U.S. patent application number 10/539125 was filed with the patent office on 2007-03-08 for method and apparatus for forming glass flakes and fibres.
Invention is credited to Charles Watkinson.
Application Number | 20070051136 10/539125 |
Document ID | / |
Family ID | 32670965 |
Filed Date | 2007-03-08 |
United States Patent
Application |
20070051136 |
Kind Code |
A1 |
Watkinson; Charles |
March 8, 2007 |
Method and apparatus for forming glass flakes and fibres
Abstract
Apparatus for forming fibres or flakes of material comprises
means (1) for producing a heated stream of molten material (9),
means for feeding the stream in a substantially vertically downward
direction and means (7) for receiving the downwardly directed
stream and for forming fibres or flakes therefrom. The apparatus
includes means (11, 13, 15, 17) for effecting a change in the
temperature of the stream subsequent to the production thereof
whereby fibres or flakes of a desired thickness are obtained.
Instead of, or in addition to, the temperature changing means,
there may be provided means for controlling the mass or volume flow
of the stream. The invention also provides methods corresponding to
the apparatus.
Inventors: |
Watkinson; Charles;
(Yorkshire, GB) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Family ID: |
32670965 |
Appl. No.: |
10/539125 |
Filed: |
December 19, 2002 |
PCT Filed: |
December 19, 2002 |
PCT NO: |
PCT/GB02/05794 |
371 Date: |
April 27, 2006 |
Current U.S.
Class: |
65/384 ; 65/441;
65/469 |
Current CPC
Class: |
C03B 37/005 20130101;
C03B 37/07 20130101; C03B 37/05 20130101; C03B 5/26 20130101 |
Class at
Publication: |
065/384 ;
065/441; 065/469 |
International
Class: |
C03B 37/07 20060101
C03B037/07; C03B 37/01 20060101 C03B037/01; C03B 37/04 20060101
C03B037/04 |
Claims
1. Apparatus for forming fibres or flakes of material comprising
means (1) for producing a heated stream of molten material (9),
means (3) for feeding the stream in a substantially vertically
downward direction, means (7) for receiving the downwardly directed
stream and for forming fibres or flakes therefrom, and means (11,
13, 15, 17) for effecting a change in the temperature of the stream
subsequent to the production thereof whereby fibres or flakes of a
desired thickness are obtained, characterized in that said
temperature changing means are means for directly heating the
stream by application thereto of microwave radiation or electric
current while the stream is traveling in a vertically downward
direction.
2. Apparatus according to claim 1, wherein the apparatus is
additionally provided with means for cooling the stream prior to it
being fed in a downward direction.
3. Apparatus according to claim 2, wherein the cooling means
includes a conduit (3) through with the stream is fed, said conduit
being surrounded by a cooling coil or jacket (23) through which an
appropriate fluid may be fed.
4. Apparatus according to claim 1, wherein the apparatus is
additionally provided with mass or volume flow control means.
5. A method for forming fibres or flakes of material comprising
producing a heated stream of molten material, feeding the stream in
a substantially vertically downward direction, receiving the
downwardly directed stream and forming fibres or flakes therefrom,
and effecting a change in the temperature of the stream subsequent
to the production thereof whereby fibres or flakes of a desired
thickness are obtained, characterized in that the change in the
temperature of the stream is affected by directly being the stream
by application thereto of microwave radiation or electric current
while the stream is traveling in a vertically downward
direction.
6. A method according to claim 5, wherein, in addition to effecting
a change in the temperature of the stream, a change is effected in
the mass or volume flow of the stream.
Description
FIELD OF THE INVENTION
[0001] The invention relates to methods and apparatus for forming
flakes or fibres of glass or of other similar materials, including
ceramic material.
[0002] The present invention is applicable to any material which
melts when heated and is capable of being formed into flakes and
fibres. Such entities are increasingly being used for the
reinforcement of plastics or other composite materials.
