CN111779846A

CN111779846A - Butterfly valve

Info

Publication number: CN111779846A
Application number: CN202010633378.0A
Authority: CN
Inventors: 陈少同; 姜桂梅; 马玉英
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-04
Filing date: 2020-07-04
Publication date: 2020-10-16

Abstract

The invention discloses a butterfly valve, comprising: valve body, butterfly plate and valve rod, the valve rod is worn to establish along radially rotating in the valve body, the butterfly plate passes through the valve rod location is in the valve body inner chamber can round the valve rod upset, the sealing washer is installed at the sealed position of valve body, the outward flange pressure equipment of butterfly plate has the rubber circle, the sealing washer with the rubber circle is constituteed the valve body with sealed vice between the butterfly plate, the butterfly valve still include protection machanism, protection machanism with the butterfly plate is connected can be to the import side when the butterfly plate is in the open mode on the butterfly plate the rubber circle outside is carried out the closing cap protection. The invention has the advantages that: through setting up a plurality of backplate, when the butterfly valve was opened, it is rotatory to make the control lever, can control the backplate rotatory, and then seals the rubber circle on the butterfly plate of import side and cover to can play the guard action to the rubber circle, prevent that the medium from to the washing away of rubber circle, improve the life of butterfly valve.

Description

Butterfly valve

Technical Field

The invention belongs to the technical field of pipeline valves, and particularly relates to a butterfly valve.

Background

The butterfly valve is a valve which utilizes a circular butterfly plate to rotate along with a valve rod to open, close and adjust a fluid channel. Most butterfly valves can be used for controlling a conveying switch of suspended solid particle media, and can also be used for controlling the conveying switch of powder and particle media according to the strength of a sealing piece, so that the butterfly valves are widely used in the fields of petroleum, chemical engineering, metallurgy, electric power, food, medicine, water supply and drainage, gas conveying and the like.

The multi-layer three-eccentric metal sealing butterfly valve is a widely applied one in the butterfly valve, wherein the butterfly plate is eccentrically arranged in the valve body, and the valve shaft is eccentrically arranged on the butterfly plate to control the opening and closing of the butterfly plate.

When the butterfly valve is used for on-off control of a medium with suspended solid particles on a conveying belt, the solid particles in the medium can continuously flush the butterfly valve along with the flowing of the medium, so that the anti-flushing capacity of the butterfly valve directly determines the service life of the butterfly valve. In the prior art, chinese patent document CN2594565Y discloses a novel sealing flange type eccentric butterfly valve, wherein a "convex" frame table is made at the sealing position of the valve body of the butterfly valve, and sealing pairs are installed on the valve body and the butterfly plate, that is, o-shaped sealing rings are installed at two end faces of the "convex" frame table of the valve body, and an inner "n" -shaped stainless steel ring band is embedded on the "convex" frame of the valve body, so as to form a valve body seal; meanwhile, the T-shaped rubber ring is pressed in the groove of the butterfly plate through the pressing ring and the fastening piece to form butterfly plate sealing, so that a sealing pair of the valve body and the butterfly plate is formed. Therefore, in the sealing flange type butterfly valve in the prior art, the stainless steel ring is arranged on the O-shaped sealing ring of the valve body, so that the anti-scouring capability of the O-shaped sealing ring on the valve body is improved, but no protective measure is taken on the rubber ring arranged on the butterfly plate, when the butterfly plate is in a sealing state, a medium is in a slow flowing or even static state, and the medium does not cause abrasion or very little abrasion on the butterfly plate, so that even if no protective measure is taken on the rubber ring on the butterfly plate, the rubber ring is not greatly abraded; however, when the butterfly plate is in an open state, the rubber ring directly faces the oncoming high-speed flowing medium in the positive direction, and when the medium rapidly passes through the valve body, suspended solid particles contained in the medium continuously abrade the rubber ring in high-speed motion, so that the rubber ring is easily abraded, the sealing effect when the butterfly valve is closed is influenced, and the service life of the butterfly valve is further shortened.

