CN220834371U - Back flush prefilter - Google Patents

Abstract

The utility model discloses a back flushing prefilter, in a back flushing state, water flows into a valve head from a water inlet, flows into a filter flask through a lower port, finally flows out through a water outlet, opens a sewage ball valve, and moves downwards under the action of water pressure to drive a whole switching assembly to move downwards to switch the filtering state into a water purification back flushing sewage discharging state, water forms a water flow vortex in a net cover due to inertia effect, the rotating water flows onto an impeller to drive the impeller to rotate anticlockwise, the impeller rotates to drive an outer framework to rotate anticlockwise together, and a hairbrush strip arranged on the outer framework scrapes and washes impurities on the outer surface of a stainless steel filter screen, so that the back flushing process of the back flushing prefilter is realized; by the arrangement, the backwashing problem of the backwashing pre-filter can be solved, and the backwashing efficiency is further improved.

Description

Back flush prefilter

Technical Field

The utility model relates to the technical field of pre-filter equipment, in particular to a back flushing pre-filter.

Background

Along with the progress of science and technology and the improvement of living standard of people, people start to have higher requirements on water and diet health in daily life. Currently, more and more people begin to use a back flush pre-filter to purify water once to filter impurities in the water.

However, the existing back flushing prefilter is easy to accumulate impurities on a back flushing passageway due to improper operation, thereby causing blockage and losing the back flushing function,

Therefore, how to solve the back flushing problem of the back flushing pre-filter and the back flushing efficiency problem is a technical problem that the skilled person needs to solve at present.

Disclosure of utility model

The utility model aims to provide a back-flushing pre-filter, which can solve the back-flushing problem of the back-flushing pre-filter and the back-flushing efficiency problem.

In order to achieve the above object, the present utility model provides the following technical solutions:

the utility model provides a back flush prefilter, includes manometer and flushing subassembly, and manometer and flushing subassembly are connected, and flushing subassembly includes:

The valve head is arranged at the bottom of the pressure gauge and connected with the pressure gauge, a water inlet and a water outlet are arranged at two ends of the valve head, and a lower port is arranged at the bottom of the valve head;

The filter bottle is connected with the lower port, and a pollution discharge ball valve is arranged at the bottom of the filter bottle;

The back flushing framework is arranged at the top end of the inside of the filter flask, a back flushing filter screen is nested in the back flushing framework, and the back flushing framework and the back flushing filter screen are both coaxially arranged with the filter flask;

The switching piece is arranged at the bottom of the back flushing framework and is coaxially arranged with the back flushing framework, a supporting piece is arranged at the periphery of the bottom of the switching piece, a back flushing spring is arranged at the periphery of the bottom of the supporting piece, a piston is arranged at the bottom of the back flushing spring and is connected with the switching piece, a net cover is arranged at the bottom of the piston and is sealed with the piston through a silica gel piece, and an impeller is arranged at the periphery of the net cover;

The water knockout drum is arranged in the circumference of the top of the switching piece, an inner framework is arranged in the water knockout drum and connected with the water knockout drum, the inner framework is nested in the stainless steel filter screen, the stainless steel filter screen is nested in the outer framework, and hairbrush strips are arranged on the outer framework along the height direction and the circumference of the stainless steel filter screen.

Preferably, the top of the switching piece is provided with a first groove, the bottom of the switching piece is provided with external threads connected with the piston, and the periphery of the first groove is provided with a silica gel sleeve.

Preferably, a first convex rib matched with the first groove is arranged on the outer side of the bottom of the back flushing framework, a second groove matched with the sealing ring is arranged on the top of the back flushing framework, and a filtering hole communicated with the back flushing filter screen is arranged between the second groove and the first convex rib.

Preferably, the water knockout drum is equipped with the protruding muscle of second all around in the outside, and the inside water knockout drum is equipped with the guide vane, and the guide vane inboard is equipped with inboard annular muscle, and inboard annular muscle inboard is equipped with protruding muscle of installation and buckle all around, and protruding muscle of installation and buckle are connected water knockout drum and inner skeleton.

Preferably, the side wall of the top of the inner framework is provided with a third groove matched with the installation convex rib, a buckle groove matched with the buckle is arranged between the third grooves, and the side wall of the bottom of the inner framework is provided with a fixed buckle connected with the net cover.

