FLUID FLOW PROPORTIONING DEVICE.

Description

• Μ·,····' - 2 - Ing· Barzanò & zanardoin the flow path of the main pipe* the second in the flow path leading to the branch pipe of proportioning» to* so that the tt< Ό resistance force acting on the first resisting body *.*{{* I ·* e tends to open the valve and consequently **: • ♦eoeeeeee increases the flow rate through the branch of proportioning» while the resistance force that -;*·* • e acts both according to the resistant body tends to close *·..·*the valve and consequently to reduce the flow rate through the proportional branch DESCRIPTION The present invention relates to a proportioning device to be connected to a main pipe that conveys a fluid under pressure* for the purpose of introducing* or withdrawing* from such main pipe a fluid at a flow rate corresponding to an essentially constant proportion to the instantaneous flow rate of such pipe. The use of proportioning or metering devices that allow the introduction* or withdrawal* of a fluid proportional to the main flow rate of main pipes under pressure is very common and two distinct types of such systems can be distinguished: a) open circuit systems* used with main pipes having a known constant flow rate* in which - 3 — Ing. Barunò & Zanardo the metered flow rate is calculated and calibrated according to the required proportion; b) closed circuit systems in which the flow rate which can vary in the main pipe is continuously sensed, the metered flow rates- V··]* ····a# · .being continuously and automatically adjusted to maintain the desired ratio. While open-loop systems are relatively simple, closed-loop systems are sophisticated, complex, and more expensive. An object of the present invention is to .......... provide a closed-loop control system which is simple, low-cost and reliable and which can be combined with an open-loop proportioning system. This object is achieved according to the invention by providing a proportioning device to be connected to a main line conveying a fluid under pressure for the purpose of introducing, or withdrawing, from said main line a fluid at a flow rate corresponding to an essentially constant proportion of the flow rate of said main line, said device comprising a housing, at least one opening of which is connected to said main line and another opening of which is connected to a proportioning branch line, further comprising aaa• ma aa aa · aa a aa aa ·aaa - 4 - mg· Barzanò & Zanardotuia valve arranged in said casing and capable of closing the passage of said fluid to and from said proportioning branch pipe, which» and « ···· the valve is mechanically connected to two bodies . J ··········* of resistance» the first of which is located in the per- * · · m *· · ··♦·*··· · • · 'a ····•eoe# ····♦· 9 « flow path of the main pipe» and the ·-···· · · * * ·*·* ·***: ·*·. • ee i__ ***** ·*·· ·· · « · • * MM second » in the flow path suitable for tu- ·:*·* ;**. *; · » ·• . **·» proportioning branch arrangement» with an *·.. / .**,·*effect such that the resistance force acting ····* on said first resistance body tends to open .·.*said valve and consequently to increase the flow through said proportioning branch» while the resistance force acting on said second resistance body tends to close said valve and consequently» to reduce the flow through said proportioning branch. Although the invention will now be described in connection with certain preferred embodiments with reference to the figures of the accompanying drawings for the purpose of a better understanding of the invention, it is noted that the particulars shown and described are given by way of illustrative example only in order to give a more useful and comprehensive description of the fundamental principles of the invention. In this regard noshown structural details of the 5 - · Xng· Barsanò ft Zanardo devices and their elements more than is necessary to dispute the basis of the invention. The description together with the attached drawings will enable those skilled in the art to understand how to implement the various embodiments of the invention in the drawings; Figure 1 is a schematic cross-sectional view of an embodiment of the proportioning device according to the invention arranged to draw a proportional flow rate from the main pipe. Figure 2 is an identical view of the same embodiment arranged to introduce a proportional flow rate into the main pipe. Figure 3 is a partially edematous cross-sectional view of another embodiment of the proportioning device arranged to take a proportional flow