CONSTANT AIR FLOW RATE VALVE, AND PROCEDURE FOR CONTROLLING A CONSTANT AIR FLOW RATE VALVE

Abstract: A constant air flow rate valve (1) with a changing cross section, preferably conical, passage section (14) and within said passage section (14) a throttling member (3) changing shape and which in dependence of the differential pressure across the passage section (14) moves towards the flow walls (14a) of the passage section (14). As taught by the invention, the throttling member (2) with throttling part (3) has been disposed to be displaceable in the direction of the central axis (X1) of the passage section (14) for imposing the set-point value of flow rate. The invention also concerns a procedure for controlling a constant air flow rate valve.

Description: Constant air flew rate valve, and procedure for controlling a constant air flew rate valve The present invention concerns a constant air flew rate valve where in a flew passage confined by a passage section has been disposed a throttlJLng member presenting a throttling part which changes shape. A constant air flew rate valve of this type has been disclosed e.g. in the EP Patent No. 0027068. Constant air flew rate valves of prior art have an elastic throttling member vrtiici- has been placed in the interior space of the air passage. When the diffeir- ential pressure acting across the throttling merober increases, the throttling member changes shape so that the flew aperture is re¬ duced. The higher the differential pressure becomes, the smaller becomes the flew aperture similarly, decrease of the differential pressure causes the flew aperture to grew larger. In this way the cdr flew passing throug the constant air flew rate valve is kept approximately constant. The object of the invention is to provide an improved constant air flew rate valve in τtfiich the known drawbaciks of the above-mentioned constant air flew rate valves are avoided, that is, in which within a wide enough differential pressure range is achieved a large encugh t____t_ugh-flcw in relation to the passage size, and vfaerein even at high flew velocities the noise level is lew, and in said valve the passing air flew rate is controllable to equal a given air flew rate set-point value, and said valve being advantageous in manufacturing. The constant air flow rate valve of the invention is mainly charac¬ terized in that the substantially circular projection of the valve's throttling member on a plane perpendicular against the central axis has been disposed to grew on its periphery when the differ- ential pressure increases, respectively to d__minish on its periphery when the differential pressure grows less. The abover-mentioned changing of the projection is understood to mean that the t_h__σttling portion of the t_hrσttl__ng part has been arranged, depending on the differential pressure across the valve, to move radially with its entire mantle surface cross section towards the passage section constituting the flew aperture. ι_& constant εdr flew rate valve of the invention is advantageously so designed that said valve passage is a conical structure of which the cross section area decreases linearly in the direction of the longitudinal axis. New when the throttling member is moved in relation to said valve passage, the distance of the throttling member frαn the valve passage will be changed at the same time. The substantially circular configuration of the elastic throttling member in the constant air flew rate valve of the invention enables the throttling to take place uniformly over the entire flew cross section area. The invention also concerns a procedure for controlling the constant air flew rate valve. The procedure of the invention is in its main parts characterized in that the εdr flew rate set-point value is input to the constant air flew rate valve by changing the position relative to each other of the elastic t-hrσttling part of thie constant air flew rate valve's throttling member and the, preferably conical, passage section of the passage section with variable flew cross section area. In accordance with the invention a novel constant air flew rate valve controlling method has been iinplemented wherein set-point adjustment is substantially stepless within a wide flew rate range in such manner that one limit of the flew rate is the fully closed position of the valve, or zero flew condition. The stnictural design of the constant air flew rate valve of the iirverrtion is also very simple and advantageous in view of manufacturing tech¬ nology. As taught by the invention, adjustment of the set-point value of the constant air flew rate valve is advantagecusly ac- cσplished in that the t-hrottling member with substantially circular cross section and made of an elastic material is moved in relation to the valve passage in the direction of the longitudinal axis of the valve passage. T e invention is described in the following, referring to the figures that have been enclosed. In Fig. 1 is depicted a constant air flew rate valve according to the