Aluminum alloy profile oxidation wastewater treatment device

Abstract

The invention provides an aluminum alloy profile oxidation wastewater treatment device, and mainly relates to the technical field of wastewater treatment equipment. An aluminum alloy profile oxidation wastewater treatment device comprises a wastewater treatment pond and a base arranged at the bottom of the wastewater treatment pond, a partition plate is fixedly installed in the wastewater treatment pond and divides the wastewater treatment pond into a flocculation pond and a sedimentation pond, a water inlet pipe is fixedly installed on one side of the wastewater treatment pond and communicated with the flocculation pond, and a water outlet pipe is fixedly installed on the other side of the wastewater treatment pond. A stirring assembly is arranged in the flocculation tank, a sedimentation assembly is arranged in the sedimentation tank, a supporting plate is fixedly mounted on the top surface of the wastewater treatment tank, and the stirring assembly and the sedimentation assembly are both connected with the supporting plate. The wastewater treatment device has the beneficial effects that the wastewater treatment tank 10 is divided into the flocculation tank 103 and the sedimentation tank 104 by the partition plate 102, so that the two key treatment processes of flocculation and sedimentation are carried out in different regions, the wastewater treatment efficiency and quality are improved, and the wastewater treatment is more orderly and efficient.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment equipment technology, specifically to a wastewater treatment device for aluminum alloy profile oxidation. Background Technology

[0002] The oxidation process of aluminum alloy profiles generates a large amount of oxidation wastewater. This wastewater contains high concentrations of metal ions (such as aluminum ions), suspended solids, organic matter, and pollutants such as acids and alkalis. If discharged directly without effective treatment, it will cause serious harm to the surrounding aquatic environment, soil ecology, and the entire ecosystem. For example, it can lead to eutrophication of water bodies, soil acidification or salinization, affect the growth of aquatic organisms and crops, and even threaten human health through the food chain.

[0003] A Chinese patent with publication number CN118217706A discloses an aluminum alloy profile oxidation wastewater treatment device. To solve the problem of filter plate clogging after long-term use, a connecting rod is eccentrically hinged to the drive disc. The drive base reciprocates via the connecting rod, causing the filter plate to reciprocate. The moving filter plate reduces the pressure in the backwash chamber, thereby intensifying the filtration of wastewater in the mixing chamber. At the same time, when the pressure in the backwash chamber is too low, it indicates that the filter plate is clogged, resulting in poor filtration. The backwash blockage seat is forced out. Thus, when the filter plate moves into the backwash chamber, the backwash blockage seat first blocks the drain pipe, causing the wastewater in the backwash chamber to be squeezed and reflected out of the filter plate, thereby clearing the filter plate. Ultimately, it achieves the effect of detecting whether the filter plate is clogged and performing adaptive backwashing to clear the clog.

[0004] However, this wastewater treatment device has the following drawbacks in practical use: In existing oxidation wastewater treatment devices, wastewater is mainly filtered through filter plates. However, the impact force of the wastewater flowing through the treatment tank is relatively large, which is not conducive to the sedimentation of impurities. Furthermore, the small diameter of the through holes on the filter plates makes them more prone to clogging, making them inconvenient to use. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an aluminum alloy profile oxidation wastewater treatment device, achieved through the following technical solution: A wastewater treatment device for aluminum alloy profile oxidation includes a wastewater treatment tank and a base disposed at its bottom. A partition is fixedly installed inside the wastewater treatment tank, dividing the wastewater treatment tank into a flocculation tank and a sedimentation tank. An inlet pipe is fixedly installed on one side of the wastewater treatment tank, and the inlet pipe is connected to the flocculation tank. A stirring component is provided in the flocculation tank, and a sedimentation component is provided in the sedimentation tank. A support plate is fixedly installed on the top surface of the wastewater treatment tank, and both the stirring component and the sedimentation component are connected to the support plate.

