Off-line filter for main gear box of wind turbine generator

Abstract

The invention discloses a wind turbine generator main gear box off-line filter which comprises a supporting plate, two mounting holes are formed in the supporting plate, the supporting plate communicates with a collecting barrel at the lower end of each mounting hole, a detachable filtering assembly is mounted in each collecting barrel, and the upper end of each filtering assembly communicates with a liquid inlet pipe; the end, away from the filtering assembly, of the liquid inlet pipe communicates with an oil outlet pipe through a first electromagnetic valve, the lower end of the collecting barrel communicates with a liquid outlet pipe, and the end, away from the collecting barrel, of the liquid outlet pipe communicates with an oil inlet pipe through a second electromagnetic valve. The collecting barrel is arranged in the protective shell, and a cooling assembly is arranged in the protective shell. When in use, the two filter assemblies are alternately used, and the self-cleaning assembly is used for cleaning the stopped filter assembly, so that the normal operation of the two filter assemblies and the cleanliness of oil are ensured, the operation and maintenance cost and the downtime can be reduced, and the cost is saved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filtering equipment, in particular to a wind turbine main gearbox offline filter. BACKGROUND

[0002] Wind power as an important renewable energy technology has been rapidly developed in the world in recent years. In the wind turbine, the main gearbox is a key component for efficient conversion of wind energy to mechanical energy. Its main function is to convert the low-speed high-torque power of the wind wheel into the high-speed low-torque power required by the generator. Since the main gearbox is operated under high load, variable working conditions and harsh outdoor environments (such as wind sand, salt spray and large temperature changes), the internal gears, bearings and other key components are prone to wear, producing metal particles, non-metallic impurities and oil sludge and other pollutants.

[0003] If these pollutants are not removed in time, they will mix into the lubricating oil, continuously aggravating the secondary wear of the parts, causing gear surface pitting, gluing, bearing peeling and other failures, and even causing early failure of the gearbox, resulting in huge downtime losses and maintenance costs. Therefore, maintaining the cleanliness of the gearbox lubricating oil is of great significance to ensure the safe, stable and long-period operation of the unit.

[0004] Currently, wind turbines generally use a lubricating oil circulation filtration system to purify the oil. Among them, the offline filter is widely used in the deep purification of lubricating oil due to its characteristics of not directly participating in the main lubrication circuit, independent operation, and not affecting the operation of the main machine. The offline filter extracts part of the lubricating oil from the gearbox oil tank, purifies it after filtration, and then reinjects it to continuously improve the cleanliness of the oil, especially for removing small particles and soft sludge that are difficult to remove by conventional online filtration.

[0005] Impurities in the lubricating oil tend to accumulate on the surface of the filter element, causing rapid increase in filtration resistance and decrease in filtration efficiency. Most existing offline filters lack effective self-cleaning mechanisms and mainly rely on regular shutdown to replace the filter element or manual cleaning, which not only increases the operation and maintenance cost and downtime, but also cannot guarantee the cleanliness of the oil during filter element clogging, which poses a risk of equipment damage. SUMMARY

[0006] The purpose of the present application is to provide a wind turbine main gearbox offline filter, which uses filter assemblies alternately, cleans the idle filter assemblies using self-cleaning assemblies, ensures the cleanliness of the oil, and reduces operation and maintenance costs and downtime.

[0007] The above technical purpose of the present application is achieved by the following technical scheme: The utility model provides a kind of wind turbine main gear box offline filter, including support plate, two installation holes that are left-right symmetrical are opened in the support plate, the lower end of each installation hole is communicated with collection cylinder, detachable filter assembly is installed in the collection cylinder, the upper end of the filter assembly is communicated with liquid inlet pipe, the end of liquid inlet pipe away from the filter assembly is communicated with oil outlet pipe by first solenoid valve, the lower end of the collection cylinder is communicated with liquid outlet pipe, the end of liquid outlet pipe away from the collection cylinder is communicated with oil inlet pipe by second solenoid valve, self-cleaning assembly is equipped in the filter assembly, and the self-cleaning assembly is used to clean the filter assembly, the lower end of the support plate is equipped with protective shell, and the collection cylinder is equipped in the protective shell, and cooling assembly is equipped in the protective shell.