Preferably, the fourth groove connected with the impeller is formed in the periphery of the bottom of the outer framework, the third convex rib matched with the inside of the filter flask is arranged on the outer side of the top of the outer framework, and the outer wall of the outer framework is provided with a mounting groove for connecting the hairbrush strips.

Preferably, the inner wall of the top of the piston is provided with an internal thread which is matched with the external thread, the end face of the bottom of the piston is provided with a sewage outlet, and the bottom of the piston is provided with a fifth groove connected with the silica gel piece.

Preferably, the middle part of the net cover is provided with a sewage draining hole, a contact rib in point contact with the impeller is arranged above the sewage draining hole, an annular sealing groove provided with a sealing ring is arranged below the sewage draining hole, a cylindrical surface connected with a silica gel piece is arranged inside the annular sealing groove, and a clamping surface clamped with a fixing buckle is arranged inside the cylindrical surface.

Preferably, the top of the impeller is provided with a combined buckle matched with the fourth groove, and the bottom of the impeller is provided with blades.

Preferably, the filter flask is connected with the blowdown ball valve through a sealing piece.

Compared with the background art, in the back flushing prefilter provided by the utility model, in a back flushing state, water flows into the valve head from the water inlet, flows into the filter flask through the lower port, finally flows out through the water outlet, the blowdown ball valve is opened, the piston moves downwards under the action of water pressure to drive the whole switching assembly to move downwards, the filtering state is switched into a water purification back flushing blowdown state, water forms a water vortex in the net cover due to the inertia effect, the rotating water flows to the impeller to drive the impeller to rotate anticlockwise, the impeller rotates to drive the outer framework to rotate anticlockwise together, and the hairbrush strips arranged on the outer framework scrape and wash impurities on the outer surface of the stainless steel filter screen, so that the back flushing process of the back flushing prefilter is realized.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present utility model, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic view of a backwash pre-filter according to the present utility model;

FIG. 2 is a schematic view of the structure of the back flush pre-filter according to the present utility model in a filtering state;

FIG. 3 is a schematic view of the structure of the back-flushing prefilter according to the present utility model in a back-flushing condition;

FIG. 4 is a schematic diagram of a switch according to the present utility model;

FIG. 5 is a schematic structural view of a backwash framework of the present utility model;

FIG. 6 is a schematic view of the water separator of the present utility model;

FIG. 7 is a schematic view of the structure of the inner frame of the present utility model;

FIG. 8 is a schematic structural view of an exoskeleton of the present utility model;

FIG. 9 is another angular schematic view of the exoskeleton of the present utility model;

FIG. 10 is a schematic view of the position of a bristle bar according to the present utility model;

FIG. 11 is a schematic view of the piston of the present utility model;

FIG. 12 is a schematic view of the structure of the net cover of the present utility model;

FIG. 13 is another angular schematic view of the net cover of the present utility model;

Fig. 14 is a schematic structural view of an impeller of the present utility model.

In fig. 1 to 14, reference numerals include:

100-pressure gauge, 200-flushing assembly;

1-valve head, 101-water inlet, 102-water outlet, 103-lower port;

2-filtering the bottle;

3-a sewage ball valve;

4-back flushing skeleton, 4001-first ribs, 4002-second grooves and 4003-filtering holes;

5-back flushing the filter screen;

6-switching piece, 6001-first groove, 6002-external thread;

7-a support;

8-back flushing springs;

9-a piston, 9001-an internal thread, 9002-a drain outlet and 9003-a fifth groove;

10-net cover, 1001-sewage draining water hole, 1002-contact rib, 1003-annular seal groove, 1004-cylindrical surface and 1005-clamping surface;

11-a silica gel piece;

12-impeller, 1201-combined buckle and 1202-blade;

13-water separator, 1301-second convex rib, 1302-deflector, 1303-inner annular rib, 1304-mounting convex rib, 1305-buckle;

14-inner skeleton, 1401-third groove, 1402-fastening groove, 1403-fixing fastener;

15-stainless steel filter screen;

16-an outer framework, 1601-a fourth groove, 1602-a third rib and 1603-a mounting groove;

17-hairbrush strips;

18-a silica gel sleeve;

19-seal.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The utility model aims to provide a back flushing prefilter, which can solve the back flushing problem of the back flushing prefilter and improve the back flushing efficiency.

