CN105987207A - Pressure relief type backflow prevention device with tiny resistance - Google Patents

Abstract

The invention discloses a pressure relief type backflow prevention device with tiny resistance. A water inlet check valve and a water outlet check valve are horizontally arranged in a middle chamber between a valve body and an upper valve cover, the axis of the water inlet check valve and the axis of the water outlet check valve are the same as the axis of the water inlet of the valve body and the axis of the water outlet of the valve body. A drain valve is arranged on the lower portion of the valve body, and the axis of the drain valve vertically intersects with the axis of the water inlet of the valve body and the axis of the water outlet of the valve body. A plurality of drain holes (I) are formed in the partition on the lower portion of the valve body and communicate with a drain chamber. The water inlet check valve and the water outlet check valve are each provided with a permanent magnet and an armature. The drain valve is provided with a membrane piece, and the outer edge of the membrane piece is tightly pressed between the lower portion of the valve body and a lower valve cover. Through holes used for introducing water inlet pressure into the lower chamber of the membrane piece are formed. The portion, connected with the lower valve cover, of the lower end of the valve body is provided with a drain apparatus function detection device through which the upper chamber and the lower chamber of the membrane piece can communicate. According to the pressure relief type backflow prevention device with tiny resistance, various comprehensive measures which facilitate flow resistance reduction are adopted, flow resistance loss can be greatly reduced, and reliable backflow prevention performance is achieved.

Description

Micro-resistance pressure reduction type backflow preventer

Technical field

The present invention relates to a kind of valve, particularly relate to a kind of pressure reduction type backflow preventer.

Background technology

Backflow preventer, also known as dirt stream isolating valve, be one strictly prevent Drinking Water pipeline occur backflow time polluted source Safety features, it is possible to be applied to other tubing not allowing medium to flow backwards.

Backflow preventer pattern is more, and pressure reduction type backflow preventer is high due to function admirable, safety, is accepted by industry, And promoted.Its typical construction represents in Chinese patent notification number CN201547347C, by clack box, water inlet non-return Valve, go out Water Check Valve and drain valve composition.But in use finding, this class formation has the disadvantage that

1. drag losses during medium circulation is relatively big, and main cause is for making drain valve reliably close, it is necessary to make beating into water check-valves Open the pressure closing presure (closing presure >=0.014MPa of national regulations drain valve) more than drain valve, such inlet check valve Open pressure and must be designed to relatively big (national regulations inlet check valve opens pressure >=0.02MPa)；Secondly, for making outlet non-return Valve seals reliable, and opening pressure should not too small (national regulations goes out Water Check Valve and opens pressure >=0.007Ma)；Moreover, in valve pocket Area of passage and runner design everywhere are unreasonable, and running through the most up and down in the valve pocket of above-mentioned patent has the valve rod of a drain valve, Cause local resistance loss bigger.After tested, under conditions of the design of each spring meets GB, when velocity of medium is 3m/s, Flow resistance loss reaches 0.07～0.10MPa, and this not only causes a large amount of energy consumption, and at water supply pressure relatively low (such as 0.16MPa) Area cannot use at all.

In order to reduce flow resistance, applicant once have developed the most a backflow preventer, Chinese patent notification number CN204164434, In water-in and water-out check-valves, it is provided with permanent magnet and armature, after valve is opened, counteracts partial spring power；And change Drain valve structure, eliminates the montant in the middle of valve pocket.After tested, when velocity of medium is 3m/s, flow resistance loss about 0.4MPa, Having had and declined to a great extent, water supply department proposes to widely be promoted in the relatively low area of pressure of supply water while affirmative, uncommon Prestige can reduce further.

2. the critical component during drain valve is backflow preventer, it is desirable to reach at intake pressure P1 and intermediate cavity pressure P2 pressure reduction During setting value (national regulations is 0.014MPa), can promptly open draining, because when intake pressure is higher than intermediate cavity pressure Just carry out draining, therefore can definitely prevent medium from flowing backwards and occur.In recent years, the various structure of drain valve constantly occurs, but practice card Bright, have can not regulate because of spring force, causes when using after with the passing of time elastic force diminishes, causes discharge pressure to reduce, to safety band Carry out hidden danger；Have because of diaphragm size, spring force and port size three's mismate, cause sealing force inadequate, cause and leak； Have because of in runner some position flow section area less, cause displacement little；Have because of in valve pocket deposition dirt can not be square Just cleaning in time, causes the kinematic pair such as guiding valve and valve pocket to be consolidated by dirt, causes drain valve not open；More have very Person, in use for some time, completely loses drain function.

