JPS58129718A - Vacuum interrupter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to vacuum interrupters, and more particularly to a vacuum interrupter comprising means behind the electrodes for generating an axial magnetic field parallel to the arc.

In recent years, by applying an axial magnetic field parallel to the arc, it is possible to disperse the arc on the electrode surface and prevent its local concentration, thereby preventing excessive melting of the electrode. A so-called vertical magnetic field type (arc dispersion type) vacuum interrogator with improved performance is known.

Such a vertical magnetic field type vacuum interrupter brings a pair of electrodes into contact with and away from each other through a pair of electrode rods that are positioned on the axis of the vacuum container and introduced so that they can move toward and away from each other.
ili6) At the same time, each city (V) and the inner end of each electrode rod are arranged at the back of the electrode, and the current flowing through the electrode rod is changed to a loop current centered on the electrode rod, and the axial direction A coil that generates a magnetic field (magnetic field generator)
Generally, it is configured to be electrically connected to each other.

In order to increase the carrying current capacity of such a vertical magnetic field type vacuum interrupter, it is possible to use a shunt type coil, but the strength of the axial magnetic field decreases in inverse proportion to the number of divisions of the coil, and the breaking ability decreases. There is a problem with doing so. To deal with this problem, the optimal axial magnetic field for cutting off large currents when the electrodes are made of stainless steel, for example, has a magnetic flux density of 40 to 60 G/K.
It has been confirmed by experiment that A is the case, and the magnetic flux density of the axial magnetic field when the outer diameter of the stainless steel electrode and the coil is 100 m+*, and the gap between the electrodes and the number of divisions of the coil are changed. As can be seen from the following table showing the calculated value of and the result of suppression, it is known that it is sufficient to use a 1 turn coil with a division number of 0 or a 1A turn coil with a division number of 2.

However, the coils and the like of vertical magnetic field type vacuum interrupters have conventionally been cut off by one hair, as shown in Fig. 1, 2g and 2. That is, in FIG. 1, reference numeral 1 denotes an electric conductor, and as shown in FIG. Two arm portions 2b extend outward in the radial direction (horizontal direction in FIGS. 1 and 2) from symmetrical positions, and from the end of each arm portion 2b toward the end of the adjacent arm portion 2b. The cap-shaped disk-shaped electrode 5 is fitted through one side of the same directionality 4, and is recessed in the center of the back (lower surface in FIG. 1) of the fourth part 6 and the attachment part 2a of the coil 2. a truncated cone-shaped electrode insulating support 7 whose both ends are fitted into the other recess 4;
They are fixed in series through. The coil 2 and the electrode 5 are connected in the axial direction (up and down in FIG. It is electrically connected via the current-carrying bottle 9 in the direction (direction).

The electrode insulating support 7 is for supporting the electrode 5 on the electrode rod 1 while preventing the electrode rod 1 and the electrode 5 from being directly electrically connected. It is made of electrically insulating materials such as resistive metals or ceramics. Further, in FIG. 1, reference numeral 10 denotes a coil reinforcing body for reinforcing and supporting the coil 2, and is made of stainless steel or the like.

However, in the conventional coils and the like described above, the magnetic field generating section is divided into two in the circumferential direction, and therefore requires a radial arm section, resulting in a decrease in mechanical strength and a loss of the axial magnetic field. Furthermore, since it is connected to the electrode via a current carrying pin, there is a problem that it cannot withstand use due to heat generation due to insufficient current carrying capacity.

The present invention has been made in view of the above-mentioned problems, and its purpose is to divide the magnetic field generating part concentrically in the radial direction, and to form a cylindrical part in which each magnetic field generating part is provided as a pole. By electrically connecting the electrode and the electrode rod through the cylindrical part of the intermediate lead body fixed to the electrode rod, a vertical conductor that can conduct a large amount of current and cut off with excellent cutting performance. To provide a magnetic field type vacuum interrupter. Hereinafter, embodiments of the present invention will be described and explained in detail with reference to the drawings from FIG. 3 onwards.

