JP7640428B2 - Weft insertion device for air jet loom - Google Patents

Description

The present invention relates to a weft insertion device for an air jet loom equipped with a plurality of supply devices each consisting of an electromagnetic valve and a distributor that distributes air supplied from a supply source via the electromagnetic valve to two sub-nozzles. The distributor includes a main pipe line, one end of which is connected to the electromagnetic valve and the other end of which is closed by a tip wall, and a pair of branch pipe lines that are connected to the other end of the main pipe line and to which corresponding sub-nozzles are connected, and both branch pipe lines are formed so as to face the front-rear direction of the loom.

For example, Patent Document 1 discloses an example of such a weft insertion device for an air-injected loom. In the weft insertion device disclosed in Patent Document 1, multiple sub-nozzles are provided across the width of the loom to transport the weft injected from the main nozzle into the warp shed. The weft insertion device also has multiple supply devices that supply air from a supply source to the sub-nozzles. In this weft insertion device, the sub-nozzles are grouped in groups of multiple from the main nozzle side, and a corresponding supply device is connected to each group of sub-nozzles.

Each supply device is composed of one electromagnetic on-off valve and a distributor that distributes air from the supply source to multiple sub-nozzles via the electromagnetic on-off valve. Inside the distributor, a main pipe line is formed, one end of which is connected to the electromagnetic on-off valve and the other end of which is closed by a tip wall, and multiple branch pipe lines are formed that are connected to the other end of the main pipe line and to which corresponding sub-nozzles are connected. Therefore, air supplied from the supply source to the supply device is sent to the main pipe line via the electromagnetic on-off valve, and then supplied to each sub-nozzle through each branch pipe line.

JP 2003-239160 A

In the supply device of the weft insertion device disclosed in Patent Document 1, the branch pipe in the distributor is formed so as to open to the peripheral wall of the main pipe at the other end side of the main pipe. Note that the air supplied from the electromagnetic valve to the main pipe flows in a direction along the axis of the main pipe (i.e., along the peripheral wall of the main pipe) toward the branch pipe. Therefore, in the configuration of Patent Document 1 (hereinafter referred to as the "conventional configuration"), most of the air that reaches the position of the branch pipe does not flow into the branch pipe, but flows toward the tip side of the branch pipe. Then, the air that flows toward the tip side bounces off the tip wall and flows toward the branch pipe, where it collides with the air from the electromagnetic valve and flows into the branch pipe.

In this way, in the conventional configuration, the flow rate of air flowing toward the tip side (rebounding from the tip wall) is greater than that of the branch pipe, and as a result, the air from the electromagnetic valve side collides with the air that has rebounded from the tip wall, causing severe turbulence in the airflow. As a result of such severe turbulence in the airflow, there is a risk of problems occurring, such as adverse effects on weft insertion.

Furthermore, when the airflow to each branch pipe becomes severely turbulent in this way, it also causes a phenomenon in which it takes a long time for the sub-nozzle's injection pressure to rise to the desired pressure. If it takes a long time for the injection pressure to rise, then in order for the injection pressure to rise to the desired pressure by the time the weft reaches the position of that sub-nozzle, the timing for starting the air supply (the timing for opening the solenoid valve) must be made earlier. This results in a problem of the sub-nozzle's injection period becoming longer, and an increase in air consumption.

The present invention aims to provide a weft insertion device configuration that can reduce the turbulence of the air flow to each branch pipe line, thereby minimizing the effect of the turbulence of the air flow on the weft insertion as much as possible and reducing the amount of air consumed.

To achieve the above object, the present invention is characterized in that in the weft insertion device as described above, each branch pipe is connected to the main pipe in such a way that at least a portion of the branch pipe opens into the tip wall of the main pipe.

In addition, in the present invention, each branch pipe may be formed such that, as viewed in the weft insertion direction, the angle that the center line (a line that passes through the center of the pipe and extends in the extension direction of the pipe) of the branch pipe connected to the upstream sub-nozzle (first branch pipe) makes with the center line of the main pipe is greater than the angle that the center line of the branch pipe (second branch pipe) of the branch pipe connected to the downstream sub-nozzle makes with the center line of the main pipe.

