JP2016044090A - Glass traction apparatus, glass molding apparatus and glass molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of a trouble in a shape, when molding tubular or columnar glass continuously.SOLUTION: A tube traction apparatus 5 includes: traction means 14 for pulling tubular glass Gt molded continuously by allowing molten glass to flow down along the outer surface of a rotating molding, along an axial direction of the tubular glass Gt on the downstream side of the tubular glass Gt; and rotating driving means 15 for rotating the traction means 14 around the axis of the tubular glass Gt.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a glass pulling device that pulls continuously formed tubular or columnar glass on the downstream side thereof, a glass forming device including the glass pulling device, and a glass forming method for forming tubular or columnar glass. .

  Usually, when tubular or cylindrical glass is continuously formed, a device that pulls the continuously formed tubular or cylindrical glass along the direction of the axis on the downstream side is used. .

  For example, Patent Document 1 discloses a glass pulling device used when forming tubular glass. This glass pulling device is composed of a pair of conveyor belts that sandwich a continuously formed tubular glass and pull it in the lateral direction.

Japanese Utility Model Publication No. 6-54742

  However, when a tubular or columnar glass is continuously formed using such a glass traction device, there may be a problem in the shape due to, for example, the influence of vibration during molding. Such a problem may occur not only when the tubular or cylindrical glass is pulled in the lateral direction but also when the tubular or cylindrical glass is pulled downward.

  This invention makes it a technical subject to suppress that the malfunction of a shape arises, when shape | molding tubular or columnar glass continuously in view of the said situation.

  The glass pulling device according to the present invention, which has been created to solve the above-mentioned problems, is a tube or columnar glass formed continuously, pulling the axial line while pulling along the direction of the axis on the downstream side. It is characterized by having traction rotation means for rotating around.

  With this configuration, a predetermined rotational force is applied to the tubular or columnar glass around its axis. Thereby, rigidity is structurally improved by slightly twisting the glass being solidified. For this reason, even if it receives a vibration etc., since the shape of glass is easy to be maintained and it is suppressed that the shape of glass is distorted, it can suppress that a malfunction arises in the shape of tubular or columnar glass. Thus, according to the glass pulling device of the present invention, it is possible to suppress the occurrence of a shape defect when continuously forming a tubular or columnar glass.

  In the above configuration, the traction rotation means is constituted by traction means for traction of the tubular or columnar glass along the direction of the axis, and rotation drive means for rotating the traction means around the axis. It is preferable.

  With this configuration, the traction rotating means can be easily configured, and the traction conditions and the like can be easily set.

  Said structure WHEREIN: It is preferable that the said tow | pulling means was comprised by the fixed position of the direction of the said axis line by a pair of rotating member which pulls by pinching and rotating the said tubular or columnar glass.

  For example, in the case of a pulling means such as a chuck that grips and pulls the downstream end of the glass, it is necessary to reciprocate the pulling means between a pulling start position and an end position. On the other hand, with the above configuration, the glass is pulled at a fixed position in the axial direction, so that the reciprocating movement of the pulling means can be made unnecessary.

  Said structure WHEREIN: It is preferable that the said rotation member was comprised with the belt which carries out the contact contact holding | maintenance of the said tubular or columnar glass over predetermined length.

  If it is this structure, since glass will be continuously contacted over predetermined length, the contact area of the rotation member with respect to glass will become large, and it will be suppressed that a contact pressure is applied to glass locally. Thereby, it can suppress that the contact to the glass of a rotating member has a bad influence on the shape of glass.

  Further, a glass forming apparatus according to the present invention created to solve the above problems includes a forming means for continuously forming tubular glass, and a downstream side of the tubular glass continuously formed by the forming means. Any of the above glass traction devices that are pulled by the molding means, wherein the molding means comprises a rotating molded body, and the molded body continuously flows the tubular glass by flowing molten glass along its outer surface. Characterized by molding into.

  If it is this structure, the tubular glass pulled by the pulling apparatus of one of the said structures will be rotated with rotation of a molded object. On the other hand, if it is the above-mentioned composition, since the traction means rotates, it is possible to apply an appropriate rotational force to the tubular glass by adjusting the rotation direction and the rotation speed of the traction means. Thereby, it becomes possible to suppress the occurrence of problems in the shape of the tubular glass.