3. there is no water trap function detection device, owing to water trap is made up of some parts, use and break down the most unavoidably day, Reduce such as spring rate or the kinematic pair such as fracture, guiding valve or valve rod is by dirt consolidation, flap and sealing member (material one be rubber) Adhesion etc. occurs, and in use when these faults occur unknown, once occur sewage to flow backwards and just carry out dissembling inspection, One there occurs that large amount of sewage flows backwards.

Summary of the invention

The present invention is that the one micro-resistance pressure-reducing refluence designed for solving the above-mentioned technical deficiency of backflow preventer prevents Device.

The above-mentioned technical problem of the present invention is mainly addressed by following technical proposals:

A kind of micro-resistance pressure reduction type backflow preventer, has valve body, valve gap, water inlet check-valves, goes out Water Check Valve and drain valve；

Water inlet check-valves and go out Water Check Valve and be arranged horizontally in the intermediate cavity between valve body and bonnet, its axis enters with valve body Outlet axis is consistent；

Drain valve is arranged between valve body lower end face and bottom flange, and the axis that its axis is imported and exported with valve body intersects vertically, valve body Some osculums one are had to connect with drain chamber on lower quartered；

It is characterized in that: described water inlet check-valves is each provided with permanent magnet and armature with going out Water Check Valve, also has above employing The circlip of opening, to facilitate dismounting maintenance；

Described drain valve is provided with the guiding valve being connected with diaphragm, is equipped with piston in the endoporus of guiding valve, and the central shaft upper surface of piston exists Under the effect of spring, contact with the boss lower surface of pressing plate all the time；

Valve body lower end is provided with the water trap function detection device that the upper and lower chamber of diaphragm can be made to connect with bottom flange connecting portion.

Technical scheme can also be the most perfect:

As preferably, described bottom flange include casting all-in-one-piece lower flange, middle part have sinking cylinder, in position go up some Projection, described projection includes projection one and projection two；In the cylinder endoporus of bottom flange, close-fitting has sleeve, sliding in the endoporus of sleeve Being furnished with guiding valve, be equipped with piston in the endoporus of guiding valve, the upper of piston is positioned by the internal shoulder on guiding valve top；Also set on bottom flange There is the through hole that intake pressure is introduced diaphragm cavity of resorption.

As preferably, the upper end cylindrical of described guiding valve has been got on the bus screw thread, and the inner ring of diaphragm is pressed on by clamp nut and packing ring On the upper surface of the outer convex shoulder of guiding valve, in the case of not water flowing, outward flange and the inner ring of diaphragm are located substantially in same level.

As preferably, the top of described guiding valve is provided with annular sword limit, forms drain valve with the sealing gasket being arranged on body base Valve port, the Assurance of Size of valve port is in the case of normal water supply, and the ratio pressure about 0.6MPa of the two, to ensure the reliability sealed.

As preferably, described piston is made up of the piston ring outside central shaft, central shaft and two straight dowels, muscle Between have two mounting holes, the upper surface of central shaft contacts with the boss lower surface of pressing plate the most all the time.

As preferably, the lower end of described piston is provided with spring, and spring force can be by below with the Adjusting bolt Adjusting screw tune of osculum two Joint.

As preferably, described intake pressure introduces the through hole of diaphragm cavity of resorption and is: be drilled with and film on the outer peripheral face of bottom flange projection one The radial direction small through hole one of sheet cavity of resorption connection, blocks outer end with steel ball after brill；Bottom flange bottom surface is drilled with aperture one, with radial direction small through hole one Intersect vertically, and be positioned at aperture two that valve body lower end face connects with intake antrum on same centrage；By on valve body with water inlet The inclined hole of chamber connection, the corresponding through hole on aperture two, diaphragm and aperture one, radially small through hole one, intake pressure is incorporated into The cavity of resorption of diaphragm.