As shown in FIG. 3, the vacuum interrupter according to the present invention has a pair of electrode rods 12 positioned on the axis of a cylindrical vacuum container 11 and introduced so as to be able to approach and separate from each other. A pair of cap-shaped disk-shaped electrodes 13 that are brought into contact and separated in order to input and cut off a large amount of current to the inner end of the pole rod 12 are fixed in series with an electrically insulating support member interposed, and each electrode The rod 12 and each electrode 13 are arranged at the back of the electrode 13, and the axial current (vertical direction in FIG. 3) flowing through the electrode rod 12 is changed to fc, a loop current centered around the electrode rod 12. It is generally constructed of a coil 14 that generates an axial magnetic field.

That is, the vacuum container 11 is made of a metal material such as Kovar, which has a plurality (two in this embodiment) of insulating cylinders 15 formed into a cylindrical shape made of glass or alumina ceramics and hermetically connected to both ends of each insulating cylinder 15. One of the thin cylindrical sealing fittings 16, 16°... is connected to form a single insulating cylinder, and both open ends are connected to the other sealing fitting 16, 16 to form a disc-shaped metal end plate. 17, 17 are hermetically sealed and the inside is evacuated to a high vacuum. The pair of electrode rods 12 are introduced into the vacuum container 11 through holes 17a provided in the center of each metal end plate 17 so as to be able to approach and separate from each other while maintaining the airtightness of the vacuum container 11. There is.

Note that one (upper in FIG. 3) electrode rod 12 is hermetically joined to one metal end plate 17.
The other electrode rod 12 is connected to the hole 17 of the other metal end plate 17 while maintaining the airtightness of the vacuum container 11 with the metal bellows 18.
It is inserted through the tube so as to be freely movable in the axial direction, and is driven back and forth via an operating device (not shown) disposed outside the vacuum container 11. In FIG. 3, reference numeral 19 denotes a cylindrical main shield concentrically surrounding the electrodes 13, 18, etc., and a ring disk-shaped support fitting 2o is sandwiched near the middle part by the one sealing fitting 16. J, 21 is an auxiliary shield fixed to the inner surface of each metal end plate 17, and the other (movable side) electrode rod 1 is supported by J.
At the inner end of the coil 14, as shown in FIG.
The intermediate lead body 22 constituting a part of the electrode 13 is fitted through a recess 23 recessed in the center of one surface of the mounting portion 22a, which is formed in a disk shape with approximately the same diameter as the outer diameter of the electrode 13, and is fixed by brazing. has been done. A first cylindrical portion 22b having the same outer diameter as the mounting portion 22a and a second cylindrical portion 22c having approximately the same outer diameter as the electrode rod 12 are integrally molded concentrically on the other surface of the mounting portion 22a. , 22c are provided with a stepped portion 24 on the opposing inner and outer peripheral surfaces in order to facilitate the fitting of a magnetic field generator, which will be described later.
, 25 are formed. The intermediate lead body 22 is used to electrically connect the magnetic field generating body and the electrode rod 12, which are arranged concentrically in the same plane in the radial direction (the left-right direction in FIGS. 3 and 4), as described later. One surface of the mounting portion 22a is secured by a reinforcing fitting 26 that is shaped like a ring disk and is made of a metal with high mechanical strength such as austenitic stainless steel, which is fitted near the inner end of the electrode rod 12. Brazing is joined and reinforced. The second cylindrical portion 2 on the other surface of the attachment portion 22a of the intermediate lead body 22
The portion surrounded by 2c has flange portions 27a at both ends.
A cylindrical electrode insulating support member 27 made of a high electrical resistance metal such as austenitic stainless steel or an electrical insulator such as ceramics is integrally molded with 7 flange portions 27a at the tip of each cylindrical portion 22b, 22c. It protrudes from the opening end, is fitted through the flange portion 27b at the base end, and is fixed by brazing.

