RU2454574C2 - Digital steering gear - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: gear includes hydraulic cylinder with outlet stock, digital-to-analogue drive having housing inside which there located in series are several discharge pistons being engaged between each other, and the same number of electric hydraulic converters which connect cavities of discharge pistons either to control pressure header, or to drain header, spool - hydraulic valve providing the supply of control pressure to hydraulic cylinder, position sensor of outlet stock, fixing device of outlet stock, device for attaching the housing of hydraulic cylinder and outlet stock to the appropriate mounts of liquid-fuel rocket engine, as well as supply and discharge connections of control pressure to digital steering gear; at that, hydraulic cylinder, spool - hydraulic valve and discharge pistons of digital-to-analogue drive are located on one and the same axis; at that, housing of hydraulic cylinder is rigidly and tightly attached to housing of digital-to-analogue drive; spool - hydraulic valve has control cavity which is connected to control pressure header, made in the form of hollow cylinder with solid bottom and installed inside piston of hydraulic cylinder; the above spool is engaged with senior-grade piston and with piston of hydraulic cylinder, and moves inside it within gap δ, and its travel is restricted with a nut, and the following is made in its wall: pressure cavity, two drain cavities; at that, control cavities of hydraulic cylinder depending on movement of spool - hydraulic valve can be connected to pressure cavity or to drain cavities via the channels made in hydraulic cylinder piston; besides, drain cavities are interconnected with inlet cavity of flow stabiliser which is rigidly attached to spool - hydraulic valve; at that, cavities of discharge pistons are connected to drain header or control pressure header via hydraulic lines in which there installed are electric hydraulic valves (for cavities of smaller-grade pistons) and hydraulic lines in which there in series installed are electric hydraulic valves and hydraulic valves of amplification for cavities of medium- and senior-grade pistons.

EFFECT: improvement of quick action of working devices of gear.

7 cl, 9 dwg

Description

The invention relates to the field of engineering, and in particular to digital steering gears, designed to deflect the chambers of liquid rocket engines with the aim of creating control moments relative to the center of mass of the launch vehicle for motion control.

State of the art

A known digital drive containing a casing, a return electromagnet and electromagnets with cores of reciprocating motion, the number of which is equal to the number of bits of the binary number, and the air gaps between them are equal to one, two, four, etc. units (see ed. certificate of the USSR No. 185118, MKI F15B 9/17, 1966). This technical solution is taken as an analogue of the invention. This technical solution is workable and has good reliability.

However, such drives are unlikely to find application in rocketry due to the increased mass and low speed. Such digital drives are used in low-power control systems.

Also known is a digital steering gear for controlling the thrust vector of a liquid propellant rocket engine.

The specified digital converter includes a hydraulic cylinder with an output rod, a digital-to-analog drive having a housing inside which seven digit sliding pistons, seven electro-hydraulic converters are arranged in series, which convert the electrical command signals from the control system, which are set in the form of a seven-digit binary code to the translational movement of the rod. The driving elements of the digital analog converter are seven magnetoelectric converters that connect the cavities between the discharge pistons, depending on the command signal, either with discharge or with discharge. In addition, the control spool is included in the design of such a drive, which, depending on the movement of the digital-to-analog converter rod and feedback levers, provides a supply of working fluid to the hydraulic cylinder. There is also a clamp for the output rod, means for mounting the drive to the corresponding nodes of the liquid rocket engine, a rod position sensor and nozzles for supplying and discharging the working fluid (see the technical description of the RD-170 liquid rocket engine under the general editorship of B.I. Katorgin, p. 54-57, 1995). This technical solution is taken as a prototype of the invention.

Despite the proven operability and reliability of the prototype, its high mass and cost, the complex hydromechanical connection between the primary digital-to-analog converter and the hydraulic cylinder can be considered a disadvantage. In addition, in the prototype, as a digital-to-analog converter, low-power electromagnetic devices of the nozzle-damper type are used, which do not provide the necessary hydraulic amplification and the necessary rod code and require the next several cascades of hydraulic amplification both in amplification and in the course of the rod with the necessary complex reverse connections for this case .

Disclosure of invention

The basis of the present invention is the creation of a digital steering gear for controlling the thrust vector of a liquid propellant rocket engine having a lower mass, relatively low cost and simple layout of the drive.

