JPS6015582B2 - Method for pulling out glass tubes without deforming their surfaces and air support device for glass tube arrays - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Glass tubes have been drawn from a source of molten glass in a variety of ways, including outer diameters from 5 mm to 65 mm. Small diameter tubes in the range of the remeter are typically drawn by pulling the tube along an elongated horizontal path defined by a plurality of support rollers.

Although such rollers are made from graphite, some deformation or damage to the surface occurs when the hot tube is pulled horizontally over the roller, especially when the tube is still plastic. It is a well-known fact. This deformation increases linearly with manufacturing speed; because increasing manufacturing speed is accompanied by higher forming temperatures and thus makes the tube more susceptible to deformation. This relationship naturally limits the production capacity of any array since there is an apparent limit to the degree of deformation that can be tolerated in tube manufacture. Coming
British Patent No. 1025500 to GlassWorks discloses a device for supporting drawn tubes on a cushion of air.

This air cushion is provided by an upward airflow that passes through a generally U-shaped perforated board made of solid metal, the board being slightly larger than the outside diameter of the glass tube. diameter, and the amount of air flow is sufficient to create a cushion of air between the lower surface of the tube and the semi-cylindrical air supply board. The obvious disadvantage of this construction is that it is only valid for certain diameters of tubes. Those skilled in the art will appreciate that modern tube manufacturers must be able to manufacture tubes in a wider range of diameters and weights to meet market demands. Since the length of the plastic range of the array of hot glass tubes varies from 20 feet to 50 feet, each time a desired change in tube diameter is made, an air hole of the appropriate diameter is prepared using the apparatus shown in the aforementioned British patent. It is clearly impractical to use slat members. For effective operation, downtime caused by changes in the work of the tube array must be kept to a minimum, so mechanical changes to the tube support mechanism are not allowed.
SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a method for drawing a glass tube having a softened surface to the extent that it is susceptible to deformation, without deforming the surface, and an improved device for supporting the drawn hot glass tube on a cushion of air. hand,
A relatively wide range of tube diameters and linear weights (lin
It is an object of the present invention to provide an improved device as described above, which can be effective against C. earwei scales.

The invention contemplates providing a horizontally elongated air chamber located below the tube withdrawal path.

The top wall of this air chamber is made of graphite and has approximately 1000 subtended angles.
defining a V-shaped notch having a diameter (e); Slot-like openings are provided in a longitudinal array along the length of the V-shaped top panel, with the slots extending across the top of the panel. The dimensions of the slot are selected to provide effective air flow for each of a relatively wide range of tube diameters and weights drawn through the notch and supported by the upward passage of air through the slot. . The air pressure inside the air chamber is higher than the surroundings,
carefully controlled and selected as a function of tube diameter and linear weight. In order to minimize bowing of the tube due to air support, several modifications are proposed to provide cooling air flow to the top of the tube.

The present invention will now be described in more detail with reference to the accompanying drawings.

As is well known in the art, a tube pullout array may include 20
It comprises an elongated structure having an overall length of about 0 feet and a height of about 2 feet.

One end of the array is located adjacent to a glass furnace that provides a continuous supply of molten glass to a tube-forming mandress or tube-drawing orifice to form the hot glass into a tube shape. The tube-shaped molten glass is then pulled through a vertical path from the mandrel or orifice to assume a horizontal position and extended a sufficient distance downwardly onto the tube array.
The drawn plastic tube is cooled sufficiently to be hard enough to contact conventional tube processing equipment, such as drawing belts and cutting saws. Although a wide variety of structural members may be used to define the tube support mechanism, and a specific structure is shown in the drawings, the essential elements of the chicheap array 1 shown in the drawings are the primary plenum chamber 10. It should be understood that this includes Supported above the primary plenum 10 is a pressure control chamber 20 whose top wall 21 defines a continuous row of orifices 30 and supports a hot tube T in a position out of contact with the top wall 21. Exhaust enough air to do so. The primary air pressure chamber 10 includes four channel-shaped frame elements 11a, 11b,
11c, 11d by a bolted (or welded) assembly. Elements 11a and 11b constitute the side walls of chamber 10, and elements 11c and 11b constitute the bottom and top walls of chamber 10, respectively. The top channel member 11d is
a depending sheet metal structure 2 provided with an elongated slot 11e and forming part of a pressure control chamber 20;
It is possible to insert 0. The pressure control chamber is conveniently formed by assembling a plurality of identical units in longitudinal abutting relationship.

