US2214757A - Nozzle - Google Patents

Description

Patented sept 17, 1940 lUNITED STATES NOZZLE Carroll R.. Alden, Detroit, Mich., assigner to Ex- A Cell- Corporation, Detroit, Mich., a corporation of Michigan Application December 10, 1937, Serial No. 179,069 Renewed December 13, 1939 13 Claims The present invention relates to improvements in nozzles adapted particularly for 'delivering timed metered injections of liquid fuel in connection with the operation of internal combustion engines.

One of the important objects of the present invention is to provide a novel fuel injection nozzle in which proper atomization of the fuel and maximum penetration consistent therewith of the issuing jet or spray into the combustion space are obtained at all rates of injection.

Another object is to provide a new and improved plain orifice nozzle in which the manner of approach of the fuel to the orifice is varied to change the discharge characteristics in accordance with changes in the rate of injection.

A further object is to provide a novel plain oriflce nozzle in which the coefficient of discharge of the orifice is controlled by the flow of the fuel.

A more specific object is to provide a new and improved fuel injection nozzle with a plain discharge orifice in which the fuel is caused to issue from the orifice as a jet or spray varying progressively from a centrifugal form to a non-centrifugal form inthe course of the valve opening movement, whereby the coeillcient of discharge and hence the flow capacity of the orifice are progressively increased to obtain the required dispersion and penetration characteristics not only at maximum rates of delivery but also at low and medium rates of delivery. I

A further object is to provide novel means for effecting a positive conversion of the iiow characteristics in the course of the valve opening movement, and particularly for breaking up or eliminating the rotational swirl of the fuel upon movement of the valve into fully open position.

Still another object is to provide a novel flowcontrolled i'uel injection nozzle with a plain discharge orifice in which initial, intermediate and final flow restrictions of progressively increased flow areas are successively effective to set up opening pressure assistances in the course of the valve opening movement, and in which the intermediate restriction is also effective within its range to vary the coefllcient of discharge of the orice as required to maintain a proper injection pressure at low and medium rates of delivery.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is a longitudinal sectional view of a nozzle tip embodying the features of my invention.

Figs. 2, 3 and 4 are transverse sectional views taken respectively along lines 2-2 to 4-4 'of ied form of nozzle tip with the valve in fully closed position.

Fig. 6 is a'fragmentary view of the tip illustrated in Fig. 5, but with the valve in fully open position.

Fig. 7 is a transverse sectional view taken along line 1-1 of Fig. 5.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the. drawings and will herein describein detail the preferred embodiment. but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

The present invention is an improvement of the nozzle tips disclosed in my copending applications Serial No. 152,074, filed July 6, 1937, and Serial No. 158,639, led August 12, 1937. Any subject matter common to this application and either of said copending applications is claimed Ain the earliest filed application.

Referring more particularly to the drawings, the fuel injection nozzle illustrated in Figs. 1 to 4 comprises a suitable body or housing II. Preferably, the body II is in the form of a tubular shell defining an axial bore I2, and having an external peripheral flange I3 at the base end and an internal peripheral flange I4 at the discharge end.

The discharge end of the shell II is closed by an orifice head I5 which has suitable orifice means with the desired fuel discharge characteristics, and which preferably is removable to permit substitution for different spray patterns and, characteristics. The orifice head I5 may be provided in any desired form, and in the present instance is shown as a circular plate or block extending snugly through the flange I4, and having a peripheral mounting flange I6 seating snugly within the bore I2 against the inner face of the flange I4.

A generally tubular spacer I1, having an inner peripheral flange I8 at the outer end defining an axial guide bore I9, is removably fitted into the shell Il and serves to hold the plate I5 in position. Removably positioned against the inner end of the spacer I1 is a tubular valve body 20 having an inner peripheral end flange 2|.

A stationary member 22 in the form of a. cylindrical valve plug is removably fitted into the base end of the shell II against the body 20, and serves to hold the various parts within the shell II in assembled position. l Suitable plastic means 23 may be pressed into an annular groove 24 having opposed complementary sections in the base en'd of the'shell I I and the member 22, and serves to seal and maintain the assembly. The member l 22 is formed with an axial fuel inlet passage 25 adapte'd for a fluid-tight connection with a fuel pump or other suitable means (not shown) for supplying the fuelto be injected.