invention, in elevatiαnal sectioned view, the spring of the constant air flew rate valve having been sca-ieπatically indicated in this figure. In Fig. 2 are illustrated the two extreme positions of the constant air flew rate valve of the invention, these positions being indi¬ cated with symbols C^ and C2, respectively. In Fig. 3 are shown said extreme positions C-_ and C2 of Fig. 2 along the section lines A-A and B-B, whereof the section plane A-A represents one extreme position C and section plane B-B represents the other extreme position C2. In Fig. 1 is indicated with reference numeral 1, the constant air flew rate valve of the invention. The constant air flew rate valve 1 comprises a throttling member, which has been indicated with the general reference numeral 2. The throttling member 2 comprises a throttling part 3 made of an elastic material, preferably of sili¬ cone. The throttling part 3 has a flcw^throttling portion 3a, and at its ends a first end portion 3b and at the other end a second end portion 3c. The first end portion 3b carries a spring fixing shoulder or another equivalent spring fixing part 3bι, and on the same end is also located the first fixing border 3)_ for the throt- tling part 3. In the other end portion 3c is located the second fixing border 3cτ_ for the t-hrσttling part 3. The throttling member 2 comprises a body part 4, consisting of a main body 4a and a fixing disk 4b attaching thereto substantially in its central area. The fixing disk 4b carries fixing means 4bχ for the end of the spring, these being preferably formed by cavities in which one end of the spring can be placed and in which the spring is thus firmly held. The fixing disk 4b also comprises a second fixing border 3b2 for the throttling part 3, fixing means 4b2, likewise preferably formed by a cavity, the second border 3b*2 of the throttling part 3 being placeable and fixable in this cavity. The main body 4a is advantageously an elongated, cylindrical body part having on its central axis an elongated threaded hole 4a , closed at one end, for the shaft 10. The threads provided on the shaft 10 and in the threaded hole 4a^ in the body 4 are compatible as to their thread systems so that the body 4 can be rotated on the shaft 10 in the direction of the central axis X ] _. The body 4 has also been provided with a threaded hole 4a for the set-point value locking screw 9. This enables the throttling member 2 to be locked in a given position on the shaft 10. Between the throttling part 3 and the body 4 remains an expansion chamber 6, in this chamber being accommodated a spring 5, preferably a compression spring. The chamber 6 communicates by an air aperture 7 with the entrance chamber 8 and, further, through the central aperture 11a in the flew deflector part 11 with the air space on the incoming εdr flew side of the throttling member 2. Said air cxsraπunication has expressly been provided to enable air to flew through the apertures 11a and 7 into the expansion chamber 6 when the t-irottling part 3 changes shape. The shaft 10 has expressly been provided for set-point fixing. The throttling member 2 can be displaced in the direction of the central axis of the shaft 10 to assume the position on the shaft 10 which is desired in each particular instance and, thereby, the desired position in relation to the passage striictu_.es of the valve. The εdr flew deflector part 11 has been attached to the throttling part 3 in the region between the throttling portion 3a and the first end portion 3b. The flew deflector part 11 is a part with curved surface and its effect is, by its curvature, to deflect the flew smoothly to pass along the flew path defined between the throttling part 3 and the passage. The flew deflector part 11 has a central air aperture 11a, throughvfaic air is enabled to flew into the chamber 8 and, further, through the εdr aperture 7 into the equalizing chamber 6, or vice versa, depending on whether the throttling of the air flew is being increased or reduced, i.e., whether the chamber 6 expands or contracts. The locking part 12 is located at one very end of the body 4a. It is possible bymeans of the locking part 12 to ensure the holding of the first fixing border 3b 2 of the throttling part in contiguity with the body proper, 4. The fixing part 12 is provided with a central flew aperture, and it has on one end a shoulder 12a which urges the fixing border of the throttling part 3 into the cavity in the main body 4a and holds it there. The shaft 10 is attached to a yoke part 13, which is further fixedly positioned in relation to the valve passage 14. The valve is pro¬ vided with a set-point scale, this scale being advantageously marked on the shaft 10. The valve passage 14 is most advantageously a conical body. The passage section 14 has a flew surface 14a obliquely positioned in relation to the central axis X_. The passage section 14 flares out cαnically. Its flew cross section is substantially circular, and consequently the central axis X_ i* 3 ' at t* 1 * 3 ssa time, the axis of