[0006] Furthermore, the stirring assembly includes: A stirring motor is fixedly installed on one side of the top surface of the support plate; The stirring shaft is fixedly connected to the output shaft of the stirring motor. The stirring shaft vertically passes through the support plate and is connected to its bearing. The stirring shaft extends downward into the flocculation tank. The stirring blades are fixedly installed on the outer periphery of the stirring shaft, and a number of evenly distributed stirring blades are fixedly installed thereon.

[0007] Furthermore, the precipitation component includes: A flow guide plate is fixedly installed on the upper part of the sedimentation tank near the baffle, and the top of the baffle is flush with the middle of the flow guide plate. A settling plate, wherein several evenly distributed settling plates are fixedly installed between the guide plate and the settling tank, and all settling plates are inclined; A guide channel is provided on the upper part of the other side of the wastewater treatment tank. A through channel communicating with the sedimentation tank is provided on one side of the guide channel. A drain pipe is provided in front of the guide channel. A sludge scraping assembly is provided in the sedimentation tank.

[0008] Furthermore, the sludge scraping assembly includes: A sludge scraper motor is fixedly installed on the top surface of the support plate; The drive shaft is fixedly connected to the output shaft of the sludge scraper motor, and the drive shaft passes through the support plate and the sedimentation plate from top to bottom; Connecting rods are fixedly installed on both sides of the bottom of the drive shaft; Scraper blades, with several uniformly spaced internal scraper blades fixedly installed at the bottom of the connecting rod; A mud pump is fixedly installed on the top surface of the base; The sludge pump inlet is fixedly connected to one end of the sludge pump inlet, and the other end of the sludge pump inlet is fixedly connected to the center of the bottom surface of the sedimentation tank.

[0009] Furthermore, support rods are fixedly installed on both sides of the drive shaft, and the lower ends of the support rods are fixedly connected to one side of the top of the corresponding connecting rods.

[0010] Furthermore, the tilt angle of the sedimentation plate is 30°-60°.

[0011] Furthermore, extension plates are fixedly installed on the front and rear sides of the inner wall of the through groove, and an overflow plate is rotatably installed between the two extension plates. A waterproof electric telescopic rod is hinged to the bottom of the guide groove, and the movable end of the waterproof electric telescopic rod is hinged to the middle of one side of the overflow plate.

[0012] Furthermore, a number of buffer plates arranged from top to bottom are fixedly installed on one side of the sedimentation tank. The buffer plates are all inclined, and the inclination directions of two adjacent buffer plates are opposite. A baffle is fixedly installed on one side of the top surface of some of the buffer plates, and the baffles are arranged at intervals.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This device divides the wastewater treatment tank into a flocculation tank and a sedimentation tank using a partition, enabling the two key treatment processes of flocculation and sedimentation to proceed independently. In the flocculation tank, the stirring component provides sufficient stirring power to promote thorough mixing of wastewater and flocculant, accelerating the flocculation reaction and causing suspended solids and other impurities to quickly agglomerate into larger particles. Subsequently, the wastewater flows naturally into the sedimentation tank, where, under the action of the sedimentation component, the flocculated particles smoothly slide down the inclined sedimentation plate and settle, achieving efficient solid-liquid separation. This partitioned treatment method avoids mutual interference between treatment stages, making the wastewater treatment process more orderly and efficient, significantly improving the efficiency and quality of wastewater treatment, and ensuring the subsequent treatment of wastewater.

[0014] 2. The sludge scraping component can promptly clean the sludge settled at the bottom of the sedimentation tank, preventing sludge accumulation from affecting the sedimentation effect and normal equipment operation, ensuring the sedimentation performance of the sedimentation tank, and extending the service life of the equipment. The buffer plate and baffle effectively reduce the turbulence effect when wastewater enters the sedimentation tank, reducing interference with the sedimentation process. At the same time, the adjustable overflow plate structure can flexibly adjust the drainage water level according to actual treatment needs, improving the adaptability and flexibility of the device. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is the front view of the present invention; Figure 3 This is a cross-sectional structural schematic diagram of the wastewater treatment tank of the present invention; Figure 4 This is a partial structural schematic diagram of the sludge scraping component of the present invention.