This problem is solved due to the fact that in a digital steering drive that includes a hydraulic cylinder with an output rod, there is a digital-to-analog drive having a housing inside which several discharge pistons are arranged in series with each other, and as many electro-hydraulic converters that connect the cavity of the discharge pistons either with a control pressure manifold or with a drain manifold, a spool-valve, providing a supply of control pressure to the hydraulic cylinder, an output position sensor th rod, output rod retainer, means for fastening the cylinder body and the output rod to the corresponding units of the liquid propellant rocket engine, as well as supply and outlet control pressure pipes to the digital steering gear, while the hydraulic cylinder, the spool valve and the digital-to-analog drive pistons are located on one axis, and the cylinder body is rigidly and hermetically connected to the body of the digital-to-analog drive, the spool valve has a control cavity that is connected to the collector m of control pressure, made in the form of a hollow cylinder with a blind bottom and installed inside the piston of the hydraulic cylinder, the specified spool is meshed with the piston of the highest category and the piston of the hydraulic cylinder and moves inside it within the gap δ, and its stroke is limited by the nut, and in its wall made: a pressure cavity and two discharge cavities, while the control cavity of the hydraulic cylinder, depending on the movement of the spool valve, can be connected to the pressure cavity or to the drain cavities through channels made in pores not the hydraulic cylinder, in addition, the drain cavities communicate with the inlet cavity of the flow stabilizer, which is rigidly connected to the spool-valve, and the cavities of the discharge pistons are connected to the drain manifold or to the control pressure manifold through hydraulic lines in which electrohydraulic valves are installed (for control cavities of smaller pistons ) and hydraulic lines in which electrohydraulic valves and amplification hydraulic valves for piston cavities of medium and higher discharge are installed in series.

Other features of the proposed digital steering gear are:

- the electrohydro valve has an electromagnet and a shutter, which includes a spool and a sleeve, while two control cavities and a drain cavity are made in the sleeve, one of the control cavities being connected to the control pressure manifold, and the second connected to the first control cavity and to the cavity when the spool is moved piston (s) of lower discharge;

- the amplification hydraulic valve has a piston and a shutter that includes a spool and a sleeve, while two control cavities and a drain cavity are made in the sleeve, one of the control cavities being connected to the control pressure manifold, and the second connected to the first control cavity when the spool is moved the line is connected to the piston cavity (s) of a larger discharge, in addition, the spool is integral with the piston, and its diameter is smaller than the diameter of the piston, and the piston control cavity is hydraulically connected to tapping cavity of the electrohydrovalve;

- each engagement element of the discharge pistons has a L-shaped cross section;

- the flow stabilizer has a housing containing an inlet cavity and a cavity of reduced pressure, separated by a partition in which throttle openings are made, said housing having a cover inside which a spring-loaded sensing element with a supporting surface is located, in addition, between the sensing element and the flow stabilizer housing control gap, the outlet of which is connected to the drain pipe, and the annular cavity in which the sensing element is located is connected to the inlet cavity flow abilizer;

- the position lock of the hydraulic cylinder rod has a body and a cavity that is hydraulically connected to the control pressure manifold, a cover, a spring-loaded hollow rod and a pin, while the rod is connected to the pin with a screw, in addition, a U-shaped groove is made in the end of the pin, interacting with an annular protrusion made on the rod of the hydraulic cylinder.

The technical result consists in simplifying the layout of the drive, reducing weight and its cost.

Brief Description of the Drawings

Figure 1 shows a longitudinal section aa of a digital steering gear;

figure 2 presents a view of In;

figure 3 presents a fragment I of an enlarged section of part of a longitudinal section of figure 1;

in Fig.4, Fig.5 presents fragments II and III of enlarged sections of the electrohydrovalve and its connection with the cavities of the discharge pistons;

figure 6 presents a fragment IV of an enlarged section of a reinforcement hydraulic valve;

figure 7 presents a section along BB in figure 4;

on Fig presents fragment V of an enlarged section of the spool valve;

figure 9 presents a fragment VI of an enlarged section of the rod position lock.