  Said structure WHEREIN: It is preferable that the rotation center of the said molded object is an up-down direction, and the rotation center of the said traction means is located on the same straight line with respect to the rotation center of the said molded object.

  If it is this structure, since it suppresses that a tubular glass will bend between a molded object and a pulling means, it will be suppressed that the complicated force by bending is applied to a tubular glass. Thereby, it can suppress that a malfunction arises in the shape of tubular glass.

  In any one of the configurations described above, it is preferable that the rotation driving unit rotates the traction unit in the same direction as the rotation direction of the molded body.

  If it is this structure, since a traction means rotates in the same direction as a molded object, it is possible to give a suitable rotational force to tubular glass by adjusting a rotational speed. Thereby, it becomes possible to suppress the occurrence of problems in the shape of the tubular glass.

  Said structure WHEREIN: It is preferable that the said rotational drive means rotates the said traction means at a speed faster than the rotational speed of the said molded object.

  If it is this structure, since the rotational speed of a traction means becomes quicker than the rotational speed of a molded object, it is possible to provide an appropriate rotational force to tubular glass. Thereby, it becomes possible to suppress the occurrence of problems in the shape of the tubular glass.

  In addition, the glass forming method according to the present invention, which was created to solve the above-mentioned problems, is a method of pulling a continuously formed tubular or columnar glass along the direction of its axis on the downstream side. Characterized by rotating around an axis.

  If it is this structure, the effect substantially the same as the glass pulling apparatus of the beginning can be acquired.

  As described above, according to the present invention, when a tubular or columnar glass is continuously formed, it is possible to suppress the occurrence of a shape defect.

It is a schematic front view which shows the glass forming apparatus which concerns on embodiment of this invention. (A) is a longitudinal cross-sectional view of a molding furnace, (B) is a cross-sectional view of a molding furnace. It is a longitudinal cross-sectional view of a molded object. It is a longitudinal cross-sectional view which shows the modification of a molded object. It is a top view of a molded object. (A) is a front view around the supply port of the supply pipe, and (B) is a side view around the supply port of the supply pipe. (A) is a front view of a pipe drawing apparatus, (B) is a side view of a pipe drawing apparatus.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic front view showing a glass forming apparatus according to an embodiment of the present invention. The glass forming apparatus 1 forms a tubular glass Gt used for, for example, a fluorescent lamp. In the present embodiment, the tubular glass Gt to be molded has, for example, a diameter of 15 to 150 mm and a glass thickness of 1.0 mm to 3.0 mm.

  The glass forming apparatus 1 includes a melting tank 2, a supply pipe 3, a forming furnace 4, and a pipe drawing apparatus 5 as main components. The melting tank 2 generates and stores molten glass Gm. The supply pipe 3 supplies the molten glass Gm from the melting tank 2 into the molding furnace 4. The molding furnace 4 has a molded body 6 that rotates around an axis in the vertical direction while being supplied with the molten glass Gm from the supply pipe 3. Here, in the present embodiment, the axis of the molded body 6 is the vertical direction, and the term “vertical direction” includes a direction in which an inclination angle with respect to the vertical direction is ± 5 °.

  And the molded object 6 is a shaping | molding means which shape | molds the tubular glass Gt continuously, and the molded object 6 flows down the molten glass Gm along the outer surface, and shape | molds the tubular glass Gt continuously. The molded body 6 is rotationally driven by a driving device (not shown). The tube drawing device 5 draws the molten glass Gm flowing down from the rotating molded body 6 downward. That is, the tube drawing device 5 is a glass pulling device that pulls the tubular glass Gt on the downstream side thereof.

  Further, the glass forming apparatus 1 includes first heating means 7 for heating the supply pipe 3. The supply pipe 3 includes a longitudinal portion 3a extending downward from the dissolution tank 2, a lateral portion 3b extending laterally from a bent portion at the lower end of the longitudinal portion 3a, and a throttle portion at the tip of the lateral portion 3b. And a small diameter portion 3c extending in the lateral direction to the vicinity of the molded body 6. The horizontal part 3b has the same diameter as the vertical part 3a, and the small diameter part 3c has a smaller diameter than the horizontal part 3b.