rate from the main pipeline;Figure 4 is an enlarged cross-sectional view of the valve used in the device of Fig. 3. Figure 5 is a partially schematic cross-sectional view of the embodiment of Fig. 3 arranged to introduce a flow rate of 9m. • · · - € - lag· Bar sanò à zanardo proportional to the main pipe; Figure 6 is a cross-sectional view, on an enlarged scale, of the valve used in the device of Fig. 5. Fig. 1 shows a valve 2 mounted in a tubular casing 4 and rotatable about an axis 6 in the position shown. The size of the valve is such that it completely closes the free cross-section of the casing 4. The valve 2 in this form of construction is a butterfly valve. However, other types of valves may also be used, for example cylindrical or spherical valves. One side of the casing 4 is screwed tightly into a socket 8 which opens into the main pipe 10. The other side is screwed tightly into an elbow 12, into the other end of which the proportioning branch 14 is screwed. A rod 16 is rigidly connected to one side of the valve 2 and extends into the main pipe 10. At its end is a resistant body 17, consisting, in the embodiment shown, of a sphere. A similar rod 18 is connected to the other side of the valve 2 and extends into the elbow 12. The end of this rod 18 is connected by means of a swivel joint 19, which allows its rotation. • 4 · 4 .·«·· 7 Ing, Barzanò & Zanardo rotation around the rod 18 in a plane perpendicular to the end of the rod 18, for a purpose that will be explained later, a rod 20 which carries at its end another resistant body 22, also spherical. In the assembled condition of the device, as shown in Fig. 1, the resisting body 17 is located and influenced by the flow in the main pipe, and the resisting body 22 is located and influenced by the flow in the main pipe. driven by the flow in the proportional branch - ....I .· · ment 14» ****! • eoe* The operation of the device shown in Pig 1 is as follows: the flow in the main pipe 10 is from left to right, as indicated by the arrow 24 and, impacting on the resistant body 17, exerts on it a force which, as a moment around the axis 6, causes the butterfly valve 2 to rotate clockwise and consequently in the opening direction. The fluid now passes the valve 2 and, through the elbow 12, enters the proportional branch 14 in the direction of the arrow 26, where it meets the resisting body 22, exerting on it a force which equally translates into a moment about the axis 6. This moment, however, is counterclockwise, opposite to the effect of the flow in the · *!· eoe · - 8 - Ing. Bar sanò & Zanardo main pipe and tends to close valve 2· Since 1 two resisting bodies 17 and 22 in this size and same form of execution are of the same / configuration, and the resisting force is consequently (within practical limits) a function of the flow velocity, and ***·*. since, furthermore, the two moment arms are esseq-e<· »·*** • ••If the valve 2 is of the same length, the opposing moments acting on the valve 2 will be in equilibrium when the flow velocity in the branch pipe 14 is equal to that in the main pipe 10. The valve 2 will consequently be opened only to the extent required for the flow velocity impinging on the resisting body 22 in the branch pipe equal to the flow velocity impinging on the resisting body 17 in the main pipe, at which instant the two moments will exactly counterbalance each other and the valve 2 will remain stationary. Since the respective diameters, i.e. the cross-sections of the main and branch pipes are known, the ratio: flow main pipe / flow branch pipe will be equal to the ratio: cross-section main pipe / cross-section branch pipe, provided that, as mentioned above, the two resisting bodies • · .__ -9 - Ine* Barzanò & Zanardo are 0 and 22 / of the same size and the two branches are of the same length* If now for some reason the flow rate and consequently the flow velocity of the main pipe increases, the resistance force on the pipe increases; - ···· resisting body 17 will also increase, causing the valve opening moment to increase. This will also increase the flow in the branch pipe 14, resulting in a greater resistance force on resisting body 22, which will stabilize the position of valve 2 at the instant when the two flow velocities are equal again, i.e. the original flow rate ratio is restored again. With a drop in the main pipe, the resistance force acting on resisting body 17 will also drop, allowing the resistance force on resisting body 22 to close the valve sufficiently to again compensate for the two flow velocities.