An example implementation of the invention

The design of the proposed digital steering gear is seven-digit. Seven digits in total provide 128 combinations of stem positions, with a discrete increment of the stroke in increments of 1/128 from a given range of these parameters. The digital steering gear 1 (FIG. 1) includes a hydraulic cylinder 2 with a stem 3, a digital-analog drive 4 and a spool valve 5. An earring 6 is fixed to the end of the stem 3, with which the stem 3 is attached to a rocking chamber of a liquid-propellant rocket engine (not shown). The housing 7 of the hydraulic cylinder 2 is firmly connected to the housing 8 of the digital-analog drive 4 and are located on the same axis O'-O '. A bracket 9 is attached to the bottom of the housing 8, with which the drive is attached to the frame of a liquid propellant rocket engine (not shown).

The actuator design includes: a position sensor 10 of the rod 3, a latch 11 of the position of the rod 3, a pipe 12 for supplying control pressure and two discharge pipes 13 and 14. Along the circumference of the housing 8 are located (Fig. 2, view B) seven electrohydro valves 15 and five amplification hydraulic valves 16.

In the digital-analog drive (Figure 3), seven discharge pistons 17, 18, 19, 20, 21, 22, 23 and the same number of cavities 24, 25, 26, 27, 28, 29, 30 are used. A control pressure manifold is located inside the housing 8 31 and a drain manifold 32. The control pressure manifold 31 is hydraulically connected to the control pressure pipe 12, and the drain manifold 32 is connected to the discharge pipe 14. Electrohydraulic valves 15 and amplification hydraulic valves 16 are used to connect the discharge piston cavities to the control pressure manifold 31 or to the drain manifold 32 .

The design of each discharge piston is selected in such a way that each such piston, when it moves, engages with an adjacent discharge piston, moving by an amount different from the relative displacement of the adjacent discharge piston by half.

Each engagement element of 33 bit pistons is made in one piece with the bit piston and has a L-shaped cross section.

Each electrohydrovalve 15 (FIG. 4) is controlled by an electromagnet 34 and has a spool 35 and a sleeve 36. The spool 35, under the action of a spring 37 or a rod 38, can move in the axial direction. This valve has two control cavities 39, 40 and a discharge cavity 41. The control cavity 39 is in communication with the control pressure manifold 31. The discharge cavity 41 is in communication with the drain manifold 32 through the radial channels 42 and the axial channel 43. The control cavity 40 (FIG. 5) through the radial channel 44 and the longitudinal channel 45 and channel 46 are in communication with the cavity 25 of the piston 18 of the lower discharge (Figure 5). Similarly, the control cavity of the second electrohydrovalve 15 through the same channel (not shown), made in the housing 8, is in communication with the cavity 26 of the second piston 19 of the lower order. The control cavities of the remaining five electrohydro valves 15 communicate with the cavities of the discharge pistons of the following discharges through amplification hydraulic valves 16.

Each reinforcement hydraulic valve 16 (FIG. 6) is controlled by a piston 47, which is located in the control cavity 48. The piston 47 is integral with the spool 49, while the diameter of the piston is larger than the diameter of the spool. The spool 49 can move in the axial direction due to the force created by the control pressure acting on the difference between the cross-sectional areas of the piston 47 and the spool 49. The amplification hydraulic valve 16 also has two control cavities 50, 51 and a drain cavity 52. The control cavity 50 is in communication with the control pressure manifold 31, and the drain cavity 52 is in communication with the drain manifold 32. The control cavity 51 through the longitudinal channel 53 of a larger diameter (Figure 3) is connected with the cavity 29 of the discharge piston 22. In addition, the control cavity 51 when moving the spool 49 of the hydraulic valve 16 to the left is connected to the discharge cavity 32 through channels 54 made in the body of the valve 49. The control cavity 48 of the hydraulic valve 16 communicates through the longitudinal channel 55 with the control cavity 40 of the electrohydro valve 15 (Fig. 7, section BB in Fig. 4). Cavities 26, 27, 28 and 30 of the discharge pistons 19, 20, 21 and 23 are connected to the control pressure manifold 31 or to the drain manifold 32 through four hydraulic lines in which the electrohydrovalve 15 and the amplification hydraulic valve 16 are connected in series.