Furthermore, in the present invention, both branch pipes may be formed so that they overlap each other at the end on the main pipe side. Then, after both branch pipes are formed in this manner, each branch pipe may be formed so that the center of the inlet is located within the range of the main pipe when viewed in the longitudinal direction of the main pipe.

According to the weft insertion device of the present invention, each branch pipe line is connected to at least a part of the tip wall of the main pipe line by opening thereon, so that air introduced into the main pipe line and reaching the formation position of the branch pipe line can easily flow directly into each branch pipe line compared to the conventional configuration. As a result, the amount of air bouncing off the tip wall of the main pipe line is reduced compared to the conventional configuration, so that the generation of air currents in the main pipe line that disrupt the air currents flowing into the branch pipe lines is suppressed.

Therefore, according to the configuration of the weft insertion device of the present invention, the airflow to each branch pipe is less likely to be disturbed (airflow turbulence is reduced), so the impact of airflow turbulence on weft insertion is minimized. Furthermore, by reducing airflow turbulence in this way, the time it takes for the injection pressure to rise to the desired pressure is also shortened, so the injection period of the sub-nozzles can be shortened, and the amount of air consumed can be reduced.

In addition, in the weft insertion device according to the present invention, the branch pipes are formed so that the angle of the first branch pipe is larger than that of the second branch pipe in the weft insertion direction, and the flow resistance of the first branch pipe to the air flowing in is smaller than that of the second branch pipe. As a result, the air flows into each branch pipe more smoothly on the first branch pipe side. As a result, the time it takes for the injection pressure to rise to the desired pressure is shorter for the upstream sub-nozzle than for the downstream sub-nozzle. Therefore, according to this configuration, the injection pressure of the upstream sub-nozzle, which is the side where the weft yarn arrives earlier, can be made to rise earlier than the injection pressure of the downstream sub-nozzle during weft insertion, thereby shortening the injection period of the sub-nozzles and thereby reducing the amount of air consumed.

In addition, in the weft insertion device according to the present invention, by forming both branch pipes in a shape that overlaps each other at the end on the main pipe line side, the injection mode of the air injected from each sub-nozzle can be made appropriate according to the pipe line configuration, compared to when both branch pipes are formed so as to be generally separated (independent).

In more detail, it is assumed that the injection behavior, such as the rise in pressure, of the air injected from the sub-nozzle will correspond to the pipeline configuration. However, this is premised on the premise that the flow of air into each of the branch pipelines described above corresponds to the pipeline configuration. However, if both branch pipelines are formed independently, at least in the initial stage when air begins to flow from the main pipeline into the branch pipeline, the flow rate of air flowing into each branch pipeline may not correspond to the pipeline configuration, and the rise in the injection pressure may be delayed, and the injection behavior from the sub-nozzle may not correspond to the pipeline configuration.

On the other hand, if the two branch lines are formed so that they overlap each other at the end on the main line side, the branch lines will communicate with the main line at the common portion formed by the overlap. As a result, air supplied to the main line from the solenoid valve side will first flow into the common portion, and then flow from the common portion that is part of each branch line into each portion downstream of that. Therefore, with this configuration, compared to when the two branch lines are formed independently, the flow rate of air flowing into each branch line in the initial stage will correspond to the line configuration, and the air spray pattern from the sub-nozzle can also be made appropriate for the line configuration.

Furthermore, if both branch pipes are formed in an overlapping manner as described above, and each branch pipe is formed so that the center of the branch pipe inlet is located within the range of the main pipe when viewed in the longitudinal direction of the main pipe, each branch pipe will be in communication with the main pipe at a position closer to the tip wall. This allows air to flow into each branch pipe more smoothly than when the center of the branch pipe inlet is located outside the range of the main pipe. Therefore, with this configuration, the injection pressure of each sub-nozzle can be raised more quickly, further reducing air consumption.

FIG. 1 is a front view of a weft insertion device of an air jet loom according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA of FIG. 1. This is a cross-sectional view taken along line B-B of FIG. FIG. 4 is a front view of FIG. FIG. 5 is a side view of a main pipeline and a branch pipeline in the supply device of FIG. 4 .

The following describes one embodiment (example) of a weft insertion device for an air jet loom (hereinafter simply referred to as a "loom") according to the present invention, with reference to Figures 1 to 5.