[0008] By adopting the above technical scheme, the two filter assemblies can be used alternately, and the self-cleaning assembly can be used to clean the disabled filter assembly, so that the normal operation of the two filter assemblies and the cleanliness of the oil liquid can be ensured, the operation and maintenance cost and downtime can be reduced, and the cost can be saved.

[0009] The utility model further provides that the filter assembly includes a filter cylinder, a top plate, an electromagnet and a bottom plate, the top plate is detachably installed at the upper end of the installation hole, the liquid inlet pipe is communicated with the top plate, the filter cylinder is arranged at the lower middle part of the top plate, the electromagnet is arranged in the filter cylinder and is vertically installed uniformly, the bottom plate is installed at the lower end of the filter cylinder, the upper end of the electromagnet is connected to the top plate, the lower end of the electromagnet is connected to the bottom plate, the collection cylinder, the filter cylinder and the bottom plate form a liquid collecting cavity, and the liquid outlet pipe is communicated with the liquid collecting cavity.

[0010] By adopting the above technical scheme, the electromagnet is used to adsorb iron impurities, and the filter cylinder is used to filter other impurities, so that the cleanliness of the oil liquid can be ensured.

[0011] The utility model further provides that the upper end of the bottom plate is provided with a storage groove, the self-cleaning assembly includes a lifting mechanism, a scraper, a plug rod and an adsorption mechanism, the scraper is horizontally arranged in the filter cylinder, the side of the scraper is attached to the inner wall of the filter cylinder, a plurality of sliding holes are vertically arranged on the scraper, the sliding holes are sleeved on the electromagnet, the scraper is slidingly connected to the electromagnet, the lifting mechanism is installed on the bottom plate, the lifting mechanism drives the scraper to slide up and down, a liquid inlet hole is arranged in the middle part of the scraper, the plug rod is installed in the storage groove, the plug rod corresponds to the liquid inlet hole, when the scraper moves downward to the lowermost position, the plug rod is plugged in the liquid inlet hole, the storage groove and the scraper form a waste liquid cavity, and the adsorption mechanism is used to adsorb the waste liquid in the waste liquid cavity.

[0012] By adopting the technical scheme, the cleaning assembly drives the scraper to move up and down through the lifting mechanism, scrapes off the impurities outside the electromagnetic iron on the inner wall of the filter cylinder with the aid of the scraper, makes the impurities gather in the storage tank, forms waste liquid in the waste liquid cavity, and then the waste liquid is sucked away through the adsorption mechanism, so that the filter cylinder can work normally.

[0013] The lifting mechanism comprises a telescopic motor, the telescopic motor is installed at the lower end of the collecting cylinder, and the output shaft of the telescopic motor vertically penetrates the collecting cylinder and the filter cylinder and is connected to the middle part of the scraper.

[0014] By adopting the technical scheme, the scraper is conveniently lifted up and down.

[0015] The liquid inlet hole is located on the side of the output shaft of the telescopic motor.

[0016] The adsorption mechanism comprises an oil storage tank, a third electromagnetic valve, a first pipe body, a second pipe body, a third pipe body, a fourth electromagnetic valve, a pump body, a waste liquid tank and a temporary storage tank, the oil storage tank, the waste liquid tank and the temporary storage tank are all arranged in the protective shell, the oil storage tank is communicated with one side of the storage tank through the first pipe body, the third electromagnetic valve is arranged on the first pipe body, the waste liquid tank and the temporary storage tank are both communicated with the fourth electromagnetic valve through the second pipe body, the fourth electromagnetic valve is communicated with the other side of the storage tank through the third pipe body, and the pump body is arranged on the third pipe body.

[0017] By adopting the technical scheme, when the adsorption mechanism is used, the pump body is used to suck the waste liquid into the temporary storage tank, then the pump body is used to inject the waste liquid into the waste liquid, the waste liquid is repeatedly flushed back and forth for multiple times, then the waste liquid is sucked into the waste liquid tank, the third electromagnetic valve is opened, new oil is injected into the waste liquid tank, the scraper is lifted, and the filtering work is restarted.

