JP2010013009A - Traveling vehicle system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a traveling vehicle system of a non-contact electric supply system capable of suppressing leakage of a magnetic field from electric supply lines. <P>SOLUTION: This invention relates to the ceiling traveling vehicle system for allowing a traveling vehicle with a receiving pickup to travel, and it is provided with a pair of electric supply lines 17, 17, and a plate member 62 made of a non-magnetic conductor. The pair of electric supply lines 17, 17 are members for supplying electric power to the receiving pickup arranged along the traveling pathway of the ceiling traveling vehicle. The plate member 62 is provided with a main surface section 69 extended along the traveling path, and a pair of side face sections 71, 73 extended from the main surface section 69 and opposed with the pair of electric supply lines 17, 17 interposed between them. The distances L1, L2 from the respective supply lines 17, 17 to the nearer side face sections 71, 73 are the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a traveling vehicle system, and more particularly to a traveling vehicle system that supplies power to a traveling vehicle by a non-contact power feeding method.

  2. Description of the Related Art Conventionally, in a clean room where generation of dust is a problem, such as in a semiconductor manufacturing factory, a technique is known in which a transport carriage is run on a track in order to transport articles. A motor is usually used as a drive source for these transport carts. Further, power is supplied to the motor by electromagnetic induction from two power supply lines installed along the track of the transport carriage.

Hereinafter, a non-contact power feeding method using electromagnetic induction will be described.
The two power supply lines are held by a power supply line holder of a power supply rail provided along the track. A ferrite core having a substantially “E” cross section is fixed to the power receiving unit of the carriage. The protruding piece at the center of the core is wound with a coil, and is inserted between the two feeders in a non-contact manner. By flowing a high-frequency current through the feeder line, the magnetic field generated there acts on the coil wound around the core, and as a result, an induced current flows through the coil. As described above, electric power is supplied from the power supply line to the power receiving unit of the transport carriage in a non-contact manner, and the electric power is used in the motor and the control device (see, for example, Patent Document 1).
JP 2002-234366 A

  As described above, a magnetic field is generated from the non-contact power feeding line of the traveling vehicle system, and a part of the magnetic field leaks to the outside from the power feeding rail. When the traveling vehicle system is employed in a semiconductor factory, the leakage magnetic field from the power supply rail may affect the electron beam inspection apparatus and cause erroneous measurement. In particular, there is a concern about the problem of erroneous measurement as the number of nodes in the semiconductor design rule increases.

  The subject of this invention is providing the traveling vehicle system of the non-contact electric power feeding system which can suppress the leakage of the magnetic field from a feeder.

  The traveling vehicle system according to the present invention is a system for traveling a traveling vehicle having a power receiving pickup, and includes a pair of power supply lines and a plate member made of a nonmagnetic conductor. The pair of power supply lines is a member that is arranged along the travel route of the traveling vehicle and supplies power to the power receiving pickup. The plate member has a main surface portion extending along the traveling path, and a pair of side surface portions extending from the main surface portion and facing each other with a pair of power supply lines interposed therebetween. The distance from each of the pair of power supply lines to the pair of side surfaces on the near side is the same.

  In this system, since the plate member is a non-magnetic material, the magnetic field generated from the feeder line is difficult to leak to the outside. This is because an eddy current is generated in the plate member to constitute a magnetic shield. Therefore, it is difficult for other devices to be adversely affected by the leakage magnetic field. Further, by making the distance from each of the pair of power supply lines to the pair of side surfaces closer to each other, the balance of the magnetic fields respectively generated from the pair of power supply lines can be maintained. Thereby, the effect that it is hard to give the bad influence by a leakage magnetic field to another apparatus becomes high.

  It is preferable that the pair of side surface portions have the same length extending from the main surface portion, and the tips of the pair of side surface portions extend to a position covering the pair of power supply lines. In this case, since the length of the pair of side surface portions extending from the main surface portion is the same, the balance of the magnetic fields generated from the pair of power supply lines can be maintained. Thereby, the effect that it is hard to give the bad influence by a leakage magnetic field to another apparatus becomes high. Furthermore, since the front ends of the pair of side surfaces extend to a position covering the pair of power supply lines, the magnetic field generated from the power supply lines is less likely to leak to the outside.