The electrode insulating support member 27 has a cylindrical portion 18a having an outer diameter approximately intermediate between the first cylinder m22b and the second cylindrical portion 22c of the intermediate lead body 22 on the back (lower surface in FIG. 4).
The cylindrical portion 13a of the electrode 13 is integrally formed with the cylindrical portions 22b and 22c of the intermediate lead body 22 in the radial direction, and a recess 28 formed in the center of the back surface is formed in the flange portion at the tip. 27a and is fixed by brazing. The first cylindrical part 22b of the intermediate lead body 22 and the cylindrical part 13a of the electrode 13, as well as the cylindrical part 18a of the electrode 13 and the second cylindrical part 22c of the intermediate lead body 22, each work together with the intermediate lead body 22. The first magnetic field generating body 29 and the second magnetic field generating body 30, which constitute the coil 14, are connected in the same direction. 1st
The magnetic field generator 29 and the second magnetic field generator 30 generate an axial magnetic field by changing the current path into a loop centered on the electrode rod 12, as shown in FIGS. 4 and 6. outer ring portions 29a and 30a that fit with the inner peripheral surface of the first cylindrical portion 22b of the intermediate lead body 22 and the inner peripheral surface of the cylindrical portion 18a of the electrode 18 and are fixed by brazing;
The outer peripheral surface of the cylindrical portion 13a of the electrode 13 and the intermediate lead body 2
Inner ring portions 29b and 30b that fit onto the outer peripheral surface of the second cylindrical portion 22C of No. 2 and are fixed by brazing, and the respective outer ring portions 29a and 30a and the inner ring portion 29
1) and 30b through 7! j:'l In order that the flow flows in the same circumferential direction as shown by the arrows, the ring should preferably be formed into an annular shape with an end having an outer diameter intermediate between the two ring parts and provided with radial connecting parts at both ends. It consists of two magnetic field generating parts 29c and 80c, each part of which has a long rectangular cross section extending in the axial direction, and each part is integrally molded.

In FIG. 4, reference numeral 31 indicates a gas vent hole during brazing between the intermediate lead body 22 of the electrode insulating support 27 and the electrode 13. Further, the electrode 13, coil 14, etc. fixed to the inner end of one (fixed side) electrode rod 12 are substantially the same as the other electrode rod 12 described above, and therefore their explanation will be omitted.

The vacuum interrupter with the above configuration is similar to the previous one. A large amount of current is applied and cut off by connecting and separating the pair of electrodes 13 to the operating device, and the current flows from the electrode rod to the attachment part 22a of the intermediate lead body 22,゜Second cylindrical portion 22b, 22cK:
As shown in FIG. 5, the currents that are divided into the first and second cylindrical parts 22b and 22c are divided into the outer ring part 29a, the magnetic field generator 29c, and the inner ring part of the first magnetic field generator 29, respectively. 29b and the cylindrical portion 18a of the electrode 13 to reach the electrode 13, as well as the inner ring portion 30b of the second magnetic field generator 30, the magnetic field generating portion 30c, the outer ring portion 30a, and the cylindrical portion 13a of the electrode 13 to the electrode 13. . Therefore, in addition to the fact that the magnetic field generating parts 29c and 30c of each magnetic field generating body 29.80 are arranged concentrically in the radial direction, each coil 14 has an outer ring part 29a and an inner ring part 3ob, respectively. and the first cylindrical portion 22b of the intermediate lead body 22
, the electrode rod 12 through the second cylindrical portion 22c, etc., and the groove is connected to the electrode 13 through the inner ring portion 29b, outer ring portion 30a, and cylindrical portion 13a of the electrode 13, so that it can be connected to the electrode 13 through the inner ring portion 29b, the outer ring portion 30a, and the cylindrical portion 13a of the electrode 13. Since the cross-sectional area for current flow is larger than that of other products, it does not generate heat or the like and can withstand use with large currents.

Moreover, the magnetic field generating part 29c of each magnetic field generating body 29.30.

The axial magnetic field generated by 30c [with current carrying capacity - Of course, it can improve the first. Magnetic field generating section 2 of second magnetic field generating body 29.30
By making the interval 9c r 30c as narrow as possible, the second magnetic field generator 30 corresponds to the flat part (contact energizing part) 18b where an arc first occurs in the electrode 13.
The magnetic field inside the magnetic field generating section 30c of the first magnetic field generating section 30c is strengthened, and the first magnetic field generating section 2 corresponding to the periphery of the slope section 13C of the electrode 13 is strengthened.
Since the magnetic field outside the magnetic field generating section 29C of 9 is strengthened and the direction of the magnetic lines of force interlinking with the electrode 13 is opposite, eddy currents occur in the flat part 13b and the slope part 1.3c of the electric current Q]8. is in the opposite direction. Therefore, the eddy current immediately after a large current is interrupted is immediately canceled out to zero, and the axial magnetic field and the current zero point coincide (same phase), resulting in good insulation recovery characteristics and, as a result, the breaking bond strength. can be improved.

