JP2007154724A - Reciprocating compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reciprocating compressor that reduces the noise of a suction valve and secures a sufficient fluid absorption volume as necessary. <P>SOLUTION: A cylinder 5 is installed on a crack case 1, and a piston 7 is inserted into the cylinder 5 so as to make reciprocating motion. The piston 7 has a suction port 12 for introducing air into a compression chamber B from a crank chamber A, and a suction valve 13. A valve plate 6 for blocking the cylinder 5 has a discharge port 14 and a discharging valve 15 for discharging compressed air from the compression chamber B, and also has an unload port 19 and an unload valve 20 for unload operation. The unload port 19 is made to communicate with the crank chamber A through a bypass pipe 22. The unload valve 20 is forced to be opened by a push solenoid 21 at unload operation, and functions as the other suction valve at loaded operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reciprocating compressor suitably used for compressing a fluid, for example, by reciprocating a piston in a cylinder.

  In general, a reciprocating compressor is known in which a cylinder is provided in an upper part of a crankcase and a piston connected to a crankshaft in the crankcase is inserted into the cylinder. In this case, a valve plate that defines a compression chamber is provided between the front end of the cylinder and the piston. The piston is provided with a suction port and a suction valve for sucking the air in the crankcase into the compression chamber, and the valve plate is provided with a discharge port and a discharge valve for discharging the compressed air in the compression chamber. ing. In the conventional reciprocating compressor, the piston is reciprocated in the cylinder, so that the air in the crankcase is sucked into the compression chamber through the suction port, compressed, and then directed from the discharge port to the air tank or the like. It is the composition which discharges.

JP-A-8-28469

  By the way, in the above-described prior art, the suction port is provided with a plate-like suction valve, and the suction valve opens and closes when the suction valve is separated from the seating surface located around the opening of the suction port. It is the structure which speaks. However, since the conventional technique uses a single suction valve, the outer shape of the suction valve tends to increase, and the opening degree tends to increase. As a result, there is a problem that the seating sound when the suction valve is closed increases and the noise increases.

  In the prior art, since the suction valve is provided in the piston, the hole diameter of the suction port and the size of the suction valve are limited by the cylinder diameter. As a result, there is a problem that the amount of air sucked is insufficient and the compression efficiency of air is lowered.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a reciprocating compressor capable of reducing noise caused by a suction valve and sufficiently securing a fluid suction amount. There is.

  In order to solve the above-described problems, the present invention provides a crankcase for supporting a crankshaft therein, a cylinder attached to the crankcase, and a reciprocating motion in the cylinder connected to the crankshaft via a rod. And a piston defining a compression chamber on the tip end side of the cylinder, a suction port for sucking an external fluid into the compression chamber, a valve provided in the suction port and opened in a suction stroke, and closed in a discharge stroke. The present invention is applied to a reciprocating compressor having a suction valve that discharges, a discharge port that discharges compressed fluid from the compression chamber, and a discharge valve that is provided in the discharge port and closes in a suction stroke and opens in a discharge stroke .

  A feature of the configuration adopted by the invention of claim 1 is that an unload port that communicates the compression chamber and the outside is provided, and the unload port is forcibly opened when the unload mechanism is operated. Thus, an unloading valve that performs an unloading operation and opens in the intake stroke and closes in the discharge stroke when the unloading mechanism is not operated is provided.

  In the invention of claim 2, the suction valve and the unload valve are each formed in a plate shape in which one end is a fixed end and the other end is a free end, and the suction valve and the unload valve have their thicknesses. When at least any one of the size, shape, and material is different from each other, the timing for opening the valve and the frequency of sound when the valve is closed are different from each other.

  According to a third aspect of the present invention, a valve plate that defines a compression chamber between the piston and the piston is provided on the tip side of the cylinder, and the discharge port and the unload port are provided on the valve plate, and the suction port Is configured to suck the fluid in the crankcase provided in the piston into the compression chamber.

  According to a fourth aspect of the present invention, the unload port is connected to a bypass flow path opened in the crankcase.