[0016] The labels shown in the attached diagram: 10. Wastewater treatment tank; 101. Base; 102. Baffle plate; 103. Flocculation tank; 104. Sedimentation tank; 105. Inlet pipe; 20. Stirring assembly; 201. Stirring motor; 202. Stirring shaft; 203. Stirring blades; 30. Sedimentation assembly; 301. Flow guide plate; 302. Sedimentation plate; 40. Support plate; 50. Drainage channel; 501. Through channel; 502. Drainage pipe; 503. Extension plate; 504. Overflow plate; 505. Waterproof electric telescopic rod; 60. Sludge scraping assembly; 601. Sludge scraping motor; 602. Drive shaft; 603. Connecting rod; 604. Sludge scraper; 605. Sludge pump; 606. Sludge suction pipe; 607. Support rod; 70. Buffer plate; 701. Baffle. Detailed Implementation

[0017] The present invention will be further described in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0018] Example: A wastewater treatment device for aluminum alloy profile oxidation like Figure 1-4 As shown, an aluminum alloy profile oxidation wastewater treatment device has the following specific structure: Wastewater treatment tank 10 and base 101 disposed at its bottom. A partition 102 is fixedly installed inside the wastewater treatment tank 10, which divides the wastewater treatment tank 10 into a flocculation tank 103 and a sedimentation tank 104. The flocculation tank 103 and the sedimentation tank 104 are interconnected. An inlet pipe 105 is fixedly installed on one side of the wastewater treatment tank 10, which is interconnected with the flocculation tank 103. A stirring assembly 20 is provided inside the flocculation tank 103, and a sedimentation assembly 30 is provided inside the sedimentation tank 104. A support plate 40 is fixedly installed on the top surface of the wastewater treatment tank 10, and both the stirring assembly 20 and the sedimentation assembly 30 are connected to the support plate 40.

[0019] The working principle described above is as follows: Wastewater enters the flocculation tank 103 through the inlet pipe 105, where a flocculation reaction occurs, causing suspended solids and other impurities in the wastewater to coagulate into larger particles. Since the flocculation tank 103 is connected to the sedimentation tank 104, the wastewater after the flocculation reaction flows into the sedimentation tank 104. In the sedimentation tank 104, the flocculated particles settle under gravity, achieving solid-liquid separation. The stirring component 20 provides stirring power in the flocculation tank 103, promoting thorough mixing of the flocculant and wastewater. The sedimentation component 30 assists the sedimentation process in the sedimentation tank 104. The entire device is fixed and supported by the support plate 40. The wastewater treatment tank 10 is divided into the flocculation tank 103 and the sedimentation tank 104 by the partition 102, realizing the separate operation of the two key treatment processes of flocculation and sedimentation, improving the efficiency and quality of wastewater treatment, and making wastewater treatment more orderly and efficient.

[0020] The stirring assembly 20 includes: A stirring motor 201 is powered by alternating current and is fixedly installed on one side of the top surface of the support plate 40. The stirring shaft 202 is fixedly connected to the output shaft of the stirring motor 201. The stirring shaft 202 vertically penetrates the support plate 40 and is connected to its bearing. The stirring shaft 202 extends downward into the flocculation tank 103. Stirring blades 203: Several uniformly distributed stirring blades 203 are fixedly installed on the outer periphery of the stirring shaft 202.

[0021] The stirring motor 201 is powered by AC. After starting, the output shaft of the stirring motor 201 drives the stirring shaft 202 to rotate. The stirring shaft 202 vertically penetrates the support plate 40 and extends downward into the flocculation tank 103. Several stirring blades 203 fixedly installed on the outer periphery of the stirring shaft 202 rotate accordingly, stirring the wastewater in the flocculation tank 103, so that the wastewater and flocculant are fully mixed and the flocculation reaction is accelerated.