BACKGROUND TO THE INVENTION
[0003] In our European patent specification No 0 289 240 there is
disclosed apparatus for forming flakes of material from a heated
stream of molten material. The apparatus comprises means for
feeding the stream in a downwards direction into a rotating cup,
the cup being arranged with its open mouth facing upwardly such
that molten material within the cup is caused to flow over the
upper edges of the cup and flow outwards in a radial direction due
to centrifugal force. The apparatus also includes a pair of spaced
apart substantially parallel plates arranged about the cup such
that the material leaving the cup by centrifugal force passes
through a gap defined between the plates. The plates are mounted
within a vacuum chamber arranged such that a vacuum is applied to
the space between the plates to draw air from outside the chamber
between the plates in a radial direction to prevent the molten
material from touching the sides of the plates and to cool material
until it reaches a solid state pulling the material in a radial
direction thereby keeping the material in the form of a flat film
and breaking it into small platelets.
[0004] In the production of glass or ceramic fibre or flake the
thickness is determined in part by the temperature and volume of
the flow stream entering the spinning device producing the product.
As the flow stream is necessarily open to atmosphere between an
outlet from which the stream emerges and the spinning device, it is
subject to heat loss and variation in temperature. The loss of heat
is detrimental to the production of thin fibres or flake,
particularly in the sub-micron range and changes in temperature as
small as one degree cause variation in thickness. The viscosity of
the glass mass within a source tank or reservoir is determined by
temperature variations which in turn cause changes in mass flow
through the outlet from which the stream emerges. Additional mass
flow changes are caused by head variations within the tank.
[0005] Furthermore, in order to compensate for the heat loss
outside the source tank, the temperature within the tank may need
to be higher than the stream temperature by some hundreds of
degrees. This is not only energy wasteful but may cause severe
erosion and corrosion of the refractory lining within the tank.
STATEMENTS OF THE INVENTION
[0006] According to the present invention there is provided
apparatus for forming fibres or flakes of material comprising means
for producing a heated stream of molten material, means for feeding
the stream in a substantially vertically downward direction, means
for receiving the downwardly directed stream and for forming fibres
or flakes therefrom, and means for effecting a change in the
temperature of the stream subsequent to the production thereof
whereby fibres or flakes of a desired thickness are obtained.
[0007] The temperature changing means may be arranged to effect a
change of temperature in the stream while it is travelling in a
vertically downward direction. Alternatively, the temperature
changing means may be arranged to effect a change of temperature in
the stream prior to it travelling in a vertically downward
direction.
[0008] In accordance with the present invention the apparatus
includes means for applying a high frequency (RF) current to the
vertically downwardly travelling stream.
[0009] In another embodiment in accordance with the present
invention, means are provided for applying an electric current to
the vertically downwardly travelling stream.
[0010] In a further embodiment in accordance with the present
invention, the apparatus is alternatively or additionally by
provided with means for cooling the stream prior to it being fed in
a downward direction. The cooling means may include a conduit
through which the stream is fed, said conduit being surrounded by a
cooling coil or jacket through which an appropriate cooling fluid,
such as air, may be fed. The effect of cooling the stream within
the conduit is to solidify an outer region of the stream in the
vicinity of the outlet from the conduit. In this way, the volume
mass flow of the flow stream is reduced.
[0011] Although this variation in the volume of the flow stream is
produced by varying the temperature of at least the outer region of
the flow stream, it should be appreciated that variation of the
volume of the flow stream represents, in general, an alternative or
additional method of controlling the thickness of the resultant
flakes or fibres. Accordingly, considered in another aspect, the
present invention also provides apparatus as defined above in which
in addition to or in substitution of the temperature changing means
there are provided mass flow control means. Such control means are
typically positioned to effect the mass flow prior to the stream
being fed in a vertically downward direction.
[0012] The present invention further provides a method for forming
fibres or flakes or material comprising producing a heated stream
of molten material, feeding the stream in a substantially
vertically downward direction, receiving the downwardly directed
stream and forming fibres or flakes therefrom, and effecting a
change in the temperature of the stream subsequent to the
production thereof whereby fibres or flakes or a desired thickness
are obtained.
[0013] The present invention also provides a corresponding method
in which the mass or volume flow of the stream is controlled, prior
to the stream travelling in a vertically downward direction, in
order again to produce fibres or flakes of a desired thickness.