The top of each pressure control chamber unit 20 is defined by a pair of laterally spaced upright sidewall members 23a and 23b having horizontal flanges 23c and 23d, respectively, at their bottom ends. The bar 24 is fixed with a bolt to a bar 24 extending in the longitudinal direction, and the bar 24 is inserted into the nuchal wall 11d near the side edge of the recess 11e.

An integral horizontal flange 22a formed at the top of depending sheet metal member 22 is also secured to bar 24 by the same bolts. The upright wall members 23a and 23b have at their tops upwardly outwardly sloping flanges 23e and 23f, respectively, to which the top wall 21 is secured by suitable bolts 21a.

Mounting plates 23g and 23h are connected to top wall 21 and flange 2.
3e and 23f. More particularly, the top wall 21 is made of a V-shaped material made of carbon, graphite, or other materials known to minimize the formation of scratches on hot glass that may accidentally come into contact with such a top wall. It forms the elements of the shape. To facilitate the manufacture of the top wall 21, the top wall 21 is advantageously made from two identical cushions 21b and 21c, with section 2
1b and 21c are arranged so as to be in an abutting relationship at the apex angle formed by the top wall 21. An orifice 30 is defined by a matching groove 21e at the abutting surface of sections 21b and 21c, through which sufficient air is directed to support the hot glass tube T, so that the tube T deforms into a tube T; It is cooled to a temperature that can be supported by conventional graphite rollers without risk of damage. The specific dimensions of the orifice 30 defined by the slot 21e in relation to the diameter and weight of the tube will be detailed below. The internal angle defined by the top surface of the top wall 21 is between 85o and 120o.
Therefore, for the purpose of the present invention, it can be said that the size is about 100 degrees.

An internal angle of this magnitude provides a wide range of variations in wall thickness for air support of hot glass tubes T from 5 mm to 60 mm in diameter, i.e. the linear weight of the supported tube
It has been confirmed that this method gives sufficiently satisfactory results, taking into account the following conditions: 20 chamber units each
A sheet metal end plate 25 is provided so that the pressure within each chamber unit 20 can be individually controlled.

A conventional air pump 5 is connected to one end of the primary plenum chamber 10 to maintain the air pressure in the chamber at least 2 inches of water above atmospheric pressure. Naturally, the exact pressure within the primary charging chamber 10 may vary along the length of the tube passage 1: because there is a temperature factor and also because of the change in volume in a particular part of the chamber with respect to pump evacuation. This is because there is a difference. The air support system embodying the invention requires that a carefully controlled superatmospheric pressure be maintained within the pressure control chamber unit 20.

This controlled pressure is obtained by providing a plurality of selected area inlets, preferably valved inlets 25, along the length of the bottom 22 of each control pressure chamber 20. Each entrance 25 has an adjustable valve element 26 having a tapered head 26a, the valve element 26 being axially movable with respect to the orifice 25 to adjust the effective flow through the associated orifice. It becomes. The valve head 26 is securely attached to the end of a bolt 27 which is slidably attached to the actuation plate 28.

A counter 28a working between the valve head 26a and the plate 28 is
The valve head is kept in the extended position with respect to the actuating plate 28. Each board 28
has two valve elements 26. The actuating plate 28 is mounted for reciprocating transverse movement with respect to the closure 25 supported by a pair of bolts 29 which are connected to reinforcements provided on each side of the lower end of the sheet metal wall section 22. It is screwed onto the plate 22c. A spring 29a surrounds each bolt 29 and urges the actuating plate 28 laterally away from the orifice 25. The actuation plate 28 is laterally adjusted in 4-increments by an adjustment mechanism comprising a threaded shaft 31 secured to an intermediate portion of the actuation plate 28 and extending laterally through the side wall 11b of the tube passageway. Can be adjusted.