Referring to fig. 1 and 14, a back flush pre-filter includes a pressure gauge 100 and a flushing assembly 200 which are connected with each other, the flushing assembly 200 includes a valve head 1 disposed at the bottom of the pressure gauge 100, a water inlet 101 and a water outlet 102 are disposed at two ends of the valve head 1, a lower port 103 connected with a filter flask 2 is disposed at the bottom of the filter flask 2, a drain ball valve 3 is disposed at the bottom of the filter flask 2, a back flush filter screen 5 and a back flush skeleton 4 are sequentially disposed inside the top of the filter flask 2 from inside to outside, a switching member 6 coaxial with the back flush skeleton 4 is disposed at the bottom of the back flush skeleton 4, a supporting member 7 is disposed at the bottom of the switching member 6 in a circumferential direction, a back flush spring 8 is disposed at the bottom of the supporting member 7 in a circumferential direction, a piston 9 is disposed at the bottom of the back flush spring 8, the piston 9 is connected with the switching member 6, a net cover 10 is disposed at the bottom of the piston 9 and sealed with the piston 9 by a silica gel member 11, an impeller 12 is disposed at the circumferential direction of the net cover 10, a water distributor 13 is disposed at the top of the switching member 6, an inner skeleton 14, a stainless steel filter screen 15 and an outer skeleton 16 are sequentially disposed inside the filter screen 16 from inside the filter distributor 13 from inside to outside, and a brush 17 is disposed along the height direction and circumferential direction of the stainless steel filter screen 15.

Specifically, referring to fig. 2 in a normal filtration state, water flows into the valve head 1 from the water inlet 101, enters the filter flask 2 through the lower port 103, and finally is discharged from the water outlet 102, the water pressure inside the filter flask 2 is basically consistent, at this time, the elastic force of the back flush spring 8 acts on the plane of the support member 7 and the inner skeleton 14, and the support member 7, the switching member 6 and the piston 9 synchronously move, so that the support member 7 is supported by the back flush spring 8, the back flush skeleton 4 and the switching member 6 are in movable buckle fit, the back flush filter 5 and the switching member 6 mounted inside the back flush skeleton 4 move upwards together, the water flow drives the outer skeleton 16 to rotate through the water distributor 13, and the hairbrush strips 17 mounted on the outer skeleton 16 scrape the outer surface of the stainless steel filter screen 15, so that centrifugal force is formed during filtration, and impurities cannot be precipitated and adsorbed.

Referring to fig. 3 in a back flushing state, when the blowdown ball valve 3 is opened to flush and blowdown, water flows out through the piston 9, a siphon effect is achieved during blowdown, large-particle impurities are conveniently discharged, a silica gel piece 11 is designed between the net cover 10 and the piston 9 to seal gaps between the two, the piston 9 is in threaded connection with the switching piece 6, the piston 9 moves downwards under the action of water pressure, the whole switching assembly is driven to move downwards together, and the filtering state is switched to a water purification back flushing blowdown state; further, after the water is fed into the net cover 10, a water vortex is formed under the action of inertia, the rotating water flows onto the impeller 12 and drives the impeller 12 to rotate anticlockwise, and because the impeller 12 is in snap connection with the outer framework 16, the impeller 12 rotates to drive the outer framework 16 to rotate anticlockwise together, so that the hairbrush strips 17 arranged on the outer framework 16 scrape impurities on the outer surface of the stainless steel filter screen 15.

It should be noted that, the plastic part is fixedly installed inside the valve head 1, and separates water from the valve head 1 by the plastic part, so as to prevent metal ions in the valve head 1 from precipitating into the water, thereby affecting human health.

By the arrangement, dirt attached to the stainless steel filter screen 15 can be washed away by the back flushing pre-filter, so that granular dirt is not easy to accumulate in the filter flask 2, and the back flushing efficiency can be improved.

Referring to fig. 4, a first groove 6001 is provided at the top of the switching member 6, an external thread 6002 connected to the piston 9 is provided at the bottom of the switching member 6, and a silica gel sleeve 18 is installed on the periphery of the first groove 6001.

It can be appreciated that the silica gel sleeve 18 is sleeved on the switching piece 6, so that gaps among the switching piece 6, the plastic piece inside the valve head 1 and the back flushing skeleton 4 can be sealed during filtering, water flow is prevented from being filtered by the stainless steel filter screen 15, and water is directly discharged from the gap to the water outlet 102.