The control valve 5 (Fig. 8) has a control cavity 56, is made in the form of a hollow cylinder with a blind bottom 57 and is installed inside the piston of the hydraulic cylinder 2. The control valve 5 is engaged with the piston of the highest category 23 and with the piston 58 of the hydraulic cylinder 2. -distributor 5 moves inside the piston 58 within the gap δ, limited by the nut 59. The piston 58 is rigidly connected to the rod 3 (Figure 1). The spool valve 5 has a pressure cavity 60 and two discharge cavities 61 and 62. The control cavities 63 and 64 of the hydraulic cylinder 2, depending on the movement of the spool valve 5, can be connected either to the pressure cavity 60 or to the drain cavities 61 and 62, through channels 65 and 66, made in the piston 58. The control cavity 56 of the control valve 5 through the longitudinal channel 67 communicates with the manifold 31 of the control pressure (Fig.Z). The drain cavity 61 and 62 through the longitudinal channel 68 communicate with the input cavity 69 of the flow stabilizer 70.

The housing 71 of the stabilizer 70 is located in the inner cavity of the stem 3 and is rigidly connected to the spool-valve 5. In the housing 71 of the stabilizer 70 is a cavity of reduced pressure 72. The inlet cavity 69 and the cavity of reduced pressure 72 are separated by a partition 73 in which throttle openings 74 are made. C the other side of the stabilizer body is fixed cover 75.

In the inner cavity 76 of the lid 75, a sensing element 77 movably mounted in the form of an elongated glass is movably mounted. A sleeve 78 is mounted on the outer surface of the sensing element 77, having a support collar 79. A spring 80 is placed between the collar 79 and the flow stabilizer body 71. The inlet cavity 69 communicates with the inner cavity 76 of the cover 75 through a longitudinal channel 81 made in the stabilizer body 71. A regulating gap 82 is formed in the stabilizer body 71, which is formed by the conical surface 83 of the body 71 and the sharp edge 84 of the sensor 77. The regulating gap 82 connects the reduced pressure cavity 72 to the annular cavity 85 formed between the cylindrical surfaces of the rod 3 and the flow stabilizer body 71. This the cavity is in communication with the discharge pipe 13 (Figure 1).

In the housing 7 of the hydraulic cylinder 2, a latch (FIG. 9) of the position 11 of the rod 3 is installed. A cavity 87 is made in the cylindrical housing 86 of the latch 11, which is connected through a hole 88 made in the wall of the housing 86 to the tube 89. The other end of this tube is connected to the collector control pressure 31. The cylindrical housing 86 of the clamp is closed by a cover 90. Inside the cylindrical housing 86 a hollow rod 91 is movably mounted having a flange 92. A spring 93 is installed between the flange 92 and the cover 90. A cylindrical pin 94 is also installed inside the housing 86 of the clamp It is connected by a screw 95 to a hollow rod 91. A U-shaped groove 96 is made at the end of the pin 94, and annular grooves 97 and projections 98 are made on the outer surface of the output rod 3 of the hydraulic cylinder 2. When the rod 3 is fixed, the U-shaped groove 96 of the check 94 included in the annular protrusion 98.

The movement of the rod 3 is fixed by the position sensor 10 located on the housing 7 of the hydraulic cylinder 2. The rod of the position sensor through a half ring is connected to the rod 3 (not shown).

The presence in this invention of a hydraulic cylinder with the specified piston made it possible to perform the simplest layout of a digital steering gear. The use of electro-hydraulic and amplification hydraulic valves instead of electromagnetic converters in this drive design made it possible to increase the speed of the drive working units due to the increased flow of control fluid supplied to the cavity of the discharge pistons.

In addition, the proposed design of the digital steering drive allows you to abandon the units that control external and internal feedback, providing stabilization of the control pressure, from oil systems and maintenance of drives in the launch vehicle.

Device operation

Before starting a liquid rocket engine, the hydraulic system of the digital steering gear is connected to the input and output of a centrifugal pump of a fuel turbopump. In this case, the internal cavity of the steering gear and the cavity of the fuel liquid rocket engine are evacuated, and then filled with fuel - kerosene. At this time, the output rod 3 is in the middle position and is fixed by the pin 94 of the position lock 11. The electromagnets 34 of the electrohydro valves 15 are de-energized.

The deflection of the LRE chambers is carried out in accordance with the electric commands supplied to a number of electromagnets of the electrohydro valves 15 corresponding to the average position of the rod 3. When the pressure increases in the control cavity 87 of the position lock 11 of the rod 3 (Fig. 9), the check 94, overcoming the force of the spring 93, leaves out of engagement with the output rod 3 (U-shaped groove 96 moves away from the annular protrusion 98).