  The traveling vehicle system further includes a resin holder that is provided continuously along the traveling path and holds a pair of power supply lines, and the plate member is disposed on the pair of power supply lines with respect to the holder. It is preferable. In this case, since the plate member is arranged inside the holder, even if another member collides with the traveling vehicle system, it is difficult for dust from the plate member to come out. As a result, even if the traveling vehicle system is applied in a clean room, a problem hardly occurs.

  It is preferable that the holder is continuous along the travel path and holds the plate member inside. The traveling vehicle system further includes an inner holder that is held by the holder and fixes the plate member to the holder and holds a pair of power supply lines. In this case, since the inner holder has a holding function of the plate member and a holding function of the feeder line, the number of parts is reduced.

  Further, the inner holder preferably has a plurality of holder members. In this case, since the inner holder is composed of a plurality of members, assembly / disassembly workability is improved. That is, the holder member is a small member with respect to the outer holder or the plate member, and when fitted, the fitting operation can be performed without strict positioning with respect to the outer holder or the plate member. Moreover, since it is only necessary to remove small members one by one when removing them, workability is good. Furthermore, when the plurality of holder members are partially disposed, many portions of the main surface portion of the plate member are exposed. Therefore, it is difficult for the inner holder to reduce the magnetic flux.

  There are a total of two pairs of a pair of power supply lines and plate members, which are preferably arranged on both sides of the traveling path. The main surface portion of the plate member is disposed on the lateral outer side of the pair of power supply lines, and the pair of side surface portions extends to the other copper plate member side.

  In the traveling vehicle system according to the present invention, since the balance of the magnetic fields generated from the pair of power supply lines can be maintained, the effect that the adverse effect due to the leakage magnetic field is less likely to be exerted on other devices is enhanced.

An embodiment of the present invention will be described with reference to the drawings.
(1) Overhead Traveling Vehicle System FIG. 1 is a schematic diagram of an overhead traveling vehicle system 1 using a non-contact power supply method using a power supply line. The overhead traveling vehicle system 1 is provided in a clean room or the like such as a semiconductor factory, and carries a FOUP (Front Opening Unified Pod) described later. The overhead traveling vehicle system 1 mainly includes a rail 3 and an overhead traveling vehicle 5 that travels along the rail 3.

  The configuration in the semiconductor factory will be described. The semiconductor factory has a plurality of bays (processes), an interbay route 51 is provided for connecting remote bays, and each bay has an intrabay route 53. Each of the routes 51 and 53 is constituted by the rail 3.

A plurality of processing devices 55, 55 such as semiconductor processing devices are arranged along the intra-bay route 53. Further, a load port 57 is provided in the vicinity of the processing devices 55 and 55. The load port 57 is provided directly below the intra-bay route 53. In the above configuration, the overhead traveling vehicle 5 travels on the rail 3 and conveys a FOUP described later between the load ports 57.
(2) Rail As shown in FIG. 2, the rail 3 is suspended from the ceiling 9 by a plurality of columns 7. The rail 3 mainly includes a travel rail 11 and a power supply rail 13 provided at the lower portion of the travel rail 11.
(A) Traveling rail The traveling rail 11 is made of, for example, aluminum, and is configured in an inverted U shape in cross section as shown in FIG. 3 and has an upper surface portion 11a and both side surface portions 11b. A pair of first running surfaces 11c extending inward are formed below the side surface portions 11b. Further, a second traveling surface 11d is formed on the upper side of the inner side surface of both side surface portions 11b, and a third traveling surface 11e is formed on the lower side surface of the upper surface portion 11a.
(B) Feeding rail The feeding rail 13 is mainly composed of a pair of feeding line holders 15, 15 provided on both lower sides of the traveling rail 11. A pair of power supply lines 17, 17 made of litz wires in which conductive wires such as copper wires are covered with an insulating material are arranged in the power supply line holders 15, 15. A power supply device (not shown) is provided at one end of the power supply line 17 so that a high-frequency current is supplied to the pair of power supply lines 17 and 17.
(3) Overhead traveling vehicle The overhead traveling vehicle 5 mainly includes a traveling unit 21, a power receiving unit 23, and a lifting drive unit 25. The traveling unit 21 is a mechanism that is disposed in the traveling rail 11 and travels on the rail 3. The power reception unit 23 is a mechanism that is disposed in the power supply rail 13 and is supplied with power from the pair of power supply lines 17 and 17. The raising / lowering drive unit 25 is a mechanism that is disposed below the power supply rail 13 and holds the FOUP 4 and moves up and down.
(A) Traveling unit The traveling unit 21 is mainly disposed in the traveling rail 11, and includes a pair of first guide wheels 18, 18, a pair of second guide wheels 19, 19, and a traveling drive wheel 20. And a motor (not shown). The pair of first guide wheels 18, 18 are disposed on both lower sides of the traveling portion 21 and are rotatably supported on an axle extending in the left-right direction. The first guide wheels 18 and 18 are placed on the first traveling surface 11 c of the traveling rail 11.