The external thread 6002 on the switching piece 6 is screwed with the piston, the back flushing spring 8 is fixed between the inner framework 14 and the supporting piece 7, and under the action of the water pressure and the back flushing spring 8, the switching piece 6, the supporting piece 7, the piston 9, the back flushing framework 4 and other parts can synchronously move upwards or downwards, so that the switching between the back flushing and the filtering of the purified water is realized.

In the above-mentioned case, the limit is designed between the inner frame 14 and the switching member 6, and between the inner frame 14 and the piston 9, so as to protect the internal back flushing spring 8 from damage under the condition of high water pressure, and lose the back flushing effect.

Referring to fig. 5, a first rib 4001 matched with the first groove 6001 is arranged on the outer side of the bottom of the back flushing skeleton 4, a second groove 4002 matched with a sealing ring is arranged on the top of the back flushing skeleton 4, and a filtering hole 4003 communicated with a back flushing filter screen 5 is arranged between the second groove 4002 and the first rib 4001.

In the embodiment, the back-flushing filter screen 5 arranged inside the back-flushing framework 4 is fixed between the back-flushing framework 4 and the switching piece 6, the back-flushing framework 4 and the switching piece 6 are movably buckled, namely, the first convex rib 4001 on the back-flushing framework 4 is buckled with the first groove 6001 on the switching piece 6, so that the back-flushing filter screen 5 inside the back-flushing framework 4 is conveniently taken out for cleaning,

The second groove 4002 is provided with a sealing ring for sealing a gap between the backwash skeleton 4 and the plastic part inside the valve head 1.

Further, the provision of the filter holes 4003 facilitates the flow of water into or out of the backwash filter screen 5, thereby achieving filtration and flushing.

Referring to fig. 6, a second protruding rib 1301 is disposed around the outer side of the water separator 13, a flow deflector 1302 is disposed inside the water separator 13, an inner annular rib 1303 is disposed inside the flow deflector 1302, and mounting protruding ribs 1304 and buckles 1305 are disposed around the inner side of the inner annular rib 1303, wherein the mounting protruding ribs 1304 and the buckles 1305 connect the water separator 13 with the inner skeleton 14.

It can be appreciated that the water separator 13 is connected with the filter flask 2 through the second protruding rib 1301, and is fixedly connected with the inner skeleton 14 through the mounting protruding rib 1304 and the buckle 1305, and the outer skeleton 16 is movably mounted inside, so that the water separator 13 is prevented from rotating under the action of water flow.

In the above-mentioned case, evenly distributed on the water knockout drum 13 the guide vane 1302, rivers can form the rivers swirl behind the guide vane 1302 to drive exoskeleton 16 and rotate, the brush strip 17 of installing on exoskeleton 16 will scrape the impurity on the surface of stainless steel filter screen 15, and then form centrifugal force when filtering, make impurity can not deposit and adsorb, during blowdown, the brush strip 17 can scrape the impurity on the surface of stainless steel filter screen 15, reaches the effect of back flush.

Wherein, the second protruding rib 1301 and the buckle 1305 are provided with four groups, and the installation protruding rib 1304 is provided with two groups.

Referring to fig. 7, a third groove 1401 is formed on a top side wall of the inner frame 14 and is matched with the mounting ribs 1304, a fastening groove 1402 is formed between the third grooves 1401 and is matched with a fastening 1305, and a fixing fastening 1403 is formed on a bottom side wall of the inner frame 14 and is connected with the net cover 10.

In the above embodiment, the third recess 1401 on the inner frame 14 cooperates with the mounting ribs 1304 on the water separator 13 to fix the inner frame 14, thereby preventing rotation thereof; the fastening groove 1402 is matched with a fastening 1305 on the water separator 13, the fixing fastening 1403 is matched with the net cover 10, and has a limiting function, and the net cover 10 can be fixed to rotate together under the condition that the impeller 12 cannot rotate.

Wherein, the third recess 1401 is equipped with two sets of, and buckle groove 1402 and fixed buckle 1403 all are equipped with four sets of.

Referring to fig. 8 and 9, a fourth groove 1601 connected with the impeller 12 is formed around the bottom of the outer frame 16, a third protrusion 1602 adapted to the inside of the filter flask 2 is formed on the outer side of the top of the outer frame 16, and a mounting groove 1603 connected with the brush bar 17 is formed on the outer wall of the outer frame 16.

Referring to fig. 10, it should be noted that the outer frame 16 is provided with mounting grooves 1603 uniformly distributed for mounting the brush strips 17, and when the outer frame 16 rotates, the brush strips 17 mounted on the outer frame 16 are driven to rotate together, so that impurities on the outer surface of the stainless steel filter screen 15 can be scraped.