Disclosure of Invention

In view of the above, it is desirable to provide a butterfly valve capable of protecting a rubber ring when a butterfly plate is in an open state.

The invention discloses a butterfly valve, comprising: valve body with import and export, with rotatable mode set up in valve rod on the valve body, fixed set up in butterfly plate on the valve rod, the sealing washer is installed at the sealing position of valve body, the outward flange pressure equipment of butterfly plate has the rubber circle, the sealing washer with the rubber circle is constituteed the valve body with sealing pair between the butterfly plate is used for realizing the cutout of valve body, the butterfly valve still include protection machanism, protection machanism with the butterfly plate is connected can be to the import side when the butterfly plate is in the open mode on the butterfly plate the rubber circle outside carries out the closing cap protection, protection machanism includes: the protective plate is hinged to the butterfly plate, the rubber ring on the inlet side can be covered by rotating the protective plate, and therefore when the butterfly plate is in an open state, media positively flush the protective plate and flow along two sides of the butterfly plate; one end of the connecting rod is hinged to the protective plate, the other end of the connecting rod is connected to the butterfly plate in a sliding mode, and the connecting rod moves back and forth along the radial direction of the butterfly plate so as to drive the protective plate to close or open the rubber ring on the inlet side; the turntable is rotationally connected to the butterfly plate, an arc-shaped groove is formed in the turntable, one end, away from the protective plate, of the connecting rod is connected with the butterfly plate in a sliding mode through the arc-shaped groove, the arc-shaped groove can be driven to rotate through rotation of the turntable, and then the distance between the connecting rod and the center of the butterfly plate can be changed, so that the connecting rod is driven to move along the radial direction of the butterfly plate; and the transmission assembly is arranged at the axial position of the valve rod, is connected with the turntable and can drive the turntable to rotate by rotating.

In one embodiment, the transmission assembly comprises a control rod, a driving bevel gear and a driven bevel gear fixedly connected to the center of the rotary table, the control rod penetrates through the axial center of the valve rod and is fixedly connected with the driving bevel gear, the driving bevel gear is meshed with the driven bevel gear, the driving bevel gear can be driven to rotate by rotating the control rod, and the driving bevel gear drives the driven bevel gear to rotate, so that the rotary table is driven to rotate.

In one embodiment, a first locking clamp is fixedly connected to the upper end of the valve rod, a first locking disc is fixedly arranged on the upper portion of the valve body, a second locking clamp is fixedly connected to the upper end of the control rod, a second locking disc is fixedly arranged on the upper end of the valve rod, a plurality of locking openings are formed in the first locking disc and the second locking disc, the first locking clamp can be clamped into the locking opening of the first locking disc to enable the valve rod to be fixed with the valve body, and the second locking clamp can be clamped into the locking opening of the second locking disc to enable the valve rod to be fixed with the control rod.

In one embodiment, the guard plate comprises an arc-shaped blocking piece concentric with the rubber ring and a connecting piece used for hinging the connecting rod, and the connecting piece is further hinged with the butterfly plate.

In one embodiment, a sliding groove is formed in the end face of the butterfly plate, a sliding block is connected in the sliding groove in a sliding mode, and one end of the sliding block penetrates through the arc-shaped groove and is hinged to the connecting rod.

In one embodiment, when the butterfly plate is in an open state, the sliding block is driven to move along one side of the sliding groove away from the circle center position of the butterfly plate through forward rotation of the rotary disc, so that the connecting rod can be driven to generate thrust to the protection plate, the protection plate is enabled to flip towards the butterfly plate, and therefore the rubber ring on the inlet side can be sealed and protected; when the butterfly plate is in a closed state, the rotary table rotates reversely to drive the sliding block to move along one side, close to the circle center position of the butterfly plate, of the sliding groove, and then the connecting rod can be driven to pull the protective plate, so that the protective plate is turned up towards the two sides of the butterfly plate, and the sealing effect between the rubber ring and the sealing ring is guaranteed.