  In the present embodiment, the supply pipe 3 is made of a conductive metal such as platinum, and the first heating means 7 is an electrode connected to the lateral portion 3 b of the supply pipe 3. The horizontal portion 3b is heated by energization. By adjusting the heating of the lateral part 3b of the supply pipe 3 by the first heating means 7, the temperature of the molten glass Gm flowing in the lateral part 3b of the supply pipe 3 is adjusted, and thereby the molten glass Gm Adjust the viscosity.

  Of course, the 1st heating means 7 is not limited to this, For example, the heater etc. which were arrange | positioned around the supply pipe | tube 3 may be sufficient. Moreover, the heating location by the 1st heating means 7 is not limited to the horizontal direction part 3b, The vertical direction part 3a and the small diameter part 3c may be sufficient.

  Although the temperature of the molten glass Gm supplied to the molded object 6 from the supply pipe 3 is based also on the composition of the molten glass Gm, it is 1000 to 1300 degreeC, for example. If it is lower than 1000 ° C., the viscosity is too high and the molten glass Gm may not flow smoothly. When it exceeds 1300 degreeC, a viscosity is too low and sufficient thickness for molten glass Gm may not be obtained.

The viscosity of the molten glass Gm supplied from the supply pipe 3 to the molded body 6 is, for example, 10 ³ P to 10 ⁴ P. If it is less than 10 ³ P, the viscosity may be too low to obtain a sufficient thickness for the molten glass Gm. If it exceeds 10 ⁴ P, the viscosity is too high and the molten glass Gm may not flow smoothly.

  Further, the glass forming apparatus 1 has a second heating means 8 for heating the inside of the forming furnace 4. The 2nd heating means 8 is arrange | positioned at the outer peripheral side of the molded object 6, and heats the molten glass Gm which flows down the molded object 6 by heating the inside of the shaping | molding furnace 4. FIG. By adjusting the heating in the molding furnace 4 by the second heating means 8, the temperature of the molten glass Gm flowing down the molded body 6 is adjusted, and thereby the viscosity of the molten glass Gm is adjusted.

  As shown in FIG. 2, in this embodiment, the 2nd heating means 8 is comprised by the soaking plate 8a (refractory material) and the heater 8b which heats the soaking plate 8a from the outer peripheral side. The soaking plate 8 a constitutes the peripheral wall of the molding furnace 4. A plurality of soaking plates 8 a are arranged along the circumferential direction of the molded body 6, and are configured to have the same temperature in the circumferential direction of the molded body 6.

  As shown in FIG. 3, the molded body 6 includes a sleeve portion 9 and a metal chip 10 that supports the sleeve portion 9 from the lower side as main components. The sleeve portion 9 is made of, for example, a refractory material, and includes a main body portion 9a and a shaft portion 9b extending upward from the upper end of the main body portion 9a. The sleeve portion 9 has a hole extending in the axial direction inside, and a metal tube 11 such as platinum is disposed in the hole. The upper end of the metal tube 11 is connected to an air compressor (not shown). A metal tip 10 is connected to the lower end of the metal tube 11. The metal chip 10 is made of a metal such as platinum. A through hole 10 a is formed in the metal chip 10 along the axial direction, and the through hole 10 a communicates with the inside of the metal tube 11.

  The shaft portion 9b of the sleeve portion 9 and the metal tube 11 in the sleeve portion 9 are provided with a rotational driving force from a driving device (not shown) above, whereby the sleeve portion 9 and the metal tip 10 are synchronized with each other. Rotate. In the present embodiment, the molded body 6 rotates clockwise in plan view.

  As shown in FIG. 3, the molded body 6 has an upper surface 12 that receives the molten glass Gm supplied from the small-diameter portion 3 c of the supply pipe 3 during rotation on the upper side of the main body portion 9 a of the sleeve portion 9. The upper surface 12 has an outer peripheral edge 12a that allows the received molten glass Gm to flow down. And the molded object 6 has the cylindrical side surface 13 comprised by the main-body part 9a of the sleeve part 9, and the outer peripheral surface of the metal chip 10. FIG. On the side surface 13, the molten glass Gm that has flowed down from the outer peripheral edge 12 a during the rotation flows down. In the present embodiment, the upper surface 12 and the side surface 13 of the molded body 6 have a perfect circular shape regardless of the axial position of the contour line of the cross section.

