Varying the hydraulic resistance in a pressure pipe
United States Patent n9 Denizov et a].  
 [451 Apr. 29, 1975 1 VARYING THE HYDRAULIC RESISTANCE IN A PRESSURE PIPE [76] Inventors: Anatoly Alexeevich Denizov, ul.  
 Rubinshteina, 36, kv. 49; Vladimir Stepanovich Nagorny, ul. Novo-Litovskaya 5, kv. 24, both of Leningrad, USSR.  
 [22] Filed: July 17, 1972 [21] Appl. No.: 272,665  
 [52] U.S. Cl 137/827; 137/13 [51] Int. Cl. FlSc H04 [58] Field of Search 137/827, 251, 13  
 [56] References Cited UNITED STATES PATENTS 3,071,154 H1963 Cargill [37/827 X Horton 137/827 X Dexter 137/251 Primary E.raminerAlan Cohan Assistant E.\aminerGerald A. Michalsky [57] ABSTRACT 2 Claims, 5 Drawing Figures I I V L,.  
 VARYING THE HYDRAULIC RESISTANCE IN A PRESSURE PIPE The invention relates to electro-hydraulic converters and more particularly to an electro-hydraulic converter and a method of controlling it.  
  The invention may prove particularly helpful for drive control purposes, in electro-hydraulic automatic systems, etc.  
  Known in the art are methods of controlling hydraulic mechanisms in electro-hydraulic drives, based on the variation of the hydraulic resistance in a pressure pipe through which a working liquid, e.g. mineral oil, is fed to an actuating mechanism, e.g. a piston and hydraulic cylinder.  
  Constructions for the realization of these known methods of controlling electro-hydraulic mechanisms include such as, for instance, devices of the nozzleshutter&#34; type or a slide-valve device.  
  The nozzle-shutter&#34; device provides for variations in the liquid pressure at its outlet by way of displacing the shutter relative to the nozzle. As a result, the hydraulic pressure in this section will be changed, resulting in changed pressure of the liquid at the outlet.  
  With the use of a slide-valve device for controlling the hydraulic mechanism, variations in the hydraulic resistance are achieved due to a partial obstruction of the liquid flow passage by the slide-valve plunger.  
  Both in the slide-valve and the nozzle-shutter&#34; devices, the plunger and the shutter respectively are actuated by an electric drive.  
  Consequently, the known constructions are characterized by multiple transformations of energy. Electric power fed to an electric drive is transformed into mechanical energy of the moving parts of the converters and thereafter into the energy of liquid pressure, i.e., an electric control signal is converted into a mechanical one, and the latter into an output hydraulic signal of the converter.  
  The known constructions of the converters suffer from a number of disadvantages, the basic of which is the presence of moving mechanical members, which considerably affects the reliability and speed of the converters and their control, and makes the entire design of the units more complicated.  
  Moreover, the so-called obliteration is not rare to develop in slide-valve devices, as a result of which the effort required to move the slide-valve plunger tends to increase many fold, which in its turn imposes increased demands on the electric drive in such devices, necessitating greater dimensions of the latter.  
  The primary object of the invention is to provide such a method of changing the hydraulic resistance in a pressure pipe, as would ensure direct transformation of electric energy into an output hydraulic signal, as well as an electro-hydraulic converter operated on that method and exempt from moving mechanical members.  
  This object has been accomplished by provision of the proposed electro-hydraulic converter whose control consists in that the liquid flow is charged with static electricity in a section where hydraulic resistance is established and an electric field is thus induced, interacting with the flow of the charged liquid so that any change in the field intensity will result in changed flow conditions.  
  It is expedient that the charging of the liquid with static electricity be effected by way of friction against a dielectric when said liquid is flowing around it.  
  The electrohydraulic converter for the realization of the proposed method comprises a housing with inlet and outlet branch pipes communicating with each other through a channel for the passage of liquid and a device for varying the hydraulic resistance of the liquid in the pressure pipe section.  
  According to the invention, the device for varying the hydraulic resistance is fashioned as outer and inner electrodes connected to the respective poles of a DC. source, and a liquid charging element, the converter housing serving as the outer electrode, while the inner electrode and the liquid charging element are disposed in the housing so as to form said channel for the passage of liquid between them and the housing.  
  Such construction of the converter is exempt from any moving mechanical members; as a result, it is compact and reliable in operation.  
  The proposed method of control of the above converter is characterized by the fact that the electric control signal is transformed directly into an output hydraulic signal, thus increasing the speed of the converter operation.  