To change the position of the output rod, an electric command is supplied to the corresponding electromagnets 34 of the electrohydro valves 15. In this case (FIG. 4), the rod 24 of the electromagnet 34 moves the spool 35, compressing the spring 37. This leads to the separation of the drain cavity 41 with the control cavity 40 and the message of the control cavity 40 with a control cavity 39, which in turn communicates with the control pressure manifold 31, while the drain cavity 41 through the radial channels 42 in the spool 35 and the axial channel 43 is connected to the drain manifold 32. Pos f this control pressure output from uprovlyat cavity 40 through the channels 44, 45 and 46 (Figure 5) is fed directly into the discharge cavity 24 of the piston 17 (piston of smaller discharge). Similarly, the cavity 25 of the discharge piston 18 also communicates with the control pressure manifold 31 through another electrohydrovalve 15 (not shown). In the cavity 26, 27, 28, 29 and 30 of the discharge pistons 19, 20, 21, 22 and 23, the control pressure from the manifold 31 enters through five autonomous hydraulic lines in which the electrohydrovalve 15 and the amplification hydraulic valve 16 are installed. So, for example, after the next of the electrohydro valve 10, the control pressure from the control cavity 40 enters the control cavity 48 (Fig. 7) of the amplification hydraulic valve 16. It should be noted that before that the control cavity 50 of the hydraulic amplification valve 16 is connected to the control pressure manifold 31. Since the diameter p of the piston 47 is larger than the diameter of the spool 49, then the spool 49 will move to the right due to the force created by the pressure of the working fluid acting on the difference between the cross-sectional areas of the piston 47 and the spool 49. As a result, the control cavity 50 is connected to the control cavity 51, which is through a longitudinal a larger section channel 53 (FIG. 3) communicates with a cavity 29 of the discharge piston 22. Similarly, when the following electrohydro valves 15 are installed in other hydraulic lines, the spools 49 of the other hydraulic valves move amplification 16. As a result, the control pressure from the cavities 51 will flow into the cavities 26, 27, 28 and 30 of the discharge pistons 19, 20, 21 and 23. As a result, a system of seven discharge pistons will shift along the O'-O 'axis up, moving the spool valve 5 within the gap δ, limited by the nut 59.

When the specified spool 5 is moved, the control pressure from the pressure cavity 60 enters the cavity 63 of the hydraulic cylinder 2 through the channel 66 made in the piston 58. At the same time, the other cavity 64 of the hydraulic cylinder 2 through the channel 65 made in the piston 58 communicates with the drain cavity 61, and this happens movement of the piston 58. From this cavity, the working fluid through the longitudinal channel 68 enters the inlet cavity 69 of the flow stabilizer 70. As a result, the piston 58 with the rod 3 will move until the seventh discharge closes piston 23 th and installing valve-control valve 5 to the neutral position.

The stabilization of the flow rate of the working fluid at the outlet of the control cavities 63 and 64 of the hydraulic cylinder 2 is as follows. The working fluid from the discharge cavity 61 through the channel 68 enters the inlet cavity 69 of the flow stabilizer 70, and from it through the throttling holes 74 made in the baffle 73, enters the cavity of the reduced pressure 72 and then through the control gap 82 enters the drain cavity 85, from where through the discharge pipe 13 is sent to the inlet of the fuel pump. At the same time, the working fluid from the inlet cavity 69 through the longitudinal channel 81 in the housing 71 enters the cavity 76. Since the hydraulic resistance between the cavities 69 and 72 is provided by throttling holes 74, a constant flow rate across them ensures a constant flow rate through the flow stabilizer 70. The differential value pressure is determined by the force of the corresponding amount of compression of the spring 80 divided by the effective area of the sensing element 77. When the pressure difference between the cavities 69 and 72 deviates to a large side, the sensing element 77, under the action of forces from the pressure differential acting on the effective area, moves, decreasing the control gap 82, determining the flow cross-section and lowering the flow rate through the flow stabilizer 70. When the pressure difference between the cavities 69 and 72 deviates to the smaller side, the sensitive element 77, moves, increasing the regulatory clearance 82, which leads to an increase in fluid flow through the stabilizer.