  The upper surface 12 has a shape that gradually increases as it moves from the outer peripheral edge 12a to the inner peripheral side, and is a tapered surface in this embodiment. The inclination angle of the upper surface 12 with respect to the horizontal plane is, for example, 10 ° to 20 °. When the inclination angle of the upper surface 12 is less than 10 °, the speed at which the molten glass Gm flows down from the outer peripheral edge 12a becomes slow, and the molten glass Gm may devitrify on the upper surface 12. When the inclination angle of the upper surface 12 exceeds 20 °, the speed at which the molten glass Gm flows down from the outer peripheral edge 12a increases, and the molten glass Gm may not be connected in the circumferential direction on the upper surface 12.

  In the present embodiment, the side surface 13 includes an upper uniform diameter portion 13a connected to the outer peripheral edge 12a, a throttle portion 13b connected to the lower end of the upper uniform diameter portion 13a, and a lower uniform diameter portion connected to the lower end of the throttle portion 13b. 13c. The upper and lower uniform diameter portions 13a and 13c are portions having a uniform diameter in the axial direction. The lower uniform diameter portion 13c is smaller in diameter than the upper uniform diameter portion 13a and has a very short length in the axial direction. The narrowed portion 13b is a portion that gradually decreases in diameter downward, and is a tapered surface in the present embodiment. In the present embodiment, the narrowed portion 13 b and the lower uniform diameter portion 13 c are configured by the outer peripheral surface of the metal chip 10. In the present embodiment, the inclination angle of the narrowed portion 13b with respect to the horizontal plane is larger than the inclination angle of the upper surface 12 with respect to the horizontal plane.

  Of course, the shape of the molded body 6 is not limited to the shape described in FIG. For example, the upper uniform diameter portion 13a of the side surface 13 may be gradually reduced in diameter in the middle in the axial direction. That is, a plurality of apertures may be provided on the side surface 13. Furthermore, for example, as shown in FIG. 4A, the molded body 6 may be configured such that the side surface 13 does not have a narrowed portion, and the side surface 13 is composed only of a uniform diameter portion. Moreover, as shown to FIG. 4 (B), the molded object 6 may be provided with the cyclic | annular recessed part 12b in the upper surface 12, and you may make it the molten glass Gm accumulate in the recessed part 12b. Furthermore, as shown in FIG. 4C, the molded body 6 may be provided with an annular convex portion 13d on the side surface 13 thereof. Furthermore, the molded body 6 may not have the side surface 13 as shown in FIG.

  In addition, the rotational speed of the molded object 6 is 3 rpm-15 rpm, for example. When the rotational speed of the molded body 6 is less than 3 rpm, since the molten glass Gm flows down to the side surface 13 before spreading on the upper surface 12, a spiral thickness distribution may occur on the side surface 13. If it exceeds 15 rpm, the molten glass Gm may not flow smoothly from the upper surface 12 to the side surface 13 due to centrifugal force.

  Next, the small diameter part 3c of the supply pipe 3 of this embodiment is demonstrated with reference to FIG. 5, FIG. In FIGS. 3 and 4, the small diameter portion 3 c of the supply pipe 3 is schematically illustrated.

  As shown in FIG. 5, the small diameter portion 3 c of the supply pipe 3 has a supply port 3 d located above the upper surface 12. And in this embodiment, the small diameter part 3c of the supply pipe 3 extended from the dissolution tank 2 side bends in the rotation direction downstream side of the molded body 6 above the upper surface 12 in a plan view, and the supply port 3d at its tip Have That is, the supply port 3d is opened downstream in the rotation direction of the molded body 6. Depending on the opening direction of the supply port 3d, the supply pipe 3 supplies the molten glass Gm from the supply port 3d toward the upper surface 12 on the downstream side in the rotation direction, as indicated by a white arrow A.

  The small-diameter portion 3c of the supply pipe 3 has a uniform diameter and has a round (circular) shape in cross section as shown in FIG. As shown in FIG. 6B, the supply port 3d has a shape obtained by obliquely cutting the supply pipe 3 into a straight line so that the lower side protrudes in a side view.

