JPS5911539B2 - Method and apparatus for producing glass fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method and apparatus for producing fibers from molten glass or other thermoplastic materials by centrifugal or rotational molding processes.

In this field of technology, glass fibers are produced in large quantities by feeding a stream of molten glass into a high-speed centrifuge or rotor having a plurality of openings in its circumferential surface so that the molten glass flows out through the openings by centrifugal force. This is well known.

The glass stream exiting the rotor opening is subjected to the action of a high-velocity gas blast, causing the molten stream to become fibrillated.
ua ting) into thin fibers or filaments.

The production rate of glass fibers that can be produced by such a method is a function of the number of openings around the rotor.

Therefore, in order to increase this production rate, more glass flow forming openings must be provided.

This can be done by increasing the peripheral surface area of the rotor over which the openings are drilled.

The peripheral surface area is increased by increasing the depth of the rotor and thus its diameter.

Increasing the depth of the rotor and thus its diameter creates glass flow and thermal uniformity problems that contribute to undesirable properties of the glass fibers.

Increasing the diameter of the rotor will result in a larger low pressure area immediately below the rotor and will have a greater impact on the stability of the fiber bale exiting the rotor.

Note that the fiber veil refers to a veil-like structure in which a large number of glass fibers flowing out from the rotor are formed.

The diameter of the rotor is 30.5 to 40.6 crfL (12
Experience has shown that when the fiber veil is increased to a range of 161 to 161 inches), the fiber veil becomes extremely unstable.

Unstable fiber veils tend to move haphazardly in all directions about the lower extension of the rotor's axis of rotation.

Such random movements affect the flow parameters for the gas flow from the burner and the fiberizing blast in the fiberizing zone.

The most affected area appears to be in the direction of the radially opposed random motion.

Due to these perturbed flow parameters, poor quality, non-uniform and undesirable fibers are produced.

If the fiber bale is continuously moved haphazardly in what is always the fiberizing zone, poor quality fibers are released therefrom, resulting in a non-uniform glass wool product.

The fiber veil instability phenomenon is not necessarily limited to large diameter rotors.

The unstable fiber veil has a diameter of 20.3 crfL (8i
It can also be formed on the underside of the rotor.

Generally, such instability phenomena are observed in gas flow turbulences that depend on the swirl strength of the high velocity gas just below the rotor.

The advantage of increasing the rotor diameter is that slower rotations (RPM) can be used for a given glass fiber production rate.

For example, the diameter is 20.3°, 30.5° and 38.5°. ICrr
The rotors of t (8, 12 and 151 nch) must be rotated at 3000.2000 and 1600 RPM, respectively, to produce 453.6 to 680.4 kg for one hour.
(1000 to 1500 pounds) of glass fiber cannot be produced.

Furthermore, the centrifugal force acting on the rotor at the above speed is 1
000.750 and 570g.

Therefore, a larger diameter rotor can be expected to have a longer useful life since it operates with less material strain.

A typical prior art technique for reducing the effect of the low pressure zone on the underside of the rotor and controlling the fiber veil is U.S. Pat.
No. 14618, No. 328572, No. 3179507, No. 3372011, No. 2855626 and No. 3
No. 040377.

The first three U.S. patents cited utilize devices to physically force the fiber veil outward from the central axis of the underside of the rotor.

This can be done by providing structures within the fiber veil, such as structures with conical surfaces that widen downwards, or by introducing gases such as air or steam into areas of low pressure that reduce their strength. has been achieved by.

In the remaining three US patents, a tapered rotating body is provided at the bottom of the rotor as a device to reduce unstable flow under the rotor.

A conical shape, which is easy to manufacture, is not the most suitable shape for the low pressure area.

Such diversion conditions create characteristic small swirls of gas and fibers flowing upwardly along the conical surface.

Additionally, in such cases, glass fibers, fiberizing media (at
Experience has shown that the cone operating temperature is such that the fibers impact and adhere to the cone surface.

Needless to say, under such conditions the flow parameters for the fiber veil will be destroyed.

In the present invention, the flow parameters for the fiber veil are stabilized by providing a flow control device whose shape or appearance is controlled by the gas flow bounding the low pressure zone below the rotor. Approximate a streamline about .

An appropriate amount of gas is added to the region or boundary layer between the low pressure area and the gas flow and is forced along the geometry of the gas flow control device so that the boundary layer on the surface of the flow control device is This results in a relatively cold boundary layer.

The cold boundary layer also controls the surface temperature of the flow control device by reducing heat transfer across the boundary layer.

Furthermore, this cold boundary layer forms a dynamic barrier of dense gas to prevent the fibers from impinging on the flow control device.

Two basic types of flow control devices are within the scope of this invention.

These include laminar boundary layer flow and swirling boundary layer flow.