[0022] The precipitation component 30 includes: A guide plate 301 is fixedly installed on the upper part of the sedimentation tank 104 near the partition 102, and the top of the partition 102 is flush with the middle of the guide plate 301. A number of evenly distributed sedimentation plates 302 are fixedly installed between the guide plate 301 and the sedimentation tank 104, and the sedimentation plates 302 are all inclined. When the wastewater flows through the sedimentation plates 302, the particles naturally settle towards the sedimentation plates 302 under their own gravity and the force of the wastewater. After accumulating a certain amount, the sediment slides down the sedimentation plates 302 and falls into the bottom of the sedimentation tank 104 and collects. The wastewater treatment tank 10 is provided with a guide channel 50 on the upper part of the other side. A through channel 501 communicating with the sedimentation tank 104 is provided on one side of the guide channel 50. A drain pipe 502 is provided in front of the guide channel 50. A sludge scraping assembly 60 is provided in the sedimentation tank 104.

[0023] After wastewater flows from the flocculation tank 103 into the sedimentation tank 104, it first passes through the guide plate 301. The guide plate 301 guides the water flow, ensuring a more even distribution within the sedimentation tank 104. The guide plate 301 also buffers the water flow, reducing the turbulence effect of the wastewater in the flocculation tank 103 on the wastewater in the sedimentation tank 104. The sedimentation plate 302 is inclined between the guide plate 301 and the sedimentation tank 104. When the water flows through the sedimentation plate 302, the flocculated particles slide down the inclined sedimentation plate 302 under gravity and settle at the bottom of the sedimentation tank 104. The treated water enters the guide channel 50 through the perforation 501 on one side of the guide channel 50 and is then discharged from the drain pipe 502. The sludge scraper assembly 60 is used to clean the sludge settled at the bottom of the sedimentation tank 104.

[0024] The sludge scraping assembly 60 includes: The sludge scraper motor 601 is powered by AC and is fixedly installed on the top surface of the support plate 40. The drive shaft 602 is fixedly connected to the output shaft of the scraper motor 601. The drive shaft 602 passes through the support plate 40 and the sedimentation plate 302 from top to bottom. The drive shaft 602 is connected to the support plate 40 by a bearing, and the drive shaft 602 and the sedimentation plate 302 are clearance-fitted. Connecting rod 603, the connecting rod 603 is fixedly installed on both sides of the bottom of the drive shaft 602; Scraper 604, and several uniformly spaced scraper blades 604 are fixedly installed at the bottom of the connecting rod 603; A mud pump 605 is powered by AC power and is fixedly installed on the top surface of the base 101. The sludge suction pipe 606 is fixedly connected to one end of the sludge suction pump 605, and the other end of the sludge suction pipe 606 is fixedly connected to the center of the bottom surface of the sedimentation tank 104.

[0025] The sludge scraper motor 601 is powered by AC. After starting, the output shaft of the sludge scraper motor 601 drives the transmission shaft 602 to rotate. When the transmission shaft 602 rotates, it drives the connecting rod 603 and the scraper blade 604 to rotate. The scraper blade 604 collects the sludge settled at the bottom of the sedimentation tank 104 towards the center of the bottom of the sedimentation tank 104. Then, the sludge is pumped out of the bottom of the sedimentation tank 104 through the sludge pump 605 and the sludge is pumped out through the sludge pumping pipe 606. This cleans the sludge, prevents sludge accumulation from affecting the sedimentation effect and normal operation of the equipment, ensures the sedimentation performance of the sedimentation tank 104, extends the service life of the equipment, and also facilitates the subsequent treatment of sludge.