  The second guide wheels 19, 19 are disposed on both sides of the upper portion of the traveling unit 21, and are rotatably supported on an axle extending in the vertical direction. The second guide wheels 19, 19 prevent the positional deviation in the lateral direction (the lateral direction of the traveling direction) using the second traveling surface 11 d of the traveling rail 11 as a guide surface.

The traveling drive wheel 20 is disposed substantially at the center of the traveling unit 21 and is pressed against the third traveling surface 11e of the traveling rail 11 by a pressing means such as a spring. The traveling drive wheel 20 is driven by a motor (not shown). As a result, the overhead traveling vehicle 5 travels on the rail 3.
(B) Power reception unit The power reception unit 23 includes a pair of pickup units 27 for obtaining power from the pair of power supply lines 17 and 17. Specifically, the pair of pickup units 27 and 27 are arranged side by side in the power supply rail 13. Each pickup unit 27 has a ferrite core 29 having a substantially E-shaped cross section, and a pickup coil 31 wound around the core 29. Specifically, the core 29 has projecting portions 29a on both sides and a central projecting portion 29b therebetween, and the pickup coil 31 is wound around the projecting portion 29b in the center.

A pair of power supply lines 17 and 17 held by the power supply line holder 15 are respectively disposed between the protrusions 29a on both sides and the protrusions 29b on the center. A magnetic field generated by flowing a high-frequency current through the pair of power supply lines 17 and 17 acts on the pickup coil 31, and an induced current is generated in the pickup coil 31. In this manner, electric power is supplied from the pair of power supply lines 17 and 17 to the pickup unit 27 in a non-contact manner, and a driving motor (not shown) is driven or electric power is supplied to a control device. Thus, the non-contact power feeding unit 33 is configured by the pair of power feeding lines 17 and 17 of the power feeding rail 13 and the power receiving unit 23 of the overhead traveling vehicle 5.
(C) Elevating drive unit As shown in FIG. 2, the elevating drive unit (hoist) 25 mainly includes a main body frame 35, a lateral feed unit 37, a θ drive 39, a hoist main body 41, and an elevating platform 43. It has.

  The main body frame 35 is a member fixed to the lower part of the power receiving unit 23. Front and rear frames 45 and 47 are provided before and after the main body frame 35.

  The lateral feed unit 37 laterally feeds the θ drive 39, the hoist body 41 and the lifting platform 43 to the side, for example, and delivers the FOUP 4 to and from a side buffer (not shown) provided on the side of the traveling rail 3. it can. The θ drive 39 rotates the hoist body 41 in a horizontal plane to facilitate delivery of the FOUP 4. In the hoist body 41, lifting means (not shown) for lifting the lifting platform 43 is provided. The elevating means is, for example, four sets of winding drums, and a belt 59 is wound around the winding drums. A lifting platform 43 is attached to the end of the belt 59. FIG. 4 shows a state in which the belt 59 is fed from the take-up drum and the lifting platform 43 is lowered together with the FOUP 4.

The FOUP 4 accommodates a plurality of semiconductor wafers and has a lid that can be opened and closed on the front surface. A flange 49 is provided on the upper part of the FOUP 4, and the flange 49 is chucked by a lifting platform 43.
(4) Feedline holder The structure of the feedline holder 15 will be described with reference to FIGS. In addition, since the structure of a pair of feeder holders 15 and 15 is substantially the same, only one structure is demonstrated.