[0018] The second electromagnetic valve is arranged at the lower middle part of the two collecting cylinders, the liquid outlet pipe is communicated with the collecting cylinder and the electromagnetic valve in an L shape, the oil inlet pipe is vertically communicated with the upper end of the second electromagnetic valve, the upper end of the oil inlet pipe penetrates the support plate, the cooling assembly comprises a plurality of metal heat dissipation plates, the heat dissipation plates are arranged in the protective shell from top to bottom, the heat dissipation plates are fixed on the liquid outlet pipe and the oil inlet pipe, and air inlets are arranged at the front end and the rear end of the protective shell.

[0019] By adopting the technical scheme, the air inlets are convenient for air inlet and outlet, the liquid outlet pipe and the oil inlet pipe on the heat dissipation plates are conveniently cooled, the temperature of the oil is reduced, and the work of the gear box is facilitated.

[0020] The first electromagnetic valve, the second electromagnetic valve and the fourth electromagnetic valve are all two-position three-way electromagnetic valves.

[0021] In summary, the present application has the following advantages: First, the present application allows two filter assemblies to be used alternately, and the disabled filter assembly is cleaned by the self-cleaning assembly, ensuring the normal operation of the two filter assemblies and the cleanliness of the oil, which can reduce the operation and maintenance cost and downtime, and save costs.

[0022] Second, the present application cleans the impurities on the filter cartridge and electromagnet by sliding the scraper downward, and then the impurities are scraped into the waste liquid chamber, and the waste liquid is sucked away by the adsorption mechanism, and the scraper can continue to filter.

[0023] Third, the adsorption mechanism in the present application can flush the waste liquid chamber through the temporary storage tank, then suck the waste liquid into the waste liquid tank, and then supplement new oil to ensure the normal operation of the gear box. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the overall structure schematic diagram in the present application; Figure 2 is the cross-sectional view in the present application; Figure 3 is the enlarged view of A in the present application; Figure 2 Figure 4 is the cross-sectional view when the scraper is used with the storage tank in the present application.

[0025] In the figure: 1, support plate; 11, mounting hole; 2, collection cylinder; 3, filter assembly; 31, filter cartridge; 32, top plate; 33, electromagnet; 34, bottom plate; 35, liquid collection chamber; 36, storage tank; 41, liquid inlet pipe; 42, first electromagnetic valve; 43, oil outlet pipe; 44, liquid outlet pipe; 45, oil inlet pipe; 46, second electromagnetic valve; 5, self-cleaning assembly; 51, lifting mechanism; 52, scraper; 521, sliding hole; 522, liquid inlet hole; 53, plug rod; 54, adsorption mechanism; 541, oil storage tank; 542, third electromagnetic valve; 543, first pipe body; 544, second pipe body; 545, third pipe body; 546, fourth electromagnetic valve; 547, pump body; 548, waste liquid tank; 549, temporary storage tank; 55, waste liquid chamber; 6, protective shell; 61, air inlet; 7, cooling assembly; 71, heat sink. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below with reference to the accompanying drawings.

[0027] ​In the description of the present application, it needs to be understood that the terms "upper", "lower", "left", "right", "front", "back", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0028] In addition, the terms "horizontal", "vertical" and the like do not mean that the components must be absolutely horizontal or vertical, but can be slightly inclined. For example, "horizontal" only means that it is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0029] In the description of the present application, it also needs to be explained that unless otherwise explicitly specified and limited, the terms "provided", "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, it can be directly connected, or indirectly connected through an intermediate medium, it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0030] Embodiment, a wind turbine main gear box offline filter, as shown in Figures 1 to 4 The support plate 1 is provided with two left-right symmetrical mounting holes 11, and a collecting cylinder 2 is communicated with the lower end of each mounting hole 11. A detachable filter assembly 3 is installed in the collecting cylinder 2. The upper end of the filter assembly 3 is communicated with a liquid inlet pipe 41. The end of the liquid inlet pipe 41 away from the filter assembly 3 is communicated with an oil outlet pipe 43 through a first electromagnetic valve 42. The lower end of the collecting cylinder 2 is communicated with a liquid outlet pipe 44. The end of the liquid outlet pipe 44 away from the collecting cylinder 2 is communicated with an oil inlet pipe 45 through a second electromagnetic valve 46. A self-cleaning assembly 5 is arranged in the filter assembly 3, which is used to clean the filter assembly 3. A protective shell 6 is arranged at the lower end of the support plate 1, and the collecting cylinder 2 is arranged in the protective shell 6. A cooling assembly 7 is arranged in the protective shell 6. The oil in the gear box is introduced into the liquid inlet pipe 41 through the oil outlet pipe 43 and the first electromagnetic valve 42, filtered by the filter assembly 3, and then discharged from the liquid outlet pipe 44 on the collecting cylinder 2 and enters the gear box through the second electromagnetic valve 46 and the oil inlet pipe 45 to filter the oil. The filter assembly 3 is used alternately, and the self-cleaning assembly 5 is used to clean the stopped filter assembly 3, so as to ensure the normal work of the filter assembly 3, without stopping the work of the device to clean the filter assembly 3, and the self-cleaning assembly 5 can ensure long-time operation without cleaning.