Thus, the presence of a flow stabilizer installed on the line for draining the working fluid from the cavities of the hydraulic cylinder, allows you to maintain a stable speed of movement of the rod 3 of the digital steering gear.

Industrial application

The proposed digital steering gear is simple in design, has less weight and low cost. The drive will find application in rocket technology to control the thrust vector of liquid rocket engines.

Claims (7)

1. A digital steering drive, including a hydraulic cylinder with an output rod, a digital-to-analog drive, having a housing, inside which several discharge pistons are arranged in series with each other, and as many electro-hydraulic converters that connect the cavities of the discharge pistons either to the control pressure manifold, or with drain manifold, spool-valve, providing control pressure to the hydraulic cylinder, output rod position sensor, output rod clamp, means for fastening the cylinder body and the output rod to the respective nodes of the liquid propellant rocket engine, as well as the supply and exhaust control pressure pipes to the digital steering gear, characterized in that the hydraulic cylinder, spool valve and discharge pistons of the digital-to-analog drive are located on one axis, while the housing the hydraulic cylinder is rigidly and hermetically connected to the body of the digital-to-analog drive, the spool-valve has a control cavity, which is connected to the collector of the control pressure, made in the form of a hollow cylinder with a blind bottom and installed inside the piston of the hydraulic cylinder, the specified spool is meshed with the piston of the highest category and the piston of the hydraulic cylinder and moves inside it within the gap δ, and its stroke is limited by the nut, and in its wall are made: a pressure cavity, two discharge cavities, while the control cavities of the hydraulic cylinder, depending on the movement of the spool valve, can be connected to the pressure cavity or to the drain cavities through channels made in the piston of the hydraulic cylinder in addition, the drain cavities communicate with the inlet cavity of the flow stabilizer, which is rigidly connected to the control valve, and the cavities of the discharge pistons are connected to the drain manifold or the control pressure manifold via hydraulic lines in which electrohydraulic valves are installed (for piston cavities of a lower discharge) and hydraulic lines, in which electrohydraulic valves and amplification hydraulic valves for piston cavities of medium and higher discharge are installed in series. 2. The digital steering actuator according to claim 1, characterized in that the number of electrohydro valves and the number of discharge pistons is seven, and the number of amplification hydraulic valves is five, and the electrohydro valves and amplification hydraulic valves are arranged in a circle around the circumference of the digital-analog drive. 3. The digital steering actuator according to claim 1, characterized in that the electrohydro valve has an electromagnet and a shutter, which includes a spool and a sleeve, while in the sleeve there are two control cavities and a drain cavity, one of the control cavities being connected to the control pressure manifold, and the second - when moving the spool, it is connected to the first control cavity and to the control cavity of the piston (s) of a smaller discharge. 4. The digital steering actuator according to claim 1, characterized in that the amplification hydraulic valve has a piston and a shutter, which includes a spool and a sleeve, while in the sleeve there are two control cavities and a drain cavity, one of the control cavities being connected to the control pressure manifold, and the second - when moving the spool, it is connected to the first control cavity and through the line is connected to the control cavity of the piston (s) of the larger discharge, in addition, the spool is made in one piece with the piston, and its diameter is smaller than the diameter of the piston , Wherein the control piston cavity hydraulically connected to the control chamber Electrohydraulic. 5. The digital steering gear according to claim 1, characterized in that each engagement element of the discharge pistons and the amplification hydraulic valve has a L-shaped cross section. 6. The digital steering gear according to claim 1, characterized in that the flow stabilizer has a housing containing an inlet cavity and a reduced pressure cavity separated by a partition in which throttle openings are made, said housing having a cover inside which a spring-loaded sensing element with a support the surface, in addition, between the sensitive element and the housing of the flow stabilizer a regulatory clearance is made, the exit from which is connected to the drain pipe, and the annular cavity in which the sensor The element is connected to the inlet cavity of the flow stabilizer. 7. The digital steering drive according to claim 1, characterized in that the position lock of the output rod of the hydraulic cylinder has a housing and a cavity that is hydraulically connected to the control pressure manifold, a cover, a spring-loaded hollow rod and a pin, while the rod is connected to the pin with a screw, in addition, a U-shaped groove is made at the end of the check, interacting with an annular protrusion made on the output rod of the hydraulic cylinder.

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