As preferably, the lower flange upper surface of bottom flange has boss, boss to be provided with to get rid of easily and accumulate in diaphragm cavity of resorption The blowdown bolt of middle dirt.

As preferably, water trap function detection device is arranged on the projection two of bottom flange and clamping diaphragm position, valve body lower end face In intercommunicating pore, including valve rod, O-ring seals three and fastening screw nut；Described valve rod is stairstepping, and epimere is relatively thin, and top processes Having frustum, stage casing is used as guiding when it moves up and down, and prevents medium from leaking with O-ring seals three, and hypomere is machined with outer spiral shell Stricture of vagina, there is fastening screw nut 26 end in order to prevent valve rod from loosening after shutting valve port.

As preferably, described intercommunicating pore includes dividing on the appropriate location of valve body lower end outer peripheral face and bottom flange projection two outer peripheral face Not being drilled with radially small through hole two and radially small through hole three, after brill, outer end all blocks with steel ball, and the axis of holes is at same vertical plane On；Being drilled with aperture three on the lower surface of valve body, intersect vertically with radial direction small through hole two, the end of aperture three is machined with and valve rod end The conical surface that portion's frustum coordinates, the two forms valve port；The hole coordinated with valve rod, described hole it is machined with on the end face of bottom flange projection two Intersecting vertically with radial direction small through hole three, communicate and concentric with aperture three, diaphragm outward flange is provided with corresponding aperture, concentric with hole, The downside in hole is machined with the female thread coordinated with valve rod external screw thread.

Beneficial effects of the present invention:

1, take: two check-valves are provided with permanent magnet and armature, so when valve port is fully open, nearly one can be offset The spring pressure of half；Change drain valve structure, intermediate cavity no longer has the montant running through upper and lower；When medium flows in valve pocket, Each flow section area is spacious, and all contacts site with each part or leave position, all has 30 °～60 ° on part Chamfering or fillet, advantageously reduce the aggregate measures of flow resistance reducing local eddy currents loss etc..Survey through model machine, work as velocity of medium During for 3m/s, flow resistance loss about 0.32MPa；When flow velocity is 2m/s, flow resistance loss about 0.025MPa, has been water supply department Accreditation, can be used for the relatively low area of pressure of supply water.

2, the spring force of drain valve can accurately be adjusted to the discharge pressure of Standard, and anti-backflow safety is high, and sealing Good, drainability is big, reliable operation；

3, the function that structure of the detecting device is simple, easy to detect, can detect drain valve at any time is the most normal, in order to find in time Problem repairs or replaces.

Accompanying drawing explanation

Accompanying drawing 1 is a kind of structural representation of the present invention；

Accompanying drawing 2 is drain valve structure enlarged drawing in Fig. 1；

Accompanying drawing 3 is water trap function amplification figure in Fig. 1；

Description of reference numerals:

1, valve body, 2, bonnet, 3, water inlet check-valves, 4, go out Water Check Valve, 5, drain valve, 6, circlip, 7, ball valve, 8, O-ring seals one, 9, steel ball, 10, diaphragm, 11, bottom flange, 12, sleeve, 13, spring, 14, O shape seals Circle two, 15, Adjusting bolt Adjusting screw, 16, guiding valve, 17, piston, 18, blowdown bolt, 19, clamp nut, 20, packing ring, 21, Pressing plate, 22, sealing gasket, 23, valve rod, 24, O-ring seals three, 25, fastening screw nut；

A, inclined hole, b, aperture two, c, aperture one, d, radially small through hole one, e, osculum one, f, mounting hole, g, osculum two, H, radially small through hole two, j, radially small through hole three, m, hole, L, aperture three,；

D1, projection one, D2, projection two, H1, intake antrum, H2, intermediate cavity, H3, water chamber, H4, drain chamber, P1, Intake pressure, P2, intermediate cavity pressure, P3, discharge pressure.

Detailed description of the invention

Below by embodiment, and combine accompanying drawing, technical scheme is described in further detail.