  In one of the exemplary embodiments of the converter, its inner electrode is fashioned as a metal cylindrical rod with notches on its rounded butt ends, spaced uniformly on the outer periphery of said butt ends and accomodating the threads of the liquid charg ing element therein, said rod being mounted in the housing on dielectric sleeves provided with slots for the passage of liquid.  
  Such converter can be built into a pressure pipe section without extending beyond its size. With the converter electrodes being connected to a DC. source, an electric field is set up between them, whose strength depends upon the voltage and spacing between the electrodes. In its turn, the liquid flowing over the surface of the inner electrode, whereon the threads of the liquid charging element are accomodated, acquires a charge of static electricity as a result of its friction against said threads.  
  As a result of the interaction of the electric field with the flow of the charged liquid, its flow conditions will be changed, resulting in a different hydraulic signal of the converter.  
  Another exemplary embodiment of the invention provides for a dielectric rod, rigidly fastened, inside the converter housing, with diametrically opposite rectangular grooves along its trajectories, the inner electrode being fashioned as a metal band accomodated in said grooves and carrying the threads of the liquid charging element, said metal band being in contact with a metal rod inserted in a hole provided in one of the butt ends of the dielectric rod.  
  Experimentally it has been found, that the flow rate through circular slots is much lower than that through rectangular slots. In the particular case, serving as a channel for the passage of liquid inside the converter are the rectangular slots provided in the dielectric rod secured inside the housing. Therefore, the converter of such design can be utilized in pipelines with a relatively high flow rate.  
  Physically, the essence of the proposed method consists in the following. In case of the absence of an input electric signal across the converter, a laminar liquid flow is observed in the channel of the converter housing, said flow being characterized by Reynold&#39;s number Re 2300v Pressure differential in this section is expressed by equation:  
  l 2 l n where P, and P serve to indicate the liquid pressure at the converter inlet and outlet, respectively;  
 K stands for the proportionality factor which depends upon the kind of liquid and the construction parameters of the converter; and  
 V is the liquid flow velocity.  
  In case of the presence of an input signal across the converter, an electric field is set up between the electrodes, which leads to flow turbulization, while the pressure differential in the converter tends to rise.  
 P P2 K V,  
 where K is the proportionality factor; and a is a factor characterizing the degree of flow turbulization, l a 2.  
 Consequently, the flow rate through the converter being constant, the pressure differential in it will rise whenever the input signal becomes stronger. The flow rate is maintained constant with the aid of a flow regu lator.  
  Following hereinbelow is a detailed description of exemplary embodiments of the invention, reference being had to the appended drawings, wherein:  
  FIG. 1 is a schematic diagram of an electro-hydraulic converter. longitudinal section;  
  FIG. 2 is an exemplary embodiment of the electrohydraulic converter, longitudinal section;  
 FIG. 3 is a section along line llllll, FIG. 2;  
  FIG. 4 is an exemplary embodiment of the electrohydraulic converter, longitudinal section;  
 FIG. 5 is a section along line VV, FIG. 4.  
  The electro-hydraulic converters of the proposed constructions can be built into a pipeline. Serving as a housing 1 (FIG. 1) of the converter is a pipe section of the same diameter as that of the main pipeline. Said housing 1 is connected with the pipeline by means of sleeves 2 and 3 made of a dielectric, e.g., organic glass. The housing 1 also serves as one of the converter electrodes. Further on, it will be referred to as the outer electrode. Arranged coaxially inside the housing 1 is the inner electrode 4 fashioned as a metal rod with rounded butt ends. it is secured in the housing 1 by means of network element 5 made of a dielectric and serving also as liquid charging elements. Besides, these network elements 5 insulate the outer electrode 1 from the inner electrode 4.  
  Thus, a channel is formed between the inner surface of the housing I and the inner electrode 4 for the passage of liquid, communicating the inlet 6 and outlet 7 branch pipes.  
  For connection of either of the electrodes 1 and 4 to a respective pole of a DC. source 8, the sleeves 2 and 3 are provided with holes to accomodate leads 9 and 10 contacting the electrodes 4 and 1, respectively.  
  Also provided in the converter there may be pressure gauges Ml-ll and M2-12 that serve to measure liquid pressures at the converter inlet and outlet, correspondingly.  
  In another exemplary embodiment of the converter its inner electrode 4, (FIG. 2) is made as follows. A metal rod with the rounded butt ends is secured coaxially in the housing 1 (FIG. 2) by means of sleeves 13 made of a dielectric and provided with circular slots for the passage of liquid.  
  Spaced uniformly throughout the periphery of the rounded butt ends of the electrode 4 are notches that accomodate the thread making up the liquid charging element 5. Said element 5 is made of a thread e.g., vinyl, wound along the lateral surface of the electrode 4 with a maximum possible tension. Owing to such a design, the converter offers a relatively small hydraulic resistance.  