Note that in the above-mentioned embodiment, 1 is the intermediate lead body 22.
Although the case has been described in which two cylindrical parts 22b and 22C are provided in the electrode 13 and one cylindrical part 18a is provided in the electrode 13, the present invention is not limited to this. In addition to providing the intermediate lead body 2
2 may be provided with one cylindrical portion, and each of the intermediate lead body 22 and the electrode 13 may be provided with two or more cylindrical portions.

Further, in the above-mentioned embodiment, a case was described in which the magnetic field generating parts 29c and 80c of the concentric magnetic field generating bodies 29.80 were provided so that the direction of the current flowing was the same, but the present invention is not limited to this, for example. As shown in FIG. 6, the respective magnetic field generating portions 29C and 230ci, the outer ring portions 29a and 30a, and the inner ring 29b such that current flows in opposite directions.

30b, and by providing it in this way, the axial magnetic fields generated by the magnetic field generators 29 and 30 become alternating MIS fields with different polarities, so this alternating longitudinal magnetic field Therefore, the directions of the eddy currents generated in the electric current 13 are also opposite to each other. Therefore, the phases of the cutoff current and the magnetic field at the time of cutoff match, and the cutoff performance can be improved.

Furthermore, the magnetic field generating portion 29C of each magnetic field generating body 29.80,
30c is not limited to a single ring-shaped pigeon coop with ends, but for example, as shown in Figure 7, a pigeon coop made of two semicircular arc-shaped pieces, or divided into three or more pieces in the circumferential direction. It is formed from an arc-shaped part or an external magnetic field generating part.

'80c may be formed as two semicircular arcs or three or more circular arcs, and by providing them in this way, the current carrying capacity t can be further improved, and
Heat generation from the magnetic field generators 29 and 30 can be made uniform.

Further, each part of each magnetic field generating body 29.80 is not limited to being integrally molded, and may be formed by joining each part formed separately, and the respective outer ring parts 29a, 30
a and the inner ring portion 29b.

The magnetic field generating body 29.30 may be formed only by the magnetic field generating parts 29c and 80c without providing the magnetic field generating body 30b, and each magnetic field generating body 29.30 may be formed by a plurality of magnetic field generating elements superimposed in the axial direction. It's also good.

FIG. 8 is a longitudinal cross-sectional view of a main part of a second embodiment of the present invention. In this embodiment, two magnetic field generators 29 and 30 of the coil 14 are provided spaced apart in the axial direction. and a ring-disc-shaped first ring between the two. Second connection conductor 32
．． This embodiment is different from the first embodiment described above in that the strength of the axial magnetic field is improved by connecting the magnets 88 in series. Therefore, the same members as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

That is, the electrode 130 cylindrical portion 13a and the intermediate lead body 22
The open end and the second magnetic field generator 30 are fitted into the cylindrical parts 22b and 22c through the inner ring part 29b and the outer ring part 30a, respectively, and the intermediate lead body 2
2, the inner circumferential surface of the first cylindrical portion 22b and the second cylindrical portion 22c
The other first magnetic field generating body 29 and second magnetic field generating body 30 are fitted onto the outer peripheral surface of the magnetic field generating body 29 through an outer ring portion 29a and an inner ring portion 30b, respectively. Then, the outer ring part 29a of the first magnetic field generator 29, which is spaced apart in the axial direction and fitted onto the outer peripheral surface of the cylindrical part 13a of the electrode 13, is fitted into the inner peripheral surface of the first cylindrical part 22b of the intermediate lead body 22. The first
The inner ring portion 29b of the magnetic field generator 29 is electrically connected to the inner ring portion 29b of the ring disk-shaped first connection conductor 32 through projecting edges 82a and 32b formed on the outer and inner edges of the ring disk-shaped first connection conductor 32 so as to protrude in mutually different axial directions. The outer ring portion 30a of the second magnetic field generator 30 and the second cylindrical portion 22c of the intermediate lead body 22 are connected in series and are similarly spaced apart in the axial direction and fitted onto the inner peripheral surface of the cylindrical portion 18a of the electrode 13. The inner ring part 30b of the second magnetic field generating body 30 fitted on the outer peripheral surface of the second magnetic field generating body 30 is a protrusion formed on the outer peripheral edge and the inner peripheral edge of the second connecting conductor 33 in the shape of a ring disk in the same manner as the first connecting conductor 32. Rim 33a
and 83b are electrically connected in series.