  As shown in FIG. 7, the tube drawing device 5 pulls the tubular glass Gt continuously formed by the forming furnace 4 along the direction of the axis J of the tubular glass Gt on the downstream side of the tubular glass Gt. Means 14 and rotational driving means 15 for rotating the pulling means 14 around the axis J of the tubular glass Gt. The pulling means 14 and the rotation driving means 15 are configured to pull the continuously formed tubular glass Gt along the axis J of the tubular glass Gt while pulling the tubular glass Gt on the downstream side of the tubular glass Gt. It is a traction rotation means for rotating around.

  In the present embodiment, the traction means 14 is composed of a pair of rotating members that rotate while holding the tubular glass Gt at a fixed position in the axis J direction of the tubular glass Gt. The belt 14a is continuously contacted and held over its length. Of course, the rotating member is not limited to this, and for example, a plurality of pairs of rollers that rotate while sandwiching the tubular glass Gt may be disposed along the axis J direction of the tubular glass Gt.

  In the present embodiment, each belt 14a is an endless ring and is stretched between a pair of large-diameter pulleys 14b arranged in the vertical direction and a pair of small-diameter pulleys 14c arranged between the pair of large-diameter pulleys 14b. Yes. The belt 14a contacts the tubular glass Gt with a predetermined contact pressure by the small-diameter pulley 14c. The large-diameter and small-diameter pulleys 14b and 14c are rotatably attached to the attachment plate 14d. The attachment plate 14d is fixed to the turntable 14e. The pulley driving means 14f rotates the large diameter pulley 14b, and this rotation is transmitted to the small diameter pulley 14c via the belt 14a, and the small diameter pulley 14c rotates. The pulley driving means 14f is also fixed to the rotary table 14e.

  The turntable 14e is rotatably supported via a rotation support member (not shown). Then, the rotary table 14e is rotationally driven by the rotational driving means 15, whereby the belt 14a rotates (turns) around the axis J of the tubular glass Gt.

  The turning center line of the belt 14 a is located on the same straight line as the rotation center line of the molded body 6. Here, the term “located on the same straight line” includes a state in which the inclination angle of the center line of rotation of the belt 14 a with respect to the center line of rotation of the molded body 6 is ± 5 °.

  In the present embodiment, the rotation driving unit 15 rotates (turns) the belt 14 a in the same direction as the rotation direction of the molded body 6. That is, the belt 14a turns clockwise in plan view. Then, the rotation driving means 15 turns the belt 14 a at a speed faster than the rotation speed of the molded body 6. The turning speed of the belt 14a is, for example, 3 rpm to 20 rpm.

  Next, a method for forming the tubular glass Gt by the glass forming apparatus 1 will be described with reference to FIGS.

  In advance, the glass raw material is melted in the melting tank 2 to generate and store molten glass Gm. Then, the supply pipe 3 is heated to a predetermined temperature by the first heating means 7. Further, the inside of the molding furnace 4 is heated to a predetermined temperature by the second heating means. Then, the air compressor is activated to supply air into the metal pipe 11. The air supplied into the metal tube 11 is ejected downward from the lower end of the metal chip 10 through the through hole 10a. Further, the tube drawing device 5 is activated, and the belt 14a is rotated by the rotation driving means 15 while being rotated by the pulley driving means 14f.

  Next, the molded body 6 is rotated around the vertical axis by a drive device (not shown). Then, the molten glass Gm is supplied from the melting tank 2 to the supply pipe 3, and the molten glass Gm is supplied from the supply port 3 d of the supply pipe 3 to the upper surface 12 of the molded body 6. Then, the molten glass Gm is received by the upper surface 12 of the molded body 6 and flows down from the outer peripheral edge 12 a of the upper surface 12. Then, the molten glass Gm flows down the side surface 13 of the molded body 6. The thickness of the molten glass Gm at the lower end of the lower uniform diameter portion 13 c of the side surface 13 is thicker than the thickness of the molten glass Gm on the upper surface 12.

  And the molten glass Gm which flowed down from the lower end of the side surface 13 of the molded body 6 becomes tubular, and becomes a molten tubular glass Gt. At this time, the molten glass Gm is stably formed into a tubular shape by the air ejected from the lower end of the metal chip 10 of the molded body 6. While this molten tubular glass Gt is gradually solidified, on the downstream side thereof, it is pulled downward along the direction of the axis J by the belt 14a of the tube drawing device 5, and at the same time, Rotated around. Thereby, the formation of the tubular glass Gt is completed.