  One more exemplary embodiment of the invention provides for a dielectric cylindrical rod 14 press-fitted in the housing 1 (FIG. 4). Arranged diametrically opposite along the trajectories of this rod 14 are rectangular grooves.  
  A metal band designed as the inner electrode 4 is laid along the bottom of these grooves. Wound on top of said band in the same grooves are the threads of the liq uid charging element 5. One of the butt ends of the dielectric rod 14 has a hole wherein a metal rod 15 contacting the inner electrode 4 is inserted. in such exempiary embodiment, the rectangular grooves made in the dielectric rod 14 serve as the channels for the passage of liquid. It has been established experimentally that the flow rate through the rectangular slots is several times higher than that through the circular slots with the same clear section; therefore, the proposed converter can be used at relatively high flow rates.  
  The converter operates in the following way. With the electrodes 1 or 4 connected to a respective pole of a DC. source, an electric field is set up between said electrodes 1 and 4. The liquid is fed to the inlet branch pipe 6 of the housing 1 and therefrom to the liquid flow channel provided between the inner surface of the housing 1 serving as the outer electrode and the inner electrode 4.  
  The flow conditions are laminar, i.e., characterized by Reynolds number Re 2300.  
  While flowing between the electrodes 1 and 4, the liquid is contacting the charging element 5. As a result of friction against the dielectric, the liquid acquires an electric charge whose value depends upon the type of the liquid and the material of the element 5.  
  The field intensity between the electrodes 1 and 4 reaches 5.10 V/m. In general, the former depends upon the voltage and spacing between the electrodes.  
  The charged liquid interacts with the electric field and, as a result, its flow conditions become turbulized. At such flow conditions, losses necessary to overcome the hydraulic resistance of the converter become greater and the pressure P, at the converter inlet rises. By varying the field intensity it is possible to control the extent of the flow turbulization and, consequently, obtain a hydraulic signal with a preset value at the converter outlet.  
  The value of the output hydraulic signal depends upon the parameters of the converter as follows:  
 V is the liquid flow velocity at U O;  
 l is the length of the liquid flow channel in the converter;  
 5 is the distance between the electrodes;  
 U is the voltage across the converter electrodes; and  
 K is the proportionality factorv Consequently, with the given design parameters of the converter and the voltage across the electrodes 1 and 4, it is possible to increase the output hydraulic signal, raising the speed of the liquid flow through the converter.  
  The converter of the proposed design and operating principle is characterized by high speed and reliability of operation, as it is exempt from any moving mechanical members What we claim is:  
  1. An electro-hydraulic converter for varying the hydraulic resistance of liquid in a pressure pipe section, comprising a housing with inlet and outlet branch pipes; said housing being the outer electrode of the converter, the inner electrode being accomodated inside said housing; a DC. source connected with respective poles to said outer and inner electrodes; a liquid charging element enclosed in said housing, said inner electrode being arranged inside said housing so as to form a liquid flow channel therebetween and communicating with the inlet and outlet branch pipes of said housing, said outer and inner electrodes being connected to respective poles of said D.C. source and comprising together with said liquid charging element, a device for varying the hydraulic resistance of the liquid in a pressure pipe section; a dielectric rod secured rigidly in said housing and having diametrically opposite rectangular grooves along its trajectories, said inner electrode being a metal band arranged on the bottom of the grooves in said dielectric rod; threads of said liquid charging element laid on top of the metal band in the grooves of said dielectric rod; and a metal rod inserted in a hole in one of the butt ends of said dielectric rod and being in contact with said inner electrode.  
  2. An electro-hydraulic converter for varying the character of a flow of liquid under the influence of an input electric signal, comprising a housing with inlet and outlet connection pipes interconnected by a channel for the passage of said liquid; means for varying the hydraulic resistance comprising a direct-current source and electrodes connected to respective terminals of said direct-current source; means for electrically charging the liquid and located inside said housing. said housing serving as the external electrode of said converter; an inner electrode located inside said housing; a dielectric rod securely fixed inside said housing and provided with diametrally located rectangular slots extending along the axial length thereof, said inner electrode being a metal band placed at the base of said slots of said dielectric rod, said means for charging the liquid being in the form of dielectric threads placed over the metal band in the slots of said dielectric rod; a metal rod inserted in an opening made in one of the ends of said dielectric rod in contact with said inner electrode, said inner electrode with said means for charging the liquid defining, together with the walls of said slots of said dielectric rod and of said housing, said channel for the passage of said liquid, said channel being a pressure pipe section.