Embodiment:

Micro-resistance pressure reduction type backflow preventer as shown in Figure 1, has valve body 1, bonnet, 2, water inlet check-valves 3, goes out Water Check Valve 4 and drain valve 5, water inlet check-valves 3 and go out intermediate cavity H2 that Water Check Valve 4 is arranged horizontally between valve body 1 and bonnet, 2 In, its axis is consistent with valve body intake-outlet axis, and drain valve 5 is arranged between valve body lower end face and bottom flange 11, its axis The axis imported and exported with valve body intersects vertically, and 1 time quartered of valve body has some osculum one e connect with drain chamber H4, enters Water Check Valve 3 is each provided with permanent magnet and armature with going out Water Check Valve 4, and uses top to have the circlip 6 of opening, right They carry out mounting or dismounting rapidly, need not be unloaded from pipeline by complete machine during maintenance, only need to pull down bonnet, 2, take out water-in and water-out Check-valves 3,4 is just；Three ball valves 7 above valve body 1 and bonnet, 2 are respectively in order to measure intake antrum H1, centre Pressure gauge is connected when chamber H2 and water chamber H3 hydraulic pressure；Valve body lower end is provided with bottom flange 11 connecting portion and diaphragm can be made upper and lower The water trap function detection device of chamber connection；The lower flange upper surface of bottom flange have boss, boss be provided with can get rid of easily long-pending There is the dirt in diaphragm cavity of resorption, prevent the blowdown bolt 18 that guiding valve 16 and sleeve 12 are consolidated by dirt.

Below the part-structure of the present invention is elaborated:

Drain valve (as shown in Figure 2)

Drain valve is by O-ring seals 1, steel ball 9, diaphragm 10, bottom flange 11, sleeve 12, spring 13, O-ring seals two 14, Adjusting bolt Adjusting screw 15, guiding valve 16, piston 17, blowdown bolt 18, clamp nut 19, packing ring 20, pressing plate 21, sealing Pad 22 compositions such as part such as grade.Bottom flange 11 is by lower flange, cylinder and two projection one D1, projection two D2 in position gone up Composition, four are cast into one, and inner surface is stepped through hole, sleeve connect at plane the most prominent；Bottom flange 11 passes through Some screws are fixed on the lower surface of valve body 1, and the outward flange of diaphragm 10 is pressed in therebetween；The periphery of projection one D1 Being drilled with radially small through hole d on face, blocked outer end with steel ball 9 after brill, bottom surface is drilled with aperture one c, hangs down with radial direction small through hole one d Straight crossing, and with aperture two b on valve body 1 on same centrage；By the inclined hole a on valve body 1, aperture two b, diaphragm Corresponding aperture on 10 and aperture one c, radially small through hole one d, be incorporated into the cavity of resorption of diaphragm 10, O shape by intake pressure P1 Sealing ring 1 is used for preventing medium from leaking；Projection two D2 is provided with water trap function detection device；Lower flange upper surface convex Platform is provided with a blowdown bolt 18, can pull down easily, utilizes the press water in valve to get rid of and accumulates in diaphragm 10 cavity of resorption Dirt, be consolidated by dirt with antiskid valve 16 and sleeve 12；The endoporus of cylinder has been press-fitted stainless sleeve 12, The endoporus of sleeve is equipped with guiding valve 16, between the two, is provided with O-ring seals 2 14, in case medium leaks.

The top of guiding valve 16 is provided with annular sword limit, and with the valve port that sealing gasket 22 forms drain valve, the Assurance of Size of valve port is just In the case of often supplying water, the ratio pressure of the two is about 0.6MPa, to ensure the reliability sealed；Sealing gasket 22 is by screw, pressure Plate 21 is fixed in the groove below 1 time partition wall of valve body；The upper end cylindrical of guiding valve 16 has been got on the bus screw thread, and is cased with diaphragm 10； The inner ring of diaphragm 10 is pressed on the upper surface of the outer convex shoulder of guiding valve 16, in the feelings of not water flowing by clamp nut 19 and packing ring 20 Under condition, outward flange and the inner ring of diaphragm 10 are located substantially in same level；The endoporus of guiding valve 16 is equipped with piston 17, The upper of piston 17 is positioned by the internal shoulder on guiding valve top；Piston 17 is by central shaft, outer piston ring and two straight connections Muscle forms, and has two mounting hole f between muscle；The lower end of piston 17 is provided with spring 13, spring force can by below with draining The Adjusting bolt Adjusting screw 15 of hole two g regulates；Under spring force, the upper surface of the central shaft of piston 17 is convex with pressing plate 19 all the time The lower surface contact of platform, guiding valve 16 is subject to 13 1 downward thrusts of spring all the time simultaneously, therefore in the case of not water flowing, The lower surface of the outer convex shoulder of guiding valve 16 is pressed on the upper surface of sleeve 12, and now valve port V opens completely, and has opening of setting Degree；Pacifying spring-loaded space in the endoporus of guiding valve 16 is drain chamber H4.