A rattan support bracket 32 having a U-shaped cross section is attached to the side wall 2
2b, and the shaft 31 is supported by each of the arms 32a and 32b. Arm 32b has a slot entrance (not shown). Arms 32a and 32b
An annular extension 33 of the adjustment knob 34 having a female thread (not shown) cooperating with the male threaded end portion 31a of the shaft 31 is inserted between the knobs 34 and 31 so that the rotation of the knob 34 is The movement results in an axial movement of the adjusting shaft 31 and a corresponding lateral movement of the actuating plate 28 and of the valve head 56 relative to the opening 25. Pressure control chamber unit 20
The exact air pressure present inside each of the tube arrays 1 is detected by a tube 50 extending upwardly within each chamber, and the detected pressure is transferred to the tube array 1 by means of flexible hoses 51 and fittings 52. taken outside.

The fitting 52 is connected to a pressure indicating meter 53, shown only in FIGS.
3 and the adjustment is made by operating the respective adjustment knob 34 on the valve head 26 with respect to the closure 25.
This is done by changing the position of a to maintain a desired pressure inside each of the pressure control chambers 20. In order to make the pressure within the chamber 20 more uniform, it has been found desirable to arrange an arcuate perforated baffle plate 7 between the lower and upper parts of the chamber 20. The above is a tube array.
The length of 1 unit of the air support portion of 1 has been appropriately described. Such units are conveniently made as long as about 10 inches. A plurality of identical units 20 are secured end to end to form an air support for an array of flexible tubes as shown in FIG. The number of chamber units 20 provided is . Determine the accuracy of adjustment of support air pressure control.

Similarly, the number of air intake ports 25 plays a significant role in the accuracy of maintaining the desired pressure within each pressure-controlled chamber 20. Preferably, one controlled air intake opening 25 is used for each 4 to 6 inches of tube passageway 1. Tube T to be supported by air
Exhaustive testing and calculations are required to determine the appropriate correlation between the size and number of air supply orifices 30 and the pressure within pressure controlled chamber 20 in terms of weight and size.

Of course, it is possible to calculate the static air pressure required to perform a specific magnitude of lifting and linear weight lifting above the supporting V-shaped surface 21b. This would be the pressure that would provide a lifting force in excess of the linear unit weight of the hot glass tube T, and would be the pressure applied in an area equal to the area for engagement of the tube wall with the top surface 21 of the V-shape. Will. Unfortunately,
This easy approach does not yield adequate results in practice. Since the tube T is lifted out of contact with the top surface 21, the dynamic effects of the airflow must be taken into account. There is a constant pressure drop across the orifice 30. The effect of airflow through the curved surface of the tube is the flattening effect of airflow onto the curved surface.
) is considered to cause downward forces at vertical angles to the neck slopes of the blocks 21b and 21c, respectively.

This is the effect of self-centering (self, center).
action). Since we are dealing with a hot glass tube at a temperature where the glass walls of the tube are still plastic, the blowing of air that contacts the bottom of the tube has the effect of causing an inward deformation of the tube wall. Additionally, the volume of airflow should be as low as possible to minimize cooling of the bottom of the tube that would result in curvature. Add to this that all tube arrays must be able to produce a relatively wide range of tube diameters and weights, and the continuation of the tubes in an elevated position with respect to the top wall 30 of the air support system air supply nozzle 3 capable of working with all tubes of a given size and weight range to maintain
It will be readily apparent that choosing the shape and dimensions of 0 is difficult. Graphite block 21b, 2
Since it is impractical to remove the Achieve Array and provide an air supply nozzle 30 of a different size or shape to change the pressure control chamber 201, the control of the air pressure present in the pressure control chamber 201 is limited to a range of tube dimensions and weights to be adjusted. This necessarily becomes the only convenient variable available to provide adequate control of the device. Tube diameter range from 5 to 65 mm and from 0.15 mm/skin to 78 mm
．． 09/For the accompanying range of skin tube weight,
Slot widths on the order of 1/8 inch, lengths of 1/16 inch, and slot spacing of 1/4 inch give highly effective performance for all weights from 10 mm to 25 mm tube diameters, and 5 mm. It has been determined that acceptable performance can be given for tube diameters ranging from 25 to 10 millimeters in diameter and 25 to 65 millimeters in diameter.