It will be understood that the assembly just described constitutes the rigid structure of the nozzle tip, and as such is adapted to be connected to the source of fuel supply, and to be clamped or secured to the engine at the desired point of injection a nozzle holder or other suitable means, not specifically disclosed herein since per se it forms no part of the present invention, may be utilized for this purpose as is well understood 4in the art. 'The rigid structure of the nozzle tip is susceptible of various modifications and alternative forms without departing' from the broad aspects of the present invention, and in general provides an internal chamber 28, defined by the spacer i1 and the body 20, and adapted for communication with the inlet passage 25 and to discharge through the orifice body I5. l

'I'he supply of fuel vunder pressure, from the inlet passage 25 to the chamber 28 for injection through the orifice head I5 into the combustion space, is under the control of a nozzle valve 21. Within the broad aspects of the invention, the valve 21 may be of any suitable form 'or character. In the present instance, the valve 21 is spring seated against the pressure of the fuel, and opens outwardly in the direction of the fuel fiow. More particularly, the valve 21 comprises a fiat annular valve seat 28 formed in the inner end of the valve plug 22, and encircling a valve passage 29 opening from the passage 25. A movable valve member 30, herein shown in the form of a partial or half ball, has a flat valve f ace v3| adapted for engagement with the seat 28. When the valve member 30 is seated, the seat 28 denes a central pressure area Av on the face 3.I exposed to the fuel pressure in the passage 29.

Any suitable means may be provided for supporting the valve member 30, and in the present instance this means comprises a retainer 32 in the form of a circular head slidably guided in the valve body and rigid with the inner end of an axial stem 33 guided in the bore I9. To permit self-alignment with the valve seat 28, the spherical portion of the valve member is seated for universal adjustment in a partial spherical socket 34 formed in the free end face ofthe retainer head 32. lA coiled compression spring 35 closely encircles the stem 33, and abuts at opposite ends against the spacer flange I8 and the head 32 to urge the valve member 38 toward or against the valve seat 28 with a predetermined spring pressure.

The valve member 30 is reciprocably disposed within the confines of the flange 2I,v and coacts therewith to denne an annular flow passage 38. Formed in the periphery of the head 32 are a plurality of longitudinal flutes 31 (see Fig. 2) which provide unrestricted flow passages from the passage 36 to the chamber 28 about the stem 33. The outer end portion of the stem 33 is formed with a peripheral groove 38 defining a head 39 slidable with a close fit in the outer end of the bore I9, and is also formed on the periphery with a plurality of longitudinal fiats 40 (see Fig. 3) defining ow passages opening from the chamber 26 to the groove 38. A plurality of grooves 4I in the periphery of the head 38 serve to connect the groove 33 to the orifice means in the orifice head I5. It will be understood that the fiow path of the fuel from the valve 21 to the orifice head I5 leads through the passage 36, the

flutes 81, the chamber 28. the passages alonthe flats 40, the groove 38 and the grooves 4I.

Upon the application of fuel pressure from any suitable source of timed delivery of metered fuel quantities, static pressure is first applied to the area of the ball element 30 exposed tothe valve passage 28 at the valve seat 28, i. e., the valve opening pressure area Av.' When the hydraulic pressure times the area Av overbalances the pressure of 'the spring 35, the valve 21 will open to permit the fiow of fluid to the orifice head I5 at which point hydraulic pressure is again huilt up by yreason of the orifice restriction.

'Ihe opening of the valve 21 is made at least in part responsive to the rate of fuel fiow so that the applied hydraulic pressure may be limited and controlled as desired throughout the range of valve movement. More particularly, a plurality of fiow restrictions or resistances of diii'erent ow areas are interposed in the path of fuel flow, and are successively effective over different 21 open, and hence the remaining pressure of the total applied pressure is relatively high and is utilized solely for injection purposes to obtain they desired atomization andk penetration. The subdivision of the pressure to perform the separate functions makes possible a heavy lifting action Without objectionably disturbing the injection characteristics of the nozzle.

Each ow restriction in coaction with the associated pressure area sets lup a valve opening pressure assistance. assistances A, B and C have been-provided. IIt will be understood that the fiow restrictions may be provided in any suitable manner, and may be varied widely in form and character depending on the operating characteristics desired.