In one embodiment, the rotary table is provided with two rotary tables, the centers of the two rotary tables are connected with each other, so that the two rotary tables rotate synchronously, the two rotary tables are respectively arranged on two sides of the butterfly plate, one rotary table is provided with an arc-shaped groove, the other rotary table is provided with two arc-shaped grooves, the guard plate is provided with three guard plates, one guard plate is connected with the rotary table which is provided with only one arc-shaped groove, the other two guard plates are connected with the rotary table which is provided with the two arc-shaped grooves, the number of the connecting rods is three, and each connecting rod is correspondingly connected with one guard plate.

In one embodiment, the three guard plates are alternately distributed on two sides of the dish plate.

The technical scheme has the advantages that: the butterfly valve is provided with the plurality of guard plates, when the butterfly valve is opened, the control rod is rotated, the guard plates can be controlled to rotate, and the rubber ring on the butterfly plate at the inlet side is covered, so that the rubber ring can be protected, the rubber ring is prevented from being washed by media, and the service life of the butterfly valve is prolonged.

Drawings

FIG. 1 is an overall cross-sectional view of a butterfly valve provided by the present invention;

FIG. 2 is a front view of a butterfly valve provided by the present invention;

FIG. 3 is a cross-sectional view taken at A-A of FIG. 1 in accordance with the present invention;

FIG. 4 is a cross-sectional view taken at B-B of FIG. 1 in accordance with the present invention;

FIG. 5 is a first cross-sectional view of the butterfly valve according to the present invention in an open state, wherein the cover plate is in the open state;

fig. 6 is a second cross-sectional view of the butterfly valve according to the present invention in an open state, wherein the protection plate is in a protection state;

FIG. 7 is a cross-sectional view taken at C-C of FIG. 6 in accordance with the present invention;

FIG. 8 is a rear perspective view of a butterfly plate of the butterfly valve of the present invention;

FIG. 9 is a front perspective view of a butterfly plate of the butterfly valve of the present invention;

fig. 10 is a perspective view of a butterfly valve cover according to the present invention.

In the figure, a valve body 1, a sealing ring 11, an inlet 12, an outlet 13, a butterfly plate 2, a rubber ring 21, a sliding groove 22, a sliding block 23, a valve rod 3, a first locking clamp 31, a first locking disc 32, a protective plate 4, an arc-shaped baffle 41, a connecting sheet 42, a connecting rod 5, a rotating disc 6, an arc-shaped groove 61, a control rod 7, a second locking clamp 71, a second locking disc 72, a driving bevel gear 8 and a driven bevel gear 9.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It will be understood that when an element is referred to as being "mounted on" another element, it can be directly on the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.

As shown in fig. 1 to 4, the present invention discloses a butterfly valve, including: valve body 1 with import and export, with rotatable mode set up in valve rod 3 on the valve body 1, fixed set up in butterfly plate 2 on the valve rod 3, sealing washer 11 is installed at the sealing position of valve body 1, the outward flange pressure equipment of butterfly plate 2 has rubber circle 21, sealing washer 11 with rubber circle 21 is constituteed valve body 1 with sealed pair between the butterfly plate 2 is used for realizing the cutout of valve body 1, the butterfly valve still include protection machanism, protection machanism with butterfly plate 2 is connected can be to the import side when butterfly plate 2 is in the open mode on the butterfly plate 2 the rubber circle 21 outside carries out the closing cap protection, protection machanism includes: the protective plate 4 is hinged on the butterfly plate 2, the rubber ring 21 on the inlet side can be covered by rotating the protective plate 4, so that when the butterfly plate 2 is in an open state, a medium positively washes the protective plate 4 and flows along two sides of the butterfly plate 2; one end of the connecting rod 5 is hinged to the guard plate 4, the other end of the connecting rod 5 is connected to the butterfly plate 2 in a sliding mode, and the connecting rod 5 moves back and forth along the radial direction of the butterfly plate 2 so as to drive the guard plate 4 to close or open the rubber ring 21 on the inlet side; the rotary table 6 is rotatably connected to the butterfly plate 2, an arc-shaped groove 61 is formed in the rotary table 6, one end, away from the guard plate 4, of the connecting rod 5 is slidably connected with the butterfly plate 2 through the arc-shaped groove 61, the arc-shaped groove 61 can be driven to rotate through rotation of the rotary table 6, and then the distance between the connecting rod 5 and the center of the butterfly plate 2 can be changed, so that the connecting rod 5 is driven to move along the radial direction of the butterfly plate 2; the transmission assembly is arranged at the axial position of the valve rod 3, connected with the rotary disc 6 and capable of driving the rotary disc 6 to rotate through rotation.