symmetry for the passage section. To the flew section 14a adjoins a curved intake section 14b. The flow, -when entering the valve as indicated by arrcw L, encounters the throttling part 2 and its flew deflector part 11, which deflects the flew to the flew path defined between the passage 14 and the throttling part 2. The spring 5 is fitted with one end to the iirσttling part 3 and with its other end to the fixing disk 4b on the body 4 of the throttling member 2, in its spring end fixing means 4b l7 which preferably consist of cavities. On the other end, the spring 5 is attached to the throttling part 3 itself, to its first end portion 3b. It is fixed on said first end portion 3b with the εdd of a spring fixing shoulder 3bι or equivalent. In the constant air flew rate valve controlling procedure of the invention, the valve is adjusted to pass an air flew of given magnitude, independent of the differeπticil pressures, by setting the t_hrottli_ng member 2 in a given position en the central axis X of the passage section 14. Since the passage section 14 expands in conical fashion, it is cibvicus that vrtien the throttling meπiber 2 is displaced in the direction of the central axis ^ the throttling member 2 can always be made to be located at desired distance from the flew surface 14a disposed obliquely in relation to the central axis X ] _ of the passage section 14. When the throttling member 2 is positioned in the close vicinity of the curved part 14b of the passage section 14, the throttling regions of the t-hrottling part 3 of throttling member 2 are located very close to the flew surface i4 of the passage section 14. In this case a set-point has been imposed at whic the least possible air flew is admitted to pass through the valve. When, on the other hand, the t_hrottling member 2 is located as far away as possible from the intake aperture A t_hrσugh which the εdr enters the valve, the t-hrottling part 3 of throttling member 2 is located as far as possible from the flew surface 14a of the passage section 14, and the greatest possible flew is admitted throug the valve. It is thus understood that, by positioning the throttling member 2 in a given position on the central axis X , one at the same time positions said throttling iπerriber 2 at a given distance from the flew surface 14a of the passage section 14. Thus, setting of the set-point is accomplished by moving the throttling member 2 along the X axis in relation to the passage section 14, which, is conical. This displacement may be accomplished by rotating the tlirottling member 2 on the threads of the shaft 10 so that the throttling member 2 is displaced en the axis X » When a given flew rate set-point has been attained, the screw 9, cr equivalent, may be turned to secure the position of the throttling member 2 on the shaft 10. The shaft 10 is in this case fixedly carried in the yoke 13, this yoke 13 further being fixedly located in relation to the passage section 14. It is cbvious that the control procedure may equally be iirplemented in such manner that the shaft 10 is fixedly attached to the tlirofttling member 2, the throttling member 2 together with the shaft 10 then being rotated in threads provided in the yoke 13. in Fig. 2, two extreme shapes of the throttling part 3 have been reproduced. C indicates that shape of the throttling part 3 with which the flow aperture is at its largest. C 2 , agεdn, indicates in . this figure that shape of the tiirottling part 3 with which the flew aperture is smallest. Fig. 3 illustrates these two extreme shapes of the throttling part 3, in cross section and shown as sectioned along the lines A-A and B-B in Fig. 2. When the throttling part 3 is in the state in which the maximum flew aperture is provided, the throttling portion wall of the t-hrottling part 3 is pleated in undulating fashion (section A-A) . This wavy .shape enables the tirσttling part 3 to expand towards the flew surface 14a of the passage section 14. C 2 in Fig. 3 indicates this tlirottling part 3 when fully expanded, in which case the cross section shape is circular (section B-B) . The crests and dales of the waves occurring here run parallel to the central axis X ] _. In an advantageous embod__merrt of the invention, the shaft 10 is a guide with rectangular cross section, on which the throttling member 2 can be secured in various positions with the εdd of a locking screw or equivalent. The guide carries en one face a scale for different flew rate settings. The chamber 8 serves as a damping means preventing resonance vi¬ brations of the throttling part 3. In an advantageous embodiment of the invention, a wide chamber space has been established at the point 8' in the body part 4a of the t_hrottling member 2, commu¬ nication being provided therefrom to the space on the i-ricαming flew side, and one or several air apertures to the equalizing space 6. The respective chamber in the body part 4a will then cperate as a highly effective resonance damping means, and no anterior chamber 8 is then needed in this embodiment.