[0026] Support rods 607 are fixedly installed on both sides of the drive shaft 602, and the lower ends of the support rods 607 are fixedly connected to one side of the top of the corresponding connecting rods 603. The support rods 607 enhance the connection stability between the connecting rods 603 and the drive shaft 602, making the sludge scraping assembly 60 more stable and reliable during operation, reducing equipment failures caused by vibration and other reasons, and improving sludge scraping efficiency and equipment service life.

[0027] The tilt angle of the sedimentation plate 302 is 30°-60°. Controlling the tilt angle of the sedimentation plate 302 within the range of 30°-60° ensures that the sedimentation plate 302 provides sufficient sedimentation area while ensuring that the particles can slide down smoothly to settle, thereby improving sedimentation efficiency and resulting in better wastewater treatment.

[0028] Extension plates 503 are fixedly installed on the front and rear sides of the inner wall of the through channel 501, and an overflow plate 504 is rotatably installed between the two extension plates 503. A waterproof electric telescopic rod 505 is hinged to the bottom of the guide channel 50. The waterproof electric telescopic rod 505 is electrically connected to a power source, and its movable end is hinged to the middle of one side of the overflow plate 504. When the drainage level needs to be adjusted, the movable end of the waterproof electric telescopic rod 505 extends or retracts, causing the overflow plate 504 to rotate around the rotation axis between the two extension plates 503, thereby changing the angle of the overflow plate 504 and adjusting the drainage level. This allows for flexible adjustment of the drainage level according to actual treatment needs, improving the adaptability and flexibility of the device and ensuring good wastewater treatment results under different operating conditions.

[0029] A plurality of buffer plates 70, arranged sequentially from top to bottom, are fixedly installed on one side of the sedimentation tank 104. All buffer plates 70 are inclined, with adjacent buffer plates 70 inclined in opposite directions. Baffles 701 are fixedly installed on one side of the top surface of some of the buffer plates 70, and these baffles 701 are spaced apart. When wastewater flows from the flocculation tank 103 into the sedimentation tank 104, the water flow first impacts the buffer plates 70. Due to the inclination of the buffer plates 70 and the opposite inclination of adjacent buffer plates 70, the water flow changes direction multiple times between the buffer plates 70, gradually reducing the flow velocity and allowing more time for particles in the wastewater to settle. The baffles 701 fixedly installed on one side of the top surface of some of the buffer plates 70, spaced apart, further impede the water flow, enhance the buffering effect, and further reduce the turbulence effect when wastewater enters the sedimentation tank 104.

[0030] This solution also includes a controller, the location of which is set by the operator according to the actual situation during operation. The controller is used to control the electrical components used in this solution, including but not limited to sensors, motors, telescopic rods, water pumps, solenoid valves, heating wires, heat pumps, displays, computer input devices, switches, communication devices, lights, speakers, and microphones. The controller is an Intel processor, AMD processor, PLC controller, ARM processor, or microcontroller. It is used in conjunction with a motherboard, memory modules, storage media, and power supply, which is AC power or a lithium battery. When a display screen is provided, a graphics card is also included. For the operating principle of the controller, please refer to "Principles of Automatic Control," "Microcontroller Principles and Application Simulation Cases," and "Sensor Principles and Applications" published by Tsinghua University Press. Other books in this field can also be consulted. Other automation control and electrical components not mentioned are knowledge well known to those skilled in the art and will not be described in detail here.

[0031] In explaining this invention, it should be noted that the terms indicating location are used only for ease of description and understanding, and are not intended to limit the installation location of specific technical features. Other possible installation methods are not excluded.

[0032] The serial numbers assigned to components in this document, such as "first," "second," etc., are merely used to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages). In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 the invention.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wastewater treatment device for aluminum alloy profile oxidation, comprising a wastewater treatment tank (10) and a base (101) disposed at its bottom, characterized in that: A partition (102) is fixedly installed inside the wastewater treatment tank (10), which divides the wastewater treatment tank (10) into a flocculation tank (103) and a sedimentation tank (104). An inlet pipe (105) is fixedly installed on one side of the wastewater treatment tank (10), and the inlet pipe (105) is connected to the flocculation tank (103). A stirring assembly (20) is provided inside the flocculation tank (103), and a sedimentation assembly (30) is provided inside the sedimentation tank (104). A support plate (40) is fixedly installed on the top surface of the wastewater treatment tank (10), and both the stirring assembly (20) and the sedimentation assembly (30) are connected to the support plate (40).