  The feeder holder 15 includes an outer holder 61, a plate member 62, and an inner holder 63. Both the outer holder 61 and the plate member 62 have a predetermined corresponding length, and a plurality of inner holders 63 correspond to the pair of combinations.

  The outer holder 61 is an integrally formed member made of resin, and mainly includes a main surface portion 65 and a pair of side surface portions 67 and 68 extending laterally from the end portion of the main surface portion 65. The main surface portion 65 extends in the depth direction in FIG. 5 and FIG. 6, and extends in the vertical direction in the cross section. The side surface portions 67 and 68 also extend in the paper depth direction along the main surface portion 65, and extend horizontally from the end of the main surface portion 65 to the right in the cross section. The side surface portion 67 has a first portion 67a on the root side and a second portion 67b extending therefrom. The second portion 67b is thinner than the first portion 67a and has high flexibility. A hook-shaped hook portion 67c is formed on the outer side at the tip of the second portion 67b. The side surface portion 68 includes a first portion 68a on the base side and a second portion 68b extending therefrom. The first portion 68a and the second portion 68b are thin like the second portion 67b of the side surface portion 67, and are highly flexible. A hook portion 68c bent in a hook shape is formed on the outer end of the second portion 68b.

  An engagement portion 67d is formed in the first portion 67a of the side surface portion 67 of the outer holder 61, and an engagement portion 11f (FIG. 3) formed on the lower surface of the traveling rail 11 is engaged therewith. . With this structure, the power supply rail 13 is fixed to the traveling rail 11.

  The plate member 62 is a copper thin plate, and mainly includes a main surface portion 69 and a pair of side surface portions 71 and 73 extending laterally from an end portion of the main surface portion 69. The thickness of the plate member 62 is, for example, 0.3 mm, and preferably in the range of 0.2 to 0.4 mm. The main surface portion 69 extends in the depth direction of the paper surface of FIGS. 5 and 6, and extends in the vertical direction in the cross section. The side surfaces 71 and 73 also extend in the paper depth direction along the main surface 69, and extend horizontally from the end of the main surface 69 to the right in the cross section. The plate member 62 has the same shape as the inner surface of the outer holder 61 and is held in close contact with the inner surface of the outer holder 61. That is, the main surface portion 69 of the plate member 62 is in close contact with the inner surface of the main surface portion 65 of the outer holder 61. The side surface 71 of the plate member 62 is in close contact with the inner surface of the side surface 67 of the outer holder 61. The side surface portion 73 of the plate member 62 is in close contact with the inner surface of the side surface portion 68 of the outer holder 61.

  Next, a structure for keeping the side surfaces 71 and 73 of the plate member 62 in close contact with the side surfaces 67 and 68 of the outer holder 61 will be described. As shown in FIG. 5, a cap 91 is attached to the tips of the side surface portion 71 and the side surface portion 67, and a cap 92 is attached to the tips of the side surface portion 73 and the side surface portion 68. The caps 91 and 92 may be formed continuously along the plate member 62, or may be intermittently arranged, that is, at a plurality of locations. Hereinafter, the cross-sectional structure of the cap 92 will be described in detail with reference to FIG. Since the structure of the cap 91 is the same as that of the cap 92, the description thereof is omitted.

  The cap 92 is made of, for example, resin and has high flexibility. As shown in FIG. 8, the cap 92 has a shape bent in a U shape in cross section, and the distal ends of the side surface portion 73 and the side surface portion 68 are accommodated in the cap 92. A hook portion 93 that engages with the hook portion 68 c is formed at the tip of the outer portion of the cap 92 so that the cap 92 does not fall off from the side surface portion 68. Furthermore, a protrusion 94 that abuts against the side surface portion 73 is formed at the tip of the inner portion of the cap 92. In this way, the both end portions of the cap 92 sandwich the side surface portions 73 and 68, so that the side surface portion 68 is not separated from the side surface portion 73. Furthermore, a protruding portion 95 that protrudes inward is formed at an intermediate bent portion of the cap 92. The engagement of the hook portions 68c and 93 is maintained by the protrusion 95 coming into contact with the tip of the side surface portion 68.