Operation principle (as shown in Figure 1), for the location drawing of each parts in valve in the case of not supplying water shown in figure, now enters Water Check Valve 3, going out Water Check Valve 4 and close, drain valve 5 is opened, and intermediate cavity H2 is by several rows on 1 time quartered of valve body Water hole one e communicates with diaphragm epicoele and drain chamber H4 of drain valve.After water supply, medium initially enters intake antrum H1, and passes through Corresponding aperture and aperture one c, radially small through hole one d on inclined hole a, aperture two b, diaphragm 10 edge enter drain valve diaphragm The cavity of resorption of 10.Along with the rising of intake antrum H1 hydraulic pressure, reach drain valve spring 13 when acting on the pressure below diaphragm 10 When setting pressure, band movable pulley 16 moves upward, and valve port V closes, and now intermediate cavity H2 is cut off with drain chamber H4.Draining After valve cuts out, P1 continues to rise, until being opened by water inlet check-valves, then will go out Water Check Valve 4 and opening, and downstream supplying water.

In the case of normal water supply, if intake pressure P1 declines suddenly, during declining, when (P1-P2) is less than setting During definite value, drain valve is opened under the promotion of spring 13, and the medium in intermediate cavity H2 is through osculum one e, valve port V, kidney-shaped Hole f, drain chamber H4 and osculum two g discharge, and intermediate cavity H2 hydraulic pressure P2 reduces immediately, when (P1-P2) recovers extremely During setting value, drain valve is closed again, recovers normal water supply.

When import hydraulic pressure P1 falls too low, or being zero, even during negative value, drain valve 5 is opened rapidly, by intermediate cavity H2 In water emptying, simultaneously air enter intermediate cavity H2, define air partition, it is therefore prevented that siphon flow backwards generation, even if now Water inlet check valve seal inefficacy (such as being blocked by foreign material) also will not be flow backwards.

In the case of normal water supply, if owing to the reasons such as water hammer cause discharge pressure significantly to raise, now, if water outlet non-return Valve 4 good seal, then the pressure of intermediate cavity H2 can raise, if seal failure, then the pressure P2 of intermediate cavity H2 is along with liter Height, when (P1-P2) reaches drain valve 5 closing presure, drain valve 5 is opened, and air enters intermediate cavity H2 simultaneously, is formed Air partition.

From the above analysis, under the present invention the most sharp operating mode in office, though the sealing of two check-valves all destroyeds, can It is effectively prevented the danger at refluence medium pollution water source.

Water trap function detection device (as shown in Figure 3):

This device is arranged on projection 2 and the position of valve body 1 lower surface clamping diaphragm 10 of bottom flange 11, valve rod 23, O shape seal Enclose the part such as fastening screw nut 25 composition of 3 24 and surface knurling.The outer peripheral face of valve body 1 lower end and bottom flange 11 projection two D2 Being drilled with radially small through hole two h and radially small through hole three j on the appropriate location of outer peripheral face respectively, after brill, outer end all blocks with steel ball 9, The axis in two holes is on same vertical plane.Aperture three L it is drilled with, with the radial direction small through hole two vertical phase of h on the lower surface of valve body 1 Handing over, the end of aperture three L is machined with the conical surface；It is drilled with hole m, with radial direction small through hole three on the end face of bottom flange 11 projection two D2 J intersects vertically, and the downside of hole m is machined with female thread, and aperture three L communicates with hole m, and axis is on the same line.Diaphragm 10 Outward flange is provided with corresponding aperture, concentric with hole m.Being equipped with valve rod 23 in the m of hole, valve rod is stairstepping, and epimere is relatively thin, Top is machined with frustum, and frustum is close with the conical surface of aperture three L end joins and forms valve port；Stage casing is used as leading when it moves up and down To, O-ring seals 3 24 leaks in order to prevent medium；Hypomere is machined with external screw thread, screws with the female thread on the downside of the m of hole； Tail end is machined with the square opening in order to rotation valve rod, and fastening screw nut 25 loosens in order to prevent it after shutting valve port.