In the above-mentioned case, be equipped with outside the outer skeleton 16 top with filter flask 2 inner wall complex third protruding muscle 1602, can prevent that outer skeleton 16 from appearing the installation slope in the installation, lead to the condition that water does not change, further, third protruding muscle 1602 surface design is the sphere, can reduce the frictional force between outer skeleton 16 and the filter flask 2 inner wall when rotating.

It will be appreciated that the evenly distributed fourth grooves 1601 on the exoskeleton 16 cooperate with the impeller 12 such that the exoskeleton 16 and the impeller 12 can rotate in unison.

Wherein, the fourth groove 1601, the third protrusion 1602 and the mounting groove 1603 are all provided with three groups.

Referring to fig. 11, an inner wall of a top of the piston 9 is provided with an inner thread 9001 engaged with the outer thread 6002, a drain port 9002 is provided on an end surface of a bottom of the piston 9, and a fifth groove 9003 connected to the silica gel member 11 is provided on the bottom of the piston 9.

In the above case, the piston 9 is screwed with the switching member 6 through the internal screw 9001 and the external screw 6002, so that the internal switching member is connected to move upward or downward synchronously, and further, the switching between the filtration and the back flushing of the purified water is performed.

It should be noted that, the drain 9002 is provided with two sets of drain 9002, and two sets of drain 9002 have siphon effect in the blowdown process, make things convenient for large granule impurity to discharge, and the gap between the lid 10 and the piston 9 can be sealed to the installation silica gel piece 11 of fifth recess 9003 department, prevents that water from flowing out from the gap between the two when blowdown.

Referring to fig. 12 and 13, a drain hole 1001 is provided in the middle of the net cover 10, a contact rib 1002 in point contact with the impeller 12 is provided above the drain hole 1001, an annular seal groove 1003 provided with a seal ring is provided below the drain hole 1001, a cylindrical surface 1004 connected with the silica gel member 11 is provided inside the annular seal groove 1003, and a clamping surface 1005 clamped with the fixing buckle 1403 is provided inside the cylindrical surface 1004.

In the above embodiment, the mesh cover 10 is provided with the drain hole 1001 to enable water to flow out through the mesh cover 10, the contact rib 1002 is used for fixing the relative position of the mesh cover 10 and the impeller, and the annular seal groove 1003 is provided with a seal ring for sealing the gap between the mesh cover 10 and the filter flask 2.

Referring to fig. 14, a combination buckle 1201 matching with a fourth groove 1601 is provided at the top of the impeller 12, and a vane 1202 is provided at the bottom of the impeller 12.

It can be appreciated that the blades 1202 are uniformly designed on the impeller 12, when water flows into the mesh cover 10 and impacts the blades 1202 on the impeller 12, the impeller 12 is driven to rotate, wherein three groups of combined buckles 1201 are arranged on the impeller 12, the three groups of combined buckles 1201 are matched with the grooves 1601 on the outer skeleton 16, and when the impeller 12 rotates, the outer skeleton 16 is driven to synchronously rotate.

On the basis of the above embodiment, the filter flask 2 is connected with the drain ball valve 3 through a sealing element 19.

The sealing member 19 is used for preventing water flow from flowing out of the gap between the filter flask 2 and the drain ball valve 3, and guaranteeing the tightness in the filter flask 2.

In conclusion, the back flushing prefilter provided by the utility model can solve the back flushing problem of the back flushing prefilter, and further improve the back flushing efficiency.

The back flush prefilter provided by the present utility model is described in detail above. The principles and embodiments of the present utility model have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present utility model and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the utility model can be made without departing from the principles of the utility model and these modifications and adaptations are intended to be within the scope of the utility model as defined in the following claims.