  When the forming of the tubular glass Gt having a predetermined length is completed, the tubular glass Gt is cut. This cutting method is not particularly limited. For example, a cutout may be formed with a cutter or the like, and the cut may be cut. Thereafter, molding and cutting of the tubular glass Gt are repeated. When a desired amount of tubular glass Gt is obtained, the supply of the molten glass Gm to the molded body 6 is stopped, and the rotation of the molded body 6 and the tube drawing device 5 are stopped. Then, the air compressor and the first and second heating means 7 and 8 are also stopped.

  In the tube drawing device 5 of the glass forming apparatus 1 configured as described above, a predetermined rotational force is applied around the axis J to the tubular glass Gt. Thereby, rigidity is structurally improved by applying an appropriate twisting force to the glass being solidified. For this reason, even if it receives a vibration etc., since the shape of glass is easy to be maintained and it is suppressed that the shape of glass is distorted, it can suppress that a malfunction arises in the shape of tubular glass Gt. Thus, according to the tube drawing device 5 of the present embodiment, it is possible to suppress the occurrence of a shape defect when the tubular glass Gt is continuously formed.

  In the above embodiment, the tubular glass Gt is formed from the molten glass by the molded body 6 and pulled by the belt 14a. However, the present invention is not limited to this. For example, cylindrical glass may be formed by the redraw method and pulled by the tube drawing device 5.

  Further, in the above embodiment, the traction rotating means for rotating the continuously formed tubular or columnar glass around the axis while pulling along the direction of the axis on the downstream side thereof is the traction means 14. However, the present invention is not limited to this. For example, the pulling and rotating means is composed of a pair of rotating members that pull by rotating the glass while sandwiching the glass at a fixed position in the axial direction of the tubular or cylindrical glass, and in a direction perpendicular to the axial direction. On the other hand, the rotation center lines of the pair of rotating members may be inclined to opposite sides. Further, for example, the pulling rotation means is a gripping means such as a chuck for gripping an end portion of the tubular or columnar glass, and the gripping means pulls the glass along the direction of the axis around the axis. You may perform the operation | movement to rotate.

DESCRIPTION OF SYMBOLS 1 Glass forming apparatus 2 Melting tank 3 Supply pipe 4 Molding furnace 5 Pipe drawing apparatus (glass pulling apparatus)
6 Molded body 14 Pulling means 14a Belt (rotating member)
15 Rotation drive means Gm Molten glass Gt Tubular glass J Axis

Claims (9)

  A glass traction device comprising traction rotation means for rotating a continuously formed tubular or columnar glass around the axis while pulling along the direction of the axis on the downstream side.   The pulling and rotating means is constituted by pulling means for pulling the tubular or columnar glass along the direction of the axis, and rotation driving means for rotating the pulling means around the axis. The glass traction device according to claim 1.   3. The glass according to claim 2, wherein the pulling means includes a pair of rotating members that pull by pulling the tubular or columnar glass at a fixed position in the direction of the axis. Traction device.   4. The glass traction device according to claim 3, wherein the rotating member is constituted by a belt that continuously contacts and holds the tubular or columnar glass over a predetermined length. The glass traction device according to any one of claims 1 to 4, wherein the glass glass traction device according to any one of claims 1 to 4 is configured to pull the tubular glass continuously formed by the forming device at a downstream side thereof. Prepared,
The said shaping | molding means is comprised with the molded object to rotate, and the said molded object flows down molten glass along the outer surface, and forms the said tubular glass continuously, The glass forming apparatus characterized by the above-mentioned.   6. The glass forming apparatus according to claim 5, wherein the rotation center of the molded body is in the vertical direction, and the rotation center of the traction means is located on the same straight line with respect to the rotation center of the molded body. .   The glass forming apparatus according to claim 5 or 6, wherein the rotation driving means rotates the pulling means in the same direction as a rotation direction of the molded body.   The glass forming apparatus according to claim 7, wherein the rotation driving unit rotates the pulling unit at a speed faster than a rotation speed of the molded body.   A glass forming method characterized by rotating a continuously formed tubular or columnar glass around the axis while pulling along the direction of the axis on the downstream side.

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