The loom 1 is equipped with a reed beating device 3 that drives a reed 5 to swing. In the reed beating device 3, the reed 5 is supported by a rocking shaft 11 via a sley 7 and a sley sword 9. The rocking shaft 11 is supported so as to be swingable by being installed between the loom frames. Incidentally, the loom frame is composed of a pair of side frames 12 (only one of which is shown in the drawing) that are spaced apart in the width direction of the loom 1 (direction parallel to the weft insertion direction), and multiple (generally four) beams that connect both side frames 12. However, of the multiple beams, only the front top stay 13 that is located on the upper end side of the side frame 12 on the winding side of the woven fabric W from the weaving fell is shown in the drawing.

The loom 1 also includes a weft insertion device 2 for inserting a weft thread into the warp shed. The weft insertion device 2 has a main nozzle MN and multiple sub-nozzles SN. The main nozzle MN and multiple sub-nozzles SN are mounted on a sley 7. The multiple sub-nozzles SN are arranged side by side at a predetermined interval in the width direction. During weaving, air is supplied to each sub-nozzle SN for a preset period during the weft insertion period, and air is sprayed from each sub-nozzle SN.

The loom 1 is equipped with an air tank for storing the air supplied to each sub-nozzle SN. In this embodiment, the front top stay 13 described above is used as the air tank. The front top stay 13 has a rectangular columnar appearance and is a hollow column with a space inside. The front top stay (hereinafter also referred to as the "air tank") 13 has a supply hole 13a through which pressure-adjusted air is supplied from a supply source (not shown) via a regulator or the like, and air is supplied to the inside from the supply hole 13a.

In the weft insertion device 2, the sub-nozzles SN are grouped in pairs from the main nozzle MN side, and air is sprayed for each group. Therefore, the weft insertion device 2 is provided with a plurality of supply devices 14 provided for each group of sub-nozzles SN. In this embodiment, each supply device 14 is attached to the side wall of the air tank (front top stay) 13 via a screw member 20.

The supply device 14 is composed of an electromagnetic on-off valve 15 and a distributor 16 that distributes the air supplied from the air tank 13 via the electromagnetic on-off valve 15 to the two sub-nozzles SN, SN. The distributor 16 also has a supply pipe 17 formed to allow air from the air tank 13 to flow toward the electromagnetic on-off valve 15. The supply pipe 17 is formed in the distributor 16 so that one end of the supply pipe 17 communicates with the nozzle hole 13b formed in the air tank 13 when the supply device 14 is attached to the air tank 13. The supply pipe 17 is also formed so that the other end of the supply pipe 17 communicates with the input port of the electromagnetic on-off valve 15.

The distributor 16 has a main line 18, one end of which is connected to the output port of the electromagnetic valve 15 and the other end of which is closed, and two branch lines 19, 19, which are connected to the other end of the main line 18. Therefore, in the supply device 14, air introduced from the air tank 13 to the supply line 17 in the distributor 16 is introduced into the main line 18 and the branch line 19 via the electromagnetic valve 15. Incidentally, in the supply device 14, the electromagnetic valve 15 and the distributor 16 are provided integrally. Also, the main line 18 in the distributor 16 is formed so that its tip wall 18a is a plane parallel to a direction perpendicular to the longitudinal direction of the main line 18.

The supply device 14 is then connected to the two corresponding sub-nozzles SN, SN by tubes 22 that are connected to each branch line 19 via a pipe joint 21. As a result, the air introduced into each branch line 19 is supplied to each sub-nozzle SN via each tube 22.

As described above, the supply device 14 in the weft insertion device 2 is configured to supply the air introduced from the air tank 13 into the distributor 16 to the two sub-nozzles SN, SN by branching it in the branch pipe 19. In the present invention, each branch pipe 19 is formed to communicate with the main pipe 18 in such a way that at least a portion of the tip wall 18a, which is the wall on the other end side of the main pipe 18 that is closed, is open. In addition, this embodiment is an example in which the two branch pipes 19, 19 are formed to overlap each other at the end on the main pipe 18 side. The supply device 14 of this embodiment is described in detail below.

In the supply device 14, the two branch pipes 19, 19 are formed to open into the tip wall 18a of the main pipe 18. As shown in FIG. 3, the two branch pipes 19, 19 are formed to face rearward in the front-to-rear direction of the loom (the rocking shaft 11 side relative to the air tank 13) and to face diagonally upward when viewed in the weft insertion direction. As shown in FIG. 4, the two branch pipes 19, 19 are formed to be inclined to the left and right at the same angle β with respect to the center line of the main pipe 18 when viewed in the front-to-rear direction.