It is worth mentioning that the rotary table 6 is provided with two and the center is mutually connected, thereby making two the rotary table 6 rotates synchronously, two the rotary table 6 is respectively arranged on two sides of the butterfly plate 2, one of the rotary table 6 is provided with an arc-shaped groove 61, and the other rotary table 6 is provided with two arc-shaped grooves 61.

In this embodiment, as shown in fig. 10, the guard plate 4 has three pieces, one of the guard plates 4 is connected to the turntable 6 having only one arc-shaped slot 61, and the other two guard plates 4 are connected to the turntable 6 having two arc-shaped slots 61.

It can be understood that when the protection plate 4 is in the capping protection state, three protection plates 4 are in contact in sequence, and two protection plates 4 on the same side are symmetrically distributed on two sides of another protection plate 4, so that the protection plates 4 can continuously cap the inlet side of the butterfly plate 2.

The number of the connecting rods 5 is three, each connecting rod 5 corresponds to one guard plate 4, and the connecting rods 5 are hinged to the middle position of the guard plate 4, so that stable pushing force or pulling force can be generated on the guard plate 4 conveniently.

It should be noted that, by providing two rotating discs 6, and two rotating discs 6 are located at two sides of the butterfly plate 2, so that the protection plates 4 can be disposed at two sides of the butterfly plate 2, it can be understood that the protection plates 4 at two sides of the butterfly plate 2 are alternately disposed, and the protection plates 4 can be effectively prevented from interfering with each other in the opened state.

In other embodiments, other numbers of guard plates 4 may be alternately arranged on both sides of the dish plate 2.

Preferably, the transmission assembly comprises a control rod 7, a driving bevel gear 8 and a driven bevel gear 9 fixedly connected to the center of the rotary table 6, the control rod 7 penetrates through the axial center of the valve rod 3 and is fixedly connected with the driving bevel gear 8, the driving bevel gear 8 is meshed with the driven bevel gear 9, and the control rod 7 is rotated to drive the driving bevel gear 8 to rotate, so that the driven bevel gear 9 is driven to rotate, and the rotary table 6 is driven to rotate.

It will be appreciated that the control rod 7 and the valve stem 3 may be rotated either individually or in synchronism.

Preferably, the guard plate 4 comprises an arc-shaped blocking piece 41 concentric with the rubber ring 21 and a connecting piece 42 used for hinging the connecting rod 5, and the connecting piece 42 is further hinged with the butterfly plate 2.

Preferably, the end surface of the butterfly plate 2 is provided with a sliding groove 22, the sliding groove 22 is connected with a sliding block 23 in a sliding manner, and one end of the sliding block 23 penetrates through the arc-shaped groove 61 and is hinged to the connecting rod 5.

As shown in fig. 8 and 9, it can be understood that the sliding grooves 22 are provided with three pieces, two pieces of which are provided on the end surface of the butterfly plate 2 on the same side as the two protection plates 4, and the other piece of which is provided on the other end surface of the butterfly plate 2, and the two pieces of the sliding grooves 22 provided on the same side as the butterfly plate 2 are symmetrically distributed.

Preferably, as shown in fig. 5 to 7, when the butterfly plate 2 is in the open state, the rotating disc 6 rotates in the forward direction to drive the sliding block 23 to move along one side of the sliding groove 22 away from the position of the center of the butterfly plate 2, so as to drive the connecting rod 5 to generate a thrust force on the protection plate 4, so that the protection plate 4 is flipped toward the butterfly plate 2, and the rubber ring 21 on the inlet side can be covered and protected; when the butterfly plate 2 is in a closed state, the rotary table 6 rotates reversely to drive the sliding block 23 to move along one side of the sliding groove 22 close to the circle center of the butterfly plate 2, so that the connecting rod 5 can be driven to generate a pulling force on the protection plate 4, and the protection plate 4 is turned up towards the two sides of the butterfly plate 2, so that the rubber ring 21 and the sealing ring 11 can be in sealing fit with each other.