Although not required within the scope of the present invention, it is preferred to surround the flow control device and utilize its internal volume capacity as an accumulator.

This eliminates any fluctuations in the feed gas and provides a smooth continuous flow of gas to the boundary layer.

It is an object of the present invention to provide an improved method and apparatus for stabilizing flow parameters for a fiber veil immediately below a centrifugal fiberizing device.

Another object of the present invention is to provide an improved method for uniformly maintaining a uniform operating temperature of a flow control device immediately below a centrifugal fiberizing device.

Yet another object of the present invention is to provide an optimal flow control device geometry with laminar or vortex flow.

Further objects and advantages of the invention will be explained in more detail below by means of embodiments of the invention illustrated in the accompanying drawings.

These descriptions are for illustration of the invention and are not intended to limit the invention.

Referring to the accompanying drawings, FIG. 1 shows a centrifugal rotor 10, which is rotated by a drive spindle or flexure shaft 11. FIG.

The rotor 10 receives a flow of molten material 12, for example glass, which is forced there by centrifugal force from inside the rotor surface 13 to the outside.

Due to the hydrostatic pressure acting on the molten glass, the molten glass
It is forced to flow through a number of holes 16 made in the rotor surface 13.

The resulting flow of molten glass 14 is acted upon by an annular blast of hot combustion gases exiting from an annular burner port 15, directing the molten glass flow downward.

Note that the annular blast herein refers to the blast that flows out from the annular burner port 15.

Furthermore, a jet of high pressure gas is discharged via the blow nozzle 20.

The combination of the high temperature high pressure gas from the burner 15 and the high pressure gas discharged from the blow nozzle acts on the molten glass stream 14 and attenuates it into fibers 2.
1 is formed and the fibers are directed and accelerated into a cylindrical fiber veil 22 flowing under a high velocity gas.

Note that the cylindrical fiber veil herein refers to one in which a large number of glass fibers are formed into a cylindrical veil shape by an annular blast.

Due to the above-mentioned action, the area of trapped gas 23 is below ambient pressure, which area is immediately below the rotor 10.

In such an area 23 there is a backflow as indicated by arrow 24.

The flow 24 within this low pressure zone 23 is generally unstable, thereby causing similar instability in the fiber veil 22.

The fiber veil 22 ends up moving haphazardly due to lack of strategy.
The result is an unsatisfactory and non-uniform product.

FIG. 2 depicts one embodiment of the invention in which an apparatus and method as described above for forming glass fibers 21 by feeding a stream of molten glass 12 to high speed rotor 10 is shown. , has been improved as follows.

The deflection shaft 11 extends below the rotor 10, to which the flow control device 29 is mounted by suitable means, for example a disc-shaped support 34.

The flow control device 29 is, geometrically speaking, a coaxial rotating body that is coaxial with the rotor 10 .

Such coaxial rotating bodies may have a frusto-conical shape, but more preferably their shape approximates the streamlines of the gas flow forming the low pressure zone below the rotor 10.

Even if the shape of the flow control device 29 is not an immediate issue.

The shape of such a rotating body may be, for example, parabolic, hyperbolic, or elliptical.

In short, it is preferable that the rotating body has a tapered shape.

The flow control device body begins at 31 immediately below the rotor face 13 and extends toward the axis of the rotor according to a predetermined shape, leaving an annular open space or slot 35 between it and the rotor 10. It continues downwardly and inwardly to the level of the truncated head 32 and thence horizontally to a flexible shaft extension 33 and is suitably attached to this extension.

This creates a plenum chamber.
) 40 is defined by the disc-shaped support 34, the flexible shaft extension 33 and the flow control device shape 30.

A relatively cold gas, such as air 41, is admitted into the central passage 42 of the flexible shaft 11 and is forced into the chamber 40 through a suitable opening 43.

A restraint 44 closes the central passage 42 below the opening 43 and forces the cooling gas into the chamber 40 .

Cooling gas flows from chamber 40 through suitable openings 45 in support 34, passes along the bottom of rotor 10, exits through annular slot 35, and flows downward along a flow control device. The side is injected as indicated by arrow 46 to form a boundary layer.

The cooling boundary layer flowing along the flow control device shape 30 reduces aerothermodynamic heat transfer from the hot veil 22 to the flow control device shape 30.

It is necessary to maintain the flow control device below 380° C. (700° F.) to prevent fibers from striking and sticking to the flow control device.

Furthermore, since relatively cool gas is injected, the density of the boundary layer is relatively high, so the tendency of the fibers to pass through this boundary layer, and the flow control device configuration 3.
The tendency to hit zero is reduced.

