rack, comprises three parts from top to bottom: a blade rake, rakes at both ends, and a rake in the middle section. Four blades are symmetrically arranged on the blade rake tube's central cross-section, located 1m to the left and 2m to the right of the central cross-section. The rake teeth at both ends are positioned along a 1m length from each end of the rake tube, with no rake teeth along the middle 2m length. The rake teeth in the middle section are positioned within a 2m length of the middle section of the rake tube, with no rake teeth along the middle 1m length from each end.

[0099] In a preferred embodiment of the present invention, toothed rakes are arranged at both ends with a tooth spacing d. c_side =166.7mm, with 7 rake teeth installed at each end of the rake, and the total number of rake teeth on one rake is n. c_side =14 pieces;

[0100] In a preferred embodiment of the present invention, the tooth spacing d of the intermediate rake is arranged. c_mid =166.7mm, the total number of teeth n on a single rake c_mid =13 pieces;

[0101] Step C. Design verification of the rake tube and blades.

[0102] In a preferred embodiment of the present invention, four blades are installed on the rake tube, and the installation position is as in step B. Experimental results show that the optimal installation angle for the blades is β = 30°, at which point the cutting force is minimal and the cutting effect is optimal.

[0103] In a preferred embodiment of the present invention, the blade grinding angle α = 30° was determined through testing.

[0104] In a preferred embodiment of the present invention, the blade length Ld for:

[0105]

[0106] In the formula: α d The blade length factor is set to 1.8;

[0107] The target water hyacinth, with a diameter of 5mm, is cut by a blade after a slip distance of 50mm at β = 30°. The maximum tensile force along the plane of the trash rack is measured to be F = 10.5N. Calculate the force on the blade perpendicular to the cutting edge:

[0108] q cut =F·sin(β) grid -β)=10.5×sin(75°-30°)=7.43N

[0109]

[0110] The maximum bending moment on the blade is at the root, and its maximum bending moment is calculated as follows:

[0111]

[0112] At the root of a rectangular tool, the tool has a height h = 0.1m and a thickness b = 10mm at the end. The stress calculation is checked as follows:

[0113]

[0114]

[0115] For cutting blades made of Q235-A steel, the allowable bending stress [σ] b =160MPa, which is much greater than the maximum stress at the root of the blade, so the blade can withstand the working load of the cleaning machine.

[0116] The rake tube has an outer diameter D = 114 mm, an inner diameter d = 104 mm, and a length L. g =4000mm, distance L between the middle blade and the end plate on the same side g The two blades, each with a cutting force F, have a cutting force of F = 4000 / 4mm = 1m. cut =624.12N

[0117] The action of the rake tube generates a bending moment, and the maximum bending moment of the rake tube between the two middle blades is:

[0118] M p max =F cut L g / 4=624.12×1=642.12N·m

[0119] The section modulus and maximum bending stress of the circular rake tube are:

[0120]

[0121]

[0122] Verification calculations show that the bending stress on the Q235-A steel rake pipe is much less than its allowable bending stress, meeting the strength requirements. The stress on the blade will increase to some extent when facing hard contaminants.

[0123] The maximum load of the original cleaning machine includes the weight of all the aquatic plants carried by the entire length of the rake and the pulling force of the aquatic plants on both sides, plus the weight of the aquatic plants lifted by the two rakes above the water surface, totaling 14856.04 + 2 × 3176.77 × sin75° = 20993.09 N.

[0124] Using the two sets of staggered rake teeth of this invention, first considering the simultaneous cutting of aquatic plants by the four blades of the rake, the maximum cutting force upward along the screen surface of the debris barrier is:

[0125]

[0126] At this time, there are two toothed rakes above the water surface in front of the trash rack. The cleaning load of each toothed rake is only half of the weight of the aquatic plants carried by the entire length of the rake in the original cleaning load. The cleaning load is 3176.77 / 2×sin75°=1534.26N. Therefore, the total cleaning load is 3528+3176.77×sin75°=6596.52N.

[0127] Compared to the existing toothed rake, the maximum cleaning load of the present invention's cleaning machine occurs when the rake is cutting aquatic plants, and is only 31.5% of the original load, significantly reducing the load. Considering the no-load friction power of the cleaning machine is 1.0kW, the maximum cleaning power of the original toothed rake is 20993.09×0.1 / 1000+1.0≈3.099kW, while the maximum cleaning power of the new toothed rake assembly is 6596.52×0.1 / 1000+1.0≈1.66kW, only 53.6% of the original cleaning power. This ensures that the large amount of aquatic plants accumulated before the trash rack is removed during the initial operation of the pump station without overloading, guaranteeing the reliability of the cleaning machine. However, the cleaning speed is only 1 / 3 of the original cleaning machine, requiring an extension of the cleaning time.

