1. Field of the Invention
The present invention relates to an apparatus for producing glass particles deposit by depositing glass particles on an outer circumferential face of a target rod while relatively moving the target rod with respect to a glass particle synthesis burner in a reaction vessel. More particularly, the present invention relates to an apparatus for producing glass particles deposit in which the glass particles having not been deposited on the outer circumferential face of the target rod but floating within the reaction vessel can be exhausted out of the reaction vessel efficiently.
2. Description of the Prior Art
A method for producing a glass particles deposit 5 by depositing glass particles on an outer circumferential face of a target rod I using this producing apparatus will be described below.
Within a reaction vessel 4, glass particles (referred to as the “soot”) are blown onto the outer circumferential face of the target rod 1 by burners 2 (this process is referred to as “soot deposition”). The target rod 1 is rotated around its central axis together with a supporting rod 3 by a rotation mechanism 7, so that the glass particles are deposited onto the entire circumference of the target rod 1. When the target rod 1 is movable up and down by means of a lift 8, the glass particles can be deposited over the entire length of the target rod 1. Since the lift 8 and the rotation mechanism 7 are operated continuously, the target rod 1 is moved in an upward or downward direction while being rotated, so that the glass particles are deposited onto the outer circumferential face of the target rod 1. Thus, the glass particles deposit 5 (referred to as “soot body”) is produced. Gas such as clean air is blown out of a gas port 18 during producing the glass particles deposit 5. The blown gas is passed around the glass particles deposit to be produced, and then flowed in a direction toward an exhaust port 17.
In producing the glass particles deposit using this producing apparatus, glass particles having not been deposited on the outer circumferential face of the target rod or the glass particles deposit are adhered within the reaction vessel. Since the reaction vessel is at high temperatures, an upward current occurs. Glass particles are blown in this upward current to flow to an upper part of the reaction vessel, and adhered on the upper part of the reaction vessel. In producing the glass particles deposit for a long time, a number of glass particles are adhered on the reaction vessel and peeled off in lump from the reaction vessel. An eddy occurs partially due to a flow of the fluid within the reaction vessel, so that glass particles that have once flowed to the exhaust port side can not be exhausted smoothly and remain within the reaction vessel. The peeled off lump of glass particles or the glass particles remaining within the reaction vessel are deposited on the glass particles deposit. Thereby, a portion where the lump or the glass particles were deposited excessively has a larger diameter than the other portions, whereby the outer shape of the produced glass particles deposit is irregular. When this glass particles deposit is vitrified to obtain a preform, the preform has irregularities or air bubbles which correspond to irregularities of the glass particles deposit.
U.S. Pat. No. 5,116,400 disclosed that while a burner array having a plurality of burners arranged in parallel to a target rod is moved with respect to the target rod, glass particles blown out of the burners are deposited on the target rod to produce the glass particles deposit. In order to form a uniform glass particles deposit, an air flow in the area between the burner array and the glass particles deposit is controlled to be relatively uniform over the entire length of the glass particles deposit, and substantially perpendicular to a central axis of the glass particles deposit.
In the invention of the above patent, air ports for causing the air flow are placed on both the outsides of the burners. The air flow from the air ports is blown toward the glass particles deposit. However, the air blown against the glass particles deposit is diffused over many directions, and is not flowed smoothly to an exhaust port. The diffused air may form an eddy. Owing to this eddy of the air flow, glass particles not deposited on the glass particles deposit are not exhausted rapidly. However, in the above patent, there is no consideration for this producing apparatus that glass particles are adhered on an inner face of the reaction vessel.
It is an object of the present invention to provide an apparatus for producing glass particles deposit that can control a flow of fluid within the reaction vessel, and exhaust rapidly floating dusts such as glass particles that have not been deposited.
In the apparatus for producing glass particles deposit according to this invention, a target rod is held within a reaction vessel by a holding means. A plurality of glass particle synthesis burners are placed on a front face of the reaction vessel and directed toward an outer circumferential face of the target rod. The target rod or the burners can be relatively moved in parallel to a rotation axis of the target rod, glass particles synthesized by the burners are deposited one layer after another on the outer circumferential face of the target rod that is being rotated. At least one exhaust port is provided on a rear face of the reaction vessel. A fluid adjusting means has two wall faces extending from both sides of the exhaust port and being in contact with two side faces other than the front face and the rear face of the reaction vessel, with its contained angle of 90 degrees or less. Assuming that a shorter distance between a first shortest distance from the rotation axis of the target rod to the side face of the reaction vessel and a second shortest distance from the rotation axis of the target rod to the wall face is L, and an outer diameter of the glass particles deposit deposited on the target rod is d, L is greater than d. A plurality of first gas ports are provided at positions symmetrical with respect to a plane containing central axes of the burners and the rotation axis of the target rod, the positions being closer to the front face side of the reaction vessel than positions at which the side faces of the reaction vessel are contact with the wall faces. The first gas ports are directed toward the wall face on the same side.