Naturally, in order to properly support tubes of large dimensions,
A large value of air pressure must be maintained in the pressure control chamber 20, and for small dimensions a low pressure must be maintained. Experiments have shown that the weight of the tube (which, of course, is
(which is a function of the tube wall thickness) is a more effective indicator for determining the amount of static pressure required within the pressure control chamber 20 to adequately support a tube of a particular size and weight within the aforementioned ranges. It became clear that. Referring to FIG. 8, there is shown a graph showing the required static pressure (inches of water) versus tube weight (water/skin). This graph shows curves for tube diameters ranging from 5 to 65 millimeters, from which the appropriate hydrostatic head to be maintained within the pressure control chamber 20 can be conveniently determined. Looking at Figures 9 and 10,
Another construction of the top wall of the air support unit is shown which has the advantage of allowing more convenient regulation of the upward airflow from the pressure control chamber unit 20.

Like reference numerals in FIGS. 9 and 10 indicate the same components described above in conjunction with the embodiments of FIGS. 1-8. The top wall 12 is defined by a plurality of longitudinally abutting and laterally spaced block elements 121b, 121c. The support flanges 23e and 23f of such block elements each have a laterally elongated slot 122, which slot 122 is connected to the chamber side wall portion 2.
Support flange heaves formed on top of 3a and 23b. It receives the bolt 21a which secures the locking element. As in the embodiment of FIGS. 1-4, plates 123g and 123h may be mounted between flanges 23e and 23f and overlying blocks 121b and 121c, respectively. This plate has a slot 123 for receiving a bolt 122. Blocks 121b and 1
Laterally adjacent end surfaces 121d and 121e of 21c
can be adjusted to provide the desired degree of separation or orifice 121 between these surfaces, which of course determines the effective flow area presented to the pressurized air within the upwardly flowing chamber 20. to provide support for the hot glass tube T. With this modification, it is not necessary to replace the graphite blocks 21b and 21c of the embodiment of FIGS. 1-4 in order to change the effective airflow flowing upwardly over the top wall 21 providing support for the hot glass tube T. Another limiting factor in the volume of support air flow, which is particularly important in the case of 4.4 diameter tubes, is the cooling effect of such air flow on the bottom portion of the supported tube.

This effect is caused by the bottom of the tube cooling more rapidly than the top, known in the art as a "b-shaped"
ow)” condition, causing stress in the tube on final cooling and causing it to arch upwards. Therefore, the dynamic air flow for small size tubes is
The formation of "bows" should be kept to a minimum, or supplemental cooling means may be provided to cool the top of the tube simultaneously, resulting in non-uniform cooling between the top and bottom. Preferably, the generation of stress is avoided. One approach to achieving cooling of the top of a hot glass tube supported on an air support device embodying the invention is to direct a flow of cooling air to the top of the hot glass tube.

That is, referring to FIG. 5, an air manifold 35 serves to direct the air in the elongated sheet metal.
is provided, which is connected to a suitable source of pressurized air and has a longitudinally extending exhaust passage defined by a tapered sheet metal element 35a;
This sheet metal element 35a extends along the top of the hot glass tube T, which is supported by the air support device described above. However, it has been found that this cooling system cannot be effective in significantly reducing the degree of bowing caused to hot glass tubes by the air support system unless it is positioned at a specific location along the tube array. Ta. It is known in the art that the longitudinally drawn tubes of an array undergo a helical motion such that the portion of the hottest area around the glass tube moves in a helical path. This area is usually opposite the area initially contacted by the air support. The longitudinal center of the air manifold is therefore preferably positioned at the position shown in FIG. 5 so that the trajectory of the hottest region of the tube traverses over the top of the air-supported tube. The convective cooling that is necessary and thus provided clearly reduces bowing of the air-supported hot glass tube. Another device for providing controlled cooling of the top of the tube is shown in FIGS. 6 and 7.