The assistance A is in control when the valve member 30 is in close proximity to'the seat 28, and causes the initial opening movement and the final closing movement of the valve 21 to occur with extreme rapidity. It is transient or disappearing in character in the opening movement of the valve 21. To obtain the assistance A, the an- In the present instance three nular valve seat 28 is peripherally relieved by an encircling groove or recess 42 formed in the plug 22, thereby providing a small seat area. As a result, the seat pressure is sumciently high to collapse or extrude the oil film between the valve faces when the valve 21 is closed. The bottom of the groove 42 is inclined outwardly toward the face 3I of the valve member 38, and coacts with the peripheral edge of the latter to define a small annular flow restriction 43. By inclining the bottom of the groove 42, the seat 28 is conveniently provided with a substantial relief, and the effective minimumA area or clearance of the small fiow restriction 43 may be readily and accurately determined by the use of mathematics, the depth of the seat relief, theangle and the radial dimensions of the half ball 30 and seat 28 being known. The bottom of the groove 42 being closely spaced from the peripheral edge of the half ball 38 also serves approximately to square up the latter with the seat 28. Hence, the half ball ciently large to cause damage or result in valve leakage.

When the hydraulic pressure from the source of supply acting on the closed valve area Av is sufficient to overcome the force of the spring 3l. the valve 21 will open. After the initial opening movement, the annular restriction 4l builds up a pressure differential which is applied to the flat face area 9| of the valve member III, and which assists the initial force to accelerate rapidly the ilrst portion of the valve movement, so that. the valve member 90 is caused to leave the seat 29 with a popping action. Since the area II is much larger than the valve area Av, the differential pressure required to move the valve member lll is considerably lower than the valve opening pressure, and makes available immediately a high pressure for injection with proper atomization. If the valve opening movement continues, as for the delivery of large quantities of fuel, the initial assistance A, quickly disappears, thereby reducing the pressure drop at the seat and releasing. more pressure for injection. The assistance A also serves to accelerate rapidly the final closing movement of the valve 21. As the valve member 99 moves into close proximity to the seat 29, the restriction 42 again becomes effective, and sets up a differential pressure acting on the ball area 9| in opposition to the closing movement. However, when the rate of flow drops to a point where the assistance A is no longer effective to balance the closingforce, the spring 35 will move the valve member 39 rapidly toward the seat 28 to close the valve 21 with a popping action.

'I'he assistance B becomes effective after disappearance of the assistance A, and serves to control the transition from the slowest rates of delivery to medium rates of delivery. To obtain this assistance. the grooves 4| are formed to dene a flow restriction tending to set up a diilerential pressure acting outwardly on an effective area equal to the transverse area of the stem I3. As the head 39 moves outwardly of the bore I9 in the opening movement of the valve 2'I, the effective length of the grooves 4I is shortened, thereby reducing the flow restriction. Hence, the assistance B also is transient or disappearing in character so as to be effective only over the intermediate range of injection.

The final assistance C becomes effective after disappearance of the assistance B, and hence controls the transition from medium rates of delivery to maximum rates of delivery. To obtain this resistance, the clearance between the ange 2| and the peripheral edge of the valve member 90 is small so that the passage 38 deflnesa flow restriction tending to set up a differential pressure acting outwardly on the face 3|. It will be understood that the valve may open to any point in the range of movement depending on the rate and quantity of injection. The assistances A, B and C would be relatively so proportioned as to cooperate to obtain the desired result. For further details as to the function and operation of the assistances A, B and C, reference may be had to the aforesaid copending application, Serial No.

The orifice head I5 may be provided in various forms depending on the spray characteristics desired. In Fig. l, the head I5 is formed in the inner face with an injection pressure chamber 44 which registers with the bore I9 to receive the head I9 in the opening movement of the valve 21, and which opens axially to a single plain hole discharge orifice 4l.