[0031] The filter assembly 3 comprises a filter cylinder 31, a top plate 32, electromagnets 33 and a bottom plate 34. The top plate 32 is detachably installed at the upper end of the mounting hole 11. A liquid inlet pipe 41 is connected to the top plate 32. The filter cylinder 31 is arranged at the lower end of the top plate 32. The electromagnets 33 are arranged in the filter cylinder 31. The bottom plate 34 is arranged at the lower end of the filter cylinder 31. The upper end of the electromagnet 33 is connected to the top plate 32. The lower end of the electromagnet 33 is connected to the bottom plate 34. The collecting cylinder 2, the filter cylinder 31 and the bottom plate 34 form a liquid collecting cavity 35. A liquid outlet pipe 44 is connected to the liquid collecting cavity 35. In the filter assembly 3, the electromagnets 33 are mainly used to filter metal impurities. The filter cylinder 31 is used to filter other impurities. The oil is filtered by the filter cylinder 31 and then enters the collecting cylinder 2, thereby completing the filtering work.

[0032] A storage groove 36 is arranged at the upper end of the bottom plate 34. The self-cleaning assembly 5 comprises a lifting mechanism 51, a scraper 52, a blocking rod 53 and a suction mechanism 54. The scraper 52 is horizontally arranged in the filter cylinder 31. The scraper 52 is attached to the inner wall of the filter cylinder 31. A plurality of sliding holes 521 are vertically arranged on the scraper 52. The sliding holes 521 are sleeved on the electromagnets 33. The scraper 52 is slidingly connected to the electromagnets 33. The lifting mechanism 51 is installed on the bottom plate 34. The lifting mechanism 51 drives the scraper 52 to slide up and down. A liquid inlet hole 522 is arranged at the middle part of the scraper 52. The blocking rod 53 is installed in the storage groove 36. The blocking rod 53 corresponds to the liquid inlet hole 522. When the scraper 52 moves downward to the lowermost position, the blocking rod 53 is blocked in the liquid inlet hole 522. The storage groove 36 and the scraper 52 form a waste liquid cavity 55. The suction mechanism 54 is used to suck the waste liquid in the waste liquid cavity 55. The lifting mechanism 51 comprises a telescopic motor. The telescopic motor is installed at the lower end of the collecting cylinder 2. The output shaft of the telescopic motor vertically penetrates the collecting cylinder 2 and the filter cylinder 31 and is connected to the middle part of the scraper 52. The liquid inlet hole 522 is located at the lateral side of the output shaft of the telescopic motor. The scraper 52 is driven by the telescopic motor to move up and down. When the scraper 52 moves upward to the uppermost position, the oil enters the filter cylinder 31 through the liquid inlet hole 522 to be filtered. When the scraper 52 moves downward, the impurities on the outside of the electromagnets 33 and the inside of the filter cylinder 31 are scraped downward. The excess oil is discharged from the filter cylinder 31. In this way, the waste liquid can be stored in the waste liquid cavity 55. Finally, the waste liquid is sucked away by the suction mechanism 54. Then, the scraper 52 is raised to the highest point to continue the filtering work.