Claims

1. A design method for a rotary trash cleaner with staggered rake teeth to prevent overload, characterized in that: The toothed rake assembly includes a rake (1), two end toothed rakes (2), and a middle toothed rake (3). The two ends of the rake (1), the two ends of the two end toothed rakes (2), and the two ends of the middle toothed rake (3) are sequentially fixed to the traction chains on both sides of the cleaning machine according to the rotation direction of the cleaning machine. On the front of the trash rack, the rake (1) is positioned above the two end toothed rakes (2), and the two end toothed rakes (2) are positioned above the middle toothed rake (3). The rake (1), the two end toothed rakes (2), and the middle toothed rake (3) are kept horizontal and parallel. At least two sets of the toothed rake assemblies are installed on the cleaning machine traction chain according to the required rotation length of the cleaning machine traction chain. The rake (1) has four blades (1-2) arranged at both ends and in the middle of the rake tube (1-1). The two blades at both ends are arranged on the inner side of the end plate close to the end plate, and the two blades in the middle are arranged on both sides of the center section of the rake tube at 1 / 4 of the length of the rake tube. The toothed rake (2) has symmetrically arranged rake teeth in the toothed rake tube (2-1) from both ends inward, corresponding to the 1 / 4 length between the two blades at both ends of the rake tube. There are no rake teeth in the middle 1 / 2 length of the toothed rake tube (2-1) corresponding to the two blades in the middle section of the rake tube. The toothed rake (3) has rake teeth (3-2) in the middle of the toothed rake tube (3-1) corresponding to the 1 / 2 length between the two blades in the middle section of the rake tube (1-1). There are no rake teeth in the left and right sections of the toothed rake tube (3-1) at 1 / 4 of the length. The four blades (1-2) are vertically welded to the rake tube with the blade edges facing upwards. The blade grinding angle α and installation angle β are determined experimentally, using the value of the minimum sliding tensile force of aquatic plants on the blades (1-2). The maximum cutting force of the blades at both ends and the bending stress of the root section are calculated to verify their strength.

2. The design method for the staggered rake teeth assembly of a rotary cleaning machine to prevent overload as described in claim 1, characterized in that: The installation angle β of the blade (1-2) was determined through experiments. An experimental setup was constructed, and the blade was installed with the blade edge facing upwards. Experimental aquatic plants were selected. At the beginning of the experiment, the installation angle β of the blade was set to 0°. The aquatic plants were placed on the blade edge, and force gauges were connected to both ends. The force gauges were moved downwards along the experimental screen, and the force gauge values ​​were recorded when the aquatic plants were cut by the blade. Then, the installation angle of the blade was gradually increased in 2° intervals to determine the installation angle at which the cutting force was the smallest under each blade installation. The installation angle of the blade (1-2) on the rake tube (1-1) was determined. Multiple cutting experiments were conducted on the aquatic plants at the determined blade installation angle β with the smallest breaking force. The average value of the cutting force of the aquatic plants in the multiple experiments was taken as the breaking force when the aquatic plants were cut, which was used for the design and verification of the blade (1-2).

3. The design method for the staggered rake teeth assembly of a rotary cleaning machine to prevent overload as described in claim 2, characterized in that: The blade (1-2) has a length of L. d Requires L d The projection along the length of the rake teeth is greater than the length of the rake teeth, L d The value is: In the formula: L c β is the length of the rake teeth; c β is the rake tooth installation angle, which is the angle between the upper surface of the upturned rake tooth and the horizontal plane; α is the blade cutting edge installation angle; d This is the blade length coefficient, ranging from 1.5 to 2.0; The cross-section of the blade (1-2) has a triangular blade (1-3) at the top with the cutting edge facing upwards, and a rectangular shape at the bottom. The blade is taller at the root and shorter at the end, with a straight line change in the middle.