  According to the invention of claim 1, since the unload port is provided separately from the suction port, and the unload valve is provided in the unload port, the unload valve is forcibly opened when the unload mechanism is operated. Thus, the outside and the compression chamber can be communicated, and the fluid can be compressed and the unload operation can be performed. On the other hand, when the unloading mechanism is not operated, the unloading valve opens in the suction stroke and closes in the discharge stroke, like the suction valve. For this reason, since the fluid can be sucked into the compression chamber from the unload port in addition to the suction port, for example, even when the size of the suction port or the suction valve is limited, a sufficient amount of fluid is supplied from the two ports. Can be sucked into the compression chamber.

  Moreover, since the unloading valve functions as another suction valve, the outer shape of the suction valve and the unloading valve can be made smaller than when a single suction valve is used. For this reason, the seating sound when the suction valve or the like is closed can be reduced, and the noise can be reduced.

  According to the invention of claim 2, the suction valve and the unload valve formed in a plate shape are opened when at least one of the thickness dimension, shape and material thereof is different from each other. The timing and frequency of sound when the valve is closed can be made different from each other. As a result, the suction valve and the unload valve do not open together, and the timing at which the suction valve and the unload valve close can be made different from each other. Sounds accompanying valve opening and closing do not overlap each other, and noise can be reduced.

  In addition, since the frequency of the sound when the suction valve and the unload valve are closed can be made different from each other, the suction valve and the unload valve generate a sound with the same frequency compared to when the valve is closed. The seating sound can be reduced and noise can be reduced.

  According to the invention of claim 3, since the suction port is provided in the piston and the unload port is provided in the valve plate, for example, compared to the case where both the suction port and the unload port are provided in the valve plate. The hole diameter of the suction port and the unload port can be increased. Therefore, a sufficient amount of fluid can be sucked into the compression chamber through these ports, and the compression efficiency can be improved.

  According to the invention of claim 4, since the unload port is connected to the bypass flow path opened in the crankcase, the sound generated by the unload valve can be guided into the crankcase through the bypass flow path. it can. Further, since the suction port is provided in the piston, the sound generated by the suction valve can also be released to the outside through the inside of the crankcase. For this reason, the sound generated by the suction valve and the unload valve is not directly released to the outside, but passes through the crankcase, so that the sound of each valve can be reduced in the crankcase and noise can be reduced. it can.

  Hereinafter, a swing type air compressor will be described as an example of a reciprocating compressor according to an embodiment of the present invention, and will be described in detail according to the accompanying drawings.

  First, FIG. 1 thru | or FIG. 6 has shown the air compressor by embodiment. In the figure, reference numeral 1 denotes a crankcase in which a crank chamber A is defined. A crankshaft 2 is rotatably supported by the crankcase 1 so as to be positioned in the crank chamber A. The crankshaft 2 is connected to an output shaft 3 of an electric motor (not shown), for example, and is driven to rotate by the electric motor. Further, a suction port 4 opened to the outside is provided on the side surface of the crankcase 1, and external air flows into the crank chamber A through the suction port 4.

  Reference numeral 5 denotes a cylindrical cylinder having a base end attached to the crankcase 1, and the inside of the cylinder 5 communicates with the inside of the crank chamber A through a vent 5A. Further, the front end side of the cylinder 5 is closed by a valve plate 6, and the valve plate 6 defines a compression chamber B with a piston 7 described later. Further, on the surface of the valve plate 6, a seal groove 6 </ b> A for accommodating a later-described seal member 18 is formed.

  Reference numeral 7 denotes an oscillating piston that is fitted in the cylinder 5 so as to be able to reciprocate. The piston 7 is formed in a substantially disc shape, and a retainer 9 that holds a lip seal 8 is attached to the surface of the piston 7. It has been. Thereby, the lip seal 8 surrounds the outer peripheral side of the piston 7 and hermetically seals between the outer peripheral surface of the piston 7 and the inner peripheral surface of the cylinder 5.

  Further, the back surface of the piston 7 is fixed to the distal end side of the rod 10, and the proximal end side of the rod 10 is rotatably connected to the crankshaft 2 via a bearing 11. As a result, the piston 7 reciprocates while swinging in the cylinder 5 by the rotational drive of the crankshaft 2, thereby forming a compression chamber B with the valve plate 6.

  Reference numeral 12 denotes a suction port formed in the piston 7. The suction port 12 is provided through the piston 7 and the retainer 9, and both ends thereof open to the crank chamber A and the compression chamber B, respectively. As a result, the suction port 12 sucks outside air into the compression chamber B via the crank chamber A.