One ofthe important features of the present invention is to vary the discharge characteristics of the orifice 4l in accordance with the rate of fuel flow so as to obtain proper atomization and penetration at all rates of delivery, and particularly to permit the delivery of very small quantities of fuel without the presence of objectionable solids through a fixed orifice otherwise of sumcient size for maximum injection. 'Ihis is accomplished by changing the manner of approach of the fuel to the orifice 45 whereby to vary the coelcient of discharge as required. The degreeiof atomization is a function of the pressure a plied at the orifice, and the pressure varies as the square oi' the velocity times the coefllcient of discharge. Ifthis coelcient is constant, the pressure at low rates of delivery may be too low to break up the fuel. By varying the coefficient, an effect comparable to a variation in the size of the orice is obtained.

To control the coefficient of discharge of the orifice 45, a variable centrifugal action is imparted to the entering fuel. In Fig. 1, the centrifugal action is obtained by means of the.

grooves 4| which preferably are V-shaped and of suitable flow area and proportions in cross-section, and which are formed with a suitable helical lead to impart a swirl to the fuel passing therethrough. The swirl of the fuel reduces the coemcient of discharge, and hence builds up an injection pressure in the chamber 44 suflicient to effect proper atomization. Since the head 39 moves outwardly into the chamber 44, the effective length of the grooves 4I is progressively decreased in the course of the Valve opening movement. Hence, the coefilcient of discharge is the lowest at minimum rates of delivery and increases progressively through the range of the assistance B. Upon movement of the peripheral groove 38 into direct communication with the chamber 44, the grooves 4I cease to be effective to impart a centrifugal or rotational swirl to the incoming fuel, and the fuel jet issuing from the orifice 45 tends to become non-centrifugal.

'I'he groove belt defined by the head 39 has a close and uniform sliding fit with the bore I9 so that the grooves 4I will have maximum effectiveness in defining the flow passages therethrough and in varying their restrictive action with changes in the valve lift. The spiral grooves 4| should have a flow area sufllciently restricted to make the assistance B effective, but not restricted to an extent resulting in interference with the proper functioning of the assistance A.

The helix angle of the grooves 4|, i. e., the lead along the stem axis, may be varied within limits depending on the atomization and penetration characteristics desired, without departing from the invention. Ordinarily, the helix angle should be the maximum vconsistent with desired atomization. at low rates of injection. Decreasing the helix angle results in a greater centrifugal action and a corresponding decrease in the coefficient of discharge. A greater cone spray angle, with increased atomization, is thereby obtained, and the jet penetration is decreased. Increasing the helix angle results in a smaller spray cone angle and increased jet penetration.

After the grooves 4| leave the bore I9, the assistance C is adapted to accomplish the last step in moving the valve 29 into fully open position.

2liA

During vthis step, the grooves 4I are no longer residual centrifugal action. An important feature of the present invention is to breakup or eliminate quickly .and effectively any residual swirl when the valve moves into fully open position so as to obtain a spray with maximum penetration characteristics after the swirl initially imparted has served its purpose. This is'accomplished -by a positive conversion of the ow characteristics from centrifugal to non-centrifugal.

To effect the conversion, the head 38 is formed with an end extension 48, and this extension and the peripheral surface of the chamber 44 in the orifice plate I5 are conical or tapered irl form for engagement to prevent the discharge of the swirling fuel when the valve 21 reaches full open position. The groove belt of the head 38 is cylindrical in form, and spaced peripherally from the surface of the chamber 44.` The head 38 is also formed with passage means 41 effective to direct the fuel non-centrifugally to the orifice 45 when the extension 46 engages the orifice plate i5 to cut ofi the peripheral flow. In the present instance, the passage means 41 consists of a plurality, for example four, uniformly spaced radial slots which open to the groove belt of the head 39, and which intersect each other longitudinally in alignment with the orifice 45. These slots do not interfere with the rotary motion of the fuel in the entry to the orifice 45 as long as the fuel is free to swirl about the head extension 48. However, when the extension 45 comes into engagement with the orifice plate i5, rotary motion of the fuel is no longer possible, and the fuel must iiow radially inwardly from the periphery of the head 39 through the slots 41. and thence axially outward through the orice 45. The slots 41 therefore become effective immediately upon movement of the valve 21 into full open position to remove or break up any residual swirl in the fuel.

The modified form illustrated in Figs. 5 to 7 is closely similar to the form just described, and hence corresponding parts will be identified by the same reference numerals plus the letter a, and only the differences in construction will be specifically described. In this form, all possible effect of any residual swirl is completely eliminated immediately upon movement of the valve 21 into fully open position.