In addition, as shown in FIG. 4, the branch lines 19a and 19b are formed so that they overlap each other at their ends on the main line 18 side. As a result, each branch line 19 communicates with the main line 18 at the common portion formed by the overlapping. In addition, the branch lines 19a and 19b (the common portion) are formed so that they open to the tip wall 18a of the main line 18 as described above, but in this embodiment, they are formed so that they also open to the peripheral wall 18b of the main line 18 in part (the opening spans the tip wall 18a and the peripheral wall 18b). However, most of the opening is on the tip wall 18a side, so that the center of the end (inlet) of each branch line 19 on the main line 18 side is on the tip wall 18a side. In other words, the center of the inlet of each branch line 19 is located within the range of the main line 18 when viewed in the longitudinal direction of the main line 18.

In this embodiment, each branch pipe 19 is formed so that the center line of the first branch pipe 19a (the left branch pipe 19 in FIG. 4), which is a branch pipe connected to the upstream sub-nozzle SN of the two sub-nozzles SN in each group, and the center line of the second branch pipe 19b (the right branch pipe 19 in FIG. 4), which is a branch pipe connected to the downstream sub-nozzle SN, intersect on the center line of the main pipe 18. Furthermore, as shown in FIG. 5, both branch pipes 19a and 19b are formed so that the angle α1 that the center line of the first branch pipe 19a makes with the center line of the main pipe 18 is larger than the angle α2 that the center line of the second branch pipe 19b makes with the center line of the main pipe 18 when viewed in the weft insertion direction.

In the weft insertion device 2 of this embodiment described above, each branch pipe 19 in the supply device 14 (distributor 16) is formed so that most of it opens into the tip wall 18a of the main pipe 18. Therefore, according to the weft insertion device 2 in which the supply device 14 is configured in this way, compared to the conventional configuration in which each branch pipe in the distributor opens only to the peripheral wall of the main pipe, air introduced into the main pipe 18 and reaching the formation position of the branch pipe 19 is more likely to flow directly into each branch pipe 19. As a result, the flow rate of air bouncing off the tip wall 18a of the main pipe 18 is less than in the conventional configuration, so turbulence of the air flow flowing into the branch pipe 19 is suppressed as much as possible.

As a result, the airflow supplied to the sub-nozzle SN through each branch pipe 19 can be made as turbulent as possible, and the impact of turbulence on the weft insertion caused by turbulence in the airflow can be reduced. Furthermore, by reducing turbulence in the airflow in this way, the time it takes for the injection pressure of the sub-nozzle SN to rise to the desired pressure is also reduced, so that the injection period of the sub-nozzle SN can be shortened, and the amount of air consumed can be reduced.

Furthermore, in this embodiment, the angle α1 between the center line of the first branch pipe 19a and the center line of the main pipe 18 is larger than the angle α2 between the center line of the second branch pipe 19b and the center line of the main pipe 18 when viewed in the weft insertion direction. Due to such a pipe configuration of each branch pipe 19, the flow resistance of each branch pipe 19 to the air flowing in is smaller in the first branch pipe 19a than in the second branch pipe 19b. Therefore, the air flows into each branch pipe 19 more smoothly on the first branch pipe 19a side. As a result, the time until the injection pressure rises to the desired pressure is shorter for the upstream sub-nozzle SN than for the downstream sub-nozzle SN. In other words, in weft insertion, the injection pressure of the upstream sub-nozzle SN, which is the side where the weft yarn arrives earlier, rises earlier than the injection pressure of the downstream sub-nozzle SN. Therefore, this configuration makes it possible to shorten the ejection period of each sub-nozzle SN in each group, which in turn reduces the amount of air consumed.

In addition, in this embodiment, the branch pipes 19a, 19b are connected to the main pipe 18 at the common portion formed by overlapping each other at the end on the main pipe 18 side. As a result, air introduced into the main pipe 18 first flows into the common portion, and then flows from the common portion that forms part of each branch pipe 19 to each portion downstream of that. And, with this configuration, compared to when the branch pipes 19, 19 are formed independently, at least in the initial stage when air starts to flow from the main pipe side into the branch pipes, the flow rate of air flowing into each branch pipe 19 is appropriate according to the pipe configuration. As a result, the injection mode of the air injected from the sub-nozzle SN, such as the pressure rise at least in the initial stage, can be made appropriate according to the pipe configuration.