  13 is a suction valve provided on the side of the compression chamber B of the suction port 12, and the suction valve 13 is disposed on the surface side of the retainer 9 as shown in FIGS. 4 and 6. The suction valve 13 is formed in an elongated plate shape having a thickness dimension T1, and the base end side thereof is a fixed end and is attached to the retainer 9 using a fixing pin 13A, and the distal end side is a free end. The opening end of the suction port 12 is covered so that it can be opened and closed. As a result, the suction valve 13 opens in the suction stroke for sucking external air into the compression chamber B, and closes in the discharge stroke for discharging the compressed air from the compression chamber B.

  The suction valve 13 is provided with a valve presser (not shown) for regulating the valve opening when the valve is opened.

  Reference numeral 14 denotes a discharge port formed in the valve plate 6. The discharge port 14 is provided through the valve plate 6, and both ends thereof are respectively connected to a compression chamber B and a discharge chamber C in a cylinder head 16 described later. It is open. Thereby, the discharge port 14 discharges the compressed air in the compression chamber B to the outside through the discharge chamber C.

  Reference numeral 15 denotes a discharge valve provided on the discharge chamber C side of the discharge port 14, and the discharge valve 15 is disposed on the surface side of the valve plate 6 as shown in FIGS. 4 and 5. Similarly to the suction valve 13, the discharge valve 15 is formed in an elongated plate shape and extends in a direction orthogonal to the extension direction of the suction valve 13. The discharge valve 15 is attached to the valve plate 6 using a fixed pin 15A with the base end side as a fixed end, and covers the open end of the discharge port 14 so that the front end side is a free end and can be opened and closed. . Thereby, the discharge valve 15 is closed in the suction stroke for sucking the external air into the compression chamber B, and is opened in the discharge stroke for discharging the compressed air from the compression chamber B.

  The discharge valve 15 is provided with a valve presser (not shown) for regulating the valve opening when the valve is opened.

  Reference numeral 16 denotes a cylinder head provided on the surface side of the valve plate 6. As shown in FIGS. 1 to 3, the cylinder head 16 has a discharge chamber C formed at a position facing the discharge valve 15. An unload chamber D in which an unload port 19 to be described later opens is formed at a position opposite to the center side of the valve plate 6 as a position different from the discharge chamber C. At this time, the discharge chamber C and the unload chamber D are partitioned by the partition wall 16A. Further, the cylinder head 16 is formed with a discharge port 17 opened to the discharge chamber C, and the compressed air in the discharge chamber C is discharged through the discharge port 17 toward an external tank (not shown). . The cylinder head 16 and the valve plate 6 are hermetically sealed using a seal member 18 attached in the seal groove 6A.

  Reference numeral 19 denotes an unload port provided in the compression chamber B separately from the suction port 12. The unload port 19 is provided in the valve plate 6, unlike the suction port 12. The plate 6 is arranged on the center side of the valve plate 6 as a position different from the discharge port 14. The unload port 19 is provided through the valve plate 6, and both ends thereof open to the compression chamber B and the unload chamber D, respectively. The unload port 19 communicates the outside with the compression chamber B via the unload chamber D and performs an unload operation.

  Reference numeral 20 denotes an unload valve provided on the compression chamber B side of the unload port 19, and the unload valve 20 is disposed on the back surface side of the valve plate 6 as shown in FIGS. The unload valve 20 is formed in an elongated plate shape having a thickness dimension T2, and its base end side is a fixed end and is attached to the valve plate 6 using a fixed pin 20A, and the distal end side is a free end. The opening end of the unload port 19 is covered so that it can be opened and closed. The unload valve 20 forcibly opens the communication between the compression chamber B and the unload chamber D when a push solenoid 21 described later is operated. On the other hand, when the push solenoid 21 is not operated, the unload valve 20 opens in the suction stroke for sucking external air into the compression chamber B, and closes in the discharge stroke for discharging the compressed air from the compression chamber B.