Claims: Claims 1. A constant air flow rate valve (1) with a t-hrottling meπiber (2) disposed in a flew passage defined by a passage section (14) and featuring a t-hrottling part (3) changing shape under effect of the differential pressure acting across the constant air flew rate valve, characterized in that the substantially circular projection of the t_hrottling member (2) on a plane perpendicular to the central axis (X_) has been arranged to grew of its periphery when the differential pressure increases, respectively to became smaller of its periphery when the differential pressure becomes less. 2. Constant εdr flew rate valve according to the preceding claim, characterized in that the passage section (14) is one with changing cross section. 3. Constant εdr flew rate valve according to the preceding claim, characterized in that the throttling member (2) has been disposed to move in the direction of the central axis (X_ of the passage section (14) for iπposing the flew rate set-point value. 4. Constant air flew rate valve according to any one of the.pre¬ ceding claims, characterized in that the throttling member (2) comprises a spring (5) disposed around the main body (4a) of the tody (4) of the throttling meπiber (2) in the equalizing space (6) defined between the body (4) and the throttling part (3) . 5. Constant εdr flew rate valve according to any one of the pre¬ ceding claims, characterized in that the valve comprises a shaft (10) or equivalent εdαng which, or around *4dch, the throttling member (2) can be displaced on the central axis (X_), the shaft (10) or equivalent having been disposed to be fixedly positioned in relation to the passage section (14) . 6. Constant air flew rate valve according to any one of claims 1-4, characterized in that the constant air flew rate valve cent- ^ prises a shaft (10), or equivalent holder, v ch is fixedly pos¬ itioned in the throttling member (2) , and that the shaft (10) has an one end threads, splines or other equivalent elements for dis¬ placement of the throttling member (2) in the direction of the 5 central axis (X ) in relation to the passage section (14) . 7. Constant air flew rate valve according to airy one of the pre¬ ceding claims, characterized in that the throttling member (2) comprises on that surface which is foremost with reference to the 0 flew, a flew deflector part (11) Vhich is curved of its surface and which has been provided with at least one air aperture (11a) for admitting εdr flew into a chamber (8) and -further t-hrσugh an air aperture (7) into the equalizing chamber (6) . 5 8. Constant air flew rate valve according to any one of the pre¬ ceding claims, characterized in that the shaft (10) is located substan'tially on the central axis (X_) of the passage section (14) . 9. Constant air flew rate valve according to any one of the pre- 0 ceding claims, characterized in that the throttling portion (3a) of the throttling part (3) of the t-hrottling meπiber (2) assumes in one extreme position (C_) a wavy shape in which the wave crests and dales run substantially parallel to the central axis X , and that the throttling portion (3a) in its other extreme position 5 assumes a shape (C 2 ) with circular cross section. 10. Procedure for controlling a constant air flew rate valve, in said constant air flew rate valve the air flew rate keeping approxi¬ mately equal to a value, independent of the differ¬ 0 ential pressure across the valve, characterized in that the εdr flow rate set-point value of the constant air flew rate valve is imposed by changing the position relative to each other of the elastic throttling part (3) of the throttling member (2) of the constant air flew rate valve and the passage section with changing 5 cross section area, preferably a conical passage section. 11. Procedure for cxatrolling a constant air flew irate valve accord¬ ing to the preceding claim, characterized in that imposing the εdr flew rate set-point value is accomplished by increasing or reducing the distance between the entire cross section area of the mantle of the throttling part (3) and the passage section (14) . 12. Procedure for controlling a constant air flew rate valve accord¬ ing to claim 10 cr 11, characterized in that the εdr flew rate set-point value is imposed on the constant air flew rate valve by displacing the throttling part (3) of the t_h__ottling meπiber (2) of the constant air flew rate valve (1) in the direction of the central axis (Xi) of the conically widening passage section (14) . 13. Procedure for controlling a constant air flow rate valve accord- ing to any one of claims 10-12, characterized in that for adjusting the flew rate set-point value of the constant air flow rate valve the displacement in the direction of the X± axis and the imposing of set-point vεilue is accomplished by rotating the throttling member (2) or merely moving it axially in the direction of the Xτ_ axis.

Inventors: VARUNKI MARKKU, VARUNKI, MARKKU
Applicants: HALTON OY
Application year: 1986
Main classification: F24F11
IPC codes: F24F11