  The inner holder 63 is an integrally formed member made of resin, and a plurality of inner holders 63 are arranged at a predetermined interval with respect to the combination of the outer holder 61 and the plate member 62 as shown in FIG. The pitch of the inner holder 63 is, for example, 150 to 200 mm. Each inner holder 63 includes a main surface portion 75 and a pair of power supply line holding portions 77 and 79 extending laterally from two intermediate positions of the main surface portion 75. The main surface portion 75 of the inner holder 63 is fitted inside the outer holder 61 and is in contact with the main surface portion 65.

  Next, means for fixing the inner holder 63 to the outer holder 61 will be described. A plurality of grooves 81 opened inward are formed in the main surface portion 65 of the outer holder 61, and nuts 82 are disposed therein. Further, a hole 83 with counterbore is formed in the main surface portion 75 of the inner holder 63. Bolts 84 are inserted from the inside into the holes 83, and the bolts 84 are screwed into the nuts 82 through holes (not shown) formed in the main surface portion 69 of the plate member 62.

  As shown in FIG. 3, the pair of power supply lines 17 is disposed at a deep position in the space between the protruding portions 29 a and 29 b of the core 29 while being held at the tips of the power supply line holding portions 77 and 79. Has been.

  By partially disposing the plurality of inner holders 63, many portions of the main surface portion 69 of the plate member 62 are exposed. Therefore, it is difficult for the inner holder 63 to reduce the magnetic flux.

  As apparent from FIG. 5, the distances L <b> 1 and L <b> 2 from the pair of power supply lines 17 and 17 to the pair of side surfaces 71 and 73 of the plate member 62 on the near side are the same. In the figure, L1 and L2 are the shortest distances between them. Since the plate member 62 is a nonmagnetic material, the magnetic field generated from the pair of power supply lines 17 and 17 is unlikely to leak to the outside. This is because an eddy current is generated in the plate member 62 to constitute a magnetic shield. Therefore, it is difficult for other devices to be adversely affected by the leakage magnetic field. In particular, since the plate member 62 is made of copper (high conductivity), the effect of reducing leakage magnetic flux is high. Further, by arranging the plate member 62, the power supply efficiency is improved because the magnetic circuit of the core 29 becomes a closed loop at the time of power supply by electromagnetic induction.

  Further, by making the distances L1 and L2 to the pair of side surfaces 71 and 73 of the plate member 62 closer to each other the same, the balance of the magnetic fields generated from the pair of power supply lines 17 and 17 can be maintained. Thereby, the effect that it is hard to give the bad influence by a leakage magnetic field to another apparatus becomes high.

  Further, the lengths L3 and L4 of the pair of side surface portions 71 and 73 of the plate member 62 extending from the main surface portion 69 are the same, and the tips of the pair of side surface portions 71 and 73 extend to a position covering the pair of power supply lines 17. Yes. The pair of side surface portions 71 and 73 covering the pair of power supply lines 17 and 17 means that the front ends of the pair of side surface portions 71 and 73 are further laterally outer than the side outermost portions of the pair of power supply wires 17 and 17. It means that there is. In this case, since the length of the pair of side surface portions 67 and 68 extending from the main surface portion 69 is the same, the balance of the magnetic fields generated from the pair of power supply lines 17 and 17 can be maintained. Thereby, the effect that it is hard to give the bad influence by a leakage magnetic field to another apparatus becomes high. Furthermore, since the front ends of the pair of side surface portions 71 and 73 of the plate member 62 extend to a position covering the pair of power supply lines 17 and 17, the magnetic field generated from the pair of power supply lines 17 and 17 is less likely to leak to the outside.

  Since the plate member 62 is disposed on the pair of power supply lines 17 and 17 side of the outer holder 61, that is, on the inner side of the outer holder 61, even if another member collides with the overhead traveling vehicle system 1, the plate member 62 Dust is hard to go out. As a result, even if the overhead traveling vehicle system as an embodiment of the present invention is applied in a clean room, problems are unlikely to occur.

  Furthermore, since the inner holder 63 has a holding function of the plate member 62 and a holding function of the pair of power supply lines 17 and 17, the number of parts can be reduced.

  Next, assembling / disassembling work of the feeder holder 15 will be described. First, the plate member 62 is fitted inside the outer holder 61. Next, the caps 91 and 92 are attached to the tips of the side surfaces of both members. In this state, the plate member 62 is temporarily fixed to the outer holder 61. Next, the plurality of inner holders 63 are fitted inside the outer holder 61, that is, inside the plate member 62. Further, the bolt 84 is screwed into the nut 82. Thus, the feeder line holder 15 is assembled. The disassembling operation is the opposite of the above assembling operation.