2.72 to 3.4 atm (40 to 50psi
) 0.84945 m'/ii
n (30 ctm) of standard factory general purpose compressed air per hour.
diameter 30.5 to 38.1 cffL (12 to 15 inches) producing 500 pounds) of glass fiber.
ches) rotor.

The flow control device 29 occupies the low pressure zone immediately below the rotor 10 (indicated by 23 in FIG. 1) which has the greatest influence on the flow parameters for the fiber bale, and provides an optimum flow profile 30 at high speeds. fiber veil 22 and follow it.

By providing flow control devices in such areas,
It provides a solid geometry and stabilizes the fiber veil 22 without the instability that occurs in fiber veils.

Diameter 30.5 to 38, ICWL (12 to 151
45 per hour) and has a rotor of approximately 45
3.6 to 680.4 kg (1000 to 1500
For glass fiberizing equipment that produces glass fibers of 100 to 300 m2, a suitable length to rotor diameter ratio is about 0.7.

For a rotor with a diameter of approximately 20.3 cIrL (81 nch), this ratio may be greater than 1.0.
).

A smaller, less extreme low pressure area is left below the flow control device.

However, because of the flow control device 29, its area is much smaller than area 23 in FIG.
The effect on the stability of the fiber veil is very small.

Furthermore, because of the flow control device 29, the fiber veil 22
It is already stabilized by flowing along the shape 30 before being influenced by the remaining low pressure area 47.

The kinetic energy imparted to the fiber veil 22 along the control flow path defined by the shape 30 stabilizes the fiber veil before being affected by the less severe low pressure area 47.

FIG. 3 shows another embodiment of the invention in which the flow control shape 50 does not follow the separation streamline between the fiber veil 22 and the low pressure zone 23 shown in FIG. , is parallel to this streamline on the inside.

As a result, the flow control shape 50 combined with the geometry of the rotor 10 forms an aft step 51 with respect to the flow of the fibers 21 flowing downwardly from the rotor and tapering.

Due to this backward step 51, turbulence 52 is created along the shape 50.

A gaseous cooling medium, such as air or steam, is connected to the flexible shaft 11.
2 and into a plenum chamber 40 as in the case shown in FIG.

This cooling gas also flows between the rotor 10 and the flow control shape 5.
is added to the turbulent flow 52 via an annular slot 53 formed by

The cooling turbulence 52 along the flow control shape 50 has an increased cooling effect on the flow control body.

However, the fibers have a greater chance of striking the flow control feature 50 than with the laminar flow control shown in FIG.

FIG. 4 shows yet another embodiment of turbulence control, which also uses a rear step to create turbulence along the flow control shape 50.

However, in this embodiment, a lip or shield 55 is provided to protect fibers from occasionally striking the bottom of the rotor 10.

This is because a small backflow section 56 occurs particularly below the rear step.

A cooling gas flow is indicated by arrow 57 and is injected into the boundary layer through an annular slot 58 formed between rotor 10 and lip 55.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a low pressure area on the lower side of a rotor to which the present invention is not applied. FIG. 2 shows an embodiment of the invention in which laminar flow is provided between the rotor surface and the flow control device and over the flow control device. FIG. 3 also shows an embodiment of the invention, in which a rear step is provided between the rotor and the flow control device, and this rear step creates a vortex flow that follows the shape of the flow control device. FIG. 4 is a diagram showing another embodiment of the embodiment shown in FIG. 3. 10... Rotor, 13... Rotor surface,
22... Fiber veil, 29... Flow control device, 47... Low pressure area, 50...
Flow control device shape, 51... Rear step.

Claims (1)

[Claims] 1. A method for forming glass fibers by converting molten glass into a glass stream using a centrifugal device, comprising:
engaging the glass stream in a high-velocity, hot annular blast around the centrifuge, thereby reducing the glass stream to fine fibers and cylindrical fibers flowing around a coaxial rotor immediately downstream of the centrifuge; In a method adapted to transport said fibers as a bale axially away from said centrifugal device, the flow of said fibers within said bale is increased by additionally injecting a continuous flow of gas into a boundary layer on the surface of said rotating body. A method characterized in that the heat transfer from hot gases to the rotating body is reduced. 2. A device for producing glass fibers by supplying molten glass to a centrifugal device provided with a plurality of openings around the periphery, wherein the molten glass is diverged from the openings into a molten stream, and Under the action of a hot, high-velocity gaseous fiberizing means discharged in the periphery of the centrifugal device, said fiberizing means is directed into engagement with said molten stream of emitted glass and is moved away from said centrifugal device. A manufacturing apparatus for producing an axially flowing glass fiber veil, comprising: a tapered rotating body located within the fiber veil and immediately downstream of the centrifuge;
An apparatus characterized in that it is further provided with a device for additionally supplying a continuous fluid flow to the boundary layer on the rotating body.