··♦· • * • · · **** • · • · ····· ·· / • · * · · · ····* · ·• * · ·. In order for the moments acting on valve 2 to depend only on the respective resistance forces acting on the resisting bodies, valve 2 itself must be insensitive to pressures from both sides which tend to alter the angular position - 10 - Big Bar sanò & Zanardo of the valve 2. the proportioning ratio of a main pipe of a given diameter can be changed by varying one or more of the following parameters: a) the relative dimensions of the resisting bodies 17 and 22: the larger the relative dimension of the resisting body 17, the smaller the proportioning ratio; b) the relative lengths of the moment arms of the resisting bodies 17 and 22: the larger the moment arm of the body .«..* resistant 17» the smaller the proportioning ratio; c) the cross-section of the proportioning branch 14: the larger the flow cross-section of the branch pipe 14» the larger the proportioning ratio. The resistant bodies 17 and 22 can have different shapes» for example cylindrical» flat» conical» pear-shaped» prismatic» cup-shaped» etc.* The mechanical coupling joint between the resisting bodies and the valve can also be made in the form of a belt, chain, gear or similar transmission. Fig. 2 shows the proportioning device according to Fig. 1 but arranged to introduce into the main pipe 10 a proportional flow rate from the proportioning branch 14. Such an arrangement is used, for example, to introduce a liquid fertilizer into an irrigation pipe and a certain ratio which must be maintained independent of fluctuations in the flow rate delivered, or to introduce a disinfectant such as chlorine or similar into the main pipe; in which case maintaining a constant mixing ratio is even more important. As can be seen in and Fig. 2# a proportioning device according to the ····.' ····* Fig. 1 p for withdrawing a flow at a given proportional ratio from a main pipe# can be easily converted into a device for introducing a flow at a given proportional ratio into a main pipe# by simply rotating the elbow fitting 12 180°. Here the purpose of the swivel joint 19 is evident: when the elbow fitting 12 is rotated 180°# the joint 19 allows the rod 20 with its resisting body 22 to participate in the rotation# ultimately assuming the position shown in Fig. 2. The operation of this arrangement of the device is analogous to the explanation relating to Fig. 1# except that the proportional flow now enters the elbow fitting in the direction of arrow 28# instead of in the direction of arrow 26# as in Fig. 1.- 12 - lag* Barzanò ft zanardoThe embodiments shown in Figs. 3 to 6 can also be used with liquids» but are particularly suitable for gases due to the fact that the two resistant bodies 17 and 22 are located in different spaces, these spaces communicating through the space y. eoe# and 30 and are consequently at equal pressure» unlike the embodiment shown in Figs. 1 and 2» V···*. In which the resistant body 22 is located on the other side of the valve 2» i.e.» under conditions of different pressures of the proportioning branch 14» although this would make no difference for liquids» which are incompressible. Fig. 3 shows an embodiment of the device according to the invention, particularly suitable for gaseous media and designed to draw a proportional flow rate from the main pipe. The casing 4 is shown in the figure, which is inserted into the main pipe 10 and is connected to it, for example, by means of flanges 32. The proportioning branch connector 14 is also shown, shaped for use with an elastic hose, although other means of connection are also possible. The Fig. 3 shows an embodiment of the device according to the invention, particularly suitable for gaseous media and designed to draw a proportional flow rate from the main pipe 10. The casing 4 is shown in the figure, which is inserted into the main pipe 10 and is connected to it, for example, by means of flanges 32. The proportioning branch connector 14 is also shown, shaped for use with an elastic hose, although other means of connection are also possible. and ·' • »· * and»·· »··· valve is of the sliding type and can be seen better in the enlarged cross-section in Fig· 4· The valve, as shown in Fig. 4, in the closed condition, is made up of a fixed element 40 preferably, but not necessarily integral with the branch connector 14, and of a sliding element 42 to which an actuating rod 44 is connected. The fixed element 40 is provided with a central axial hole 46 which opens on one side to the upper part β.G of the connector 