Hot glass tube T placed horizontally on air support device
The top of the air support block 21c and 21d is enclosed within a tunnel 42 defined by the placement of suitably shaped graphite blocks 41a and 41b on the mirrored top surface 21d of the graphite air support blocks 21c and 21d. As best shown in FIG. The blocks are preferably constructed as identical sections 41a and 41b, which have beveled bottom surfaces 41c and 41d to conform and ride on the bevels of the top surfaces of air support blocks 21a and 21b. Each block 41a and 41b extends upwardly and inwardly to define a vertical wall surface 41e in mating relationship with a laterally adjacent block. inches, and the sections are aligned longitudinally to achieve the desired overall length. That is, block sections 41a and 41b cooperate to form a generally hexagonal cross-section tunnel 42.
The tunnel 42 extends along the tube array from the hot end to a point where the tubes are sufficiently cooled in a compensating fashion to minimize the possibility of bowing. The cold end of tunnel 42 is connected to a vacuum plenum (vacuum plenum).
The vacuum plenum 43 is connected by a tube 44 to the inlet side of a suitable pump (not shown). This vacuum connection directs a flow of cooling air over the entire length of the tunnel, entering at the hot end of the tunnel 42, passing through the vacuum plenum 43, and exiting at the cold end of the tunnel.

Obviously, the absolute pressure at the top of the tunnel 42 can be reduced somewhat compared to the surroundings, which has a synergistic effect since an air support device is involved: this is because the hot glass tube T The supporting air necessary to create an upwardly directed differential pressure between the bottom side and the top side of the tube T to support the tube and be placed under the tube T through the nozzle 30. This is because it reduces the pressure of It has been found that the apparatus described above significantly reduces the bowing of air-supported hot glass tubes by the apparatus embodying the invention, and at the same time reduces the pressure of the supporting air. Abutment surface 41e of blocks 41a and 41b
More effective cooling may be achieved by providing a plurality of longitudinally spaced slots 41f. If such a slot is provided, it is desirable to provide a hood 43 over the tunnel block to minimize the amount of airborne dust that may be drawn into contact with the tube T.

[Brief explanation of the drawing]