  Since the inner holder 63 is composed of a plurality of members, the assembling / disassembling workability is improved. That is, the inner holder 63 is a small member with respect to the outer holder 61 and the plate member 62, and when fitted, the fitting operation can be performed without strict positioning with respect to the outer holder 61 and the plate member 62. Further, when removing the inner holder 63, it is only necessary to remove small members one by one, so that workability is good.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of invention.

  In the above embodiment, the plate member is made of copper, but may be an aluminum plate or a stainless steel plate.

  In the embodiment, the bolt and the nut are used to fix the inner holder to the outer holder, but the fixing method is not limited to this. For example, the inner holder is provided with a side portion along the side portion of the outer holder, and the side portion of the inner holder is slightly elastically deformed so that it is fixed to the outer holder by its own elastic force. Also good.

  In the said embodiment, although the plate member was comprised from one plate which has 3 surfaces, you may comprise, for example, combining three plates.

  Although the overhead traveling vehicle system has been described in the above embodiment, the present invention is also applicable to other track traveling vehicle systems such as a floor traveling vehicle.

  In the above embodiment, the traveling vehicle system in the clean room of the semiconductor manufacturing factory has been described, but the present invention can also be applied to other types of factories.

  The pair of power supply lines may be provided in both of the power supply line holders, or may be provided only in one of the power supply line holders.

  The present invention is widely applicable to a traveling vehicle system that travels on a track.

Schematic schematic diagram of an overhead traveling vehicle system in a clean room. The partial side view of an overhead traveling vehicle system and an overhead traveling vehicle. The longitudinal cross-sectional schematic diagram in a rail. The partial side view of an overhead traveling vehicle system and an overhead traveling vehicle. The longitudinal cross-sectional view of an electric power feeding unit. The longitudinal cross-sectional view of the state which decomposed | disassembled the electric power feeding unit into each component. The partial perspective view of a rail. The fragmentary sectional view which shows the engagement state of a cap.

Explanation of symbols

1 Overhead vehicle system 3 Rail 4 FOUP
5 Overhead Car 11 Traveling Rail 13 Power Feeding Rail 15 Power Feeding Line Holder 17 Power Feeding Line 23 Power Receiving Unit 27 Pickup Unit 29 Core 31 Pickup Coil 33 Non-contact Power Feeding Unit 61 Outer Holder (Holder)
62 Plate member 63 Inner holder 65 Main surface portion 67, 68 Side surface portion 69 Main surface portion 71, 73 Side surface portion 75 Main surface portion 77, 79 Feed line holding portion

Claims (6)

A traveling vehicle system for traveling a traveling vehicle having a power pickup,
A pair of power supply lines arranged along a travel route of the traveling vehicle for supplying power to the power pickup;
A plate member made of a non-magnetic conductor, having a main surface portion extending along the travel path, and a pair of side surface portions extending from the main surface portion and facing each other with the pair of power supply lines interposed therebetween;
The distance from each of the pair of power supply lines to the pair of side portions on the near side is the same,
Traveling vehicle system. The length of the pair of side surface portions extending from the main surface portion is the same,
The traveling vehicle system according to claim 1, wherein tips of the pair of side surface portions extend to a position covering the pair of power supply lines. A resin holder provided continuously along the travel path and holding the pair of power supply lines;
The traveling vehicle system according to claim 1, wherein the plate member is disposed on the pair of power supply lines with respect to the holder. The holder is continuous along the travel path and holds the plate member inside,
The traveling vehicle system according to claim 3, further comprising an inner holder that is held by the holder and fixes the plate member to the holder and holds the pair of power supply lines.   The traveling vehicle system according to claim 4, wherein the inner holder has a plurality of holder members. There are a total of two sets of the pair of power supply lines and the plate member, which are respectively arranged on both sides of the travel route,
The traveling vehicle according to any one of claims 1 to 5, wherein the main surface portion of the plate member is disposed on a lateral outer side of the pair of power supply lines, and the pair of side surface portions extends to another plate member side. system.

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