Furthermore, in this embodiment, the branch pipes 19a, 19b are formed in an overlapping manner as described above, and are formed so that the center of the inlet of the branch pipe 19 is located within the range of the main pipe 18 when viewed in the longitudinal direction of the main pipe 18. In other words, each branch pipe 19 is in communication with the main pipe 18 at a position closer to the tip wall 18a. This allows air to flow into each branch pipe 19 more smoothly than when the center of the inlet of the branch pipe 19 is located outside the range of the main pipe 18. Therefore, with this configuration, the injection pressure of each sub-nozzle SN rises more quickly, further reducing air consumption.

The above describes one embodiment of a weft insertion device for a loom to which the present invention is applied (hereinafter referred to as the "embodiment"). However, the present invention is not limited to the configuration described in the embodiment, and can be implemented in other embodiments (variations) such as the following.

(1) Regarding the opening position of the branch pipe relative to the tip wall of the main pipe, in the above embodiment, both of the two branch pipes 19a, 19b are formed so that their openings straddle the tip wall 18a and the peripheral wall 18b. However, in the present invention, the two branch pipes are not limited to being formed in such a shape, and one or both of them may be formed so that they open only on the tip wall.

In the above embodiment, both of the two branch pipes 19a and 19b are formed so that the majority of the openings to the main pipe 18 are on the tip wall 18a side. However, in the present invention, it is sufficient that at least a portion of the two branch pipes open to the tip wall. That is, one or both of the two branch pipes may be formed so that they open more toward the peripheral wall side than the tip wall side. In that case, the center of the inlet of the branch pipe formed so that it opens more toward the peripheral wall side will be located outside the existence range of the main pipe when viewed in the longitudinal direction of the main pipe. Thus, in the present invention, the two branch pipes are not limited to being formed so that the centers of both inlets are located within the existence range of the main pipe 18 as in the above embodiment when viewed in the longitudinal direction of the main pipe, but may be formed so that the center of at least one inlet is located outside the existence range of the main pipe 18.

(2) Regarding the relationship between the two branch pipes, in the above embodiment, the two branch pipes 19a, 19b are formed so as to overlap each other at the end on the main pipe 18 side. However, in the present invention, the two branch pipes are not limited to being formed in this manner, and may be formed independently (separately) from each other, including the opening positions relative to the main pipe.

(3) Regarding the direction in which the two branch pipelines are formed, in the above embodiment, the two branch pipelines 19a and 19b are formed such that, when viewed in the weft insertion direction, the angle α1 between the center line of the first branch pipeline 19a and the center line of the main pipeline 18 is greater than the angle α2 between the center line of the second branch pipeline 19b and the center line of the main pipeline 18. However, in the present invention, the two branch pipelines may be formed to form the same angle with the center line of the main pipeline when viewed in the weft insertion direction.

In the above embodiment, the branch pipes 19a, 19b are formed so as to be inclined to the left and right at the same angle β with respect to the center line of the main pipe 18 when viewed in the front-to-rear direction of the loom. However, in the present invention, the two branch pipes may be formed so as to be inclined to the left and right at different angles with respect to the center line of the main pipe when viewed in the front-to-rear direction.

Furthermore, in the above embodiment, each branch pipeline 19 is formed so that the center lines of the two branch pipelines 19a, 19b intersect. The two branch pipelines 19a, 19b are also formed so that both center lines intersect with the center line of the main pipeline 18, and the position where the center lines of the two branch pipelines 19a, 19b intersect is on the center line of the main pipeline 18. However, in the present invention, the two branch pipelines are not limited to being formed in this way.

For example, even if the center lines of both branch pipelines are formed to intersect, the intersection may be formed at a position other than the center line of the main pipeline. Also, the center lines of both branch pipelines may be formed to intersect, and only the center line of one of the branch pipelines may intersect with the center line of the main pipeline. Furthermore, the center lines of both branch pipelines may be formed so that they do not intersect, and in that case, one or both center lines may be formed so that they intersect with the center line of the main pipeline, or both center lines may be formed so that they do not intersect with the center line of the main pipeline.