Under normal circumstances, valve rod 23 is tightened so that it is the frustum of upper end is in close contact with the taper hole of aperture three L end, and valve port closes Closing, now the upper and lower cavity of diaphragm 10 is obstructed.

When checking drain valve function, first fastening screw nut 25 is unclamped, then rotation valve rod 23, make valve port open, now The water under high pressure P1 of diaphragm 10 cavity of resorption enters on diaphragm 10 through aperture j, annular gap i, valve port, aperture three L and aperture two h Chamber, the hydraulic pressure P2 of diaphragm epicoele raises, and when (P1-P2) is less than setting value, drain valve 5 is opened draining, repeatedly tested several Secondary, if not draining when valve rod 23 is tightened, draining when unclamping, then can confirm that drain valve function is normal.Otherwise, drain valve is Break down, answer on-call maintenance.Because detection method is convenient, can detect at any time, can find that drain valve is the most faulty early, Process in time, prevent large amount of sewage from flowing backwards.

This invention takes that to advantageously reduce the aggregate measures of flow resistance as follows:

(1) two check-valves is provided with permanent magnet and armature, so when valve port is fully open, the bullet of nearly half can be offset Spring pressure, is computed, and without Magnet and armature, the flow loss of two check-valves is about 0.04MPa, has used about 0.022MPa, Reduce 0.018MPa；

(2) meeting on the premise of entery and delivery port check-valves opens pressure, reducing spring rate, with reduce valve port fully open time Spring pressure；

(3) change drain valve structure, intermediate cavity no longer has the montant running through upper and lower；

(4) in order to reduce flow resistance to greatest extent, the present invention particularly payes attention to the design of flow section area and runner, existing with DN100 Backflow preventer be explained:

A) table 1 is main flow section area and the ratio of nominal dimension area.

Table 1

Note: in design specification requires valve, each flow section area is not less than the 80% of nominal area

As shown in Table 1, the ratio requirement much larger than 80%, flow section area is big, and flow velocity is the lowest, and square the becoming of flow resistance and flow velocity Direct ratio, this is largely effective to reducing flow resistance under high flow velocities.

B) when medium flows in valve pocket, all contacts site with each part or leave position all have 30 °～60 ° of chamferings or Fillet, to reduce local eddy currents loss.

C) short series length standard is used, to reduce linear loss.

D) valve pocket inwall and each part of intracavity, all surfaces contacted with flow media all carry out machining, and surface smoothness is high.

Survey through model machine, when velocity of medium is 3m/s, flow resistance loss about 0.32MPa；When flow velocity is 2m/s, flow resistance Lose about 0.025MPa, approve for water supply department, can be used for the relatively low area of pressure of supply water.

Claims (10)

1. a micro-resistance pressure reduction type backflow preventer, have valve body (1), valve gap, water inlet check-valves (3),

Go out Water Check Valve (4) and drain valve (5)；

Water inlet check-valves (3) and go out Water Check Valve (4) and be arranged horizontally in the intermediate cavity (H2) between valve body (1) and bonnet, (2), its axis is consistent with valve body intake-outlet axis；

Drain valve (5) is arranged between valve body lower end face and bottom flange (11), and the axis that its axis is imported and exported with valve body intersects vertically, and has some osculums one (e) to connect with drain chamber (H4) under valve body (1) on quartered；

It is characterized in that: described drain valve is provided with the guiding valve (16) linked into an integrated entity with diaphragm (10), the endoporus of guiding valve is equipped with piston (17), the central shaft upper surface of piston is under the effect of spring (13), and the boss lower surface with pressing plate (21) contacts all the time；