  Here, the thickness dimension T2 of the unload valve 20 is set to a value different from the thickness dimension T1 of the suction valve 13, for example, and the timings at which the unload valve 20 and the suction valve 13 are opened are different from each other. The timing at which the valves close is also different from each other. Further, the unload valve 20 and the suction valve 13 are configured so that the frequencies of sounds (sitting sounds) when they are closed are also different from each other.

  The unload valve 20 is provided with a valve presser (not shown) for regulating the valve opening when the valve is opened.

  Reference numeral 21 denotes a push solenoid as an unload mechanism provided in the cylinder head 16. The push solenoid 21 is disposed at a position facing the unload port 19 as shown in FIGS. (Not shown) has a shaft 21A that can be advanced and retracted to and from the unload port 19.

  Further, the push solenoid 21 excites the electromagnetic coil, thereby inserting the shaft 21A into the unload port 19 and causing the tip of the shaft 21A to protrude into the compression chamber B. Thereby, since the unload valve 20 is displaced into the compression chamber B, the push solenoid 21 forcibly opens the unload valve 20. As a result, since the air in the compression chamber B flows out to the unload chamber D in the discharge stroke, the compression chamber B is not pressurized, and an unload operation state is achieved in which the compression load is reduced.

  On the other hand, the push solenoid 21 releases the tip of the shaft 21A from the compression chamber B by releasing the excitation of the electromagnetic coil. As a result, the unload valve 20 is released from the forced valve opening state, so that, similarly to the suction valve 13, the unload valve 20 opens in the suction stroke and closes in the discharge stroke. As a result, external air is sucked into the compression chamber B through the unload chamber D.

  Reference numeral 22 denotes a bypass pipe as a bypass flow path connected to the unload port 19 through the unload chamber D. The bypass pipe 22 is provided between the cylinder head 16 and the crankcase 1 and both ends thereof are provided. The unload chamber D and the crank chamber A are opened. As a result, the bypass pipe 22 causes the air in the compression chamber B to flow out toward the crank chamber A when the push solenoid 21 is operated, and the air in the crank chamber A when the push solenoid 21 is not operated. It is made to flow toward B.

  The air compressor according to the present embodiment has the above-described configuration. Next, the operation of the air compressor will be described with reference to FIGS.

  First, when the unload operation is performed, the push solenoid 21 is electrically excited as shown in FIG. As a result, the shaft 21A of the push solenoid 21 extends into the unload port 19 and forcibly opens the unload valve 20. At this time, in the suction stroke in which the piston 7 moves from the top dead center to the bottom dead center, the air in the crank chamber A is sucked into the compression chamber B from the suction port 12 and the unload port 19. Further, in this suction stroke, the discharge valve 15 is in a closed state in close contact with the seating surface (surface) of the valve plate 6 and isolates the compression chamber B and the discharge chamber C from each other.

  On the other hand, in the discharge stroke in which the piston 7 moves from the bottom dead center to the top dead center, the unload valve 20 is open, so that the air in the compression chamber B enters the unload chamber D through the unload port 19. While flowing out, it flows into the crank chamber A through the bypass pipe 22. Here, for example, in addition to the pressure in a tank (not shown) connected to the rear stage of the discharge port 17, the elastic force of the discharge valve 15 acts, so that the discharge valve 15 is in the discharge stroke. The valve is not opened but is kept closed. As a result, during the unload operation, the air in the compression chamber B flows only into the unload chamber D, so that the compression chamber B is not pressurized and the compression load is reduced.

  Next, when the load operation (compression operation) is performed, the excitation of the push solenoid 21 is released as shown in FIGS. As a result, the shaft 21A of the push solenoid 21 is separated from the unload valve 20 and retreats from the compression chamber B. As a result, the unloading valve 20 functions as another suction valve since the forced opening is released.

  Accordingly, in the suction stroke in which the piston 7 moves from the top dead center to the bottom dead center, as shown in FIG. 1, the suction valve 13 and the unload valve 20 are opened, and the outside air is supplied from the suction port 4 to the crank chamber. Flows into A. As a result, the air in the crank chamber A flows into the compression chamber B through the vent 5A and the suction port 12, and the compression chamber B via the bypass pipe 22, the unload chamber D, and the unload port 19. It is sucked in. At this time, the discharge valve 15 is in a closed state in close contact with the seating surface (surface) of the valve plate 6 and isolates the compression chamber B and the discharge chamber C from each other.