It is worth mentioning that, the first lock of upper end fixedly connected with of valve rod 3 presss from both

sides

31, 1 upper portion of valve body has set firmly first lock dish 32, the upper end fixedly connected with second lock of control lever 7 presss from both sides 71, the second lock dish 72 has set firmly in the 3 upper ends of valve rod, a plurality of closure openings have all been seted up on first lock dish 32 and the second lock dish 72, first lock presss from both sides 31 can block into in the closure opening of first lock dish 32 so that valve rod 3 with valve body 1 is fixed, second lock presss from both sides 71 can block into in the closure opening of second lock dish 72 so that valve rod 3 with control lever 7 is fixed.

The working mode of the invention is as follows: if the butterfly valve needs to be opened for medium circulation, the valve rod 3 is rotated in the forward direction to drive the butterfly plate 2 to be opened, the control rod 7 synchronously rotates in the forward direction rotation process of the valve rod 3, at the moment, the drive bevel gear 8 and the driven bevel gear 9 are relatively static, after the butterfly plate 2 is opened, the rotation control rod 7 drives the drive bevel gear 8 to synchronously rotate in the forward direction, the drive bevel gear 8 drives the driven bevel gear 9 to forwardly rotate, the driven bevel gear 9 forwardly rotates to drive the rotating disc 6 to synchronously and forwardly rotate, so that the rotating disc 6 rotates relative to the butterfly plate 2, the arc-shaped groove 61 rotates along with the forward rotation of the rotating disc 6, so that the three sliding blocks 23 move in the respective sliding grooves 22 along the trajectory of the arc-shaped groove 61 away from the circle center of the butterfly plate 2, thrust is generated to the corresponding connecting rods 5, and the three connecting rods 5 respectively generate thrust to, then, the three protection plates 4 are turned over towards the direction of the butterfly plate 2, the rubber ring 21 is covered by the protection plates 4, the three protection plates 4 are sequentially contacted, and at the moment, the protection plates 4 are flushed by the medium in the forward direction and flow along the two sides of the butterfly plate 2, so that the rubber ring 21 is protected;

if the butterfly valve needs to be closed to cut off media, the control rod rotates reversely to drive the driving bevel gear 8 to rotate synchronously and reversely, the driving bevel gear 8 drives the driven bevel gear 9 to rotate reversely, the driven bevel gear 9 rotates reversely to drive the turntable 6 to rotate synchronously and reversely, the turntable 6 rotates reversely to drive the arc-shaped groove 61 to rotate along with the arc-shaped groove, so that the three sliding blocks 23 move close to the circle center of the butterfly plate 2 in the respective sliding grooves 22 along the track line of the arc-shaped groove 61 and generate pulling force for the corresponding connecting rods 5, the three connecting rods 5 respectively generate pulling force for the corresponding three guard plates 4, the guard plates 4 are turned up towards the two sides of the butterfly plate 2, then the valve rod 3 rotates reversely to drive the butterfly plate 2 to close, the inner wall of the valve body 1 and the guard plates 4 do not interfere with each other, and the tight fit between.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A butterfly valve, comprising: valve body with import and export, with rotatable mode set up in valve rod on the valve body, fixed set up in butterfly plate on the valve rod, the sealing washer is installed at the sealing position of valve body, the outward flange pressure equipment of butterfly plate has the rubber circle, the sealing washer with the rubber circle is constituteed the valve body with sealing pair between the butterfly plate is used for realizing the cutout of valve body, its characterized in that, the butterfly valve still include protection machanism, protection machanism with the butterfly plate is connected can be right when the butterfly plate is in the open mode the import side on the butterfly plate the rubber circle outside carries out the closing cap protection, protection machanism includes:

the protective plate is hinged to the butterfly plate, the rubber ring on the inlet side can be covered by rotating the protective plate, and therefore when the butterfly plate is in an open state, media positively flush the protective plate and flow along two sides of the butterfly plate;

one end of the connecting rod is hinged to the protective plate, the other end of the connecting rod is connected to the butterfly plate in a sliding mode, and the connecting rod moves back and forth along the radial direction of the butterfly plate so as to drive the protective plate to close or open the rubber ring on the inlet side;

the turntable is rotationally connected to the butterfly plate, an arc-shaped groove is formed in the turntable, one end, away from the protective plate, of the connecting rod is connected with the butterfly plate in a sliding mode through the arc-shaped groove, the arc-shaped groove can be driven to rotate through rotation of the turntable, and then the distance between the connecting rod and the center of the butterfly plate can be changed, so that the connecting rod is driven to move along the radial direction of the butterfly plate;

and the transmission assembly is arranged at the axial position of the valve rod, is connected with the turntable and can drive the turntable to rotate by rotating.

2. The butterfly valve of claim 1, wherein the transmission assembly includes a control rod, a driving bevel gear, and a driven bevel gear fixedly connected to the center of the rotary disk, the control rod passes through the axial center of the valve rod and is fixedly connected to the driving bevel gear, the driving bevel gear is engaged with the driven bevel gear, the driving bevel gear can be driven to rotate by rotating the control rod, and the driving bevel gear rotates to drive the driven bevel gear to rotate, thereby driving the rotary disk to rotate.

3. The butterfly valve according to claim 2, wherein a first locking clamp is fixedly connected to an upper end of the valve rod, a first locking disc is fixedly arranged on an upper portion of the valve body, a second locking clamp is fixedly connected to an upper end of the control rod, a second locking disc is fixedly arranged at an upper end of the valve rod, a plurality of locking openings are formed in the first locking disc and the second locking disc, the first locking clamp can be clamped into the locking opening of the first locking disc to fix the valve rod with the valve body, and the second locking clamp can be clamped into the locking opening of the second locking disc to fix the valve rod with the control rod.

4. The butterfly valve of claim 1, wherein the shield includes an arcuate flap concentric with the rubber ring and a connecting tab for articulating with the connecting rod, the connecting tab articulating with the butterfly plate.

5. The butterfly valve according to claim 1, wherein a sliding groove is formed in an end surface of the butterfly plate, a sliding block is slidably connected in the sliding groove, and one end of the sliding block penetrates through the arc-shaped groove and is hinged to the connecting rod.

6. The butterfly valve according to claim 5, wherein when the butterfly plate is in the open state, the sliding block is driven to move along one side of the sliding groove away from the circle center position of the butterfly plate through forward rotation of the rotary disc, and then the connecting rod can be driven to generate thrust on the protection plate, so that the protection plate is flipped towards the butterfly plate, and the rubber ring on the inlet side can be capped and protected; when the butterfly plate is in a closed state, the rotary table rotates reversely to drive the sliding block to move along one side, close to the circle center position of the butterfly plate, of the sliding groove, and then the connecting rod can be driven to pull the protective plate, so that the protective plate is turned up towards the two sides of the butterfly plate, and the sealing effect between the rubber ring and the sealing ring is guaranteed.

7. The butterfly valve according to claim 1, wherein two of said turntables are provided and are connected to each other at their centers, so that said two turntables rotate synchronously, said two turntables are respectively provided at two sides of said butterfly plate, one of said turntables is provided with an arc-shaped slot, the other of said turntables is provided with two arc-shaped slots, said guard plate is provided with three pieces, one of said guard plates is connected to said turntable provided with only one of said arc-shaped slots, the other two of said guard plates are connected to said turntable provided with two arc-shaped slots, said connecting rods are provided with three pieces, and each of said connecting rods is correspondingly connected to one of said guard plates.

8. The butterfly valve of claim 7 wherein the three shields are alternately disposed on opposite sides of the disk plate.