Claims (10)

1. A backwash pre-filter comprising a pressure gauge (100) and a flushing assembly (200), the pressure gauge (100) and the flushing assembly (200) being connected, the flushing assembly (200) comprising:

The valve head (1) is arranged at the bottom of the pressure gauge (100) and is connected with the pressure gauge (100), a water inlet (101) and a water outlet (102) are arranged at two ends of the valve head (1), and a lower port (103) is arranged at the bottom of the valve head (1);

The filter flask (2) is connected with the lower port (103), and a drain ball valve (3) is arranged at the bottom of the filter flask (2);

The back flushing framework (4) is arranged at the top end of the interior of the filter flask (2), a back flushing filter screen (5) is nested in the back flushing framework (4), and the back flushing framework (4) and the back flushing filter screen (5) are both coaxially arranged with the filter flask (2);

The switching piece (6) is arranged at the bottom of the back flushing framework (4) and is coaxially arranged with the back flushing framework (4), a supporting piece (7) is arranged on the circumference of the bottom of the switching piece (6), a back flushing spring (8) is arranged on the circumference of the bottom of the supporting piece (7), a piston (9) is arranged at the bottom of the back flushing spring (8), the piston (9) is connected with the switching piece (6), a net cover (10) is arranged at the bottom of the piston (9), the net cover (10) is sealed with the piston (9) through a silica gel piece (11), and an impeller (12) is arranged on the circumference of the net cover (10);

The water knockout drum (13) is arranged in the circumference at the top of the switching piece (6), an inner framework (14) is arranged inside the water knockout drum (13), the inner framework (14) is connected with the water knockout drum (13), the inner framework (14) is nested in the stainless steel filter screen (15), the stainless steel filter screen (15) is nested in the outer framework (16), and hairbrush strips (17) are arranged on the outer framework (16) along the height direction and the circumference of the stainless steel filter screen (15).

2. The back flush pre-filter according to claim 1, wherein a first groove (6001) is arranged at the top of the switching piece (6), an external thread (6002) connected with the piston (9) is arranged at the bottom of the switching piece (6), and a silica gel sleeve (18) is arranged at the periphery of the first groove (6001).

3. The back flush pre-filter according to claim 2, wherein a first convex rib (4001) matched with the first groove (6001) is arranged on the outer side of the bottom of the back flush framework (4), a second groove (4002) matched with a sealing ring is arranged on the top of the back flush framework (4), and a filtering hole (4003) communicated with the back flush filter screen (5) is arranged between the second groove (4002) and the first convex rib (4001).

4. The back flush pre-filter according to claim 1, wherein a second protruding rib (1301) is arranged around the outer side of the water separator (13), a guide vane (1302) is arranged inside the water separator (13), an inner annular rib (1303) is arranged on the inner side of the guide vane (1302), a mounting protruding rib (1304) and a buckle (1305) are arranged around the inner side of the inner annular rib (1303), and the mounting protruding rib (1304) and the buckle (1305) connect the water separator (13) with the inner framework (14).

5. The back flush pre-filter according to claim 4, wherein a third groove (1401) matched with the installation ribs (1304) is formed in the top side wall of the inner framework (14), a fastening groove (1402) matched with the fastening (1305) is formed between the third grooves (1401), and a fixing fastening (1403) connected with the net cover (10) is formed in the bottom side wall of the inner framework (14).

6. The back flush pre-filter according to claim 1, wherein a fourth groove (1601) connected with the impeller (12) is formed around the bottom of the outer skeleton (16), a third convex rib (1602) adapted to the inside of the filter flask (2) is formed on the outer side of the top of the outer skeleton (16), and a mounting groove (1603) connected with the brush strip (17) is formed on the outer wall of the outer skeleton (16).

7. The back flush pre-filter according to claim 2, wherein an inner wall of the top of the piston (9) is provided with an inner thread (9001) which is matched with the outer thread (6002), a drain outlet (9002) is formed in the end face of the bottom of the piston (9), and a fifth groove (9003) connected with the silica gel piece (11) is formed in the bottom of the piston (9).

8. The back flush pre-filter according to claim 5, wherein a blowdown water passing hole (1001) is formed in the middle of the net cover (10), a contact rib (1002) in point contact with the impeller (12) is arranged above the blowdown water passing hole (1001), an annular sealing groove (1003) provided with a sealing ring is arranged below the blowdown water passing hole (1001), a cylindrical surface (1004) connected with the silica gel piece (11) is arranged inside the annular sealing groove (1003), and a clamping surface (1005) clamped with the fixing buckle (1403) is arranged inside the cylindrical surface (1004).

9. The backwash pre-filter according to claim 6, wherein the impeller (12) is provided with a combination catch (1201) on top of the impeller (12) cooperating with the fourth groove (1601), and the impeller (12) is provided with blades (1202) on the bottom.

10. Backwash pre-filter according to claim 1, characterised in that the filter flask (2) is connected to the blowdown ball valve (3) by a seal (19).