[0033] The adsorption mechanism 54 comprises an oil storage tank 541, a third electromagnetic valve 542, a first pipe body 543, a second pipe body 544, a third pipe body 545, a fourth electromagnetic valve 546, a pump body 547, a waste liquid tank 548 and a temporary storage tank 549, the oil storage tank 541, the waste liquid tank 548 and the temporary storage tank 549 are arranged in the protective shell 6, the oil storage tank 541 is communicated with one side of the storage tank 36 through the first pipe body 543, the third electromagnetic valve 542 is arranged on the first pipe body 543, the waste liquid tank 548 and the temporary storage tank 549 are both communicated with the fourth electromagnetic valve 546 through the second pipe body 544, the fourth electromagnetic valve 546 is communicated with the other side of the storage tank 36 through the third pipe body 545, and the pump body 547 is arranged on the third pipe body 545. The adsorption mechanism 54 sucks the waste liquid into the temporary storage tank 549 through the pump body 547, then re-injects the waste liquid into the waste liquid chamber 55 by means of the pump body 547 for flushing, and after repeated multiple times, the waste liquid is sucked into the waste liquid chamber 55, and then new oil liquid is sucked, so that the normal work of the filter assembly 3 is ensured.

[0034] The second electromagnetic valve 46 is arranged at the lower middle part of the two collecting cylinders 2, the liquid outlet pipe 44 is communicated with the collecting cylinder 2 and the electromagnetic valve in an L shape, the oil inlet pipe 45 is vertically communicated with the upper end of the second electromagnetic valve 46, the upper end of the oil inlet pipe 45 penetrates through the support plate 1, the cooling assembly 7 comprises a plurality of metal heat dissipation plates 71, the heat dissipation plates 71 are arranged in the protective shell 6 from top to bottom, the heat dissipation plates 71 are fixed on the liquid outlet pipe 44 and the oil inlet pipe 45, and air inlets 61 are arranged at the front end and the rear end of the protective shell 6. The heat of the liquid outlet pipe 44 and the oil inlet pipe 45 is taken away by air blowing through the heat dissipation plates 71.

[0035] The first electromagnetic valve 42, the second electromagnetic valve 46 and the fourth electromagnetic valve 546 are all two-position three-way electromagnetic valves. The liquid separation treatment is facilitated.

[0036] The specific embodiment is only an explanation of the application, and is not a limitation of the application, and those skilled in the art can make modifications to the embodiment without creative contribution according to the needs after reading the specification, as long as the modifications are within the scope of the claims of the application and are protected by the patent law.

Claims

1. An off-line filter for a main gearbox of a wind turbine generator unit, comprising a support plate (1), characterized in that: Two mounting holes (11) are symmetrically arranged on the support plate (1), and a collecting cylinder (2) is communicated with the lower end of each mounting hole (11); a detachable filter assembly (3) is arranged in the collecting cylinder (2); the upper end of the filter assembly (3) is communicated with a liquid inlet pipe (41); the end of the liquid inlet pipe (41) away from the filter assembly (3) is communicated with an oil outlet pipe (43) through a first electromagnetic valve (42); the lower end of the collecting cylinder (2) is communicated with a liquid outlet pipe (44); the end of the liquid outlet pipe (44) away from the collecting cylinder (2) is communicated with an oil inlet pipe (45) through a second electromagnetic valve (46); a self-cleaning assembly (5) is arranged in the filter assembly (3) and used for cleaning the filter assembly (3); a protective shell (6) is arranged at the lower end of the support plate (1), the collecting cylinder (2) is arranged in the protective shell (6), and a cooling assembly (7) is arranged in the protective shell (6).

2. An off-line filter for a main gear box of a wind turbine generator set according to claim 1, characterized in that: The filter assembly (3) comprises a filter cylinder (31), a top plate (32), electromagnets (33) and a bottom plate (34); the top plate (32) is detachably arranged at the upper end of the mounting hole (11); the liquid inlet pipe (41) is communicated with the top plate (32); the filter cylinder (31) is arranged at the lower end of the top plate (32); the electromagnets (33) are vertically arranged in the filter cylinder (31); the bottom plate (34) is arranged at the lower end of the filter cylinder (31); the upper end of the electromagnet (33) is connected to the top plate (32); the lower end of the electromagnet (33) is connected to the bottom plate (34); the collecting cylinder (2), the filter cylinder (31) and the bottom plate (34) form a liquid collecting cavity (35); and the liquid outlet pipe (44) is communicated with the liquid collecting cavity (35).