The valve stem 33 in this instance is cylindrical instead of fiuted. A plurality of peripherally spaced longitudinal bores 48, for example three, are formed in the outer end of the spacer I1a and open from the chamber 26B to define iiow passages. Formed in the flange I8 in which -the stem 33 is guided is an internal annular groove 49 which intersects the bores 48 to establish communication therewith, and which is always open to the groove 38a. The groove belt of the head 39, with the restricted helical or inclined grooves 4i is movable into and out of the bore I8, and the conical or tapered end extension 46a is movable into engagement with the orifice plate i5a to cut off completely the path of ow from the grooves 4Ia to the orifice 45* when the valve 21al is fully open.

Formed in the stem 33a in axially spaced relation to the groove 18 is an annular by-pass groove 50. This'groove is movable into and out of communication with the supply groove 48,

and is connected through radial ports 5I to an axial bore 52 in and opening to the end of the,

stem 33B.

When the valve 21 is in or near closed posiagravar tion. fuel from the chamber 28" is free to pass 4through the bores 48, the grooves 48 and 38",

the grooves 4 I and the chamber 44* to the orice 45. At this time, the grooves 48 and 50 are out of communication so that'no iiow occurs through the bore 52 and`all of the fuel is discharged cen'- trifugally. After a predetermined valve movement, for example midway of the range, the

Igroove 50 moves into communication with the groove 48. Now, the fuel is free to, flow not only through the restricted grooves 4I* which impart the centrifugal action, but also non-centrifugally from the groove 48 through the groove 50, the ports 5I? and the bore 52 to the orifice 45, As the valve opening movement continues, the iiow through the centrifugal grooves 4I is decreased progressively while that through the bore 52 is increased. When the stem 33 engages the orificek plate I5, the centrifugal flow is completely eliminated, and all the fuel is caused to iiow without centrifugal action through the bore 52.

lI am cognizant of the fact that the operation of the nozzle may be influenced to some extent by the pressure in the combustion chamberV of the engine. but for the purpose of simplicity in describing the invention have disregarded this factor particularly since it can be compensated for by proper selective design of the nozzle parts.

I claim as my invention:

1. In a fuel injection nozzle, in combination, a f

body having a fuel inlet and a fixed discharge orifice of constant flow area, valve means for controlling the supply of fuel under pressure for discharge through said orifice, means operable in the initial opening movement of said valve means for imparting a centrifugal action to the fuel entering said oriiice, and means for positively eliminating said action upon further opening movement of said valve means into a predetermined position.

2. In a fuel injection nozzle, in combination, a body having a fuel inlet and a fixed discharge orifice of constant flow area, valve means for controlling the supply of fuel under pressure for discharge through said orifice, and means operable in the opening movement of said valve means to cause the fuel to issue through said orifice initially in the form of a centrifugal envelope of progressively decreasing cone angle and finally in the form of a non-centrifugal spray, said last mentioned means being operable to effect a positive conversion from said envelope to said noncentrifugal spray. Y

3. In a fuel injection nozzle, in combination, a body having a circular chamber with anvaxial inlet bore opening thereto, a spring-seated valve for controlling the supply of fuel to said bore and opening in the direction of fuel flow, a head movable with said valve and slidable with a close fit progressively into and out of the outlet end of said bore, a plurality of helical grooves formed in the periphery of said head and opening to the opposite ends thereof, said head when in said.

charge orifice opening axially from said chamber, y

and means operable after movement of said head out of said bore to effect elimination of residual asu-,757

centrifugal action of the fuel and to discharge the fuel non-centrifugally to said orifice.

4. In a fuel injection nozzle, in combination, a hollow body having an inner chamber with a fuel inlet at one end and a fixed discharge orifice at the other end, a spring seated valve for controlling the supply of fuel through said inlet to said chamber and opening in the direction of fuel flow, means for defining a plurality of peripherally inclined restricted flow passages decreasing progressively in effective length in accordance with the opening movement of said valve and causing the fuel to enter said orifice centrifugally, and means for eliminating the residual centrifugal action /of said fuel when said passages become ineffective.