  On the other hand, in the discharge stroke in which the piston 7 moves from the bottom dead center to the top dead center, the suction valve 13 comes into close contact with the seating surface (surface) of the retainer 9 as shown in FIG. The load valve 20 comes into close contact with the seating surface (back surface) of the valve plate 6 and closes the compression chamber B from the crank chamber A and the unload chamber D. At this time, since the pressure in the compression chamber B increases, the pressure in the compression chamber B becomes higher than the pressure in the discharge chamber C, and the discharge valve 15 opens. Thereby, the compressed air flows out of the compression chamber B through the discharge port 14 and is discharged toward the tank or the like through the discharge chamber C and the discharge port 17.

  Thus, in the present embodiment, since the unload port 19 is provided separately from the suction port 12 and the unload valve 20 is provided in the unload port 19, when the push solenoid 21 is operated, the unload valve 20 is provided. Can be forcibly opened to allow the unload chamber D and the compression chamber B to communicate with each other, and the air can be compressed without being compressed. On the other hand, when the push solenoid 21 is not operated, the unload valve 20 opens in the suction stroke and closes in the discharge stroke, like the suction valve 13. For this reason, since air can be sucked into the compression chamber B from the unload port 19 in addition to the suction port 12, for example, even when the sizes of the suction port 12 and the suction valve 13 are limited, the two ports 12 19, a sufficient amount of air can be sucked into the compression chamber B, and the compression efficiency can be improved.

  In addition, since the unload valve 20 functions as another suction valve, the outer shape of the suction valve 13 and the unload valve 20 can be made smaller than when only the suction valve 13 is used. For this reason, the seating sound when the suction valve 13 and the unload valve 20 are closed can be reduced, and the noise can be reduced.

  In addition, since the thickness dimension T1 of the suction valve 13 and the thickness dimension T2 of the unload valve 20 are set so that the opening timings of the suction valve 13 and the unload valve 20 are different from each other, The unload valve 20 does not open together. Thereby, since the timing at which the suction valve 13 and the unload valve 20 are closed can also be made different from each other, the sounds accompanying the opening and closing of the suction valve 13 and the unload valve 20 may be superimposed on each other. And noise can be reduced.

  Furthermore, since the thickness dimension T1 of the suction valve 13 and the thickness dimension T2 of the unloading valve 20 are set so that the sound frequencies when the suction valve 13 and the unloading valve 20 are closed are different from each other, Compared with the suction valve 13 and the unload valve 20 generating sound of the same frequency, the seating sound when the valve is closed can be reduced, and noise can be reduced.

  Further, since the suction port 12 is provided in the piston 7 and the unload port 19 is provided in the valve plate 6, for example, compared with the case where both the suction port 12 and the unload port 19 are provided in the valve plate 6. The hole diameters of the suction port 12 and the unload port 19 can be increased. For this reason, a sufficient amount of air can be sucked into the compression chamber B through these ports 12 and 19, and the compression efficiency can be improved.

  In particular, in this embodiment, since the bypass pipe 22 opened in the crankcase 1 is connected to the unload port 19, the sound generated by the unload valve 20 does not leak directly to the outside and bypass It can be led into the crankcase 1 through the pipe 22. Further, since the suction port 12 is provided in the piston 7, the sound generated by the suction valve 13 can also be released to the outside through the crankcase 1. For this reason, the sound generated by the suction valve 13 and the unload valve 20 is not directly released to the outside but passes through the crankcase 1, so that the sounds of the valves 13 and 20 can be reduced in the crankcase 1. , Noise can be reduced.

  In the above-described embodiment, when the thickness dimension T1 of the suction valve 13 and the thickness dimension T2 of the unload valve 20 are made different from each other, the timing at which both the valves 13 and 20 open and the seat surface collide. The frequency of the sitting sound at the time is different from each other. However, the present invention is not limited to this. For example, as shown in the modified examples of FIGS. 7 and 8, the free length L1 of the suction valve 13 '(the length dimension from the fixed pin 13A' to the free end) and the unload valve By varying the free length L2 of 20 '(the length dimension from the fixed pin 20A' to the free end), the timing at which both valves 13 'and 20' open, and the seating sound when colliding with the seating surface The frequency may be different from each other, or the shape and material of the suction valve and the unload valve may be different.