FIG. 1 is a reduced perspective view of a portion of a tube draw array incorporating an air support device in accordance with the present invention. 2 is an enlarged schematic side view of a portion of the tube array of FIG. 1; FIG. FIG. 3 is a longitudinal cross-sectional view taken along plane 3-3 of FIG. FIG. 4 is a partial top view of FIG. 1, with a portion cut away to make it easier to see. FIG. 5 is a schematic perspective view of one type of cooling device designed to avoid arching of air supported tubes. FIG. 6 is a schematic perspective view of a modified form of the cooling device. FIG. 7 is a partial cross-sectional view of FIG. 6. 8th
The figure shows the relationship between desired air pressure and tube diameter and linear weight. FIG. 9 is similar to FIG. 3 and shows a modified structure of the tube array's terminal wall. FIG. 10 is a partial top view of FIG. 9. 1・
...Tube array, 7...Archive-shaped perforated block, 10...Primary air chamber, 11a, 11b,
11c, 11d...Four elements having a channel shape, 20...Pressure control chamber, 21...Top wall, 2
1c... Alignment slot, 22... Hanging metal sheet metal structure, 26... Valve head, 26a...
・・・・Head with 7-pa attached, 28・・・・・・
Actuation plate, 30... Orifice, 34... Adjustment knob, 50... Tube, 51... Flexible hose, 53
・・・・・・Pressure indicator hose. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Scope of Claims] 1. An apparatus for supporting a hot glass tube drawn from a source of molten glass on an air cushion, 1
a horizontally elongated chamber mechanism disposed below the withdrawal path of the tube, the chamber mechanism comprising a primary air chamber and a second chamber for maintaining a selected high air pressure;
3. the pneumatic pressure reduction chamber has a top wall that is V-shaped in longitudinal section and defines a groove in which the tube is disposed; 4. the top wall includes:
a plurality of longitudinally spaced orifices, the orifices traversing the top portion to permit upward flow of air from the air pressure restriction chamber, the width and length of the orifices; supporting a hot glass tube drawn from a source of molten glass on an air cushion, characterized in that the air pressure is selected as a function of the diameter and weight magnitude of the glass tube to be air supported; equipment for. 2. The device according to item 1, wherein the top portion of the top wall is made of graphite. 3. The device of claim 1, wherein the top walls are defined by laterally abutting identical graphite blocks, the abutting surfaces having vertical grooves defining the orifice. The device is characterized in that: 4. In the device according to item 1, 2 or 3 above, the V
The device characterized in that the inner angle of the glyph-shaped groove is about 100°. 5. The apparatus of claim 1, wherein the air pressure restriction chamber includes a horizontally extending housing defining a second air chamber extending adjacent and parallel to the primary air chamber; a pump for increasing the pressure of air in an air pressure restriction chamber, a plurality of longitudinally ablated apertures interconnecting two such chambers, and adjustment means for adjusting the effective flow area of each aperture; The device characterized in that it includes: 6. In the device according to item 1, 2, 3 or 4 above,
Apparatus characterized in that the pneumatic pressure restriction chamber includes a longitudinal assembly of identical chamber units. 7. The apparatus of paragraph 1, having an air directing air manifold on the top wall for directing the flow of cooling air over the top of the air-supported hot glass tube so that the tube is arcuate. The device is characterized in that: 8. The apparatus of claim 7, wherein the air directing air manifold includes an elongated plenum chamber having an elongated exhaust opening extending along the top of the air-supported tube and for directing pressurized air into the plenum chamber. A device characterized in that it comprises means for supplying pressurized air. 9. The mansion of paragraph 3 above, including an air directing manifold in the top wall for directing the flow of cooling air over the top of the air-supported hot glass tube to minimize bowing of the tube. The device is characterized in that: 10. The apparatus of claim 7, wherein the air directing manifold has an elongated cover defining a tunnel through which a tube of hot glass passes and rests on the top surface, and a cold end of the tunnel is evacuated. said apparatus including coupling means connected to a source, thus producing a flow of cooling air along the top of the hot glass tube from the hot end of the tunnel to the cold end. 11. Apparatus according to claim 8, characterized in that the center of the outlet opening of the air directing manifold is located such that the trajectory of the spiral hot region of the glass tube traverses above the top of the glass tube. Device. 12. The apparatus of paragraph 10, wherein the cover comprises a plurality of pairs of identical graphite blocks longitudinally aligned on the top surface, each pair of blocks having a laterally abutting relationship. The device is characterized in that: 13. Apparatus according to paragraph 10 above, characterized in that a plurality of longitudinally spaced openings are provided in the cover, adapted to introduce the cooling air flow at a number of points along the tunnel. Characteristics of the device. 14. The apparatus of claim 12, wherein the graphite abutment surface has a plurality of slots defining inlet passages for cooling air flow into the tunnel. Device. 15. A method for drawing glass tubes of different weights and diameters from a source of molten glass without substantially deforming the surface of the glass, comprising: 1. drawing out the glass tube; 2 passing the hot deformable part of the glass tube thus drawn between two walls forming a horizontally long V-shaped groove; 3 feeding primarily from the bottom lowest point of said V-shaped groove; supporting the glass tube in the V-groove without contacting the groove with an upward airflow, and simultaneously applying a cooling airflow to the top of the air-supported glass tube to cool the glass tube. A method characterized in that the air-supported glass tube is subjected to substantially uniform circumferential cooling until the air-supported glass tube is cooled to a temperature at which it is no longer deformable. 16. The method of claim 15, further comprising limiting the fluid pressure of the supply air as a function of the weight and diameter of the drawn glass tube.