5. In a fuel injection nozzle, in combination, means defining a chamber having a fuel inlet and a fuel outlet, spring-seated valve means for controlling the supply of fuel to said inlet, and means operable with said valve means and cooperating with said inlet in the valve opening movement to define first a flow passage through said chamber for causing the fuel to issue centrifugally from said orifice and upon movement of said valve means into fully open position to close said passage and establish a parallel passage for causing the fuel to issue non-centrifugally from said orifice.

6. In a fuel injection nozzle, in combination, a hollow body havingA a chamber with an inlet bore at one end and a discharge orifice at the other end, a spring-seated valve for controlling the' supply of fuel through said inlet to said chamber and opening in the direction of fuel flow, a

'valve stem`movable with said valve and having a head spaced from said valve with an inclined groove coacting with said inlet to impart a rotational swirl to the entering fuel, said head being movable into engagement with the surface of said chamber to interrupt the flow of fluid from said chamber through said groove to said orifice, and a passage formed in said head for discharging uid from said inlet non-centrifugally to said orice.

7. In a fuel injection nozzle, in combination, a hollow body having a chamber with an inlet at one end and a discharge orifice at the other end, a spring-seated valve for controlling the supply of fuel through said inlet to said chamber and opening in the direction of fuel flow, and means movable with said valve and having a head with an inclined groove coacting with said inlet during the initial portion of the opening movement of said valve to impart a rotational swirl to the entering fuel,^said head being movableinto engagement with the surface of said chamber during the final portion of the opening movement of said valve to render said groove ineffective and to interrupt the centrifugal iiow of duid from said chamber through said groove to said orifice.

8. In a fuel injection nozzle, in combination, a body having a chamber of conical form, an orifice opening from said chamber at the apex. a

groovetosaidchamberandmcvabiemveiy out of said first mentioned bore, said stem having a tapered end engageable with the surface of said chamber to close the passage from said inclined groove to said orifice upon movement of said inclined groove out of said first mentioned bore and of said second groove into communication with said internal groove.

9. In a fuel injection nozzle, in combination, means defining a chamber having a fuel inlet bore and a fuel outlet, spring-seated valve means for controlling the supply of fuel to said bore, a stem movable with said valve means and having a cylindrical groove belt movable from said chamber into and out of said bore, an inclined groove in the periphery of said belt and coacting with said bore when said head is in said bore to define a restricted flow passage from said bore to said chamber and to impart a centrifugal force to the fuel passing therethrough, an extension on said stem movable into cooperative relation with said body upon movement of said belt out of said bore to interrupt the flow of swirling fuel to said outlet, and a radial slot in said stem opening from said belt through said extension to establish a flow passage for directing fuel from said chamber non-centrifugally to said outlet when the flow of swirling fluid to said outlet is interrupted.

10. In a fuel injection nozzle, in combination, a body having a fuel inlet and a discharge orifice, valve means for controlling the supply of fuel under pressure for discharge through said orifice, and means operable in the opening movement of said valve means to cause the fuel to issue through said orifice initially in the form of a centrifugal envelope of progressively decreasing cone angle and finally in the form of anoncentrifugal spray, said last mentioned means being operable to effect a positive conversion from said envelope to said noncentrifugal spray.

11. In a fuel injection nozzle, in combination, a hollow body having a fuel inlet and a discharge orifice, a spring seated valve for controlling the supply of fuel4 from said inlet to said orifice and opening in the direction of fuel flow, means for defining a peripherally inclined restricted flow passage in the path of fuel iiow and decreasing progressively in effective length in accordance with the movement of said valve in one direction and causing the fuel to enter said orifice centrifugally, and means for eliminating the residual centrifugal action of said fuel when said passage becomes ineffective.

12. Ina fuel injection nozzle, in combination, a body having a fuel inlet and a fuel outlet, and valve means for controlling the supply of said fuel from said inlet to said outlet, said valve means cooperating with said body to denne nrst a flow passage to said outlet for causing the fuel to issue centrifugally and upon movement of said valve means into fully open position to close said e and to establish a parallel to said outlet for causing the fuel to issue non centrifugally.

13. In a fuel injection nozzle, in combination,

a hollow body having a fuel inlet and a fuel outlet, and valve means for controlling the supply of said fuelfrom said inlet to said outlet, said valvemeans defining a first normally open spiral flowl CARROILRAIDIN.

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