In the apparatus for producing glass particles deposit, it is desirable that the plurality of exhaust ports are provided and a displacement adjusting unit for adjusting displacement through each exhaust port is provided.
Further, in the apparatus for producing glass particles deposit, it is desirable that a second gas port for blowing a gas flow is provided above the holding means of the target rod within the reaction vessel and in parallel to an upper face of the reaction vessel.
Moreover, in the apparatus for producing glass particles deposit, it is desirable that at least one of the exhaust ports is installed above positions where the glass particle synthesis burners are disposed.
Further, in the apparatus for producing glass particles deposit, it is desirable that the upper face of the reaction vessel is formed with an inclined face increasing in height at a constant rate from the front face of the reaction vessel to the rear face of the reaction vessel, and at least one of the exhaust ports is provided on an upper end portion of the rear face of the reaction vessel.
Moreover, in the apparatus for producing glass particles deposit, it is desirable that a gas heating unit for heating the gas to be supplied to the gas port is provided.
The present invention will be described below in more detail with reference to the drawings. In FIGS. 1 to 3, the same parts are designated by the same numerals as in
An apparatus for producing glass particles deposit according to a first embodiment of the present invention comprises glass particle synthesis burners 2, a supporting rod 3, a reaction vessel 4, a holding means 6, a rotation mechanism 7, a lift 8, and exhaust ports 10 and 11, and is employed to deposit glass particles on an outer circumferential face of a target rod 1. The reaction vessel 4 has a rectangular section. Within the reaction vessel 4, the target rod 1 is held by the holding means 6 connected with one end portion of the supporting rod 3. The supporting rod 3 extends outside the reaction vessel 4. The other end portion of the supporting rod 3 is connected with the rotation mechanism 7. The rotation mechanism 7 is also connected with the lift 8 for lifting the target rod 1. The plurality of glass particle synthesis burners 2 are arranged at a regular interval toward the target rod 1 on one side face 18 (hereinafter referred to as the front face) of the reaction vessel 4. The plurality of exhaust ports 10 and 11 are provided on the other side face 15 (hereinafter referred to as a rear face) opposite the front face 18 of the reaction vessel 4, and opposed to the burners 2, with the target rod 1 placed therebetween. The target rod 1 is rotated around its central axis by the rotation mechanism 7 together with the supporting rod 3. With the continuous operation of the lift 8 and the rotation mechanism 7, the target rod 1 is moved up or down while being rotated, so that glass particles are deposited on the outer circumferential face of the target rod 1.
The apparatus of the invention has a fluid adjusting means 16 for adjusting a flow of fluid within the reaction vessel 4. The fluid adjusting means 16 is provided almost vertically to a lower face 14 of the reaction vessel 4. This fluid adjusting means 16 has a pair of wall faces 16a and 16b for partitioning both side faces 19, 19 and the rear face continuous to both side faces 19, 19 of the reaction vessel 4. This pair of wall faces 16a and 16b consist of a pair of plate-shaped members extending from the lower face 14 to an upper face 17 within the reaction vessel 4. In the embodiment as shown in
The mounting positions A, A of the fluid adjusting means 16 are set in the following way. The shorter one between the shortest distance from the center (rotational axis) of the target rod 1 to the side face 19 of the reaction vessel, and the shortest distance from the center (rotational axis) of the target rod to the wall face of the fluid adjusting means 16 is assumed to be L. Also, an outer diameter of the glass particles deposit 5 is assumed to be d. The fluid adjusting means 16 is set up such that L is greater than d (L>d).
In the example of
Also, the apparatus for producing glass particles deposit according to this invention has gas ports 13 at positions closer to the face where the burners are placed than the mounting position in contact with the fluid adjusting means 16 on the side face 19, as shown in
Within the reaction vessel 4, it is required to form a uniform flow of fluid in a direction from the burners 2 to the exhaust ports 10 over the entire length of the target rod 1. Accordingly, it is desirable that the gas port 13 can blow out the gas uniformly at least over the entire length of the target rod 1. The gas port 13 can take arbitrary form in which a plurality of gas blowout holes or the long slits are arranged in parallel in a direction of the axis of the target rod 1. It is desirable that a gas blowout nozzle having a number of gas blowout holes for blowing the gas in the same direction is disposed in parallel to the rotation axis of the target rod 1, such that the gas blowout holes are directed toward the fluid adjusting means 16 on the same side. In any form, the flow velocity of gas blown out of each gas port 13 is desirably 30 m/minute or more.