4. The design method for the staggered rake teeth assembly of a rotary cleaning machine to prevent overload as described in claim 3, characterized in that: The blade (1-2) is subjected to a strength check, where the blade withstands the force q exerted by the vertical cutting edge (1-3) when it rises and cuts through the bottom layer of aquatic plants at the top of the blade. cut q cut The magnitude is the component of the force F that breaks a water plant along the plane of the debris barrier during the experiment, perpendicular to the blade (1-3). A uniformly distributed load is applied to the blade (1-2) along the effective cutting length of the blade (1-3) to check its strength. Specifically, the water plant slides a distance e on the blade (1-3) under the action of the force before being cut. The experiment measured that when β = 30°, the diameter D of a single plant... grass aquatic plant cutting force q cut The sliding distance e on the blade (1-3) is the smallest, and the blade (1-3) is subjected to a vertical force q from a water plant. cut for: q cut =F sin(β grid -b) (2) In the formula, β grid The installation angle of the trash rack is the angle between the trash rack surface and the horizontal plane; the entire length of a blade is subjected to the vertical force of the aquatic plants. The root of the blade (1-2) experiences the greatest bending moment, which is: The root cross-section of the blade (1-2) is rectangular, and the bending section modulus W d z and the maximum stress σ of the cross section d max They are respectively: Where h is the height of the blade root section and b is the width of the blade root section, i.e., the blade thickness.

5. The design method for the staggered rake teeth assembly of a rotary cleaning machine to prevent overload as described in claim 4, characterized in that: The design and strength verification method for the rake pipe (1-1) is as follows: the rake pipe is made of round steel pipe with a length of L. g Four blades are installed on the rake tube. The two blades near the end plates at both ends exert no bending moment on the rake tube (1-1). The distance between the two sides of the mid-section of the rake tube and the mid-section is L. g The two blades at point / 4 each have a cutting force F. cut The rake pipe (1-1) experiences a bending moment, with the maximum bending moment occurring in the section between the two blades in the middle, and the maximum bending moment value is M. p max for: M p max =F cut ·L g / 4 (7) The outer diameter D and inner diameter d of the circular rake tube, and its section modulus W p z With the maximum bending stress σ p max The calculation is as follows: Where ε=d / D; the outer diameter and wall thickness of the round steel pipe are selected according to the load design to ensure the strength of the rake pipe (1-1); The strength of the rake tube (1-1) is checked. Considering the forces on all the blades (1-2) on the rake tube and the direct forces on the rake tube (1-1), the bending moment is the largest in the middle of the length of the rake tube, which is the most unfavorable section. The maximum stress of this section is calculated and compared with the allowable stress of the material to check its strength.

6. The design method for the staggered-interval rake teeth assembly of a rotary trash cleaner according to any one of claims 1 to 5 to prevent overload, characterized in that, The original single-tooth rake pipe of the cleaning machine had a peak cleaning load F. d Calculation method: The breaking force F in the drag force of the aquatic plants snap Extraction force F ext and the force of fall F fall The experimental method for determining the strength of the aquatic plants to be removed is as follows: the breaking force of the plants is tested experimentally, and the average breaking force F of a single plant is calculated statistically. * snap Average falling force F of a single aquatic plant * fall The pulling force F of a single aquatic plant * ext ; Statistical analysis of the proportion of aquatic plants that broke, were pulled out, or fell during actual cleanup; Weight of aquatic plants (G) and breaking force (F) on a single toothed rake pipe. snap Falling force F fall and extraction force F ext They are represented as follows: G=ρ 水草 gSL g (10) In the formula: G is the weight of the aquatic plants; ρ 水草 ρ represents the density of aquatic plants; g is the acceleration due to gravity, 9.81 m / s². 2 S represents the cross-sectional area of ​​the aquatic plants accumulated on the teeth of a single rake tube; L g σ is the length of the rake tube; 水草 P represents the number of water-collecting grass roots per unit cross-section on the toothed rake; snap P represents the percentage of broken aquatic plants among all the aquatic plants dragged on the rake tube. fall P represents the percentage of fallen aquatic plants among all the dragged aquatic plants on the rake tube. ext The percentage of aquatic plants pulled out from all the dragged aquatic plants on the toothed rake tube; The peak load F during cleaning with a single rake tube of the original cleaning machine d Calculations show that the aquatic plants at both ends of the rake pipe are subject to external dragging, breaking, pulling out, and falling. The peak cleaning load F of a single rake pipe is calculated. d Represented as: F d =G sinβ grid +2(F snap +F fall +F ext ) (12)。

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