(4) Regarding the method of installing the supply device, in the above embodiment, the supply device 14 is installed in a manner that it is directly attached to the side wall of the front top stay 13. However, in the present invention, the supply device is not limited to being directly attached to the front top stay in this manner.

For example, the supply device may be installed by using a support member such as a bracket and attaching it to the front top stay via the support member. In that case, the nozzle hole of the front top stay and the supply pipe in the distributor of the supply device are connected via a pipe joint, tube, etc.

When the supply device is provided using such a support member, the degree of freedom in the arrangement and orientation of the supply device in the front-to-rear direction is increased compared to the above-mentioned embodiment. Therefore, in this case, instead of providing the supply device with the branch pipe 19 facing backward as in the above-mentioned embodiment, it is also possible to provide the supply device with the branch pipe facing forward when viewed in the weft insertion direction.

Furthermore, in the above embodiment, the supply device 14 is configured with the distributor 16 so that the branch pipe 19 is directed diagonally upward (the branch pipe 19 is formed in the distributor 16) in consideration of the installation state such as the installation position and installation state. However, when the supply device is installed using a support member as described above, the branch pipe may be configured so that the branch pipe is directed horizontally (front-to-back direction) or diagonally downward in the above installation state. In other words, the direction of the branch pipe in the supply device in the above installation state may include the front-to-back direction, and may be horizontal or diagonally downward, not limited to diagonally upward as in the above embodiment. Furthermore, with regard to the direction of diagonally upward, horizontal, and diagonally downward, the supply device (distributor) is not limited to being configured so that both branch pipes are directed in the same direction, and one branch pipe and the other branch pipe may be configured to be directed in different directions.

(5) Regarding the main conduit, in the above embodiment, the main conduit 18 is formed so that its tip wall 18a is a plane parallel to a direction perpendicular to the longitudinal direction of the main conduit 18. However, in the present invention, the main conduit is not limited to being formed so that its tip wall forms such a plane. For example, the main conduit may be formed so that its tip portion forms a cone shape, in which case the tip wall of the main conduit is formed so as to be inclined with respect to the longitudinal direction of the main conduit.

(6) In addition, in the present invention, the pipelines (main pipeline and branch pipelines) in the distributor may be formed so that their cross-sectional shape is circular, elliptical, or polygonal.

The present invention is not limited to the above examples, and can be modified as appropriate without departing from the spirit of the invention.

REFERENCE SIGNS LIST 1 loom 2 weft insertion device MN main nozzle SN sub nozzle 3 beating device 5 reed 7 sley 9 sley sword 11 rocking shaft 12 side frame 13 front top stay (air tank)
Reference Signs List 13a Supply hole 13b Spout hole 14 Supply device 15 Electromagnetic on-off valve 16 Distributor 17 Supply pipe 18 Main pipe 18a Tip wall 18b Circumferential wall 19a Branch pipe (first branch pipe)
19b Branch pipe (second branch pipe)
21 Pipe joint 22 Tube

Claims (4)

A weft insertion device for an air jet loom comprising a plurality of supply devices each including an electromagnetic valve and a distributor for distributing air supplied from a supply source via the electromagnetic valve to two sub-nozzles, the distributor including a main duct having one end connected to the electromagnetic valve and the other end closed by a tip wall, and a pair of branch ducts connected to the other end of the main duct and connected to corresponding sub-nozzles, the branch ducts being oriented in the front-rear direction of the loom,
A weft insertion device, wherein each of the branch ducts is connected to the main duct in such a manner that at least a portion of the branch duct opens to the tip wall. 2. The weft insertion device according to claim 1, wherein each of the branch pipes is formed such that, as viewed in the weft insertion direction, an angle formed by a center line of the branch pipe connected to the upstream sub-nozzle with respect to a center line of the main pipe is larger than an angle formed by a center line of the branch pipe connected to the downstream sub-nozzle with respect to the center line of the main pipe. 3. The weft insertion device according to claim 1, wherein the branch pipes are formed so as to overlap each other at their ends on the main pipe side. 4. The weft insertion device according to claim 3, wherein each of the branch pipes is formed such that a center of an inlet of the branch pipe is located within an area in which the main pipe exists, as viewed in the longitudinal direction of the main pipe.

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