  In the embodiment, the suction port 12 is provided in the piston 7 and the unload port 19 is provided in the valve plate 6. However, the present invention is not limited to this. For example, both the suction port and the unload port may be provided on the valve plate, and the suction valve and the unload valve may be attached to the valve plate.

  Moreover, in the said embodiment, the rod 10 was integrally formed in the piston 7, and it applied to the rocking | fluctuation type air compressor which reciprocates while the piston 7 rock | fluctuates. However, the present invention is not limited to this, and the piston and the rod are formed separately from each other, and the piston and the rod are connected using a piston pin, and the piston reciprocates in a cylinder in a parallel state. It may be applied to a compressor.

  In the above-described embodiment, the push solenoid 21 in which the shaft 21A is advanced and retracted by electrical excitation is used as the unload mechanism. However, for example, a pneumatic unload mechanism in which the shaft is advanced and retracted by air pressure is used. It is good.

  Moreover, in the said embodiment, although it was set as the structure which connects the bypass piping 22 opened in the crankcase 1 to the unload port 19, for example, it is also possible to omit the bypass piping and to connect the unload port directly to the outside. Good. In this case, it is preferable to attach a silencer to the unload port in order to reduce the noise of the unload valve or the like.

  Furthermore, although the air compressor has been described as an example in the embodiment, the present invention can be applied to various reciprocating compressors that compress a fluid other than air, such as a gas or a refrigerant.

It is sectional drawing which shows the state from which the air compressor by embodiment of this invention became the suction stroke during load operation. It is sectional drawing which shows the state which became the discharge stroke in the air compressor in FIG. It is sectional drawing which shows the state in which the air compressor in FIG. 1 is carrying out unloading operation. It is a principal part expanded sectional view which expands and shows the cylinder, piston, valve plate, etc. in FIG. It is a top view shown in the state which attached the discharge valve and the unloading valve to the valve plate in FIG. It is a top view shown in the state which attached the suction valve to the retainer of the piston in FIG. It is a top view similar to FIG. 5 shown in the state which attached the discharge valve and the unload valve to the valve plate by a modification. It is a top view similar to FIG. 6 shown in the state which attached the suction valve to the retainer of the piston by a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Crankshaft 5 Cylinder 6 Valve plate 7 Piston 9 Retainer 10 Rod 12 Suction port 13, 13 'Suction valve 14 Discharge port 15 Discharge valve 19 Unload port 20, 20' Unload valve 21 Push solenoid (Unload mechanism) )
22 Bypass piping (bypass flow path)
A Crank chamber B Compression chamber C Discharge chamber D Unload chamber

Claims (4)

A crankcase that supports the crankshaft inside, a cylinder attached to the crankcase, and a rod that is connected to the crankshaft and is removably inserted into the cylinder so as to be compressed on the tip side of the cylinder A piston that defines a chamber, a suction port that sucks an external fluid into the compression chamber, a suction valve that is provided in the suction port and that opens in the suction stroke and closes in the discharge stroke; and compressing fluid from the compression chamber In a reciprocating compressor comprising a discharge port for discharging, and a discharge valve provided in the discharge port and closed in a suction stroke and opened in a discharge stroke,
An unloading port that communicates the compression chamber with the outside is provided,
The unload port is forcibly opened when the unload mechanism is operated to perform unload operation, and when the unload mechanism is not operated, the unload valve opens during the intake stroke and closes during the discharge stroke. A reciprocating compressor characterized in that it is configured to provide. The suction valve and the unload valve are each formed in a plate shape having one end as a fixed end and the other end as a free end,
The suction valve and the unload valve are different from each other in at least one of their thickness, shape, and material, so that the opening timing and the sound frequency when the valve is closed The reciprocating compressor according to claim 1, wherein the reciprocating compressor is configured to be different. Provided on the tip side of the cylinder is a valve plate that defines a compression chamber with the piston,
The discharge port and the unload port are provided in the valve plate,
The reciprocating compressor according to claim 1, wherein the suction port is provided in the piston and sucks fluid in the crankcase into the compression chamber.   The reciprocating compressor according to claim 3, wherein a bypass flow path opened in the crankcase is connected to the unload port.

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