3. An off-line filter for a main gear box of a wind turbine generator set according to claim 2, characterized in that: A storage groove (36) is arranged at the upper end of the bottom plate (34); the self-cleaning assembly (5) comprises a lifting mechanism (51), a scraper (52), a blocking rod (53) and a suction mechanism (54); the scraper (52) is horizontally arranged in the filter cylinder (31); the circumferential side of the scraper (52) is attached to the inner wall of the filter cylinder (31); a plurality of sliding holes (521) are vertically arranged on the scraper (52); the sliding holes (521) are sleeved on the electromagnets (33); the scraper (52) is slidingly connected to the electromagnets (33); the lifting mechanism (51) is arranged on the bottom plate (34); the lifting mechanism (51) drives the scraper (52) to slide up and down; a liquid inlet hole (522) is arranged in the middle of the scraper (52); the blocking rod (53) is arranged in the storage groove (36); the blocking rod (53) corresponds to the liquid inlet hole (522); when the scraper (52) moves downward to the lowermost position, the blocking rod (53) is blocked in the liquid inlet hole (522); the storage groove (36) and the scraper (52) form a waste liquid cavity (55); and the suction mechanism (54) is used for sucking waste liquid in the waste liquid cavity (55).

4. An off-line filter for a main gear box of a wind turbine generator set according to claim 3, characterized in that: The lifting mechanism (51) comprises a telescopic motor installed at the lower end of the collecting cylinder (2), and the output shaft of the telescopic motor vertically penetrates the collecting cylinder (2) and the filter cylinder (31) and is connected to the middle part of the scraper (52).

5. An off-line filter for a main gear box of a wind turbine generator set according to claim 4, characterized in that: The liquid inlet hole (522) is located at the circumferential side of the output shaft of the telescopic motor.

6. An off-line filter for a main gear box of a wind turbine generator set according to claim 5, characterized in that: The adsorption mechanism (54) comprises an oil storage tank (541), a third electromagnetic valve (542), a first pipe body (543), a second pipe body (544), a third pipe body (545), a fourth electromagnetic valve (546), a pump body (547), a waste liquid tank (548) and a temporary storage tank (549), the oil storage tank (541), the waste liquid tank (548) and the temporary storage tank (549) are all arranged in the protective shell (6), the oil storage tank (541) is communicated with one side of the storage groove (36) through the first pipe body (543), the third electromagnetic valve (542) is arranged on the first pipe body (543), the waste liquid tank (548) and the temporary storage tank (549) are both communicated with the fourth electromagnetic valve (546) through the second pipe body (544), the fourth electromagnetic valve (546) is communicated with the other side of the storage groove (36) through the third pipe body (545), and the pump body (547) is arranged on the third pipe body (545).

7. An off-line filter for a main gear box of a wind turbine generator set according to claim 6, characterized in that: The second electromagnetic valve (46) is arranged at the lower middle part of the two collecting cylinders (2), the liquid outlet pipe (44) is communicated with the collecting cylinder (2) and the electromagnetic valve in an L shape, the oil inlet pipe (45) is vertically communicated with the upper end of the second electromagnetic valve (46), the upper end of the oil inlet pipe (45) penetrates the support plate (1), the cooling assembly (7) comprises a plurality of metal heat dissipation plates (71), the heat dissipation plates (71) are arranged in the protective shell (6) from top to bottom, the heat dissipation plates (71) are fixed on the liquid outlet pipe (44) and the oil inlet pipe (45), and air inlets (61) are arranged at the front end and the rear end of the protective shell (6).

8. An off-line filter for a main gear box of a wind turbine generator set according to claim 7, characterized in that: The first electromagnetic valve (42), the second electromagnetic valve (46) and the fourth electromagnetic valve (546) are all two-position three-way electromagnetic valves.

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