Note that in the second embodiment described above, the intermediate lead body 2
The cylindrical portions 22b and 22c of the second embodiment are two, and the cylindrical portion 13a of the electrode 13 is one. However, the present invention is not limited to this. Of course, the cylindrical portions 13 a f of 13 may be two, and the cylindrical portion of the intermediate lead body 22 may be one.
and the cylindrical portion of the intermediate lead body 22, respectively.
It is also possible to have more than one.

In addition, it goes without saying that each magnetic field generator 29, 30 can be modified in various ways as in the case of the first sister example described above, and the outer ring portions 29a, 30a and the inner ring portion 29.
It is sufficient that at least one of 9b and 80b is provided.

As described above, in the present invention, 1 ? The electrode rod j is positioned on the axis and introduced so that it can be relatively approached and separated,
An intermediate lead body having one or two or more concentric cylindrical parts is concentrically fixed to the inner end of each of the electrode rods with the open ends of the cylindrical parts facing each other, and the cylindrical part of the intermediate lead body An electrode having one or two or more concentric cylindrical parts with different diameters on the back side, the cylindrical parts are alternately overlapped concentrically in the radial direction with the cylindrical part of the intermediate lead body, and the electrodes are interposed through an electrode insulating support. fixed in series, and connecting the cylindrical portion of each intermediate one-piece body and the cylindrical portion of each adjacent electrode by a magnetic field generating body having an end ring shape or an arc shape divided into two or more in the circumferential direction. Since the current carrying capacity is not restricted due to the generation of resistance heat at the connection between the coil and the electrode, unlike conventional ones, it is also possible to handle large currents with excellent breaking performance. can be cut off,
Moreover, it is possible to easily set the strength and distribution of the axial magnetic field.

Further, a pair of electrode rods are positioned on the axis line and introduced into the vacuum container so as to be able to approach and separate from each other, and each electrode rod has one or two or more concentric cylindrical portions at the inner end thereof. The intermediate lead body is fixed concentrically with the open end of the cylindrical part facing each other, and the diameter is different from that of the cylindrical part of the intermediate lead body.
The idea is to use an electrode with two or more concentric cylindrical parts on the back, and to separate the open end of the cylindrical part from the open end of the cylindrical part of the intermediate lead body in the axial direction, and to separate the cylindrical part from the open end of the cylindrical part of the intermediate lead body. An outer ring is attached to the cylindrical portion of each intermediate lead body and the cylindrical portion of each adjacent electrode, and is fixed in series through an electrode insulating support such that the cylindrical portion and the cylindrical portion are alternately overlapped concentrically in the radial direction. A magnetic field generating body having an end ring shape or an arc shape divided into two or more parts in the circumferential direction is fitted into the cylindrical part of each of the intermediate lead bodies. Since the magnetic field generator and the magnetic field generator fitted into the cylindrical portion of each electrode are formed into ring disks and are connected in series by a connecting conductor having protrusions on the inner and outer edges, the above-mentioned effects can be achieved. In addition to this, the strength of the axial magnetic field can be significantly improved.

[Brief explanation of drawings]

1 and 2 are a vertical cross-sectional view and a plan view of the main parts of a conventional vacuum interrupter, respectively, FIG. 3 is a vertical cross-sectional view of a vacuum interrupter according to the present invention, and FIG. 4 is a first embodiment of the present invention. FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 4, FIGS. 6 and 7 are cross-sectional views of other embodiments of the main part of the first embodiment, and FIG. The figure is a longitudinal sectional view of the main part of the second embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Vacuum container, 12... Electrode rod, 13... Electrode, 18a... Cylindrical part, 22... Intermediate lead body, 2
2b. 22C...Cylindrical part, 27...Electrode, electrode insulating support, 2
9°30...Magnetic field generator, 32.33...Connecting conductor, 32a. 82 b, 83 a, 33 b - ridge. 1 Figure 1 Figure 2