2. The aluminum alloy profile oxidation wastewater treatment device according to claim 1, characterized in that: The stirring assembly (20) includes: A stirring motor (201) is fixedly installed on one side of the top surface of the support plate (40); A stirring shaft (202) is fixedly connected to the output shaft of the stirring motor (201). The stirring shaft (202) vertically penetrates the support plate (40) and is connected to its bearing. The stirring shaft (202) extends downward into the flocculation tank (103). Stirring blades (203): Several uniformly distributed stirring blades (203) are fixedly installed on the outer periphery of the stirring shaft (202).

3. The aluminum alloy profile oxidation wastewater treatment device according to claim 1, characterized in that: The precipitation component (30) includes: A guide plate (301) is fixedly installed on the upper part of the sedimentation tank (104) near the partition (102), and the top of the partition (102) is flush with the middle of the guide plate (301). A sedimentation plate (302) is fixedly installed between the guide plate (301) and the sedimentation tank (104). Several sedimentation plates (302) are evenly distributed and are all inclined. The wastewater treatment tank (10) is provided with a guide channel (50) on the upper part of the other side. A through channel (501) communicating with the sedimentation tank (104) is provided on one side of the guide channel (50). A drain pipe (502) is provided in front of the guide channel (50). A sludge scraping assembly (60) is provided in the sedimentation tank (104).

4. The aluminum alloy profile oxidation wastewater treatment device according to claim 3, characterized in that: The sludge scraping assembly (60) includes: Scraper motor (601), said scraper motor (601) is fixedly installed on the top surface of support plate (40); The drive shaft (602) is fixedly connected to the output shaft of the scraper motor (601). The drive shaft (602) passes through the support plate (40) and the sedimentation plate (302) from top to bottom. Connecting rod (603): Connecting rods (603) are fixedly installed on both sides of the bottom of the drive shaft (602); Scraper blade (604), and several uniformly spaced internal scraper blades (604) are fixedly installed at the bottom of the connecting rod (603). A mud pump (605) is fixedly installed on the top surface of the base (101). The mud pump (606) has a fixed connection at one end to the feed inlet of the mud pump (605), and the other end of the mud pump (606) is fixedly connected to the center of the bottom surface of the sedimentation tank (104).

5. The aluminum alloy profile oxidation wastewater treatment device according to claim 4, characterized in that: Support rods (607) are fixedly installed on both sides of the drive shaft (602), and the lower ends of the support rods (607) are fixedly connected to one side of the top of the corresponding connecting rods (603).

6. The aluminum alloy profile oxidation wastewater treatment device according to claim 3, characterized in that: The inclination angle of the sedimentation plate (302) is 30°-60°.

7. The aluminum alloy profile oxidation wastewater treatment device according to claim 3, characterized in that: Extension plates (503) are fixedly installed on the front and rear sides of the inner wall of the through groove (501), and an overflow plate (504) is rotatably installed between the two extension plates (503). A waterproof electric telescopic rod (505) is hinged to the bottom of the guide groove (50), and the movable end of the waterproof electric telescopic rod (505) is hinged to the middle of one side of the overflow plate (504).

8. The aluminum alloy profile oxidation wastewater treatment device according to claim 3, characterized in that: A number of buffer plates (70) arranged from top to bottom are fixedly installed on one side of the sedimentation tank (104). The buffer plates (70) are all inclined, and the two adjacent buffer plates (70) are inclined in opposite directions. A baffle (701) is fixedly installed on one side of the top surface of some of the buffer plates (70), and the baffles (701) are arranged at intervals.

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