Valve body lower end is provided with the through hole that intake pressure introduces diaphragm cavity of resorption and the water trap function detection device that the upper and lower chamber of diaphragm can be made to connect with bottom flange (11) connecting portion.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1, it is characterized in that: described bottom flange (11) includes casting all-in-one-piece lower flange, the cylinder that there is sinking at middle part, some projections of in position going up, and described projection includes projection one and projection two (D1, D2)；In the cylinder endoporus of bottom flange (11), close-fitting has sleeve (12), is equipped with guiding valve (16) in the endoporus of sleeve, is equipped with piston (17) in the endoporus of guiding valve, and the upper of piston is positioned by the internal shoulder on guiding valve top；Bottom flange is additionally provided with, on (11), the through hole that intake pressure introduces diaphragm cavity of resorption.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1 and 2, it is characterized in that: the upper end cylindrical of described guiding valve (16) has been got on the bus screw thread, the inner ring of diaphragm (10) is pressed on the upper surface of guiding valve (16) outer convex shoulder by clamp nut (19) and packing ring (20), in the case of not water flowing, outward flange and the inner ring of diaphragm (10) are located substantially in same level.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1 and 2, it is characterized in that: the top of described guiding valve (16) is provided with annular sword limit, with the valve port that the sealing gasket (22) being arranged on body base forms drain valve, the Assurance of Size of valve port is in the case of normal water supply, ratio pressure about 0.6 MPa of the two, to ensure the reliability sealed.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1 and 2, it is characterised in that: described piston (17) is made up of the piston ring outside central shaft, central shaft and two straight dowels, has two mounting holes (f) between muscle.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1 and 2, it is characterized in that: the lower end of described piston (17) lower section spring (13) is connected to centre to be had on the Adjusting bolt Adjusting screw (15) of osculum two (g), described Adjusting bolt Adjusting screw (15) is screwed in the female thread of guiding valve (16) lower end, in order to regulate spring force.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1 and 2, it is characterized in that: described intake pressure introduces the through hole of diaphragm cavity of resorption and is: is drilled with radial direction small through hole one (d) connected with diaphragm cavity of resorption on the outer peripheral face of bottom flange projection one (D1), is blocked outer end with steel ball (9) after brill；Bottom flange bottom surface is drilled with aperture one (c), intersects vertically with radial direction small through hole one (d), and goes up the aperture two (b) connected with intake antrum on same centrage with being positioned at valve body (1)；By the upper inclined hole (a) connected with snout cavity of valve body (1), the corresponding through hole on aperture two (b), diaphragm (10) and aperture one (c), radially small through hole one (d), intake pressure (P1) is incorporated into the cavity of resorption of diaphragm (10).

Micro-resistance pressure reduction type backflow preventer the most according to claim 2, it is characterised in that: the lower flange upper surface of bottom flange (11) has boss, boss to be provided with can get rid of the blowdown bolt (18) accumulating in dirt in diaphragm cavity of resorption easily.

Micro-resistance pressure reduction type backflow preventer the most according to claim 1 and 2, it is characterized in that: water trap function detection device is arranged in the projection two (D2) of bottom flange and the intercommunicating pore at clamping diaphragm (10) position, valve body (1) lower surface, including valve rod (24), O-ring seals three (25) and fastening screw nut (26)；Described valve rod (24) is stairstepping, and epimere is relatively thin, and top is machined with frustum, stage casing is used as guiding when it moves up and down, and preventing medium from leaking with O-ring seals three (25), hypomere is machined with external screw thread, and there is fastening screw nut 26 end in order to prevent valve rod from loosening after shutting valve port.

Micro-resistance pressure reduction type backflow preventer the most according to claim 9, it is characterized in that: described intercommunicating pore includes being drilled with respectively on the appropriate location of valve body (1) lower end periphery face and bottom flange projection two (D2) outer peripheral face radially small through hole two (h) and radially small through hole three (j), after brill, outer end all blocks with steel ball (9), and the axis of holes is on same vertical plane；Being drilled with aperture three (L) on the lower surface of valve body (1), intersect vertically with radial direction small through hole two (h), the end of aperture three (L) is machined with the conical surface coordinated with valve rod (24) end frustum, thus forms valve port；It is drilled with, on the end face of bottom flange projection two (D2), the hole (m) coordinated with valve rod, described hole (m) intersects vertically with radially small through hole three (j), communicate and concentric with aperture three (L), diaphragm (10) outward flange is provided with corresponding aperture, concentric with hole (m), the downside in hole (m) is machined with the female thread coordinated with valve rod (24) external screw thread.