In the case where there no disturbance, the temperature within the reaction vessel 4 rises due to the heat generated in synthesizing glass particles. The gas within the reaction vessel 4 is heated, and flows upward. The glass particles are blown in this upward flow of fluid, and tend to move upward within the reaction vessel 4, as indicated by the hatching in
In addition to the gas port 13 disposed near the side face 19 of the reaction vessel 4, a gas port 9 is desirably provided at an upper part of the reaction vessel 4. The gas port 9 is disposed above the holding means 6 of the target rod 1 and in parallel to the upper face of the reaction vessel 4, as shown in
The gas port 9 as shown in
It is desirable that the upper structure of the reaction vessel has the upper face 21 of the reaction vessel 4 formed with an inclined face increasing in height at a constant rate toward the rear face 15 of the reaction vessel 4, as shown in
The producing apparatus of
Also, it is desirable that a gas heating unit such as a coiled heater (not depicted) for heating the gas to be supplied to the gas ports 9 and 13 is provided, and the heated gas is introduced into the reaction vessel. Thereby, it is possible to prevent fracture or peeling off from occurring in the glass particles deposited layer because the low temperature gas is introduced into the reaction vessel to change the temperature distribution of the glass particles deposit.
In the producing apparatus of
Referring to
The invention has been described above mainly with regards to producing apparatus of the longitudinal type in which the glass particle synthesis burner and the target rod are relatively moved vertically, but may be applied to the producing apparatus of the transverse type.
The glass particles deposit was produced, using the rectangular reaction vessel 4 as shown in
Two gas blowout nozzles were installed directly near the mounting position on the side face 19 at which the fluid adjusting means is contact with the side face 19. The gas blowout nozzles had 300 gas blowout holes having a diameter of 1 mm at a pitch of 5 mm. The gas blowout nozzle was installed so that the gas blowout holes were directed toward the middle of the wall face on the same side. The range where the glass particles deposit 5 being produced can reciprocate was contained in the range where the gas blowout holes existed. The gas blowout nozzle as the gas port 9 was provided above the holding means 6 of the target rod 1 for the reaction vessel 4 and in parallel to the upper face of the reaction vessel 4. The gas blowout nozzle had 140 gas blowout holes having a diameter of 1 mm at a pitch of 5 mm. The gas blowout holes were directed to blow out a planar gas flow in parallel to the upper face of the reaction vessel 4.
As the synthesizing conditions of the glass particles, glass raw material gas, hydrogen gas, oxygen gas and argon gas were supplied at a rate of 12 liters/minute in total from the burners, and the clean air at room temperature was introduced into the gas ports 9 and 13 at a flow rate of 1 liter/minute for each gas blowout hole. The volume of the reaction vessel 4 was 3000 liters, and the total gas displacement was 3000 liter/minute.
Under these conditions, the glass particles deposit having a length of 600 mm and a diameter of 200 mm was produced. No lump of glass particles adhered onto the inside of the reaction vessel dropped down. Though in one of ten produced glass particles deposits a fracture which was considered to be caused due to the introduced air at room temperature was observed, the glass particles deposit of excellent shape and smooth surface was obtained. The glass particles deposit without fracture was vitrified within a furnace held at high temperature, such as 1500°, so that the excellent preform without irregularities and bubbles could be obtained.
The glass particles deposit was produced in the same way as in the example 1, except that the reaction vessel having a cross section as seen in
The glass particles deposit was produced in the same way as in the example 1, except that the upper portion of the reaction vessel has the structure as shown in
The glass particles deposit was produced in the same way as in the example 1, except that the clean air introduced into the reaction vessel was heated at 200°. No fracture was observed in any of ten glass particles deposits produced. This glass particles deposit was vitrified within the furnace held at high temperature, whereby the excellent preforms without irregularities could be obtained.
The glass particles deposit was produced using the reaction vessel having different shape of the inner face by varying the contained angle θ of
With the apparatus for producing the glass particles deposit according to the invention, the flow of fluid within the reaction vessel is smooth, and the floating dusts including excess glass particles which have not been deposited on the glass particles deposit were exhausted efficiently and rapidly, whereby the excellent glass particles deposit without irregularities could be obtained. If the heated gas was blown out, it is possible to prevent the occurrence of fracture in the glass particles depositing due to introduced gas at low temperature.
Number | Date | Country | Kind |
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JP 2001-218173 | Jul 2001 | JP | national |
This application is a Continuation-In-Part of application Ser. No. 10/197,536, filed on Jul. 18, 2002, which is incorporated herein by reference.
Number | Date | Country | |
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Parent | 10197536 | Jul 2002 | US |
Child | 11069039 | Mar 2005 | US |