Claims (1)

[Scope of Claims] (1) A pair of electrode rods are positioned on the axis line and introduced into a vacuum container so as to be able to approach and separate from each other, and one or a concentric electrode is inserted into the inner end of each of the electrode rods. An intermediate lead body having two or more cylindrical parts is fixed concentrically with the open ends of the cylindrical parts facing each other, and the diameter is different from that of the cylindrical part of the intermediate lead body.
Alternatively, an electrode is provided with two or more concentric cylindrical parts on the back, and the cylindrical parts are alternately overlapped concentrically in the radial direction with the cylindrical part of the intermediate lead body, and the electrodes are fixed in series via an electrode insulating support, The cylindrical portion of each intermediate lead body and the cylindrical portion of each adjacent electrode are connected by a magnetic field generating body having an end ring shape or an arc shape divided into two or more parts in the circumferential direction. Vacuum interrupter. (2) A vacuum according to claim 1, characterized in that a concentric magnetic field generating body is connected to the cylindrical part of the intermediate lead body and the cylindrical part of the electrode so that the 11 currents flow in the same direction. Interrupter. (3) The first aspect of the present invention is characterized in that the concentric magnetic field generators are connected to the cylindrical portion of the intermediate lead body and the cylindrical portion of the electrode in such a manner that current flows through the concentric magnetic field generators while changing directions alternately.
Vacuum interrupter as described in section. (4) Claims 1 to 3, characterized in that the inner part of the concentric magnetic field generator is annular with ends, and the outer part is in the shape of two or more circular arcs. Pages listed in any of the sections up to the empty interrupter. (5) The vacuum interrupter according to any one of claims 1 to 4, 1, characterized in that the magnetic field generating body is formed of two or more magnetic field generating elements superimposed in the axial direction. . (6) Claims 1 to 1, characterized in that the magnetic field generator is provided with an outer ring portion and an inner ring portion that are fitted into the cylindrical portion of the intermediate lead body or the cylindrical portion of the electrode. The vacuum interrupter according to any one of items 5 to 5. (7) A pair of electrode rods are positioned on the axis line and introduced into the vacuum container so that they can be moved toward and away from each other, and one or more concentric cylindrical portions are attached to the inner end of each electrode rod. The intermediate lead body provided with the intermediate lead body is fixed concentrically with the open end of the cylindrical part facing each other, and the diameter is different from that of the cylindrical part of the intermediate lead body.
An electrode having two or more twisted or concentric cylindrical parts on its back is separated in the axial direction from the open end of the cylindrical part and the open end of the cylindrical part of the intermediate lead body, and the cylindrical part is separated from the open end of the cylindrical part of the intermediate lead body. The electrodes are alternately overlapped concentrically with the cylinder in the radial direction, and are fixed in series through the electrode insulating support, and are externally attached to the cylindrical part of each of the intermediate lead bodies and the cylindrical part of each adjacent electrical wire. An arcuate magnetic field generating body divided into two or more in the circumferential direction is fitted into the circular arc-shaped magnetic field generator having both or one of the ring part and the inner ring part, and the cylindrical part of each intermediate lead body. The magnetic field generating body fitted into the cylindrical part of each electrode and the magnetic field generating body fitted into the cylindrical part of each electrode are formed into a ring disc shape and are connected in series by a connecting conductor having protruding edges on the inner and outer peripheral edges. A vacuum interrupter characterized by the following: (8) The vacuum interconnect 2 according to claim 7, characterized in that concentric magnetic field generators are connected to the cylindrical portion of the intermediate lead body and the cylindrical portion of the electrode so that current flows in the same direction. Puta. (9) Claim 7 of the patent, characterized in that the concentric magnetic field generators are connected to the cylindrical portion of the intermediate lead body and the cylindrical portion of the electrode in such a manner that current flows through the concentric magnetic field generators while changing directions alternately. vacuum interrupter. (Claims 7 to 9) characterized in that the inner part of the concentric magnetic field generator is annular with ends, and the outer part is in the shape of two or more circular arcs. (11) The vacuum interrupter according to any one of claims 7 to 10, characterized in that the magnetic field generating body is formed by two or more magnetic field generating elements superimposed in the axial direction. The vacuum inter-tube according to any one of the above.