BRIEF DESCRIPTION OF THE DRAWING
[0014] The accompanying drawing is a schematic section through
apparatus in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The invention will now be described, by way of example only,
with reference to the accompanying drawing.
[0016] The apparatus includes a tank 1 for holding molten glass.
Extending from tank 1 is an outlet conduit or bushing 3 which
terminates in an outlet orifice 5. The stream is found in conduit 3
from material fed from tank 1 and the internal diameter of orifice
5 defines the diameter of a stream of liquid glass at the point
where it leaves conduit 3 and descends vertically from the orifice.
As indicated in the drawing the stream exiting from orifice 5
descends vertically downwards towards a spinning device 7 which may
be substantially as described in EP 0 289 240. Indeed the apparatus
includes further components for producing the flake or fibres from
the liquid stream 9, these components not being shown in the
accompanying drawing. However they may be substantially as shown
and described in EP 0 289 240.
[0017] The apparatus includes a coil 11 which surrounds the stream
9 around about half its length in a central section of the
vertically downward path. This coil is suitable for passing a high
frequency (RF) current therethrough. The coil is connected by
connections 13 and 15 to an RF heater 17 which generates the
desired current level. The passage of the high frequency current
through coil 11 causes the excitement of the molecules in the glass
stream by microwave transmission. An infrared receptor (not shown)
is located at the base of the glass stream and is connected to
suitable control circuitry for regulating the coil output and
thereby the amount of heat transmitted into the glass stream. A
large amount of heat can be instantaneously created within the flow
stream thereby allowing close temperature regulation.
[0018] Also shown in the drawing are components for another method
of directly heating the glass stream. This method involves the
passing of an electric current through the stream between an upward
connection 19 in the form of an electrode connected to bushing 5.
Such a connection can be achieved by using a bushing made of an
electrically conductive material so that the bushing is itself the
electrode or, alternatively, positioning an electrode either
immediately in front of the bushing within the tank or immediately
after it and in contact with the flow stream.
[0019] At the other end of the flow stream, electrical connection
to the spinning device 7 is made by means of a slip ring attached
to the shaft of the spinning device and including static brushes 21
through which the electrical connection is made. Control of the
current is by way of a transformer (not shown) with suitable
voltage and current output. Current variation may be achieved by,
for instance, thyristor control and an infrared receptor as
described above.
[0020] In addition or as an alternative to the above described
means for heating the glass stream, the apparatus may be provided
with means for controlling the mass flow. These means are provided
at the conduit 3 and involve cooling the glass stream emerging from
the tank 1. The conduit is provided with an oversized aperture and
is externally clad with a cooling jacket 23 through which may be
fed cooling fluid. The jacket may be a simple coil wrapped round
the bushing and fed with water or it may be an external annular
ring through which compressed air is passed. As the molten glass
passes through the bushing, the bushing is cooled and a layer of
molten material is solidified within the bushing orifice. This has
the effect of reducing the aperture size and thereby reducing the
mass flow. Although there is a loss of heat from the flow stream,
this is relatively small because the melt steam material is a poor
thermal conductor when solidified.
[0021] The change in temperature is linear with mass flow and the
flow rate can therefore be controlled by monitoring the outflow
temperature with an infrared receptor directed at the flow stream
immediately below the bushing. This receptor (not shown) is
connected to suitable electronic circuitry to vary the amount of
coolant causing solidification within the bushing. Any heat losses
arising from this control method are compensated for by the
temperature control methods described above.
[0022] This method of mass flow control also has the benefit of
allowing construction materials to be used with lower melting
points than the temperature of the material it is controlling. This
is possible because the molten material is flowing through a
solidified layer of the same material and is not in direct contact
with the bushing itself. The bushing may be at a temperature
several hundred degrees lower due to the insulating effect of the
solidified layer.
[0023] The above described methods used either individually or in
combination allow fine control of flow streams being fed into the
spinning devices such that fibres and flake may be produced with
thicknesses below 250 nanometers and with thickness variations as
low as 10 percent.
[0024] Reference has been made above to the use of apparatus of the
present invention for producing glass flakes and fibres. However it
should be appreciated that the apparatus may be used for producing
flakes or fibres of any other appropriate material including
ceramic materials.
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