14 and on the other side into a transverse hole 48 passing through the fixed element 40 and essentially along its diameter. A circular groove ! ····· the conference 50 is drilled to a shallow depth at the points where the hole 48 penetrates the surface of the fixed element 40,the width of said groove 50 is approximately equal to the diameter of the hole 48. The sliding element 42 has a sleeve-shaped portion which slides on the fixed element 40 and is provided with at least one hole 52 of diameter approximately equal to the diameter of the hole 48 and located at a point such that when the sliding element 42 is slid on the fixed element 40 to the permissible extent, the hole or holes 52 do not communicate with the groove 50. The other portion of the sliding element 42 is essentially smooth, except for a hole in which an actuating rod 44 is fixed to the press,and a small inclined hole 54 which extends from the outside to the lower part of the hole which houses the fixed valve element 40. The hole 54 is a relief hole which prevents the occurrence of stress forces due to possible valve leaks. The actuating member 44 is guided in a projection 56 in the form of a rib integral with the casing 4 or connected to it and which carries the resistant body 22 in the narrowest proportioning space 58 and at its free end the resistant body 17. An annular stop element 60 limits the axial movement of the actuating rod 44. The operation of the device shown in Fig· 3 is as follows; The fluid flowing in the direction of the arrows 24 enters the mixing space 30 and, assuming the valve at this stage is in the closed position as shown, continues to flow to the left when it impinges on the resisting body 17, exerting a tensile force on the actuating member 44. This tensile force moves the sliding element 42 of the valve from the position shown in Fig. 4 in which there is no communication between the holes 52 and 48 to a position in which communication is established, at which time the fluid from the mixing space can enter the holes 52 and pass into the annular groove. • ····· ♦ ·• * ♦ **· * • »• * ···» * > • » • · · #· • ·· * * % * ·• · · • ·· · ··· — 15 — lag. Barzanò & Zanardo <50 and from there, through the holes 48 and 46 in the branch of proportional space 14» in the direction of the ··*· • and arrow 26* The fluid in the space of proportional space 58 having started to move, is now dared»·ΓΓ • · ^ and ··»· a resistance force is exerted on the resisting body 22 ;··;·. · ; ;* μ·. which, transmitted to the actuating rod 44, tends to close the valve. A state of equilibrium is reached when the valve opening forces acting on the resisting body 17 and the valve closing forces acting on the resisting body 22 compensate each other.Since the resisting bodies 17 and 22 are of equal size and configuration, such a state of equilibrium will be obtained when the velocities around the resisting bodies are equal. At that instant, the proportional ratio: flow rate in main pipe / flow rate in branch pipe will be equal to the ratio: cross-section of main pipe / cross-section of proportional space. Fig. 5 shows the embodiment illustrated in detail in Fig. 3, but arranged to introduce a proportional flow in the main pipe 11, in the direction of the arrow 28. The structure of this embodiment is analogous to that shown in Fig. 3, the principal difference being the relative position of the holes 52 and 48 in the sliding element 42 and the fixed element 40 of the valve respectively. While in the extreme lateral position in the shown in Figs. 3 and 4 holes 52 and 48 are not in the same extreme position of the valve *···« r*:· ··*· "I. J*·· • • 2*** vi***· *···* * · J» • * · • memo ···· ··. ····* e • *·* ···· • · a : • · ···*· • a · • .* ** * **·· ···*• * · • · ·· · · so in the main pipe the vai-.··.; ····* flies and the flow in the branch tends to close the valve. It is evident that the valve can also assume other shapes, provided that care is taken to prevent the occurrence of axial stress forces that could interfere with the equilibrium of the two opposing resisting forces. While in the embodiments of Figs. 3 and 5 the three moving elements: resisting body 17, resisting body 22 and sliding element 42 are rigidly connected by the actuating rod 44, other coupling means could be used to alter their travels and relative speeds, in order to increase the sensitivity of the device. It is also obvious that, as in the embodiment shown in Figs. 1 and 2, the resisting bodies can assume various shapes other than the disc-shaped one shown.